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Oxygen consumption by oceanic microbes can predict respiration (CO2 production) but requires an assumed respiratory quotient (RQ; ΔO2/ΔCO2). Measured apparent RQs (ARQs) can be impacted by various processes, including nitrification and changes in dissolved organic matter (DOM) composition, leading to discrepancies between ARQ and actual RQ. In DOM remineralization experiments conducted in the eastern North Atlantic Ocean, ARQs averaged 1.39 ± 0.14, similar to predictions for complete consumption of plankton biomass. DOM removed with an elevated nominal oxidation state (i.e., more oxidized DOM), as detected by liquid chromatography-tandem mass spectrometry, coincided with increased hydrolyzable amino acid removal, increased ARQs and bacterioplankton respiration (BR), and a decreased bacterioplankton growth efficiency (BGE). Across experiments, evidence emerged that nitrification and DOM partial oxidation, driven in part by bacterioplankton members of OM43, SAR92 and Rhodobacteraceae, can elevate BR relative to bacterioplankton consumption of plankton-derived carbon. These rare synoptic measurements of interrelated variables reveal complex biochemical and cellular processes underlying variability in large-scale CO2 production estimates.

Climate-induced droughts exert a significant influence on the connectivity of river systems. It is estimated that about 25% of the world's rivers ran dry before reaching the ocean due to climate change and human activities. Ecological water replenishment is an effective measure for restoring aquatic ecosystems damaged by drought. It is urgently needed to quantitatively assess the aquatic ecosystems in rewetted dry river channels after water replenishment. This study investigated the variations in phytoplankton, zooplankton, benthic macroinvertebrates, and benthic bacterial communities in the rewetted dry river channel of Yongding River after water replenishment. In comparison with the water column communities, the benthic macroinvertebrates were identified as limiting factors for ecological restoration in rewetted dry river channels. In the absence of a certain recovery time for benthic macroinvertebrates, the benthic bacterial-based index of biological integrity, especially calculated based on their intrinsic properties, can properly assess aquatic ecosystems in rewetted dry river channels. [ABSTRACT FROM AUTHOR]

Explaining biodiversity is the central focus in theoretical ecology. A significant obstacle arises from the competitive exclusion principle (CEP), which states that two species competing for the same type of resources cannot coexist at constant population densities, or more generally, the number of consumer species cannot exceed that of resource species at steady states. The conflict between CEP and biodiversity is exemplified by the paradox of the plankton, where a few types of limiting resources support a plethora of plankton species. In this review, we introduce mechanisms proposed over the years for promoting biodiversity in ecosystems, with a special focus on those that alleviate the constraints imposed by the CEP, including mechanisms that challenge the CEP in well‐mixed systems at a steady state or those that circumvent its limitations through contextual differences. [ABSTRACT FROM AUTHOR]

The short-term variability of plankton communities in the oceanic realm is still poorly known due to the paucity of high-resolution time-series in the open ocean. Among these few studies, there is compelling evidence of a lunar cycle of epipelagic zooplankton biomass in subtropical waters during the late winter bloom. However, there is few information about lower trophic levels and zooplankton physiological changes related to this lunar cycle. Here, we studied the short-term variability of pico-, nano-, micro-, and mesoplankton in relation to the lunar cycle in subtropical waters. Weekly sampling was carried out at four stations located north of the Canary Islands from November 2010 to June 2011. Zooplankton abundance and biomass, gut fluorescence (GF), electron transfer system (ETS), and aminoacyl-tRNA synthetase (AARS) activities were measured before, during, and after the winter vertical mixing in these waters in a wide range of size classes. Chlorophyll a , primary production, and zooplankton biomass were low, showing a rather weak late winter bloom event due to the high temperature and stratification observed. Chlorophyll, nanoplankton, diatoms, and mesozooplankton proxies for grazing (GF), respiration (ETS), and growth (AARS) varied monthly denoting a lunar pattern. Chlorophyll a, nanoplankton, diatoms, and mesozooplankton proxies for grazing and respiration peaked between 4 and 6 days after the new moon, followed by an enhancement of the mesozooplankton index of growth between 8 to 9 days after the new moon. However, mesozooplankton biomass only increased during the productive period when supposedly growth exceeded mortality. Coupled with previous results in pico-, nano-, and microplankton, we suggest that the lunar cycle governs the development of planktonic communities in the high turnover warm subtropical ocean. This study provides further evidence of the match of plankton communities with the predatory cycle exerted by diel vertical migrants, adding essential information to understand the short-term functioning of the open ocean. [ABSTRACT FROM AUTHOR]

Taxa specific responses to climate warming may shape aquatic communities, dominance patterns, biotic interactions, and related ecosystem processes and functions. As climate warming effects on smaller zooplankton are less understood than larger zooplankton, we focused on rotifers to study their response to a future climate warming scenario in outdoor mesocosms. Our year-long experiment (14 July 2020 to 13 July 2021) included present temperature conditions as controls and a treatment simulating a future warmer climate involving occasional heatwaves. Total rotifer abundance increased with warming, with Keratella spp. and Polyarthra spp. benefiting the most, while the Kellicottia spp. population collapsed. Filinia spp. were negatively affected by warming in the summer of 2020, but increased during winter and the following summer. Our findings suggest that thermophilic or eurytherm rotifers such as Keratella and Polyarthra may increase in a warmer future, while heat-sensitive Kellicottia may be negatively affected in the temperate region. Milder winters may allow some rotifer genera to proliferate while allowing others to recover from high summer temperatures, thereby considerably changing the composition and dominance patterns of rotifer assemblages. [ABSTRACT FROM AUTHOR]

The interaction between aquatic organisms and plants is crucial to maintaining the ecological balance of the marine environment. This study aims to investigate the effects of providing refuge on phytoplankton and the delay in releasing hazardous substances by phytoplankton. To accomplish this, a nutrient-phytoplankton-zooplankton system was developed and analyzed to examine its equilibria and the conditions under which they exist. The model’s stability was also analyzed, both in the absence and presence of time delays. The inclusion of a time delay caused a Hopf bifurcation at the interior equilibrium of the model, resulting in a transition from stability to instability. The study found that as the time delay value increases, the system’s stable dynamics transition into an unstable state. However, because phytoplankton refuge is part of the system, the dynamics temporarily become stable, even though phytoplankton release the toxins over a long time. However, this stable behavior is disrupted when the time required for the toxin liberation process by phytoplankton is further extended. [ABSTRACT FROM AUTHOR]

Mobulid rays (manta and devil rays) use a highly specialized filtering apparatus to separate plankton food particles from seawater. Recent studies have indicated that captive vortices form within the microscale pores of the filter, which enhance filtration efficiency through a novel mechanism referred to as ricochet separation. The high throughput and clog resistance of this filtration process have led to the development of several bioinspired engineered filtration systems. However, it is still unclear how changes to the filter morphology influence the surrounding flow patterns and filtration efficiency. We address this question by examining the flow fields around and filtering properties of mobulid filters with systematically varied morphologies, using a combination of computational fluid dynamics and experiments on physical models. While the pore size is the principal determinant of filtration efficiency in a sieve filter, we found that the captive vortices in a mobulid filter grow or shrink to fill the pore, and changes in the pore size have modest effects. By contrast, the filtration efficiency appears to be highly sensitive to the orientation of the filter lobes (microscale plate-like structures). These results provide a foundation for interpreting the morphological differences between species and also for generating optimized bioinspired designs. [ABSTRACT FROM AUTHOR]

Within aquatic ecosystems, heterotrophic, mixotrophic and autotrophic plankton are entangled in a complex network of competitive, predatory and mutualistic interactions. "Browning," the increase of colored dissolved organic matter (CDOM) from terrestrial catchments, can affect this network of interactions by simultaneously decreasing light availability and increasing organic carbon and nutrients supplies. Here, we introduce a conceptual, process-based numerical model to investigate the effects of browning on a microbial food web consisting of heterotrophic bacterioplankton, bacterivorous phago-mixoplankton, autotrophic phytoplankton and the resources light, inorganic phosphorus and DOM. Additionally, we explore how the investment in autotrophic vs. phagotrophic resource acquisition influences mixoplankton performance. Several model predictions are in broad agreement with empirical observations under increasing CDOM supply, including increased bacterial biomass and inorganic phosphorous, decreased light penetration, the potential for a unimodal phytoplankton biomass response and a local minimum in mixoplankton biomass. Our results also suggest that mixoplankton with a high investment in phototrophy perform best in many conditions but that phosphorous acquisition via prey is crucial under high light-low nutrient conditions. Overall, our model analyses suggest that responses to altered CDOM supply are largely determined by systematic changes in the relative importance of nutrient vs. energy limitation of each plankton group. [ABSTRACT FROM AUTHOR]

Strombidium rassoulzadegani is an oligotrich ciliate from coastal waters that retains functional chloroplasts from its algal diet. Using a Fluorescence Induction and Relaxation fluorometer, we measured the maximum quantum efficiency (QE) of Photosystem II in two algal foods, one chlorophyte and one cryptophyte, and in the chloroplasts retained by the ciliate. Within the ciliate, QE of the chloroplasts was about half the value (c. 0.3) of that in exponentially-growing, nutrient-replete algal cultures (0.5–0.6). Under starvation, when the ciliates were not able to replace aging chloroplasts, QE declined further, to values of 0.1–0.2. The rate of decline was similar at irradiances from 30–100 μmol m−2 s−1 and slightly faster in total darkness. Exposure of the ciliates to the Photosystem II inhibitor DCMU decreased growth rates much more strongly in chlorophyte-fed ciliates, compared to those fed the cryptophyte. The decline in the chlorophyte-fed ciliates was much greater than expected, given the small subsidy to growth provided by the retained chloroplasts, suggesting that their role in the ciliate's metabolism may be more than just a photosynthetic boost. [ABSTRACT FROM AUTHOR]

To explore how environmental factors affect the structure of plankton in urban rivers, we analyzed the Caowangjing River, an urban river that passes through Wuxi, to survey the water environmental factors and plankton population in different seasons. We identified 103 phytoplankton species belonging to eight phyla, with Chlorophyta, Bacillariophyta, and Cyanobacteria being the dominant groups. A total of 45 zooplankton species belonged to three classes, with Rotifera being the dominant class. Phytoplankton density was highest in the autumn, followed by the spring, and the lowest in the summer. Phytoplankton biomass, along with zooplankton density and biomass, exhibited seasonal declines. The average values of the Shannon–Wiener index, Pielou's evenness index, and Margalef richness index were 3.58 ± 0.50, 0.72 ± 0.76, and 2.03 ± 0.31, respectively, indicating the Caowangjing River was mildly polluted based on a water quality evaluation. Redundancy analysis showed that turbidity, water temperature, and ammonia nitrogen are the key factors of phytoplankton community distribution, while water temperature, the permanganate index, and ammonia nitrogen are the key factors of zooplankton community distribution. [ABSTRACT FROM AUTHOR]

This paper considers the features of a time series of plankton concentrations, which are further compared with such phenomena as the alteration of day and night and tidal processes. The analysis of experimental data recorded as a result of long-term monitoring measurements under field conditions showed that the diurnal variability in plankton concentrations can be described using a model harmonic function. At the same time, based on the parameters of the diurnal variability model, it is possible to build a bioindication system to detect the influence of abnormal environmental factors estimated as pollution. This study discusses the ideology of building such a system based on regular observations of the behavior of autochthonous plankton using a submersible digital holographic camera. [ABSTRACT FROM AUTHOR]

A key control on the magnitude of coastal eutrophication is the degree to which currents quickly transport nitrogen derived from human sources away from the coast to the open ocean before eutrophication develops. In the Southern California Bight (SCB), an upwelling-dominated eastern boundary current ecosystem, anthropogenic nitrogen inputs increase algal productivity and cause subsurface acidification and oxygen (O 2 ) loss along the coast. However, the extent of anthropogenic influence on eutrophication beyond the coastal band, and the physical transport mechanisms and biogeochemical processes responsible for these effects are still poorly understood. Here, we use a submesoscale-resolving numerical model to document the detailed biogeochemical mass balance of nitrogen, carbon and oxygen, their physical transport, and effects on offshore habitats. Despite management of terrestrial nutrients that has occurred in the region over the last 20 years, coastal eutrophication continues to persist. The input of anthropogenic nutrients promote an increase in productivity, remineralization and respiration offshore, with recurrent O 2 loss and pH decline in a region located 30-90 km from the mainland. During 2013 to 2017, the spatially averaged 5-year loss rate across the Bight was 1.3 mmol m -3 O 2 , with some locations losing on average up to 14.2 mmol m -3 O 2 . The magnitude of loss is greater than model uncertainty assessed from data-model comparisons and from quantification of intrinsic variability. This phenomenon persists for 4 to 6 months of the year over an area of 278,40 km 2 ( ∼ 30% of SCB area). These recurrent features of acidification and oxygen loss are associated with cross-shore transport of nutrients by eddies and plankton biomass and their accumulation and retention within persistent eddies offshore within the SCB.

Abstract The plankton community structure and environmental factors in Dongting Lake were investigated during four seasons from September 2020 to August 2021. The results revealed 147 species from 58 genera and 7 phyla of phytoplankton and 84 species from 56 genera and 4 phyla of zooplankton in Dongting Lake. The characteristics of plankton communities varied with time and space. The temporal variation of phytoplankton abundance ranged from 43.5201 × 104 to 120.7968 × 104 cells/L and the spatial variation ranged from 18.6707 × 104 to 247.5542 × 104 cells/L. The temporal variation of zooplankton abundance ranged from 18 to 42 ind/L and the spatial variation ranged from 19 to 62 ind/L. The temporal and spatial variations of the abundance range values were much larger for phytoplankton than for zooplankton, with phytoplankton dominating. However, environmental factors in Dongting Lake vary more temporally than spatially, and drive more temporal than spatial variations in planktonic organisms. Based on the redundancy analysis WT, DO, and CODMn were the main environmental factors affecting the distribution of phytoplankton, while WT, CODMn, NO2–N, and Chl-a were the main factors affecting the distribution of zooplankton. WT and CODMn were the common key influencing factors.

Abstract Background An increase in upper-ocean thermal stratification is being observed worldwide due to global warming. However, how ocean stratification affects the vertical profile of plankton communities remains unclear. Understanding this is crucial for assessing the broader implications of ocean stratification. Pelagic ciliates cover multiple functional groups, and thus can serve as a model for studying the vertical distribution and functional strategies of plankton in stratified oceans. We hypothesize that pelagic ciliate communities exhibit vertical stratification caused by shifts in functional strategies, from free-living groups in the photic zone to parasitic groups in deeper waters. Results 306 samples from the surface to the abyssopelagic zone were collected from 31 stations in the western Pacific and analyzed with environmental DNA (the V4 region of 18 S rDNA) metabarcoding of pelagic ciliates. We found a distinct vertical stratification of the entire ciliate communities, with a boundary at a depth of 200 m. Significant distance-decay patterns were found in the photic layers of 5 m to the deep chlorophyll maximum and in the 2,000 m, 3000 m and bottom layers, while no significant pattern occurred in the mesopelagic layers of 200 m – 1,000 m. Below 200 m, parasitic Oligohymenophorea and Colpodea became more prevalent. A linear model showed that parasitic taxa were the main groups causing community variation along the water column. With increasing depth below 200 m, the ASV and sequence proportions of parasitic taxa increased. Statistical analyses indicated that water temperature shaped the photic communities, while parasitic taxa had a significant influence on the aphotic communities below 200 m. Conclusions This study provides new insights into oceanic vertical distribution, connectivity and stratification from a biological perspective. The observed shift of functional strategies from free-living to parasitic groups at a 200 m transition layer improves our understanding of ocean ecosystems in the context of global warming. Graphical Abstract

Abstract Several experimental evidences and field data documented that zooplankton may alter its behavioral response in the presence of toxic phytoplankton, reducing its consumption to the point of starvation. This paper is devoted to the mathematical study of such interactions of toxic phytoplankton with grazer zooplankton. The non-toxic phytoplankton is assumed to adopt a density-dependent refuge strategy to avoid over-predation by zooplankton. Both groups of phytoplankton are assumed to suffer direct harm from anthropogenic toxicants, while zooplankton is affected indirectly by ingesting contaminated phytoplankton. We calibrate the proposed model with the field data from Talsari and Digha Mohana, India, and estimate some crucial model parameters consistent with the behavior of the observed data. Our results demonstrate that zooplankton grazing on toxic phytoplankton plays a key role in the emergence or mitigation of plankton blooms. We also highlight the system’s potential to exhibit multiple stable configurations under the same ecological conditions. The plankton system experiences significant regime shifts, which are explored through various bifurcation scenarios, such as transcritical and saddle-node bifurcations. These shifts are influenced by changes in refuge capacity, species growth rates, and environmental carrying capacity. Furthermore, we incorporate environmental variations due to seasonal periodic or almost periodic changes, allowing the refuge parameter to be time-dependent. We observe that the forced system exhibits double periodic solutions. Moreover, stronger seasonal variations in the refuge pattern lead to irregular chaotic blooms. In conclusion, the results offer valuable insights into the sustainability of biodiversity, potentially shedding light on the origin of diverse plankton bloom phenomena.

ABSTRACT In this study, we examine a deterministic model incorporating refuge, additional food sources, and toxins. The existence and stability of positive equilibria and the bifurcation analyses are discussed. Our numerical outcomes entail that increased zooplankton growth due to additional food leads to the disappearance of phytoplankton species, while a significant drop in nutrient levels results in zooplankton extinction within the ecosystem. Notably, the refuge by phytoplankton has a tendency to terminate the persistent oscillations and stabilize the system. As seasonal stochasticity significantly influences the dynamics of planktonic system, so we introduce seasonality into environmental noise and certain model parameters. In this case, we analyze both the regularity and the dichotomy between persistence and extinction. The numerical evidences demonstrate periodic solutions, strong/weak persistence, and plankton extinctions resulting from stochasticity and/or seasonality. Furthermore, the seasonally forced noise, intriguingly, has the capacity to exert control over hyperchaos, yielding a distinctive pattern in plankton populations. [ABSTRACT FROM AUTHOR]

A new species of the freshwater copepod genus Arctodiaptomus is described from a high-altitude lake of Kumaun Himalaya. The undescribed species differs from their congeners by the presence of a strong comb-shape denticulated spine at the antepenultimate segment of male right antennule. Basis of the male fifth right leg possess a butterfly shape hyaline membrane on the inner lateral side; 2-segmented endopod with board distinct proximal segment. Endopodite of the female fifth leg is elongated round apex without any septum. The identified diaptomid tends to be restricted in the Himalayan region; it seems apparently isolated from the purported main area of the origin. [ABSTRACT FROM AUTHOR]

The circumstances under which species diversify to genetically distinct lineages is a fundamental question in biology. Atlantic herring (Clupea harengus) is an extremely abundant zooplanktivorous species that is subdivided into multiple ecotypes that differ regarding spawning time and genetic adaption to local environmental conditions such as temperature, salinity, and light conditions. Here we show using whole genome analysis that multiple populations of piscivorous (fish-eating) herring have evolved sympatrically after the colonization of the brackish Baltic Sea within the last 8000 years postglaciation. The piscivorous ecotype grows faster, and is much larger and less abundant than the zooplanktivorous Baltic herring. Lesions of the gill rakers in the piscivorous ecotype indicated incomplete adaptation to a fish diet. This niche expansion of herring in the young Baltic Sea, with its paucity of piscivorous species, suggests that empty niche space is more important than geographic isolation for the evolution of biodiversity. The Atlantic herring is one of the world's most abundant vertebrates and a typical plankton feeder of major ecological importance. This study shows that a piscivorous (fish-eating) ecotype of herring has evolved after the colonization of the brackish Baltic Sea within the last 8,000 years. [ABSTRACT FROM AUTHOR]

Ocean alkalinity enhancement (OAE) is a nature-based technology for CO2 removal and storage, but little is known about its environmental safety. We tested a CO2-equilibrated OAE deployment in a close-to-natural community using in situ mesocosms in the oligotrophic subtropical North Atlantic and assessed metazoan zooplankton to inform about food web stability, structure, and production. In addition, a literature review complemented experimental results by summarizing physiological responses of marine animals to decreasing proton concentrations, or increased pH. The food web studied proved resistant, and zooplankton physiologically tolerant, to the OAE tested. We observed short-term effects of OAE on zooplankton reproduction and productivity, which were likely trophically mediated. Yet, these did not affect zooplankton populations or their nutritional value as food for fish. Our study demonstrates an environmentally safe OAE application, but also stresses the risks of more intense OAE options, and the vulnerabilities of other marine ecosystems. [ABSTRACT FROM AUTHOR]

We present the first comprehensive phylogenetic study of the global fauna of the superfamily Oplophoroidea (including all 70 valid species), based on nine molecular markers and 111 morphological characters (including six multistate characters). In this study, we developed a novel approach for assessing and visualizing single- and multigene relative genetic distances (RGD) between species, complementing traditional phylogenetic trees and providing additional support for taxonomic conclusions. While both morphological and molecular phylogenetic trees of Oplophoroidea were largely congruent, the molecular trees were better resolved at most nodes. Based on molecular trees and RGD plots, we confirmed the existence of three families and proposed three new genera within the former Systellaspis, diagnosed them, and provided a key for identifying all genera and species of Oplophoroidea. We were unable to definitively confirm or reject the monophyly of Acanthephyra and Meningodora and, therefore, retained their current status pending further multigene analyses. We also observed a low level of external morphological diversity within Oplophoroidea, likely due to the relatively homogeneous habitats and similar ecological pressures they experience. Additionally, we identified two groups of co-evolving characters, discussed evolutionary trends, and examined behavioral adaptations that contribute to the evolutionary success of these species in the pelagic environment. ZooBank: urn:lsid:zoobank.org:pub:BA47FCEF-FE40-4177-B99D-0C2A168698A4. [ABSTRACT FROM AUTHOR]

In order to understand the current status of plankton and fish population structure and diversity after the construction of the 'One Dam and Three Routes' project in the Dazhangxi River, plankton and fish samples were collected in the Dazhangxi River watershed in June and October 2023.A total of 149 species of phytoplankton from 7 phyla were found. The biomass of phytoplankton ranged from 0.88 to 21.35 mg/L, the Shannon ∼ Wiener diversity index (H') ranged from 2.04 to 3.99, the Margalef abundance index (D) ranged from 1.56 to 3.72, and the Pielou homogeneity index (J') ranged from 0.41 to 3.72. The permanganate index (CODMn) and pH were the most important environmental factors affecting the distribution of phytoplankton, and the variation of Margalef's richness index (D) ranged from 1.56 to 3.72, and Pielou's uniformity index (J') ranged from 0.41 to 0.76. Seventy species of zooplankton were found in the survey, the biomass of zooplankton ranged from 0.0042 to 3.20 mg/L, the Shannon ∼ Wiener diversity index (H') ranged from 0.1972 to 3.22, the Margalef abundance index (D) ranged from 1.50 to 5.17, the Pielou index (J') ranged from 0.41 to 0.76, and CODMn and pH were important environmental factors affecting the distribution of phytoplankton. The variation range of Pielou's evenness index (J') was 0.066 ∼ 0.824. ammonia nitrogen∼, Secchi depth, and electrical conductivity were important environmental factors affecting the distribution of zooplankton. A total of 38 species of fish were collected in the survey, belonging to 7 orders, 13 families, and 33 genera, with the predominance of Carpiformes accounting for 50%, Perchiformes accounting for 23.68%, the diversity index of the fish ranged from 1.703 to 2.386, the richness index from 1.763 to 3.882, the predominance index from 0.754 to 0.888, and the uniformity index from 1.504 to 2.144, and the diversity index from 1.504 to 2.14. The fish community was obviously miniaturized, but some rare and uncommon fish were found. The diversity index of zooplankton in the Dazhangxi River fluctuated greatly, and the fish resources showed a declining trend and obvious miniaturization. [ABSTRACT FROM AUTHOR]

Plankton, as an important part of the food chain in the river ecosystem, is sensitive to changes in the environment. To investigate the influence of plankton community structure on the aquatic ecosystem and further verify the applicability of biomanipulation, the midstream of the Jialing River was selected as the study area. A total of 149 species (varieties) from 7 phyla, 18 orders, 34 families, and 72 genera were identified for phytoplankton. A total of 48 species were found for zooplankton. The mean density of phytoplankton was 2.09 × 106 cells/L, and the mean density of zooplankton was 27.1 ind./L. Moreover, the mean values of the Shannon–Wiener diversity index (H′), Pielou homogeneity index (J′), and Margalef abundance index (D) for phytoplankton were 3.17, 0.76, and 4.47, respectively. The mean values of the Shannon–Wiener diversity index (H′), Pielou homogeneity index (J′), and Margalef abundance index (D) for zooplankton were 2.64, 0.92, and 5.07, respectively. Based on the diversity indices, the water quality was evaluated as oligo pollution to β-medium pollution level. Redundancy analysis (RDA) was used to explore the relationship between dominant plankton species and environmental factors. The RDA results show that the main environmental factors affecting the community structure of phytoplankton and zooplankton were water temperature (WT), electrical conductivity (EC), pH, total phosphorus (TP), and transparency (Secchi depth; SD). There were 17 functional groups in phytoplankton, which are X1, S1, Y, Y2, and so on. In zooplankton, there were six functional groups, which are Pmsl, Prsu, Pfif, Pmip, Lrsf and Lmic. Many articles have demonstrated the feasibility of using biological manipulation to control algae. The number of piscivorous fish in the midstream of the Jialing River had increased, and phytoplankton density in this survey was significantly decreased. The results show that traditional biomanipulation can be applied to this region, which can provide better scientific support for the future management of the aquatic environment in the Jialing River basin. [ABSTRACT FROM AUTHOR]

The mixing of reactive tracers within the ocean mixed layer, phytoplankton transported downwards from the sea surface and nutrients transported upwards from the mixed layer depth (MLD), is investigated using large eddy simulation coupled to a Lagrangian plankton model. The study focuses on how vertical and horizontal heterogeneity in tracer distribution is generated and how it influences an autumn phytoplankton bloom. The vertical gradient appears in the profiles of horizontal mean phytoplankton and nutrient concentrations, P and N, and it reduces phytoplankton production by photosynthesis compared to the cases with uniform distributions. The reduction ratio decreases as the mixed‐layer mean N increases, but it remains relatively insensitive to other conditions such as MLD, surface forcing, stratification below the mixed layer, and the initial N. Phytoplankton and nutrient concentrations show a negative correlation in the horizontal plane, which becomes stronger with increasing depth. Its contribution to plankton production by photosynthesis is negligible, however, because the correlation is weak near the sea surface and the reaction time scale is much longer than the turbulent mixing time scale. It is also found that the vertical gradients of P and N are smaller, and the negative correlation is stronger in the convective mixed layer than in the shear‐driven mixed layer. A simple box plankton model, which takes into account the mixing process of tracers, is proposed and used to investigate how mixing affects the prediction of an autumn phytoplankton bloom. Plain Language Summary: An autumn phytoplankton bloom occurs in the mid to high‐latitude ocean, when the deepening of the surface mixed layer brings nutrients from below the mixed layer to near the sea surface, where photosynthesis by phytoplankton takes place. Therefore, the mixing of two tracers within the mixed layer, downward‐transported phytoplankton and upward‐transported nutrients, plays an important role in triggering the autumn phytoplankton bloom. To clarify the mixing process, simulations were carried out using a new type of plankton model, in which a large number of plankton particles move around in turbulent flows of the ocean. The existence of vertical gradients in phytoplankton and nutrient concentrations within the mixed layer is found to reduce the phytoplankton production by photosynthesis, compared to the cases with vertically uniform distributions. Phytoplankton and nutrient concentrations show a negative correlation in the horizontal plane, although their effect on phytoplankton production is negligible. It is also found that the mixing of the two tracers differs depending on whether the mixed layer is driven by surface cooling or wind stress. A simple box plankton model, which takes into account the mixing process of tracers, is proposed. Key Points: Mixing of top‐down and bottom‐up diffusing tracers in the mixed layer is investigated using large eddy simulations coupled to a Lagrangian plankton modelThe effect of heterogeneity in phytoplankton and nutrient concentration distributions on phytoplankton production is investigatedA simple box plankton model is proposed to predict an autumn phytoplankton bloom by considering the mixing process of tracers [ABSTRACT FROM AUTHOR]

Microzooplankton grazing is widely recognized as an important process of heterotrophic prokaryote and phytoplankton biomass removal. However, few studies have specifically addressed microbial mortality in the Ria Formosa coastal lagoon. This study aimed to assess the growth and mortality of heterotrophic prokaryotes and phytoplankton in this ecosystem using the dilution technique. The results revealed significant seasonal variations in the growth and grazing rates of both heterotrophic prokaryotes and phytoplankton, with mean grazing rates slightly exceeding the mean potential instantaneous growth rates. This indicates that microzooplankton consume a substantial proportion of both microbial groups in the lagoon. For specific phytoplankton taxa, the wide range of observed grazing rates suggests grazer selectivity, highlighting the need for future research to examine the dynamics of each phytoplankton group more closely. [ABSTRACT FROM AUTHOR]

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The Indonesian government continues to accelerate the resolution of all problems related to the planning, infrastructure development, and arrangement of tourist visits, including the arrangement of parking spaces and commercial areas in the Borobudur temple area. The purpose of this study is to develop a waste management system in the parking and commercial areas of Kujon as an alternative to structuring the Borobudur temple area. The research method is a descriptive-qualitative observational approach. Surface water and groundwater examinations are carried out in laboratories and compared with quality criteria determined by the Indonesian government. Toxic and hazardous waste is stored in temporary facilities until it is collected by a company licensed by the Indonesian environmental ministry. The Shannon-Wiener Plankton and Benthos Diversity Index measures the diversity of organisms in a community. The study's findings highlight the need to establish a waste processing facility based on the reduction, reuse, and recycling principles. Waste will be collected at a certain site and stored temporarily in line with the technical instructions for the Minister of Environment and Forestry's Regulation. The findings of surface water and groundwater studies demonstrate that all measured parameters continue to meet the Indonesian government's quality thresholds. Plankton Bioindicator Measurements: Plankton diversity index values range from 1.040 to 1.943, indicating moderate pollution, while benthos values range from 0.811 to 0.918, indicating weakly to moderately contaminated conditions. Sustainable environmental management is critical and should serve as a baseline for environmental quality in the activity area. [ABSTRACT FROM AUTHOR]