Seasonal Phytoplankton Dynamics Research Articles

Joint seasonal dynamics of phytoplankton and zooplankton in the sub-Arctic White Sea

The seasonal succession of phytoplankton species composition and biomass plays a pivotal role in driving the seasonal variations in zooplankton community structure and biomass. Our study focused on the seasonal dynamics of planktonic communities in the Chupa Inlet (Kandalaksha Bay, White Sea) to determine if there are distinct complexes of phyto- and mesozooplankton species associated with different seasons, and whether these complexes are interconnected. Four seasonal groups of phyto- and zooplankton samples were revealed, each characterized by a specific composition of typical species. The winter and spring groups of phytoplankton and zooplankton corresponded to each other in their temporal span. Later in the year, this temporal correspondence was disrupted as early copepodite stages of Calanus glacialis dominated the community briefly in late spring, forming the basis of a separate seasonal group. From July until the end of the study period, warmer-water species constituted the community core, shaping the summer-autumn seasonal group. The role of smaller species in both phyto- and zooplankton communities increased during summer and autumn. The size structure and motility of the phytoplankton were found to significantly influence the seasonal succession of the zooplankton. This apparently contributes to better trophic coupling between phyto- and zooplankton throughout the seasonal cycle.

Phytoplankton Dynamics and Biogeochemistry: Model Studies

The seasonal dynamics of the NE Black Sea phytoplankton follow the following pattern: small diatoms (spring) → coccolithophorid Emiliania huxleyi (late spring–early summer) → large diatoms (summer). Our hypothesis states that nitrogen and phosphorus concentrations regulate the seasonal phytoplankton dynamics. A minimum number of parameters is enough to understand the mechanisms of dominant species change. Based on the concept of intracellular regulation, the following parameters were evaluated: the minimum nitrogen and phosphorus quotas; half-saturation constants for nitrogen and phosphorus uptake; the maximum specific growth rate of the dominant phytoplankton species. Computational experiments on the model show the following: (1) in spring, a species with a high maximum specific growth rate becomes dominant; (2) in late spring and early summer, a species with a low minimum nitrogen quota and a low half-saturation constant for nitrogen uptake is observed; (3) in summer, a low minimum phosphorus quota and a low half-saturation constant for phosphorus uptake allow the species to become dominant.

Seasonal Dynamics of Phytoplankton in Integrated Paddy-cum-Fish Culture

Background: An experimental study was conducted during June-November 2020 at Tungjoy village of Manipur, India, to assess the assemblage pattern, abundance and seasonal dynamics of phytoplankton in simultaneously integrated paddy-cum-fish culture (IPFC). Methods: The experimental IPFC fields were prepared by enhancing width and height of dykes and constructing central refuge pond. Rice saplings were manually transplanted into the prepared fields in June 2020 while the common carp fingerlings were introduced 30 days after rice-transplantation. Both rice and fish were harvested in November 2020. Assemblage pattern, abundance and dynamics of phytoplankton, soil nutrients and water quality were analysed for three seasons (monsoon, post-monsoon and winter) in paddy fields without fish (PF) compared with IPFC fields. Relevant fish growth parameters were analysed on monthly basis. Result: The study recorded 37 genera of phytoplankton belonging to 25 families and 18 orders falling under class Bacillariophyceae, Chlorophyceae and Cyanophyceae. Bacillariophyceae was the most diverse class. Phytoplankton density ranges from 14.00±1.57 × 103 to 33.25±3.60 × 103 µL-1 and 9.05±2.27 × 103 to 33.06±3.45 × 103 µL-1 in PF and IPFC, respectively, wherein Chlorophyceae dominated during monsoon and post-monsoon. Phytoplankton in IPFC was lower than PF, indicating effective utilisation by the reared fish. Fish production from IPFC fields was 326 kg ha-1 with 83% survival rate while rice production was enhanced by 7.4% as compared to rice monoculture.

Sea-ice melt determines seasonal phytoplankton dynamics and delimits the habitat of temperate Atlantic taxa as the Arctic Ocean atlantifies.

The Arctic Ocean is one of the regions where anthropogenic environmental change is progressing most rapidly and drastically. The impact of rising temperatures and decreasing sea ice on Arctic marine microbial communities is yet not well understood. Microbes form the basis of food webs in the Arctic Ocean, providing energy for larger organisms. Previous studies have shown that Atlantic taxa associated with low light are robust to more polar conditions. We compared to which extent sea ice melt influences light-associated phytoplankton dynamics and biodiversity over two years at two mooring locations in the Fram Strait. One mooring is deployed in pure Atlantic water, and the second in the intermittently ice-covered Marginal Ice Zone. Time-series analysis of amplicon sequence variants abundance over a 2-year period, allowed us to identify communities of co-occurring taxa that exhibit similar patterns throughout the annual cycle. We then examined how alterations in environmental conditions affect the prevalence of species. During high abundance periods of diatoms, polar phytoplankton populations dominated, while temperate taxa were weakly represented. Furthermore, we found that polar pelagic and ice-associated taxa, such as Fragilariopsis cylindrus and Melosira arctica, were more common in Atlantic conditions, while temperate taxa, such as Odontella aurita and Proboscia alata, were less abundant under polar conditions. This suggests that sea ice melt may act as a barrier to the northward expansion of temperate phytoplankton, preventing their dominance in regions still strongly influenced by polar conditions. Our findings highlight the complex interactions between sea ice melt, phytoplankton dynamics, and biodiversity in the Arctic.

Impact of critical eddy diffusivity on seasonal bloom dynamics of Phytoplankton in a global set of aquatic environments

The intensity of eddy diffusivity and the spatial average of water velocity at the depths of the water column in oceans and lakes play a fundamental role in phytoplankton production and phytoplankton and zooplankton biomass, and community composition. The critical depth and intensity of turbulent mixing within the water column profoundly affect phytoplankton biomass, which depends on the sinking characteristic of planktonic algal species. We propose an Nutrient-Phytoplankton-Zooplankton (NPZ) model in 3D space with light and nutrient-limited growth in a micro-scale ecological study. To incorporate micro-scale observation of phytoplankton intermittency in bloom mechanism in stationary as well as oceanic turbulent flows, a moment closure method has been applied in this study. Experimental observations imply that an increase in turbulence is sometimes ecologically advantageous for non-motile planktonic algae. How do we ensure whether there will be a bloom cycle or whether there can be any bloom at all when the existing phytoplankton group is buoyant, heavier, motile, or non-motile? To address these questions, we have explored the effects of critical depth, the intensity of eddy diffusivity, spatial average of water velocity, on the concentration as well as horizontal and vertical distribution of phytoplankton and zooplankton biomass using a mathematical model and moment closure technique. We quantify a critical threshold value of eddy diffusivity and the spatial average of water velocity and observe the corresponding changes in the phytoplankton bloom dynamics. Our results highlight the importance of eddy diffusivity and the spatial average of water velocity on seasonal bloom dynamics and also mimic different real-life bloom scenarios in Mikawa Bay (Japan), Tokyo Bay (Japan), Arakawa River (Japan), the Baltic Sea, the North Atlantic Ocean, Gulf Alaska, the North Arabian Sea, the Cantabrian Sea, Lake Nieuwe Meer (Netherlands) and several shallower lakes.

Seasonal interactions between Quagga Mussel grazing and phytoplankton in western Lake Erie: The view from different measuring technologies

Abstract We measured Quagga Mussel grazing-induced changes in seston concentration in 20-L laboratory mesocosms containing lake water, during May-October, as part of a study to investigate the present role of mussel feeding and nutrient excretion in affecting phytoplankton composition. A variety of measuring methodologies including size-fractionated chlorophyll (< 2, 2-20, and >20 µm), phytoplankton groups by FluoroProbe, cyanobacterial genera by 16S rRNA gene sequencing, and particulate C, N, and P gave us different insights into seasonal phytoplankton dynamics and mussel selective feeding and assimilation. High clearance rates and/or high assimilation rates were seen during late May-early July across all size categories, with high rates seen particularly in cryptophytes and diatoms as revealed by FluoroProbe. Starting in late July cyanophytes dominated the phytoplankton and feeding rate on them was generally zero or low. Sequencing analyses suggested that there was a diverse cyanobacterial community present, with Microcystis, contrary to expectation, dominating only in late June. Cyanobium was the dominant genera at most times during summer-fall, and as expected, Microcystis was rejected by mussels relative to other cyanobacteria. Planktothrix, dominant in spring, was readily ingested as well as Anabaena in late June. We show that a combination of methods is helpful to make progress in understanding plankton succession and grazing. These methods were important adjuncts to microscopic analysis (Carrick et al, this issue). Our results support the hypothesis that dreissenid mussels, when abundant, can affect seasonal succession of phytoplankton shifting composition to cyanobacteria and even changes within the cyanobacterial community; however, impacts are likely modest now due low mussel biomass (Carter et al., this issue). Assimilation of C, N, and P was generally high, which is important for mussel population maintenance.

Annual Dynamics of a Layered Phytoplankton Structure in a Meromictic Lagoon Partially Isolated from the White Sea

In a saline semi-isolated lagoon on Cape Zeleny (White Sea), the annual dynamics of the vertical hydrological structure and the seasonal dynamics of phytoplankton were traced. Species composition, vertical distribution, abundance, nutrition type, and biomass were analyzed. In total, 293 species and supraspecific taxa of algae and cyanobacteria were found. Most of the identified species are marine, and 38 species are freshwater. Taxonomic composition changed in the lagoon throughout the year. Dinoflagellates dominated in winter and early June; unidentified cocci and flagellates in July; diatoms, dinoflagellates, and unidentified cells in August; dinoflagellates in September; and unidentified cocci and flagellates in October–November. The abundance of algae also changed in the lagoon throughout the year. The integrated biomass in the water column varied from 0.01 g C/m2 in January to 0.78 g C/m2 in early September. According to the environmental parameters, the water column of the lagoon was subdivided into several zones with different environmental conditions and corresponding phytoplankton communities. The similarity between the communities of different horizons was 32–46% in summer and 7% in winter. The chemocline layer was the most populous. It contained a maximum of phytoplankton biomass, 1–2 orders of magnitude higher than that in the overlying horizons. Despite the connection to the sea, the phytoplankton structure in the surface water layer in the lagoon and in the sea differed significantly in composition, quantitative parameters, and seasonal dynamics. The similarity between the communities never exceeded 50%. In terms of biomass dynamics, the lagoon lagged behind the sea until mid-summer, but, starting from August, it outnumbered it, and the phytoplankton development in the lagoon lasted longer, until late autumn. According to sequential tests DistLM, the phytoplankton structure and dynamics in the lagoon and in the sea were related to the daylength, water salinity, oxygen content, and pH by 24.5%. At the same time, the PhP structure did not depend on water temperature, underwater illuminance, or depth. Oxygen content and pH were defined by PhP activity. Salinity serves as a vector of the vertical sequence of ecological niches. The day length seems to be the crucial factor of the seasonal PhP dynamics in the semi-isolated coastal stratified lakes and lagoons.

Seasonal dynamics of phytoplankton in the northern part of Suez Gulf, Egypt

This study was conducted to evaluate the seasonal variability of phytoplankton in the northern part of the Gulf of Suez (Suez Bay), considering the contribution of physicochemical parameters of bay water in shaping the dynamics, and eutrophication assessment. Water and phytoplankton samples were collected seasonally at nine stations in the Suez Bay during the period from the winter to autumn of 2012. A total of 423 phytoplankton species were identified, comprised mainly of 224 diatoms, 127 dinoflagellates, 33 cyanophytes, 20 chlorophytes, and 9 euglenophytes; the rest of the species (10 species) belong to other six groups. Of these, 28 species were potentially harmful. The total phytoplankton abundance exhibits a significant seasonal variation, with the autumn being the most fertile season, followed by the winter due to the proliferation of diatom species Thalassionema nitzschioides and Proboscia alata f. gracillima, respectively. While the seasonal species richness indicates that the winter attained the highest number of species, followed by summer. Generally, the major diatom genera were Chaetoceros (16 species), Navicula (15 species), Nitzschia (15 species), and Amphora (14 species), while dinoflagellates were principally composed of the genera Protoperidinium (34 species), and Tripos (26 species). Water temperature, pH, salinity, nitrate, and nitrite were the most important explanatory parameters in regard to phytoplankton abundance and chlorophyll a concentration. In addition, the phytoplankton stability exhibited a significant positive relationship with the mean values of dissolved oxygen and biological oxygen demand and the variability of salinity and phosphate, while a negative relationship was observed with ammonia and nitrite and the variability of nitrate. Based on the trophic index (TRIX), the bay water was classified as mesotrophic (moderately polluted) for almost the entire year except in the autumn as it turned eutrophic. The results explored the potential importance of the environmental heterogeneity in the bay as a key structuring mechanism of phytoplankton abundance and biomass, influenced by anthropogenic activities.

Phytoplankton Dynamics and Biogeochemistry of the Black Sea

The biogeochemistry of waters is an essential regulator of phytoplankton dynamics, determining the level of species bloom and the change in dominants. This paper investigated the seasonal dynamics of phytoplankton and the nutrient concentrations and their ratios in the northeastern Black Sea in 2017–2021. Two taxonomic groups, diatoms and coccolithophores, determine the seasonal dynamics and significantly contribute to the total phytoplankton biomass. Coccolithophores formed blooms in early June annually, except in 2020. Large diatoms dominated in summer with a biomass exceeding 1000 mg m−3 annually, except in 2019. During the blooms of these taxonomic groups, their contribution to the total phytoplankton biomass exceeded 90%. Each group has characteristic biogeochemical niches in the nitrogen and phosphorus concentration coordinates. The position of the seasonal thermocline regulates the biogeochemistry of the water. With a high-lying and sharp gradient thermocline (the average for five years is 6.87 m), low nitrogen concentrations and a nitrogen-to-phosphorus ratio below the Redfield ratio are created in the upper mixed layer. These conditions are optimal for the dominance of coccolithophores. When the thermocline is deepened (the average for five years is 17.96 m), the phosphorus concentration decreases significantly and the ratio of nitrogen to phosphorus is significantly higher than the Redfield ratio, and these conditions lead to the dominance of large diatoms. The results of experimental studies with nitrogen and phosphorus additives in the natural phytoplankton population confirm the above statements. The addition of phosphorus leads to the increased role of coccolithophores in the total phytoplankton biomass, the addition of nitrogen alone contributes to the growth of large diatoms, and the combined addition of phosphorus and nitrogen in a ratio close to the Redfield ratio leads to the dominance of small diatoms.

Human activity as a factor causing the biomass, structure and seasonal dynamics of phytoplankton in adjacent fishponds

The role of phytoplankton as one of the main sources of energy entering the water food network is especially evident in fish-rearing ponds. Indeed, in these comparatively small ponds (unlike many lakes), variations in the abundance of phytoplankton can be extremely sensitive to the action of external factors, including human activity. Here, we present results of the analysis of the phytoplankton dynamics in adjacent fishponds and in supplying/recipient river courses upstream and downstream of the ponds during a growing season. In the grow-out ponds, phytoplankton biomass is shown to reach maximums in spring and in early autumn, while in the nursery pond, the phytoplankton dynamics is characterized by one long peak. The specificity of fish-rearing ponds as the human-regulated reservoirs clearly manifests itself under comparison of phytoplankton biomass of ponds with the biomass of phytoplankton inhabiting a nearby river. The averaged phytoplankton biomass in the ponds was 6.2–10.1 times higher than in the river. Besides, we show here that the taxonomic composition of phytoplankton in the river differs significantly from the composition of phytoplankton in the fish-rearing ponds. In particular, Cyanobacteria and Chlorophyta were revealed as the major portion of the phytoplankton in the fish-rearing ponds, while in the river their abundances were low.

Phytoplankton Seasonal Dynamics under Conditions of Climate Change and Anthropogenic Pollution in the Western Coastal Waters of the Black Sea (Sevastopol Region)

The studies of seasonal phytoplankton dynamics, its growth rate, and microzooplankton grazing were conducted on two stations in the western Black Sea coastal waters near Sevastopol from January 2021 to December 2022. The phytoplankton species composition has remained relatively the same during recent years compared to the end of the last century and the beginning of the 2000s. However, significant changes have occurred in the ratio between different species of diatoms, and the proportion of dinoflagellates was increased, especially in the autumn. Large diatoms and dinoflagellates play a crucial role in forming the phytoplankton biomass seasonal peaks. The first central maximum was observed in July, and the second smaller one was in September–November. Whereas two decades ago, the small diatoms generated three peaks annually: in February, May, and September–October. The maximum values of the phytoplankton growth rate and the rate of its consumption by microzooplankton decreased 2–3 times compared to the beginning of the 2000s. The relative share of primary production consumed by microzooplankton annually averages 35%, two times lower than before.

Novel insights in seasonal dynamics and co-existence patterns of phytoplankton and micro-eukaryotes in drinking water reservoir, Northwest China: DNA data and ecological model.

Although associations between phytoplankton and micro-eukaryotes have been studied in aquatic ecosystems, there are still knowledge gaps in comprehending their dynamics and interactions in drinking water reservoirs. Here, the seasonal dynamics of phytoplankton and micro-eukaryotic diversities and their co-existence patterns were studied in a drinking water reservoir, Northwest China. The highest phytoplankton diversity was observed in summer, and Chlorella sp. that belongs to Chlorophyta was the most abundant genus. The highest eukaryotic diversity was also detected in summer, and Rimostrombidium sp. that belongs to Ciliophora was the most dominant genus. Mantel test showed that the phytoplankton diversity was significantly correlated with ammonia nitrogen (r = 0.561, p = 0.001) and dissolved organic carbon (r = 0.267, p = 0.017), while the eukaryotic diversity was significantly associated with ammonia nitrogen (r = 0.265, p = 0.034) and temperature (r = 0.208, p = 0.046). PLS-PM (Partial Least Squares Path Modeling) further revealed that nutrients (P < 0.01) significantly affected the phytoplankton diversity, while nutrients (P < 0.01) and temperature (P < 0.01) significantly influenced the eukaryotic diversity. Co-occurrence network displayed the primarily positive interactions (77.66% positive and 22.34% negative) between phytoplankton and micro-eukaryotes. These findings could deepen our understanding of interactions between phytoplankton and micro-eukaryotes and their driving factors under changing aquatic environments of drinking water reservoirs.

Features of the Seasonal Dynamics of Phytoplankton in the Kama River (Kuibyshev Reservoir) in 2017

Features of the Seasonal Dynamics of Phytoplankton in the Kama River (Kuibyshev Reservoir) in 2017

The Structuring Effects of Salinity and Nutrient Status on Zooplankton Communities and Trophic Structure in Siberian Lakes

Many continental saline lakes are under the effects of salinity increase and anthropogenic eutrophication exacerbated by global change. The response of the food web to these drivers of change is not straightforward. To understand the consequences of salinity and eutrophication interactive effects on the food web, we studied the seasonal dynamics of zooplankton and phytoplankton and water quality parameters in 20 lakes of different salinity (from freshwater to hypersaline) and nutrient status (from oligotrophic to eutrophic) located in southern Siberia. We observed a pronounced bottom-up effect of nutrients, which induced an increase in the biomass of phytoplankton and zooplankton and a decline in water quality. A significant decrease in the species abundance of zooplankton was observed at a threshold salinity of 3 g L−1 and the disappearance of fish at 10 g L−1. The top-down effect induced by salinity manifested itself in an increase in the biomass of zooplankton with the disappearance of fish, and in the change of the size distribution of phytoplankton particles with an increase in the proportion of cladocerans in the zooplankton. Even though we observed that with the salinity increase the food web in saline lakes transformed from three-trophic to two-trophic without fish, we conclude that in the salinity range from 10 to 20–30 g L−1 this transition in most cases will not increase the ability of zooplankton to control phytoplankton. Interactive effects of salinity and eutrophication strongly depend on the size and depth of the lake, as deep stratified lakes tend to have a better water quality with lower biomasses of both phyto- and zooplankton. Thus, the salinity per se is not the driver of the decline in water clarity or the uncontrolled development of phytoplankton. Moreover, for deep lakes, salinity may be a factor affecting the stability of stratification, which mitigates the consequences of eutrophication. Thus, small shallow lakes will be the most vulnerable to the joint effect of salinity increase and eutrophication with the degradation of ecosystem functioning and water quality at moderate salinities of 3–20 g L−1.

Seasonal Dynamics of Phytoplankton in the Chupa Inlet (Kandalaksha Bay, White Sea)

Seasonal Dynamics of Phytoplankton in the Chupa Inlet (Kandalaksha Bay, White Sea)

Dynamics of abundance and biomass of Gonyostomum semen (Ehr.) Diesing in Valaam lakes

The paper presents long-term material on the succession of species Gonyostomum semen (Ehr.) Diesing collected on the lakes of the Valaam archipelago. The work was carried out on 10 small lakes about Valaam archipelago, maintaining a natural mode of functioning. The lakes differed in the shape of the basin, depth, and features of the hydrochemical regime. For lakes, a wide range of limnological parameters was revealed, such as transparency (0,3–4,6 m), active reaction of the environment (4,0–8,6), water color (27–296° according to Pt–Co scale), the content of total organic matter (10,8–63,8 mgO/dm3) and mineral phosphorus (0,001–0,646 mg/dm3). The phytoplankton structure varied significantly from lake to lake. In terms of abundance in most small lakes in biomass rafidophyte algae dominated. G. semen biomass varied from 1,1 to 82,3 mg/dm3. In the seasonal dynamics of phytoplankton, one or two peaks were noted, which occurred in different years in different months, most often in June or September.

Seasonal dynamics of phytoplankton and its relationship with environmental factors in Lake Hulun

为探究呼伦湖浮游植物群落的季节变化特征及其与环境因子的关系，本研究分别于2019年3、5—10月对呼伦湖浮游植物的种类、细胞密度和生物量及湖水水质进行调查.结果显示，共鉴定出120种浮游植物，隶属于7门72属.从浮游植物群落季节组成差异上来看，春季绿藻门种类数最多，其次是硅藻门、蓝藻门；夏秋季绿藻门种类数最多，蓝藻门次之；冬季硅藻门种类数最多，绿藻门次之.呼伦湖浮游植物优势种主要为硅藻门的梅尼小环藻（Cyclotella meneghiniana）、蓝藻门的卷曲长孢藻（Anabaena circinalis）和细小平裂藻（Merismopedia minima），种类数在春季最多，秋冬季最少.浮游植物细胞密度在春季（123.52×10⁴ cells/L）和冬季（16.41×10⁴ cells/L）较夏季（280.80×10⁴ cells/L）和秋季（380.63×10⁴ cells/L）低，春冬季绿藻门细胞密度最高，夏秋季蓝藻门细胞密度最高.就浮游植物生物量而言，夏季（0.38 mg/L）最大，其次是秋季（0.26 mg/L）和春季（0.24 mg/L），冬季（0.13 mg/L）最小.香农-威纳（Shannon-Wiener）多样性指数、均匀度指数和综合营养状态指数均表明呼伦湖水体处于中营养状态.冗余分析（RDA）表明：水温、叶绿素a、pH和营养盐浓度是影响呼伦湖浮游植物群落分布的主要环境因子.;To understand the phytoplankton community characteristics and its relationships with environmental factors, we investigated the species, abundance and biomass of phytoplankton and environmental factors at eight sampling sites in Lake Hulun during March and from May to October of 2019. The results showed that:A total of 120 phytoplankton species were identified, belonging to 7 plyla and 72 genera. In terms of the seasonal composition of the phytoplankton community, Chlorophyta was the dominant groups in spring, followed by Bacillariophyta and Cyanophyta. The number of Chlorophyta was the largest in summer and autumn, followed by Cyanophyta. Bacillariophyta was the dominant group in winter, followed by Chlorophyta. The dominant species of phytoplankton in Lake Hulun were Cyclotella meneghiniana of Bacillariophyta, Anabaena circinalis and Merismopedia minima of Cyanophyta. The number of the dominant species was the most in spring and the least in autumn and winter. The phytoplankton abundance in spring (123.52×10⁴ cells/L) and winter (16.41×10⁴ cells/L) was lower than that in summer (280.80×10⁴ cells/L) and autumn (380.63×10⁴ cells/L). The abundance of Chlorophyta was the highest in spring and winter, and the abundance of Cyanophyta was the highest in summer and autumn. In terms of phytoplankton biomass, summer (0.38 mg/L) had the largest, followed by autumn (0.26 mg/L) and spring (0.24 mg/L), and winter (0.13 mg/L) had the smallest. Shannon-Wiener diversity index, evenness index J and comprehensive trophic state index all indicated that Lake Hulun was in mesotrophic condition. Redundancy analysis of phytoplankton abundance and water environmental factors showed that water temperature, chlorophyll-a, pH and nitrogen and phosphorus nutrients were the main environmental factors that affected the distribution of the phytoplankton community in Lake Hulun.

Experience in using the methods of catastrophe theory in describing the dynamics of phytoplankton in the Vistula lagoon of the Baltic Sea

Ideas and methods of catastrophe theory are widely used to analyze “regime shifts” in ecosystems. In this work, the analysis of the seasonal dynamics of phytoplankton in the Russian part of the Vistula Lagoon of the Baltic Sea is carried out on the basis of using the simplest possible model of the catastrophe theory − cusp catastrophe. The total phytoplankton biomass is considered as a state variable. The use of one of the methods of multivariate analysis − principal components method − made it possible to carry out the entire analysis depending on a small number of parameters. A calculation of the control parameters values is carried out using the factor loadings of the main components for the data that characterize the hydro-physical and hydro-chemical regimes as well as the level of biogenic loading on the aquatic ecosystem of the lagoon. It was found that, depending on the specific situation, the same factor or different combinations of factors can play both a stabilizing role and be the cause of destabilization.

Relative roles of fundamental processes underpinning PEG dynamics in dimictic lakes as revealed by a self-organizing, multi-population plankton model

The longstanding PEG (Phytoplankton Ecology Group) qualitative/conceptual model describes generalized seasonal phytoplankton dynamics in temperate lakes and suggests important mechanisms driving these processes. In the research presented here, we re-created the conceptual PEG dynamics using a novel mechanistic numerical plankton model. The numerical model incorporates only a handful of interacting factors and biological rules. Key model features include seasonally variable temperature, mixing depth, and light, dynamic zooplankton and phytoplankton populations, and multiple dynamic nutrient concentrations. The model design is unique in that it incorporates a population-rich phytoplankton assemblage where life-history traits of members are based on ecological principles (trade-offs between traits), allowing the assemblage to organize over time based on nutrient competition and grazing. Using 50th year solutions to the model solved with fourth-order Runge-Kutta methods, i.e., a period when the dynamics had reached stable non-equilibrium states, sensitivity analyses were run by individually varying model parameters +/- 50% and comparing the effect on model responses of interest. Simulation analyses revealed the important role light and temperature limitation played both early and late in the year controlling plankton biomass. Trade-offs in phytoplankton life-history characteristics determined the composition of the spring bloom under non-nutrient limiting conditions (fast-growing, edible populations dominated) and the post clear-water phase assemblage under low nutrient conditions (slower-growing, less-edible populations dominated). Grazer characteristics, specifically rate of grazing and spring “emergence”, determined the occurrence of the clear-water phase and influenced the post assemblage composition, where a clear-water phase was absent when the grazing rate was low or spring emergence absent, and the highly inedible populations were lost from the assemblage. Hydraulic flushing also played an important role where diminished inflow led to higher richness, evenness and diversity due to greater overwintering of less-edible taxa, which influenced phytoplankton composition during spring bloom, diminishing secondary productivity. These results increase understanding of the relative roles of fundamental mechanisms structuring natural aquatic ecosystems and reinforce the significance of key biotic and abiotic system components of temperate lakes.

Comparative analysis of the structure of planktonic algae of the Volga and Kama rivers before their confluence in the Kuibyshev reservoir (the Republic of Tatarstan, RF)

The article presents the results of comparative analysis of the structure of planktonic algae in the Volga and Kama rivers, as well as the assessment of the trophic state of these water bodies, which form the Kuibyshev reservoir at their confluence. The hydrochemical regime of the Kuibyshev reservoir is nonhomogeneous and is determined by the chemical properties of the Volga and Kama, differing in the ratio of ions and mineralization. The ionic compositionin Kama is often dominated by sulfates. Its mineralization ranges from 168 to 674 mg L-1, depending on the season and dryness of the year. The Volga contains calcium hydrocarbonate and display a lower degree of mineralization (120-130 mg L-1). Different composition of the incoming water, runoff rate, the degree of volume drawdown, intra-basin processes and groundwater inflows exhibit a direct impact on the conditions for the existence of planktonic algae. During the growing season of 2012, 123 algae taxa were identified among the phytoplankton of the Volga and Kama rivers (the areas before their confluence in the Kuibyshev reservoir). In terms of species diversity, diatoms and green algae were prevalent. The Volga exhibits higher species diversity (107 species), while the phytoplankton in Kama displays less diverse (77 species). In the seasonal dynamics of phytoplankton in both areas, two peaks of abundance and biomass are observed, i.e., at the middle and at the end of summer. The studied areas of Volga River are characterized by a phytoplankton complex of blue-green, diatoms and green algae, while diatom phytoplankton predominates in Kama River. In the summer-autumn period, the blooming of water in both rivers is connected with massive development of blue-green algae of the genera Aphanizomenon, Microcystis, Anabaena and Oscillatoria. During most of the growing season, the waters of Volga and Kama rivers belong to the mesasaprobic type and correspond to the moderately-polluted zone. Moreover, the waters of Kama River are characterized by higher saprobity indices. The trophic status of studied rivers mostly corresponds to eutrophic type, and in the periods of maximum development of planktonic algae - to hypereutrophic type.