Effluent waste generated from the intensive production of vannamei shrimp is known to play an essential role in increasing phytoplankton abundance and the alteration of environmental quality. This alteration is characterized by the presence of various organic compounds and their derivatives. The northern coastal area of Bangka Island represents a region in Indonesia that has witnessed significant growth and development as a vannamei shrimp cultivation zone. Therefore, this study aims to evaluate phytoplankton abundance and environmental quality in the waste of shrimp ponds in the northern coastal area of Bangka Island. The investigation procedures were carried out in four specific locations within this area, namely BL1, BL2, BL3, and BL4. The results showed the presence of five–six distinct phytoplankton groups, including a total of 11–18 genera, within the effluent discharge from these ponds. The highest abundance of phytoplankton was recorded at BL3, with a value of 2,418,375 cells ml−1. The phytoplankton groups identified at all locations included Chlorophyta, Cyanophyta, Chryptophyta, Bacillariophyta, and Pyrrophyta. Euglenophyta was found at BL1 and BL3 but was not observed at BL2 and BL4. Furthermore, the most abundant group found in this study was Chlorophyta. The genera Nanochloropsis, Chlorella, Microcystis, and Nitzschia were consistently found in all the surveyed ponds. The calculation results showed that all locations had a moderate level of diversity, high evenness, and the absence of dominance. Based on the findings of principal component analysis, there was a commonality in parameters that exerted a strong influence on phytoplankton abundance, including nitrate, orthophosphate, and magnesium.

Spatial–temporal variability of phytoplankton community and potentially harmful species in the Golden Horn Estuary (Sea of Marmara) was investigated from October 2018 to September 2019 together with some environmental factors. A total of 148 phytoplankton taxa were identified during the study period. Among these, 134 taxa (90.5%) consisted of diatoms (71 taxa, 48%) and dinoflagellates (63 taxa, 42.5%), while 14 taxa (9.5%) were other groups. Seventeen species were recorded for the first time in the study area. Species richness was highest in October, while it was lowest in August. The species diversity (H') varied according to sampling stations. Cell abundances were higher especially in the middle and upper estuary in spring and summer than in autumn and winter. The abundance of diatoms and euglenophyceans was highest in spring, while the abundance of raphidophycean and cryptophycean was highest in summer. Temperature was correlated positively with total abundance (P < 0.01), but negatively with species diversity (H') (P < 0.01). Several dense algal blooms causing discolouration in surface water occurred in spring and summer. A total of 12 microalgae species known as potentially toxic were detected during this study period. Among these, dinoflagellates Alexandrium cf. tamarense and Dinophysis infundibulum were recorded for the first time in the study area. The increase in species diversity and richness in the upper estuary, and the decrease in frequency of bloom events compared with the previous years indicated the changes in environmental conditions in this study period. Findings showed that phytoplankton might be used as an indicator of the changing environmental conditions in such ecosystems.

Over the past decade, there have been increasing recognition and concern of the toxicological impacts of microplastics (MPs) in the environment, which have been widely found in various marine environments from estuary to deep oceans. Numerous toxicological studies have been conducted on the impacts of MPs on various marine organisms, especially phytoplankton, zooplankton, bivalves, and fish of different trophic levels. These studies mainly focused on the measurements of MPs bioaccumulation and their resulting biological impacts at molecular, metabolic, biochemical, physiological, and organismic levels. This review examines the various studies conducted over the recent years on the toxicology of MPs in different marine organisms, particularly on the bioaccumulation and toxicity of MPs. The impacts of MPs on marine organisms are diverse, and the complexity of organism physiology as well as MPs physical and chemical properties need to be considered. Future studies should consider the environmental relevance of toxicological research and the development of quantitative tools to model the transport, bioaccumulation, and toxicity of MPs. These are important for the real environmental risk assessments of MPs in the marine environments.

Fildes Peninsula, on King George Island, has been greatly influenced by recent rapid climate warming. Lakes are pervasive features of Fildes Peninsula landscapes, some of which are used as water sources for Antarctic stations. We studied seven Fildes Peninsula lakes to explore differences among lakes and between seasons in phytoplankton and bacterioplankton communities. We measured environmental variables, analysed pigments using high-performance liquid chromatography and examined bacterial DNA through high-throughput sequencing of the 16S rRNA gene. The main driver structuring microbial communities was the season (i.e. spring vs autumn). Chlorophyceae were the dominant phytoplankton group in all lakes and both seasons. Indicator bacteria for each season were identified, including Flavobacterium, Polaromonas and Oxalobacteraceae as indicators of spring conditions under thick ice, whereas Frankiales and Verrucomicrobia were indicator species of autumn following the ice-free summer. The indicator species for spring are generally observed in oligotrophic conditions, whereas many of the autumn indicators are commonly found in soils. There were lesser between-lake differences in microbial communities in autumn, at the end of the open-water period, than in spring at the end of the ice-covered period. This study will act as the basis for future assessments of changes in aquatic microbial communities.

The aim of this study is to determine the phytoplankton species found on the shores of Burgaz Island and the basic ecological variables that affect their seasonal distribution between May 2013 and February 2014. Water samples were collected from four stations at six different depths and plankton samples were gathered horizontally and vertically. The analysis of phytoplankton community composition revealed 101 phytoplankton taxa belonging to five classes. As a result of the study, two taxa belonging to the Dinophyceae (Corythodinium frenguellii and Gonyaulax scrippsae) were new records for Turkish coastal waters. Additionally, a taxon belonging to Dinophyceae (Pronoctiluca pelagica) and a taxon belonging to Bacillariophyceae (Nitzschia reversa) were new records for the Sea of Marmara. Prorocentrum micans, was the dominant species throughout all sampling periods. During the study, the highest phytoplankton abundance was observed at 0.5 m depth in May 2013 (138,500 cells l−1) and February 2014 (52,620 cells l−1). Primary ecological variables, such as temperature (9.0–21.5 °C), salinity (15.23–37.22‰) and dissolved oxygen (4.89–15.84 mg l−1), were recorded on each sampling occasion. In addition, nitrite + nitrate–N (NO2 + NO3–N) (0.01–7.37 μg-at N l−1), phosphate (PO4–P) (0.05–51.95 μg-at P l−1) and silicate (SiO4–Si) (0.01–0.20 μg-at Si l−1) concentrations were measured. Chlorophyll a and suspended material values ranged between 0.01–3.17 μg l−1 and 10.0–61.5 mg l−1, respectively. Spearman's rank correlation was used to determine the relationship between phytoplankton species and ecological variables, and Bray–Curtis analysis and Euclidean distance were applied to bring out the similarity between stations.

Little is known about the dynamics of marine food chains spanning primary to higher trophic levels on centennial and longer timescales, especially where the supply of dissolved iron limits primary productivity. To elucidate the long-term dynamics of biological productivity in the Coastal Oyashio (CO), which is a major pathway for transporting dissolved iron into the western North Pacific from winter to spring, we reconstructed the lower trophic level productivity over the last 3000 years in the CO. Our results demonstrate that the concentrations and mass accumulation rates of both Chl-a (chlorophyll a and its derivatives) and biogenic opal used as proxies of primary productivity, and steryl chlorin esters (SCEs) used as that of zooplankton productivity, show a millennial-scale increasing trend and centennial-scale variability beginning ca. AD 400. SCEs were positively correlated with Chl-a, indicating that changes in zooplankton productivity were induced by bottom-up control of primary productivity. The Chl-a and SCEs showed synchronous centennial-scale patterns with a relative abundance of sea-ice-associated diatom species transported by CO, and with a ventilation index in the Okhotsk Sea Intermediate Water. This synchronous pattern indicates that lower trophic-level productivity during the spring bloom responded to the intensity of iron-replete CO.

Phtytoplankton group composition determined by microscopy was compared with high performance liquid chromatography (HPLC) derived from pigment signatures in surface water samples taken bi-weekly and monthly between October 2018 and September 2019 in the Golden Horn Estuary (Sea of Marmara). A total of 80 eukaryotic phytoplankton taxa belonging to eight algal classes were identified in surface water during the study period. Forty-three taxa (54%) were diatoms, 29 taxa (36%) were dinoflagellates and eight taxa (10%) were other phytoflagellates. The average contribution of diatoms to total phytoplankton abundance decreased considerably (41 to 25%), while the average contribution of dinoflagellates and other phytoflagellates increased markedly (59 to 75%) from the lower to the middle estuary. Chlorophyll-a and seven other group-specific pigments, including fucoxanthin, peridinin, chlorophyll-c1 + c2, alloxanthin, 19′-hexanoyloxyfucoxanthin, 19′-butanoyloxyfucoxanthin and divinyl chlorophyll-a were identified in the study area. The relative contribution of the major phytoplankton groups to chlorophyll-a was estimated on three different initial ratio matrices by CHEMTAX. The results obtained were compared with those from microscopic examination. It was concluded that the CHEMTAX method was not accurate enough to characterize the phytoplankton community in the Golden Horn Estuary ecosystem and microscopic analysis was essential to determine the major contributing species to chlorophyll-a.

Changes in phytoplankton composition of the Golden Horn Estuary were investigated following remediation, through seawater transfer from the Strait of Istanbul to the estuary. Average values of Secchi depth, salinity and dissolved oxygen increased during this study when compared with a previous study. The average number of species (S) and species diversity (H′) increased and they correlated positively with Secchi depth, salinity and dissolved oxygen. There was a similar phytoplankton group composition between this and a previous study, however, the species composition differed. A total of 127 taxa consisting of diatoms (66 taxa), dinoflagellates (49 taxa) and others (12 taxa) were identified. Abundance of dinoflagellates and phytoflagellates and their relative contribution to the total phytoplankton abundance increased during this study, however, the abundance of diatoms and their relative contribution decreased notably, as compared with the previous study. There was a significant positive correlation between salinity and dinoflagellates and phytoflagellates (P < 0.01), and also between Secchi depth and dinoflagellates (P < 0.01) in the upper estuary. Additionally, salinity and Secchi depth correlated positively with species diversity (H′) and number of species (S) (P < 0.01). The increase in water transparency probably contributed to the increase in abundance of dinoflagellates and phytoflagellates. The results revealed that water transparency was one of the most important factors affecting phytoplankton composition in the study area. Changes in some environmental conditions following seawater transfer appear to have changed phytoplankton composition. As a result, phytoplankton species were confirmed as a very good indicator of changed environmental conditions.

Our understanding of ice algal responses to the recent changes in Arctic sea ice is impeded by limited field observations. In the present study, environmental characteristics of the landfast sea-ice zone as well as primary production and macromolecular composition of ice algae and phytoplankton were studied in the Kitikmeot Sea near Cambridge Bay in spring 2017. Averaged total chlorophyll-a (Chl-a) concentration was within the lower range reported previously for the same region, while daily carbon uptake rates of bottom-ice algae were significantly lower in this study than previously reported for the Arctic. Based on various indicators, the region's low nutrient concentrations appear to limit carbon uptake rates and associated accumulation of bottom-ice algal biomass. Furthermore, the lipids-dominant biochemical composition of bottom-ice algae suggests strong nutrient limitation relative to the distinctly different carbohydrates-dominant composition of phytoplankton. Together, the results confirm strong nitrate limitation of the local marine system.

Cardiac activity of two White Sea Bivalvia species – Mytilus edulis and Modiolus modiolus – was monitored in situ for one full calendar year every 4 days. During the year, we also assessed the temperature and salinity of the ambient seawater (at intervals of 1 min), measured phytoplankton concentration (every 4 days) and checked the reproductive status of the molluscs (every 2 weeks). Our field study showed a significant linear correlation between the molluscs’ heart rates and the temperature of the ambient seawater. However, during specific periods of the year, we observed that phytoplankton composition or reproductive status became the dominant influence over cardiac activity. Phytoplankton concentrations were generally found to be low throughout the entire year, but two peak periods of drastically elevated phytoplankton concentration were found (April and May), and during April the peak heart rates of the blue mussels significantly increased. Spawning time took place in the middle of June, and at this time the cardiac activity of the molluscs did not change in spite of a 4°C temperature increase in the ambient seawater. Monitoring of the heart rates of the real intertidal blue mussels (animals located at the middle part of intertidal) revealed periodic fluctuations in cardiac activity that correlated strongly with tidal fluctuations. Cardiac activity in M. modiolus was significantly lower than in M. edulis from 9 May to 25 November. On the basis of our data, we concluded that the molluscs’ cardiac activity can serve not only as an indicator of the animals’ physiological conditions, but also as an indicator of changes in ambient factors.

The abundance pattern and species diversity of phytoplankton in the surface waters of the Golden Horn Estuary were investigated between August 2011 and July 2012 in relation to environmental factors. Seventy-eight phytoplankton taxa (38 diatoms, 30 dinoflagellates and 10 phytoflagellates) belonging to eight taxonomic classes were identified in bottle and net samples. Phytoplankton abundance increased in spring and summer (from March to August) and reached its highest (10,429 × 103 cells L−1) during the bloom of Heterosigma akashiwo (Raphidophyceae) in the middle and upper estuary in late May. In general, phytoplankton abundance was higher in the middle estuary indicating more suitable conditions for phytoplankton growth, while species richness and diversity was higher in the lower estuary. The most abundant species were Skeletonema marinoi and Thalassiosira sp. among diatoms; Scrippsiella trochoidea among dinoflagellates; Plagioselmis prolonga and Heterosigma akashiwo among phytoflagellates. Diatoms were more abundant in the lower and middle estuary, while dinoflagellates and phytoflagellates in the upper estuary. The main factors causing the spatio-temporal variation of phytoplankton in the study area were temperature, salinity, water transparency and nutrients. Water transparency in the upper estuary is mostly influenced by organic and inorganic matter carried by two streams. As a result, this area should be considered a potential risk area for future algal blooms.

The beach of Porto de Galinhas is socially and economically important because of the reef environment that attracts a large number of tourists. In order to contribute to the monitoring of the environmental quality of the area, which is subject to strong human pressure, phytoplankton composition was analysed in four fixed sampling station, during 4 months of the dry and rainy periods, at high and low tides and at diurnal spring tides. The phytoplankton community structure and the abiotic parameters varied according to seasonality. Phytoplankton biomass ranged from 0.42 to 5.66 mg m−3 and density ranged from 0.50 to 14.3 cell 103 l−1. A total of 192 taxa were identified, belonging to six divisions. The most representative taxa were Ochrophyta (64.6%), followed by Dinophyta (19.3%). Ostreopsis ovata, Trichodesmium erythraeum, Protoperidinium bispinum, Paralia sulcata, Thalassiosira leptopus and Fragilaria capucina were the most representative species of the environment. Ostreopsis ovata was the only highly frequent and dominant species. The Easterly Wave Disturbance contributed to the occurrence of a large number of freshwater species that were observed on the site. The environment was characterized as oligotrophic, tending toward mesotrophic in the rainy season. The high number of taxa associated with high evenness was indicative of environmental balance. Continental interference was perceived due to the variation of abiotic parameters and of the variation of the phytoplankton community structure.

Quantifying exchange of particulate matter between coastal and open waters is an important and often unresolved issue. Here, we apply phytoplankton order richness as an innovative marine tracer to identify the geographic position of a coastal exchange zone in the SE North Sea, including its variability in time and space. Previous observations on dynamics of suspended particulate matter accumulation resulted in a hypothesized boundary between coastal waters (including the Wadden Sea) and open North Sea waters, the so-called ‘line-of-no-return’. Our study along two transects (Terschelling, Noordwijk) in the Dutch coastal zone showed seasonality patterns in phytoplankton order richness, both for diatoms and flagellates. The coastal Wadden Sea was found to be clearly different from the open North Sea, implying that seasonality in Wadden Sea phytoplankton is at least partly driven by local environmental conditions. Seasonality in flagellates was found to be more uniform than seasonality in diatoms. Stations in the coastal North Sea to a distance of 10 km (Terschelling) to 20 km (Noordwijk) from the shore appeared to be at the inside of the ‘line-of-no-return’. Our findings indicate that this approach is a useful aid in exploring mixing of particulate matter between coastal and open waters and to study the responses of phytoplankton communities to environmental drivers.

Winter cooling and persistent mixing for more than a quarter of year (November to early March) along the North Eastern Arabian Sea (NEAS) results in nutrient enrichment of the euphotic column thereby triggering biological production. Hydrographic characteristics of NEAS during Late Winter Monsoon (LWM) and Early Spring Inter Monsoon (ESIM) and the influence on biological production are overviewed here. Winter convective mixing signatures were evident during LWM with low SST (24°C), high SSS (36.4), deep mixed layers (>100 m) and increased surface nitrate (~1 µM). Open ocean waters observed high chlorophyll a (1–2 mg m−3) and microphytoplankton abundance (1.2–1.5 × 104 cells l−1). Diatoms and green Noctiluca scintillans were the major microphytoplankton identified. ESIM observed gradual stabilization of water column with curtailment of winter signatures and strengthening of Noctiluca scintillans blooms. Mesozooplankton biomass was higher during LWM and decreased towards ESIM with intensification of Noctiluca blooms. However during ESIM, abundance of gelatinous zooplankton occurred in the bloom region. Inter-annual variations were observed in the biological responses along with the hydrographic changes. Thus the convective process during winter monsoon and stabilization of the water column during ESIM plays a significant role in the production pattern of NEAS.

From September 2000 to September 2001 the concentration of chlorophyll a, and the abundance and composition of the phytoplanktonic community was studied in a neritic station of the Mallorca Channel (Western Mediterranean). Sampling was performed approximately every 12 days. Chlorophyll a concentration and phytoplankton abundance reached maxima of 1.79 μg L−l and 352 cells mL−1, respectively. It was a relatively productive period, as a result of the high convective mixing in winter and the prevalence of northern waters during most of the cycle. Phytoplankton proliferations (chlorophyll a concentration >1 mg L−1) were detected in January, February, March and June. Those blooms mainly happened under the influence of northern waters, with the exception of the February proliferation, when mixing conditions were found. During bloom conditions it highlights the presence of coccolithophores as proliferation precursors. During no-bloom situations the phytoplankton community was mainly constituted by nanoplanktonic flagellated forms. The Winter Mixing period was dominated by different groups of nanoflagellates, including coccolithophores, undetermined flagellates and dinoflagellates. However, in the most oligotrophic conditions (from April until November) dinoflagellates were clearly dominant, except in the DCM in summer where diatoms prevailed.

The abundance and community composition of phytoplankton are influenced by a suite of interacting environmental factors. Hong Kong's marine environment features a hydrographic gradient from an estuarine zone in the west to a transition zone in the middle and an oceanic zone in the east. Size fractionation combined with high performance liquid chromatography (HPLC) pigment analyses were used to investigate the phytoplankton communities in different hydrographic zones during summer (July–August 2009) and winter (December 2009–January 2010). Clear temporal and spatial variations in environmental parameters occurred among hydrographic zones. Results of principal component analysis (PCA) revealed that the major deviating factors among hydrographic zones were turbidity and salinity in summer and nitrate and phosphate in winter. Phytoplankton abundance showed significant temporal variations, but no zonal variations. Phytoplankton communities in all hydrographic zones were dominated by cells >5 µm in both summer and winter. Chlorophyll a concentrations for most size fractions correlated significantly with temperature. The high concentration of fucoxanthin indicated that the phytoplankton community was dominated by diatoms in both summer and winter, while dinoflagellates, cryptophytes, cyanobacteria and other minor groups occurred sporadically in low abundance. The spatial pattern of phytoplankton in Hong Kong's coastal seas did not reflect the hydrographic zonation, but the phytoplankton in the semi-enclosed Tolo Harbour and Deep Bay were different from those in the other zones.

The phytoplankton community structure and abundance in the south-eastern Black Sea was measured from February to December 2009 using and comparing high performance liquid chromatography pigment and microscopy analyses. The phytoplankton community was characterized by diatoms, dinoflagellates and coccolithophores, as revealed by both techniques. Fucoxanthin, diadinoxanthin, peridinin and 19′-hexanoyloxyfucoxanthin were the main accessory pigments showing significant correlation with diatom-C r2 = 0.56–0.71, P < 0.05), diatom-C (r2 = 0.85–0.91, P < 0.001), dinoflagellate-C (r2 = 0.39–0.88, P < 0.05) and coccolithophore-C (r2 = 0.80–0.71, P < 0.05), respectively. Microscopy counts indicated a total of 89 species, 71% of which were dinoflagellates, 23% were diatoms and 6% other species (mainly coccolithophores). Pigment-CHEMTAX analysis also indicated the presence of pico- and nanoplankton. Phytoplankton carbon (phyto-C) concentrations were highest in the upper water column, whereas chlorophyll-a (Chl-a) showed a deep maximum. Average phyto-C was higher at the coastal station (291 ± 66 µg l−1) than at the offshore station (258 ± 35 µg l−1), not statistically different (P > 0.05). The coastal station also had higher Chl-a concentrations (0.52–3.83 µg l−1) compared to the offshore station (0.63–2.55 µg l−1), not significant (P > 0.05). Our results are consistent with other studies and indicate that the southern Black Sea is shifting towards mesotrophy with the increasing prevalence of dinoflagellates compared to diatoms.

Investigating forces driving the structure of aquatic communities has long been an important issue in ecology. In the present study, we focused on the effects of changed water supply for aquaculture ponds on phytoplankton, zooplankton and macrozoobenthos communities during two seasons of rearing common carp. We compared these communities between two types of inflow water: surface sources of water – a reservoir pond, two open wells and a small stream and groundwater – deep tube well. Significant changes were observed in environmental variables after the introduction of the groundwater source: oxygen concentration and water hardness decreased, while conductivity, phosphorus and un-ionized ammonia increased. Results revealed that all investigated groups, except Mollusca (macrozoobenthos), decreased in species richness, abundance and biomass due to changed water chemistry, but differed in the level of susceptibility. Rotifera and Cladocera were the most affected showing a sharp decline in density and number of species since 66% of species disappeared from the ponds. The abundance of Copepoda was relatively high although significantly lower under new conditions, with adults being more tolerant to changed inflow water than nauplii larvae. Phytoplankton had the highest potential to replace previous species with newcomers more adapted to changed water chemistry, providing 36 immigrant species, whereas 49 became extinct. Although mainly influenced by fish predation, Chironomidae (macrozoobenthos) were undoubtedly affected by changed water chemistry. These results suggest profound changes in three key ecological groups produced by significant changes of important environmental variables and water quality after the shift from surface to groundwater supply.