ECOSYSTEM MANAGEMENT AND THE CONSERVATION OF AQUATIC BIODWERSITY AND ECOLOGICAL INTEGRITY1

ABSTRACT: Ecologically effective ecosystem management will require the development of a robust logic, rationale, and framework for addressing the inherent limitations of scientific understanding. It must incorporate a strategy for avoiding irreversible or large-scale environmental mistakes that arise from social and political forces that tend to promote fragmented, uncritical, short-sighted, inflexible, and overly optimistic assessments of resource status, management capabilities, and the consequences of decisions and policies. Aquatic resources are vulnerable to the effects of human activities catchment-wide, and many of the landscape changes humans routinely induce cause irreversible damage (e.g., some species introductions, extinctions of ecotypes and species) or give rise to cumulative, long-term, large-scale biological and cultural consequences (e.g., accelerated erosion and sedimentation, deforestation, toxic contamination of sediments). In aquatic ecosystems, biotic impoverishment and environmental disruption caused by past management and natural events profoundly constrain the ability of future management to maintain biodiversity and restore historical ecosystem functions and values. To provide for rational, adaptive progress in ecosystem management and to reduce the risk of irreversible and unanticipated consequences, managers and scientists must identify catchments and aquatic networks where ecological integrity has been least damaged by prior management, and jointly develop means to ensure their protection as reservoirs of natural biodiversity, keystones for regional restoration, management models, monitoring benchmarks, and resources for ecological research.     

PHOSPHORUS ASSIMILATION IN A STREAM SYSTEM OF THE LAKE OKEECHOBEE BASIN1

ABSTRACT: The ability to predict how streams and wetlands retain phosphorus (P) is critical to the management of watersheds that contribute nutrients to adjacent aquatic systems such as lakes. Field and laboratory experiments were conducted to determine the P assimilatory capacity of a stream (Otter Creek) in the Taylor Creek/Nubbin Slough Basin located north of Lake Okeechobee, Florida. Dominant soils in this basin are sandy Spodosols; landuse is primarily dairy farms and beef cattle pastures. Estimates of P assimilation show that sediments assimilate approximately 5 percent of the P load. Phosphorus assimilation rates in the stream were estimated using first-order relationships based on the total P concentration of the water column as a function of distance from the primary source. This method assumes minimal lateral inputs. Stream lengths required for one turnover in P assimilation were estimated to be in the range of 3–16 km. Laboratory studies using intact sediment cores indicated a P assimilation rate of 0.025 m day^?1, and equilibrium P concentration of 0.16 ± 0.03 mg L^?1 in the water column. Dissolved P concentration gradients in the sediments showed upward flux of P at water column P concentration of <0.16 mg L^?1. Approximately 56–77 percent of the P assimilated in the above-ground vegetation during active growth was released or translocated within six months of senesence, suggesting short-term storage in above-ground vegetation. Bottom sediments and recalcitrant detrital plant tissue provide for long-term P assimilation in the creek. Although stream sediments have the potential to adsorb P, high flow rate and low contact period between water and sediment limits this process.     

The Sensitivity and Adaptation of Ecosystems to the Disturbances: A Case Study in Northeastern Estonia

The study focused on the problem of the response and adaptation of an ecosystem to natural fire in case of greenhouse warming. The palaeoecological approach was used and reconstructions were made for timeca 6000 years ago, when the human impact in the studied area was absent or very weak and the summer temperatures were about 2.4 degrees higher than at the present time. The palaeoreconstructions were compliled using the charcoal, pollen and diatoms data from the sediments of a northeast Estonian lake. The results show that forest fires influenced the biota of the lake mainly through evapotranspiration and the accompanying erosional changes. The impacts of the fire directly to the lake ecosystem were short-term and the primary diatom association was restored after 10–15 years. The pollen influx was influenced by the fires mainly through the changes in the openness of the landscape and the composition of the pollen spectra was restored over a period of 50–60 years. The data demonstrate the high ability of the studied ecosystem to adapt to the impact of natural fires in the climatic environment comparable with that predicted for the future.     

水环境两相分层流数值模拟

以研究水环境两相分层流精细预报模型为目标,广泛地涉及了两相湍流精细模拟的理论和方法。用Eulerian坐标系中多流体模型统一描述两相各自的运动,并分别对两相本分的湍流输运观作以及地相间互作规律进计模拟,建立了水环境两相分层流的双流体模型对包含有浮力和密度分层的两相湍流进行了数值模拟,计算结正确地反映了分层及紊动特征,与实测结果吻合较好     

淀山湖水生态系统的物质循环

为了解淀山湖水生态系统中氮、磷的循环过程与特征,于1990～1995年间在全湖布设的25个样点上调查、测定了淀山湖水生态系统中各营养级的种类组成、生物量、生产力,以及水质和底质情况;并估算了淀山湖氮、磷的主要输入与输出途径和数量。根据湖中生物体内氮、磷的含量建立了淀山湖水生态系统内氮、磷循环模式。氮、磷输入、输出统计表明,磷基本平衡,氮每年约有117.72t积累在湖中。淀山湖目前仍以有机污染为主,处在中营养向富营养湖泊的过渡阶段。各类水生生物对于维持淀山湖水生态系统的物质平衡具有重要作用。     

青藏高原东部生态系统土壤碳排放

在青藏高原探讨不同生态系统碳平衡规律及其影响因子并揭示其对全球含碳温室气体变化的影响与响应,有重要的现实意义和理论价值。分别在海北高寒草甸生态站、贡嘎山森林生态站和拉萨农业生态站用静态箱法进行了土壤CO₂排放的试验研究。土壤CO₂排放速率日平均值为草甸215.87～329.68mgCO₂m^-2h^-1,森林713.72～2102.56mgCO₂m^-2h^-1,农田913.05～1135.83mgCO₂m^-2h^-1。土壤碳排放速率日变化,在农田和高寒草甸区表现为单峰型,均以地方时8∶00～16∶00最高,0∶00～8∶00最低。草甸、农田土壤碳排放随着牧草、作物生长发育的加速而逐渐增加,越接近成熟(或枯黄期)其值越低,林区以6～9月的生长旺季为最高。土壤碳排放与温度之间有较好的相关性,温度是影响土壤碳排放的重要因子,全球变暖有可能引起高原土壤碳排放的增加。     

我国六价铬淡水水生生物安全基准推导研究

参照美国国家环境保护局(USEPA)"推导保护水生生物及其用途的国家水质基准的技术指南"的程序和规范,筛选了我国广泛存在的淡水水生生物物种,收集现有的急性和慢性毒性数据,结合课题组实验得到的部分本土生物毒性数据,分别采用物种敏感度排序法(SSR)、物种敏感度分布法(SSD)以及澳大利亚的水质基准技术方法对我国六价铬的淡水水生生物安全基准进行了推导。获得了我国淡水水生生物的六价铬的双值基准,3种方法得到的基准最大浓度(CMC)分别为23.97、22.84、29.06μg·L-1,基准连续浓度(CCC)分别为14.63、10.35、9.00μg·L-1,在同一个数量级上,但与美国的基准值有一些差异,建议使用SSD法推导CMC值和CCC值。研究结果可为我国水质基准的制定提供一些有用的基础资料。     

The Institute of Hydrobiology of the Chinese Academy of Sciences (1 p.)

- The Institute of Hydrobiology (IHB), Chinese Academy of Sciences (CAS) is located at the foot of Luojia Hill and beside the beautiful Donghu Lake in the City of Wuhan, Hubei Province, China. It was founded in 1930 as the Natural History Museum of Academia Sinica, and renamed as the Institute of Zoology and Botany of Academia Sinica in 1934. In 1944, it was divided into two institutes: The Institute of Zoology and Institute of Botany. In 1950, the main part of the Institute of Zoology, the sections of phycology in the Institute of Botany, and some members from other institutes and universities were merged into the Institute of Hydrobiology of the Chinese Academy of Sciences in Shanghai. The institute was moved from Shanghai to Wuhan in 1954.     

A Probabilistic Screening Model for Evaluating Pyrethroid Surface Water Monitoring Data

Synthetic pyrethroids have been detected in recent California surface water monitoring. Filtration is avoided during sample workup because pyrethroids are extremely hydrophobic, tending to sorb to most surfaces. The resultant analytical pyrethroid concentrations reflect both dissolved pyrethroid and pyrethroid associated with suspended sediment in the water column. Such “whole-water” analytical data are not directly comparable to aquatic acute toxicity effect concentrations measured in laboratory sediment-free water. Consequently, any potential aquatic toxicity risk is indeterminate. In this study a simple probabilistic model was developed to allow a screening-level assessment of pyrethroid whole-water monitoring data. The results suggest that water column toxicity of pyrethroids is possible in California's agriculturally-dominated tributaries, and indicate that additional monitoring to better characterize pyrethroid water-column concentrations are warranted. Model refinement will depend on future work that more firmly establishes the relationship between pyrethroid partitioning and bioavailability, and that addresses the potential influence of dissolved organic carbon on pyrethroid sorption and bioavailability.     

APPLICATION OF A MULTIPURPOSE UNEQUAL PROBABILITY STREAM SURVEY IN THE MID‐ATLANTIC COASTAL PLAIN1

ABSTRACT: A stratified, spatially balanced sample with unequal probability selection was used to design a multipurpose survey of headwater streams in the Mid‐Atlantic Coastal Plain. Objectives for the survey include unbiased estimates of regional stream conditions, and adequate coverage of unusual but significant environmental settings to support empirical modeling of the factors affecting those conditions. The design and field application of the survey are discussed in light of these multiple objectives. A probability (random) sample of 175 first‐order nontidal streams was selected for synoptic sampling of water chemistry and benthic and riparian ecology during late winter and spring 2000. Twenty‐five streams were selected within each of seven hydrogeologic subre‐gions (strata) that were delineated on the basis of physiography and surficial geology. In each subregion, unequal inclusion probabilities were used to provide an approximately even distribution of streams along a gradient of forested to developed (agricultural or urban) land in the contributing watershed. Alternate streams were also selected. Alternates were included in groups of five in each subregion when field reconnaissance demonstrated that primary streams were inaccessible or otherwise unusable. Despite the rejection and replacement of a considerable number of primary streams during reconnaissance (up to 40 percent in one subregion), the desired land use distribution was maintained within each hydrogeologic subregion without sacrificing the probabilistic design.