Phytoplankton Assemblages Research Articles

Potential Short-Term Effects of Mine Tailings on Phytoplankton Assemblages in the Open Ocean

The disposal of mine tailings into the marine environment is considered an essential option to secure the economic efficiency of deep-sea mining, but it might adversely affects the ecosystem. To examine the potential impacts of tailing disposal from polymetallic nodules and polymetallic sulfide mines on phytoplankton communities, addition experiments of crushed fine particles into surface seawater were conducted in the open Indian Ocean and changes in chlorophyll a fluorescence and community composition were analyzed. The addition of tailings had serious adverse effects on phytoplankton fluorescence and photosynthetic activity, regardless of mine type. The adverse effects seemed to mainly be due to the physical properties of the mine tailings. These also showed discriminatory effects on phytoplankton, resulting in great changes in community composition. The results suggest that mine tailings could have significant adverse impacts on phytoplankton assemblages, but the degree of impact greatly varies depending on the phytoplankton groups. The discriminatory impacts would cause changes in biomass, community structure, and thus ecological function.

Nonspecif ic response of Lake Baikal phytoplankton to anthropogenic impact.

In this study, we present the first results on oxidation stress in Lake Baikal phytoplankton and its adaptation to environmental changes under anthropogenic impact. As was shown, the changing of the dominant species of phytoplankton collected from the surface water layer (~0.3 m) took place from February to June 2021. Phytoplankton were collected at a nearshore station (a littoral station at a distance of ~0.01 km from the shoreline, depth to bottom is ~5 m) and an offshore station (a pelagic station at a distance of ~1 km from the shoreline, depth to bottom is ~543 m). In February, dinoflagellates were dominant (~40 %) as well as diatoms (≤33 %) and green algae (≤12 %). Their biomass was 100 mg·m–3. In March, chrysophytes were dominant (up to 50 %) as well as cryptophytes (≤43 %) and dinoflagellates (≤30 %). Their biomass was 160–270 mg·m–3. In April, biomass increased up to 700–3100 mg·m–3 with the dominance of large cell dinoflagellates (up to 99 %), chrysophytes (up to 50 %), and cryptophytes (up to 35 %). By the end of the first decade of May, the percentage of dinoflagellates decreased and that of cryptophytes increased. In the second decade of May, the percentage of diatoms increased up to ~26–38 % but phytoplankton biomass was minimal (13–30 mg·m–3). By June, the percentage of diatoms in the samples reached 44–75 % at 60–550 mg·m–3. The oxidation stress of phytoplankton as a nonspecific adaptive response to a prolonged, intensive, or recurrent effect of a stress factor was estimated from the content of thiobarbituric acid reactive substances (TBARS). The mean content of these substances (markers of the lipid peroxidation) was determined spectrophotometrically. The oxidation stress of phytoplankton was revealed only when diatom algae dominated. It can be explained by adaptation of algae of other classes to the stress factor. The content of the lipid peroxidation markers in the coastal phytoplankton collected close to the settlement of Listvyanka known as a large touristic center was estimated from 100 to 500 μg·g–1 of dry weight of sample. During the period of diatom blooming in 2016 and 2018, oxidation stress of phytoplankton collected near large settlements was found. In phytoplankton from deep-water pelagic stations most remote from settlements, stress was not revealed. Using the method of gas chromatography, we showed a lower (up to 15 %) content of polyunsaturated fatty acids in phytoplankton characterized by stress occurrence. This confirms cell membrane damages. In Lake Baikal surface water, we found a higher content of synthetic anionic surfactants (sodium alkylbenzene sulfonates), which are components of detergents and cause oxidation stress of hydrobionts (up to 30 ± 4 μg·L–1). The presence of these substances in a water ecosystem can result in exhausting of phytoplankton cell resources, homeostasis imbalance, stress, pathological changes, and rearrangements in phytoplankton assemblage

Seasonal variations in Ichthyofaunal assemblage in relation to Physicochemical parameters, Phytoplankton assemblage and Habscore of the Chathe River

Density and diversity of Ichthyofaunal assemblage in some selected areas of the Chathe River in Nagaland (India) was investigated for a year in 2014 to survey its seasonal distribution in association with a few selected Physicochemical parameters, Phytoplankton assemblage and Habscore of the stream. Various physicochemical parameters were found to be at recommended ranges of tolerance for Ichthyofauna to flourish in the Chathe River. Phytoplankton assemblage was recorded to be comprised of 56 species under 44 genera of 7 classes in the sampling areas of which Bacillariophyceae and Chlorophyceae were witnessed to be the most abundant classes of phytoplankton in the river. Further, amidst this investigation, 40 species of fishes under 23 genera of 10 families and 4 orders were encountered in the river of which Cyprinidae was found to be the most abundant family followed by Nemacheilidae and Psilorhynchidae throughout the year. Seasonal distribution of Ichthyofaunal assemblage and their diversity or dominance in the river was noticed to be directly influenced by abundance of phytoplankton, since herbivore fishes mostly rely on phytoplankton for their nourishment. Habitat quality was recorded in the range of ‘fair’ to ‘good’ during most of the seasons except monsoon when, Ichthyofaunal assemblage was witnessed to be relatively declined in the river. Further canonical correlation analysis and canonical correspondence analysis has revealed the degree of association of Ichthyodiversity indices and Ichthyofamily abundance with physicochemical attributes, phytoplankton diversity and habscore of the surveyed areas of the Chathe River.

Distinct effects of sediment regulation on phytoplankton community assembly in the tributaries and mainstream of the Three Gorges Reservoir

Sediment regulation (SR) maintains the water storage capacity of the Three Gorges Reservoir (TGR), but the influences of SR on riverine phytoplankton communities, especially in the upper reservoir, have not yet been investigated. In this study, the first description of the membership of the phytoplankton community was provided, together with hydrodynamic and environmental factors before, during, and after implementation of SR in the TGR region was investigated. A total of 84 taxa of phytoplankton from 6 phyla were recorded during the three stages of SR. There were no significant impacts of SR on phytoplankton assemblages in the mainstream. But in the tributaries, the replacement components of beta diversity increased from 0.39 to 0.63, and the biomass reduced from 1.36 to 0.49 mg/L. Bray-Curtis distances revealed that phytoplankton community in the mainstream and tributaries became more similar after SR (PERMANOVA, p = 0.592). Based on the investigated environmental variables, stochastic processes play a vital role in structuring the phytoplankton community in the TGR region, although SR decreased the relative importance of stochastic processes for phytoplankton assembly in the tributaries. This study indicates that SR plays a critical role in accelerating turnover rates within phytoplankton communities in tributaries, which has important implications for preventing phytoplankton bloom, and more significantly, for maintaining river–reservoir system sustainable development.

Phytoplankton growth and community shift over a short-term high-CO2 simulation experiment from the southwestern shelf of India, Eastern Arabian Sea(summer monsoon).

The southwestern shelf water of India (eastern Arabian Sea) experiences high seasonality. This area is one of the understudied regions in terms of phytoplankton response to the projected ocean acidification, particularly, during the summer monsoon when phytoplankton abundance is high. Here we present the results of a short-term simulated ocean acidification experiment (ambient CO2 424 µatm; high CO2, 843, 1138 µatm) on the natural phytoplankton assemblages conducted onboard (R. V. Sindhu Sadhana) during the summer monsoon (Aug 2017). Among the dissolved inorganic nutrients, dissolved silicate (DSi) and nitrate + nitrite levels were quite low (< 2µM). Phytoplankton biomass did not show any net enhancement after the incubation in any treatment. Both marker pigment analysis and microscopy revealed the dominance of diatoms in the phytoplankton community, and a significant restructuring was noticed over the experimental period. Divinyl chlorophylla (DVChla) containing picocyanobacteria and 19'-hexanoyloxyfucoxanthin (19'HF) containing prymnesiophytes did not show any noticeable change in response to CO2 enrichment. A CO2-induced positive growth response was noticed in some diatoms (Guinardia flaccida, Cylindrotheca closterium, and Pseudo-nitzschia sp.) and dinoflagellates (Protoperidinium sp. and Peridinium sp.) indicating their efficiency to quickly acclimatize at elevated CO2 levels. This is important to note that the positive growth response of toxigenic pennate diatoms like Pseudo-nitzschia as well as a few dinoflagellates at elevated CO2 levels can be expected in the future-ocean scenario. The proliferation of such non-palatable phytoplankton may impact grazing, the food chain, and carbon cycling in this region.

Gradient rise in seepage pollution levels in tailings ponds shapes closer linkages between phytoplankton and bacteria

A large number of tailings ponds formed by slag accumulation have become serious environmental hazards. Spatially high potential energy and long-term accumulation may result in gradient-changing seepage pollution. The assemblages of phytoplankton and bacteria are widely used as assessment indicators. In this study, we investigate the changes in phytoplankton and bacterial assemblages in tailing pollution. The results showed that there are temporal and spatial variabilities in seepage pollution. The abundance and diversity of phytoplankton and bacteria decreased with increasing pollution. However, Synedra acus (diatom) and Polynucleobacter (bacteria) were positively correlated with pollution levels (r = 0.37, P < 0.05; r = 0.24, P < 0.05). Heavy metals are the main contributors to bacterial changes (16.46%), while nutrients are for algae (13.24%). Tailings pond pollution reduced the number of phytoplankton and bacterial linkages. However, more pollution broke the originally independent modules of phytoplankton and bacteria, and they produced more positive correlations (79.39%; 87.68%). Microcystis sp. and Limnobacter were the key nodes of the co-occurrence network in the polluted areas. Exploring the interactions between bacteria and phytoplankton within different pollution levels could provide insights into biological interaction patterns and the bioremediation of tailings ponds.

Optical and biogeochemical properties of diverse Belgian inland and coastal waters

Abstract. From 2017 to 2019, an extensive sampling campaign was conducted in Belgian inland and coastal waters, aimed at providing paired data of optical and biogeochemical properties to support research into optical monitoring of aquatic systems. The campaign was focused on inland waters, with sampling of four lakes and a coastal lagoon during the growth season, in addition to samples of opportunity from other four lakes. Campaigns also included the Scheldt estuary over a tidal cycle and two sampling campaigns in the Belgian coastal zone. Measured parameters include inherent optical properties (absorption, scattering and beam attenuation coefficients, near-forward volume scattering function, turbidity), apparent optical properties (Secchi disc depth, substrate and water-leaving Lambert-equivalent bi-hemispherical reflectance), and biogeochemical properties (suspended particulate matter, mineral fraction of particle mass, particle size distribution, pigment concentration, DNA metabarcoding, flow microscopy counts, and bottom type classification). The diversity of water bodies and environmental conditions covered a wide range of system states. The chlorophyll a concentration varied from 0.63 to 382.72 mg m−3, while the suspended particulate matter concentration varied from 1.02 to 791.19 g m−3, with mineral fraction varying from 0 to 0.95. Depending on system and season, phytoplankton assemblages were dominated by cyanobacteria, green algae (Mamiellophyceae, Pyramimonadophyceae), or diatoms. The dataset is available from https://doi.org/10.1594/PANGAEA.940240 (Castagna et al., 2022).

Phytoplankton assemblage and chlorophyll a along the salinity gradient in a hypoxic eutrophic tropical estuary-Ulhas Estuary, West Coast of India

Phytoplankton assemblage and chlorophyll a along the salinity gradient and oxygen zonation were studied in Ulhas Estuary. Oxic condition exist in euhaline region of the estuary that receives oxygenated coastal waters, while, poly-meso-oligohaline region is hypoxic due to the accumulation of voluminous amount of pollutants from industrial effluents, domestic/sewage and agricultural discharges. Additionally, anthropogenically generated nutrients enhanced phytoplankton biomass (chlorophyll a) and their senescence also led to hypoxia. The dominance of diatoms (>70%) was observed in the euhaline-oxic region, while a tremendous decrease in their contribution (18%) was observed in the oligohaline region. Meso to oligohaline region of the estuary is governed by cyanophytes and chlorophytes due to their affinity towards low salinity and high dissolved inorganic nutrients. Carlson's Trophic State Index (TSI) further substantiated the estuary as eutrophic. Additionally, the study could identify the adaptation of cyanophytes and chlorophytes in oxygen deficient water.

Reply to Stafford's (2022) comment on “Seaweed ecosystems may not mitigate CO2 emissions” by Gallagheret al. (2022)

AbstractThe comment qualitatively suggests that seaweed ecosystems are global carbon sinks. This was in contradiction to the article that showed that seaweed ecosystems are on average measurably carbon sources within the canopy. Furthermore, this was amplified by the remineralization of a large fraction of exported seaweed production, as estimated from published parameters. It appeared that the comments’ conclusion was mistaken from two standpoints. First, a view that the article did not consider the impact of the phytoplanktonic assemblage on the seaweed ecosystems’ global sequestration rate. This had been previously calculated as likely, not significant. Second, a view that the consumption and subsequent respiration of exported material cannot be included in ecosystems that are generally open to allochthonous organic carbon subsidies. Nevertheless, the comment does raise the importance of a more holistic view in assessing sequestration services. The response expands the article's arguments from different standpoints and consequences to illustrate where the comment has been mistaken, and points out where the article was misread. We also expand on the comments’ call for a more holistic approach by being more explicit on what drives both sequestration and mitigation through the extreme circumstances where this could be maximized, including phytoplankton contributions.

Comparative Analysis of Total and Size-Fractionated Chlorophyll a in the Yellow Sea and Western Pacific.

Measurements of different size-fractionated chlorophyll a concentrations (Chl a) of phytoplankton assemblages in situ are vital for advancing our understanding of the phytoplankton size structure and thus the marine biogeochemical cycle. In the present study, we thus made a comparative analysis of total and size-fractionated Chl a in the Yellow Sea (YS) and Western Pacific (WP). Our results suggest that the total Chl a was highly variable in the YS (averaging ~1.02 μg L−1) and was generally 3–4-fold more than that in the WP (averaging ~0.30 μg L−1). The pico-sized Chl a had a significant contribution to total Chl a in the WP (range 75–88%), while the average contributions of the nano-sized and pico-sized Chl a to total Chl a in the YS were 47 and 38%, respectively, suggesting that a majority of the total Chl a in the YS was associated with nano- and picophytoplankton. Moreover, we applied the generalized additive models (GAMs) to explore the relationships between the total Chl a and that contained in each of the three size classes. These GAMs relationships suggested a continuum from picophytoplankton dominated waters to large phytoplankton (cells> 2 μm) domination with increasing Chl a. Finally, we made a comparison of the total Chl a obtained with GF/F filters and that measured from size-fractionated filtration and revealed that their corresponding concentrations are in good agreement, indicating the size-fractionated filtration had no effect on total Chl a determination.

Phytoplankton Diversity of a Demineralized Urban Wetland of Meghalaya State of Northeast India: The Spatio-temporal Variations and the Role of Abiotic Factors

The authors analyze phytoplankton diversity of a small urban wetland of Meghalaya to assess biodiversity and limnology interest of small water bodies. This “slightly acidic-circumneutral, demineralized and soft water” subtropical wetland reveals diverse phytoplankton (64 species), indicates high desmid richness and highlights the speciose littoral constellations of up to 55-58 species per sample. Phytoplankton comprises dominant quantitative component of net plankton and registers Charophyta dominance; Chlorophyta &gt; Bacillariophyta &gt; Dinozoa &gt; Chrysophyta &gt; Cyanobacteria depict sub-dominance, and Euglenozoa and Cryptophyta show poor abundance at the littoral and semi-limnetic regions. The richness of phytoplankton and abundance of phytoplankton, Charophyta, Chlorophyta, Dinozoa, Chrysophyta and Cyanobacteria follow bimodal spatio-temporal variations. Closterium, Cosmarium, Staurastrum, Micrasterias, Netrium, Staurodesmus and Scenedesmus are notable genera, and 14 species collectively influence phytoplankton abundance. Phytoplankton registers high species diversity, lower dominance and high evenness. Amongst 15 abiotic factors, only the rainfall and sulphate exert notable influence individually, while the canonical correspondence analysis registers lower cumulative influence of the selected 10 factors on the littoral and semi-limnetic phytoplankton assemblages. This study merits interest for neglected biodiversity and ecology of small aquatic biotopes of India and urban wetlands in particular.

Water quality parameters affect dynamics of phytoplankton functional groups in Lake Hawassa, Ethiopia

The water quality of Lake Hawassa has been deteriorating due to high influent loads from various sources, including influents of a hospital, industries, hotels, and agricultural runoff, which can induce changes in Reynolds functional groups of phytoplankton (RFGs). The functional associations of algae can also be affected by the dominant zooplankton and macrophytes coverage. RFGs (species with similar ecological requirements) are indicative of water quality but have not been studied in Lake Hawassa. The functional approach detects stressor-induced changes in phytoplankton assemblages more effectively than taxonomy-based methods due to its higher discriminatory power. The main objective of this study was, therefore, to investigate the factors affecting the dynamics of RFGs in Lake Hawassa through monthly sampling (April–August in 2019) from four sites. A total of 130 species of phytoplankton were identified and classified into 17 RFGs. The dominant ten RFGs (D, J, K, LO, M, N, P, SN, TD,and W2) contributed 96.1% of the total fresh weight biomass. Redundancy analysis indicated that the RFGs were correlated significantly with electrical conductivity, dissolved oxygen, pH, turbidity, Secchi depth, and total phosphorus revealing the overriding importance of these parameters in influencing the dynamics of the algal functional assemblage in Lake Hawassa. The results supported our hypothesis that the biotic and the human-induced abiotic factors have significant impact on RFGs. Our findings could serve as baseline information for efforts directed toward water quality improvements.

Dynamics of phytoplankton community in scallop farming waters of the Bohai Sea and North Yellow Sea in China

BackgroundAs the major suppliers of food for higher consumers, phytoplankton are closely related to the yield, nutritional ingredients and even toxin contents of mariculture animals, potentially influencing the human health when they are consumed. With the increase of shellfish culture density, phytoplankton in the coastal waters have been excessively consumed in recent years, and the nutrients they depend on are becoming more and more limited, which severely restrict the shellfish mariculture and threaten the coastal ecosystems.ResultsIn the present study, nutrient concentrations, phytoplankton assemblages and scallop growth status were investigated in the main bay scallop farming waters of the Bohai Sea (Qinhuangdao site) and North Yellow Sea (Zhuanghe site) in 2018. Both phosphate and silicate limitations were observed at the two sites, with the major determinant of phytoplankton assemblages being silicate in Qinhuangdao and phosphate in Zhuanghe, respectively. The phytoplankton assemblages at the two sites displayed different community structures and succession patterns. The phytoplankton community was dominated by dinoflagellates and diatoms in Qinhuangdao, while dinoflagellates were the most abundant group in Zhuanghe, which accounted for 41.9% of the total phytoplankton abundance. The dominant genera of diatoms in Qinhuangdao were Skeletonema, Thalassiosira and Leptocylindrus, while those in Zhuanghe were Thalassiosira and Cyclotella. Greater biomass and more appropriate structure of phytoplankton contributed to higher growth rate and glycogen content of cultured bay scallops.ConclusionsOur study characterized the relationship between nutrient concentration, phytoplankton community and scallop mariculture in the main bay scallop farming waters in northern China. The results suggest that, as nutrient limitation intensified, dinoflagellates are becoming the dominant phytoplankton species in the scallop farming waters of the Bohai Sea and the North Yellow Sea, which is harmful to the coastal mariculture.

How does a short-term hydrological disturbance changes the phytoplankton assemblages of a small lake?.

How does a short-term hydrological disturbance changes the phytoplankton assemblages of a small lake?.

Exploring Variability of Trichodesmium Photophysiology Using Multi-Excitation Wavelength Fast Repetition Rate Fluorometry.

Fast repetition rate fluorometry (FRRf) allows for rapid non-destructive assessment of phytoplankton photophysiology in situ yet has rarely been applied to Trichodesmium. This gap reflects long-standing concerns that Trichodesmium (and other cyanobacteria) contain pigments that are less effective at absorbing blue light which is often used as the sole excitation source in FRR fluorometers—potentially leading to underestimation of key fluorescence parameters. In this study, we use a multi-excitation FRR fluorometer (equipped with blue, green, and orange LEDs) to investigate photophysiological variability in Trichodesmium assemblages from two sites. Using a multi-LED measurement protocol (447+519+634 nm combined), we assessed maximum photochemical efficiency (Fv/Fm), functional absorption cross section of PSII (σPSII), and electron transport rates (ETRs) for Trichodesmium assemblages in both the Northwest Pacific (NWP) and North Indian Ocean in the vicinity of Sri Lanka (NIO-SL). Evaluating fluorometer performance, we showed that use of a multi-LED measuring protocol yields a significant increase of Fv/Fm for Trichodesmium compared to blue-only excitation. We found distinct photophysiological differences for Trichodesmium at both locations with higher average Fv/Fm as well as lower σPSII and non-photochemical quenching (NPQNSV) observed in the NWP compared to the NIO-SL (Kruskal–Wallis t-test df = 1, p < 0.05). Fluorescence light response curves (FLCs) further revealed differences in ETR response with a lower initial slope (αETR) and higher maximum electron turnover rate () observed for Trichodesmium in the NWP compared to the NIO-SL, translating to a higher averaged light saturation EK (= /αETR) for cells at this location. Spatial variations in physiological parameters were both observed between and within regions, likely linked to nutrient supply and physiological stress. Finally, we applied an algorithm to estimate primary productivity of Trichodesmium using FRRf-derived fluorescence parameters, yielding an estimated carbon-fixation rate ranging from 7.8 to 21.1 mgC mg Chl-a–1 h–1 across this dataset. Overall, our findings demonstrate that capacity of multi-excitation FRRf to advance the application of Chl-a fluorescence techniques in phytoplankton assemblages dominated by cyanobacteria and reveals novel insight into environmental regulation of photoacclimation in natural Trichodesmium populations.

Using null models and species traits to optimize phytoplankton monitoring: An application across oceans and ecosystems

Phytoplankton assemblages are privileged descriptors of the ecological status of marine ecosystems regularly included in routine monitoring programmes. The high spatial and temporal variability of phytoplankton and the intrinsic difficulties of species identifications, however, combine in making reiterate assessments of this component of marine biota particularly demanding. Coarse levels of taxonomic resolution (e.g., genus, family) or morpho-functional categories have been proposed to reduce identification efforts or to ease the analysis of phytoplankton assemblages for monitoring purposes, although with contrasting outcomes. A major issue is that, in the absence of control for the loss of information associated to these alternative approaches, their application may lead to poor representations of genuine spatial and/or temporal patterns of assemblages in relation to natural and anthropogenic sources of variation. We provided a new approach to reduce the efforts required to analyse phytoplankton assemblages that integrate morpho-functional classification of phytoplankton with the use of null models to estimate the consequent loss of information on species-level community patterns. Null models for information loss were built by randomly grouping the original species variables into a progressively decreasing number of groups, in order to identify the minimum number of aggregate variables needed to detect community patters as at species level. Aggregate variables were then defined as morpho-functional groups, by grouping species on the basis of a combination of morpho-functional traits, including general taxonomy, cell size, shape, elongation and complexity. We applied the approach to six case studies investigating the response of phytoplankton assemblages from marine and transitional water ecosystems under different environmental settings in areas spanning the world’s ocean, including coral atolls, mangroves, estuaries, coastal lagoons and inlets. The approach allowed obtaining parsimonious sets of morpho-functional groups, which were suitable to detect changes in phytoplankton assemblage structure as at species level in all case studies. Trait-based approaches to phytoplankton research and monitoring are crucial to shed light on processes underlying phytoplankton community assembly and dynamics in the face of global change. In this perspective, our framework incorporates cost-effectiveness, instances from traditional monitoring programmes aiming at the detection of community patterns, and the current need for a deeper understanding of functional responses of phytoplankton to environmental drivers.

Spatio-temporal variations of phytoplankton assemblage in coastal waters of Maharashtra, north-eastern Arabian Sea

Seasonal variations in phytoplankton species and abundance along the coast of Maharashtra from two different locations (Mumbai and Ratnagiri) and depths were investigated during August 2014-May 2017. A total of 84 species of phytoplankton were recorded from the region out of which 67 were diatoms, 16 dinoflagellates and one blue green alga. Seventy-five and 60 species of phytoplankton were recorded from Ratnagiri and Mumbai respectively. Diatoms dominated the phytoplankton community (81.7-93.3%) followed by dinoflagellates (4.7-7.2%) and blue green algae in both locations. Maximum phytoplankton density was recorded during post-monsoon season followed by pre-monsoon and monsoon seasons at Mumbai and Ratnagiri. Highest average phytoplankton cell density recorded was 9.09 x 104 cells l-1 and 4.06 x 104 cells l-1 during post-monsoon season at Ratnagiri and Mumbai respectively. Maximum cell density was observed at 20 m depth from Mumbai and Ratnagiri. Thalassiosira subtilis, Trieres mobiliensis, Skeletonema costatum, Coscinodiscus centralis and Ditylum brightwelli were the most abundant phytoplankton species recorded at Mumbai, whereas Chaetoceros curvisetus, S. costatum, Trichodesmium erythraeum, Chaetoceros lorenzianus and Ditylum brightwelli were abundant in Ratnagiri waters. The blue green alga, T. erythraeum was abundantly recorded during pre-monsoon season. Species diversity index (H’) ranged from 4.72 to 5.52 and was higher during post-monsoon season compared to pre-monsoon and monsoon. Highest phytoplankton diversity was observed at 20 m depth compared to 40 m depth.Keywords: Arabian Sea, Diversity, Mumbai, Phytoplankton, Ratnagiri

Spatiotemporal Variation in Phytoplankton and Physiochemical Factors during Phaeocystis globosa Red-Tide Blooms in the Northern Beibu Gulf of China

Phaeocystis globosa blooms frequently in the Beibu Gulf of China. This species has a distinct life cycle that includes colonies and solitary cells. Colonies are formed during a bloom, while solitary cells are produced between blooms. Information about the abundance of solitary cells and other picophytoplankton in the northern Beibu Gulf is limited. To elucidate phytoplankton variation trends during periods of frequent P. globosa blooms and to determine the main physiochemical factors affecting phytoplankton distribution, four cruises were conducted between November 2018 and April 2019. Seawater was collected, and water temperature, salinity, and nutrient concentrations were simultaneously determined. Redundancy analysis was performed to understand the relationship between environmental factors and phytoplankton assemblages. Seven phytoplankton clusters were present during the cruises. Picophytoplankton abundance (including Synechococcus and Picoeukaryote groups I and II) dominated during the four cruises. Synechococcus abundance was restricted by the low temperatures in winter, decreasing from November to February and increasing in April. Picoeukaryote I abundance was almost unaffected by low temperatures and was mainly affected by nutrient concentration. P. globosa solitary cell abundance increased from November to January and decreased in February and April, and phosphorus was the key factor affecting P. globosa blooms. This is the first study to reveal the abundance and distribution of P. globosa solitary cells in this area.

Phytoplankton Composition and Ecological Status of Lakes with Cyanobacteria Dominance.

Phytoplankton is one of the five biological quality elements used in the assessment of the ecological status of surface waters according to the European Water Framework Directive established in 2000. In this study, we determined the ecological status of three small and shallow lakes in the Polesie Plain, Eastern Poland, by using indices based on phytoplankton assemblages. The predominant phytoplankton of all three lakes were filamentous cyanobacteria, both heterocystous and non-heterocystous, represented by the genera Aphanizomenon, Planktothrix, Limnothrix, and Planktolyngbya. We used the Hungarian Q index, German PSI (Phyto-See-Index), and recently developed PMPL (Phytoplankton Metrics for Polish Lakes) for Polish lakes. We compared the results from the calculation of the indices to physicochemical data obtained from the lake water and Carlson’s Trophy State Index (TSI). On the basis of TSI, Gumienek and Glinki lakes were classified as advanced eutrophic, whereas Czarne Lake had a better score and was classified as slightly eutrophic. The trophic state was generally confirmed by the ecological status based on phytoplankton indices and also showed the diverse ecological situation in the lakes studied. Based on the Polish PMPL, Gumienek Lake was classified as having bad status (ecological quality ratio (EQR) = 0.05), whereas Glinki and Czarne lakes were classified within the poor status range (EQR = 0.25 and 0.35, respectively). However, based on the German PSI, the lakes were classified in a different manner: the status of Gumienek and Czarne lakes was better, but unsatisfactory, because they were still below the boundary for the good status category recommended by the European Commission. The best ecological status for the studied lakes was obtained using the Q index: Gumienek Lake with EQR = 0.42 had a moderate status, and Czarne Lake with EQR = 0.62 obtained a good status. However, Glinki Lake, with EQR = 0.40, was classified at the boundary for poor and moderate status. Based on our study, it seems that the best index for ecological status assessment based on phytoplankton that can be used for small lakes is the Polish (PMPL) index.

Comparative trace metal assessment in phytoplankton using size and density fractionation

Trace metal assessment in marine phytoplankton is challenging due to complex assemblages and variable amounts of abiogenic suspended particulates. Using aliquots, this study were able to compare trace metal concentrations in plankton samples subjected to size and density fractionation. Elements including Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Hg, and Pb were analyzed by inductively coupled plasma mass spectrometer (ICP-MS). Trace metals were found to be significantly higher in size fractionated than density fractionated plankton for both small (1.2–50 μm) and large (50–120 μm) fractions. Metals from abiogenic sources (61–88%) also significantly contributed to trace metals detected in 1.2–120 μm suspended particulates collected from Kaohsiung Harbor. Results suggest that size fractionation can potentially overestimate trace metals in phytoplankton. It is therefore recommended combining the two methods by first isolating different size fractions followed by density fractionation to separate phytoplankton from zooplankton, and abiogenic particulates from phytoplankton assemblages, respectively.