Summer Phytoplankton Community Research Articles

Characteristics and Factors Influencing Summer Phytoplankton Community Structures of Typical Lakes in Southeast Hubei, China

Phytoplankton plays a key role in the stabilization of aquatic ecosystems. However, there is a lack of research on the structure of phytoplankton communities and their influencing factors in shallow lakes in Southeast Hubei. In this study, four typical lakes were selected in the summer of 2019, and the phytoplankton community structure and its drivers were investigated for each lake. The results showed that the number of phytoplankton species, dominant species, biomass, and abundance varied among lakes. A comprehensive trophic level index (TLI) assessment showed that Lake Xiandao was oligotrophic, Lake Baoan was light eutrophic, and Lake Wang and Lake Ci were moderate eutrophic. The Shannon–Wiener, Margalef, and Pielou indices showed that the phytoplankton communities of Lake Wang and Lake Ci are less stable, and the water bodies are more severely contaminated. In contrast, the communities of the Lake Baoan and Lake Xiandao are more stable and have superior water quality. A redundancy analysis (RDA) indicated that the primary variables influencing phytoplankton community structures were pH and water temperature (WT) (Lake Ci); permanganate index (CODMn) and pH (Lake Xiandao); WT and total nitrogen (TN) (Lake Wang); and WT and total phosphorus (TP) (Lake Baoan).

Spatial heterogeneity in summer phytoplankton communities shaped by anthropogenic and natural effects in typical coastal bay-river systems in South China

Phytoplankton community spatial scales vary in typical coastal bay-river systems under natural and anthropogenic effects. However, their relative importance in shaping phytoplankton spatial heterogeneity has been largely uncharacterized in the literature. In this study, we performed comprehensive analyses using field monitoring, meteorological, and remote sensing datasets from a coastal bay-river system in South China (the Guangdong-Hong Kong-Macao Greater Bay-Pearl River tributaries) to examine phytoplankton spatial heterogeneity and main effects. We showed that water quality in the four water bodies of the typical coastal bay-river system in South China were relatively poor. Phytoplankton community abundance, taxonomic grouping, dominant species, and species similarity varied significantly in response to environmental gradients. We showed that Cyanophyta, Bacillatiophyta, and Chlorophyta were dominant phyla, and we observed regional variations in taxonomic groups and dominant species. Phytoplankton abundance was significantly higher in Dongjiang River and water bodies in branched bays when compared with other regions due to nutrient input from extensive agricultural and urban development, where the dominant phylum was Cyanophyta. Cyclotella (Bacillariophyta) had relatively high abundance and was widely distributed throughout the coastal bay-river system, except in the Dongjiang River. Melosira (Bacillariophyta) had relatively high abundance in Dongjiang and Xijiang Rivers, Merismopedia (Cyanophyta) dominated in the Dongjiang River and highly urbanized branched bay areas, while Microcystis (Cyanophyta) only dominated in Beijiang and Xijiang Rivers. Dominant species distributions showed apparent spatial heterogeneity in phytoplankton community composition. Species similarities between different water bodies were generally low, but phytoplankton species similarities between the Dongjiang River and water bodies in the branched bay area were relatively high, which indicated that water exchange associated with freshwater and nutrient inputs may have profoundly influenced species dispersal and dominant phytoplankton species. Redundancy analyses (RDA) demonstrated that pH, elevation, photosynthetically active radiation (PAR), dissolved active phosphorus (SRP), total dissolved phosphorus (TP), total nitrogen (TN), and nitrate nitrogen (NO3−-N) values - associated with nutrient and climate indicators were the main factors explaining structured phytoplankton spatial distributions. Variance partitioning analyses (VPA) showed that phytoplankton community variations were explained by anthropogenic factors (eutrophication) in summer. Our study improves our understanding of the natural and anthropogenic effects on phytoplankton spatial heterogeneity and provides basic study data for long-term phytoplankton evolution from river to bay areas.

Seasonal Dynamics of Primary Production in the Southeastern Bering Sea Assessed Using Continuous Temporal and Vertical Dissolved Oxygen and Chlorophyll‐a Measurements

AbstractThe Bering Sea and other high‐latitude systems are experiencing unprecedented changes related to climate warming and the consequent loss of sea ice. Understanding how such changes influence primary production is a pressing question. Here, we quantify primary production rates in the southeastern Bering Sea over 4 years (2016–2019) at daily to weekly time resolution. A moored high‐resolution Profiling Crawler was used in combination with in situ sampling to collect physical and biological data in the ocean's upper 50 m. We used dissolved oxygen (O2) data to estimate gross and net primary production (NPP), and chlorophyll‐a (Chl‐a), temperature, and irradiance data to model NPP rates. We then assessed seasonal variation in phytoplankton production rates, phytoplankton community growth rates () and explored to what extent summer phytoplankton community growth rates may be influenced by nitrogen limitation. Our analyses revealed that the majority of gross primary production (GPP) and net community production occurs in association with the spring phytoplankton bloom. After the bloom, the water column generally experienced low GPP and net biological carbon consumption. Phytoplankton growth rates were commonly suppressed in late summer due to apparent nitrogen depletion. Using high temporal resolution vertically resolved measurements of O2 and Chl‐a, our analyses provides important insight into how biogeochemical cycles, phytoplankton community growth rates, and carbon available for export vary seasonally in the southeastern Bering Sea.

Influence of Some Environmental Factors on Summer Phytoplankton Community Structure in the Varna Bay, Black Sea (1992–2019)

During the last decades, a decrease in the nutrients and an increase in marine temperature on the surface of the Varna Bay of the Black Sea have been registered. The main aim of this study was to establish the influence of some environmental factors (SST, TP, DIN) on the structure of the phytoplankton and to define what part of these dynamics results from the changes in temperature. Bivariate correlation and Nonlinear regression analyses were used to establish the connection between factors of the environment and the quality parameters of different size and taxonomic groups of phytoplankton. The rising SST proved to statistically significantly influence the decrease in the abundance of nano-phytoplankton (50.9%), the abundance and biomass of micro-phytoplankton (53%; 33.2%), the Bacillariophyceae (49.5%; 35.6%), and the biomass of the species of group “Other” (51.4%). The decreasing TP has a significant influence on the decrease in the abundance and biomass of the diatoms and the biomass of group “Other”. The decreasing DIN significantly affects the decrease in the abundance and biomass of Dinophyceae. The analyses showed that rising temperatures had a leading role in the changes in the taxonomic and size structure of phytoplankton during the period 1992–2019.

Summer phytoplankton species composition and abundance in the southern basin of Lake Baikal and Irkutsk Reservoir

Phytoplankton has higher species richness in summer, when water temperatures are higher than in other seasons in aquatic ecosystems. Here, we characterized phytoplankton communities using microscopy and environmental parameters (temperature, pH, transparency) in the southern basin of Lake Baikal and Irkutsk Reservoir, which is directly connected with the lake as it is the upper part of Angara River, the Lake Baikal outlet. Surface water temperature was 10.1-18.4 °С in the southern basin of Lake Baikal and 14.9-20.0 °С was in Irkutsk Reservoir, pH values were similar both in the lake and the reservoir (8.09-8.44 and 7.96-8.28, respectively), and Secchi disc water transparency was 4.5-9.0 m in the lake and 2.5-4.5 m in the reservoir. The phytoplankton community included 104 species from 7 high-rank taxa such as Chrysophyta (36), Chlorophyta (30), Bacillariophyta (22), Cyanobacteria (11), Cryptophyta (2), Dinophyta (2), and Haptophyta (1). Species composition of summer phytoplankton communities of the Irkutsk Reservoir and the southern basin of Lake Baikal were different, however the community composition in terms of high-level phylotypes was very similar. At the same time, a large number of small-cell cyanobacteria were identified in the lake. A high species richness of Chrysophyta, genus Dinobryon (11 species) and silica-scaled chrysophytes (22) was founded. The composition of dominant species of the southern basin of Lake Baikal and Irkutsk Reservoir became wider compared to data published earlier, and included Cyanodictyon planctonicum, Cyanodictyon sp., Microcystis sp., Dinobryon sociale, Dinobryon sociale var. americanum, Chlorella vulgaris and Mychonastes homosphaera.

Effects of Miniaturization of the Summer Phytoplankton Community on the Marine Ecosystem in the Northern East China Sea

After the construction of the Three Gorges Dam (Changjiang River), the northern East China Sea has been exposed to major environmental changes in the summer due to climate change and freshwater control. However, little is known regarding phytoplankton in this area. Here, we investigated differences in the summer phytoplankton-community structure as a consequence of marine-environment changes from 2016 to 2020. In the 2000s, the key dominant species in the summer phytoplankton community in the northern East China Sea were diatoms and dinoflagellates. In this study, however, nanoflagellates of ≤20 µm were identified as the dominant species throughout the survey period, with abundances ranging from 43.1 to 69.7%. This change in the phytoplankton-community structure may be ascribed to low nutrient concentrations in the area, especially phosphate, which was below the detection limit, seriously hampering phytoplankton growth. The relative contribution of picophytoplankton to the total chlorophyll a biomass was highest in the surface mixed layer with low nutrient concentrations. Spatially, higher percentages were observed along the east-side stations than the west-side stations, where nutrient concentrations were relatively high. Conclusively, decreased nutrients led to phytoplankton miniaturization. Accordingly, as the dominance of picophytoplankton increases, energy transfer is expected to decrease at the upper trophic level.

Phytoplankton Community Patterns in the Northeastern South China Sea: Implications of Intensified Kuroshio Intrusion During the 2015/16 El Niño

AbstractKuroshio intrusion into the South China Sea (SCS) varies seasonally and interannually under different climatic conditions. To characterize the intensity of the climate‐driven Kuroshio intrusion and its impact on the phytoplankton community in the northeastern South China Sea (NESCS), two cruises were conducted during the 2015/16 El Niño event. In situ observations and remote sensing data showed that the Kuroshio strongly intruded into the SCS in both summer and winter. The summer phytoplankton community was dominated by cyanobacteria (Trichodesmium erythraeum), associated with high surface temperature, shallower mixed layer depth, and low nutrient concentrations. The winter phytoplankton community was mainly dominated by cosmopolitan diatoms (Thalassiosira diporocyclus, Thalassionema nitzschioides, and Chaetoceros socialis), associated with low surface temperature, deeper mixed layers, and relatively higher nutrient concentrations. Meanwhile, the elevated abundance of T. erythraeum coupled well with the Kuroshio intrusion index during the El Niño summer. The phytoplankton network was unstable in summer but not in winter, induced by the Kuroshio intrusion. Our findings show that intensified Kuroshio intrusion during the El Niño event was a vital driving force for reshaping phytoplankton community dynamics of the NESCS through lateral advection and affecting temperature, mixed layer depth, and nutrient supply.

Sea ice presence is linked to higher carbon export and vertical microbial connectivity in the Eurasian Arctic Ocean

Arctic Ocean sea ice cover is shrinking due to warming. Long-term sediment trap data shows higher export efficiency of particulate organic carbon in regions with seasonal sea ice compared to regions without sea ice. To investigate this sea-ice enhanced export, we compared how different early summer phytoplankton communities in seasonally ice-free and ice-covered regions of the Fram Strait affect carbon export and vertical dispersal of microbes. In situ collected aggregates revealed two-fold higher carbon export of diatom-rich aggregates in ice-covered regions, compared to Phaeocystis aggregates in the ice-free region. Using microbial source tracking, we found that ice-covered regions were also associated with more surface-born microbial clades exported to the deep sea. Taken together, our results showed that ice-covered regions are responsible for high export efficiency and provide strong vertical microbial connectivity. Therefore, continuous sea-ice loss may decrease the vertical export efficiency, and thus the pelagic-benthic coupling, with potential repercussions for Arctic deep-sea ecosystems.

Trophic state assessment based on summer phytoplankton community structure and trophic indices: a small tectonic lake in Turkey

Trophic state assessment based on summer phytoplankton community structure and trophic indices: a small tectonic lake in Turkey

Extreme and gradual rainfall effects on winter and summer estuarine phytoplankton communities from Patagonia (Argentina)

Rainfall events bring both, terrigenous materials (including DOM) and nutrients to the aquatic system (e.g., via riverine runoff) having potential effects on the structure and metabolism of the phytoplankton communities. As extreme rainfall events in Patagonia occurred more frequently in the last decade (2010–2019) as compared to the previous ones (1972–2009), we exposed winter and summer phytoplankton communities (using microcosms) to solar radiation, simulating two rainfall conditions - a single extreme vs. intermittent i.e., with gradual inputs, and we assessed their photosynthetic and growth rates responses and taxonomic changes. Rainfall scenarios significantly increased growth of both communities, mainly of small nanoplanktonic species, as compared to the control. Small nanoplanktonic centric diatoms increased and dominated in both rainfall scenarios, as compared to the control, during winter and summer, with significantly smaller cells during summer as compared to winter. Photosynthetic efficiency increased in both rainfall scenarios at the end of the experiment as compared to the control. Overall, the change towards small cells (associated to rainfall events) that can use more effectively solar radiation and nutrients (as compared to large cells) may have a significant impact on the trophic webs of the South West Atlantic Ocean by favoring grazing pressure by microzooplankton, especially during summer.

Long-term changes in summer phytoplankton communities and their influencing factors in Daya Bay, China (1991–2017)

Spatial variations in summertime phytoplankton community structure from 1991 to 2017 in Daya Bay, China were investigated in this research. The abundance of total phytoplankton and diatoms significantly increased during the study period in all regions of the bay while an increase in dinoflagellates abundance was only significant in the inner and middle bay areas. Pseudo-nitzschia spp. were overwhelmingly dominant followed by Skeletonema costatum. Ceratium furca was the dominant dinoflagellate. Overall, species diversity and evenness indices showed downward trends during the study period. Moreover, the bloom frequency of Scrippsiella trochoidea (associated with red tides) has increased rapidly since the 2000s in the inner bay. These temporal dynamics are largely explained by enhanced dissolved inorganic nitrogen (DIN) concentrations, which increased by 64.58% during 2005–2017 relative to 1991–2004, induced by human activities, along with temperature reductions and salinity increases resulting from open oceanic seawater intrusion.

Short timeframe changes of environmental impacts on summer phytoplankton in the Chukchi Sea and surrounding areas in a regional scaling

Recent changes observed in the Arctic associated with climate change call for further studies of its habitats and ecosystems, including those of the microbial communities that are the base of the food web. Limited information is available on short timeframe changes of summer phytoplankton and its driving factors. In the present study, space and time resolution in the phytoplankton community (>10 μm) and chlorophyll a (Chl a) were analyzed in Chukchi shelf and northern deep-sea areas (66°N ~ 80°N) during the Fourth Chinese National Arctic Research Expedition in the summer of 2010. Potential environmental drivers were linked to assess effects of Pacific inflow, light intensity and seasonal ice retreat on summer phytoplankton community. Results indicate a strong temporal variability in species composition, abundance and Chl a within a short interval (July 20 to August 30), as well as significant difference in regional distribution (Chukchi shelf, coast Alaska and deep-sea). A total of 159 taxa belonging to 69 genera from 9 phyla were identified by Utermöhl method. The Chukchi shelf in early summer (July 20 to 25) had a depth-integrated Chl a of 97.24 mg/m2 with a depth-averaged abundance of 101.37 × 103 cells/L. The community was dominated by Navicula pelagica, Thalassiosira nordenskiöeldii, Pseudonitzschia seriata, Leptocylindrus danicus, Nitzschia longissimi and Navicula vanhoeffenii. An ongoing ice-edge diatom bloom was observed associated to Anadyr Water. In contrast, from the deep-sea to Chukchi shelf in late summer (August 23 to 30), depth-integrated Chl a and depth-averaged abundance were lower than the previous weeks with only 25.31 mg/m2 plus 2.10 × 103 cells/L in deep-sea and 71.37 mg/m2 plus 27.00 × 103 cells/L in Chukchi shelf, respectively. At this stage, dominant species now include Thalassionema nitzschioides, Chaetoceros spp., Cylindrotheca closterium, Nitzchia longissima in deep-sea and Chaetoceros diadema, Letocylindrus danicus, N. longissima, Navicula pelagica, C. closterium, T. nitzschioides in Chukchi shelf, respectively. Generally, both Chl a and abundance were higher in the Chukchi shelf than those in the deep-sea, but was also higher in July than in August. Deep chlorophyll maxima was exclusively fixed at around 50 m in deep-sea, while a peak in Chl a appeared randomly at each layer in Chukchi shelf. A succession from pennate to centric diatoms was observed in northern Chukchi shelf closely related to ice retreat, while the opposite trend was common in the ice-free southern Chukchi shelf. Revisited stations in Chukchi shelf demonstrated the decrease in light intensity from July to August chiefly resulted in the reduction in Chl a and abundance during the return leg, while nutrients from Pacific inflows played a main role during the inbound leg.

Limited evidence for common interannual trends in Baltic Sea summer phytoplankton biomass.

The Baltic Sea summer phytoplankton community plays an important role in biogeochemical cycling and in the transfer of energy through the food web via zooplankton. We aimed to improve the understanding of the degree to which large-scale versus local environmental dynamics regulate phytoplankton dynamics by analyzing time series at the Baltic Sea scale. We used dynamic factor analysis to study if there are common patterns of interannual variation that are shared (“common trends”) among summer phytoplankton total and class-level biomass time series observed across Baltic Sea latitudinal gradients in salinity and temperature. We evaluated alternative hypotheses regarding common trends among summer phytoplankton biomass: Baltic Sea-wide common trends; common trends by geography (latitude and basin); common trends differing among functional groups (phytoplankton classes); or common trends driven by both geography and functional group. Our results indicated little support for a common trend in total summer phytoplankton biomass. At a finer resolution, classes had common trends that were most closely associated with the cryptophyte and cyanobacteria time series with patterns that differed between northern and southern sampling stations. These common trends were also very sensitive to two anomalous years (1990, 2008) of cryptophyte biomass. The Baltic Sea Index, a regional climate index, was correlated with two common class trends that shifted in mean state around the mid-1990s. The limited coherence in phytoplankton biomass variation over time despite known, large-scale, ecosystem shifts suggests that stochastic dynamics at local scales limits the ability to observe common trends at the scale of monitoring data collection.

Structural changes of the microplankton community following a pulse of inorganic nitrogen in a eutrophic river

AbstractGlobal change will increase the number and severity of extreme events resulting in strongly pulsed nutrient loading to rivers. Recent studies indicate the potential for rapid plankton shifts as short‐term response to storm events and highlight the need for high‐frequency methods to understand these complex processes. Here, we studied the effects of a strong short‐term pulse of ammonium nitrate in a eutrophic temperate river that elevated nitrate‐N concentrations from 3.1 to 10–55 mg L−1. An intense phytoplankton bloom increased chlorophyll a concentrations from below 10 μg L−1 to over 140 μg L−1 despite of high background N concentrations and followed the N‐pulse downstream. High‐throughput sequencing revealed the temporal dynamics of the bacterial (16S rRNA gene) and microeukaryotic (18S rRNA gene) community throughout the event. Bacterial and microeukaryotic community richness was reduced, and community composition changed significantly during the bloom. Few microeukaryote taxa (e.g., Cyclotella meneghiniana, Chlamydomonas) dominated the bloom and replaced the rich summer phytoplankton community. Long‐term monitoring data (2008–2016) using classical microscope analyses showed that seasonal shifts in phytoplankton community composition were linked to physical parameters and nutrient availability with P‐limitation observed in spring but not in summer. We conclude that a disturbance in abiotic and biotic control factors, such as caused by a nutrient pulse, can induce structural shifts in the microplankton community leading to a phytoplankton bloom, even in eutrophic waters.

Impact of ocean acidification and high solar radiation on productivity and species composition of a late summer phytoplankton community of the coastal Western Antarctic Peninsula

AbstractThe Western Antarctic Peninsula (WAP), one of the most productive regions of the Southern Ocean, is currently undergoing rapid environmental changes such as ocean acidification (OA) and increased daily irradiances from enhanced surface‐water stratification. To assess the potential for future biological CO2 sequestration of this region, we incubated a natural phytoplankton assemblage from Ryder Bay, WAP, under a range of pCO2 levels (180 μatm, 450 μatm, and 1000 μatm) combined with either moderate or high natural solar radiation (MSR: 124 μmol photons m−2 s−1 and HSR: 435 μmol photons m−2 s−1, respectively). The initial and final phytoplankton communities were numerically dominated by the prymnesiophyte Phaeocystis antarctica, with the single cells initially being predominant and solitary and colonial cells reaching similar high abundances by the end. Only when communities were grown under ambient pCO2 in conjunction with HSR did the small diatom Fragilariopsis pseudonana outcompete P. antarctica at the end of the experiment. Such positive light‐dependent growth response of the diatom was, however, dampened by OA. These changes in community composition were caused by an enhanced photosensitivity of diatoms, especially F. pseudonana, under OA and HSR, reducing thereby their competitiveness toward P. antarctica. Moreover, community primary production (PP) of all treatments yielded similar high rates at the start and the end of the experiment, but with the main contributors shifting from initially large to small cells toward the end. Even though community PP of Ryder Bay phytoplankton was insensitive to the changes in light and CO2 availability, the observed size‐dependent shift in productivity could, however, weaken the biological CO2 sequestration potential of this region in the future.

Composition and settling properties of suspended particulate matter in estuaries of the Chesapeake Bay and Baltic Sea regions

Our goal was to understand how differences in source material (allochthonous vs. autochthonous) and phytoplankton communities (diatoms vs. cyanobacteria) influence composition and settling properties of suspended particulate matter. We characterized the composition and settling properties of suspended particulate matter in two systems—one which has a high hydrologic loading factor (watershed to surface area ratio), and a diatom-dominated phytoplankton community (James River Estuary, USA), and a second, where hydrologic inputs are proportionally smaller, and the summer phytoplankton community is dominated by cyanobacteria (Curonian Lagoon, Lithuania). In the James, we found that TSS concentrations were positively related to discharge, whereas POC concentrations were negatively correlated with discharge and positively correlated with Chl-a. We infer that suspended particulate matter in this system was largely derived from allochthonous inputs, but that the organic matter fraction was derived from autochthonous production. In the Curonian Lagoon, TSS concentrations were correlated with Chl-a, but not discharge, indicating that suspended particulate matter was largely of autochthonous origin. In the James, the proportion of settleable materials was greater during high TSS concentrations, indicating that high discharge events delivered heavier particulates. In the Curonian Lagoon, we observed a seasonal decline in settling rates associated with the shift from mixed (diatoms and chlorophytes) to cyanobacteria-dominated phytoplankton, which we attribute to the presence of positively buoyant cyanobacteria. We found that a comparative approach yielded useful insights regarding sources, composition, and settling properties of suspended particulate matter in two estuaries that differ in hydrologic loading and phytoplankton community composition. Our findings suggest that the presence of positively buoyant cyanobacteria favors export losses of particulate C, N, and P to marine waters over retention through sedimentation in transitional zones.

Nitrogen Limitation of the Summer Phytoplankton and Heterotrophic Prokaryote Communities in the Chukchi Sea

Major changes to Arctic marine ecosystems have resulted in longer growing seasons with increased phytoplankton production over larger areas. In the Chukchi Sea, the high productivity fuels intense benthic denitrification creating a nitrogen (N) deficit that is transported through the Arctic to the Atlantic Ocean, where it likely fuels nitrogen fixation. Given the rapid pace of environmental change and the potentially globally significant N deficit, we conducted experiments aimed at understanding phytoplankton and microbial N utilization in the Chukchi Sea. Ship-board experiments tested the effect of NO3- additions on both phytoplankton and heterotrophic prokaryote abundance, community composition, photophysiology, carbon fixation and NO3- uptake rates. Results support the critical role of NO3- in limiting summer phytoplankton communities to small cells with low production rates. NO3- additions increased particulate concentrations, abundance of large diatoms, and rates of carbon fixation and NO3- uptake by cells >1 µm. Increases in the quantum yield and electron turnover rate of photosystem II in NO3- treatments suggested that phytoplankton in the ambient dissolved N environment were N starved and unable to build new, or repair damaged, reaction centers. While some increases in heterotrophic prokaryote abundance and production were noted with NO3- amendments, phytoplankton competition or grazers likely dampened these responses. Trends toward a warmer more stratified Chukchi Sea will likely enhance summer oligotrophic conditions and further N starve Chukchi Sea phytoplankton communities.

Interannual changes in summer phytoplankton community composition in relation to water mass variability in the East China Sea

The surface distribution of the phytoplankton community was investigated in July 2009, 2010, 2011, and 2013 on the mid-shelf of the East China Sea (ECS), which is under the influence of Changjiang River Diluted Water (CDW) and the Kuroshio Current. This study, based on a CHEMTAX analysis of phytoplankton pigments, revealed a predominance of cyanobacteria and prochlorophytes in the eastern ECS, which is perennially under the influence of oligotrophic Kuroshio Surface Water. Towards the west, on the mid-shelf of the ECS, the composition of the phytoplankton community varied from year to year. Diatoms dominated in 2009 and 2013, when dissolved inorganic phosphate (DIP) concentrations were higher than during 2010 and 2011. During the latter two years, characterized as high-nitrate years, a mixed population of cyanobacteria, chlorophytes, and other groups was observed. Cluster analysis based on the phytoplankton community composition together with a PCA of shipboard hydrographic and nutrient data for all four years helped to confirm that the summer phytoplankton community structure of the ECS was regulated by the mixing of water masses and the variability of nutrient ratios within the CDW as it moved offshore. Our results show that elevated DIP concentrations in the CDW favor the growth of diatoms and dinoflagellates. The primary pathway for DIP inputs appears to be the upwelling of high-phosphate subsurface waters along the coast of China.

Distribution of Phaeocystis antarctica-dominated sea ice algal communities and their potential to seed phytoplankton across the western Antarctic Peninsula in spring

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 586:91-112 (2018) - DOI: https://doi.org/10.3354/meps12367 Distribution of Phaeocystis antarctica-dominated sea ice algal communities and their potential to seed phytoplankton across the western Antarctic Peninsula in spring Virginia Selz1,*, Kate E. Lowry1, Kate M. Lewis1, Hannah L. Joy-Warren1, Willem van de Poll2, Sandip Nirmel1, Amy Tong1, Kevin R. Arrigo1 1Department of Earth System Science, Stanford University, Stanford, CA 94305, USA 2Department of Ocean Ecosystems, Energy and Sustainability Research Institute Groningen, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands *Corresponding author: vselz@stanford.edu ABSTRACT: The western Antarctic Peninsula has experienced extreme changes in the timing of sea ice melt and freeze up, shortening the duration of the seasonal sea ice cycle. While previous research demonstrated connections between multiple pelagic trophic levels and the physics of the sea ice, few studies have assessed the sea ice ecosystem or its linkage to the ocean ecosystem in this region. Through a field survey and shipboard experiments, our study focused on characterizing the spring ice algal bloom and elucidating its role in seeding phytoplankton communities post-ice melt in high and low light conditions. Field data revealed that algal communities in slush layers, often formed from the flooding of seawater (infiltration layers), dominated biomass distributions in the sea ice throughout the region, and showed distinct photophysiological characteristics from interior or bottom ice communities. Sea ice algal biomass reached 120 mg chl a m-2 and was often dominated by Phaeocystis antarctica. Shipboard growth experiments showed that prior light history (ice or water column), rather than community composition (phytoplankton and ice algae were composed of similar taxa), primarily drove physiological responses to high and low light. P. antarctica generally dominated the community in growth experiments at the end of the 6 d incubation period. Settling column experiments suggested that P. antarctica’s higher sinking rates relative to other taxa may explain its minor contributions to the summer phytoplankton community in single-cell form and its absence in colonial form, observed in the long-term ecological record of this region. KEY WORDS: Photophysiology · Diatoms · Ice-ocean coupling · Community composition Full text in pdf format PreviousNextCite this article as: Selz V, Lowry KE, Lewis KM, Joy-Warren HL and others (2018) Distribution of Phaeocystis antarctica-dominated sea ice algal communities and their potential to seed phytoplankton across the western Antarctic Peninsula in spring. Mar Ecol Prog Ser 586:91-112. https://doi.org/10.3354/meps12367 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 586. Online publication date: January 11, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Parallel assessment of marine autotrophic picoplankton using flow cytometry and chemotaxonomy

Autotrophic picoplankton (0.2–2μm) can be a significant contributor to primary production and hence play an important role in carbon flow. The phytoplankton community structure in the Baltic Sea is very region specific and the understanding of the composition and dynamics of pico-size phytoplankton is generally poor. The main objective of this study was to determine the contribution of picoeukaryotic algae and their taxonomic composition in late summer phytoplankton community of the West-Estonian Archipelago Sea. We found that about 20% of total chlorophyll a (Chl a) in this area belongs to autotrophic picoplankton. With increasing total Chl a, the Chl a of autotrophic picoplankton increased while its contribution in total Chl a decreased. Picoeukaryotes play an important role in the coastal area of the Baltic Sea where they constituted around 50% of the total autotrophic picoplankton biomass. The most abundant groups of picoeukaryotic algae were cryptophytes (16%), chlorophytes (13%) and diatoms (9%). Picocyanobacteria were clearly dominated by phycoerythrin containing Synechococcus. The parallel use of different assessment methods (CHEMTAX and flow cytometry) revealed the share of eukaryotic and prokaryotic part of autotrophic picoplankton.