Seasonal Succession Of Phytoplankton Research Articles

Survival strategies of phytoplankton functional groups to environmental factors in a drinking water reservoir, central China

In this study, use survival strategies of phytoplankton functional groups to environmental factors in a drinking water reservoir. Survival strategies of phytoplankton in drinking water reservoirs were rarely analysed. Dynamics and survival strategies of phytoplankton community in Zhushuqiao Reservoir (Changsha, China) were studied bimonthly from April 2016 to February 2017 to fill this gap. In spring, species of CRS-strategy that adapted to low water temperature, light, and nutrient dominated. There were small individuals of opportunistic colonists of C-strategy observed before stratification. With the increase of nutrient and water temperature in summer, slightly bigger, disturbance-tolerant species of R-strategy and species of CS-strategy that adapted to stratification dominated. In winter, some species adapted to low water temperature, which were R-strategists. Key factors driven seasonal phytoplankton succession were water temperature, total phosphorus, and dissolved inorganic nitrogen. Attention should be paid to potential threats from algal bloom species with C-strategy, and future longer-term monitoring of the system and its surrounding watersheds is greatly needed.

Seasonal and Inter-Annual Variability of the Phytoplankton Dynamics in the Black Sea Inner Basin

We explore the patterns of Black Sea phytoplankton growth as driven by the thermohaline structure and circulation system and the freshwater nutrient loads. Seasonal and inter-annual variability of the phytoplankton blooms is examined using hydrodynamic simulations that resolve mesoscale eddies and online coupled bio-geochemical model. This study suggests that the bloom seasonality is homogeneous across geographic locations of the Black Sea inner basin, with the strongest bloom occurring in winter (February–March), followed by weaker bloom in spring (April–May), summer deep biomass maximum (DBM) (June–September) and a final bloom in autumn (October–November). The winter phytoplankton bloom relies on vertical mixing of nitrate from the intermediate layers, where nitrate is abundant. The winter bloom is highly dependent on the strength of the cold intermediate layers (CIL), while spring/summer blooms take advantage of the CIL weakness. The maximum phytoplankton transport across the North Western Shelf (NWS) break occurs in September, prior to the basin interior autumn bloom. Bloom initiation in early autumn is associated with the spreading of NWS waters, which in turn is caused by an increase in mesoscale eddy activity in late summer months. In summary, the intrusion of low salinity and nitrate-rich water into the basin interior triggers erosion of the thermocline, resulting in vertical nitrate uplifting. The seasonal phytoplankton succession is strongly influenced by the recent CIL disintegration and amplification of the Black Sea circulation, which may alter the natural Black Sea nitrate dynamics, with subsequent effects on phytoplankton and in turn on all marine life.

Seasonal succession of phytoplankton in two temperate artificial lakes with different water sources.

To explore the seasonal succession and drivers of phytoplankton communities in Guanzhong, Shaanxi Province, China, the water quality and phytoplankton communities in two typical waterbodies (Juehe Wetland Park in Xian and Xiaoxihu Lake in Xianyang) were monitored from 31 August 2017 to 31 July 2018. We identified 43 genera of phytoplankton from 7 phyla in Juehe Wetland Park and 45 genera of phytoplankton from 7 phyla in Xiaoxihu Lake. Phytoplankton communities in the two waterbodies showed significant patterns of seasonal succession. Cyanophyta (Microcystis spp.) dominated in August-September 2017 in Juehe Wetland Park, and Bacillariophyta (Navicula spp.) dominated in October 2017-July 2018. Cyanophyta (Microcystis spp.) dominated in Xiaoxihu Lake in August-November 2017, and Bacillariophyta (Synedra spp.) dominated in December 2017-July 2018. Redundancy analysis (RDA) showed that the temperature and total phosphorus were closely related to the seasonal succession of Cyanophyta and Bacillariophyta. In addition, the temperature, dissolved total phosphorus, and total phosphorus were closely related to the seasonal succession of Microcystis spp., Navicula spp., and Synedra spp.

Marked spatiotemporal variations in small phytoplankton structure in contrasted waters of the Southern Ocean (Kerguelen area)

AbstractIn the Southern Ocean, diatom blooms have attracted a lot of attention, while other small nonsilicified phytoplankton groups have been less studied. Here, small phytoplankton (< 20 μm, including small diatoms and nonsilicified small phytoplankton) are focused on in two contrasting areas: the productive Kerguelen plateau and its surrounding low productivity waters. To assess the diversity and spatial structuration of phytoplankton, discrete plankton samples (0–300 m layer) of two size fractions (< 20 and 20–100 μm) were analyzed with 18S rDNA amplicon sequencing in late summer. Phytoplankton seasonal succession was described using flow cytometry, pigments, and environmental data, from two previous cruises (during the onset and decline of the diatom bloom). In the mixed layer, small nonsilicified phytoplankton represented less than 10% of chlorophyll a (Chl a) during the onset and late diatom bloom on the plateau, but they increased on and off the plateau after the bloom (53–70% of Chl a). Phaeocystis antarctica was relatively abundant at all stations after the bloom, but other small phytoplanktonic groups featured marked differences on and off the plateau. Higher concentrations on the plateau appeared to stimulate the presence of Micromonas, while Pelagophytes were enhanced off the plateau. A diverse assemblage of small diatoms was also promoted off the plateau, where silicate concentration was still high. Interestingly, P. antarctica represented up to 25% of all reads at 300 m depth off the plateau in the larger size fraction suggesting a significant contribution to carbon export through aggregation in low productive waters.

Seasonal phytoplankton succession in Netravathi – Gurupura estuary, Karnataka, India: Study on a three tier hydrographic platform

The Netravathi-Gurupura estuary is a tropical, micro to meso-tdal estuary situated at Mangalore, southwest coast of India. The estuary outlets into the Arabian Sea and it is regarded as one of the major upwelling systems of India. Our study focusses on the seasonal phytoplankton succession in Netravathi-Gurupura estuary through studying the hydrochemical and hydrobiological physiognomies of riverine, estuarine and marine components. Hypoxic conditions prevailed at the estuarine zone during monsoon seasons (D.O.< 3 mg L−1). Salinity was very low in the estuarine and marine zone during the 2018 monsoon season and hefty silicate loadings (>100 μmol L−1) contributed to the proliferation and blooming of diatoms like Skeletonema costatum in the estuary. A strong negative correlation between phytoplankton composition and silicate was observed during the 2018 monsoon season (r = −0.977). The substantial entrainment of TDS (>10000 ppm), relatively higher salinity (33–35 psμ) and high values of TN: TP (42.0–67.0 μmol L−1) and proliferation of dinoflagellates were the characteristics of non-monsoon seasons. A significant positive association of phytoplankton was observed with NO3 (r = 0.989) and TN: TP (r = −0.997). In terms of phytoplankton species diversity, our study classifies estuarine zone as least diverse zone, particularly during the 2018 monsoon season (D > 0.55, 1/D < 1.82). Phytoplankton succession from diatoms (monsoon) to dinoflagellate (non-monsoon) is attributed to the alteration in physic-chemical and nutrient parameters as a function of seasonal variation.

Phytoplankton community, structure and succession delineated by partial least square regression in Daya Bay, South China Sea.

Daya Bay is facing the influence of human activities and nature changes, which result in phytoplankton adjusting to the changing environment. The data about environmental changes and phytoplankton were obtained from four seasonal cruises in 2013 in the bay. It is helpful to explore seasonal succession of phytoplankton driven by the determining environmental factors in this bay. Temperature is a significant indicator of season change. The limiting factor of phytoplankton growth totally changed from P (PO4-P) limiting during the southwest monsoon to Si (SiO3-Si) limiting during northeast monsoon. The order of diatoms and dinoflagellates was the dominant phytoplankton groups in Daya Bay. The dominant species included chain-forming diatoms (Skeletonema, Pseudo-nitzschia, Thalassionema, Chaetoceros and Rhizosolenia) were found all the year round and filamentous cyanobacteria (Trichodesmium) in spring and autumn. Partial least square regression (PLS) found that salinity, temperature and nutrients were important driving force for phytoplankton seasonal succession.

Composition and Seasonal Succession of Phytoplankton of Taganrog Bay in the Sea of Azov and the Downstream Reaches of the Don River under a Changing Climate

The results of a study of phytoplankton in Taganrog Bay in the Sea of Azov and the downstream reaches of the Don River carried out in January–November 2017 are presented. A total of 210 species of eukaryotic algae and cyanoprokaryotes are identified. An analysis of the taxonomic, ecological, and geographical composition of the plankton algal flora and seasonal dynamics of biomass of phytoplankton taxonomic and size structures has revealed no changes in the ratio of large taxonomic and ecological–geographic groups in the algal flora when compared with previous years (1980s to early 2000s). However, the proportion of myxotrophic phytophagellates, cyanoprokaryotes from the planktotrichet complex, and small species increased in algal communities. It is shown that the water salinity is the main factor influencing the formation of species richness and total biomass and structure of phytoplankton. The maximum diversity and biomass of phytoplankton are recorded in the horohalinicum zone.

Seasonal variation of phytoplankton community and its relationship with environment in subtropical reservoirs: A comparison between two methods of functional groups classification

Phytoplankton is the most important biological component in the reservoir ecosystem, which could indicate the status of aquatic ecosystem due to its sensitive to environmental variation. To understand the application and difference between two methods of phytoplankton functional group classification, functional groups (FG) and morphology-based functional groups (MBFG), in indicating the changes of reservoir environment, we investigated water quality and phytoplankton in Qingshitan Reservoir monthly from March 2016 to February 2017. Two phytoplankton functional groups classifications (FG and MBFG) were used to analyze phytoplankton community composition, seasonal succession, and its driving factors. We compared the application and differences of two methods of functional group classifications in indicating environmental changes. The results showed that there were 109 species belonged to seven phylum, which could be classified into 17 FG or 5 MBFG functional groups. Results from both methods indicated that the reservoir was meso-eutrophic. The phytoplankton seasonal succession under 8 or 9 steps with FG or 8 steps with MBFG. Results from the redundancy analysis showed that the response of phytoplankton community reflected with FG to environmental variation was more sensitive than that with MBFG, especially in the response to the changes of pH and nitrate concentration. In conclusion, FG was more appropriate in describing community succession and exploring the relationship between phytoplankton and environment.

Фитопланктон в различных экотопах озера Отстойник (Самарская область)

This article presents the results of the study of the species composition and main indicators of the quantitative development of phytoplankton in various ecotopes (pelagic zone, phytal zone) of Lake Otstoynik. It is a small pond belonging to the system of Vasilievsky lakes of Togliatti, Samara Oblast. Initially it served as a receiver of nitrogen fertilizer production waste. In the 90s of XX century, the technological use of this lake was terminated but the rehabilitation works to restore the ecosystem of the reservoir was not carried out. Modern condition of the ecosystem is entirely the result of self-purification and self-healing. Therefore, the materials presented in this article may be of interest to experts on environment, especially those who work in the field of cost-benefit analysis in predicting the development of a "zero" scenario, i.e. without interference through recreational activities in the recovery processes of disturbed aquatic ecosystems. The study deals with the species composition of the plankton algoflora in various ecotopes of the reservoir (open pelagic zone and phytal zone formed by reed), its floral and еcological/geographical analysis. In addition, it considers seasonal succession of phytoplankton in different ecotopes in the period from 2014 to 2016, analyzes quantitative indicators of development (abundance, biomass) of phytoplankton, the role of the major divisions of algae in their formation. We estimated the level of species diversity in different ecotopes of the reservoir with the use of the Shannon-Weaver index. In terms of quantitative development of phytoplankton, the level of water trophies was estimated. Based on the data of sapro/biological analysis, the pollution level has been established and the class of water quality in the investigated water body has been determined.

Assessment of Spatiotemporal Phytoplankton Composition in Relation to Environmental Conditions of Gorgan Bay, Iran

Phytoplankton seasonal succession and spatial distribution were studied in Gorgan Bay, Iran, which is a semi-enclosed bay located in the southeastern Caspian Sea. Monthly phytoplankton and physicochemical samples were taken from March 2014 to September 2015. A total of 51 genera from six algal divisions were observed with phylum Bacillariophyta being the most represented (16 genera and on average ~ 59% of biomass). While diatoms were prevalent year-round, strong inter-seasonal variations of other phytoplankton groups were observed in response to environmental parameters. The seasonal succession of other taxa started with Chlorophyta (Chlorella sp.) in spring followed by Cyanophyta (Anabaena sp. and Microsystis sp.) and Euglenophyta (Euglena sp.) in summer, then Chrysophyta (Syndera) and Pyrrophyta (Prorocentrum sp., Exuviella sp., and Peridinium sp.) in the autumn and winter. The sites near the mouth of Gorgan Bay were characterized by slightly higher salinity with an annual mean of ~ 12 PSU compared with ~ 11 PSU for inner regions of the bay. Nitrate was higher in the mouth of the bay as well, with an annual mean of ~ 1.4 ppm compared with ~ 0.80 ppm in the inner region. Orthophosphate was also higher in the mouth of the bay with an annual mean of ~ 0.30 ppm compared with ~ 0.23 ppm in inner part of the bay. Euglena sp. and Microsystis sp. performed better in the mouth of the bay compared with their performance in the inner regions. Nutrients and salinity correlated strongest with phytoplankton in Gorgan Bay. During the period when Cyanophyta biomass was maximum, Microsystis sp. was the dominant taxa of the cyanobacteria present. Inorganic pollution from domestic wastewater in the eastern part of Gorgan Bay appears to be the cause of the Euglena maximum. According to the Palmer pollution index, Gorgan Bay experienced pollution from agricultural discharge and domestic wastewater.

Beyond Eutrophication: Vancouver Lake, WA, USA as a Model System for Assessing Multiple, Interacting Biotic and Abiotic Drivers of Harmful Cyanobacterial Blooms

Eutrophication of lakes and reservoirs has contributed to an increase in the magnitude and frequency of harmful cyanobacterial blooms; however, the interactive effects of nutrient availability (eutrophication) and other abiotic and biotic drivers have rarely been comprehensively studied in the field. We undertook an eight-year (2005–2013) research program that assessed the interaction of multiple factors driving cyanobacterial blooms in Vancouver Lake, a large, shallow eutrophic lake in Washington, USA. Our program consisted of nearly continuous monthly or weekly monitoring of water quality and plankton community composition over eight years, as well as multiple zooplankton grazing experiments over three years. We found a relatively consistent seasonal succession of phytoplankton and zooplankton assemblages, and a pattern of interacting factors influencing cyanobacterial bloom dynamics. Typically, a combined effect of decreased dissolved inorganic nitrogen (N), a sudden increase of dissolved inorganic phosphorus (P), and a cascading effect of zooplankton grazing created a ‘perfect storm’ of conditions that promoted the rapid proliferation of cyanobacteria over the two to three weeks before a bloom. At the blooms’ peaks, cyanobacterial carbon biomass reached as high as 20 µg L−1, with total [chl a] often exceeding 750 µg L−1. In the weeks following the blooms’ peaks, [PO4-P] and [NH4-N] dropped and copepod feeding rates fell to near zero, whereas microzooplankton grazing rates reached their maxima. Microzooplankton grazing impact, combined with low nutrient availability, then drove down cyanobacteria abundance. Vancouver Lake serves as a model for understanding multiple, interacting drivers of cyanobacterial bloom dynamics in shallow, temperate lakes, and is therefore an important system in which to investigate new questions related to the science and management of harmful algal blooms.

Ice algal communities in the Chukchi and Beaufort Seas in spring and early summer: Composition, distribution, and coupling with phytoplankton assemblages

AbstractTo understand the controls on distributions of ice algal communities in spring and the role of ice algae in under‐ice bloom development through possible seeding, we sampled the ice and water column in the Chukchi and Beaufort Seas over spring and summer. Field observations showed that high springtime concentrations of bottom ice algal communities were released from the ice into the water column by summer. Furthermore, during our spring sampling, bottom ice algal concentrations were highly variable. Declines in spring ice algal biomass and physiological state were correlated with ice melt, rather than light or nutrient availability. Nonparametric multivariate data analysis of the seasonal succession of phytoplankton and ice algal community composition illustrated that the loss of algae from the sea ice temporarily elevated water column chlorophyll a (Chl a) levels, as ice‐derived taxa dominated the phytoplankton biomass. Model simulations, constrained by field observations from this study, further suggested that seeding by ice algae was brief and alone could not account for the phytoplankton biomass concentrations exceeding 2 mg Chl a m−3 observed in our study. Ice algal sloughing from the sea ice to the water column contributes biomass to the phytoplankton community. However, this signal of ice‐derived taxa is brief and non‐ice derived taxa dominate phytoplankton blooms later in the spring and summer.

Plasticity in phytoplankton annual periodicity: an adaptation to long-term environmental changes

Because phytoplankton communities exhibit seasonal patterns driven by changes in physical factors, grazing pressure, and nutrient limitations, climate change, in combination with local phosphorus management policies are expected to impact phytoplankton annual dynamic. We used long-term monitoring data from Lake Geneva (from 1974 to 2010) to test if changes in phytoplankton seasonal succession across years is related to re-oligotrophication, inter-annual variability in thermal conditions, and Daphnia sp. density. We used a Bayesian method to identify species assemblages and wavelet analysis to detect transient dynamics in seasonal periodicity. A decrease in phosphorus concentrations appeared to play a major role in the inter-annual replacement of species assemblages. Furthermore, some species assemblages exhibited a change in their seasonal periodicity that was most likely induced by changes in Daphnia sp. density. Finally, we demonstrated that flexibility in the pattern of phytoplankton seasonal successions played a stabilizing role at the community level. The results suggest that phenology and inter-annual changes in seasonal dynamics of phytoplankton assemblages are important components to consider for explaining long-term variability in phytoplankton community.

Use the predictive models to explore the key factors affecting phytoplankton succession in Lake Erhai, China.

Increasing algae in Lake Erhai has resulted in frequent blooms that have not only led to water ecosystem degeneration but also seriously influenced the quality of the water supply and caused extensive damage to the local people, as the lake is a water resource for Dali City. Exploring the key factors affecting phytoplankton succession and developing predictive models with easily detectable parameters for phytoplankton have been proven to be practical ways to improve water quality. To this end, a systematic survey focused on phytoplankton succession was conducted over 2years in Lake Erhai. The data from the first study year were used to develop predictive models, and the data from the second year were used for model verification. The seasonal succession of phytoplankton in Lake Erhai was obvious. The dominant groups were Cyanobacteria in the summer, Chlorophyta in the autumn and Bacillariophyta in the winter. The developments and verification of predictive models indicated that compared to phytoplankton biomass, phytoplankton density is more effective for estimating phytoplankton variation in Lake Erhai. CCA (canonical correlation analysis) indicated that TN (total nitrogen), TP (total phosphorus), DO (dissolved oxygen), SD (Secchi depth), Cond (conductivity), T (water temperature), and ORP (oxidation reduction potential) had significant influences (p<0.05) on the phytoplankton community. The CCA of the dominant species found that Microcystis was significantly influenced by T. The dominant Chlorophyta, Psephonema aenigmaticum and Mougeotia, were significantly influenced by TN. All results indicated that TN and T were the two key factors driving phytoplankton succession in Lake Erhai.

Spatiotemporal Variations of Chlorophyll a and Its Relationship to Environmental Factors in Shiyan Reservoir

The spatial-temporal characteristics of chlorophyll a concentration[ρ(Chla)] were analyzed in Shiyan Reservoir, based on the monthly monitoring data from April 2013 to June 2014. The correlation between ρ(Chla) and key environmental factors were also studied using correlation analysis and canonical correspondence analysis.The results showed that ρ(TChla) was 9.59-123.29 μg·L-1, with an average of 52.03 μg·L-1. The ρ(Chla) of cyanobacteria was 4.54-76.30 μg·L-1, with an average of 28.39 μg·L-1. The ρ(Chla) of bacillariophyta was 3.16-46.09 μg·L-1, with an average of 15.02 μg·L-1. The ρ(Chla) of chlorophyta was 0.77-26.2 μg·L-1, with an average of 8.62 μg·L-1. Cyanobacteria was the primary species from April to December in 2013 and May, June in 2014 while bacillariophyta was the primary species in other months. The spatial heterogeneity of ρ(Chla) was unconspicuous and ρ(Chla) decreased gradually from south to north. There was a risk of algal blooming for the whole reservoir during flood season and south part of reservoir in autumn. The storm runoff pollutant washout was the leading cause of the spatial heterogeneity of ρ(Chla) in Shiyan Reservoir. Analysis revealed that water temperature was the most important driving factor for seasonal succession of phytoplankton. Significant correlation was found between ρ(Chla) and surface runoff in flood season. TN:TP was negatively related to phytoplankton biomass and phosphorus was the restrictive factor for phytoplankton. Cyanophyta were affected water temperature, TOC, TN, pH, transparency, turbidity and NO3--N. However silicate, TOC, NO3--N, and COD were the main environmental factor of bacillariophyta while TOC, COD, pH, transparency and NO3--N were the main factor of chlorophyta.

Assessing nature and dynamics of POM in transitional environment (the Curonian Lagoon, SE Baltic Sea) using a stable isotope approach

The nature of the particulate organic matter (POM) as well as its temporal and spatial distribution and dynamics in the Curonian Lagoon (south-eastern part of the Baltic Sea) were investigated. The organic matter was characterized by the organic carbon and nitrogen content, δ13C and δ15N signatures as well as POC/Chl-a and C/N ratios. Additionally, data on hydrological, chemical and biological parameters were used for better understanding the POM distribution and dynamics. The sampling was performed at 13 stations in the Curonian Lagoon and its outflow in the Baltic Sea during the 2012–2013 period. Samples were also collected at the Nemunas River mouth in order to test the riverine impact. Obtained results showed that isotopic values of carbon and nitrogen ranged from −36.1‰ to −25.2‰ and from −0.9‰ to 15.5‰, respectively. The isotopic composition, together with the low C/N molar (∼7) and POC/Chl-a ratios (<100) of the POM, suggested the dominance of living phytoplankton in POM throughout the year with the higher input of detrital material (C/N >10, POC/Chl-a ratios >100) in late autumn − winter.The results of multivariate analysis evidenced a spatial distinction of POM distribution in the northern-transitional and central confined areas and allowed us to distinguish the main driving factors. The seasonal variation of the δ13C and δ15N values in POM (towards higher δ13C and lower δ15N values in the summer − early autumn period and lower δ13C and higher δ15N values in the late autumn − spring period) was determined by combination of factors such as availability of inorganic carbon and nitrogen, the riverine discharge, seasonal phytoplankton succession and by the short-term saline water intrusion to the northern-transitional part of the lagoon.

Basin-scale spatio-temporal variability and control of phytoplankton photosynthesis in the Baltic Sea: The first multiwavelength fast repetition rate fluorescence study operated on a ship-of-opportunity

This study presents the results of the first field application of a flow-through multi-wavelength Fast Repetition Rate fluorometer (FRRF) equipped with two excitation channels (458 and 593nm). This device aims to improve the measurement of mixed cyanobacteria and algae community's photosynthetic parameters and was designed to be easily incorporated into existing ferrybox systems. We present a spatiotemporal analysis of the maximum photochemical efficiency (Fv/Fm) and functional absorption cross section (σPSII) recorded from April to August 2014 on a ship-of-opportunity commuting twice per week between Helsinki (Finland) and Travemünde (Germany). Temporal variations of Fv/Fm and σPSII differed between areas of the Baltic Sea. However, even though the Baltic Sea is characterized by several physico-chemical gradients, no gradient was observed in Fv/Fm and σPSII spatial distribution suggesting complex interactions between biotic and abiotic controls. σPSII was sensitive to phytoplankton seasonal succession and thus differed according to the wavelength used to excite photosystems II (PSII) pigments. This was particularly true in summer when high σPSII(593) values were observed later and longer than high σPSII(458) values, reflecting the role of cyanobacteria in photosynthetic light uptake measured at community scale. In contrast, Fv/Fm variations were similar after excitation at 458nm or 593nm suggesting that the adjustment of Fv/Fm in response to environmental factors was similar for the different groups (algae vs. cyanobacteria) present within the phytoplankton community.

Effects of winter severity on spring phytoplankton development in a temperate lake (Lake Erken, Sweden)

Phytoplankton seasonal succession has been linked to a variety of serial environmental changes, especially weather- and climate-induced physical forcing. This study compared spring phytoplankton dynamics after winters of different severity (cold, normal, and warm) in Lake Erken, Sweden. The spring diatom bloom was dominated by different functional groups: group A (centric diatoms 5–10 μm) after cold winters, B (centric diatoms >15 μm) after normal winters, and P (Aulacoseira granulata, Fragilaria crotonensis) after warm winters. Our results suggest that weather-related processes were the primary external drivers accounting for differences in spring phytoplankton dynamics in Lake Erken. Spring phytoplankton are influenced by overwintering species from the last autumn that can initiate the following spring bloom. Average taxonomic distinctness of the spring community was assessed using a new biodiversity measurement that incorporates taxonomic relatedness information. This value was lower than expected after warm and cold winters, which had winter air temperature 1°C deviation from an average value calculated over 21 years. Such winters increased the level of disturbance or stress to the lake, resulting in a spring with less diverse phytoplankton by narrowing the niche for species with various ecological requirements.

Modeling the response of phytoplankton to reduced external nutrient load in a subtropical Chinese reservoir using DYRESM-CAEDYM

Cui Y, Zhu G, Li H, Luo L, Cheng X, Jin Y, and Trolle D. Modeling the response of phytoplankton to reduced external nutrient load in a subtropical Chinese reservoir using DYRESM-CAEDYM. Lake Reserv Manage. 32: 146--157.The DYRESM-CAEDYM model was used to quantify the potential effects of reductions in external nutrient loads to the Shahe Reservoir in China, with an emphasis on effects on phytoplankton biomass. DYRESM-CAEDYM was calibrated using field data for a 2-year period and validated against a separate 1-year period. Simulated values for water temperature, dissolved oxygen, total nitrogen, total phosphorus, and chlorophyll a showed good agreement with field measurements. The model tended to underestimate peak values of inorganic nutrients such as ammonium, nitrate, and phosphate, with phosphate levels close to detection limits in both observed and simulated values. The model successfully captured seasonal phytoplankton succession, indicating spring peaks of diatom biomass and summer peaks of cyanophytes. Scenarios in which different reductions in external loading were applied suggest that simultaneous reductions in both external nitrogen and external phosphorus loading is more effective in controlling phytoplankton biomass than reducing input of either nutrient alone. Diatoms responded more strongly to load reductions in phosphorus input than nitrogen load, whereas cyanophytes showed the opposite pattern. A combined 25% reduction in the external loading of both nutrients could significantly decrease phytoplankton biomass in the reservoir below the 7 μg/L chlorophyll a required by drinking water standards, and the study indicated that DYRESM-CAEDYM can be a useful management tool for eutrophication control.

Using wavelet analyses to examine variability in phytoplankton seasonal succession and annual periodicity

Using wavelet analyses to examine variability in phytoplankton seasonal succession and annual periodicity