Interactions between freshwater input, light, and phytoplankton dynamics on the Louisiana continental shelf

We examined the effects of freshwater flow and light availability on phytoplankton biomass and production along the Louisiana continental shelf in the region characterized by persistent spring–summer stratification and widespread summer hypoxia. Data were collected on 7 cruises from 2005 to 2007, and spatially-averaged estimates of phytoplankton and light variables were calculated for the study area using Voronoi polygon normalization. Shelf-wide phytoplankton production ranged from 0.47 to 1.75 mg C m⁻² d⁻¹ across the 7 cruises. Shelf-wide average light attenuation (k_d) ranged from 0.19–1.01 m⁻¹ and strongly covaried with freshwater discharge from the Mississippi and Atchafalaya Rivers (R²=0.67). Interestingly, we observed that the euphotic zone (as defined by the 1% light depth) extended well below the pycnocline and to the bottom across much of the shelf. Shelf-wide average chlorophyll a (chl a) concentrations ranged from 1.4 to 5.9 mg m⁻³ and, similar to k_d, covaried with river discharge (R²=0.83). Also, chl a concentrations were significantly higher in plume versus non-plume regions of the shelf. When integrated through the water-column, shelf-wide average chl a ranged from 26.3 to 47.6 mg m⁻², but did not covary with river discharge, nor were plume versus non-plume averages statistically different. The high integrated chl a in the non-plume waters resulted from frequent sub-pycnocline chl a maxima. Phytoplankton production rates were highest in the vicinity of the Mississippi River bird's foot delta, but as with integrated chl a were not statistically different in plume versus non-plume waters across the rest of the shelf. Based on the vertical distribution of light and chl a, a substantial fraction of phytoplankton production occurred below the pycnocline, averaging from 25% to 50% among cruises. These results suggest that freshwater and nutrient inputs regulate shelf-wide k_d and, consequently, the vertical distribution of primary production. The substantial below-pycnocline primary production we observed has not been previously quantified for this region, but has important implications about the formation and persistence of hypoxia on the Louisiana continental shelf.     

Vertical distributions of chlorophyll in deep, warm monomictic lakes

The factors affecting vertical distributions of chlorophyll fluorescence were examined in four temperate, warm monomictic lakes. Each of the lakes (maximum depth >80 m) was sampled over 2 years at intervals from monthly to seasonal. Profiles were taken of chlorophyll fluorescence (as a proxy for algal biomass), temperature and irradiance, as well as integrated samples from the surface mixed layer for chlorophyll a (chl a) and nutrient concentrations in each lake. Depth profiles of chlorophyll fluorescence were also made along transects of the longest axis of each lake. Chlorophyll fluorescence maxima occurred at depths closely correlated with euphotic depth (r ² = 0.67, P < 0.01), which varied with nutrient status of the lakes. While seasonal thermal density stratification is a prerequisite for the existence of a deep chlorophyll maximum (DCM), our study provides evidence that the depth of light penetration largely dictates the DCM depth during stratification. Reduction in water clarity through eutrophication can cause a shift in phytoplankton distributions from a DCM in spring or summer to a surface chlorophyll maximum within the surface mixed layer when the depth of the euphotic zone (z _eu) is consistently shallower than the depth of the surface mixed layer (z _SML). Trophic status has a key role in determining vertical distributions of chlorophyll in the four lakes, but does not appear to disrupt the annual cycle of maximum chlorophyll in winter.     

Distribution of dissolved free amino acids, dissolved inorganic nitrogen and chlorophyll a in the surface microlayer and subsurface water of the Yellow Sea, China

Concentrations of 14 different dissolved free amino acids (DFAA), dissolved inorganic nitrogen (DIN), and chlorophyll a were determined in the surface microlayer and subsurface waters at 41 stations in the Yellow Sea, China in April 2006. The concentrations of DFAA in the subsurface water ranged from 0.13 to 1.62 μM, with an average of 0.57±0.05 μM, while those in the surface microlayer varied between 0.22 and 2.6 μM, with an average of 0.94±0.08 μM. Major constituents of DFAA present in the study area were glycine, alanine, glutamic acid, serine and histidine. One-way analysis of variance (ANOVA) showed no significant difference in average mol fractions of DFAA between microlayer and subsurface water (F=0.0440, P=0.8355). Hierarchical cluster analysis of the station similarity based on the DFAA composition in both the surface microlayer and subsurface water separated three clusters of stations at the 70% Bray–Curtis similarity level. The average concentrations of chlorophyll a and DIN were 1.18 (0.34–4.44) μg L⁻¹ and 16.57 (3.98–49.59) μM in the subsurface water, and those in the surface microlayer were 1.30 (0.24–3.97) μg L⁻¹ and 18.56 (5.77–48.93) μM, respectively. Our results showed that concentrations of chlorophyll a (r²=0.7940, n=41, p<0.0001), DIN (r²=0.6939, n=41, p<0.0001) and DFAA (r²=0.2416, n=41, P=0.0011) in the microlayer were, respectively, correlated with their subsurface water concentrations, implying that there was a strong exchange effect between the microlayer and subsurface water. The enrichment factor of DFAA in the microlayer ranged from 0.47 to 2.24 with a mean of 1.88±0.16.     

Microcosm experiments on the effect of nutrient enrichment and a soil layer on the development of freshwater plankton

We investigated the response of phytoplankton and zooplankton to experimental alteration of nitrate and phosphate levels in outdoor enclosures. Experiments were conducted in summer and winter and in the absence and presence of a layer of soil. The tubs (12 in all) except the two plain water controls were manured initially with a mixture of fresh cowdung (50g 1⁻¹), mustard oil cake (25 g l⁻¹) and poultry wastes (25 g l⁻¹; mostly excreta), prior to enrichment. Water samples were collected from the experimental tubs twice a week to measure selected physico-chemical and biological variables. Water temperature in the summer experiments ranged from 20–30 °C and during the winter experiments from 11–15 °C. The pH values ranged from 8.0 to 9.5 and the dissolved oxygen levels from 8.2–10.0 mg l⁻¹. The levels of soluble reactive phosphorus and nitrate nitrogen ranged from undetectable levels to 1800 μg l⁻¹ and 6000 μg l⁻¹, respectively. The increase in chlorophyll-a following enrichment was rapid (3–7 days) during summer, but slower in winter (7–14 days). The predominant phytoplankton species observed in the tubs belong to the genera Sphaerocystis, Chlorella, Scenedesmus, Cosmarium, Ulothrix, Zygnema, Gonium and Pandorina. The rotifer species observed were Brachionus calyciflorus, Rotaria neptunia, Lecane bulla, L. luna, L. unguitata, Euchlanis dilatata, Asplanchna intermedia, Pseudoharringia spp., Eosphora spp., Lepadella ovalis, Epiphanes brachionus, Hexarthra mira and Cephalodella gibba. The cladocerans observed were Macrothrix spp. and Alona spp.     

Mathematical modeling of PCB bioaccumulation in Perna viridis

In the present work, we built a mathematical model of polychlorinated biphenyl (PCB) bioaccumulation in Perna viridis, namely, a one-compartment model with a time dependent incorporation rate R (μg g⁻¹ lipid per ppb water per day), with positive substrate cooperativity as the underlying physical mechanism. The temporal change of the PCB concentration Q (μg g⁻¹ lipid) in the soft tissues of the mussel depends on the competition of the input rate RW and the output rate kQ, where W is the concentration of PCB in water (ppb water) and k is the elimination rate (per day). From our experimental data, k=0.181±0.017 d⁻¹. The critical concentration in water W_c for positive substrate cooperativity was found to be 2.4 ppb. Below W_c, R is a constant. For a water concentration of 0.5 ppb Aroclor 1254, R=24.0±2.4 μg g⁻¹ lipid ppb⁻¹ d⁻¹. Above W_c, positive substrate cooperativity comes into effect and R becomes a function of time and dependent on the concentration Q in a form R=γQ/(Q+δ). This is the case for a water concentration of 5 ppb Aroclor 1254, where γ=15.1 μg g⁻¹ lipid ppb⁻¹ d¹ and δ≈200 μg g⁻¹ lipid. From this model, the uptake is exponentially increasing when the PCB concentration in the mussel is small compared to 200 μg g⁻¹ lipid, and hyperbolically increasing when the concentration is large compared to 200 μg g⁻¹ lipid, which are consistent with the experimental data. The model is useful for understanding the true processes taking place during the bioaccumulation and for risk assessment with higher confidence. Future experimental data which challenge the present model are anticipated and in fact desirable for improvement and perfection of the model.     

Sand transport and deposition within arrays of non-erodible cylindrical elements

The study concerns sand deposition within a regular array of vertical cylinders placed in the path of a sand-laden wind. Twelve wind tunnel experiments using three preselected shear velocities (28·78, 32·86 and 45·1 cm s⁻¹), with associated rates of sand feed (0·3, 2·0 and 3·8 g cm⁻¹ s⁻¹), and four roughness element concentrations (λ = 0·046, 0·092, 0·184 and 0·369) were carried out to evaluate the factors that affect sand deposition and sand flux in the presence of immobile rough elements. The measurements showed that as the concentration of non-erodible elements increased, the percentage reduction in the initial sand flux increased and a particularly sharp reduction occurred when λ ≥ 0·18. The pattern of reduction was found to be q_red = q_eq (d/H) [Δy/(Δy−d)](0·68 −3·5λ) when λ ≤ 0·18, and q_red = q_eq(d/H)[Δy/(Δy−d)](0·025) when λ > 0·18, where q_eq is the equilibrium rate of sand transport arriving at the best bed, d is the diameter of the cylinder, H is the height of the cylinder, and Δy is the width of unit area associated with a cylinder. The experimenal results also showed that the sand flux downstream of the array started to increase immediately upon the commencement of burial of the array's cylinders. Thus the sand deposition and sand flux along an array consisting of regularly distributed, non-erodible elements were shown to be neither uniform nor steady. Copyright © 1999 John Wiley & Sons, Ltd.     

湖北长湖富营养化状况及时空变化(2012-2013年)

为评估长湖水体富营养化程度,2012-2013年分4个季度对全湖区20个采样点的物理、化学和生物要素进行监测,在评价水质现状的基础上采用综合营养状况指数法和浮游植物细胞丰度指数法综合评价水体营养状况,并应用典型相关分析(CCA)方法揭示水体富营养化状况与湖泊理化要素之间的典型相关性.结果显示:4个季节长湖全湖区的水质均处于地表水IV类~劣V类水标准;综合营养状态指数值在49.54~82.55之间,浮游植物细胞丰度在2.88×106~61.73×106cells/L之间,均显示其处于富营养化状态;长湖富营养化状况的分布呈现一定的时空差异性;CCA分析显示,长湖理化要素变量可解释68.6%的水体富营养化状况变量的变异,影响其富营养化状况的主要理化因素有水体总磷、总氮、溶解氧、亚硝态氮、硝态氮浓度,水深和沉积物总磷、总氮含量.长湖水体富营养化主要是由于外源的磷污染,其次是氮污染,富营养化最严重的夏、秋季浮游植物的生长主要受氮营养限制,而冬、春季则部分受磷营养限制,部分属于过渡类型.因此,建议大力削减围网/围栏养殖量,同时考虑结合水生植物栽种等生态工程建设措施以降低长湖水体发生严重富营养化的风险,并进一步改善长湖的水质现状.     

Vertical distribution of plankton in the skagerrak in relation to doming of the seasonal thermocline

In the central Skagerrak between Norway and Denmark, the seasonal thermocline tends to be relatively shallow (10 to 15 m) probably due to geostrophic effects. An investigation of phytoplankton distribution in this region in late August 1981 showed the presence of an intense subsurface chlorophyll maximum (up to 30 γ 1⁻ Chl a) at a temperature of <6°C, dominated by coccolithophores and the dinoflagellate, Prorocentrum minimum. Data are presented on the vertical distribution of zooplankton in relation to these phytoplankton populations.     

江汉平原长湖浮游植物初级生产力的季节性变化及其驱动因子

为探究长江中下游富营养化浅水湖泊的浮游植物初级生产力季节性演替特征及其驱动因子,本研究于2020年4月(春)、8月(夏)、10月(秋)及2021年1月(冬)对湖北长湖浮游植物进行采样调查,同时运用黑白瓶测氧法及VGPM模型估算法分别估算了其浮游植物生产力水平,并探究驱动初级生产力季节性变化的主要环境因子。结果显示,4个季节共鉴定出浮游植物194种,其中绿藻门(95种,49%)和硅藻门(40种,21%)居绝对优势地位;黑白瓶法测得浮游植物水柱总生产力(P_t)季节变化为:夏季((1841.24±345.93) mg C/(m²·d))>秋季((1324.14±208.34) mg C/(m²·d))>春季((847.50±247.72) mg C/(m²·d))>冬季((711.43±133.52) mg C/(m²·d)),其中M2站位在夏季采样时(2424.66 mg C/(m²·d))水柱总生产力最高;在垂直空间上,浮游植物总生产力(G...     

白洋淀浮游植物群落的时空变化及其与环境因子的关系

浮游植物和环境因子是水生态中重要的组成部分,研究浮游植物与环境因子的相关关系可为白洋淀水资源管理及水生态保护提供理论基础.本研究于2018年非汛期(5月)和汛期(8月)分别对白洋淀淀区8个采样点的浮游植物及环境因子进行调查分析.采用Pearson相关性分析法筛选主要环境因子,分析白洋淀浮游植物群落结构变化和主要环境因子的分布特征,以及两者间的相互关系.结果表明,汛期主要环境因子为溶解氧(DO)、高锰酸盐指数(CODMn)、总氮(TN)和总磷(TP),非汛期主要环境因子为DO、CODMn、氨氮(NH_3-N)和TP.汛期和非汛期检出浮游植物分别为5门38种和6门43种,浮游植物丰度分别为415.30×10~5～1018.14×10~5cells/L和249.62×10~5～454.21×10~5cells/L,优势种分别为6种和10种,且基本为蓝藻和绿藻.浮游植物群落Shannon-Wiener多样性指数(H')、Margalef物种丰富度指数(d M)、Pielou均匀度指数(J)和物种多样性阈值4项指数均表明汛期浮游植物多样性小于非汛期.浮游植物群落特征与水质关联性较强,水质较好区域(如淀区中心) H'和J均较高,反之在水质较差区域(如府河、孝义河等汇入口) H'和J较低.TP和DO是影响汛期浮游植物群落特征的关键因素,CODMn和TP是影响非汛期浮游植物群落特征关键因素.水质评价结果表明白洋淀水质整体处于富营养状态,与2005年以来对白洋淀进行的3次浮游植物生态调查结果相比,淀区浮游植物多样性与均匀度显著下降,表明淀区富营养化程度持续加深.     

Conductivity as a predictor of a total cations and salinity in Ethiopian lakes and rivers: revisiting earlier models

We used regression analyses of water samples from 18 lakes, nine rivers, and one spring in Ethiopia to (a) test the hypothesis that water bodies of relatively higher salinity (K₂₅>1000 μS cm⁻¹) have a different conductivity to salinity relationship than waters of lower salinity (K₂₅ < 1000 μS cm⁻¹), and (b) develop models to predict total cations and salinity from conductivity that can be used for Ethiopian waters and other African aquatic systems of similar chemical composition. We found no statistical difference in the bilogarithmic relationships (total cations vs. conductivity; salinity vs. conductivity) for waters of higher salinity (K₂₅ > 1000 μS cm⁻¹) and waters of lower salinity (K₂₅ < 1000 μS cm⁻¹). However, comparison among our models and models from the literature suggests that developing separate equations for low and high salinity water bodies has some merit. We believe that the equations developed in this study can be used for Ethiopian waters and other African waters within the range of conductivity in this study.     

Auswirkungen des Ablassens von Hochwasserrückhaltebecken auf deren Limnochemie und Phytoplankton-Biozönose

Reservoirs have to be released when repairing of the dams is necessary. In 1995, two reservoirs in Baden-Württemberg (Germany) of similar age and volume (Lake Herrenbach near Göppingen, 1.0 Mio. m³ and Lake Breitenau near Heilbronn, 2.3 Mio. m³) were emptied. This allowed the singular possibility to investigate the effects of drainage and refilling on the limnochemistry and the phytoplankton biocoenosis of such artificial lakes.Before the drainage of the reservoirs, both lakes showed phosphorus release from the sediment during summer stagnation. Phosphorus values of Lake Herrenbach were regularly higher than those of Lake Breitenau (Lake Herrenbach 88 μg/l, Lake Breitenau 33 μg/l). During release, both lakes indicated higher phosphorus and chlorophyll concentrations as well as rising biomasses. Remarkable differences were observed during refilling of the reservoirs: while Lake Herrenbach showed higher transparency and lower phosphorus concentrations, Lake Breitenau progressed towards eutrophication (total phosphorus during summer 1996: Lake Herrenbach 30 μg/l, Lake Breitenau 55 μg/l). One reason for the reaction of Lake Breitenau was the reduced ground drainage during the refilling, which caused an accumulation of nutrients in the hypolimnion. Another reason was the mineralisation of vegetation which covered great parts of the dry lake sediment. The limnological change of Lake Herrenbach was not as clear but could be caused by the restauration of the pre-reservoir which was drainaged and dredged before the emptying of the main reservoir started as well as many other facts which differed Lake Herrenbach from Lake Breitenau.     

A hydrobiological study to interpret the presence of desmids in Lake Zirahuén, México

Monthly collections of phytoplankton were supported by physical–chemical data and measures of chlorophyll a concentrations in the search for particular environmental factors that could explain the constant presence of desmids in a Mexican tropical lake, a characteristic not common among the phytoplanktic communities of Mexican lakes. Samplings were taken from the water column in the deepest part of the lake (40 m) and intensified in the metalimnetic zone, whose establishment was monitored by observations of temperature and oxygen profiles. The general behavior of Lake Zirahuén was typical of warm monomictic tropical lakes at high elevation: a short mixing phase during the hemispheric winter. The depth of Z_MIX and Z_eu revealed a well-illuminated epilimnion, suggesting that phytoplankton communities are not likely to be light-limited. The oligotrophic nature of the lake is indicated by discrete concentrations of inorganic nutrients, P_TOT in the interval of 0.01–0.03 mg l⁻¹ and chlorophyll a between 0.23 and 3.98 μg l⁻¹. These characteristics together with a low concentration of calcium, define a lacustrine environment different from other Mexican lakes, and one that could be suitable for desmids communities.     

Bio-dependent bed parameters as a proxy tool for sediment stability in mixed habitat intertidal areas

The stability of cohesive and non-cohesive sediments in a mixed intertidal habitat within the Ria Formosa tidal lagoon, Portugal, was examined during two field campaigns as part of the EU F-ECTS project. The cohesive strength meter Mk III was used to determine critical erosion shear stress (τ_c) within a variety of different intertidal habitats and substrata, including Spartina maritima fields and Zostera noltii beds. The best predictor(s) for τ_c were derived from a range of properties measured for the surface sediments (chlorophyll a, colloidal carbohydrate, water, organic content, % fraction <63 μm, and seabed elevation). Pigment biomarkers were used to identify the dominant algal groups within the surface phytobenthic assemblage.Strong, seasonally dependent relationships were found between τ_c and habitat type, chl a, colloidal carbohydrate and bed elevation. Typically, critical erosion thresholds decreased seawards, reflecting a change from biostabilisation by cyanobacteria in the upper intertidal areas, to biostabilisation by diatoms on the bare substrata of the channel edges. In the late summer/early autumn, cyanobacteria were the main sediment stabilisers, and colloidal carbohydrate was the best bio-dependent predictor of τ_c across the entire field area. In the late winter/early spring, cyanobacterial activity was lower, and sediment stabilisation by Enteromorpha clathrata was important; the best predictor of τ_c was bed elevation. The implications and use of proxies for sediment stability are discussed in terms of feedback and sedimentation processes operating across the intertidal area.     

Nitrogen over enrichment in subtropical Pearl River estuarine coastal waters: Possible causes and consequences

Hong Kong is surrounded by estuarine, coastal and oceanic waters. In this study, monthly averages over a 10 year time series of salinity, temperature, chlorophyll a (chl a), dissolved oxygen (DO), dissolved inorganic nitrogen (DIN), silicate (SiO₄) and orthophosphate (PO₄) at three representative stations around Hong Kong were used to examine if excess nitrogen in estuarine influenced waters is due to P limitation. The monthly distribution clearly shows the dominant influence of the seasonal change in river discharge in the Pearl River estuary and adjacent coastal waters. In winter, the river discharge is small and more oceanic waters are dominant and as a result, salinity is high, and chlorophyll and nutrients are low. In summer, when the river discharge is high, salinity decreases and nutrients increase. DIN is very high, reaching 100 μM in the estuary. This indicates over enrichment of nitrogen relative to P and consequently there is an excess of N in coastal waters of Hong Kong. P remains low (∼1 μM) and can potentially limit both phytoplankton biomass and N utilization which was demonstrated in field incubation experiments. P limitation would result in excess N being left in the estuarine influenced waters south of Hong Kong. Phosphate concentration is lower in the Pearl River estuary than in many other eutrophied estuaries. Therefore, this relatively low PO₄ concentration should be a significant factor limiting a further increase in the magnitude of algal biomass and in the degree of eutrophication in the Pearl River estuary. The export of the excess N offshore into the northern South China Sea may result in an increase in the size of the region that is P limited in summer.     

Diapirism in the earth's mantle: Experiments on the motion of a hot sphere in a fluid with temperature-dependent viscosity

The ascent of magma diapirs through the earth's mantle is modelled experimentally by the motion of a hot metal sphere through a fluid whose viscosity varies strongly with temperature. The dimensionless drag on the sphere (drag number D) and the heat transfer from it (Nusselt number Nu) are found as functions of the dimensionless velocity of the sphere (Peclet number Pe) and the viscosity contrast μ_∞/μ₀ = 10^γ, where μ_∞ and μ₀ are the viscosities of the fluid far from the sphere and at its surface. The drag D = D(Pe, γ) has two limits. For large Pe and small γ (“Stokes” limit), the drag approaches the Stokes' Law result. For small Pe and large γ (“lubrication” limit), the drag is orders of magnitude less than that predicted by Stokes' Law. Nu is a function of Pe alone. For reasonable values of the diapir radius and the viscosity contrast, the dimensionless scale height Pe/3 Nu may exceed a critical value, resulting in progressive melting during ascent. This suggests that diapirs may ascend great distances through the mantle while remaining largely molten. Lamont-Doherty Geological Observatory Contribution No. 3414.     

哈尔滨西泉眼水库夏季浮游植物群落结构动态特征

西泉眼水库作为哈尔滨市第二水源地,事关居民的饮用水安全,而浮游植物群落特征则是水库生态系统健康状况监测与评估的重要研究内容之一,能为水库生态系统健康提供科学支撑.本研究设置13个采样点,对库区和入库河流的浮游植物群落进行对比分析,采样时间为蓝藻水华易发的7月和8月.经镜检,共鉴定浮游植物7门169种,其中绿藻门最多,83种,占总种数的49.11%;硅藻门次之,47种,占总种数的27.81%;蓝藻门15种,占总种数的8.88%;隐藻门最少,仅有2种.浮游植物丰度在10.92×105~88.44×105cells/L之间,均值为51.6×105cells/L,以8月的3#采样点最高;生物量在2.61~22.44 mg/L之间,均值为10.37 mg/L,以8月的5#采样点最高.Shannon-Wiener指数在2.46~4.69之间,均值为3.33,以7月12#采样点最高.研究水域浮游植物优势种群以梅尼小环藻(Cyclotella meneghiniana)、肘状针杆藻(Synedra ulna)、阿氏席藻(Phormidium allorgei)和游丝藻(Planctonema sp.)为主.同时,典范对应分析表明:1)既将西泉眼水库库区和入库河流区分为两个相对独立的生态系统,又展现了同一生态系统内的月份变化趋势,说明西泉眼水库库区和入库河流区的浮游植物群落的时空分布异质性显著;2)库区内河流入库口处、库心和大坝口处浮游植物群落梯级差异显著,入库河流区水质明显优于库区;3)氨氮、硝态氮、总氮和总磷是影响浮游植物种群的主要驱动因子.研究认为,西泉眼水库水体总体上已处于中度富营养水平,并存在进一步富营养化的风险.建议水库管理部门建立水生态系统健康监测与评估预警体系,配套相应的水生态管理制度,并采取适宜的生态修复技术等生态治理措施,以确保哈尔滨市供水水源安全.     

The impact of pelagic (Daphnia longispina) and benthic (Dreissena polymorpha) filter feeders on chlorophyll and nutrient concentration

An outdoor experiment testing the effect of water flea (Daphnia longispina) and zebra mussels (Dreissena polymorpha) on physical and chemical water parameters and chlorophyll concentration changes was carried out in 12 containers filled with 150 l of unfiltered water from a lowland reservoir. During the 11 weeks of the experiment, the following physical, chemical and biological measurements were recorded: temperature (°C), oxygen concentration (mg dm⁻³), pH, conductivity (S cm⁻¹), concentration of phosphate phosphorus (PO₄-P) and ammonia nitrogen (NH₄-N) (g dm⁻³), total nitrogen (TN) and total phosphorus (TP) (g dm⁻³), phytoplankton community structure and chlorophyll a concentration (g dm⁻³). The amount of ammonia ions was the highest in the treatment with zooplankton, while phosphate ions reached the highest values in treatments with zebra mussels. The results confirmed the ability of Daphnia to increase the NH₄:PO₄ ratio, whereas excretion from zebra mussels resulted in a decrease in both the N:P ratio (ranging from 9 to 13) and the NH₄:PO₄ ratio in water. In both treatments containing zebra mussels, P-rich water enabled sudden growth of Chlorophyta, resulting in blooms of Hydrodictyon reticulatum after 3–4 weeks of the experiment. Such phenomena were not observed in the control and Daphnia treatments. Our results indicate that zebra mussels, in contrast to Daphnia, may increase the symptoms of water eutrophication and contribute to blooms of expansive phytoplankton species.