Search

Sumangala, D.; Abhinav, G.; Nagamani, P.V., and Warrior, H., 2024. Enhanced upwelling dynamics simulation in the Bay of Bengal: Integrating ANNs into hydrodynamic models. Journal of Coastal Research, 40(6), 1125–1136. Charlotte (North Carolina), ISSN 0749-0208. The Bay of Bengal exhibits a unique upwelling pattern, which is most pronounced during the summer monsoon months. This phenomenon is driven by a combination of open-ocean processes and seasonally reversing winds, leading to the transport of cooler, nutrient-rich waters to the coastal areas. The upwelling process is crucial for the marine ecosystem, supporting a diverse range of organisms that thrive in colder temperatures. To accurately capture the upwelling dynamics in the Bay of Bengal, a combination of the Delft3D model and an artificial neural network (ANN) was employed. The Delft3D model alone was unable to adequately represent the upwelling phenomenon, particularly the vertical velocity component (w). The incorporation of an ANN into the Delft3D framework significantly improved the accuracy of vertical velocity predictions. This modification provided a better capacity to forecast velocities in the Bay of Bengal, with a correlation of up to 0.92 (0.97) for the u (v) velocity components. The findings of this study highlight the importance of incorporating ANNs into hydrodynamic models to accurately represent complex processes such as upwelling. This approach provides a more comprehensive understanding of these critical processes, enabling better management and conservation of marine ecosystems. [ABSTRACT FROM AUTHOR]

The coastal waters of Kerala, in the South Eastern Arabian Sea (SEAS), are unique during the Southwest monsoon season due to the concurrent occurrence of two physical processes, the upwelling and Mudbanks. However, little is known about the viral ecology and activity in a system where upwelling and Mudbanks coexist, though it is generally recognized that microbial assemblages play a vital role in the food web dynamics of marine systems, particularly in upwelling. Water samples were taken from monsoon and pre-monsoon period from three locations, (M1, M2, and M3) off Alappuzha, on the southwest coast of India to examine the viral activity and distribution. The dissolved oxygen levels showed the incursion of hypoxic waters in all the stations during the peak upwelling period. Upwelling signals were prominent in all the stations, but Mudbank and upwelling co-occurred at M2 alone during monsoon. The abundance of viruses ranged from 0.86 to 15.68 × 106 Viral-like Particles (VLPs mL−1) and prokaryotic abundance ranged from 2.73–16.26 × 105 cells mL−1. Viral and prokaryotic abundance was significantly higher in the monsoon compared to pre and late-monsoon. Based on Transmission electron microscopy (TEM) results, the non-tailed viruses constituted the major (43%) proportion of the total viruses in this study region. However, the viral production rates and viral-mediated bacterial mortality were high in the pre-monsoon compared to the monsoon and late-monsoon periods. There was no obvious effect of Mudbanks on viral dynamics and the observed variations in virological and hydrological features were governed mainly by coastal upwelling. [ABSTRACT FROM AUTHOR]

Circulation and water masses in the greater Prydz Bay region were surveyed in the austral summer 2021 (January-March) during the 'Trends in Euphausiids off Mawson, Predators and Oceanography' (TEMPO) experiment, and are described in this paper. The Southern Antarctic Circumpolar Current Front is found in the northern part of the survey area, generally near 63-64°S, whereas the Southern Boundary Front is located between 64 and 65.5°S. The westward flowing Antarctic Slope Front (ASF) is found in the southern part of the survey area near the continental slope on most transects. Highest concentrations of oxygen (> 300 µmol kg-1) are found in shelf waters at stations in Prydz Bay, south of 67°S along 75°E, whereas the lowest oxygen values are found in the Circumpolar Deep Water layer, with an average of roughly 215 µmol kg-1. North of the northern extension of the ASF, surface mixed layers are between 20 and 60m deep. Mixed layers tend to deepen slightly in the northern part of the survey, generally increasing north of 64°S where the ocean has been ice-free the longest. We find evidence of upwelling of waters into the surface layers, based on temperature anomaly, particularly strong along 80°E. Enhanced variability of biogeochemical properties - nutrients, DIC, DO - in the AASW layer is driven by a combination of sea-ice and biological processes. Antarctic Bottom Water, defined as water with neutral density > 28.3 kg m-3, was sampled at all the offshore full-depth stations, with a colder/fresher variety along western transects and a warmer/saltier variety in the east. Newly formed Antarctic Bottom Water -- the coldest, freshest, and most recently ventilated -- is mostly found in the deep ocean along 65°E, in the base of the Daly Canyon. [ABSTRACT FROM AUTHOR]

The Early Miocene witnessed major tectonic, palaeoceanographic and climatological reorganizations over the Asian realm. The Himalayan and Tibetan plateau upliftment influenced monsoon intensity during this age. Contemporary high‐resolution tropical hydroclimate records are limited. Here, we present an early Miocene sub‐annual stable isotope record from the growth bands of well‐preserved Turritella sp. from the Kachchh basin, Western India. It showed δ13C and δ18O variabilities from −4.83‰ to −1.80‰ and − 7.06‰ to −2.66‰ (in VPDB) respectively. Conventional oxygen isotope thermometry showed an apparent temperature seasonality from 9.3° to 28.1°C. A comparison of the present early Miocene δ18O record with the modern δ18O records in the carbonates from coastal‐estuarine environments of the Indian Ocean confirmed a high freshwater influx into the NE Arabian Sea during the early Miocene, similar to the modern‐day freshwater plume events observed in the coastal region. [ABSTRACT FROM AUTHOR]

Quantitative analyses of the species composition and abundance of benthic foraminifers in surface sediments along a submeridional profile in the northeastern East Siberian Sea have revealed three assemblages associated with the middle–outer shelf and upper and middle continental slope. The maximum abundance of "living" benthic foraminifers is found near the shelf break, which is possibly related to enhanced sea surface bioproductivity. Active dissolution of calcareous microfossils has been detected in the shelf area whereas preservation of calcareous tests becomes better with depth. Some micropaleontological and grain-size data indirectly point to the development of compensatory currents on the middle–outer shelf in the East Siberian Sea. [ABSTRACT FROM AUTHOR]

Polymetallic enrichment layers are commonly found at the base of the Lower Cambrian and extensively distributed across the Upper Yangtze Platform, yet their genetic models remain controversial. This study systematically collected samples from a typical section in the southeastern Chongqing region for mineral, organic, and inorganic analyses. It investigates the relationship between the abundance of various trace metal elements and organic matter at the base of the Niutitang Formation, as well as the vertical distribution characteristics of organic carbon isotopes and organic matter features. The results indicate that the Niutitang Formation shale exhibits a distinct three-part structure from bottom to top. Various metal elements are enriched in the lower interval, showing a close correlation between the abundance of polymetallic elements and the carbon isotopes of shale organic matter. The middle interval contains the highest TOC value and the lowest Ti/Al ratio, while the upper interval shows a significant decrease in organic matter abundance, with a clear positive correlation between the excess silicon content and Ti/Al ratio. Additionally, the mixing effect of deep-sea upwelling is the primary control on the formation of polymetallic enrichment layers in the lower interval, followed by the adsorption of organic matter under anoxic conditions. The sedimentary environment of the upper interval of the Niutitang Formation trends toward oxidation, with paleoclimate shifting toward colder and drier conditions, exhibiting aeolian sedimentary features that are unfavorable for the enrichment of trace metal elements. Consequently, upwelling is a key factor in the enrichment and mineralization of trace metal elements at the base of the Lower Cambrian in the Upper Yangtze region. [ABSTRACT FROM AUTHOR]

Marine fishes excrete excess H+ using basolateral Na+-K+-ATPase (NKA) and apical Na+/H+ exchanger 3 (NHE3) in gill ionocytes. However, the mechanisms that regulate H+ excretion during exposure to environmentally relevant hypercapnia (ERH) remain poorly understood. Here, we explored transcriptomic, proteomic, and cellular responses in gills of juvenile splitnose rockfish (Sebastes diploproa) exposed to 3 days of ERH conditions (pH ∼7.5, ∼1,600 μatm P co 2). Blood pH was fully regulated at ∼7.75 despite a lack of significant changes in gill 1) mRNAs coding for proteins involved in blood acid-base regulation, 2) total NKA and NHE3 protein abundance, and 3) ionocyte density. However, ERH-exposed rockfish demonstrated increased NKA and NHE3 abundance on the ionocyte plasma membrane coupled with wider apical membranes and greater extension of apical microvilli. The observed gill ionocyte remodeling is consistent with enhanced H+ excretion that maintains blood pH homeostasis during exposure to ERH and does not necessitate changes at the expression or translation levels. These mechanisms of phenotypic plasticity may allow fishes to regulate blood pH during environmentally relevant acid-base challenges and thus have important implications for both understanding how organisms respond to climate change and for selecting appropriate metrics to evaluate its impact on marine ecosystems. NEW & NOTEWORTHY: Splitnose rockfish exposed to environmentally relevant hypercapnia utilize existing proteins (rather than generate additional machinery) to maintain homeostasis. [ABSTRACT FROM AUTHOR]

Environmental conditions, physiology and community composition of phytoplankton and the carbon and nitrogen isotope signature (δ13CPOC and δ15NPN) of particulate organic matter (POM) often covary across marine environments. However, little was known on the link of δ13CPOC and δ15NPN and the community and biochemical composition of phytoplankton. In this study, particulate organic carbon (POC) and nitrogen (PN), δ13CPOC, δ15NPN, phytoplankton community composition and biomass were determined during summer, along with environmental variables, in the shelf of the northern South China Sea influenced by the Pearl River plume, upwelling and anticyclonic eddy. Our results show that variability in δ13CPOC and δ15NPN along an environmental gradient is coupled with shifts in phytoplankton community composition and carbon to chlorophyll a (C:Chl a) ratio of phytoplankton. Low δ13CPOC values (−28.4 to −27.0‰) at nearshore stations (salinity <21) were primarily due to terrestrial POM input. High δ13CPOC (>−21.0‰) and δ15NPN (>5.6‰) values are most likely attributed to high abundance of diatoms induced by riverine nutrients in the plume‐impacted waters with intermediate salinity (21< salinity <33). Low δ13CPOC (<−22.0‰) and δ15NPN (−1.1–3.7‰) values are associated with high abundance of slow‐growing cyanobacteria in the oligotrophic area (salinity >33), where the lowest δ15NPN is most likely attributed to high abundance of N2‐fixing Trichodesmium spp., due to the influence of the anticyclonic eddy. Therefore, hydrodynamics modulates the biochemical composition and community composition of phytoplankton, leading to changes in δ13CPOC and δ15NPN. Our findings advance our understanding of the coupling of physical and biogeochemical processes in marginal seas. Plain Language Summary: In marginal seas, the source and biogeochemical cycle of particulate organic matter (POM) are complicated. The mechanisms for biogeochemical dynamics of POM have been not yet well understood. Particulate organic carbon (POC) and nitrogen (PN) and their stable isotope signatures were determined, along with environmental variables, in order to examine the link of hydrodynamics and biogeochemical dynamics of POM in the shelf of the northern South China Sea that is influenced by the Pearl River plume, upwelling and anticyclonic eddy. We find that hydrodynamics plays a key role in regulating biogeochemical dynamics of POM in the study area. Hydrodynamics mediates nutrient availability and phytoplankton biomass and communities, ultimately causing spatial variability in the stable isotope of POM. δ13CPOC and δ15NPN along an environmental gradient is coupled with shifts in the community and biochemical composition of phytoplankton. Our findings have improved the understanding of interactions between physical processes and dynamics of POM in marginal seas. Key Points: Hydrodynamics‐induced shifts in phytoplankton community cause changes in δ13CPOC and δ15NPNVariability in δ13CPOC is coupled with biochemical composition of phytoplankton, independent of phytoplankton speciesNitrogen sources that phytoplankton rely on shift from NO3− in the plumed‐impacted waters to NH4+ and N2 in oligotrophic waters [ABSTRACT FROM AUTHOR]

The South China Sea is a typical marginal sea characterized by the presence of numerous seamounts. However, the effect of seamounts on the air‐sea CO2 flux has not yet been well studied. In September 2021, the air‐sea CO2 flux was measured directly using eddy covariance (EC), and discrete waterside sampling was conducted. The results indicate that the northern South China Sea is a source of atmospheric CO2. Furthermore, EC measurements show that the seamount emits CO2 at an average rate of 0.34 mmol m−2 hr−1, nearly double that of non‐seamount areas. We suggest that the upwelling around the seamount transports deep water rich in dissolved inorganic carbon to the upper ocean, increasing the partial pressure of CO2 there. In addition, the increase in nutrients caused by the upwelling would increase the concentration of chlorophyll‐a, resulting in a productive area that emits CO2. Plain Language Summary: The South China Sea (SCS) serves as a minor CO2 source, and the air‐sea CO2 flux in its northern region demonstrates challenging spatiotemporal variations. In our investigation, we conducted underway assessments in the northern SCS and validated its emission of CO2, particularly in the vicinity of seamount ocean zones. CO2 emissions may have been intensified by the upward movement of seawater surrounding the seamount region. Key Points: The northern South China Sea emitted CO2 into the atmosphere at a mean rate of 0.28 mmol m−2 hr−1 in September 2021The CO2 flux almost doubled as the seamount was approached, indicating an increase in CO2 emissions near the seamountUpwelling releases high dissolved inorganic carbon, which increases the partial pressure of CO2 on the sea surface around the seamount [ABSTRACT FROM AUTHOR]

Introduction: Offshore wind farms (OWFs) generate extensive wind wakes in their leeward areas, which can induce marine upwelling and downwelling. These processes significantly affect marine stratification and ecosystems, leaving detectable patterns on the sea surface. Materials and Methods: By utilizing MODIS data, we analyzed six representative OWFs worldwide to identify these wake signatures. Result: Notably, we observed pronounced signatures near an OWF located in the coastal waters of Jiangsu Province, China. Conversely, no coherent wake signatures were detected at other selected European and Chinese OWFs. Discussion: This absence may be attributed to inactive upwelling, weak marine stratification, unsteady wind directions, and land-sea distribution. This research offers a fresh perspective on the environmental impacts of OWFs and, for the first time, underscores the potential of global gridded satellite dataset in detecting OWF-induced wind wake signatures. [ABSTRACT FROM AUTHOR]

Current climate projections for mid-latitude regions globally indicate an intensification of wind-driven coastal upwelling due to warming conditions. The dynamics of mid-latitude coastal upwelling are marked by environmental variability across temporal scales, which affect key physiological processes in marine calcifying organisms and can impact their large-scale distribution patterns. In this context, marine invertebrates often exhibit phenotypic plasticity, enabling them to adapt to environmental change. In this study, we examined the physiological performance (i.e., metabolism, Thermal Performance Curves, and biomass and calcification rates) of individuals of the intertidal mollusk Chiton granosus, a chiton found from northern Peru to Cape Horn (5° to 55°S). Our spatial study design indicated a pattern of contrasting conditions among locations. The Talcaruca site, characterized by persistent upwelling and serving as a biogeographic break, exhibited lower pH and carbonate saturation states, along with higher pCO2, compared to the sites located to the north and south of this location (Huasco and Los Molles, respectively). In agreement with the spatial pattern in carbonate system parameters, long-term temperature records showed lower temperatures that changed faster over synoptic scales (1–15 days) at Talcaruca, in contrast to the more stable conditions at the sites outside the break. Physiological performance traits from individuals from the Talcaruca population exhibited higher values and more significant variability, along with significantly broader and greater warming tolerance than chitons from the Huasco and Los Molles populations. Moreover, marked changes in local abundance patterns over three years suggested population-level responses to the challenging environmental conditions at the biogeographic break. Thus, C. granosus from the Talcaruca upwelling zone represents a local population with wide tolerance ranges that may be capable of withstanding future upwelling intensification on the Southern Eastern Pacific coast and likely serving as a source of propagules for less adapted populations. [ABSTRACT FROM AUTHOR]

The waters of the Seram Sea and Buru Island are comparatively rich in resources and productivity. However, many fishermen continue to rely on intuition or instinct to locate fishing spots. Therefore, understanding the significance of oceanographic parameters as indicators of water's primary productivity is crucial. This study utilizes data from January 2010 to December 2020, including oceanographic parameters such as sea surface temperature (SST) and chlorophyll-a concentration from AQUA-MODIS satellite imagery, wind data from ECMWF reanalysis, and fish catch data from Fishing Spot Galala-Hative Kecil. The research aimed to examine the variability of sea surface temperature, chlorophyll-a, and surface winds, and their relationship with the upwelling phenomenon in Seram Sea waters and Buru Island. Data were processed spatially using script methods in the Grads 2.2.1 application and temporally using statistical methods in MS Excel, followed by correlation analysis using Pearson correlation. The results indicate that sea surface temperature, chlorophyll-a, and winds exhibit greater variability from May to August. Upwelling potential in these waters occurs from June to August and continues through September and October, characterized by strong upwelling. This is evidenced by low sea surface temperatures ranging from 26°C to 27.7°C, chlorophyll-a concentrations ranging from 0.5 to 1.2mg/l, and wind speeds during this period ranging from 3.9 to 6.4m/s. Additionally, correlation tests reveal that sea surface temperature and chlorophyll-a in the study area from May to August have a linear correlation with fish catch (CPUE), with values of 0.52 and 0.56, respectively. [ABSTRACT FROM AUTHOR]

Taiwan Bank (TB) is located in the southern Taiwan Strait (TS). The uplifted continental slope and bottom currents in this area result in the formation of upwelling areas, which serve as crucial fishing grounds. Climate-induced fluctuations in fish populations occur in the TS. However, how predation and competition affect the interspecies relationships in the TB ecosystem warrants clarification. In this study, we collected high-grid-resolution data on fishery activity (2013–2019) and constructed ecosystem models using Ecopath with Ecosim (EwE). Three mass-balanced models for determining the influence of El Niño–Southern Oscillation (ENSO) events on the TB ecosystem were constructed using EwE. A range of groups, including representative pelagic, benthic, and reef species, were collected for analyzing the relationship between migratory and sedentary species in terms of ecosystem structure variation due to climate change. The results demonstrated that the total system throughput (TST) was 10,556–11,122 t km−2 year−1, with an average transfer efficiency of 12.26%. According to the keystoneness index, calculated through mixed trophic impact analysis, Polydactylus sextarius and Scomber japonicus were the key species with top–down control and relatively high impact on the ecosystem in normal years. The keystone species also shifted to the predator fish Thunnus albacares and Katsuwonus pelamis during El Niño and La Niña events, respectively. Moreover, total biomass, TST, consumption, and respiration were noted to increase during ENSO events. However, during La Niña events, the diversity and connectance indexes were relatively low but pelagic species' biomass was relatively high, whereas the biomass of most benthic and reef species was relatively high during El Niño events. [ABSTRACT FROM AUTHOR]

Recruitment is a critical process in the dynamics of fish populations since it represents the abundance of new fish that enter a population each year. In Ekman‐type upwelling ecosystems, wind is a critical factor for small pelagic fish recruitment, as it controls food availability and physical constraints such as turbulence and offshore advection. In this study, we evaluate the effect of wind, chlorophyll‐a, and spawning biomass as independent variables on anchovy recruitment. Using generalized additive models (GAMs), we tested (i) the significance of each factor, (ii) the shape of the relationship between recruitment and predictors variables, (iii) recruitment regimes in the series, and (iv) whether extended windy events are associated with low recruitment levels potentially related to offshore transport of early life stages. The study period spanned from 1990 to 2021, focusing on the austral spring in south‐central Chile (35–40°S) when both upwelling and anchovy spawning are maximized. GAMs revealed a parabolic relationship between the velocity of upwelling‐favorable winds and anchovy recruitment. Maximized recruitment occurred at wind speeds around 6 m s−1 but decreased with winds above 7 m s−1 and below 5 m s−1, and during periods of extended windy events (i.e., those lasting more than 15 days). Chlorophyll‐a showed no significance on anchovy recruitment, suggesting that phytoplankton were not a limiting factor for anchovy early survival. We also found that anchovy recruitment regimes were associated with specific wind intensities. We discussed the pertinence of incorporating a recruitment index based on wind in the fishery management of the anchovy in south‐central Chile. [ABSTRACT FROM AUTHOR]

The depth culture influence (4, 8, and 16 m) and periods (upwelling and non-upwelling) on growth and survival of the pearl oyster Pinctada imbricata during 10 months in the southeastern Caribbean Sea (Cariaco Gulf) were evaluated. Monthly records were taken of survival, body growth, and fouling organisms of the pearl oyster, as well as weekly samples of the temperature, chlorophyll a, and seston of the water culture site. Monthly survival was above 92% at all depths. The variation in shell size and tissue mass of the oysters cultivated in the different depths showed a similar pattern, with slow growth during the non-upwelling period (June–October) and progressive growth during the upwelling period (November–April). The multivariate analysis showed that oyster growth was associated with the phytoplankton biomass at different depths, particularly during the upwelling period. Oysters at 4 m showed the greatest increases in all growth parameters, exceeding the minimum commercial size (50 mm) in 7 months. Hence, it is recommended that the culture of P. imbricata in the Gulf of Cariaco be started right before the upwelling season to take advantage of the high amount of food available during this period. It is also recommended that the suspended culture should not exceed 8 m for higher growth performance. [ABSTRACT FROM AUTHOR]

Abstract The Island Mass Effect (IME) around the Maldives is responsible for intense blooms with distinct seasonal patterns. These blooms sustain the fishing industry of the archipelagic nation, a vital source of income that occupies about 30% of the population. Through high resolution ocean simulations, we explore the physical processes responsible for the increased productivity and its observed variability, and their sensitivity to changes in land distribution. Year-round the frictional break of the currents in the presence of shallow bathymetry produces a strong vertical shear in the flow that favors vertical mixing, independently of the currents direction. The impact of this mixing is visible at the ocean surface during March and April, when the mixed-layer is shallow and the ocean currents are generally weak. A different mechanism than observed in spring modulates the IME during the monsoon seasons, in both winter and summer, when the zonal currents forced by the strong winds cross the archipelago: the flow accelerates while squeezing between the atolls, giving rise to intense wakes, and strong upwelling originates in the lees in response to the kilometer-scale flow divergence. This upwelling creates an asymmetric cooling signal in the lee of the islands and obfuscates the effects of the enhanced vertical mixing. The land reclamation efforts being planned on some of the islands may undercut the upwelling that drives the blooms during the monsoon seasons.

Silver is a highly toxic element for marine organisms. However, its controlling factor in marine sediments remains largely unknown, limiting our understanding of its biogeochemical cycling. Based on a sediment core from the Vietnam upwelling area in the South China Sea, it is found that Ag is significantly enriched in sediments of this area (as high as 0.39 μg/g), and it shows a very similar geochemical behavior to Ca and Sr. Our study supports the theory that Ag could be a marine paleo‐productivity indicator. Burial of Ag over the past 3,200 years shows an abrupt increase at around 1850 CE, in concordance with the global atmospheric CO2 record. It is hypothesized that elevated CO2 and global warming enhance marine productivity in the Vietnam coastal upwelling area, favoring the burial of Ag. Human‐induced global warming thus significantly impacts its biogeochemical cycling. Plain Language Summary: Cycling of elements in Earth systems is fundamental to Earth vitality. Examining biogeochemical cycling of elements is thus important in geoscience research. Global warming in recent time has exerted significant impact on the cycles of some elements, including carbon (C), nitrogen (N), and phosphorus (P). This imposes challenges to the integrity and security of Earth ecosystems. However, little is known about some other bio‐active elements. For example, silver (Ag) is highly toxic to marine organisms, but its occurrence, distribution, and fate under a warming background is largely unknown. We analyzed a marine core from the South China Sea, Western Pacific. It was found that concentrations of Ag in the sediments were pretty high, and its burial rate showed an abrupt increase at around 1850 CE. This is probably associated with increased marine productivity as Earth warmed. This study advances our understanding of the Ag cycle. Key Points: High concentrations of and significant variations in Ag were found in marine sedimentsAg in marine sediments is a marker for ocean paleoproductivityGlobal warming favors the burial of Ag in oceans [ABSTRACT FROM AUTHOR]

A comprehensive investigation was conducted to examine the variations in Chlorophyll-a (Chl-a) levels in the waters located to the south of Java Island throughout the past quarter-century. This study employs satellite data and reanalysis data gathered from multiple sources spanning the period between September 1997 and December 2022. The application of EOF analysis revealed that the most notable elevation in Chl-a contents took place during the seasons of SON (September, October, November) and DJF (December, January, February) in the years 1997/1998 and 2006/2007. It has been determined that this significant increase in Chl-a content in southern Java is contingent upon the fulfillment of a number of circumstances. These conditions are associated with climatic patterns in the Indian Ocean and Pacific Ocean. An elevation in Chl-a content was seen throughout the months of SON and DJF in instances where the Indian Ocean Dipole (IOD) had a positive phase. The concurrent occurrence of a powerful positive IOD and El Niño event in the Pacific Ocean is highly probable to result in a substantial elevation in Chl-a content in the southern region of Java. In addition, our findings indicate that the phenomenon of Kelvin wave upwelling significantly contributes to the elevation of Chl-a levels during the months of June, July, August (JJA), and SON. [ABSTRACT FROM AUTHOR]

Upwelling is due to the combined effect of the coastal divergence process and Ekman pumping. The author aims to investigate two new upwelling indices for the Black Sea, derived from climate reanalysis models and the following in situ data: (a) the Coastal Upwelling Transport Index (CUTI) that estimates the rate of vertical volume transport and (b) the Biologically Effective Upwelling Transport Index (BEUTI) that estimates the nitrate flux into the surface mixed layer. Average monthly wind by the European Centre for Medium-Range Weather Forecasts (ECMWF) and Copernicus Marine Services for the Black Sea basin is used to calculate the CUTI and BEUTI Indexes for over 26 years (1993–2019) to analyse the sites along the North-Western Black Sea where changes in divergence phenomena occur. From 2000 to 2018, 31 divergence processes were observed based on daily in situ data from the coastal monitoring stations, with significant predominance in late spring and early summer. Nitrate supply by coastal upwelling has been estimated by combining sea surface temperature and salinity for the in situ data for the North-Western Black Sea shallow waters, and BEUTI indices were determined. Comparing 18 years of data results, the calculated indices and the observed upwelling events showed significant correlations. [ABSTRACT FROM AUTHOR]

The Cenomanian deposits of the Eastern Saharan Atlas are characterised by gypsum-dominated series interpreted as coastal sabkha deposits, indicating low-latitude, and tropical to subtropical settings. The evaporitic conditions are interrupted by rapid marine ingressions allowed the deposition of carbonate beds. In the Djebel Ousigna section, fine sandy limestone bed shows abundant burrows of Macaronichnus. These traces indicate the upper shoreface–foreshore contact, affected by storm events, which show similarities with recent huge tsunami waves that facilitated the proliferation of Travisia polychaete populations (Macaronichnus tracemaker). This Macaronichnus -suite represents the most proximal marine setting during a regressive phase. Also, this unique occurrence of Macaronichnus in the North African Cenomanian low-latitude, subtropical to tropical evaporites is interpreted as related to upwelling of cold nutrient rich-waters. The latter seemingly challenge the view that this trace fossil is restricted to colder climatic zones. From an ethological viewpoint, studied Macaronichnus specimens are considered to be a sequorichnial trace (exploratory behaviour) produced by polychaete annelids. [ABSTRACT FROM AUTHOR]

Coral reef ecosystems host diversified and highly productive communities, but corals are degrading in many places worldwide. Picking suitable locations to maximize coral conservation and restoration efforts is critical. From a mass balance point of view, the supply of new nutrients is crucial to support a productive and reef-building coral ecosystem. Quantifying and qualifying available nutrients provide information to set region-specific thresholds for anthropogenic pollution monitoring and to generate research hypotheses. Here, we report the inorganic and organic nutrient levels from twenty-three sampling sites in coral reefs and coastal waters covering regions from high to low coral coverage, including two remote islands, Dongsha Atoll and Taiping Island, in the South China Sea. Some of the surveyed reefs received external inorganic nutrient supply via upwelling or submarine groundwater discharge (SGD), suggesting sites potential for new production (i.e., reef-building). Production or removal of organic matter at various sites is evidenced by their elevated or depleted organic carbon and nitrogen concentrations, respectively. The degree of impact by the upwelling and SGD on various inorganic and organic nutrient distribution varies. Among all sites, organic nitrogen accounts for most of the total nitrogen and is potentially a significant nitrogen source for the environment. The highly correlated total organic nitrogen (TON) concentrations and their C-to-N ratios (C/N-TON) suggest the production of TON with low C/N-TON and preferential removal of N during remineralization processes, leaving "leftover" TON with high C/N ratios. Furthermore, we found that high coral diversity and coverage sites are featured in low organic matter with high C/N, while macroalgae-dominating sites had elevated organic matter. The new data are valuable to generate hypotheses for future research to test, for example, whether sites with low organic matter are more suitable for restoring reef-building corals than sites with high organic matter. [ABSTRACT FROM AUTHOR]

Studies of the energy metabolism in a bivalve mollusk, the ark clam Anadara kagoshimensis (Tokunaga, 1906), were carried out for the first time under experimental conditions simulating dynamic variations in the seawater characteristics at the stages of development and end of upwelling event in the Black Sea. It was shown that the level of energy metabolism of A. kagoshimensis, while being in the zone of upwelling formation, decreased, on average, by 5% per degree of temperature decrease. During the upwelling relaxation phase (14 → 26°C), the restoration of the respiration intensity parameters of the clam was slower than expected, with a temperature coefficient of Q10 = 1.31. The acidification of the seawater by 1.0 (up to рН 7.2), combined with a temperature decrease (26 → 20°C), aggravated the negative effect by 25–45%. It has been found that the clam A. kagoshimensis reduces energy expenditure by approximately 60% under upwelling conditions (cold stress and acidification). The consequences of the negative effect of a sharp temperature variation lead to a delay in the metabolism recovery to normal values. [ABSTRACT FROM AUTHOR]

The East China Sea (ECS) is among the most important and highly dynamic shelf seas, where the coupling of physical and biogeochemical processes is distinctive and may play a crucial role in regulating nutrient conditions and the pattern of primary production. Based on field observations during the late summer of 2019, the physical controls of nutrient supply and the subsequent influences on phytoplankton chlorophyll‐a (Chl‐a) regime were investigated in the ECS. The coastal upwelling originating from the Kuroshio Subsurface Water (KSSW) intrusion serves as a nutrient source on the inner East China Sea (ECS) shelf, and this inshore upwelling combined with the coastal water largely governs the surface Chl‐a patterns. The halocline, thermocline and nutricline exhibit a vertically synchronous fluctuating phenomenon, and the coexistence of several subsurface cold rings/patches was significantly observed on the middle‐outer ECS shelf, indicating intense vertical advection and the occurrence of upwelling. The subsurface cold rings greatly regulate the vertical hydrodynamics, constituting unique upward pathways of the onshore intruded KSSW on the middle‐outer shelf. Nutrients can be upwelled within these cold rings to support primary production, thus partially leading to the spatial variability of subsurface Chl‐a maximum in terms of intensity and depth. Our findings would considerably contribute to our understanding of the physical‐biogeochemical‐ecological processes on the ECS shelf. Plain Language Summary: The East China Sea (ECS) is one of the most important continental shelves in the world. Exploring the physical‐biogeochemical processes is of great significance for the in‐depth understanding of ecosystem in this shelf sea. Here, specific attention was paid to the physical controls on the nutrient supply and the associated influences on phytoplankton chlorophyll‐a (Chl‐a) regime in the ECS. We show that the coastal/inshore upwelling originating from the nearshore branch of the Kuroshio Subsurface Water (KSSW) intrusion serves as a nutrient source on the inner ECS shelf. The co‐occurrence of several subsurface cold rings clearly indicates the upward transport of the onshore intruded KSSW on the middle‐outer ECS shelf. The subsurface cold rings may play a role in modulating the vertical hydrodynamics and related biogeochemical‐ecological processes, leading to the upward delivery of nutrients and enhanced Chl‐a levels. Our results would provide a sound scientific basis for the studies of biogeochemical and ecological dynamics in the ECS. Key Points: The coexistence of several subsurface cold rings indicating upwelling on the middle‐outer East China Sea shelf was observedSubsurface cold rings and coastal upwelling constituted unique upward pathways of the onshore intruded Kuroshio Subsurface WaterNutrients could be upwelled within the cold rings and potentially modulated the associated biogeochemical‐ecological processes [ABSTRACT FROM AUTHOR]

Despite the ubiquity of eddies at the Mid‐Atlantic Bight shelf‐break front, direct observations of frontal eddies at the shelf‐break front are historically sparse and their biological impact is mostly unknown. This study combines high resolution physical and biological snapshots of two frontal eddies with an idealized 3‐D regional model to investigate eddy formation, kinematics, upwelling patterns, and biological impacts. During May 2019, two eddies were observed in situ at the shelf‐break front. Each eddy showed evidence of nutrient and chlorophyll enhancement despite rotating in opposite directions and having different physical characteristics. Our results suggest that cyclonic eddies form as shelf waters are advected offshore and slope waters are advected shoreward, forming two filaments that spiral inward until sufficient water is entrained. Rising isohalines and upwelled slope water dye tracer within the model suggest that upwelling coincided with eddy formation and persisted for the duration of the eddy. In contrast, anticyclonic eddies form within troughs of the meandering shelf‐break front, with amplified frontal meanders creating recirculating flow. Upwelling of subsurface shelf water occurs in the form of detached cold pool waters during the formation of the anticyclonic eddies. The stability properties of each eddy type were estimated via the Burger number and suggest different ratios of baroclinic versus barotropic contributions to frontal eddy formation. Our observations and model results indicate that both eddy types may persist for more than a month and upwelling in both eddy types may have significant impacts on biological productivity of the shelf break. Plain Language Summary: The Middle Atlantic Bight shelf‐break front is a highly variable region that frequently forms frontal eddies. In situ observations of the physical and biological characteristics of these eddies are relatively scarce. We present observations of two eddies, each of which showed evidence of nutrient and chlorophyll enhancement despite having drastically different characteristics and different formation processes. Satellite data indicate that neither of the two types of eddies are rare, indicating a potential for frontal eddies to significantly influence biological communities near the front. Key Points: Two frontal eddies of opposite rotational directions were observed at the Middle Atlantic Bight shelf‐break frontNutrients, chlorophyll, diatom chains, and small copepods were enhanced in the eddiesModel simulation was consistent with upwelling within both features [ABSTRACT FROM AUTHOR]

Biotic interactions play a critical role in shaping patterns of global biodiversity. While several macroecological studies provide evidence for stronger predation in tropical regions compared with higher latitudes, results are variable even within the tropics, and the drivers of this variability are not well understood. We conducted two complementary standardized experiments on communities of sessile marine invertebrate prey and their associated predators to test for spatial and seasonal differences in predation across the tropical Atlantic and Pacific coastlines of Panama. We further tested the prediction that higher predator diversity contributes to stronger impacts of predation, using both direct observations of predators and data from extensive reef surveys. Our results revealed substantially higher predation rates and stronger effects of predators on prey in the Pacific than in the Atlantic, demonstrating striking variation within tropical regions. While regional predator diversity was high in the Atlantic, functional diversity at local scales was markedly low. Peak predation strength in the Pacific occurred during the wet, non-upwelling season when ocean temperatures were warmer and predator communities were more functionally diverse. Our results highlight the importance of regional biotic and abiotic drivers that shape interaction strength and the maintenance of tropical communities, which are experiencing rapid environmental change. [ABSTRACT FROM AUTHOR]

Turbulent mixing in the ocean exerts an important control on the rate and structure of the overturning circulation. However, the balance of processes underpinning this mixing is subject to significant uncertainties, limiting our understanding of the overturning's deep upwelling limb. Here, we investigate the hitherto primarily neglected role of tens of thousands of seamounts in sustaining deep-ocean upwelling. Dynamical theory indicates that seamounts may stir and mix deep waters by generating lee waves and topographic wake vortices. At low latitudes, stirring and mixing are predicted to be enhanced by a layered vortex regime in the wakes. Using three realistic regional simulations spanning equatorial to middle latitudes, we show that layered wake vortices and elevated mixing are widespread around seamounts. We identify scalings that relate mixing rate within seamount wakes to topographic and hydrographic parameters. We then apply such scalings to a global seamount dataset and an ocean climatology to show that seamount-generated mixing makes an important contribution to the upwelling of deep waters. Our work thus brings seamounts to the fore of the deep-ocean mixing problem and urges observational, theoretical, and modeling efforts toward incorporating the seamounts' mixing effects in conceptual and numerical ocean circulation models. [ABSTRACT FROM AUTHOR]

Upwelling, which mixes deep and surface waters, significantly enhances the productivity of surface waters and plays a critical role in marine ecosystems, especially in key fishing areas like Zhoushan. This study utilized merged sea surface temperature data and an upwelling edge detection algorithm based on temperature gradients to analyze the characteristics of upwelling in Zhoushan and the Yangtze River Estuary over the past 28 years. The results indicate that upwelling in Zhoushan begins in April, peaks in July, gradually weakens, and disappears by October. The phenomenon is most pronounced during the summer months (June to August), with significant spatial distribution differences in April and September. Notably, high probability values of upwelling centers and core areas are mainly concentrated near Ma'an Island, Zhongjieshan Island, and Taohua Island. In these areas, upwelling remains stable during the summer, forming a unique "footprint" distribution pattern, and these are also the locations of the Zhoushan National Marine Ranch. From April to August, the extent of the upwelling area gradually decreases and stabilizes. These findings emphasize the frequent upwelling activity around Zhoushan and its significant contribution to the formation of local fisheries. Additionally, considering that the formation of natural upwelling in the East China Sea depends on the southern monsoon, the study suggests establishing artificial upwelling systems during periods unfavorable for natural upwelling, based on high probability areas, to enhance fishery yields and support the development of local fisheries. [ABSTRACT FROM AUTHOR]

Suspended oysters employ physiological strategies to adjust their metabolic needs with the available food resources. Using the biodeposition method, the feeding and processing behavior of Pacific oysters (Crassostrea gigas) was investigated with a field study comparing four periods (May, July, October, and December 2016) with different upwelling intensities in the coastal lagoon of San Quintin Bay (Mexico). We calculated physiological feeding responses throughout the culture cycle, including the clearance rate (CR), filtration rate (FR), net organic ingestion rate (NOIR), net organic absorption rate (NOAR), net organic selection efficiency, net absorption efficiency, and the ammonium excretion rate (AER). The dietary quality predictors showed large fluctuations in terms of total particulate material, organic fraction of seston, and chlorophyll concentration. Unlike the pumping activity, FR, NOIR, and NOAR were related to upwelling conditions, and C. gigas removed twofold, ingested fourfold, and assimilated fivefold more of the organic suspended material during the upwelling season compared with periods of weak upwelling. C. gigas showed the potential of depositing nearly twice the organic biodeposits to the sediments during the intense upwelling events. The highest AER was recorded in July and October, suggesting that seasonal temperature variation is the most important exogenous factor regulating nitrogen metabolism, even in a subtropical environment. Also, mechanistic models incorporating dietary quality predictors to the feeding and processing response functions of C. gigas were performed. We conclude that coastal upwelling plays an important bottom-up control on oysters' feeding and processing activity, and our results facilitate further studies of the carrying capacity of embayments influenced by eastern boundary current systems. [ABSTRACT FROM AUTHOR]

The Arabian Sea (AS) hosts the world's thickest and most intense oxygen minimum zone (OMZ), and previous studies have documented a dramatic decline of dissolved oxygen (DO) in the northeastern AS in recent decades. In this study, using the recently released data from Biogeochemical‐Argo floats, we found a surprising trend of recovery in deoxygenation within the core region of the OMZ in the AS (ASOMZ) since 2013. The average DO concentration increased by approximately threefold, from ∼0.63 μM in 2013 to ∼1.68 μM in 2022, and the thickness of the ASOMZ decreased by 13%. We find that the weakening of Oman upwelling resulting from the weakening of the summer monsoon is the main driver of oxygenation in the ASOMZ. In addition, the reduction of primary production linked to warming‐driven stratification reinforces deoxygenation recovery at depth. Plain Language Summary: The deoxygenation of the ocean is one of the most important changes occurring in the marine environment, impacting marine biodiversity, primary production, and carbon and nitrogen biogeochemical cycles. Ocean deoxygenation can cause the expansion of naturally occurring low dissolved oxygen (DO) water bodies known as OMZs. As the world's thickest and most intense oxygen minimum zone (OMZ), the Arabian Sea (AS) has undergone a dramatic decrease in DO, particularly in the northeastern AS in recent decades. Based on an unprecedented collection of DO from biogechemical‐Argo floats over the past decade, we found a surprising trend of recovery in deoxygenation within the core region of the OMZ in the AS (ASOMZ) since 2013. The average DO concentration in the ASOMZ increased by almost thrice, and the thickness decreased by 13%. Weakening of the summer monsoon over the AS and strengthening of stratification induced by global warming are possible causes for the recovery from deoxygenation. OMZs have major impacts on global carbon and nitrogen cycles. Our findings not only overturn the previous view of the deoxygenation trend in the ASOMZ but also provide valuable insights for projection model studies of global OMZs. Key Points: Deoxygenation in the oxygen minimum zone in the Arabian Sea has been recovered during the past decadeThe decrease in Oman upwelling due to the weakening of the summer monsoon is likely the main mechanism for the increase in dissolved oxygenThe strengthening of stratification in the AS leading to a decrease in production also contributed to the recovery of deoxygenation [ABSTRACT FROM AUTHOR]

A general decline in foundation species at the rocky intertidal has been observed during the last decades all around the world and primarily related to climate change. In agreement with that trend, the mussel aquaculture sector in Galicia (NW Spain), the main production area in Europe, has warned over the last years about a decline in the availability of wild mussel seed from the rocky coast. Here we compile for the first time, mussel seed collection reports by mussel farmers in Galicia for the period 2006–2021. We employed that dataset as a proxy of mussel recruitment evolution in the rocky shore for the last 16 years. Temporal analysis of our data confirmed the reported decline (-148 t yr-1), particularly pronounced from 2012 onwards. The data base also allowed us to analyze inter-annual variability according to both, climatic variations and management scenarios. Since cultivated mussels conform a meta-population with wild mussels from the rocky shore, alterations on the market preferences towards smaller individuals at harvest, could also contribute to a reduction in reproductive output. Our results show a decrease in life-time egg production under certain scenarios. Nonetheless, coastal upwelling seems to be the largest factor conditioning recruitment abundance, explaining as much as 60% of the variability observed. Decline on recruitment abundance was highly modulated by the observed increment in frequency of intense upwelling events, exceeding 500 m3 km-1 s-1 between July and November. Meridional winds also determined the spatial recruitment patterns, pointing to the large role of wind forcing on mussel larval dispersal. Our results highlights how alterations on upwelling regimes related to climate change can interact with mussel population dynamics and also condition aquaculture sustainability and food security. [ABSTRACT FROM AUTHOR]

Using satellite observation and reanalysis data, we studied the cold water phenomenon in the sea area of the Xisha Islands in autumn from 2003 to 2022. The cold water phenomenon refers to a colder water body relative to its surrounding area, which can partially offset the impact of global warming, thereby contributing to the protection and restoration of marine ecosystems. The cold water with a central position close to the Xisha Islands is distributed in a nearly circular area, and exhibits seasonal and interannual variations. It usually occurs at the end of September, with its intensity rapidly increasing and reaching its peak on October 1, then gradually weakening, and finally disappearing by November 6. The maximum intensity of the cold water phenomenon can reach 1.6°C. This phenomenon notably observed in October 2006, 2009, 2013 and 2022, with intensities reaching 0.9°C, 1.1°C, 1.1°C, and 0.4°C, respectively. The dynamic mechanism of its formation can be described as follows: in autumn of some years, the northeast monsoon occurs in the northern part of the South China Sea (SCS), while the southwest monsoon still prevails in the southern part of the SCS, which causes the generation of strong positive wind stress curl (WSC) near the Xisha sea area. The positive WSC causes cyclonic circulation and further causes upwelling through Ekman pumping, which transports low‐temperature water from the seabed to the sea surface and thus leads to the occurrence of the cold water phenomenon in the Xisha sea area. Plain Language Summary: The Xisha sea area has numerous coral reefs and marine ranching sites, which form an important part of the marine ecosystem. Under global climate warming, extreme high temperature events frequently lead to coral reef bleaching and marine ranching degradation. The cold water phenomenon can partially offset the impact of climate warming and reduce the frequency and intensity of marine ecological disasters. We found that there are substantial cold water phenomena in the Xisha sea area during autumn in some years, and the formation mechanism can be attributed to upwelling caused by the East Asian monsoon through an ocean suction process. The cold water phenomenon has seasonal and interannual variations and can cause phytoplankton blooms. The discovery of the cold water phenomenon has important scientific significance for the protection and restoration of coral reefs and marine ranching in the Xisha sea area. Key Points: The cold water phenomenon in the Xisha sea area was reported for the first timeThe cold water in the Xisha sea area exhibited seasonal and interannual variationsThe formation of the cold water can be attributed to upwelling caused by wind stress curl through Ekman pumping in the Xisha sea area [ABSTRACT FROM AUTHOR]

The ocean, a pivotal component of the Earth’s climate system, exerts a profound global influence through intricate physical and biological interactions within its surface layer. This interplay centers around the mixed layer (ML), integral for energy exchange driven by oceanic currents. An essential regulatory function of the ocean involves orchestrating the distribution of chemical elements, with nitrate assuming a pivotal role in oceanic primary production. Nutrient availability, a cornerstone of primary production, hinges on the mixed layer depth (MLD) dynamics, modulated by many mechanisms, including upwelling and convection. This study unravels the interplay between nutrient variability and MLD depth, focusing on the Gulf of Guinea (GG) region in the equatorial Atlantic. Characterization of the study area reveals distinctive sea surface temperature (SST), salinity (SSS), and current patterns. The South Equatorial Undercurrent (SEUC) and Equatorial Undercurrent (EUC) play vital roles in surface nutrient transport. Nitrate distribution unveils latitudinal variations, exhibiting pronounced enrichment during boreal summer and winter. The equatorial region experiences a strengthening of MLDs from 10.5 to 35.33 m in summer, which increases the nitrate input from 0 to 2.06 mmol m-3 in the surface layers in the mixed layer. In contrast, boreal winters experience more intense MLDs that vary between 20.5 and 64.50 m, supporting high nitrate concentrations of 2.96 to 7.49 mmol m-3, challenging previous hypotheses. This equatorial enrichment is supported by low nitracline ranging from 5.47 to 46.19 m. Beyond the equator, the subequatorial and subtropical regions, despite the observed deepening of the ML, present low nitrate concentrations (less than 0.5 mmol m-3) with a nitracline that does not reach the ML. However, at 6°S and 9°S, a respective increase in nitrate content of 0.66 mmol m-3 and 1.2 mmol m-3 influenced by internal waves, advection and surface currents is observed. Temperature, salinity, and atmospheric fluxes shape nutrient distribution and primary production dynamics. These findings illuminate the intricate relationships between oceanographic processes, nutrient availability, and marine ecosystem productivity. A holistic understanding is crucial for sustainable resource management and fisheries in the equatorial Atlantic and beyond.

Locally enhanced biological production and increased carbon export are persistent features at oceanic density fronts. Studies often assume biological properties are uniform along fronts or hypothesize that along- and across-front gradients reflect physical-biological processes occurring in the front. However, the residence times of waters in fronts are often shorter than biological response times. Thus, an alternate—often untested—hypothesis is that observed biological patchiness originates upstream of a front. To test these two hypotheses, we explore an eddy-associated front in the California Current System sampled during two surveys, separated by 3 weeks. Patches of high phytoplankton biomass were found at the northern ends of both surveys, and phytoplankton biomass decreased along the front. While these patches occurred in similar locations, it was unclear whether the same patch was sampled twice, or whether the two patches were different. Using an advection-reaction framework combined with field and satellite data, we found that variations in along-front gradients in dissolved oxygen, particle biovolume, and salinity support the conclusion that the two phytoplankton patches were different. They were only coincidentally sampled in similar locations. Backward- and forward-in-time tracking of water parcels showed that these phytoplankton patches had distinct origins, associated with specific, strong coastal upwelling pulses upstream of the front. Phytoplankton grew in these recently upwelled waters as they advected into and along the frontal system. By considering both local and upstream physical-biological forcings, this approach enables better characterizations of critical physical and biogeochemical processes that occur at fronts across spatial and temporal scales.

Abstract Oceanic eddies exhibit remarkable coherence and longevity compared to other transient features in the surrounding flow. They possess the ability to transport properties over extensive distances while maintaining their material identity intact. The Lagrangian Coherent Structure (LCS) framework has proven effective in capturing these coherent eddies, where they display a solid-body-like rotation. Although various LCS approaches have been employed to investigate different facets of coherent eddies, a comprehensive understanding of their three-dimensional structures and internal dynamics remains elusive. This study aims to advance our comprehension of coherent eddies’ structural characteristics and delve into the precise nature of their internal dynamics by utilizing the Lagrangian Averaged Vorticity Deviation approach. Two eddies, one cyclonic and the other anti-cyclonic, were chosen from a high-resolution simulation carried out in the Bay of Bengal using the Regional Ocean Modeling System (ROMS). The findings unveil that these eddies have three-dimensional coherent cores resembling gently tapered cones that are broader at the surface and gradually narrow towards the bottom. Intriguingly, the dynamically coherent core of these eddies exhibits simultaneous upwelling and downwelling while maintaining their volumes during advection due to persistent material coherence. The three-dimensional trajectories followed by the fluid parcels inside the coherent core are helical. Their two-dimensional horizontal projections show alternating spiral bands of upwelling and downwelling which are the manifestations of Vortex Rossby Waves. These observations lead to a conceptual framework of a three-dimensional helico-spiralling recirculation pattern within the coherent cores of eddies.

Coastal upwelling along the SE Baltic Sea coast is a common feature, especially during the warm season. It significantly lowers sea surface temperature (SST) in the coastal areas, and, therefore, may be responsible for modifying meteorological conditions in those coastal areas, where upwelling is most frequently observed. This study aims to assess the effect of coastal upwelling on the air temperature at the south-eastern coast of the Baltic Sea based on long-term period observations (2002–2021) from coastal hydrometeorological stations and satellite data. Overall, our study revealed that due to its high frequency and spatial extent, upwelling is responsible for lowering the mean summer season SST of the SE Baltic Sea coast by about 1°C. And even though upwelling is a short-term event, upwelling-induced SST drop results in cooling air temperatures in the coastal areas, i.e., the mean air temperatures during upwelling are typically 2−4°C lower than before. It was also observed that upwelling is favouring the development of advective fog. Thus, sudden changes in meteorological parameters during upwelling can have versatile effects on various socio-economic activities. The results of this study contribute to the understanding of upwelling feedback onto the lower atmosphere and, therefore, are important for advancing the accuracy of weather forecasts that are needed for coastal communities, including marine and coastal industries.

The article presents the results of the Tutleim formation complex studies of core from 16 wells drilled on an area of 900 km2 near the Kamennaya crest of the Krasnoleninsky arch. The area is characterized by the variability of the structural plan, preserved from the time of deposits sedimentation, that might affect the structure of formation. Regionally traceable lithological units were used to describe different types of sections, which were firmly recorded on the core and on the logs. The article presents the results of the sections correlation, that shows the variability of the Tutleim formation through the area, identifies typical sections for the submerged, slope and crestal parts of the investigated field. The section may contain two reservoir intervals of different types: radiolarite and siliceousphosphate layers with average porosity values of 7% and 15%, respectively. The radiolarite layers form the main potential-productive intervals, that are found in all types of sections on one or two stratigraphic levels: in the crestal sections only in the third unit, in the slope and submerged sections – in the first, second and third units. The phosphorite layer in the fifth unit is a characteristic singularity only of the crestal sections. The obtained results allow predicting the distribution of the potential-productive intervals of the Tutleim formation and its stratigraphic analogues in different areas with higher accuracy.

Given the importance of coastal upwelling systems to ocean productivity, fisheries, and biogeochemical cycles, their response to climate change is of great interest. However, there is no consensus on future productivity changes in these systems, which may be controlled by multiple drivers including wind‐driven and geostrophic transport, stratification, and source water properties. Here we use an ensemble of regional ocean projections and recently developed upwelling indices for the California Current System to disentangle these sometimes‐competing influences. Some changes are consistent among models (e.g., decreased mixed layer depth), while for others there is a lack of agreement even on the direction of future change (e.g., nitrate concentration in upwelled waters). Despite models' diverging projections of productivity changes, they agree that those changes are predominantly driven by subsurface nitrate concentrations, not by upwelling strength. Our results highlight the need for more attention to processes governing subsurface nutrient changes, not just upwelling strength. Plain Language Summary: The California Current System is one of the world's eastern boundary upwelling systems—some of the most productive regions in the global ocean. These regions support a wide range of human activities, such as fisheries and tourism, motivating extensive research on how they might evolve under future climate change. A number of hypotheses have been offered to describe future physical and chemical change in these systems, and in terms of their impacts on primary production (which forms the base of the marine food web), these mechanisms may reinforce or oppose each other. Enhanced nutrient concentrations in upwelling source waters would support higher productivity, increased stratification would limit nutrient supply and productivity, and increased upwelling could enhance productivity to a point but limit productivity if it is too strong. There is no consensus on which mechanism(s) will predominantly drive future productivity changes. Here we provide a detailed analysis of projected physical and biogeochemical changes and how they relate to productivity changes. Even though different models project different futures, we find that in all of them the primary control on productivity is the nitrate concentration of subsurface waters, not the strength of upwelling, which has received more attention to date. Key Points: Future changes in the California Current System are evaluated using an ensemble of downscaled ocean projectionsWe evaluate changes in Ekman and geostrophic transports, water column structure, and subsurface nitrate concentrationsAcross models, phytoplankton biomass changes are more closely tied to subsurface nitrate concentration than upwelling strength [ABSTRACT FROM AUTHOR]

Oceanic eddies exhibit remarkable coherence and longevity compared to other transient features in the surrounding flow. They possess the ability to transport properties over extensive distances while maintaining their material identity intact. The Lagrangian Coherent Structure (LCS) framework has proven effective in capturing these coherent eddies, where they display a solid-body-like rotation. Although various LCS approaches have been employed to investigate different facets of coherent eddies, a comprehensive understanding of their three-dimensional structures and internal dynamics remains elusive. This study aims to advance our comprehension of coherent eddies' structural characteristics and delve into the precise nature of their internal dynamics by utilizing the Lagrangian Averaged Vorticity Deviation approach. Two eddies, one cyclonic and the other anti-cyclonic, were chosen from a high-resolution simulation carried out in the Bay of Bengal using the Regional Ocean Modeling System (ROMS). The findings unveil that these eddies have three-dimensional coherent cores resembling gently tapered cones that are broader at the surface and gradually narrow towards the bottom. Intriguingly, the dynamically coherent core of these eddies exhibits simultaneous upwelling and downwelling while maintaining their volumes during advection due to persistent material coherence. The three-dimensional trajectories followed by the fluid parcels inside the coherent core are helical. Their two-dimensional horizontal projections show alternating spiral bands of upwelling and downwelling which are the manifestations of Vortex Rossby Waves. These observations lead to a conceptual framework of a three-dimensional helico-spiralling recirculation pattern within the coherent cores of eddies. [ABSTRACT FROM AUTHOR]

Increasing nutrient inputs driven by global environmental pressures may lead to changes in prokaryotic plankton biomass and community composition in coastal environments. Nutrient addition experiments (inorganic, organic, and mixed) were performed at the continental shelf outside the Ría de Vigo, in spring, summer and autumn 2014, and the results contrasted with those from similar previous experiments carried out inside the ría in 2013. The mixed nutrient additions caused the greatest changes in community composition, mostly consisting of blooms of Vibrionales. Inorganic nutrients yielded increased proportions of Oceanospirillales and Alteromonadales. Euclidean distances among samples were used to estimate compositional resistance to disturbances derived from nutrient additions. Changes in prokaryotic biomass were used as an indicator of biomass resistance. Generally, prokaryotic communities were more resistant to inorganic than organic nutrient additions. Communities sampled inside the ría, presumably exposed to greater perturbations, showed milder variability in the non-amended control than those from outside the ría. By contrast, shelf communities, with higher ambient organic matter concentrations, were more resistant to organic and mixed nutrient additions than those from the ría. Our data suggest that the perturbation history is related to the resistance of microbial communities to changes in nutrient inputs into the coastal ocean. [ABSTRACT FROM AUTHOR]

As ocean temperatures increase, so does the need for accurate, regular, and widespread temperature data. This is especially important for researchers studying corals, which can be pushed over their bleaching thresholds by small, sustained changes in water temperature. Satellite data products offer longitudinal estimates of sea surface temperature (SST) taken at regular intervals without the ongoing costs and geospatial limits associated with underwater temperature loggers. However, previous work indicates satellite data are sometimes characterized by significant temperature biases, particularly in stratified coastal waters. Here, we compared the foundation sea surface temperature (fSST) estimated from a highly processed, gridded satellite data set (GHRSST MUR L4 Global SST) to in situ temperature (IST) data collected from coral reef habitats in the top 20 m of the water column at 19 sites in Panama. Comparisons between Pacific and Caribbean coasts and between upwelling and non-upwelling seasons provide a robust test of the utility of this product to estimate subsurface temperatures. The mean differences between fSST and IST show that MUR fSST accurately reflects temperatures at shallow (<9 m) depths on the Caribbean coast (mean bias ≤0.55°C ± standard error (SE) 0.01°C) and during the non-upwelling season on the Pacific coast (mean bias ≤0.26°C ± SE 0.03°C). MUR fSST poorly reflects IST during the Pacific upwelling season, especially at sites 12 m and deeper. In such cases, 66% of satellite estimates deviated from ISTs by >1°C. Our findings underscore how highly processed SST data products should be ground-truthed before being used as a substitute for IST, especially in upwelling areas. [ABSTRACT FROM AUTHOR]

İzmit Bay, a 50 km long inlet at the eastern end of the Marmara Sea, is crucial for the region's economy, culture, and marine ecosystem. The bay's water circulation regulates nutrient distribution, stratification, sedimentation, oxygen levels, heat, and pollution levels. It is also influenced by meteorological events, such as short-term moderate to strong wind conditions. This study investigated the sensitivity of İzmit Bay Water Circulation to wind speed, direction, and duration using the MITgcm model with Orlanski boundary conditions and process-oriented modeling. The simulations showed that under weak forcing conditions, seawater temperature, salinity, and stratification do not significantly vary. However, strong forcing and wind speeds (statistically defined by percentiles of observation data) of 4.9 m/s (75%), 6.7 m/s (90%), and 10.1 m/s (99%) generate significant mesoscale and sub-mesoscale processes, depending on the direction. Westerly component winds cause downwelling at the eastern coastline, while easterly component winds bring sub-surface water to the surface. Strong winds from N, NE, and E sectors lead to the rise in lower-layer waters in the western basin, forcing them to overflow through the Hersek Delta sill into the central basin. Overall, severe wind events greater than 4.9 m/s (75%) significantly affect the bay's hydrography by transforming the upper layer, with a decrease in temperature up to 5 °C and an increase in salinity up to 10 ppt. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Earth Science (1001-8166) is the property of Advances in Earth Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the California Current System (CCS), changes in the phenology (i.e., seasonal timing) of coastal upwelling alter the functioning of this productive marine ecosystem. Recently developed coastal upwelling indices that account for upwelling strength and nutrient flux to the surface provide a more complete understanding of bottom‐up forcing in the region. Using these indices, we describe CCS upwelling phenological variability in vertical transport and nutrient flux. Physical and biogeochemical spring transitions generally co‐occur in winter or spring, followed by increased upwelling and nutrient flux. In the latter half of the year, upwelling continues but nutrient flux wanes as declining source nutrient concentrations limit the biological efficacy of coastal upwelling. Earlier spring transitions and higher season‐integrated upwelling intensity occur during strong La Niña events at all latitudes, driven largely by stronger alongshore wind stress. Understanding phenological changes in coastal upwelling is critical, as they could have significant ecosystem consequences. Plain Language Summary: In the California Current System (CCS), coastal upwelling carries nutrient‐rich waters to the surface, supporting primary production and driving the coastal ecosystem. This upwelling varies on a seasonal and interannual basis, as reflected in recently developed indices that account for the amount of water upwelled to the surface as well as the amount of nutrients carried in that water. Generally upwelling and nutrient transport are high in the first half of the year. Upwelling persists into the second half of the year, but nutrient transport decreases as the deep‐water sources of these nutrients are depleted. Upwelling in the CCS is also affected by the El Niño Southern Oscillation. During La Niña conditions, strong trade winds enhance upwelling and nutrient transport on the California coast. This paper presents regional, seasonal and interannual patterns of upwelling and nutrient delivery in the CCS, which are important drivers of change to this coastal ecosystem. Key Points: We define new upwelling phenology indices for the California Current System that include nutrient transportWe identify spatial, seasonal, and interannual patterns of upwelling and nutrient deliveryWe relate the physical mechanisms of coastal upwelling with its biological efficacy [ABSTRACT FROM AUTHOR]

Changing temperature and ocean acidification are well-recognised consequences of climate change in marine systems. In contrast to global trends, the South African west coast is experiencing cooling due to increased frequency and intensity of upwelling. The implications of concurrent cooling and acidification for marine biota are poorly understood, particularly at the community level. This laboratory study assessed how cooling and acidification might affect fouling communities along the South African west coast. Communities were experimentally exposed to two temperatures, 13℃ (current) and 9℃ (cooling), and three pH treatments, 7.9 (current), 7.6 and 7.4, for 18 days. Cooling and acidification altered community structure. Species diversity declined in response to acidification but was not affected by cooling. This was driven by greatest loss of species at 7.4 pH. Notably, acidification reduced the abundance of both calcifying and soft-bodied taxa, highlighting the vulnerability of taxa like ascidians to acidification. Overall, these results highlight the dominant threat posed by acidification, even for alien taxa that are often perceived as resilient to climate change. Additionally, in regions experiencing cooling, acidification may pose a greater threat to fouling communities than thermal changes. [ABSTRACT FROM AUTHOR]