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The Bermuda Testbed Mooring (BTM) and Bay of Bengal Ocean Acidification (BOBOA) mooring measurements were used to identify changes in the partial pressure of CO2 at the sea surface (pCO2sea) and air-sea CO2 fluxes (FCO2) associated with passage of two tropical cyclones (TCs), Florence and Hudhud. TC Florence passed about 165 km off the BTM mooring site with strong wind speeds of 24.8 m s-1 and translation speed of 7.23 m s-1. TC Hudhud passed about 178 km off the BOBOA mooring site with wind speeds of 14.0 m s-1 and translation speed of 2.58 m s-1. The present study examined the effect of temperature, salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), air-sea CO2 flux, and phytoplankton chlorophyll a change on pCO2sea as a response to TCs. Enhanced mixed layer depths were observed due to TCs-induced vertical mixing at both mooring sites. Decreased pCO2sea (-15.16±5.60 μatm) at the BTM mooring site and enhanced pCO2sea (14.81±7.03 μatm) at the BOBOA mooring site were observed after the passage of Florence and Hudhud, respectively. Both DIC and TA are strongly correlated with salinity in the upper layer of the isothermal layer depth (ILD). Strong (weak) vertical gradient in salinity is accompanied by strong (weak) vertical gradients in DIC and TA. Strong vertical salinity gradient in the upper layer of the ILD (0.031 psu m-1), that supply much salinity, dissolved inorganic carbon and total alkalinity from the thermocline was the cause of the increased pCO2sea in the BOBOA mooring water. Weak vertical salinity gradient in the upper layer of the ILD (0.003 psu m-1) was responsible for decreasing pCO2sea in the BTM mooring water. The results of this study showed that the vertical salinity gradient in the upper layer of the ILD is a good indicator of the pCO2sea variation after the passages of TCs., Competing Interests: The authors have declared that no competing interests exist

A time series of satellite data on Chlorophyll-a concentration (Chl-a) that used ocean color was studied to determine mechanisms of phytoplankton variation in recent decade in the Yellow Sea, China during 2003-2015. The variability patterns on seasonal and inter-annual oscillation periods were confirmed using the Empirical Orthogonal Function (EOF), and Morlet wavelet transform analyses, respectively. The first EOF mode for Chl-a was dominated by obvious spring and fall blooms in a spatial pattern that was related to the strong mixing of the water masses from the Yellow Sea Cold Warm Mass (YSCWM) and the Yellow Sea Warm Current (YSWC) in winter. The second EOF mode for Chl-a showed an opposite spatial pattern between the northern and southern regions. The temporal coefficient showed differences in the timing of blooms. On an inter-annual scale, Chl-a indicated variation at periods of 2-4 years during 2003-2015. Chl-a showed a significantly negative correlation with the sea surface temperature (r = -0.21, p<0.01), with time lags of 4 months (Chl-a ahead). Chl-a was coupled with El Niño Southern Oscillation (ENSO) events, with a positive correlation (r = 0.46, p<0.01) at a lag of 3-5 months (ENSO ahead). The present study demonstrated that the variation in phytoplankton biomass was controlled primarily by water mass seasonally, and it was influenced by ENSO events on an inter-annual scale., Competing Interests: The authors have declared that no competing interests exist.

Oil spills in oceans have substantial influence on marine ecosystems. This study investigates 21 oil spills in the world. Analyzing Chlorophyll-a (Chl-a) from Moderate Resolution Imaging Spectroradiomerer (MODIS) data after Penglai oil spills on 4 June 2011, found a bloom with peak value of Chl-a (13.66 mg m−3) spread over an area of 800 km2 during 18–25 June 2011, and a pronounced increase in the monthly Chl-a concentration (6.40 mg m−3) on June 2012 in the Bohai Sea. Out of the 21 oil spills, 14 blooms were observed, while 11 blooms associated with oil spills in the time interval of 3–10 months. In total, about 75% blooms occurred during June–August. Among all 14 blooms, 72% appeared when temperature was warm (20–30 °C), 7% appeared when temperature was low (10–20 °C), and the remaining 21% occurred when temperature was lower than 10 °C. This research concludes that the odds of a phytoplankton bloom after an oil spillage are higher at the time of higher temperature (>20 °C). The short-term impact of the oil spills on ecosystem could mainly depend on the quantity and composition of oil, while the long-term impact of the oil spills on ecosystem could be related to biodegradation of microorganisms. [ABSTRACT FROM AUTHOR]

A northeastward jet in the western South China Sea (SCS) usually induces phytoplankton blooms during summertime. This jet is often sandwiched by a cyclonic eddy in the north and an anticyclonic eddy in the south. Using in situ and satellite data, the present study analyzes the combined impact of the northeastward jet and two eddies on the phytoplankton size structure (PSS) from August to September 2014. Generally, picophytoplankton is the major size fraction in surface water, contributing 73% of the total chlorophyll a concentration. The data showed that a high chlorophyll a belt (av. 0.29 ± 0.18 μg L −1 ) with a large percentage of microphytoplankton (av. 14%) appeared in the northeastward jet. Meanwhile, similar chlorophyll a concentrations were observed in the cyclonic (av. 0.072 ± 0.019 μg L −1 ) and anticyclonic eddies (av. 0.087 ± 0.02 μg L −1 ), but microphytoplankton contributed 6.7% more in the anticyclonic eddy. Below the surface, however, the dominant size of phytoplankton switched from pico to nano and micro with increasing depth. In contrast to the observations at the surface, the jet and anticyclonic eddy presented a lower microphytoplankton contribution than the cyclonic eddy. Horizontally, advection of coastal upwelling water by the northeastward jet enhanced the growth of phytoplankton and influenced the surface PSS. Meanwhile, divergence/convergence in cyclonic/anticyclonic eddy interaction with the northeastward jet formed the high chlorophyll a belt at the edge of the eddy and increased the microphytoplankton contribution through water mass transport and mixing. Nutrient supply and weakening of the light intensity below the surface layer synergistically influenced the concentration and size structure of phytoplankton in the cyclonic/anticyclonic eddies at different depths. Finally, this study proposed a ‘jet-eddy system’ to explain summer spatial characteristics of PSS in the western SCS. Source water (riverine and coastal upwelling water) that feeds the ‘jet-eddy system’ is another key factor affecting phytoplankton biomass and its size structure. [ABSTRACT FROM AUTHOR]

Temporal variations of chlorophyll a (Chl a) concentration before and after the Montara oil spill in August 2009 in the Timor Sea were analysed using MODIS-derived Chl a data. Time series data suggested a decrease in Chl a concentration following the oil spill, but an increase occurring in May 2010. A 4000 km2 patchy phytoplankton bloom with a high concentration of 13.8 mg m−3 occurred southeast of the platform, which coincided with the location the residual oil spill finally moved to. The Chl a was usually high in that area in May, but reached a peak in May 2010: the monthly Chl a for May 2010 was one and a half times higher than that of the average value for May between 2003 and 2009. The present study also analysed as many as 15 cases of major marine oil spills in the world and discussed their impacts on phytoplankton. The results suggested that the increase of Chl a may have relations with the oil spill incident. Natural seasonal variability is also an important factor for the formation of the phytoplankton bloom. [ABSTRACT FROM PUBLISHER]

Abstract: Phytoplankton blooms appear in winter (Nov–Jan) in the southwest of Luzon Strait, South China Sea, which is an oligotrophic region in general. To understand dynamic features of the winter phytoplankton bloom southwest of Luzon Strait, this study analyzes seven years (2000–2006) of remote sensing data of Chlorophyll a, sea surface temperature, and ocean vector winds, along with in situ observations of dissolved oxygen, nutrients (nitrate, phosphate, and silicate), and physical oceanographic parameters mixed layer depth, Ekman pumping velocity, and entrainment velocity. The results demonstrate that the winter phytoplankton bloom in the southwest of Luzon Strait is primarily induced by both Ekman pumping-driven upwelling (observed at about 50m under sea surface) and upper mixed layer entrainment. The area of winter phytoplankton blooms is about 2.58×104 km2, based on Empirical Orthogonal Function analysis. The seasonal variability of the bloom is associated with monsoonal wind forcing. [ABSTRACT FROM AUTHOR]

The Gulf of Tonkin is a semi-closed gulf northwest of the South China Sea, experiencing reversal seasonal monsoon. Previous studies of water conditions have been conducted in the western waters of the gulf, but very few studies of the Chlorophyll-a (Chl-a) distribution have been carried out for the entire gulf. The present study investigates seasonal and spatial distributions of Chl-a and water conditions in the Gulf of Tonkin by analyzing Sea-viewing Wide Field-of-View Scanner (SeaWiFS) derived Chlorophyll-a (Chl-a), in situ measurements, sea surface temperatures (SST), and other oceanographic data obtained in 1999 and 2000. The results show seasonality of Chl-a and SST variations in the Gulf of Tonkin, and reveal phytoplankton blooming events in the center part of the gulf during the northeast monsoon season. In summer, Chl-a concentrations were relatively low (<0.3 mg m-3) and distributed uniformly throughout most of the area, with a belt of higher Chl-a concentrations along the coast, particularly the coast of Qiongzhou Peninsula; in winter, Chl-a concentration increased (0.5 mg m-3) in the entire gulf, and phytoplankton blooms offshore-ward from the northeast coast to the center of the gulf, while Chl-a concentrations reached high levels (0.8–1 mg m-3) in the center of the blooms. One peak of Chl-a concentrations was observed during the northeast monsoon season in the year. SST were high (27–29 °C) and distributed uniformly in summer, but lower with a large gradient from northeast (17 °C) to southwest (25 °C) in winter, while strong northeast winds (8–10 m/s) were parallel to the east coast of the gulf. Comparison of Chl-a values shows that SeaWiFS derived Chl-a concentrations match well with in situ measurements in most parts of the gulf in May 1999, but SeaWiFS derived Chl-a are higher than in situ data in river mouth waters. The seasonal variation of Chl-a concentrations and SST distribution were associated with the seasonally reversing monsoon; the winter phytoplankton blooms were related to vertical mixing and upwelling nutrients drawn by the northeast wind. [Copyright &y& Elsevier]

The northern Arabian Sea is a semienclosed sea with high primary productivity and a complicated flow pattern consisting of several eddies. This paper reports on phytoplankton blooms, which were associated with a cold eddy in the northern Arabian Sea during November 1996, inferred from Ocean Color and Temperature Scanner (OCTS) and Sea-view Wide Field-of-view Sensor (SeaWiFS)-derived chlorophyll a (Chl-a hereafter), AVHRR sea surface temperature (SST), and other available oceanography data. The blooms emerged at 100 km from both coasts in the Gulf of Oman (60.5°E, 24.5°N) where the depth is about 3000 m. The Chl-a concentrations patch first appeared on November 2 and decayed after about 4 weeks (December 3, 1996). The high Chl-a concentrations patch was about 100 km in diameter and it was located at 60.3–61.3°E, 23.5–24.5°N. The bloom, having a mean Chl-a concentration of 6.8 mg m−3 on November 6, was located in a cold SST eddy, which was accompanied by another feature, an anticyclone eddy (of 100 km in diameter) with high SST and low Chl-a concentrations to the southwest (61.5°E, 22.5°N). An SST drop occurred around November 14, which coincides with a peak of the vertical pumping velocity derived from NSCAT-derived wind stress. Two SeaWiFS-derived Chl-a images obtained in November 1998 and 1999 show good agreement in terms of the locations and features with those described above through the OCTS observations. The possible mechanism for this newly identified Chl-a patch is discussed. [Copyright &y& Elsevier]

Fishery resources along China’s coasts have been declining. Could those decline be alleviated by deploying artificial reefs (ARs) in suitable areas? This study investigates effects of a big project conducted in December 2007 that deployed ARs in the southwestern part of Daya Bay. The ARs cover a total dimension of 966.10 × 2850.60 m 2 and surface area of 91,500 m 2 . This study analyzed the spatial and temporal variations of ecological factors, including Chlorophyll a concentrations (Chl-a), nutrients, attaching organisms and nekton resources, on and around the ARs using both satellite (Moderate Resolution Imaging Spectroradiometer, MODIS) and in situ data. Results showed that the potential affected area of ARs in Daya Bay reached a distance of 4.9 km in the water depth of 12.0–15.2 m. In the study area, Chl-a level reached 2.93 mg m −2 during the post-AR period (2008–2012), that was higher than the pre-AR period (2002–2007) (2.37 mg m −2 ). Nekton biomass increased by 4.66–16.22 times compared with that in the pre-AR survey, and the species diversity increased by 15%–23%. This parallel trend suggested that ARs might have contribution to the increase in nekton biomass. Long-term observations shall be conducted to understand the response of phytoplankton to ARs. [ABSTRACT FROM AUTHOR]