The human impact in the German Bight: Eutrophication during three decades (1962–1991)

The human impact in the German Bight, in the form of anthropogenic eutrophication, has been documented by a 30-year time-series measurement near the island of Helgoland. Since 1962, the Biologische Anstalt Helgoland has measured inorganic nutrients and phytoplankton abundance from daily samples at Helgoland Roads, a position 60 km off the main source of eutrophication, the River Elbe. Since the early sixties, phosphate concentrations rose for about a decade, levelling off to about twice the former concentrations for another decade, and then decreasing (since 1982) as a result of phosphate-reducing measures. Nitrate concentrations, however, have only increased since 1980/81, following Elbe river flood events. In 1987, three times the former concentrations were reached. A decrease has been observed only since 1991. This different development of phosphorus and nitrogen eutrophication led to a shift of inorganic N/P-ratios in the German Bight. The phosphate increase was more pronounced in the late summer “regeneration mode” conditions, the nitrate increase in the winter months. The eutrophication is not restricted to the inner German Bight and coastal waters of a salinity of <33, but has also occurred in more saline waters at S>33 psu (practical salinity unit), as characteristic for the outer German Bight. In this more saline water, phosphate and nitrate maximum levels occurred three years later, compared with the average Helgoland data, which are more representative of the inner German Bight. It is suggested that suspended particulate organic matter, as a long-distance carrier of nutrients, might have caused this delayed eutrophication in the outer German Bight waters. While the human impact is obvious as to nutrient concentrations, it is less obvious in phytoplankton stock enhancement. A general increase in phytoplankton biomass (about 3–4 times) was found, but this was mainly due to unidentified nanoflagellates of unknown trophic state, and subject to methodological errors. The causal relationships of phytoplankton stocks and eutrophication are not clearly understood, as natural variability is large and hydrographical factors possibly dominate. Additional nutrient input by Elbe river floods did not always result in elevated phytoplankton stocks near Helgoland, while extended periods of vertical density stratification of the German Bight water caused large plankton blooms.     

Larvae of uncommon caridean decapods in the German Bight: Species composition,distribution and abundance

Typically, the most abundant group of shrimp larvae in the German Bight is formed by representatives of the family Crangonidae. Larvae of the remaining species have been largely ignored, and only scarce information concerning their ecology is available. Thus, the purpose of the present study was to determine the species composition, distribution and abundance of noncrangonid shrimp larvae in the German Bight in July 1990, after the mildest winter of the century. The material is based upon plankton samples collected at 77 stations, covering the entire German Bight. Eight species were identified, as well as larvae of Palaemonidae andProcessa-juveniles.Processa nouveli holthuisi (53.0%) andP. modica (31.3%) were predominant in the collection. The distribution of the two species was clearly separated: the main concentration ofP. nouveli holthuisi (peak concentration of 1.94 larvae per m³) was confined to the northwest corner of the German Bight, while a majority ofP. modica larvae (peak concentration of 0.54 larvae per m³) occurred at the southwesterly stations. The spatial distribution ofCaridion steveni andEualus occultus around Helgoland indicates the presence of an adult population at the only rocky island in the study area. Other taxa, such as larvae of Palaemonidae and juvenilePandalina brevirostris were collected exclusively in estuarine habitats. Based upon both the results of the present study and comparable data, we conclude that developmental stages of ten non-crangonid species, as well as representatives of Palaemonidae, can be expected to occur in the plankton of the German Bight. The extremely mild temperatures of the preceding winter may have been, in part, responsible for the relatively high densities of some taxa encountered during our plankton survey. We assume that warm winter temperatures favour the immigration, reproduction and survival of cold-sensitive species.     

Helgoland Roads meso- and macrozooplankton time-series 1974 to 2004: lessons from 30 years of single spot,high frequency sampling at the only off-shore island of the North Sea

The Helgoland Roads meso- and macrozooplankton time-series 1974 to 2004 is a high frequency (every Monday, Wednesday and Friday), fixed position monitoring and research programme. The distance to the coastline reduces terrestrial and anthropological disturbances and permits the use of Helgoland Roads data as indicators of the surrounding German Bight plankton populations. The sampling, determination and IT methodologies are given, as well as examples of annual succession, and inter-annual population dynamics of resident and immigrant populations. Special attention is given to the phenology and seasonality of zooplankton populations. The influence of winter sea surface temperature on the seasonality of spawning of the common sole Solea solea is given as an example for merozooplankton populations.Communicated by K. Wiltshire     

Extending the phytoplankton tool kit for the UK Water Framework Directive: indicators of phytoplankton community structure

The Water Framework Directive (WFD) demands consideration of normative definitions for assessing ecological state of marine waters. For phytoplankton, ‘deviations from the ideal’ need to be considered for species composition and abundance, average biomass and the occurrence of blooms. A combination of phytoplankton metrics has been developed which, when considered in combination, should provide a confident assessment of the ecological state of each water body under assessment. The aim of this study was to evaluate phytoplankton community structure in different coastal and estuarine water bodies within England and Wales, and to contribute evidence towards the development of a community-based phytoplankton indicator. Influences of seasonality on the species assemblage were tested using a long-term data set available from a long-term monitoring site just offshore of Plymouth, UK. There is a substantive seasonal influence to the data, with a maximum of 10–14 common species (out of a potential 20) reoccurring within the same calendar month over a 10-year time span. Comparisons between reference and test water bodies give a range of common species of between 3 and 11 species within water type and season. A statistical and qualitative approach for comparing the most common species occurring between a reference and test site were tested for development of a WFD phytoplankton assessment tool. Overall, the results indicate that there are distinct phytoplankton assemblages over seasons which could form the basis of a community assessment metric. However, differences in boundary conditions are negligible between the different areas. There is evidence that community populations may be ubiquitous across marine water types in England and Wales, and development of generic seasonal lists across typologies could be appropriate in the further development of this tool.     

Alteration of the food web along the Antarctic Peninsula in response to a regional warming trend

In the nearshore coastal waters along the Antarctic Peninsula, a recurrent shift in phytoplankton community structure, from diatoms to cryptophytes, has been documented. The shift was observed in consecutive years (1991–1996) during the austral summer and was correlated in time and space with glacial melt‐water runoff and reduced surface water salinities. Elevated temperatures along the Peninsula will increase the extent of coastal melt‐water zones and the seasonal prevalence of cryptophytes. This is significant because a change from diatoms to cryptophytes represents a marked shift in the size distribution of the phytoplankton community, which will, in turn, impact the zooplankton assemblage. Cryptophytes, because of their small size, are not grazed efficiently by Antarctic krill, a keystone species in the food web. An increase in the abundance and relative proportion of cryptophytes in coastal waters along the Peninsula will likely cause a shift in the spatial distribution of krill and may allow also for the rapid asexual proliferation of carbon poor gelatinous zooplankton, salps in particular. This scenario may account for the reported increase in the frequency of occurrence and abundance of large swarms of salps within the region. Salps are not a preferred food source for organisms that occupy higher trophic levels in the food web, specifically penguins and seals, and thus negative feedbacks to the ecology of these consumers can be anticipated as a consequence of shifts in phytoplankton community composition.     

鄱阳湖不同水文期浮游生物群落结构特征和影响因素及水质评价

为阐明鄱阳湖不同水文期浮游生物群落结构特征及其影响因素,研究于2017年8月(丰水期)和12月(枯水期)在鄱阳湖湖区典型水域设置5个采样点进行浮游生物采样调查。研究期间共鉴定浮游植物8门75属186种,丰水期与枯水期均以硅藻门和绿藻门为主。共鉴定浮游动物4类76种,丰水期与枯水期均以原生动物和轮虫为主。方差分析显示:浮游植物密度与生物量在不同水文期之间的差异均为极显著(P<0.01),浮游动物丰水期密度高于枯水期,但无显著差异(P>0.05),浮游动物生物量(P<0.05)在不同水文期差异显著。冗余分析(RDA)显示:丰水期透明度和浮游生物呈显著负相关关系,电导率和浮游生物呈显著正相关。透明度、电导率与营养盐是影响丰水期浮游生物群落结构的主要环境因素,枯水期水温和溶解氧是驱动鄱阳湖浮游生物群落生态分布的主要环境因素。基于Shannon-Wiener(H′)、Margalef(d)和Pielou(J)等生物多样性指数的水质评价结果表明:鄱阳湖研究区域水质状态处于寡污-中污之间。研究揭示了2个水文期对通江湖泊浮游生物的影响:季节变化不改变湖泊浮游生物的物种组成及优势种,但...     

Dinoflagellates and ciliates at Helgoland Roads, North Sea

A monitoring programme for microzooplankton was started at the long-term sampling station “Kabeltonne” at Helgoland Roads (54°11.3′N; 7°54.0′E) in January 2007 in order to provide more detailed knowledge on microzooplankton occurrence, composition and seasonality patterns at this site and to complement the existing plankton data series. Ciliate and dinoflagellate cell concentration and carbon biomass were recorded on a weekly basis. Heterotrophic dinoflagellates were considerably more important in terms of biomass than ciliates, especially during the summer months. However, in early spring, ciliates were the major group of microzooplankton grazers as they responded more quickly to phytoplankton food availability. Mixotrophic dinoflagellates played a secondary role in terms of biomass when compared to heterotrophic species; nevertheless, they made up an intense late summer bloom in 2007. The photosynthetic ciliate Myrionecta rubra bloomed at the end of the sampling period. Due to its high biomass when compared to crustacean plankton especially during the spring bloom, microzooplankton should be regarded as the more important phytoplankton grazer group at Helgoland Roads. Based on these results, analyses of biotic and abiotic factors driving microzooplankton composition and abundance are necessary for a full understanding of this important component of the plankton.     

Interaction among Non-toxic Phytoplankton,Toxic Phytoplankton and Zooplankton: Inferences from Field Observations

We explore the mutual dependencies and interactions among different groups of species of the plankton population, based on an analysis of the long-term field observations carried out by our group in the North–West coast of the Bay of Bengal. The plankton community is structured into three groups of species, namely, non-toxic phytoplankton (NTP), toxic phytoplankton (TPP) and zooplankton. To find the pair-wise dependencies among the three groups of plankton, Pearson and partial correlation coefficients are calculated. To explore the simultaneous interaction among all the three groups, a time series analysis is performed. Following an Expectation Maximization (E-M) algorithm, those data points which are missing due to irregularities in sampling are estimated, and with the completed data set a Vector Auto-Regressive (VAR) model is analyzed. The overall analysis demonstrates that toxin-producing phytoplankton play two distinct roles: the inhibition on consumption of toxic substances reduces the abundance of zooplankton, and the toxic materials released by TPP significantly compensate for the competitive disadvantages among phytoplankton species. Our study suggests that the presence of TPP might be a possible cause for the generation of a complex interaction among the large number of phytoplankton and zooplankton species that might be responsible for the prolonged coexistence of the plankton species in a fluctuating biomass.     

some aspects of the biochemical and mineral composition of marine plankton

A natural population of phytoplankton and two species of zooplankton, Calanus finmarchicus (Gunnerus) (stage V) and Sagitta elegans (Verrill) (mature), were analysed for their biochemical and mineral composition. Comparison with published data for the same categories of plankton shows that the distribution of both organic and mineral fractions is highly variable, the causes of which are not equally understood. The composition of the organic fraction is affected by the duality of function of the biochemical constituents and by the large number of ecological factors which influence their concentration. Whether this applies to the mineral fraction remains uncertain; nevertheless it appears that plankton concentrate trace metals, that phytoplankton has a greater ability to concentrate them than zooplankton, and that the ability of zooplankton to concentrate various metals varies with the species.     

鄱阳湖国家级自然保护区浮游生物群落结构及空间分布

为评价春季大旱后鄱阳湖国家级自然保护区浮游生物现状,对保护区所辖 8 个子湖及赣江和修河部分河段的浮游生物进行调查和分析。调查共发现浮游植物 53 属 97 种、浮游动物 23 属 42 种（包括原生动物 13 种、轮虫 23 种、枝角类 3 种和桡足类 3 种）,其中大湖池和朱市湖是浮游生物种类数最多的 2 个子湖。各子湖及赣江和修河间浮游生物现存量差异较大,其变化范围分别为260（8.18106）cells/L（浮游植物）、363073173 ind./L（浮游动物）,赣江以西区域的子湖和修河的浮游生物现存量显著高于赣江及其以东区域的子湖。调查水域优势度值（Y）大于 0.02 的浮游生物包括蓝藻 1 种、绿藻 2 种、硅藻 5 种、原生动物 4 种及轮虫 5 种。浮游生物 Shannon-Wiener 多样性指数（H'）和均匀度指数（J）的最大值均分别为 2.41 和 0.96,而其丰富度指数（Dm）值均小于 3。3 种多样性指数综合评价表明,保护区各子湖与修河和赣江水体受污染程度较轻,除蚌湖和梅西湖外,均处于中污状态。       

青岛棘洪滩水库浮游藻类状况及水质评价

2003年5月至2004年5月对棘洪滩水库藻类的群落结构进行了研究。共发现藻类49属63种。水库进水口、水库中心、出水口藻类的种类组成没有明显差异,群落季节变化明显,冬春季以硅藻、隐藻为主,其优势种分别为小环藻和尖尾蓝隐藻。金藻有短时大规模出现,主要是分歧锥囊藻。夏秋季以蓝藻、绿藻为主。藻类周年变动模式为单峰型,藻类细胞密度最低值出现在1月份出水口,为0.05×106ind./L,主要是硅藻类的小环藻和隐藻,占总数的92.8%;最高值出现在10月份进水口,为196.7×106ind/L,主要是丝状蓝藻包括伪鱼腥藻、颤藻等占总数的81.2%。藻类生物量在0.34-7.77mg/L内变动,最低值出现在1月份出水口,此时硅藻门的小环藻占69.6%;最高值出现在8月份进水口,其中丝状蓝藻占71.44%;年均值进水口为1.82mg/L,出水口为1.09mg/L。Shannon-Weaver多样性指数变化范围为0.93-3.30,最低值和最高值分别出现在2004年1月进水口和2003年11月水库中心。年均值进水口为1.88,出水口为2.15。水质总体状况较好,处于中营养,但有向富营养转变的趋势,应注意加强对水源及水库的管理和保护。       

Distribution and development of under-ice phytoplankton in 90-m deep water column of Lake Päijänne (Finland) during spring convection

Distribution and development of phytoplankton were studied in the deep and large Lake Päijänne from mid-winter until the disappearance of ice. Diatoms were an important part of the phytoplankton assemblage and, with cryptophytes and chrysophytes, made up 50–80% of the phytoplankton biomass. In mid-winter, chlorophyll a and phytoplankton biomass were uniformly distributed over the whole water column down to a depth of 90 m. Thus, most of the phytoplankton was in virtual darkness and there was negligible growth. Only motile cryptophytes were concentrated in the layers below the ice and were rare in deep water. After the disappearance of snow, convection developed, but at first cryptophytes were able to resist mixing. When convection turned from penetrative to predominantly horizontal, all phytoplankton were generally uniformly distributed in the water column. In spite of the full under-ice overturn with low average availability of light, the phytoplankton biomass doubled in April. The growth of cryptophytes was higher than that of diatoms, suggesting that motile species gained an advantage by being able to maintain themselves in the upper, illuminated layers. The results show that knowledge of the basic physical framework is essential for interpretation of under-ice phytoplankton results.     

Monitoring phytoplankton, bacterioplankton, and virioplankton in a coastal inlet (Bedford Basin) by flow cytometry.

BACKGROUND: To establish the prevailing state of the ecosystem for the assessment of long-term change, the abundance of microbial plankton in Bedford Basin (Nova Scotia, Canada) is monitored weekly by flow cytometry. METHODS: Phytoplankton are detected by their chlorophyll autofluorescence. Those that contain phycoerythrin are designated as Synechococcus cyanobacteria or cryptophyte algae according to the intensity of light scatter. Bacteria and viruses are stained with DNA-binding fluorochromes and detected by green fluorescence. Distinction is made between bacterial and viral subpopulations exhibiting high and low fluorescence. RESULTS: Time series data are presented for weekly observations from 1991 to 2000. Weekly averages are computed for the complete annual cycle of temperature, salinity, river discharge, nitrate, phosphate, silicate, chlorophyll, total phytoplankton including Synechococcus and cryptophytes, total bacteria including high and low-fluorescence subpopulations, and total viruses including high and low-fluorescence subpopulations. CONCLUSIONS: The microbial biomass in the surface water of Bedford Basin is dominated by phytoplankton. The spring bloom of phytoplankton represents a maximum in algal biovolume, but not in cell number. Phytoplankton, bacteria, and viruses all attain their annual numerical maxima between the summer solstice and the autumn equinox. A vigorous microbial loop and viral shunt is envisioned to occur in the summer.     

Assessment of the ecological status of regulated lakes: stressor-specific metrics from littoral fish assemblages

Although in situ sediment capping is frequently used to reduce internal loading of contaminants and nutrients, post-application assessment rarely includes the potential undesirable short-term effects on plankton species composition. We hypothesised that a modified zeolite (Z2G1) application as a sediment capping agent in Lake Okaro, New Zealand, could cause significant undesirable shifts in species composition of both zooplankton and phytoplankton due to burial of resting stages or interference with feeding for the zooplankton. Alternatively, we predicted that the capping agent might have no effect due to, for example, the coarse grain size of the material (1–3 mm). We used multidimensional scaling (MDS) and analysis of similarity (ANOSIM) to identify any adverse effects of Z2G1 on zooplankton and phytoplankton species composition (i.e. shifts in community structure, including species loss) by comparing the community structure before and after the Z2G1 application. We found no significant differences in species composition before and after the Z2G1 application at the depths investigated (surface and 9 m). However, all of the analyses showed statistically significant differences among seasons, indicating seasonal variations in plankton composition far outweigh those that may have resulted from the Z2G1 application. Coarse particle size, low dose rate and a restricted area where the sediment capping agent was applied were considered to be the factors limiting potential adverse effects on plankton species. Considerations of finer-grained material to increase coverage and efficacy of phosphorus adsorption require assessment for their effects on zooplankton, however, and a direct mode of application into the hypolimnion is recommended to minimise effects on zooplankton and phytoplankton communities.     

On the occurrence of Diogenes pugilator in the German Bight (Crustacea: Decapoda Diogenidae)

The occurrence of Diogenes pugilator in the German Bight has been examined since 2005. The steady onshore and offshore presence confirms that this southern species has established sustaining populations. The morphometric features are comparable to that of other populations in the adjacent Atlantic Ocean.     

Diurnal fluctuations within a littoral plankton community in oligotrophic Lake Pääjärvi, southern Finland

SUMMARY. The plankton community within an Equisetum fluviatile stand in oligotrophic Lake Pääjärvi had distinct diurnal fluctuations in the total cell volume and species composition of algae and in the abundance of microcrustaceans ( Bosmina coregoni ). Diurnal fluctuations in pH, oxygen saturation and temperature of the water were also recorded. Within the littoral region, daytime pH values > 9 were recorded, whereas in the pelagial region of the lake, values remained near pH 7. Diatoms and green algae dominated the littoral phytoplankton especially in the innermost parts of the macrophyte stand, with cryptophytes (dominant in the pelagial area) occurring only in small numbers. At the outer parts of the macrophyte stand, water movements between the pelagial and littoral areas might rapidly increase the contribution of cryptophytes in the phytoplankton. The fall in algal cell volume during the night may have resulted from settling out of cells in the absence of wind-induced water movements, perhaps together with increased grazing pressure from dense swarms of Bosmina (up to 3000 individuals per litre) which appeared during the night.     

Midsummer zooplankton assemblages in four types of wetlands in the Upper Midwest,USA

The objective of this study was to characterize the zooplankton and phytoplankton assemblages of four different types of wetlands and to evaluate their use as environmental indicators. Total abundances, community composition, and species diversity were evaluated for zooplankton and phytoplankton assemblages from 24 wetlands and related to water quality variables. During August 1995, six representative sites were sampled from four types of wetlands designated as constructed, impacted, non-impacted, or temporary. The plankton assemblages of all wetlands were dominated by cosmopolitan crustacean, rotifer, and phytoplankton taxa typical of lake plankton communities. Species diversity, richness, and evenness of zooplankton and phytoplankton assemblages did not differ significantly among the wetland types. Total zooplankton abundance was significantly (p < 0.01) related to chlorophyll a and total phosphorus concentrations over the range of trophic conditions. Mean zooplankton densities and phytoplankton biovolumes were similar among the wetlands, however, the relative abundances of major zooplankton groups differed among the wetland types. Cyanophytes, primarily Oscillatoria spp., were a major component of the phytoplankton across all four wetland types, and were significantly more abundant within the constructed and temporary sites. On average, rotifers accounted for 79% of total zooplankton abundance within the constructed wetlands and were much less dominant in the non-impacted and temporary wetlands. Cladoceran, copepodite, and adult copepod concentrations were low in the constructed and impacted wetlands and increased in the non-impacted and temporary wetlands in conjunction with increased chlorophytes and cryptophytes. Our preliminary survey suggests that abiotic factors which are known to directly affect phytoplankton may indirectly affect zooplankton composition in such a way as to use zooplankton assemblages as indicators of water quality. However, further study incorporating seasonal dynamics and the influence of predators on zooplankton assemblages is needed to fully assess the use of zooplankton community composition as an environmental indicator for wetland systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

鲢放养和施肥对盐碱池塘围隔生态系统浮游生物群落的影响

报道了单养链（Hypophthalmichthys molitrix)和施肥对盐碱池塘围隔生态系统浮游生物群落的影响,链的放养使浮游植物丰度,叶绿素a 含量和和初组生产力增大,浮游植物小型化,生物量以小型硅藻和绿藻占优势,裸藻和金藻占有相当比重;浮游动物生物量减少,特别是枝角类的生物量无鱼围隔大于有鱼围隔,且多是较大型的种类,施肥特别是施无机肥能显著地提高浮游植物丰度和初级生产力,浮游动物生物量也增大,施有机肥围隔浮游植物和浮游动物生物量虽高于有鱼对照围隔,但其浮游植物初级生产力,叶绿素a含量,浮游生物多样性指数,P／R系数均较低,链鱼的生长最差,文中讨论了滤食性鱼类和施肥对浮游生物的影响。     

Plankton abundance in relation to physicochemical factors in the Bui reservoir of Ghana's Black Volta River

The relationship between physicochemical factors and plankton abundance in the newly created Bui reservoir was studied during 2011 and 2012. The objective was to assess the influence of physicochemical factors on plankton abundance and provide data for monitoring the hydrobiology of the newly created Bui reservoir. Two sampling stations were selected on the Black Volta upstream (Bui) and downstream (Bamboi) of the dam, with samples taken pre‐ and postimpoundment during the study period. Canonical Correspondence Analysis (CCA) was used to trace temporal plankton community changes and to examine the relationships between species composition and physicochemical variables. The relative abundance of some phytoplankton species such as Anabaena sp., Planktothrix sp. and Scenedesmus sp. was directly correlated to nitrates. CCA indicated that physicochemical variables explained 41–64% of zooplankton and 8–12% of phytoplankton variation. Hence, there were correlations between environmental variables and the structure of plankton assemblages. This feature should therefore be used for bio‐monitoring of environmental variables of the river by the Bui Power Authority to ensure protection of the aquatic biota downstream of the Bui dam.