沿岸海域富营养化与赤潮发生的关系

综述了赤潮的发生与沿岸海域富营养化的关系。近几十年来,人类活动使得天然水体的富营养化进程大大加速。营养负荷的增加与高生物量水华的增多相联系。控制营养输入后,浮游植物生物量或有害藻类水华事件也相应减少。营养的组成与浮游植物的种类组成及水华的形成有密切联系。有机营养对有害藻类水华的促进作用受到关注。营养输入时机影响浮游植物种间竞争的结果,因而对浮游植物的群落演替具有深远影响。由于浮游植物存在生理差异,因而对营养加富的反应因种而异。营养在调控某些有毒藻类的毒素产量方面也发挥着重要作用。此外,营养输入与藻类水华之间存在复杂的间接联系。当然,营养状况并非浮游植物群落演替的唯一决定因素。研究结果提示,控制营养输入、减缓水域富营养化是减少有害藻类水华发生的有效途径,而深入研究典型有害藻类的营养生理对策则为防治并最终消除有害藻类水华提供了理论基础。     

Cyanobacterial dominance in lakes

Cyanobacterial dominance in lakes has received much attention in the past because of frequent bloom formation in lakes of higher trophic levels. In this paper, underlying mechanisms of cyanobacterial dominance are analyzed and discussed using both original and literature data from various shallow mixed and deep stratifying lakes from temperate and (sub)tropical regions. Examples include all four ecotypes of cyanobacteria sensu Mur et al. (1993), because their behavior in the water column is entirely different. Colony forming species (Microcystis) are exemplified from the large shallow Tai Hu, China. Data from a shallow urban lake, Alte Donau in Austria are used to characterize well mixed species (Cylindrospermopsis), while stratifying species (Planktothrix) are analyzed from the deep alpine lake Mondsee. Nitrogen fixing species (Aphanizomenon) are typified from a shallow river-run lake in Germany. Factors causing the dominance of one or the other group are often difficult to reveal because several interacting factors are usually involved which are not necessarily the same in different environments. Strategies for restoration, therefore, depend on both the cyanobacterial species involved and the specific causing situation. Some uncertainty about the success of correctives, however, will remain due to the stochastic nature of the events and pathways leading to cyanobacterial blooms. Truly integrated research programs are required to generate predictive models capable of quantifying key variables at appropriate spatial and temporal scales.     

Causes,historical development,effects and future challenges of a common environmental problem: eutrophication

The impact of the presence of us humans as well as our activities to nature has led to over-exploitation of natural resources and to dramatic changes in land-use including the use of artificial fertilizers contributes to the deterioration of the natural environment. The population density, industrial processes and the use of fertilizers are the main causes for the eutrophication of river systems, estuaries and seas. There are several ways to determine the actual nutrient levels back to the 1950s, back to 1900 or even back to 1800. Available data indicate that the natural background concentrations of nutrients (pristine conditions or the period prior to the widespread use of artificial fertilizers and detergents) were dramatically lower than today. Available time series on chemical and biological data collected from different parts of the world show the (sometimes tremendous) increase in nutrient levels and the related productivity. The same time series, however, also show the decreases in values when measures were taken to reduce the nutrient emissions. Investigations of different systems all over the world show that nearly every system responses differently to eutrophication. Especially physical boundary conditions play an important role in the manifestation of the ultimate effect of local eutrophication. Apart from the physical boundary conditions also the transformation and retention of nutrients in estuarine and coastal systems contribute to system specific responses. Depending on all these different conditions, site specific responses with even site specific problems may occur. The challenge of this millennium is to really reach a balance between nature and mankind including its population size. A beneficial step in this discussion is assessing criteria to reduce eutrophication back to a level acceptable to both humans and nature.     

Feeding and control of blue-green algal blooms by tilapia (Oreochromis Niloticus)

Outbreak of blue-green algal blooms, with associated unsightly scum and unpleasant odor, occurs frequently in eutrophic lakes. We conducted feeding experiments to study ingestion and digestion of Microcystis aeruginosa by tilapia (Oreochromis niloticus) under laboratory conditions and field testing to reduce Microcystis blooms by stocking tilapia in Lake Yuehu and other eutrophic waters in Ningbo, China between 2000 and 2003. Our results show that tilapia was capable of ingesting and digesting a large quantity of Microcystis. Digestion efficiency ranged from 58.6 to 78.1% at water temperature of 25 °C. Ingestion rate increased with increasing fish weight and water temperature. Intensive blooms occurred in Lake Yuehu in both 1999 and 2000. The lake was stocked with silver carp (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis) and a freshwater mussel (Hyriopsis cumingii) at a total biomass of 9.8 g m⁻³ in early 2001, and tilapia at 3–5 g m⁻³ in April of 2002. From June to October, average phytoplankton density decreased from 897.6×10⁶ cells l⁻¹ in 2000 to 291.7×10⁶ cells l⁻¹ in 2001 and 183.0×10⁶ cells l⁻¹ in 2002. Compared to 2000, the annual average phytoplankton biomass in 2001 and 2002 decreased by 48.6% and 63.8%, respectively. The blue-green algal biomass which made up 70% of the total phytoplankton biomass in 2000 was reduced to 22.1% in 2001 and 11.2% in 2002. Meanwhile, Secchi depth increased from 20–50 cm to 55–137 cm during the same time period. Similar results were observed in some other eutrophic waters. For example, algal bloom disappeared about 20 days after tilapia fingerlings were stocked (8–15 g m⁻³) to a pond in Zhenhai Park. Chlorophyll a concentration and phytoplankton production declined dramatically whereas water transparency increased substantially. However, the impacts of tilapia on nitrogen and phosphorus dynamics in natural lakes need further investigation. Our studies revealed that stocking tilapia is an effective way to control algal blooms in eutrophic waters, especially in lakes where nutrient loading cannot be reduced sufficiently, and where grazing by zooplankton cannot control phytoplankton production effectively.     

洋河水库富营养化发展趋势及其关键影响因素

洋河水库作为秦皇岛和北戴河暑期办公的重要水源地,近年来富营养化逐年加重,水质恶化.通过收集历史资料和现场连续监测,综合分析了洋河水库富营养化发展趋势及其关键影响因素,结果表明1990-2011年期间,总氮、总磷常年超过国际公认的发生富营养化的浓度水平,每年8月是水华集中暴发期.以8月为例,自1990年以来,水体总氮、总磷和叶绿素a浓度逐年上升,透明度则呈明显下降趋势,富营养化状态从1990年的中营养状态变成2011年的超富营养状态.对2011年5-10月监测数据进行相关关系分析发现水温、透明度、溶解氧、pH值、总磷、正磷酸盐、高锰酸盐指数和总有机碳都与叶绿素a浓度明显相关,其中透明度、溶解氧、pH值是水华暴发的结果而非原因,表明透明度、溶解氧和pH值是水华暴发影响水质的主要表现因素;既然洋河水库地处北温带,四季分明,冬季存在2-3个月的冰封期,因此水温是水库水华暴发的驱动因子之一.2011年7月中旬至8月底洋河水库暴发了全库水域的蓝藻水华,优势种为铜绿微囊藻(Microystis aeruginosa)和鱼害微囊藻(M.ichthyoblabe),密度分别达到3.5×106和1.4×106个/mL.     

气候变化与人类活动双重驱动的冷水湖泊富营养化

富营养化对水生生态系统造成的负面影响已在世界范围内广泛发生,尤其对淡水水源地湖泊的水环境质量影响深远,进而引起当地居民的饮用水安全与健康隐患。在人类活动和气候变化的双重驱动下,富营养化辐射的范围不断扩大,从过去主要集中于温带大型浅水湖泊已经扩展到寒冷地区的冷水湖泊。分析了近年来世界范围内高寒地区冷水湖泊富营养化的趋势特征与研究进展,探讨了气候变化、人类干扰(农业活动、畜牧业生产、管理措施不当等)在不同地区冷水湖泊富营养化进程中的作用。在未来的研究中,应进一步加强对冷水湖泊富营养化机制的探讨,并对已有富营养化症状的湖泊进行生态修复,以确保冷水湖泊生态系统健康并改善饮用水源地的环境质量。     

Non-climatic thermal adaptation: implications for species' responses to climate warming

There is considerable interest in understanding how ectothermic animals may physiologically and behaviourally buffer the effects of climate warming. Much less consideration is being given to how organisms might adapt to non-climatic heat sources in ways that could confound predictions for responses of species and communities to climate warming. Although adaptation to non-climatic heat sources (solar and geothermal) seems likely in some marine species, climate warming predictions for marine ectotherms are largely based on adaptation to climatically relevant heat sources (air or surface sea water temperature). Here, we show that non-climatic solar heating underlies thermal resistance adaptation in a rocky–eulittoral-fringe snail. Comparisons of the maximum temperatures of the air, the snail''s body and the rock substratum with solar irradiance and physiological performance show that the highest body temperature is primarily controlled by solar heating and re-radiation, and that the snail''s upper lethal temperature exceeds the highest climatically relevant regional air temperature by approximately 22°C. Non-climatic thermal adaptation probably features widely among marine and terrestrial ectotherms and because it could enable species to tolerate climatic rises in air temperature, it deserves more consideration in general and for inclusion into climate warming models.     

1996年德国石荷西部沿岸水域浮游植物种群变动及其整齐圆筛藻赤潮

1996年早春至初夏,德国石荷州西海岸水域尤其是在易白河河附近海区发生了数次赤潮事件,河口区的高叶绿素浓度总是与低盐、高营养盐浓度的分布区吻合。从早春3月至5月底,发生了持续时间很长的大规模赤潮事件,其引发赤潮原因种为整齐圆筛藻,6月份对浮游植物生物量的贡献主要来自几种硅藻如微小细柱藻、聚生角毛藻、远洋角毛灌以及属于鞭毛藻类的棕囊藻群体,7月中旬,自养的纤毛虫类Myrionecta rubra (Mesodinium rubrum）达到数量高峰。从7月下旬至8月中旬,以梭形角藻、叉状角藻占优势的甲藻类几科贡献了全部的浮游植物生物量,8月中旬至9月上旬为甲藻和硅藻等类别的混合期,9月中旬以后,硅藻重新占据浮激植物 数量的绝对优势,主要优势种为浮动弯角藻、复瓦根管藻等,该海域浮游植物种群的演替反映了温带海域的特征。在早期发生的大规模赤潮期间,整齐圆筛藻的细胞密度达到2180cells dm^-3,与之相对应的生物量为758.1μg C dm^-3,占浮游植物生物量的94.2%,整齐圆筛藻的爆发性增殖所产生的大量油膜覆盖了黑尔果兰岛和东Frisian群岛周围的海域,这一现象有史以来第一次被卫星所观测到。     

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.     

Dilution bioassays: Their application to assessments of nutrient limitation in

Hypereutrophic waters, which are characterized by nutrient inputs exceeding phytoplankton nutrient requirements, are often sites of chronic nuisance algal blooms and associated water quality deterioration problems. In order to restore such systems to acceptable water quality standards, identification of growth-limiting nutrients is of central importance. Conventional nutrient addition bioassay techniques are often ineffective in identifying potentially limiting nutrients, due to persistent nutrient excesses in hypereutrophic systems. Accordingly, we have developed a nutrient dilution bioassay, in which stepwise dilutions of phytoplankton nutrients (nitrogen, phosphorus, iron, trace metals) with a nutrient-free major ion solution are capable of; 1) identifying those nutrients potentially most limiting, and 2) establishing magnitudes of respective nutrient input cutbacks required to bring about nutrient-limited control of phytoplankton growth. In situ deployment of dilution bioassays should help establish criteria governing minimal nutrient inputs required to arrest undesirable impacts of hypereutrophy. We have evaluated the field applicability of dilution bioassays, during a 2 year trial in the periodically hypereutrophic Neuse River, North Carolina.     

Influence of simulated climate change and eutrophication on three‐spined stickleback populations: a large scale mesocosm experiment

1. Shallow lakes and their ectothermic inhabitants are particularly vulnerable to the effects of climatic warming. These impacts are likely to depend on nutrient loading, especially if the combination of warming and eutrophication leads to severe hypoxia. 2. To investigate effects of realistic warming and nutrient loading on a fish species with high tolerance of warming and hypoxia, we observed population changes and timing of reproduction of three‐spined sticklebacks in 24 outdoor shallow freshwater ecosystems with combinations of temperature (ambient and ambient +4 °C) and three nutrient treatments over 16 months. 3. Warming reduced stickleback population biomass by 60% (population size by 76%) and nutrient‐addition reduced biomass by about 80% (population size 95%). Nutrients and warming together resulted in extinction of the stickleback populations. These losses were mainly attributed to the increased likelihood of severe hypoxia in heated and nutrient‐addition mesocosms. 4. Warming of nutrient‐rich waters can thus have dire consequences for freshwater ectotherm populations. The loss even of a hardy fish suggests a precarious future for many less tolerant species in such eutrophic systems under current climate change predictions.     

Factors influencing seaweed responses to eutrophication: some results from EU-project EUMAC

Seaweed responses to eutrophication and their role in coastal eutrophication processes were compared at 8 different sites along the European coasts from the Baltic to the Mediterranean as part of the EU-ENVIRONMENT Project Marine Eutrophication and benthic Macrophytes (EUMAC). Structural and functional changes of marine benthic vegetation typical of eutrophic waters, in particular mass development (blooms) of certain seaweeds, are not merely the result of increased nutrient loading, but must be attributed to complex interactions of primary and secondary effects during the eutrophication process. Due to species-specific physiological properties of the algae (nutrient kinetics, growth potential, light, temperature requirements), the combined effects of abiotic and biotic factors on juvenile or adult developmental stages control the development of algal blooms in different ways. In particular the role of light, temperature, water motion and oxygen depletion, as well as of grazers, on early and adult developmental stages of the algae are considered. The result are discussed in the context of coastal eutrophication control and management. This revised version was published online in June 2006 with corrections to the Cover Date.     

Climate change reduces reproductive success of an Arctic herbivore through trophic mismatch

In highly seasonal environments, offspring production by vertebrates is timed to coincide with the annual peak of resource availability. For herbivores, this resource peak is represented by the annual onset and progression of the plant growth season. As plant phenology advances in response to climatic warming, there is potential for development of a mismatch between the peak of resource demands by reproducing herbivores and the peak of resource availability. For migratory herbivores, such as caribou, development of a trophic mismatch is particularly likely because the timing of their seasonal migration to summer ranges, where calves are born, is cued by changes in day length, while onset of the plant-growing season on the same ranges is cued by local temperatures. Using data collected since 1993 on timing of calving by caribou and timing of plant growth in West Greenland, we document the consequences for reproductive success of a developing trophic mismatch between caribou and their forage plants. As mean spring temperatures at our study site have risen by more than 4 degrees C, caribou have not kept pace with advancement of the plant-growing season on their calving range. As a consequence, offspring mortality has risen and offspring production has dropped fourfold.     

Modelling adaptive management strategies for coping with the impacts of climate variability and change on riverine algal blooms

The impact of climate change on hydrology and water resources is one of the most critical issues facing the world in the next few decades. In particular, there is a need to quantify the risks associated with maintaining the security of resource quantity and quality, and to assess the effectiveness of potential management strategies. In this paper, we assess the impacts of climate variability and change on one aspect of river health. A simple model of Anabaena algal bloom occurrence at a weir pool in the lower Murrumbidgee River, Australia, has been coupled to a catchment model that is used to simulate streamflow, irrigation demand and diversions, dam water storage and releases, and decision-making by both irrigators and managers. Long-term climate data are obtained from a statistical downscaling algorithm, which, when applied to global climate model predictions can provide climate data suitable for driving the coupled model under a variety of climatic scenarios. The coupled model is then used to assess the impact of climate variability and projected climate change on the frequency, duration and magnitude of Anabaena blooms. The impact of two management strategies for bloom control are also assessed and it is shown that even a single, quite simple, resource-neutral, adaptive management strategy has the potential to substantially reduce the occurrence and impact of algal blooms and to more than compensate for the deleterious impacts of climate change. This result supports the notion that planning for the future can lead to positive outcomes in the present.     

Effects of global climate change on marine and estuarine fishes and fisheries

Global climate change is impacting and will continue to impact marine and estuarine fish and fisheries. Data trends show global climate change effects ranging from increased oxygen consumption rates in fishes, to changes in foraging and migrational patterns in polar seas, to fish community changes in bleached tropical coral reefs. Projections of future conditions portend further impacts on the distribution and abundance of fishes associated with relatively small temperature changes. Changing fish distributions and abundances will undoubtedly affect communities of humans who harvest these stocks. Coastal-based harvesters (subsistence, commercial, recreational) may be impacted (negatively or positively) by changes in fish stocks due to climate change. Furthermore, marine protected area boundaries, low-lying island countries dependent on coastal economies, and disease incidence (in aquatic organisms and humans) are also affected by a relatively small increase in temperature and sea level. Our interpretations of evidence include many uncertainties about the future of affected fish species and their harvesters. Therefore, there is a need to research the physiology and ecology of marine and estuarine fishes, particularly in the tropics where comparatively little research has been conducted. As a broader and deeper information base accumulates, researchers will be able to make more accurate predictions and forge relevant solutions.