Number Of Phytoplankton Species Research Articles

A fjord with a land-terminating glacier: Meltwater, bio-optics, particulate matter, nutrients, phytoplankton species, and primary production in west Greenland

Land-terminating glaciers and submarine melting of marine-terminating glaciers are significant features in Arctic regions and are foreseen to become more frequent as marine-terminating glaciers ultimately develop into a land-terminated state. A transition driven by the continuous rise in Arctic air temperatures, and emphasizes the importance of studies of land-terminating glaciers their bio-optical properties and biogeochemistry. Kangerlussuaq in west Greenland with a land-terminating glaciers and was selected for this study. During a research cruise we measured spectral and PAR attenuation, particulate matter concentrations, salinity, nutrient concentrations, Chla, and phytoplankton species composition, along a transect from river outlet to open marine waters. Results showed that surface waters in Kangerlussuaq were strongly influenced by meltwater with low salinities, high particulate matter concentrations, high PAR and spectral light attenuation coefficients, and low nutrient concentrations. Spectral composition was also affected by the particulate matter. PAR photic depths varied between 4 and 9 m dependent on particulate matter concentrations. There was a decrease with distance from outlet in silicate concentrations, and opposite for phosphate, which increased significantly from river outlet to the marine. Phytoplankton species number (42) and diversity were high at the marine station but low (3) in turbid waters dominated by the diatom Skeletonema costatum in high numbers. A meltwater plume covered about 50 % of the Kangerlussuaq at average discharges in early August. Primary production was quantified with a simple model based on light attenuation coefficients, and showed a near exponential decrease in production with increase in attenuation.

The Impacts of Land Use and Seasonal Effects on Phytoplankton Taxa and Physical-Chemical Variables in the Tigris River within the City of Mosul

We investigated the effect of land use based on the dominant phytoplankton and physical-chemical variables in the different areas of the Tigris River, within the city of Mosul. Agricultural and urban activities have a significant impact on the water quality of the river. Regardless of physical and chemical variables, phytoplankton act as a bio-indicator of water quality due to their fast and sensitive response to changes in the environment. Our research was conducted in the Tigris River within the city of Mosul by examining the phytoplankton species and the physical-chemical variables at 16 sites during each vegetation period. Point and non-point source pollutants have affected the Tigris River within the city of Mosul, getting into the river from upstream through agricultural activities and by urban activities in the middle section of the city, respectively from both banks. Based on our results, we observed the highest phytoplankton abundance during the October sampling periods, while the lowest occurred during the July sampling period, which was associated with maximum water temperature and absence of rain. According to our study, land use (e.g., agricultural, and urban activities) greatly affected the dominant phytoplankton species and physical-chemical variables of the Tigris River. Oscillatoria sp. dominated all seasons in the agricultural region, while at the same time, we observed an increase in the number of phytoplankton species caused by the nutrient availability upstream on the river. The effects of climate have very significant and characteristic effects in this area, which basically determine the community of organisms and the water quality; the effects resulting from anthropogenic activity significantly modify this. Based on our investigation, in the part of the Tigris River connected to Mosul, we found a clear connection between the pollution caused and the effects of different land uses, through the examination of the algal community and physical-chemical variables in different periods of the year.

Advances in phytoplankton population ecology in the Pearl river estuary

Phytoplankton is an important primary producer of the estuarine ecosystem, which is essential for the biogeochemical cycle of water elements and nutrient transfer. The Pearl River estuary (PRE) is a dynamically complex estuary, and the environment of PRE is significantly impacted by anthropogenic activities, variation of phytoplankton community structure in the PRE are complex. This review aims to compare phytoplankton species, species diversity, and abundance variation characteristics from the 1980s and 2020s, evaluate the overall trend of phytoplankton in the PRE, and discuss the main environmental factors affecting phytoplankton growth in the PRE. The data from the past 40 years in PRE showed that the number of phytoplankton species significantly decreased (p < 0.05). There was no significant difference in the abundance of phytoplankton at the 10-year scale, however, the fluctuation range of the abundance has increased. Under the conditions of a decreasing species number and no significant difference in abundance, the species diversity of phytoplankton showed a downward trend. In addition, the dominant phytoplankton species in the nearshore waters were relatively homogenous, and the abundance of phytoplankton in the nearshore waters was higher than that in the open waters, which suggested that human activities have a great influence. This review can form the basis for facilitating health management in the PRE ecosystem. Further, relevant guidelines can be developed and implemented for promoting the ecological health of the Guangdong-Hong Kong-Macao Greater Bay Area and ensuring its sustainable development.

Species diversity and community structure of phytoplankton in the Velikaya Salma Strait (Kandalaksha Bay, White Sea) in 2021

The species diversity and community structure of phytoplankton in the Velikaya Salma Strait (Kandalaksha Bay, the White Sea) were investigated from May to September 2021. A total of 128 algal taxa were identified, comprised of diatoms (80% of the total phytoplankton species number), dinophytes (15%), cyanobacteria (3%), ochrophytes (1%) and cercozoans (1%). The phytoplankton abundance varied from 1.84х106 cells/m3 (in August) to 23.27х106 cells/m3 (in July); phytoplankton biomass varied from 31.4 mg/m3 (in May) to 246.7 mg /m3 (in July). Diatoms was the dominant group in terms of quantity and biomass, one dinophyte species, Sсrippsiella acuminata, was dominant in terms of quantity too.

Geostatistical Analysis of Mangrove Ecosystem Health: Mapping and Modelling of Sampling Uncertainty Using Kriging

This study assessed the health of the mangrove ecosystem and mapped the spatial variation in selected variables sampled across the Matang Mangrove Forest Reserve (MMFR) by using a geostatistical technique. A total of 556 samples were collected from 56 sampling points representing mangrove biotic and abiotic variables. All variables were used to generate the semivariogram model. The predicted variables over the entire MMFR have an overall prediction accuracy of 85.16% (AGB), 90.78% (crab abundance), 97.3% (soil C), 99.91% (soil N), 89.23% (number of phytoplankton species), 95.62% (number of diatom species), 99.36% (DO), and 87.33% (turbidity). Via linear weight combination, the prediction map shows that mangrove ecosystem health in Kuala Trong throughout the Sungai Kerang is excellent (5: MQI > 1.5). Some landward areas of Kuala Trong were predicted to have moderate health (3: −0.5 ≤ MQI ≤ 0.5), while Kuala Sepetang was predicted to have the bad ecosystem health (2: −1.5 ≤ MQI ≤ −0.5), with active timber harvesting operations and anthropogenic activities in the landward areas. The results of this method can be utilised to carry out the preferred restoration, through appropriate management and facilities distribution, for improving the ecosystem health of mangroves.

Phytoplankton community composition variation under natural and prolonged saline intrusion simulations

This study assessed phytoplankton community composition variation under two discrete salinity intrusion rate experiments. Experiment 1 simulated salinization under short-term, natural tidally induced rates of salinity change typical of the Mekong Delta, Vietnam (0–30‰ in 6 h), while Experiment 2 simulated salinization under a longer, more gradual rate of salinity change (0–30‰ at 5‰ increase per week). Phytoplankton community composition was, overall, more abundant following prolonged salinity change (Experiment 2) than rapid, tidally-induced salinity change (Experiment 1). Under both experimental conditions phytoplankton species number and density varied with changes in salinity, indicating a strong effect of salinity regardless of its rate of change. At the end of the salinity acclimation, Cyanobacteria, Chlorophyta, Euglenophyta and Bacillariophyta were all most abundant at a salinity of 5‰ after a short-term tidally simulated change in salinity, but with a longer, more gradual change in salinity, the abundance of different groups varied with salinity; With a longer, more gradual change in salinity, Chlorophyta was most abundant at 5–10‰ salinity, while Cyanobacteria, Euglenophyta and Bacillariophyta were all most abundant at a salinity of 5‰. The species composition in treatments of less than 10‰ had high similarity with the freshwater environment while treatments of 30‰ (Experiment 1) and 25‰ (Experiment 2) had high similarity with the natural seawater environment. This study demonstrates the utility of mesocosm experiments for understanding phytoplankton community composition variation in natural aquatic ecosystems under rapid and prolonged saline intrusion rates and predicting associated impacts on food webs in natural water bodies and aquaculture systems.

Phytoplankton community structure changes in Thi Nai lagoon (South - Central Vietnam) from 2004 to 2020

Phytoplankton species composition, abundance, biodiversity indices and their influence by environmental conditions were examined in Thi Nai lagoon using data from four surveys in 2004, 2008, 2009 and 2020. A total of 367 taxa of phytoplankton belonging to ten groups was recorded, of which diatoms were dominant with over 60% of the total species. In Thi Nai lagoon, the number of phytoplankton species decreased from the upper lagoon (283 taxa) to the lagoon mouth area (224) and was lowest in river stations (139). The species number was much lower in the rainy season (<95 species) and increased from 2004 to 2020. Among the biodiversity indices, Shannon, ∆, s∆+, Λ+ and sФ+ were lower in the rainy season, whereas ∆*, ∆+ and Ф+ had lower values in the dry season. For long-term analysis, the differences were especially significant at upper and lower lagoon for ∆, ∆*, ∆+, s∆+ and sФ+. In the dry season, the mean density of phytoplankton was lower at the river stations and upper lagoon, but higher at the lower lagoon and the lagoon mouth area. There was a clear difference of species assemblages between the two seasons with average dissimilarities in each area ranging from 94.16% to 95.57%. During 2004–2020, the difference in ratios between the main phytoplankton groups were small over years but there was a complete change in dominance of particular species, assemblage dissimilarities were from 73.4 to 77.9, greatest between 2009 and 2020. The lagoon was low in biodiversity for the whole investigated time indicated by taxonomic index ∆+. Among biodiversity indices, species richness (S), taxonomic indices (∆*, s∆+), and phylogenetic indices (Ф+, sФ+) were more sensitive to the changes of the aquatic environment than other traditional indices.

Multivariate approach to determine the ecological preferences of phytoplankton in Uppanar estuary, southeast coast of India

In the present study, the phytoplankton diversity and distribution was studied in relation seasonal variation of environmental parameters in the Uppanar estuary. Samples were seasonally collected (i.e., pre-monsoon: July-2018 and summer: June-2019) from six stations. A total of 62 phytoplankton species belonging to three classes, 20 orders, 26 families and 36 genera were and among the three phytoplankton taxa, diatoms topped the list with 41 species followed by Dinoflagellates (17 species) and blue green algae (4 species). The maximum number of phytoplankton species (36) and diversity value (H’) 3.976 was recorded in the stations near river mouth (UE-6) during summer and minimum species number (21) and maximum species richness (d) 6.923 was recorded in stations close to industrialr zone (UE-1) during monsoon. The maximum species evenness (J') 0.928 was recorded at stations near river mouth (UE-6). BIO-ENV (Biota-Environmental matching) and CCA results confirmed that the environmental parameters such as Dissolved oxygen, Turbidity, Salinity, Water pH, Chlorophyll, Silicate, TN and TP as best match (ρω = 0.968) in determining phytoplankton distributions. The results of present study helps to develop an understanding on the phytoplankton distribution based on physico-chemical parameters, which will form a reliable tool in bio-monitoring studies.

Phytoplankton composition of the mangrove ecosystem in Khanh Hoa province, Vietnam

The objective of this study was to clarify the structureof phytoplankton in the natural mangroves of Nha Phu lagoon in Khanh Hoa province, Vietnam, and their correlation with other environmental factors. The outcome of the surveys in the area showed that there was a high diversity of phytoplankton species with about 139 ones, particularly Silic algae dominance. The biomass of phytoplankton here is not high, ranging from 25 260 to 58686 cells/liter. The environmental parameters show that the area has a favorable environment for the growth of phytoplankton. The salinity of water was from 18 %o to 35 %o the temperature was between 29.4 °C and 30.1 °C, and the pH index varied from 7.03 to 7.98. Analysis of the relationship between the abundance of phytoplankton species and environmental factors pointed out that the number of phytoplankton species has an inverse linear proportion to the content of Chlorophyll-a but a direct one to the salinity and the total content of Phosphorus in seawater. Also, the biomass of phytoplankton has an inverse linear proportion to salinity and pH but follows the opposite one to the environmental temperature and the content of Chlorophyll-a.

Structural Characteristics of Zooplankton and Phytoplankton Communities and Its Relationship with Environmental Factors in a Typical Tributary Reservoir in the Three Gorges Reservoir Region

Based on the data of zooplankton, phytoplankton, and water environmental factors in different seasons in a typical tributary reservoir in the Three Gorges Reservoir Region (Changshou Lake), this study explored the relationships between the structures of the zooplankton and phytoplankton communities and environmental factors using Pearson correlation analysis. The results showed that there were a total of 107 species of 8 phyla of phytoplankton, and cyanobacteria was the most critical constituent with a relative abundance of 61%. The dominant populations included Phormidium tenue, Merismopedia punctata, and Anabaena oscillarioides. A total of 82 species of 4 phyla of zooplankton were identified, and rotifers was the most abundant with a relative abundance of 88%. The dominant populations included six species, such as Keratella cochlearis, Asplanchna priodonta, and Asplanchna girodi. The spatial differences in the abundances, biomass, and biodiversity indexes of zooplankton and phytoplankton were not significant, whereas the seasonal differences in all the other indexes were significant, except for the zooplankton biodiversity indexes. The abundance of phytoplankton was the highest in summer, followed by spring, and it was the lowest in winter. The maximum abundance of zooplankton occurred in spring, and the biomass of zooplankton and phytoplankton in spring was significantly higher than that in winter. The number of phytoplankton species and the Shannon-Wiener index, Pielou's uniformity index, and Margalef richness index in summer were significantly lower than those in winter and spring. The water quality evaluation showed that Changshou Lake was in a clean to oligo-pollution state in winter and spring and a moderate-pollution state in summer, thereby suggesting that Changshou Lake was in an overall eutrophic state. The environmental factors, including Chla, DOC, nutrients (TP, NO2--N, NO3--N, and NH4+-N), DO, Eh, and T, influenced the structures of the zooplankton and phytoplankton communities in Changshou Lake, and there were seasonal differences in the environmental factors.

Dynamical study of infochemical influences on tropic interaction of diffusive plankton system

We propose a model for tropic interaction among the infochemical-producing phytoplankton and non-info chemical-producing phytoplankton and microzooplankton. Volatile information-conveying chemicals (infochemicals) released by phytoplankton play an important role in the food webs of marine ecosystems. Microzooplankton is an ecologically important grazer of phytoplankton for coexistence of a large number of phytoplankton species. Here, we discuss how information transferred by dimethyl sulfide shapes the interaction of phytoplankton. Phytoplankton deterrents may lead to propagation of IPP bloom. The interaction between IPP and microzooplankton follows the Beddington–DeAngelis-type functional response. Analytically, we discuss boundedness, stability and Turing instability of the model system. We perform numerical simulation for temporal (ODE model) as well as a spatial model system. Our numerical investigation shows that microzooplankton grazing refuse of IPP leads to oscillatory dynamics. Increasing diffusion coefficient of microzooplankton shows Turing instability. Time evolution also plays an important role in the stability of system dynamics. The results obtained in this paper are useful to understand the dominance of algal bloom in coastal and estuarine ecosystem.

Ecophysiological and Anthropogenic Determinants of Phytoplankton Community Structure in Streams Receiving Effluents from the Douala-Bassa Industrial Zone

Physicochemical parameters and plankton community structure of streams flowing through the Douala-Bassa Industrial zone were assessed in seven different sites. Anthropogenic activities, water accessibility and the different industries located along the watercourse were considered in selecting the sites. Four sets of water samples were collected from each site and analysed for phytoplankton community structure, nutrient, Chl a and bacteria. Physicochemical parameters were measured insitu using a multi parameter equipment (HANNA 8289). Water temperature ranged from 25.27 - 26.840 C. The pH of the water samples ranged from 6.33 – 7.50 while Turbidity ranging from zero - 1000 NTU. The Electrical Conductivity was 495.33 - 261.67 µS/cm and Dissolved Oxygen was zero - 1.11 ppm. Chlorophyll a concentration ranged from 1.2 – 48.96µg/l. Total Suspended Solids ranged from 0.15 – 0.88. Phosphate and ammonium concentrations ranged from 1.22 – 12.81µM and 4.29 – 136.48 µM respectively nitrates concentration was 1.15 – 217.09 µM. The number of phytoplankton species varied between the sites with a total of 68 species belonging to 11 Divisions. The Bacillariophytas were the most abundant with 27 species. The Chlorophyta followed with 12 species. The most dominant phytoplankton species were Microcystis sp, Pinnularia gibba and Nitzschia palea. Site 7 was the most diverse site with 70 species. High concentrations of nutrients and the presence of eutrophic species such as the Bacillariophytas and Microcystis suggests pollution and a need to monitor activities carried out along the water course with respect to quantity and quality of wastewater discharged into the stream. The ecosystem was in a eutrophic state with variations in the water quality parameters. This could be attributed to possible untreated effluents incorporated in the ecosystem. It can be concluded from the study that phytoplankton dynamics in the Douala-Bassa Industrial Zone are directly related to ecophysiological and anthropogenic drivers.

Interannual Changes in Phytoplankton of the Iriklinsky Reservoir

The interannual changes in the phytoplankton (PP) of the upper and lower parts of the Iriklinsky reservoir during different seasons of the vegetation period are described, depending on the level regime, inflow, discharge of water, and its temperature. The correlations show the leading role of these factors. It was revealed that, in May, an increase in the inflow and water level leads to the depletion of the specific number of phytoplankton species and biomass, in contrast to the situation in July and October, when an increase in these indicators is observed. It is shown that the features of the ratio of the number of species and the biomass of phytoplankton in the upper and lower reaches are related to the level and discharge modes, as well as to water temperature.

Spatial and Temporal Variation of Phytoplankton Community Structure and Its Influencing Factors in Shanghai River Channels

In order to explore the spatial and temporal characteristics of the phytoplankton community structure and its influencing factors in Shanghai rivers, the water quality and phytoplankton community structure at 44 river channel sites in a central urban area, new town area, and rural area in Shanghai were investigated from September to October 2018 (autumn) and July to August 2019 (summer). The results showed that:① Chlorophyta was the dominant phyla during the autumn and summer, and was followed by Cyanobacteria and Bacillariophyta. Cyanobacteria dominated the phytoplankton community in terms of density. The number of species and density of phytoplankton were 24% and 2.77 times higher, respectively, than those during the summer and autumn. The dominance of Microcystis sp. was obvious during the autumn (Y=0.16), but there was no absolute dominant species during the summer. ② The difference in the number of phytoplankton species among the three regions was not significant, and the density of the total phytoplankton and cyanobacteria species showed a similar spatial pattern:rural area > new town area > central urban area. Additionally, no significant difference was observed in the total phytoplankton and Cyanobacteria density among the three regions during the autumn (P>0.05), whereas it was 1.82 and 1.93 times higher, respectively, in the rural area in comparison to the central urban area during the summer (P<0.05). Montecarlo test results revealed that the main factors affecting the phytoplankton community structure during the autumn were secchi disk transparency (SD), total phosphorus (TP), total nitrogen (TN), and turbidimetry (Turb), whereas these were TN, Turb, SD, and pH during the summer. ③ The results of a redundancy analysis (RDA) indicated that during the autumn, the phytoplankton in the rivers of the new town area were mainly affected by Turb, TN, and TP, while the rural rivers were mainly affected by SD. During the summer, the phytoplankton in the rivers of the new town and rural areas were mainly affected by TN and Turb. The influencing factors in the central urban area were complex.

Inhibition of competitive exclusion due to phytoplankton dispersion: a contribution for solving Hutchinson's paradox

G. E. Hutchinson raised the paradox of how a number of phytoplankton species competing for the same resources are able to coexist in a relatively isotropic environment. As a key for solving the paradox, we focused on the limiting similarity which prohibits the coexistence of similar species. We expected that the limiting similarity will be mitigated by some factors which are not represented in traditional theoretical studies but can be represented if we use a three-dimensional (3D) model. The use of a 3D model enables us to explore the limiting similarity without using the controversial assumption connecting niche overlap with the competitive exclusion in previous theoretical studies. Furthermore, while constant or no dispersion is given in theoretical studies, it is explicitly represented in a 3D model. The coexistence of similar species in 3D environments was explored by dividing a target persistent species in a quasi-equilibrium community into 80 subspecies, which were slightly different from one another at the optimum temperature for population growth. In the experiments, we found cases in which several dozens of species having nearly-overlapping niches coexist stably at a point for over 80 years. The comparison of experiments with and without dispersion by oceanic currents revealed that dispersion negates the progress of competitive exclusion or significantly delays the exclusion. The result that species having nearly-overlapping niches are able to coexist also highlights the crucial role of the specific rate in determining the number of coexisting species. If the number of coexisting species is not determined by the limiting similarity, it will be determined by the frequency of speciation events, as in the neutral theory.

Checklist and estimation of total number of phytoplankton species in Pari, Tidung, and Payung Islands, Indonesia

Abstract. Rachman A. 2020. Checklist and estimation of total number of phytoplankton species in Pari, Tidung, and Payung Islands, Indonesia. Biodiversitas 21: 2446-2454. A checklist of phytoplankton species from an anthropogenically pressured ecosystem has become a necessity to study the marine ecosystem changes and to detect the presence of introduced species in the area. This study aimed to list and describe the phytoplankton community in the Tidung, Pari, and Payung Islands and to estimate the total number of phytoplankton species in those islands. Sampling was conducted in May 2019 in 10 sites, consisted of 5 sites around Pari Island, 1 site next to Payung Island, and 4 sites around Tidung Island. As many as 150 species of phytoplankton, consisted of 109 species of diatoms, 38 species of dinoflagellates, 3 species of cyanobacteria, were recorded in this study. However, up to 47 phytoplankton species were estimated to be missing from the current sampling effort. Three diatom species, Chaetoceros curvisetus, Chaetoceros distans, and Chaetoceros affinis were the most abundant and most common species in the studied areas. Dinoflagellates were found in low density and have limited distribution compared to diatoms. Tripos trichoceros, Tripos fusus, and Tripos macroceros were the three most common dinoflagellates in the studied islands. Several notable harmful species, such as Pseudo-nitzschia spp., Alexandrium sp., Tripos furca, Cochlodinium sp., Dinophysis miles, Prorocentrum lima, and Noctiluca scintillans, were present albeit with low cell density. However, concern on future blooms of those harmful species in the greater water regions (i.e. Seribu Island or Jakarta Bay) should be noted, as it might cause environmental damages, including a shift in species dominance and disappearance of some native phytoplankton species from the ecosystem in the future.

The competitive exclusion principle in stochastic environments.

In its simplest form, the competitive exclusion principle states that a number of species competing for a smaller number of resources cannot coexist. However, it has been observed empirically that in some settings it is possible to have coexistence. One example is Hutchinson's 'paradox of the plankton'. This is an instance where a large number of phytoplankton species coexist while competing for a very limited number of resources. Both experimental and theoretical studies have shown that temporal fluctuations of the environment can facilitate coexistence for competing species. Hutchinson conjectured that one can get coexistence because nonequilibrium conditions would make it possible for different species to be favored by the environment at different times. In this paper we show in various settings how a variable (stochastic) environment enables a set of competing species limited by a smaller number of resources or other density dependent factors to coexist. If the environmental fluctuations are modeled by white noise, and the per-capita growth rates of the competitors depend linearly on the resources, we prove that there is competitive exclusion. However, if either the dependence between the growth rates and the resources is not linear or the white noise term is nonlinear we show that coexistence on fewer resources than species is possible. Even more surprisingly, if the temporal environmental variation comes from switching the environment at random times between a finite number of possible states, it is possible for all species to coexist even if the growth rates depend linearly on the resources. We show in an example (a variant of which first appeared in Benaim and Lobry '16) that, contrary to Hutchinson's explanation, one can switch between two environments in which the same species is favored and still get coexistence.

Community characteristics of phytoplankton and management implications in Poyang Lake Basin

Eutrophication of lakes is one of the most common pressures affecting aquatic biodiversity and ecosystem services. Poyang Lake is of great importance for maintaining regional ecological balance; however, algal blooms have become major environmental problems in this basin, and they are also caused by a variety of problems including biodiversity decline, toxin production and possibly unsafe drinking water. In this study, the community structure of phytoplankton and physicochemical parameters were investigated in different eutrophication area, Poyang Lake Basin. The results showed that the number of phytoplankton species had decreased, but the density and biomass were increased in the current period. The assemblage structure of phytoplankton showed significantly seasonal and spatial variability. The assemblage structure of phytoplankton was related to dissolved oxygen, nitrate nitrogen, chlorophyll-a and ammonium nitrogen, based on redundancy analysis. The study showed that the phytoplankton community structure was influenced by algal blooms and water quality factors. This study provides an important reference for increased biomonitoring and ecohydrological studies in this basin.

Horizontal and Vertical Distribution of Phytoplankton in the Alpine Lake Sevan (Armenia) during the Summer Cyanoprokaryota Bloom

A study of the horizontal and vertical distribution of phytoplankton in Lake Sevan was conducted in mid-July 2018 during the maximum Cyanoprokaryota blooms. The summer biomass of algae in the pelagic zone of the lake corresponded to values of mesatrophic waters. The Cyanoprokaryota biomass in Lake Sevan has horizontal and vertical heterogeneity and is related to the depth, morphometry of the lake parts, distribution of currents, transparency, temperature, and biomass of Cladocera. The specific number of phytoplankton species and water transparency decreases in areas where water blooms occur. The following factors contribute to the increase in the average phytoplankton biomass when compared to 2013–2017: (1) increased water temperature, (2) weakening of zooplankton grazing pressure due to the disappearance of Daphnia magna, and (3) increased phosphorus load due to increased contribution of D. longispina and Diaphanosoma lacustris to the zooplankton biomass.

Kelp cultivation effectively improves water quality and regulates phytoplankton community in a turbid, highly eutrophic bay

Coastal eutrophication and its associated harmful algal blooms have emerged as one of the most severe environmental problems worldwide. Seaweed cultivation has been widely encouraged to control eutrophication and algal blooms. Among them, cultivated kelp (Saccharina japonica) dominates primarily by production and area. However, the responses of water quality and phytoplankton community to kelp farming remain unclear. Here, thirteen cruises were conducted in the kelp farms and control areas in the turbid, highly eutrophic Xiangshan Bay of the East China Sea from 2008 to 2015. Results indicated that kelp cultivation slightly increased dissolved oxygen and pH, but reduced dissolved inorganic nitrogen and phosphorus. We estimated that kelp harvesting would remove 297 t of nitrogen and 42 t of phosphorus from this bay annually. Because of decreased flow velocity, turbulence, and sediment resuspension, kelp farming greatly reduced suspended solids and increased transparency, resulting in increases in phytoplankton chlorophyll a and abundance. Additionally, kelp farming appreciably increased phytoplankton species number, Marglef richness, and Shannon–Wiener diversity indices by 51.6%, 40.1%, and 13.1%, respectively. Analysis of similarity and similarity percentages demonstrated that phytoplankton community composition differed significantly between the farm and control area, which was mostly attributed to long-chained diatoms and single-celled dinoflagellates. However, after the kelp harvesting, all measurements of water quality and phytoplankton biomass, diversity, and community composition exhibited no significant difference. Our study highlights that kelp cultivation alleviates eutrophication and acidification and enhances phytoplankton diversity, thus providing guidance for macroalgal aquaculture and remediation in eutrophic waters.