Phytoplankton Community Abundance Research Articles

Spatial and Temporal Variability in Water Quality and Phytoplankton Community Composition in Charleston Harbor

The Charleston Harbor estuary is a dynamic ecosystem draining three rivers that surround the rapidly urbanizing greater Charleston area. Projected climate change impacts include elevated sea surface temperature and local changes in water quality that will likely alter biogeochemical cycling as well as phytoplankton abundance and community composition. Partnering with the local non-profit organization Charleston Waterkeeper, surface water samples were collected from late April through October 2021 at 20 sites in the Charleston Harbor estuary system. Water quality parameters measured included sea surface temperature (SST), salinity, pH, dissolved inorganic carbon, chromophoric dissolved organic matter (CDOM), phytoplankton pigments and nitrate and phosphate concentrations. Relatively high (6—16 μM) nitrate values were observed throughout the year and the nitrate to phosphate (N:P) ratios were consistently elevated (50—200) relative to the Redfield ratio of 16. Analysis of variance indicated that the delivery of nitrate, phosphate, and CDOM into the estuary came from upriver of the Charleston Harbor. For instance, CDOM was significantly impacted by tidal stage (p < 0.05) and was negatively correlated with salinity at low salinity sites, but no correlation was observed at high salinity sites. Seasonal patterns in phytoplankton community abundance and composition were driven by changes in SST, as overall phytoplankton biomass increased with a community shift from diatoms during colder months to flagellated cells such as prasinophytes during the warmer summer months. Phytoplankton diversity was greatest during the early summer and lowest in October. This study provides a reference baseline for water quality parameters and phytoplankton community composition in an estuarine ecosystem that is changing rapidly due to dredging and climate change processes.

Cell size-dependent species sensitivity to nanoparticles underlies changes in phytoplankton diversity and productivity.

Nanoparticle pollution has been shown to affect various organisms. However, the effects of nanoparticles on species interactions, and the role of species traits, such as body size, in modulating these effects, are not well-understood. We addressed this issue using competing freshwater phytoplankton species exposed to copper oxide nanoparticles. Increasing nanoparticle concentration resulted in decreased phytoplankton species growth rates and community productivity (both abundance and biomass). Importantly, we consistently found that nanoparticles had greater negative effects on species with smaller cell sizes, such that nanoparticle pollution weakened the competitive dominance of smaller species and promoted species diversity. Moreover, nanoparticles reduced the growth rate differences and competitive ability differences of competing species, while having little effect on species niche differences. Consequently, nanoparticle pollution reduced the selection effect on phytoplankton community abundance, but increased the selection effect on community biomass. Our results suggest cell size as a key functional trait to consider when predicting phytoplankton community structure and ecosystem functioning in the face of increasing nanopollution.

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.

The effects of nutrient loading from different sources on eutrophication in a large shallow lake in Southeast China.

Lake water eutrophication has become one of the leading obstacles to sustainable economic development in China. Research on the effects of mainstream currents on reservoirs has been relatively underdeveloped compared with research on tributaries, though changes in the water-sediment transport regime in a downstream river may affect nutrient transport behavior in a lake connected to that river. This is particularly problematic because certain wastewater sources, including runoff from agricultural wastes and industrial discharges, adversely affect lake water. Our study focused on Sanshiliujiao Lake, a significant drinking water source in Fujian, Southeast China, that has suffered considerably from eutrophication over the past few decades. This study aimed to estimate the phosphorus and nitrogen loads to the lake, exploring their sources and their ecologic effects using in situ observation and the export coefficient model. Our results showed that the pollution loads of total phosphorus (TP) and total nitrogen (TN) were 2.390 and 46.040 t/year, respectively, most of which were derived from the water diversion (TP 45.7%, TN 29.2%) and non-point source (TP 30.2%, TN 41.6%). The TN input was the highest in East river (3.557kg/d), followed by Red river (2.524kg/d). During the wet season, the input of TP and TN increased by 14.6 and 18.7 times, respectively, but produced only slight variations in concentration. Water diversion enriched the nutrients inputs and altered the structure and abundance of phytoplankton communities. In addition, when water flows from the main river directly to Sanshiliujiao Lake, algal blooms in river-connected lakes are significantly exacerbated, so our study may also serve as a theoretical basis to regulate eutrophication in Sanshiliujiao Lake.

Dynamics of phytoplankton in the coastal waters at Vladivostok in 2019–2021

Structure and abundance of phytoplankton community in the Sportivnaya Harbour and Paris Bay in Vladivostok (western coast of the Japan Sea) was monitored from October 2019 to December 2021. In total, 130 and 144 phytoplankton taxa were identified in these two areas, respectively. The overall cell abundance ranged from 1.3 · 103 to 19 · 106 cells/L (on average 21 · 104 and 84.5 · 104 cells/L); the total phytoplankton biomass — from 3.0 mg/m 3 to 38.5 g/m 3 (on average 0.8 and 2.6 g/m 3 , respectively, by areas). The long-term observations were made for the first time in the Sportivnaya Harbour. The community composition was typical of eutrophic waters, with usual seasonal succession in the Paris Bay but frequent blooms in the Sportivnaya Harbour, when diatoms were replaced by flagellates and filamentous cyanobacteria. Such dynamics is presumably caused by anthropogenic eutrophication due to uncontrolled wastewater discharge.

Exploring the key factors affecting the seasonal variation of phytoplankton in the coastal Yellow Sea

Marine phytoplankton play crucial roles in the ocean’s biological pump and have great impacts on global biogeochemical cycles, yet the knowledge of environmental variables controlling their seasonal dynamics needs to be improved further, especially in the coastal ecosystems. In order to explore the determinants affecting the seasonal variation of phytoplankton, here we conducted three surveys during spring, summer and autumn along the coastal Yellow Sea. Among the phytoplankton community, 49 species of diatoms and 9 species of dinoflagellates were observed in spring, 63 species of diatoms and 10 species of dinoflagellates in summer, and 62 species of diatoms and 11 species of dinoflagellates in autumn. These results thus suggested that there were obvious differences in the number of species across the three seasons, of which diatoms were the most diverse group, followed by dinoflagellates. Additionally, diatoms were the most dominant species of the phytoplankton community and varied largely during different seasons. According to the redundancy analysis, the abundance of phytoplankton community was mainly related to water temperature and dissolved inorganic nitrogen (DIN) during the three seasons, indicating that water temperature and DIN could be the key factors controlling the seasonal variability of phytoplankton community along the coastal Yellow Sea. Also, significant correlations were observed between phytoplankton abundance and heavy metals Zn, As, and Hg during the three seasons, suggesting that these metals also had potential influences on the seasonal dynamics of phytoplankton community in the coastal Yellow Sea.

Dissolved iron cycling in the Arabian Sea and sub-tropical gyre region of the Indian Ocean

Understanding the sources and biogeochemical processes influencing the dissolved iron (DFe) distribution is crucial because of its coupled role in C- and N-fixation in the oceans. Vertical depth profiles of DFe in the northwestern Indian Ocean along two meridional transects (∼65 °E and ∼57 °E) during spring and fall seasons are presented here under the GEOTRACES-INDIA initiative. The DFe in the surface waters exhibited both spatial and seasonal variabilities; N-S gradient with higher values in the north; and notably higher concentrations in the fall season. The photic zone-integrated DFe (57.5 ± 13.4 µmol m−2) was double in the Arabian Sea compared to the subtropical Indian Ocean (31.81 ± 7.63 µmol m−2) with a significant positive correlation with the photic zone integrated primary production. This suggests higher availability of DFe is responsible for high primary production in the Arabian Sea compared to the subtropical Indian Ocean. Lateral and vertical advection along with particle dissolution from the atmospheric dust fluxes and scavenging-adsorption processes could play prominent role in controlling photic DFe concentrations in the Arabian Sea. The continental margin sources, redox chemistry, and remineralization are responsible for the observed high DFe concentration within the intense oxygen minimum zone. The in-situ remineralization ratios of Fe to C in the Arabian Sea are higher than any other region of the Indian Ocean. It could be due to the high uptake of Fe during primary production in the Arabian Sea, despite huge spatio-temporal variations in the abundance of phytoplankton communities. Our DFe data from the undersampled region over the Carlsberg Ridge suggests the presence of chronic/event plumes contributing to the DFe inventory in the western Arabian Sea region.We have approximated the geochemical budget of Fe in the top 100 m for open ocean waters of the Arabian Sea. These preliminary estimates suggest that lateral and vertical fluxes for DFe are prominent in the region compared to soluble atmospheric Fe dust fluxes and these sources are balanced by the biotic and abiotic removal processes in the region. Based on these estimated fluxes, the calculated residence time of DFe varies from ∼0.1 to 1 year in photic waters of the Arabian Sea. Our results highlight the intrusion of Fe-deficit Southern Ocean waters in the Arabian Sea and the upwelling of Fe-starved deep waters alongside the northwest of the Murray Ridge are likely responsible for Fe limitation in the region.

Abundance and composition of phytoplankton communities in middle stream of Citanduy river, West Java

The relationship between phytoplankton composition and environmental conditions in their habitat provides an important role for their as an assessment of the status and quality of river waters and the management of these waters. The aim of this research was studied of composition and abundance of phytoplankton communities in Citanduy River, particularly in middle stream. The study has conducted in April, July, and October 2018. The study location consists of 4 stations. The research has measured the abundance index, diversity index, and dominance index of plankton. The physic-chemical waters parameters which was measured consist of temperature, pH, DO, depth, transparency, nitrite, ammoniac, nitrate, total phosphate, and chlorophyll-a. Phytoplankton of Citanduy River consists of 4 classes. The abundance index of phytoplankton was around 2,578-7,366 cells/L; diversity index of phytoplankton is around 0.48-2.57, while the highest dominance index was Pediastrum sp with 0.56. Based on multiple regression analysis, the abundance of phytoplankton in April was influenced by nitrates and temperature. The abundance of phytoplankton in July is influenced by nitrite and ammonia. Meanwhile, in October, phosphate and oxygen parameters affect the abundance of phytoplankton. The Citanduy River is still in the stable category because the water quality is still in a sufficient condition for aquatic biota, especially phytoplankton. The ammonium and total phosphate of BBWS station in October were higher than standard. The high concentration of nitrogen and phosphorus nutrients is the results from the surrounding land for rice fields, plantations, fish farming, and waste disposal.

Large-scale testing of phytoplankton diversity indices for environmental assessment in Mediterranean sub-regions (Adriatic, Ionian and Aegean Seas)

According to the methodological standards established by Marine Strategy Framework Directive, the assessment for the pelagic habitat under the Biodiversity Descriptor should be carried out at the regional or sub-regional level. In the case of Mediterranean Sea, the sub-regional assessment seems optimal to take into account biogeographic differences in species composition and functional characteristics. Previous research has shown that phytoplankton diversity indicators are efficient for reliable environmental assessments, although more effort has been recommended to test these indicators on a wide spatial scale to cover wider gradients of natural and anthropogenic pressures. In this work, a set of eight diversity indices was tested against the pressure levels within a common data set of the structure and abundance of phytoplankton communities from the Adriatic, Ionian and Aegean Seas. Expert knowledge was used to define four categories of impacts that take into account partial pressures, such as point and non-point pollution, industry, ports and fisheries. At the level of the common data set, most of the diversity, evenness and dominance indices could only distinguish between the highest level of impact and the rest of impact categories. These indices maintained the distinction between two levels of subsequently dichotomised impacts (no to low impact vs. high impact) across latitudinal and longitudinal gradients. On average, the indices were less sensitive to impacts in the northernmost and westernmost areas than in the southernmost and easternmost areas, although they still showed a significant response. The results also suggest that phytoplankton communities become more uniform and less dominated by a single taxon as sampling depth increases at sites with low impact, while evenness and dominance at impacted sites remain similar at all depths. In order to establish meaningful definitions of good environmental status and targets for pelagic habitats in the Mediterranean Sea, it is necessary to establish spatially specific thresholds by additional examination of indices of good performance.

Impact of the Water–Sediment Regulation Scheme on the phytoplankton community in the Yellow River estuary

The Water–Sediment Regulation Scheme (WSRS) transports large amounts of water, sediment, and nutrients to the Yellow River estuary (YRE) in a very short time, which significantly changes the ecological environment of the estuary area in summer (wet season). The influence of these changes on the distribution and abundance of phytoplankton communities in the YRE are still inadequately understood. We studied the spatial distribution of environmental factors, zooplankton abundance and biomass, and phytoplankton abundance and community in the YRE at different WSRS stages during 2018 (WSRS year) and compared with corresponding durations in 2017 (non–WSRS year). Our results demonstrate that the WSRS (1) promoted phytoplankton growth in estuarine areas at the pre-stage and decreased phytoplankton abundances in the entire study area during the inter-stage, (2) decreased phytoplankton biodiversity and increased abundance and proportion of Synedra sp., and (3) led to a temporary rapid increase in zooplankton abundance and biomass. Bottom–up effects dominated phytoplankton variability at the pre- and end-stages of the WSRS, while top–down effects dominated the inter-stage. Redundancy analysis indicated that phytoplankton assemblages were primarily influenced by nitrate and the ratio of nitrogen to phosphorus at the pre-stage, by zooplankton abundance and biomass at the inter-stage, and by ammonium and dissolved silica at the end-stage. Our findings provide essential information for understanding and predicting the changes in the phytoplankton community due to increases in hydrodynamics, nutrients, and turbidity conditions in river estuaries.

Global Warming Impacts Micro-Phytoplankton at a Long-Term Pacific Ocean Coastal Station

Understanding impacts of global warming on phytoplankton – the foundation of marine ecosystems – is critical to predicting changes in future biodiversity, ocean productivity, and ultimately fisheries production. Using phytoplankton community abundance and environmental data that span ~90 years (1931-2019) from a long-term Pacific Ocean coastal station off Sydney, Australia, we examined the response of the phytoplankton community to long-term ocean warming using the Community Temperature Index, an index of the preferred temperature of a community. With warming of ~1.8℃ at the site since 1931, we found a significant increase in the community temperature index from 1931-1932 to 2009-2019, suggesting that the relative proportion of warm-water to cold-water species has increased. The Community Temperature Index also showed a clear seasonal cycle, with highest values at the end of austral summer (Feb/Mar) and lowest at the end of winter (Aug/Sept), a pattern well supported by other studies at this location. The shift in CTI was a consequence of the decline in the relative abundance of the cool-affinity (optimal temperature = 18.7℃), chain-forming diatom Asterionellopsis glacialis (40% in 1931-1932 to 13% in 2009 onwards), and a substantial increase in the warm-affinity (21.5℃), also chain-forming diatom Leptocylindrus danicus (20% in 1931-1932 to 57% in 2009 onwards). L. danicus reproduces rapidly, forms resting spores under nutrient depletion, and displays a wide thermal range. Species such as L. danicus may provide a glimpse of the functional traits necessary to be a ‘winner’ under climate change.

Short Communication: Community of phytoplankton in peatland canal, Riau, and wet dune slacks of Parangtritis, Yogyakarta, Indonesia

Abstract. Mawarni A, Azizah FNN, Sartika HW, Hadisusanto S, Putri DM, Reza A. 2020. Short Communication: Community of Phytoplankton in peatland canal, Riau, and wet dune slacks of Parangtritis, Yogyakarta, Indonesia. Biodiversitas 21: 1874-1879. The ecosystems of peatland canal and wet dune slacks have specific characteristics for phytoplankton community. This study aimed to elaborate on the distribution and abundance of phytoplankton community in peatland canal of Sungai Tohor Village, Meranti Islands, Riau and wet dune slacks of Parangtritis, Special Region of Yogyakarta. Phytoplankton was collected using a 2-L modified Van Dorn water sampler. In peatland, canal phytoplankton was sampled at 3 different locations, each with 5 repetitions. Meanwhile, in wet dune slacks, phytoplankton was sampled at 5 locations, each with 3 repetitions. Phytoplankton samples were filtered with Wisconsin plankton-net 120 mesh and fixed with 3 drops of formaldehyde 4%. The measured physical and chemical factors were air temperature, water temperature, dissolved oxygen, alkalinity, carbon dioxide, pH, depth, transparency, nitrate, sulfate, and phosphate concentration. The results showed that the distribution and abundance of phytoplankton community in wet dune slacks were greater than those of the peatland community. This research found 18 species of phytoplankton in peatland canal, dominated by Synedra acus and 116 species of phytoplankton in wet dune slacks, dominated by Cyclotella meneghiniana.

Enhanced dissolved lipid production as a response to the sea surface warming

Abstract The temperature increase in oceans reflects on marine ecosystem functioning and surely has consequences on the marine carbon cycle and carbon sequestration. In this study, we examined dissolved lipid, lipid classes and dissolved organic carbon (DOC) production in the northern Adriatic Sea, isolated diatom Chaetoceros pseudocurvisetus batch cultures grown in a wide temperature range (10–30 °C) and in contrasting nutrient regimes, phosphorus (P)-depleted and P-replete conditions. Additionally, lipids and DOC were analyzed in the northern Adriatic (NA) in two stations characterized with different P availability, occupied from February to August 2010 that covered a temperature range from 9.3 to 31.1 °C. To gain insight into factors governing lipid and lipid classes' production in the NA, apart from temperature (T), Chlorophyll a, phytoplankton community abundance and structure, nutrient concentrations were measured together with hydrographic parameters. We found enhanced accumulation of dissolved lipids, particulary glycolipids, with increasing T, especially during the highest in situ temperature. The effect of T on enhanced dissolved lipid release is much more pronounced under P-deplete conditions indicating that oligotrophic regions might be more vulnerable to T rise. Temperature between 25 and 30 °C is a threshold T range for C. pseudocurvisetus, at which a significant part of lipid production is directed toward the dissolved phase. Unlike monocultures, there are multiple factors influencing produced lipid composition, distribution and cycling in the NA that may counteract the T influence. The possible role of enhanced dissolved lipid concentration for carbon sequestration at elevated T is discussed. On the one hand, lipids are buoyant and do not sink, which enhances their retention at the surface layer. In addition, they are surface active, and therefore prone to adsorb on sinking particles, contributing to the C sequestration.

Обилие фитопланктонных сообществ Баренцева моря в первой половине вегетационного цикла 2013 года

Обилие фитопланктонных сообществ Баренцева моря в первой половине вегетационного цикла 2013 года

Phytoplankton community structure in relation to vertical stratification along a north‐south gradient in the Northeast Atlantic Ocean

AbstractClimate change is affecting the hydrodynamics of the world's oceans. How these changes will influence the productivity, distribution and abundance of phytoplankton communities is an urgent research question. Here we provide a unique high‐resolution mesoscale description of the phytoplankton community composition in relation to vertical mixing conditions and other key physicochemical parameters along a meridional section of the Northeast Atlantic Ocean. Phytoplankton, assessed by a combination of flow cytometry and pigment fingerprinting (HPLC‐CHEMTAX), and physicochemical data were collected from the top 250 m water column during the spring of 2011 and summer of 2009. Multivariate analysis identified water column stratification (based on 100 m depth‐integrated Brunt–Väisälä frequency N2) as one of the key drivers for the distribution and separation of different phytoplankton taxa and size classes. Our results demonstrate that increased stratification (1) broadened the geographic range of Prochlorococcus as oligotrophic areas expanded northward, (2) increased the contribution of picoeukaryotic phytoplankton to total autotrophic organic carbon (< 20 μm), and (3) decreased the abundances of diatoms and cryptophytes. We discuss the implications of our findings for the classification of phytoplankton functional types in biogeochemical and ecological ocean models. As phytoplankton taxonomic composition and size affects productivity, biogeochemical cycling, ocean carbon storage and marine food web dynamics, the results provide essential information for models aimed at predicting future states of the ocean.

Space-borne study of seasonal, multi-year, and decadal phytoplankton dynamics in the Bay of Biscay

Seasonal and inter-annual variations in phytoplankton community abundance in the Bay of Biscay are studied. Preliminarily processed by the National Aeronautics and Space Administration (NASA) to yield normalized water-leaving radiance and the top-of-the-atmosphere solar radiance, Sea-viewing Wide Field-of-View Sensor (SeaWiFS), Moderate Resolution Imaging Spectroradiometer (MODIS), and Coastal Zone Color Scanner (CZCS) data are further supplied to our dedicated retrieval algorithms to infer the sought for parameters. By applying the National Oceanic and Atmospheric Administration's (NOAA's) Advanced Very High Resolution Radiometer (AVHRR) data, the surface reflection coefficient in the only band in the visible spectrum is derived and employed for analysis. Decadal bridged time series of variations of diatom-dominated phytoplankton and green dinoflagellate Lepidodinium chlorophorum within the shelf zone and the coccolithophore Emiliania huxleyi in the pelagic area of the Bay are documented and analysed in terms of impacts of some biogeochemical and geophysical forcing factors. It is shown that in the shelf zone of the Bay, the diatom-dominated phytoplankton community variations are predominantly controlled by river discharge variations, by water column stratification conditions (forming in winter–early spring), and by wind action (resulting in such phenomena as up-wellings and sediment re-suspension). Satellite data indicate that while in river deltas and adjoining waters the L. chlorophorum blooming events occur annually, in the Iroise Sea and near the Bailiwick of Guernsey, they happen irregularly. It is thought that such an irregular pattern, possibly, arises from L. chlorophorum competing with other phytoplankton species for nutrients. E miliania huxleyi blooms are found to occur nearly every year in the northern part of the Bay, whereas in the central area, this phenomenon occurs very irregularly. Satellite data indicate that variations in the water chemistry (variations in the nitrogen : phosphorus ratio due to preceding blooms of diatoms), and the incident irradiance level (degree of cloudiness), are important factors controlling the occurrence of E. huxleyi blooming in the central part of the Bay. Covering a 30 year period, the bridged data from CZCS, AVHRR, SeaWiFS, and MODIS imply that climate change might be responsible for the observed increase in E. huxleyi blooming events in the Bay since 1979.

Phytoplankton community structure in autumn of Anxing Wetland, Heilongjiang Province

于2010年10月(秋季)对黑龙江省安兴湿地浮游植物群落组成、丰度及优势种进行分析.共设置9个采样点,经鉴定共有浮游植物146个分类单位,包括128种17变种1变型,隶属于6门8纲12目25科45属,其中绿藻为优势门类,占浮游植物总数的39.7%,裸藻次之,占浮游植物总数的30.8%,硅藻居第三位,占浮游植物总数的21.9%,调查期间浮游植物的总丰度为181.4×10⁶ cells/L.优势度分析显示,安兴湿地秋季各采样点的浮游植物优势种都在3个以上,主要优势种有细粒囊裸藻(Trachelomonas granulosa Playf.)、梅尼小环藻(Cyclotella meneghiniana Kütz.)、细粒囊裸藻齿领变种(Trachelomonas granulosa var. crenulatocollis(Szab.) Hub.-Pest.)等.样点聚类和非度量多维标度分析表明,9个采样点浮游植物群落在相似度60%时可分为5组,各样点浮游植物种类在空间组成上相似性低,差异性较大,主要与其生境特点相关.典范对应分析显示优势种类变化与环境条件相一致,主要受温度、pH的影响.此外,在安兴湿地内还鉴定出大量的β-中污带指示种,结合多样性指数分析,本文初步推断安兴湿地水质可能受到了一定的污染.;This paper is about the structure of phytoplankton communities in the autumn of 2010 in Anxing Wetland, Heilongjiang Province, China. The abundance of phytoplankton communities, cell density and dominant species were analyzed. In total, 146 taxa were identified from nine sampling sites. The 146 taxa included 6 divisions, 8 classes, 12 orders, 25 families, 45 genera, 128 species, 17 varieties and 1 form. Chlorophyta were dominant and accounted for 39.7% of the total phytoplankton, while Euglenophyta and Bacillariophyta accounted for 30.8% and 21.9%, respectively. The abundance of phytoplankton was 181.4×10⁶ cells/L. Dominance analysis showed that there were more than three dominant species at each sampling site, including Trachelomonas granulosa Playf., Cyclotella meneghiniana Kütz. and Trachelomonas granulosa var. crenulatocollis(Szab.) Hub. -Pest.. Cluster and non-metric Multi Dimensional Scaling analysis showed that nine sampling sites were divided into five groups and the composition of phytoplankton communities were significant different spatially when the similarity of the phytoplankton community reached to 60%. That was related to different ecological characteristics of each site. Canonical Correspondence Analysis showed that dominant specie change was mainly influenced by temperature and pH. In addition, a large number of β-mesosaprobic zone indicators and lower diversity index were monitored in Anxing Wetland, suggesting that the water quality from the wetlands might have been polluted.

Circadian variation of the phytoplankton community and its relationship to the species forming harmful algal blooms in the mouth of Sontecomapan coastal lagoon, Veracruz, Mexico

We determined the structure of the phytoplankton community along a circadian cycle and itsrelation to species Harmful Algae Species (HAB), at the mouth of the coastal lagoon, Sontecomapan Veracruz, during the 27th and 28th of October, 1999. Water samples were collected every two hours employing a van Dorn bottle, to measure temperature, salinity, pH, dissolved oxygen, the composition and abundance of phytoplanktoncommunity and reviewed the behavior of ebb and flow of tides. In order to describe the behavior of the community the following criteria were used: simple dominance index, the Shannon diversity (H ‘), the Pielou equity (J`) and a canonical correspondence analysis was applied to understand the relationship between the abundance ofphytoplankton species and environmental variables. The results showed a total of 179 taxa, 27 of which form HAB elsewhere. At 11:00 hours on October 27 and 28 maximum values of H ‘= 5.8, J`= 0.9 are reported, the minimum of H’= 3.79, J`= 0.6 at 15:00 and 23:00 hours on October 27. With simple dominance index it was determined that Fragilaria exigua, F. tenuicollis, F. ulna var. ulna, Prorocentrum gracile, and Scrippsiella trochoidea, were dominant in the circadian cycle. It should be noted that salinity was the environmental factorwhich most influenced the composition and abundance of phytoplankton community.

Long‐term phytoplankton community changes in a deep subalpine lake: responses to nutrient availability and climatic fluctuations

Summary1. In natural lakes, modifications in the species composition and abundance of phytoplankton communities may ultimately be responses to changes in nutrient availability and climatic fluctuations. Phytoplankton and associated environmental factors were collected at monthly intervals from the beginning of the 1990s to 2007 in the large subalpine Lake Garda (zmax = 350 m, V = 49 × 109 m3). In this study period, the lake showed a slight and continuous increase of total phosphorus (TP) in the water column, up to concentrations of 18–20 μg P L−1. This increase represented the last stage of a long‐term process of enrichment documented since the 1970s, when concentrations of TP were below or around 10 μg P L−1.2. At the community level, annual phytoplankton cycles underwent a unidirectional and slow shift mainly due to changes in the species more affected by the nutrient enrichment of the lake. After a first and long period of dominance by conjugatophytes (Mougeotia) and diatoms (Fragilaria), phytoplankton biomass in recent years was sustained by cyanobacteria (Planktothrix). Other important modifications in the development of phytoplankton were superimposed on this pattern due to the effects of annual climate fluctuations principally mediated by the deep mixing events at spring overturn and, secondarily, by temperature and thermal stability of the water column during the growing season.3. Interannual variations in the stability and temperature of the water column appeared to influence the development of a few subdominant flagellates (dinophytes and cryptophytes). Nevertheless, the major impact of climate on phytoplankton was indirect, and mediated through the effects of winter climatic conditions on deep mixing dynamics. Winter climatic fluctuations proved to be a key element in a linked chain of causal factors including cooling of hypolimnetic waters, deep vertical mixing and epilimnetic nutrient replenishment. The process of fertilisation was measurable both for TP and dissolved inorganic nitrogen, although only the first had a large effect, reinforcing the seasonal growth of a few dominant groups. The degree of nutrient replenishment further increased the spring development of large diatoms and the increase of Planktothrix in summer and autumn.4. Currently, changes in nutrient concentrations have the greatest effect on the phytoplankton community, while direct effects due to the interannual variations in the thermal regime are of secondary importance compared with the indirect effects mediated through deep water mixing and spring fertilisation. Overall, the results demonstrate that the consequences of climatic fluctuations and climate warming on phytoplankton communities need to be studied at different levels of complexity and integration, from the direct effects of temperature and thermal regime, to the indirect effects mediated by the physiographic characteristics of water bodies.

Dynamics and toxicity of Anabaena aphanizomenoides (Cyanobacteria) waterblooms in the shallow brackish Oued Mellah lake (Morocco)

The structure and abundance of phytoplankton communities were investigated during 1997 to 1999 in Oued Mellah, a shallow brackish and hypertrophic lake, with particular regard to Anabaena aphanizomenoides dynamics. Important events of algal blooms were observed mostly by the cyanobacteria Microcystis ichthyoblabe, Anabaena aphanizomenoides and Oscillatoria chlorina and by the ichthyotoxic haptophyceae Prymnesium parvum. Anabaena aphanizomenoides proliferated during late summer after the Microcystis ichthyoblabe blooms. The percentage of Anabaena aphanizomenoides of the phytoplankton biomass varied from 88 to 94 percent during bloom periods. Maximum biomass was 146 and 120 mg fresh weight l−1 during the 1997 and 1999 summer periods, respectively. The main environmental factors leading to the ecological success of A. aphanizomenoides were high temperature (25–28ˆC), high incident light intensities (1488–1912 μ E m−2 s−1, high nutrient deficiency (0 μ g P-PO−4 l−1; 0–0.18 mg N-NO3 l−1) and decrease of alkalinity (329–494 mg HCO3− l−1). The toxicity of the Anabaena aphanizomenoides bloom was evaluated by bioassays and analyses. The lethal dose50 of the bloom sample tested in mice was 254 mgDW kg−1 body weight while toxicity (24 h LC−50) in the brine shrimp Artemia salina was 3.68 mgDW ml−1. The low microcystin content (3.28 μ g gDW−1) determined by ELISA was not consistent with the tested bioassays and is suggestive of the presence of other toxic compounds in the bloom extracts. Four toxic fractions were separated by HPLC-PDA and identified as microcystins according to their UV spectra. The production of microcystins by Anabaena aphanizomenoides bloom was confirmed by the analysis of the isolated strain which, in Z8 medium under controlled laboratory conditions, produced three variants of microcystins, two of them being similar to those produced by the natural bloom.