The disruption and recovery of fish communities in the Indian River Lagoon, Florida, following two hurricanes in 2004

During the summer of 2004, four hurricanes (Charley, Frances, Ivan, and Jeanne) affected Florida between August 13 and September 27. Two storms (Frances: category 2 and Jeanne: category 3) made landfall in the southern portion of the Indian River Lagoon (IRL) on the east-central coast of Florida. The presence of Florida Fish and Wildlife Conservation Commission's long-term fisheries monitoring program in the IRL provided a unique opportunity to examine the effects of large tropical events on estuarine fish communities. Increased sampling efforts to monitor the effects of tropical disturbances on the fish community within the IRL and one of its major tributaries (St. Sebastian River) were initiated within days after the passing of the last hurricane (Jeanne). The objectives of the study were to characterize changes to the composition of the fish community within the lagoon and river immediately after the passage of two hurricanes, and to examine the recovery of the fish communities. Analyses indicated that immediately after the last hurricane passed, community diversity within the estuary decreased following these storms due to the absence of many marine species, whereas the fish community within the St. Sebastian River shifted to one containing a greater percentage of freshwater species. Recovery of the community structure to pre-hurricane conditions was evident within several weeks following the last hurricane, and by mid December 2004 (ca. 3 mo after the last storm), there was little difference between the pre-hurricane and post-hurricane fish communities.     

Marine Chemistry in the Coastal Environment: Principles,Perspective and Prospectus

Marine chemistry of the coastal environment starts with principles of rock weathering that use carbonic acid to mobilize elements, only some of which comprise the majority of sea salt. The principle reason is reverse weathering, extensively represented in coastal waters, and returns most elements to newly formed colloids or minerals while recycling carbon dioxide to the atmosphere. This includes the deeper ocean expanse of sediment diagenesis, plus hydrothermal plumes and attendant low-temperature basalt alteration. Within the estuarine and extended shelf regimes, both conservative and non-conservative processes can be distinguished and modeled to determine proportions of weathered elements transmitted to the sea or consumed by reverse weathering. Conceptually, the steady-state processes that lead to the composition of seawater can be viewed as heterogeneous equilibria between dissolved constituents and solid mineral products taking hundreds of millennia. However, initial processes in the estuarine and coastal environment are characterized by shorter term scavenging associated with inorganic and organic colloids. These recycle both carbon and trace elements on timescales commensurate with estuarine flushing and coastal exchange with the ocean. The natural uranium and thorium decay series provide powerful tools for quantifying the rates of estuarine processes, including those within groundwater and the subterranean estuary. In the future, new mass spectrometric and nuclear magnetic resonance techniques will help to define the molecular nature of newly formed estuarine colloids as has been done for dissolved organic matter. As the coastal environment undergoes the forces of climate change in the form of warming and sea level rise, future research should address how these will impact chemistry of the coastal environment as a net source or sink of carbon dioxide and associated organic material.     

Flux of particulate matter in the tidal marshes and subtidal shallows of the Rhode River estuary

There was a net influx of suspended particulate matter to the uppermost part of the Rhode River estuary during the several years of this study. Most of the influx was due to episodic discharges of suspended sediment from the watershed during heavy rains. In contrast, tidal exchange of particulate matter was not related to rainstorms. Sediment composition data and historical records indicate that marsh accretion accounts for only 13% of the sediment trapping although marshes occupy 60% of the study area. Influx of particulate matter to the marshes is directly related to the amount of time they are submerged during tidal cycles.     

珠江三角洲近岸海洋地质环境与地质灾害调查主要进展及成果

通过遥感、水文和水化学、综合物探、地质取样、钻探以及静力触探等多种调查手段与方法,首次在我国重点经济区——珠江三角洲的近岸开展了1∶10万比例尺海洋地质环境与地质灾害综合调查,对调查区水域的海水化学要素、环境质量、水动力、地形地貌、沉积物、浅地层结构、潜在地质灾害以及海底工程地质条件进行了综合分析与研究,对海洋地质环境进行了综合评价与预警,并对该区海洋开发和工程建设提出了建议。     

A comparison of water-column macroinvertebrate communities in beds of differing submersed aquatic vegetation in the tidal freshwater Potomac River

Macroinvertebrates are a major food source for fish species and macrophyte beds are hypothesized to harbor a rich community of these organisms. Macroinvertebrates inhabiting the water column in two macrophyte beds and an adjacent open area were sampled in a small embayment of the tidal freshwater Potomac River. One macrophyte bed consisted of an almost complete monoculture ofHydrilla verticillata, while the second community was a more diverse mixture of plant species. In samples with substantial amounts of submersed aquatic vegetation (SAV), macroinvertebrate density was two orders of magnitude higher than and substantially more taxa were found than at the open water site. Total macroinvertebrate abundance was significantly greater at theH. verticillata site than at the mixed site in July, but no significant difference was observed in August. Taxa richness did not vary between the two vegetated sites in July but was higher in the mixed bed in August. While the two vegetated sites shared similar taxa, they differed in their abundance. TheH. verticillata site harbored more hydrobiid snails, and the mixed site was characterized by more chironomids and hydroptilid caddisflies. Differences between July and August collections were even greater than between sites. Numbers of hydroptilid caddisflies, baetid mayflies, and coenagrionid damselflies were substantially higher in August, while oligochaetes, hydrobiids, and chironomids were reduced. Results support the hypothesis that water-column macroinvertebrates are greatly enhanced in the presence of macrophytes. The ecological significance of the less substantial differences in macroinvertebrates between macrophyte beds requires further study.     

The ecological effects of structural flood mitigation works on fish habitats and fish communities in the lower Clarence River system of South-Eastern Australia

The effects of flood mitigation structures on the quality of estuarine and freshwater fish habitats in the lower Clarence River system of south-eastern Australia were investigated. Surrounding land use, fringing vegetation, overall level of habitat disturbance, distance from the sea, salinity, and water temperature were examined and compared between four sites on natural tributary streams, four sites on channelized flood mitigation drains gated at their mouths, and ten paired sites (five below and five above floodgates) on flood mitigation drains in this system, from mid 1988 to late 1990. Quantitative sampling of the fish fauna at each of these sites was conducted quarterly over this 21/2-yr period. Juvenile fishes were sampled using netting enclosures together with application of the ichthyocide rotenone, while subadults and adults were sampled using multiple-panel gill nets. In general, fish habitats in the flood mitigation drains, and especially those above flood gates, had more intensive surrounding land uses, less natural native fringing vegetation and, overall, were more highly disturbed than those in the natural tributaries. Salinity at the various study sites was largely dependent on the pattern of seasonal (mainly summer and autumn) rainfall and distance upstream from the sea. Salinities usually differed only slightly between gated and ungated sites at similar distances from the sea, indicating that the floodgates were generally ineffective in preventing the penetration of saline river water into the drains immediately above them. These gates were, however, very effective in preventing the establishment of fringing mangrove vegetation in the drains above them. The main ecological effects of these flood mitigation works have thus been to generally degrade the overall quality of available fish habitat, particularly in terms of reductions in natural fringing vegetation (mangroves in the more estuarine-dominated areas and overhanging terrestrial trees in the more freshwater-dominated areas often being replaced by grassess and rushes), and to increase the intensity of surrounding land use (natural forest often being cleared and wetlands drained for cattle grazing and sugarcane growing), both of these factors contributing to increases in generalized aquatic habitat disturbance. Results from the study of the fish assemblages in these natural and man-altered habitats revealed the following general patterns. Highest fish species numbers and abundances occurred in the ungated natural tributaries and in drains downstream of floodgates. These habitats also contained the largest proportions of both commercial fish species and individuals as well as the majority of species and individuals with marine-estuarine affinities. Both total and commercial fish species numbers generally declined with decreasing salinity and increasing distance of the sampling sites from the sea. Even through saline waters from the main river system penetrated the majority of the floodgates during most of the study period, fish passage through these gates was found to be very restricted. Fish assemblages above such gates were generally dominated by primarily freshwater species, as compared with primarily saltwater (estuarine-marine) species below. The conversion of the great majority of small mangrove-fringed tributaries in the lower reaches of this river system into uniform floodgated drainage channels has thus resulted in the destruction of, and impeded fish access to, large areas of previously available estuarine fish nursery and feeding habitat. These drainage changels are now dominated by terrestrial-freshwater vegetation above where they are cut off from the main river channels by the floodgates, and the period of their construction has coincided with that of reported declines in fish catches in this river system. On the basis of the above findings, it is recommended that these floodgates be left fully open at all times except immediately prior to and during floods in the river system, thus facilitating the re-establishment of fringing mangrove vegetation along the banks of the artificial drains in the lower reaches, generally improving flushing and thus water quality in these drains, and allowing the establishment of primarily estuarine-marine fish communities, including more species of economic importance, in them.     

Formation of Fe(III) oxyhydroxide colloids in freshwater and brackish seawater, with incorporation of phosphate and calcium

The formation of Fe(III) oxyhydroxide colloids by oxidation of Fe(II) and their subsequent aggregation to larger particles were studied in laboratory experiments with natural water from a freshwater lake and a brackish coastal sea. Phosphate was incorporated in the solid phase during the course of hydrolysis of iron. The resulting precipitated amorphous Fe(III) oxyhydroxide phases were of varying composition, depending primarily on the initial dissolved Fe/P molar ratio, but with little influence by salinity or concentration of calcium ions. The lower limiting Fe/P ratio found for the solid phase suggests the formation of a basic Fe(III) phosphate compound with a stoichiometric Fe/P ratio of close to two. This implies that an Fe/P stoichiometry of ≈2 ultimately limits the capacity of precipitating Fe(III) to fix dissolved phosphate at oxic/anoxic boundaries in natural waters. In contrast to phosphorus, the uptake of calcium seemed to be controlled by sorption processes at the surface of the iron-rich particles formed. This uptake was more efficient in freshwater than in brackish water, suggesting that salinity restrains the uptake of calcium by newly formed Fe(III) oxyhydroxides in natural waters. Moreover, salinity enhanced the aggregation rate of the colloids formed. The suspensions were stabilised by the presence of organic matter, although this effect was less pronounced in seawater than in freshwater. Thus, in seawater of 6 to 33 ‰S, the removal of particles was fast (removal half time < 200 h), whereas the colloidal suspensions formed in freshwater were stable (removal half time > 900 h). Overall, oxidation of Fe(II) and removal of Fe(III) oxyhydroxide particles were much faster in seawater than in freshwater. This more rapid turnover results in lower iron availability in coastal seawater than in freshwater, making iron more likely to become a limiting element for chemical scavenging and biologic production.     

Preliminary investigation of chloramphenicol in fish, water and sediment from freshwater aquaculture pond

Analytical methods of chloramphenicol in the aquaculture environment have been developed using high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry. The contents of chloramphenicol were determined using high-performance liquid chromatography for sediment and liquid chromatography-tandem mass spectrometry for fish and water collected from a freshwater aquaculture pond in China. Chloramphenicol in the water and sediment were 112.3 ng/L and 0.1957 mg/kg, respectively. The chloramphenicol residues in 3 kinds of fish, including carp, chub and grass carp were different. Only the muscle and head of grass carp were under the minimum required performance limit (0.3 μg/kg) and were safe to eat. The chloramphenicol in other tissues of grass carp, carp and chub exceeded the minimum required performance limit. The highest content of chloramphenicol was in the branchia of carp and the lowest was in the head of grass carp. The results showed the chloramphenicol in the aquaculture environment was serious, although the government of China had banned the use of chloramphenicol in aquaculture a few years ago.     

Geochemistry of hydroxy acids in sediments—I. Some freshwater and brackish water lakes in Japan

Series of α, β, ω and (ω-1) hydroxy fatty acids (FAOHs) were determined in several freshwater and brackish water lacustrine sediments in Japan. Analytical procedure used was digestion of the solvent-extracted sediment with HF/HCl followed by solvent and saponification extraction of the residue. Abundances of α/β and ω-FAOH determined by this procedure were 2–3 times higher than those obtained by single alkaline saponification and of the same order with those provided by HCl hydrolysis. Major portion of α/β-FAOH was obtained by solvent extraction of the acid-treated sediments, while subsequent alkaline saponification was needed for the majority of ω-FAOH to be recovered. Thus determined FAOHs comprised 33–61% (Av. = 42%) of the “bound” acid constituents in the lacustrine surface sediments. The α/β and ω-FAOH composition was principally the same among the samples examined, except for relative proportions of the iso to anteiso C₁₅ and C₁₇ ß(α)-FAOH, which showed significant variations in the ranges of 0.30–1.1 and 0.46–1.5, respectively. In the holomictic lakes, the ratios together with the same ratios of the “bound” branched monocarboxylic acids tended to decrease with increasing water depth of the lakes, suggesting that the ratios may indicate an extent of the early diagenetic alteration of the bacteria-derived lipids either in water column or in surface sediment.     

A freshwater population of the mummichog,Fundulus heteroclitus,from the Susquehanna River drainage in Pennsylvania

An established population of mummichog,Fundulus heteroclitus, in the Susquehanna drainage is reported from Pennsylvania for the first time. Three year classes of this brackish water species were taken on 17 August 1976 from Letort Spring Run, a tributary of the Conodoguinet Creek in Cumberland County. A survey of unpublished records and museum specimens revealed occurrences in Wissahickon Creek, Montgomery County, and Brandywine Creek, Chester County; both Delaware drainage. Presence in these drainages is believed the result of bait bucket introduction.     

频率域航空电磁法在雄安新区浅层(微)咸淡水调查中的应用

探明含(微)咸水地区的浅层咸淡水分界现状,对于当地浅层水资源的开发利用具有指导意义。笔者通过对雄安新区频率域航空电磁数据反演,得到地下浅层电性结构特征,进而推断新区浅层(微)咸淡水分界线。通过对比1998年、1999年两次水文地质调查咸淡水分界线,结合地面水文地质资料,笔者发现浅层地下水降落漏斗会影响咸水侵入的趋势:雄县东北处的昝岗—米家务—双堂一带(微)咸水侵入是由于昝岗水漏斗的存在而趋于稳定,但水漏斗也同时加剧了昝岗镇地区南部(微)咸水入侵;安新县城西侧由于容城水漏斗水位上升,相较1999年(微)咸水范围有所减少;高阳水漏斗地区水位持续下降,导致芦庄—高阳方向(微)咸水范围将继续扩大。通过预测的(微)咸水侵入趋势为新区建设中水资源的合理开发利用提供了数据依据。     

黄河三角洲滨海湿地健康条件评价

以黄河三角洲滨海湿地系统为研究对象,基于描述滨海湿地健康条件的4项功能,充分考虑滨海湿地生态地质环境系统的特征及其健康响应因素,建立了黄河三角洲滨海湿地健康条件评价的概念模型和指标体系。以统计监测和遥感数据为基础,采用RS和GIS技术,通过栅格化实现分区评价及其结果的优化整合,探讨了黄河三角洲滨海湿地健康的时空分布规律。结果显示：黄河三角洲滨海湿地现状健康条件处于健康的占14.2%,亚健康的占61.9%,一般病态的占23.9%;近期（2010－2015年）,河口三角洲湿地生境质量会逐步改善,向健康方向发展,而北部和南部部分滩涂区及神仙沟流路等局部地区在自然和人为因素的共同作用下,环境质量会有一定的降低;影响黄河三角洲滨海湿地健康条件的主要因素是全球气候变化背景下的区域水循环关键过程及其时空变化、湿地开发等人类负面干扰和黄河下游生态调度。应继续加大黄河下游生态调度的力度、积极实施生态修复工程,以促进黄河三角洲滨海湿地持续健康发展。     

Metabolism and organic carbon fluxes in the tidal freshwater Hudson River

We summarize rates of metabolism and major sources and sinks of organic carbon in the 148-k long, tidally influenced, freshwater Hudson River. The river is strongly heterotrophic, with respiration exceeding gross primary production (GPP). The P:R ration averages 0.57 (defined as the ratio of GPP to total ecosystem respiration) if only the aquatic portion of the ecosystem is considered and 0.70 if the emergent marshes are also included. Gross primary production (GPP) by photoplankton averages approximately 300 g C m^?2 yr^?1 and is an order of magnitude greater than that by submersed macrophytes. However, the river is deep, well mixed, and turbid, and phytoplankton spend a majority of their time in the dark. As a result, respiration by living phytoplankton is extremely high and net primary production (NPP) by phytoplankton is estimated to be only some 6% of GPP. NPP by phytoplankton and submersed macrophytes are roughly equal (approximately 20 g C m^?2 yr^?1 each) when averaged over the river. Emergent marshes are quite productive, but probably less than 16 g C m^?2 yr^?1 enters the aquatic portion of the ecosystem from these marshes. Heterotrophic respiration and secondary production in the river are driven primarily by allochthonous inputs of organic matter from terrestrial sources. Rates of metabolism vary along the river, with depth being a critical controlling factor. The P:R ratio for the aquatic portion of the ecosystem varies from 1 in the mid-river to 0.2 in the deeper waters. NPP is actually negative in the downstream waters where average depths are greater since phytoplankton respiration exceeds GPP there; the positive rates of NPP occurring upriver support a downstream advection of phytoplankton to the deeper waters where this C is largely respired away by the algae themselves. This autotrophic respiration contributes significantly to oxygen depletion in the deeper waters of the Hudson. The tidally influenced freshwater Hudson largely fits the patterns predicted by the river continuum model for larger rivers. However, we suggest that the continuum model needs to more clearly distinguish between GPP and NPP and should include the importance of autotrophic respiration by phytoplankton that are advected along a river. The organic carbon budget for the tidally influenced freshwater Hudson is balanced to within a few percent. Respiration (54%) and downstream advection into the saline estuary (41%) are the major losses of organic carbon from the ecosystem. Allochthonous inputs from nonpoint sources on land (61%) and GPP by phytoplankton (28%) are the major sources to the system. Agricultural erosion is the major source of allochthonous inputs. Since agricultural land use increased dramatically in the last century, and has fallen in this century, the carbon cycle of the tidally influenced freshwater Hudson River has probably changed markedly over time. Before human disturbance, the Hudson was probably a less heterotrophic system and may even have been autotrophic, with gross primary production exceeding ecosystem respiration.     

Chemical reactions of sea water with rocks and freshwater: Experimental and field observations on brackish waters in Israel

Four major processes are observed to take place in the coastal aquifer of Israel, detectable even in the short times of water contact with the carbonate-containing host rocks. Three are chemical reactions, Ca²⁺-Mg²⁺ exchange, Na⁺-Ca²⁺ or Na⁺-Mg²⁺ base exchange, SO^2?₄ reduction and the fourth is dilution by freshwater. These reactions and their effects on the chemical composition of the waters were demonstrated experimentally. The range of chemical changes observed in the laboratory experiments overlap the range of the studied natural waters. This indicates that simulation of geologically long-term rock-water interaction could be achieved in laboratory experiments even at low temperatures.     

Coastal Inundation due to Sea Level Rise in the Pearl River Delta,China

This paper examines the increased potential risk of tidalinundations in the Pearl River delta, China, due to futurerises in sea level. The research is based on tidal recordsof 54 tide gauges distributed across the delta plain, andemploys mathematical calculations to predict potentialrises of water level in different parts of the delta undera number of flood scenarios. After assessing a 72-yeartidal record of Hong Kong and factors such as estuarinebackwater effects and long-term geological subsidence,it suggests that a 30 cm rise in relative sea level at themouth of the estuary is possible by 2030. Based on theprediction and five freshwater discharge scenarios, thepotential impacts on water levels across the delta plain arecalculated. Three zones are identified as least affected,heavily affected and severely affected. The impacts arealso translated into return periods of water level. It issuggested that in a large part of the delta plain, returnperiods will be shortened and hence will be increasinglyvulnerable to tidal inundation. Finally, managementimplications are discussed along with assessment ofthe adequacy of the existing tidal flood defences, as well asevaluation of the cost implications if they are to be improved.     

渤海湾西北岸全新世介形类组合特征及海进海退旋回

距现代海岸25 km处的渤海湾西北岸宁河县兴坨H1孔(孔深28.0m)的介形类研究表明,可划分为7个组合层段(目下而上):Ⅰ-纯净小玻璃介组合(28.0~16.0m);Ⅱ-凹陷中华美花介-东台新单角介组合(16.0~9.0 m);Ⅲ-东台新单角介凹陷中华美花介-布氏威契曼介组合(9.0~4.5 m);Ⅳ-凹陷中华美花介-丰满陈氏介组合(4.5~2.5 m);V-丰满陈氏介-凹陷中华美花介组合(2.5~1.6m);Ⅵ丰满陈氏介-滨海弯贝介组合(1.6~0.5m);Ⅶ-玛纳斯土星介-布氏土星介组合(0.5~0m).通过对环境分析,认为渤海湾西北海岸自全新世以来古环境变化经历了一个完整的海侵序列,即自16.0 m向上至地表,从海进到海退为一个完整的沉积旋回.     

Microbial production and photobleaching of CDOM in an estuarine brackish lake on Chongming Island, Shanghai

Chromophoric dissolved organic matter （CDOM）, one of the important components in freshwater and seawater ecosystems, plays a role in underwater light absorption and primary productivity. The Lake Beihu was a part of the North Branch of the Yangtze （Changjiang） River estuary in the past, but now the Lake Beihu has become the biggest manmade brackish lake in East China. The lake is a unique brackish ecosystem, however, little study deals with the fate of CDOM in it and whether this type of lake ecosystem will face eutrophication problem. This paper focuses on the transformation of CDOM, and the impact of microbe and light in the Lake Beihu. Microbial production and natural photobleaching simulative experiment was done on water samples from the Lake Beihu, yielding the following results. Water samples were collected from the Lake Beihu in May 2006. The filtrates through Whatman GF/F filters and polycarbonate membranes （μm） were exposed to microbe and microbe plus light condition, respectively. Three-dimensional excitation emission matrix （3-DEEM） fluorescence spectra were analyzed. It was shown that the amount of CDOM increased with time in the microbe exposure experiment, which means that microbes may play an important role in the production of CDOM instead of degrading CDOM. The .productivity was enhanced with increasing temperature, e.g. the value of UV260 increased by 62.4% in 4.5 days at 30℃, 26.9% at 20℃, 5.0% at 10℃. In addition, photobleaching was observed in the study as other papers reported. With the impact of microbes, the fluorescence signal of fulvic acid became stronger as the time went by. At 30℃, the fulvic acid fluorescence, which was expressed by QSU, increased by 35%-39%.     

Parasites and cyclopoid predators of age-0 fish in the Roanoke River,North Carolina

Altered river flow has been suggested as a cause for the low recruitment of striped bass,Morone saxatilis, in the Roanoke River (North Carolina) because of its effect on the proximity of zooplankton and larval striped bass. This results in unsuccessful feeding and subsequent starvation, which was considered to be a major mortality factor. Other mortality factors, such as parasitism and copepod predation on age-0 fish, may also be regulated to some extent by changes in river flow. The relationship of cestode plerocercoids, trematode metacercaria, mussel glochidia, and cyclopoid copepod predators with age-0 fish was evaluated in the lower Roanoke River and western Albemarle Sound from plankton net collections made in 1984 to 1986 and 1988. Plerocercoid prevalence was higher under low river flow conditions than under high flow conditions in darters (Percidae; 16.7% vs. 9.2%), minnows (Cyprinidae; 28.8% vs. 4.7%), andMorone (1.9% vs. 0%). Gut analysis of the age-0 fish revealed that copepods (source of the plerocercoids) were a major diet component ofMorone and darters but not of minnows or herring (Clupeidae). Decreases in river flow were associated with increases in copepod density (Pearson r=?0.62; p=0.0001) and plerocercoid prevalence inMorone (Pearson r=?0.29; p=0.03). The low correlation value forMorone may be quite strong considering the complexity of the variables associated with prevalence. Metacercaria were found only inMorone and minnows, and prevalence and mean intensity were less than that found for plerocercoids. Mussel glochidia prevalence was less than 0.5% for all affected taxa, an order of magnitude less that that found in other studies. The low value may indicate that the mussel population in the Roanoke River is declining. Prevalence of attacks by the predatory copepodMesocyclops edax on age-0 fish was similar to that in Chesapeake Bay, and striped bass was the primary prey. Spatial and temporal proximity of copepods and fish prey may be the key factors in regulating copepod attacks. The low prevalence of parasites and copepod predators seen in this tudy would suggest that mortality from these sources may not be a major factor in age-0 recruitment in this system. Confirmation of these conclusions would require a more controlled experimental approach.     

Macroinvertebrates of a rocky shore in the freshwater tidal Hudson River

We studied the macroinvertebrate fauna of a rocky shore in the freshwater tidal Hudson River during 1992–1994, the early years of the zebra mussel (Dreissena polymorpha) invasion. The macroinvertebrate community was numerically dominated by chironomids, nematodes, oligochaetes, gastropods, zebra mussels, and planarian flatworms. The community was a mixture of species typical of stony warm water rivers and lake shores, freshwater generalists, and semiterrestrial species. Overall macroinvertebrate densities were moderate to low (2,800–14,600 m⁻²). Density was a strong function of season and elevation, with consistently low densities in the early spring and in the intertidal zone. This pattern suggests that physical harshness (alternating submergence and desiccation;ice and low temperatures) limits the distribution of invertebrates at this site. Zebra mussels occurred at our study site chiefly below the low tide mark, but only at moderate abundance (usually <1,000 m⁻²). A weak correlation between the densities of zebra mussels and those of other macroinvertebrates nonetheless suggests that the zebra mussel invasion may have affected community structure.     

Essential elements in the organs and tissues of fish depending on the freshwater toxicity and physiological state

The distribution of essential elements (Са, Mg, Na, K, Zn, Cu, Mn, Co) in organs and tissues in basins with different water toxicity is considered by the example of bream Abramis brama L. The models of redistribution of essential elements in the liver and kidney of the fish are developed depending on the physiological state, which is estimated by the concentration of hemoglobin in blood, total disease, and body mass index. It is shown that essential elements can serve as markers of intensity and direction of metabolic processes in the fish organism.