Variations In Phytoplankton Assemblages Research Articles

Dynamics of molybdenum and barium in the Bay of Brest (France) explained by phytoplankton community structure and aggregation events

Primary producers are essential organisms for marine ecosystems because they form the basis of food webs, produce half of atmospheric oxygen and are involved in various biogeochemical cycles. At the end of a bloom event, phytoplankton cells are known to produce organic compounds that act as a ‘cement’, allowing the cells to stick together and form large sinking structures called aggregates. These aggregates are microenvironments with chemical properties that are very different from the surrounding water. The main objective of this study was to determine how the temporal variations in cell assemblages over time and the formation of aggregates following a bloom affect the concentrations of molybdenum (Mo) and barium (Ba) in the water column, which are elements typically measured within accretionary hard tissues (e.g., mollusc shells) to track phytoplankton dynamics in the environment. To do so, we performed an environmental monitoring from March to October 2021 at Lanvéoc in the Bay of Brest (France) during which several biological (e.g., variations in phytoplankton assemblages) and chemical (e.g., chemical properties of the water column) parameters were measured once to twice per week. Our results show that spring and summer blooms of Gymnodinium, known to be enriched in Mo, could be one of the reasons explaining the particulate Mo enrichments in the water column. In addition, large phytoplankton aggregates transported a significant amount of Mo to the seafloor and associated suspension feeders. In contrast, the temporal variations in dissolved and particulate Ba concentration were strongly influenced by the formation of diatom blooms. Interestingly, there was a significant shift in Ba from the dissolved to the particulate fraction during the largest diatom bloom in late spring, associated with a significant Ba transport to the seafloor, which may be explained by the adsorption of this element onto diatom frustules. This study therefore highlights the impacts of phytoplankton on the dynamics of these elements in coastal ecosystems.

CHEMTAX analysis of phytoplankton assemblages revealed potential indicators for blooms of haptophyte Phaeocystis globosa

Harmful algal blooms formed by the haptophyte Phaeocystis globosa have been recorded in the Beibu Gulf since 2011. In this study, the composition and variation of phytoplankton assemblages in the Beibu Gulf were studied during an intense bloom of P. globosa from 2016 to 2017, using the CHEMTAX approach. In phytoplankton samples collected from the Beibu Gulf, chlorophyll a (Chl a, 0.046–2.87 μg L−1) and fucoxanthin (Fuco, 0.041–13.7 μg L−1) were the most abundant pigments. Diatoms were the dominant group of phytoplankton, followed by cyanobacteria (mainly Synechococcus), haptophytes, cryptophytes, prasinophytes, dinoflagellates, and chlorophytes. Phytoplankton samples were clustered into four communities characterized by diatoms, cyanobacteria, haptophytes containing 19′-butanoyloxyfucoxanthin (the “Hapt-But” subgroup of haptophytes), and haptophytes containing 19'-hexanoyloxyfucoxanthin (the “Hapt-Hex” subgroup of haptophytes). Distribution pattern of the “Hapt-But” subgroup of haptophyte was consistent with that of P. globosa colonies. Diatoms had positive correlation with P. globosa colony abundance, while cyanobacteria had negative correlation. The diagnostic pigments for colony-forming P. globosa (But-fuco), diatoms (Fuco) and cyanobacteria (zeaxanthin), as well as temperature (<20 °C), could serve as potential early-warning indicators for the formation of P. globosa blooms in the Beibu Gulf.

Long-term variation in phytoplankton assemblages during urbanization: A comparative case study of Deep Bay and Mirs Bay, Hong Kong, China

A long-term dataset, including physicochemical, nutrient, and phytoplankton assemblages from 1994 to 2016, was analyzed to investigate the response of the algal community to variations in environmental factors in Deep Bay and Mirs Bay in southern China. These bays differ in their overall nutrient loadings, as well as in physical factors. The results showed that diatoms were numerically dominant in Mirs Bay, while other minor phytoplankton groups, including eutrophication-tolerant species, constituted the majority in Deep Bay. Phytoplankton community composition tended to be less complex in Deep Bay, suggesting a stressed, unstable and unbalanced ecosystem compared to that in Mirs Bay. Algal blooms occurred more frequently in Mirs Bay, whereas fewer but larger-scale blooms occurred in Deep Bay. Statistically, the combination of all explanatory variables accounted for approximately 55% of the variation in Chlorophyll-a (Chl-a) concentration and less than 20% of the total phytoplankton variation over the 23-year period in the two bays. The high level of nutrients caused by urbanization was not the driving force in the formation of blooms but presumably provided a nutrient base that resulted in blooms with longer durations and covering larger areas.

Phytoplankton in dryland riverine waterholes: environmental drivers, variability and ecosystem-monitoring potential using different levels of taxonomic resolution and dataset reduction

Waterholes that remain in the dry season in intermittent dryland rivers are important biotic refugia, but detailed ecological descriptions of these habitats and their plankton are scarce. We aimed to determine spatial and temporal variation in phytoplankton assemblages in a tropical Australian dryland river system, their main environmental determinants and the potential of the phytoplankton for ecosystem monitoring. We sampled nine sites in three rivers over 2 years using standard methods. Water quality and phytoplankton assemblages varied considerably among sites, rivers and seasons, reflecting lithology, hydrology, bathymetry and local catchment influences. Major environmental drivers included conductivity, pH, temperature and species of N and P. We analysed several derived versions of the original dataset by using density and presence–absence data, eliminating rarer species and grouping species into higher taxa. We found substantial consistency among analyses in environmental drivers, identified using distance-based linear modelling, and in variability among systems, identified using nested permutational multivariate analysis of variance (PERMANOVA). Responsiveness of the algal assemblages to environmental drivers and consistency among analyses, even using subsamples at low taxonomic resolution, suggests potential for ecosystem monitoring and optimising of sample throughput, although variability among systems requires substantial effort to determine the range of reference conditions.

Structural adaptions of phytoplankton assemblages along two contrasting reservoirs

Differences in limnological and hydrological conditions between storage and run-of-river reservoirs caused variations in phytoplankton assemblages along the two types of reservoirs. Instead of exploring variations in phytoplankton assemblages along one type of reservoir, this study identified similarities and differences in phytoplankton assemblages along two types of reservoirs. Phytoplankton assemblages from Xiaowan (storage reservoir) and Manwan (run-of-river reservoir) reservoirs in the Lancang River, China were used as case study. Taxonomic approach and functional group method were used to compare phytoplankton assemblages at sampling sites located in impounded areas of reservoirs, free-flowing areas directly below reservoirs, and free-flowing intermediate areas between the two contrasting reservoirs. With the reduction of reservoir disturbance, phytoplankton assemblages in free-flowing intermediate areas between reservoirs will recover to rich and diverse. Because of the inoculation and dispersion of phytoplankton from the upstream reservoir, dominant functional groups at the sampling sites located in impounded areas of reservoirs and free-flowing areas directly below reservoirs were mainly represented by groups that prefer long water residence times. The functional group TB (Nitzschia lorenziana) and W2 (Strombomonas ensifera) could be used as useful indicators to determine hydrological conditions due to their strong sensitivity to water residence times. Results of the linear redundancy analysis demonstrated that phytoplankton assemblages were mainly affected by DO and flow. These results should aid river managers in acquiring better insight into the effect of cascade reservoirs on the biomass and structure of phytoplankton in the aquatic ecosystem.

Response of phytoplankton assemblages to nitrogen reduction in the Laizhou Bay, China

The response of phytoplankton assemblages to decreases in nitrogen loading is an essential index to assess the recovery of aquatic ecosystems from eutrophic status. However, a positive signal is hard to observe from short-term operations considering ecosystem complexity. Here, we used decadal data from the Laizhou Bay, China to track the seasonal and annual variations in phytoplankton assemblages after ammonia reduction in the Xiaoqing and Yellow Rivers. Annual trends show reduced phytoplankton abundance and a decline in harmful algal blooms, indicating the positive recovery of phytoplankton assemblages. Phytoplankton assemblage in the sea region adjacent to the Xiaoqing River shows a lower H′ index, higher cell abundance, and higher seasonal variability than the sea region neighbouring the Yellow River. The spatial variability might result from the differences of nitrogen species, runoff and sediment contents between the two rivers; this finding indicates a demand for more aggressive decreases in nitrogen loads.

Oceanic fronts control the distribution of dissolved barium in the Southern Ocean

The globally-observed relationship between oceanic barium and the macronutrient silicic acid results from the shared influence of large-scale ocean circulation and mixing on the two elements, and the inherent link between barium and organic matter formation and dissolution. A detailed examination of deviations from barium-silicon correlations can reveal variations in non-conservative processes within the marine barium cycle. Here, we present a high-resolution dataset of dissolved barium and macronutrients from the Drake Passage and the Scotia and Weddell Seas. Our new results highlight the influence of Southern Ocean frontal zones on barium cycling and the deviations of barium and macronutrient distributions as a result of spatial variations in phytoplankton assemblages and in barite formation processes. These new data also reinforce findings that water mass mixing and ocean circulation, in particular the location of oxygen minima, play a key role in barium distribution. Our findings have implications for the use of sedimentary barium as a proxy for export production, which may be complicated by physical water circulation changes or shifts in plankton community structure. Corrigendum: https://doi.org/10.1016/j.marchem.2018.09.004

Contribution of benthic microalgae to the temporal variation in phytoplankton assemblages in a macrotidal system.

Suspended marine benthic microalgae in the water column reflect the close relationship between the benthic and pelagic components of coastal ecosystems. In this study, a 12-year phytoplankton time-series was used to investigate the contribution of benthic microalgae to the pelagic system at a site along the French-Atlantic coast. Furthermore, all taxa identified were allocated into different growth forms in order to study their seasonal patterns. The highest contribution of benthic microalgae was observed during the winter period, reaching up to 60% of the carbon biomass in the water column. The haptobenthic growth form showed the highest contribution in terms of biomass, dominant in the fall-winter period when the turbidity and the river flow were high. The epipelic growth form did not follow any seasonal pattern. The epiphytic diatom Licmophora was most commonly found during summer. As benthic microalgae were found in the water column throughout the year, the temporal variation detected in the structure of pelagic assemblages in a macrotidal ecosystem was partly derived from the differentiated contribution of several benthic growth forms.

Vertical and temporal variation in phytoplankton assemblages correlated with environmental conditions in the Mundaú reservoir, semi-arid northeastern Brazil.

The goal of this study was to analyse the vertical structure of the phytoplankton community at the Mundaú reservoir, located in the semi-arid region of northeastern Brazil, and to correlate it to environmental conditions over two distinct seasons, dry and rainy. Samples were collected bimonthly at eight depths in the dry and rainy season for analyses of the physical and chemical variables of the water, as well as density, abundance, dominance, species diversity index and equitability of the community. Analysis of variance (ANOVA-two way) was used to analyse the vertical and seasonal differences, and Canonical Correspondence Analysis (CCA) was used to assess associations between phytoplankton and environmental variables Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju was the only dominant species and Geitlerinema amphibium (C. Agardh) Anagnostidis, Merismopedia punctata Meyen and Synedra rumpens Kützing. Others six taxa were abundant in at least one of the samples. Distinct vertical distribution patterns were observed for the abundant taxa between depths and seasons. The cyanobacteria, with the exception of C. raciborskii, showed similar seasonal patterns, with higher densities in the dry season. The CCA showed a strong correlation between the density of the phytoplanktonic species and abiotic variables. The vertical changes in abundant taxa revealed distinct patterns regulated by the variation in the environmental factors that were directly linked to seasonality, with the success of one or more species being dependent on their life strategies and ecological needs. The present study restates the importance of environmental and seasonal factors for phytoplankton composition and distribution in a freshwater tropical reservoir through a vertical gradient.

Using Phytoplankton Diversity to Determine Wetland Resilience, One Year After a Vegetable Oil Spill

A 250 t sunflower oil spill in the Con Joubert Bird Sanctuary Wetland, South Africa, was the largest global sunflower oil spill in a freshwater wetland to date. Since there was insufficient historical data for the Con Joubert Bird Sanctuary Wetland prior to the spill, variations in phytoplankton assemblages were used to indicate wetland resilience in relationship with water quality variables. From this study, it was evident that the phytoplankton biodiversity was a more reliable indicator of wetland resilience than vegetable oil concentrations measured in the water column. Vegetable oil concentrations measured in the water column varied both spatially and temporally and can possibly be linked to the passive movement of drifting oil in the water column caused by wind action and temperature changes. While we were unable to pinpoint the exact mechanisms behind the increase in phytoplankton biodiversity, the response was probably driven by the degradation of the oil by natural microbial consortiums in the wetland or a possible increase in phytoplankton grazers. Certain phytoplankton genera were found to be tolerant to the adverse effects of the oil spill. These genera include Oedogonium, Cyclotella, Spirogyra, and Planktothrix. In general, the univariate and multivariate statistical analysis showed a low diversity and richness at sites 1, 2 and 3 during the initial sampling surveys when compared to the remaining sites. However, the phytoplankton diversity and richness subsequently increased at all sampling sites from the second sampling survey, implying that there was a shift in phytoplankton biodiversity to a more stable state.

Summer primary productivity and phytoplankton community composition driven by different hydrographic structures in the East/Japan Sea and the Western Subarctic Pacific

AbstractThe East/Japan Sea (EJS) is a highly productive marginal sea in the northwest Pacific, consisting of three basins (Ulleung Basin: UB, Yamato Basin: YB, and Japan Basin: JB). To find causes of the reportedly high primary productivity in summer in the EJS, especially in the UB, we measured primary productivity, phytoplankton composition, and other environmental variables. The water column was strongly stratified in the EJS compared with the Western Subarctic Pacific (WSP). Integrated primary productivity was two times higher in the EJS (612 mg C m−2 d−1) than in the WSP (291 mg C m−2 d−1). The vertical distributions of physicochemical and biological factors confirmed that production in the subsurface chlorophyll maximum layer in the study regions was an important factor regulating primary productivity within the water column. While picoplankton (&lt;2.7 µm) dominated in the WSP, JB, and YB, micro/nanoplankton (≥2.7 µm) dominated in the UB. Contribution by picoplankton to total biomass and primary productivity in the UB was significantly lower than in the other regions. CHEMTAX analysis using marker pigments showed that diverse phytoplankton groups inhabited the study regions. Cluster and canonical correspondence analyses showed high correlation between the spatial variation in phytoplankton assemblages with the water mass properties mainly represented by water temperature and nitrate concentration. Overall, our results suggest that the hydrographic structure of water column in the study region is an important controlling factor of the biomass and productivity of phytoplankton as well as their diversity in size and taxonomic groups.

Analysis of diversity of chromophytic phytoplankton in a mangrove ecosystem using rbcL gene sequencing.

Phytoplankton forms the basis of primary production in mangrove environments. The phylogeny and diversity based on the amplification and sequencing of rbcL, the large subunit encoding the key enzyme ribulose-1, 5-bisphosphate carboxylase/oxygenase was investigated for improved understanding of the community structure and temporal trends of chromophytic eukaryotic phytoplankton assemblages in Sundarbans, the world's largest continuous mangrove. Diatoms (Bacillariophyceae) were by far the most frequently detected group in clone libraries (485 out of 525 clones), consistent with their importance as a major bloom-forming group. Other major chromophytic algal groups including Cryptophyceae, Haptophyceae, Pelagophyceae, Eustigmatophyceae, and Raphidophyceae which are important component of the assemblages were detected for the first time from Sundarbans based on rbcL approach. Many of the sequences from Sundarbans rbcL clone libraries showed identity with key bloom forming diatom genera namely Thalassiosira, Skeletonema and Nitzschia. Similarly, several rbcL sequences which were diatom-like were also detected highlighting the need to explore diatom communities from the study area. Some of the rbcL sequences detected from Sundarbans were ubiquitous in distribution showing 100% identities with uncultured rbcL sequences targeted previously from the Gulf of Mexico and California upwelling system that are geographically separated from study area. Novel rbcL lineages were also detected highlighting the need to culture and sequence phytoplankton from the ecoregion. Principal component analysis revealed that nitrate is an important variable that is associated with observed variation in phytoplankton assemblages (operational taxonomic units). This study applied molecular tools to highlight the ecological significance of diatoms, in addition to other chromophytic algal groups in Sundarbans.

Variation of phytoplankton assemblages along the Mozambique coast as revealed by HPLC and microscopy

This study is an integrated overview of pigment and microscopic analysis of phytoplankton communities throughout the Mozambican coast. Collected samples revealed notable patterns of phytoplankton occurrence and distribution, with community structure changing between regions and sample depth. Pigment data showed Delagoa Bight, Sofala Bank and Angoche as the most productive regions throughout the sampled area. In general, micro-sized phytoplankton, particularly diatoms, were important contributors to biomass both at surface and sub-surface maximum (SSM) samples, although were almost absent in the northern stations. In contrast, nano- and pico-sized phytoplankton revealed opposing patterns. Picophytoplankton were most abundant at surface, as opposed to nanophytoplankton, which were more abundant at the SSM. Microphytoplankton were associated with cooler southern water masses, while picophytoplankton were related to warmer northern water masses. Nanophytoplankton were found to increase their contribution to biomass with increasing SSM. Microscopy information on the genera and species level revealed the diatoms Chaetoceros spp., Proboscia alata, Pseudo-nitzschia spp., Cylindrotheca closterium and Hemiaulus haukii as the most abundant taxa of the micro-sized phytoplankton. Discosphaera tubifera and Emiliania huxleyi were the most abundant coccolithophores, nano-sized phytoplankton.

Phytoplankton assemblages across the marine to low-salinity transition zone in a blackwater dominated estuary

Along the salinity gradient between the freshwater reach of the Suwannee River and the marine waters of the Gulf of Mexico, the spatial and temporal composition and abundance of phytoplankton was examined in relation to physical and chemical water-column variables (i.e. salinity, nutrient and light availability and temperature). The goal of this study was to explore the applicability of the concepts of ecotone and ecocline to the distribution of phytoplankton. This was undertaken in a relatively open estuary dominated by a tannin-colored river, the Suwannee River, along the central northwest coast of Florida, USA. Hierarchical cluster analysis and non-metric multidimensional scaling (MDS) was used to define biologically distinct regions within the estuary based on the composition of phytoplankton. Variations in phytoplankton assemblages in relation to environmental variables were investigated using a canonical correspondence analysis. The results indicate that in addition to the alignment of phytoplankton composition along a salinity gradient, several key environmental factors influence phytoplankton assemblages within hydrologically distinct regions of the estuary supporting an ecocline view. However, the distribution of dinoflagellate assemblages were in contrast to the more temporally fluid spatial distributions of cyanobacteria and diatoms in the Suwannee River estuary. The spatially defined nature of the dinoflagellate assemblages was more characteristic of an ecotone rather than an ecocline.

Temporal variation in phytoplankton assemblages and pigment composition at a fixed station of the Rı́a of Pontevedra (NW Spain)

Phytoplankton composition and abundance were studied at a fixed station (P2, Rı́a of Pontevedra, NW Spain) weekly during a 2-year period (1999–2000). In addition to microscopic cell counts, a chemotaxonomic approach based on HPLC pigment analysis and CHEMTAX data processing was studied on two size classes. The contribution of the picoplankton fraction to the total chlorophyll (chl) a averaged 13±10%. Pigment suites of the picoplankton fraction were mainly provided by picoeukaryotes. Chl b dominated in the picoplankton whereas chls c ( c 2, c 1 and c 3) were the major accessory chlorophylls in the micro-nanoplankton. Despite this, fucoxanthin was by far the most abundant carotenoid in both size classes (often >70% of total carotenoids). Major ‘pigment groups’ in the picoplankton were ‘prasinophytes’ (with prasinoxanthin and carotenoids of the uriolide series) and ‘chlorophytes’, which contributed up to 60% total chl a during winter. ‘Diatoms’ and ‘haptophytes’ were other relevant picoplanktonic groups along the seasonal cycle. Micro-nanoplankton was dominated by ‘diatoms I’ (chl c 1 and chl c 2) and ‘diatoms II’ (chl c 3 and chl c 2), which contributed up to 70% of total chl a in spring. Chl c composition during diatom blooms exhibited higher chl c 1:chl c 2 ratios in winter–spring and higher chl c 3:chl c 2 ratios in summer–autumn.

Controls on the carbon-isotope compositions of compounds in Peru surface waters

We sampled suspended organic matter from two east–west transects across the Peru upwelling region and determined the taxonomic and regional variability of the relationships between photosynthetic fractionation (ε p ) and environmental conditions for diatoms, dinoflagellates, and total photosynthate. We also examined controls on the δ 13C values of zooplankton-derived sterols and suspended particulate organic carbon (SPM). Ratios of chlorophyll- a (chl- a) to SPM suggest that light limited diatom growth rates along the northern transect, while nutrients apparently limited growth along the southern transect. In the southern transect, three different diatom-derived sterols exhibit similar ε p –growth rate relationships, consistent with previous results indicating that diatoms in Peru waters employ active transport of bicarbonate and were growth-limited by silicate. Phytol, largely synthesized by primary producers, and zooplanktonic sterols exhibited relationships similar to the diatom sterols, but correlation coefficients between their respective ε p values and environmental conditions were significantly lower. Values of ε p calculated from particulate organic carbon (POC) did not correlate with specific environmental variables, possibly due to the overprint of spatial variations in phytoplankton assemblages on δ 13C POC. These results suggest that the quality of environmental interpretation based upon carbon-isotopic composition decreases as particulate organic matter and target biomarkers become less taxon-specific due to contributions from multiple sources.

Day-to-day variation in phytoplankton assemblages during spring blooming in a fixed station along the Lebanese coastline

Day-to-day variation in phytoplankton assemblages during spring blooming in a fixed station along the Lebanese coastline