The eutrophication of shallow coastal lakes in Southwest England — understanding and recommendations for restoration,based on palaeolimnology,historical records,and the modelling of changing phosphorus loads

Palaeolimnological studies of sediments from Slapton Ley and Loe Pool, two coastal freshwater lakes in Southwest England, show that in the period since 1945, they have been eutrophicated by nutrient inputs from intensification of agriculture, but also from sewage effluent. Two simple models have been used to identify the main sources of catchment outputs, and in the case of Slapton Ley, to evaluate historical changes in land use, and their likely effect on lake trophic status.Restoration strategies may also be evaluated using the same models. They suggest that in order to reduce loads on either lake to within OECD permissible limits, not only will all sewage inputs need to be prevented, and non-phosphate detergents used, but also losses from agricultural land must be reduced. This could take the form of the keeping of fewer cattle (the main source of organic nitrogen and phosphorus in both catchments), or the zoning of the respective catchments so that steep slopes close to riparian zones are not used, as at present, for the grazing of livestock.A better option, however, would appear to be the establishment along most of the rivers draining into these lakes, of buffer strips of woodland at least 15 m wide. According to the models, this measure, along with treatment or diversion of sewage effluent, would reduce phosphorus loads upon the lakes to within acceptable limits.     

Seasonality of Melosira-plankton of the great northern lakes

The paper discusses the seasonality of Melosira-plankton in Ladoga and Onega Lakes and its comparison with that in other large northern lakes. The periodicity of Melosira in dimictic temperate lakes is mainly connected with periods of turbulence of the lake water in spring and autumn. The role of Melosira in the primary productivity of great northern lakes is important both for the oligotrophic phase and in the case of eutrophication. In very advanced states of eutrophication the spring crop of Melosira-plankton may be the cause of oxygen depletion in the hypolimnion.     

Macro-zooplankter responses to simulated climate warming in experimental freshwater microcosms

1. We report data collected from 48 replicated microcosm communities created to mimic plant‐dominated shallow lake and pond environments. Over a 2‐year period, the microcosms were subjected to warming treatments (continuous 3 °C above ambient and 3 °C above ambient during summer only), a nutrient addition treatment and the presence or absence of fish. We tracked macro‐zooplankter dynamics, censusing cladoceran populations at the species level, copepods at the order level and ostracods as a class. 2. Responses to warming were subtle. Cladoceran diversity and overall abundance were not significantly affected by warming, although measures of community evenness increased. Warming effects on patterns of population trajectories tended to be strongly seasonal and most apparent during periods of pronounced increase. Populations of the prevalent cladocerans, Chydorus sphaericus and Simocephalus vetulus, displayed idiosyncratic patterns, with evidence in the case of S. vetulus for a negative relationship between warming and body‐size at maturity. Copepod populations were reduced in size by warming, but those of ostracods increased. 3. The effects of the nutrient addition and fish treatments were strong and consistent, interacting little with warming effects in statistical models. Zooplankter abundance tended to be the highest in the fish‐free microcosms receiving additional nutrient inputs and lowest when fish were present and no nutrients were added. Both treatments reduced cladoceran diversity and community evenness. 4. We suggest that warming, independently, is unlikely to supplant the effects of changing nutrient loading and fish predation as the major driver of zooplankter dynamics in shallow lakes and ponds. Moreover, in the situations where warming was of significant influence in our experiment, the distinction between summer‐only warming and year‐around warming was blurred. This suggests that warming effects were most pervasive during the summer, at the upper end of the temperature spectrum.     

Aggregating land use quantity and intensity to link water quality in upper catchment of Miyun Reservoir

Eutrophication resulting from nutrient enrichment decreases water quality and harms ecosystem structure and function, and its degree is significantly affected by land use in the catchment. Quantifying the relationship between eutrophication and land use can help effectively manage land use to improve water quality. Previous studies principally utilized land use quantity as an indicator to link water quality parameters, but these studies lacked insight into the impact of land use intensity. Taking the upper catchment of Miyun Reservoir as a case study, we developed a method of aggregating land use quantity and intensity to build a new land use indicator and tested its explanatory power on water quality. Six nutrient concentrations from 52 sub-watersheds covering the whole catchment were used to characterize the spatial distribution of eutrophication. Based on spatial techniques, empirical conversion coefficients, remote sensing data, and socio-economic statistical data, land use intensity was measured and mapped visually. The new land use indicator was calculated and linked to nutrient concentrations by Pearson correlation coefficients. Results demonstrated that our new indicator incorporating intensity information can quantify the different nutrient-exporting abilities of different land use areas. Compared to traditional indicators that only incorporate land use quantity, most Pearson correlation coefficients between the new indicator and water nutrient concentrations increased. This new information enhanced the explanatory power of land use on water nutrient concentrations, and so will be able to help us understand the impact of land use on water quality and guide decision making for better land use management.     

Loosdrecht Lakes,origin, eutrophication,restoration and research programme

The Loosdrecht Lakes area is briefly described, light has been shed on its morphology, history, the process of eutrophication with its concomitant phenomena, as well as the planned restoration and research programme.     

Eutrophication as an impact category

State of the art and research needs for the impact category eutrophication are discussed. Eutrophication is a difficult impact category because it includes emissions to both air and water — both subject to different environmental mechanisms — as well as impacts occurring in different types of terrestrial and aquatic ecosystems. The possible fate processes are complex and include transportation between different ecosystems. In some recent approaches, transportation modelling of air emissions has been included. However, in general, the used characterisation methods do not integrate fate modelling, which is a limitation. The definition of the impact indicator needs further research, too. The inclusion of other nutrients than those typically considered should also be investigated.     

Interaction of hydrological systems and eutrophication of the Loosdrecht Lakes

The history of eutrophication of the Loosdrecht Lakes system and the differences in trophic state of the compartments of this system are described from a hydrological point of view. Groundwater movement was found to be of paramount importance. This groundwater transport induced a horizontal surface water transport with concomitant biomass from Loosdrecht Lakes to Lake Breukeleveen, which explains partly the more eutrophic situation in the latter lake. The article summarizes several internal WOL-reports (ENGELEN and KAL, 1985; HETTLING, 1985a, b; KUHNEL, 1985; TEUNISSEN, 1985).     

Effects of global change on key processes of primary production in marine ecosystems

工业革命以来, 不断加剧的人类活动所引起的大气CO₂浓度增加、温度上升等全球变化问题, 正使得海洋生态系统面临着前所未有的压力。该文通过文献计量的方法分析了国内外的研究现状, 简要地回顾了全球变化对海洋生态系统影响研究的发展简史, 并聚焦海洋暖化、海洋酸化和富营养化与缺氧这三个核心研究方向, 重点阐述了它们对海洋生态系统初级生产的关键过程的影响, 总结了已取得的重要进展以及存在的主要问题, 最后提出前沿展望。     

Structural and functional measures of leaf-associated invertebrates and fungi as predictors of stream eutrophication

Eutrophication is a major threat to freshwater ecosystems worldwide that affects aquatic biota and compromises ecosystem functioning. In this study, we assessed the potential use of leaf decomposition and associated decomposer communities to predict stream eutrophication. Because leaf quality is expected to affect leaf decomposition, we used five leaf species, differing in their initial nitrogen concentration. Leaves of alder, chestnut, plane, oak and eucalyptus were placed in coarse-mesh bags and immersed in six streams along an eutrophication gradient to assess leaf decomposition and the structure of associated decomposer communities. A hump-shaped relationship was established between leaf decomposition and the eutrophication gradient for all leaf species, except for eucalyptus. Invertebrate biomass and density as well as fungal biomass and sporulation were lowest at the extremes of the gradient. Leaf-associated invertebrate and fungal assemblages were mainly structured by stream eutrophication. The percentage of shredders on leaves decreased, whereas the percentage of oligochaeta increased along the eutrophication gradient. The Iberian Biological Monitoring Working Party Index (IBMWP) applied to benthic invertebrates increased from oligotrophic to moderately eutrophic streams and then dropped sharply at highly and hypertrophic streams. Overall, leaf decomposition was a valuable tool to assess changes in stream water quality, and it allowed the discrimination of sites classified by the IBMWP within class I and class IV. Moreover, decomposition of most leaf species responded in a similar way to eutrophication when decomposition was normalized by the quality of leaves.