Distribution and abundance of littoral benthic fauna in Canadian prairie saline lakes

The littoral benthos of 18 lakes in Alberta and Saskatchewan ranging in salinity from 3 to 126 (g1^–1 TDS) were investigated twice, in the spring and in the summer of 1986. Multiple Ekman dredge samples were taken at water depths of about 0.5, 1.0 and 2 metres in each transect. Two to three transects were used in each lake according to its estimated limnological diversity for a total of 114 stations. A total of 76 species was present varying from 29–31 species in the three lakes of lowest salinity (means of 3.1–5.55) to only 2 species in lakes exceeding 100. Species richness decreased rapidly in salinities greater than 15.Biomass maximum mean of 10.91 g m^–2 dry weight (maximum 63.0 g m^–2) occurred in culturally eutrophic Humboldt Lake (3.1) but one third as great in other low salinity lakes. However, biomass again increased to about 4.5 gm^–2 in two lakes of 15 As the salinity increased still further biomass declined steadily until a minimum of 0.0212 g m^–2 was recorded in most saline Aroma Lake (mean 119). Summer biomass (11 lakes) was greater than spring biomass (4 lakes) because some groups such as amphipods, corixids and ostracods became more abundant in summer. Wet weight biomass averaged 15.8 of dry weight biomass.Seasonality (spring or summer), sediment texture and organic matter content, water depth, pH, salinity (TDS) and the presence of aquatic plants ( plant cover) were considered in the matrix involving species dry weight biomass at each of 117 stations. TWINSPAN classification of the samples yielded a dendrogram with 18 indicator species. Successive dichotomies divided these indicator species into four main lake groups based on salinity, i.e., Group I: 3–10 (Gammarus, Glyptotendipes I, Chironomus cf. plumosus), Group II: 10–38%. (Hyalella, Enallagma,Bezzia), Group III: 38–63 (Hygrotus salinarius, Cricotopus ornatus), Group IV: >63 (Dolichopodidae, Ephydra hians). Each of these main groups was subdivided into smaller groups of lakes based on factors such as pH, seasonality (spring or summer species dominance), organic matter and plant cover. Depth of samples played no apparent role.     

Benthic fauna in a series of lakes displaying a gradient of pH

The benthic fauna was examined in a series of four isolated headwater lakes, displaying a pH gradient of 5.4–7.0. A slight reduction in number of taxa present occurred below pH 6, with the fauna below 3 m dominated by the Diptera. Although epibenthic gastropods were rare, in contrast with European studies, Amphipoda, Ephemeroptera and Pisidium were common in the least buffered lake, which experiences spring pH values as low as 4.7. There were little relation between the pH or alkalinity, and the abundance, and biomass of the fauna at depths greater than 3 m. However, biomass of the littoral fauna increased significantly in the lakes with lower pH, as a result of an increase in large littoral species normally susceptible to fish predation.     

Development and use of a system for predicting the macroinvertebrate fauna in flowing waters

Abstract R iver I nV ertebrate P rediction A nd C lassification S ystem (rivpacs ) is a software package developed by the Institute of Freshwater Ecology (IFE) for assessing the biological quality of rivers in the United Kingdom. The system can be used to generate site-specific predictions of the macroinvertebrate fauna to be expected in the absence of major environmental stress. Each prediction is based on a small number of environmental features that are used to characterize the site. The fauna predicted can then be compared with the fauna observed at the same site. This offers a procedure for evaluating biological quality with application in river management both at the local level and for national surveys. Close collaboration between the IFE team and biologists in the water industry during the project had a beneficial influence on the operational development of the system. A second feature of RIVPACS is the national classification of sites, based on the macro-invertebrate fauna. Although the classification is currently a pre-requisite for the prediction system, it also has intrinsic value because newly sampled sites of high biological quality can be placed within the national framework, based on their macroinvertebrate fauna. This facility is of interest to the statutory nature conservation bodies as an element in their site appraisal procedures. The predictive component of the current version of the system (RIVPACS n) was used in the 1990 River Quality Survey to assess the biological quality of almost 9000 sites throughout the United Kingdom. Further developmental work is now under way to provide a more comprehensive version of the system for the 1995 survey.     

The distribution of microcrustacea in the littoral zone of a freshwater lake

The distribution of microcrustacea in the water column, sediments and on different macrophyte species was examined in the littoral zone of Jack Lake, Nova Scotia, Canada. Large numbers of microcrustacea occurred in association with macrophytes, suggesting that this habitat should receive greater attention in future studies of microcrustacean numbers, biomass, and production. The relative abundance of different microcrustacea varied considerably among sediments, macrophytes and water column samples. Although microcrustacean species composition differed among macrophyte groups, consistent differences in absolute numbers per gram could not be demonstrated. Epiphytic microcrustacean community structure also varied among depth strata in Jack Lake. Few epiphytic and benthic microcrustacea migrated into the water column on a diurnal basis.     

The structure of the littoral: effects of waterlily density and perch predation on sediment and plant‐associated macroinvertebrate communities

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Quantile regression analysis as a predictive tool for lake macroinvertebrate biodiversity

The Water Framework Directive introduced in Europe major changes to improve the management of water resources. This study aims to highlight some of the potential implications of its implementation for lake water monitoring in Italy. A Life+ project was launched to plan the first monitoring of lake macroinvertebrates standardized at the national level.Quantile regression analysis was used to explain different metrics of diversity describing macroinvertebrate communities in response to twenty-one variables representing chemical, physical and morphological characteristics of the environment. Nine lakes located in two Italian regions (Piedmont and Sardinia) were analyzed covering a wide trophic spectrum, from oligotrophy to hyper-eutrophy. The lakes were sampled following the national standardized protocol with samples covering the three recognized lake zones: littoral, sublittoral, profundal.The studied lakes had high chemical variability with conductivity ranging between 53 and 561 μS/cm, pH between 6.5 and 9.1, and alkalinity between 14 and 398 mg/l. The bottom sediments were characterized by fine sand (range 51–99%), followed by silt (1–35%) and clay (0–28%). When the Lake Habitat Survey was also applied to these lakes, its synthetic indices (LHMS, Lake Habitat Modification Score and LHQA, Lake Habitat Quality Assessment) produced higher values in natural lakes (mean values ± SD: LHMS = 26 ± 7, LHQA = 57 ± 3) than in the reservoirs (LHMS = 22 ± 4, LHQA = 52 ± 6). In all lakes, macroinvertebrates mainly consisted of chironomids and oligochaetes characterized by relative abundances up to 80% and >90%, respectively.Using quantile regression to evaluate limiting responses, only two variables, namely sampling depth and oxygen percent saturation (oxygen content), resulted the ones that best explained all the analyzed metrics of diversity of the macroinvertebrate communities. Depth and oxygen were then used to suggest synthetic models describing the various metrics of potential community diversity. These models can help the environmental agencies responsible for monitoring at the national level in distinguishing entire lakes or part of them with high biodiversity from those in altered conditions and then address remediation efforts toward the water bodies with the most critical conditions. Such approach could also be used to optimize the sampling procedures for the application of the Benthic Quality Index for lakes currently adopted at national level.     

Benthic macroalgae as a dispersal mechanism for fauna: influence of a marine tumbleweed

Effective dispersal is problematic for benthic organisms without planktonic larvae; rafting and vertical migrations are mechanisms that can potentially be employed by such fauna, but these strategies entail considerable predation risk as well as other disadvantages. Unattached, but non-floating, “drift” algae harbor large numbers of fauna and may serve as an alternative dispersal mechanism in some systems. This paper reports field manipulations in Florida Bay, Florida, USA designed to determine (1) if such algae can disperse benthic animals, and (2) if dispersal efficiency varies as a function of two common substrata types: seagrass and bare sediment. A live immersion stain was used to mark faunal associates of Laurencia spp. algal clumps in situ. The fidelity of molluscs, decapods, ophiuroids, and fishes to stationary algal clumps was then compared with the fidelity of these animals to clumps that were forced to tumble over a given distance with a blower apparatus; these experiments were performed over both sand and seagrass substrata. Measurements of frequency, spatial extent, and rate of algal drift were made to aid in assessing the potential importance of benthic algae as a dispersal mechanism.

Algal clumps often rolled in a manner similar to that of terrestrial tumbleweeds; mark-recapture work showed that algal clumps can move up to 0.5 km/day and that algal drift is a frequent phenomenon. The algal masses were effective transporters of benthic fauna, including mobile shrimps and fishes; dispersal was more efficient over sand than over seagrass. Dispersal of fauna via this mobile habitat should entail lower risk than other adult dispersal stratagems such as vertical migration or rafting; this mechanism would be most advantageous for brooding species or those with limited planktonic phases. Differential fidelity to clumps tumbling across seagrass versus sand suggests that the algae could facilitate exchange of fauna between isolated seagrass patches.     

The orthopteroids of the Seychelles: a threatened island fauna

Although they are conspicuous components of the native fauna, the orthopteroid insects of the Seychelles islands have attracted little attention from ecologists and conservationists throughout most of the twentieth century. Yet, at a complex crossroads, where the Afro-tropical, Malagasy and Oriental faunal regions overlap, they are potentially valuable biogeographical indicators in a region with an extremely complex palaeogeography. The taxonomic isolation of a number of species, incipient speciation among others, as well as possible interisland divergence in some cases make them worthy subjects of evolutionary studies. Most of the endemic species are indicators of undisturbed habitats and some play a role in food chains as the prey of endemic birds and hunting wasps (Sphecidae). The Seychelles orthopteroids are vulnerable to habitat disturbance caused by human activity and are now mainly confined to patches of native vegetation. They are threatened by further encroachment and by introduced predators and competitors.     

Transport and deposition of macrophytes to the dysphotic bottom of coastal waters

Some macrophytes are transported to the deep-sea bottom and are utilized by heterotrophs in the deep-sea as a food source. We inferred the transport route of macrophytes toward the deep-sea based on similarity in the species compositions of macrophyte pieces collected from the dysphotic bottom off the Izu Peninsula and the drifting macroalgae reported for the study area. We also examined whether or not the macrophytes are buried in the sediment, based on stable isotope distributions of organisms. Macrophytes collected by dredging at a depth of 100-300 m included 93 species, whereas 43 species were found by trawling at depths from 200 to 400 m. Only 15 of 76 dredged species (19.7%) that were identified to the species level were identical to the drifting macroalgal species reported for this area, whereas 15 of the 29 trawled species (51.7%) that were identified to the species level were identical to the reported drifting species. It was thus inferred that macrophytes were mainly transported through sliding along the sea bottom for the macrophytes collected by dredging and through sinking from the surface water for the macrophytes collected by trawling. The δ¹³C of sedimentary organic matter (SOM) from the 200-300 m zone was similar to the δ¹³C distribution of particulate organic matter in the surface water reported for the study area. The SOM in the zone likely originated from almost exclusively phytoplankton. In contrast, the ¹³C of SOM was significantly more enriched in shallow areas ≤100 m deep. We infer that not only phytoplankton but also macrophytes could supply organic matter to heterotrophs on the shallow bottom.     

The macroinvertebrate fauna and hydrogeology of springs in central Sweden

The macroinvertebrate fauna of 23 springs in central Sweden was sampled. A total of 79 taxa was recorded, including three crenobiont, nine crenophilic, 33 lotic, 11 lentic and 21 ubiquitous taxa. Only eight were non-insect taxa. Geological and hydrogeological maps were used to categorize each spring, resulting in eight glaciofluvial, 11 moraine and four limestone springs. Faunal composition and environmental factors showed an overall similarity among spring types, except for geographic position, the almost exclusive occurrence of crenobionts in glaciofluvial springs, and factors associated with high concentrations of calcium carbonate in limestone springs. Canonical correspondence analysis showed that the crenobiont caddisflies Parachiona picicornis(Pictet), Crunoecia irrorataCurtis were associated with high discharge and high summer temperature. Lotic taxa, including the stonefly nymph Isoperla grammatica(Poda), the caddis larvae Halesussp. and the mayfly nymph Baetis bundyaeLehmkuhl, were associated with high discharge and low summer temperature, while many lentic and ubiquitous taxa, e.g. dytiscids, were characteristic of small springs. It is suggested that the dominance of insect taxa, and the restricted occurrence of crenophilic and crenobiont taxa, are consequences of the glacial history and/or the hydrogeological setting of springs. Also, the possible influence of `diffusive rarity' of C. irrorataand P. picicornis, is discussed.     

Cartography of littoral rocky-shore communities (CARLIT) as a tool for ecological quality assessment of coastal waters in the Eastern Adriatic Sea

Littoral cartography is a valuable tool which uses shallow water macroalgal communities for monitoring ecosystem health and water quality. Cartography of littoral rocky-shore communities (CARLIT) is a European Union Water Framework Directive-compliant monitoring method widely used in the Western Mediterranean Sea. This non-destructive method is based on a visual observation of the type and length of coast occupied by rocky-shore communities in the upper-sublittoral zone. Here we present the first wide-scale application of CARLIT in the Adriatic Sea. The reference values calculated specifically for the Croatian coast (Eastern Adriatic Sea) ensure accurate calculation of the ecological status. The measured ecological quality ratio values (EQR) show a good linear relation with the Land Uses Simplified Index (LUSI) and appropriately reflect an increase in nutrient concentrations. The results suggest that this method can be used as a reliable biomonitoring tool in the Eastern Adriatic Sea. This study highlighted that Cystoseira forests thrive in 39% of the surveyed coastline and 23% of the coastline seems to be subjected to overgrazing by sea urchins. Our results provide a spatially accurate information on the abundance of different upper-sublittoral communities and the associated ecological status, which can be used in future management plans for improving water quality.     

红树林水生动物栖息地功能及其渔业价值

红树林生长于热带、亚热带海陆交界的生态敏感带,其根系为生活于潮间带高度异质环境下的生物提供了适宜生境:藻类、双壳类、甲壳类等大量附生于红树根部;红树的呼吸根、支柱根、树干、倒落的枝条和残骸等,与沉积物形成的松软基质为大量底栖动物提供栖息地,根部结构间的空隙成为虾类、蟹类和鱼类等游泳动物的优良避难所和索饵场。红树林凋落物以碎屑形式进入食物网,连同浮游植物、附生藻类和底栖微藻等,是红树林生态系统的碳循环重要组成部分,为红树林区水生动物提供了丰富的食物来源。可见,食物来源丰富、隐蔽性强、捕食压力低等特点使得红树林成为水生动物的理想栖息地,许多水生动物选择在其中度过部分或完整生活史。另外,红树林也是重要经济动物(鱼、虾、蟹类)的育苗场,为近岸鱼类种群的补充和渔业活动提供支持。为合理开发红树林区渔业和有效保护红树林湿地生态系统,从生境价值、凋落物在红树林生态系统食物网中的贡献等方面总结了红树林栖息地功能及其渔业价值,提出今后的研究方向应将红树林的栖息地功能从其它河口、近岸栖息地中分离出来,甄别不同栖息地间的动态关系及其对渔业的影响。     

中国蛱蝶科昆虫地理分布与区系分析

分析了中国蛱蝶科已知324种昆虫的分布与区系组成,主要由古北区、东洋区、古北一东洋区共有种类组成,共计309种,占总数的95．37％;其种类组成与澳洲区、新北区有明显差异;特有种类较少,占总数的12．65％;广布种很少,仅占1．74％。同时统计分析了324种蛱蝶在我国各省的贫富指数。     

Summer zooplankton dynamics in the limnetic and littoral zones of a humic acid lake

The limnetic and littoral zooplankton were studied during summer 1989 in Triangle Lake, a humic acid (pH 4.9) bog lake in Ohio, USA. The limnetic zooplankton showed low species richness and biomass, and dominance by the rotifers Kellicottia bostoniensis and Polyarthra vulgaris. In the littoral, species richness and biomass were markedly higher, and the crustaceans Alona guttata, Ceriodaphnia quadrangula, Chydorus sphaericus, Simocephalus serrulatus and Tropocyclops prasinus, and the rotifer Ascomorpha ecaudis were the dominants. The extreme rotifer dominance and lack of cladocerans in the limnetic zone were likely the result of Chaoborus predation. A pronounced mid-summer decline in cladoceran biomass in the littoral was likely due to predation by T. prasinus and Utricularia (bladderwort).     

Nearest-neighbor classifier as a tool for classification of protein families

Knowledge about protein function is essential in understanding the biological processes. A specific class or family of protein shares common structural and chemical properties amongst its member sequences. The set of properties that display its unique characteristics for clearly classifying a protein sequence into its corresponding protein family needs to be studied. Our study of these important properties conducted on four major classes of proteins namely Globins, Homeoboxes, Heat Shock proteins (HSP) and Kinase have shown that frequency of twenty naturally occurring amino acids, hydrophobic content of protein, molecular weight of protein, isoelectric point of protein, secondary structure composition of amino acid residues as helices, coils and sheets and the composition of helices, coils and sheets in the secondary structure topology plays a significant role in correctly classifying the protein into its corresponding class or family as indicated by the overall efficiency of Nearest Neighbor Classifier as 84.92%.     

Remote sensing evidence for the episodic transport of phosphorus from the littoral zone of a thermally stratified lake

• 1 Esthwaite Water in Cumbria is a small, thermally stratified lake fringed with beds of reed in the shallow littoral. In this study, we used a combination of in situ measurements and airborne remote sensing to investigate some of the physical processes influencing the transport of water and nutrients from the littoral zone.
• 2 The analysis of water samples collected from the reed beds, the littoral zone and the open water showed that significantly higher concentrations of dissolved reactive phosphorus (DRP) were frequently recorded in the reed beds in early summer.
• 3 Experiments with surface and near‐surface free‐running drogues demonstrated that the movement of water from the littoral zone was strongly influenced by the development of a secondary thermocline. When there was no secondary stratification, the surface currents generated by light winds seldom exceeded 2 cm s^‐1. When a secondary thermocline was present, surface current speeds of 5–10 cm s^‐1 were recorded even when the wind speed was less than 200 cm s^‐1.
• 4 A series of thermal surveys using a Daedalus Airborne Thematic Mapper (ATM) demonstrated that plumes of warm water frequently developed in the littoral zone when the weather was calm. Some of these plumes covered several hundred square metres and persisted for several hours. Others were only a few metres in width and acted as episodic ‘pumps’ that appeared and dispersed in less than an hour.

     

Ecohydrology as a new tool for sustainable management of estuaries and coastal waters

Throughout the world, estuaries and coastal waters have experienced degradation. Present proposed remedial measures based on engineering and technological fix are not likely to restore the ecological processes of a healthy, robust estuary and, as such, will not reinstate the full beneficial functions of the estuary ecosystem. The successful management of estuaries and coastal waters requires an ecohydrologybased, basin-wide approach. This necessitates changing present practices by official institutions based on municipalities or counties as an administrative unit, or the narrowly focused approaches of managers of specific activities (e.g., farming and fisheries, water resources, urban and economic developments, wetlands management and nature conservationists). Without this change in thinking and management concept, estuaries and coastal waters will continue to degrade, whatever integrated coastal management plans are implemented. To help in this process of change there is a need to (1) develop a profound understanding of the effects of biota and biotic processes on mediating estuary response to changing hydrology, sediment and nutrient flux and of the biota on hydrology at the river basin scale, and (2) to develop science-based remediation measures at the river basin scale, with elements of ecohydrology and phytotechnology at their core, to strengthen the ability of the biota to sustain and adapt to human-induced stresses.This revised version wa published online in March 2005 with corrections to the issue cover date.     

Sources of organic carbon in the littoral of Lake Gooimeer as indicated by stable carbon isotope and carbohydrate compositions

The relative importance of potential carbon sources in the littoral of Lake Gooimeer, a lake in the centre of the Netherlands, was studied using a combination of ¹³C/¹²C-ratio analysis and carbohydrate composition analysis. The littoral is covered on the land side by a 80 m wide Phragmites australis bed. Potential carbon sources were macrophyte litter, seston and benthic algae. Samples of potential carbon sources, sediments and benthic macrofauna from inside and outside the bed were analyzed for their¹³C/¹²C-ratio and some for their carbohydrate composition. Results indicate that inside the bed, macrophyte litter was the main source of carbon for both the sediment organic matter and the benthic macrofauna, and that algal material was of minor importance. Outside the bed, production by benthic algae was the main carbon source, with seston as a second source. No macrophyte derived material could be detected outside the reed bed.Abbreviations DOC (Dissolved Organic Carbon) - SOM (Sediment Organic Matter)     

东营盐生植物园土壤动物群落多样性研究

【背景】生物多样性是生物安全的重要内容之一,其包括基因多样性、物种多样性和生态系统多样性3个方面。环境污染、农药污染、重金属污染、海水倒灌、人类活动等诸多因素导致了物种多样性的降低。保护生物多样性是黄河三角洲大规模开发建设必须考虑的关键问题之一。【方法】用Tullgren干漏法分离、采集山东省黄河三角洲地区东营盐生植物园的土壤动物标本,对其多样性进行研究。【结果】蜱螨目是该地区的主要优势类群,占捕获土壤动物总数量的78．95％;另一优势类群为弹尾目,占捕获土壤动物总数量的14．03％;膜翅目和鞘翅目是常见类群,分别占捕获土壤动物总数量的3．57％和1．43％;其他均为稀有类群。在调查的10块样地中,优势类群弹尾目个体数量变化明显,在不同样地问的分布数量存在明显差异。东营盐生植物园土壤动物多样性与均匀度变化规律一致。【结论与意义】蜱螨目、弹尾目、膜翅目和鞘翅目构成了东营盐生植物园土壤动物的主体,对该区土壤动物群落多样性特征起着决定性作用。该区稀有类群多,但稀有物种数量较少,如不采取有效措施,该区的稀有物种随时有灭绝的危险。同时,盐胁迫作用的增强,能够影响土壤动物的数量与分布。因此,我们应在关注盐碱地改造进程的同时,更加关注该区土壤动物多样性的变化。