Effects of water-level fluctuations on lakes: an annotated bibliography

Water-level fluctuations (WLF) in lakes and rivers, especially their extent, frequency and duration, are dominant forces controlling the functioning of these ecosystems. In particular, WLF play an important role in the lake’s littoral and aquatic–terrestrial interface processes. WLF may take place on different spatial and temporal scales under natural conditions but water levels have been artificially modified in regulated lakes, and their impacts are expected to be enhanced within the actual global change scenarios with forthcoming management problems. This article presents an overview on the literature published on this important topic since 1991 by using journals indexed in the ISI Web of Knowledge. The overall objective was to examine temporal and spatial trends in publications on WLF, the specific aspect of WLF concerned and their main effects. Throughout the article we have used case studies to illustrate different effects of WLF on the variety of lake habitats and indicators that have been studied. Overall, the number of papers published on the subject since the 1990s has risen steadily, when less than ten papers were published each year; until 2006 and peaking in 2005. The greatest number of papers on WLF has been carried out in Europe and North America (c. 73%). These data also showed that the effects of WLF have not been studied equally for different groups of organisms. There is a greater interest on macrophytes, which are the most studied group of organisms (18.4% of the papers). Nearly 7% of the papers deal with algae, and zooplankton and invertebrates account for a 7% followed by fish. WLF effects on ecosystems are very complex, and the biological effects in lakes are greatest in shallow water and littoral areas, where even small changes in water levels can result in the conversion of large areas of a standing-water environment in air exposed habitats. Finally, these data might serve to highlight knowledge gaps still existing on this topic and, in particular, some of the approaches that can potentially contribute to solve several of these lacunae are explored.     

Environmental gradients determining the distribution of benthic macroinvertebrates in Lake Takkobu, Kushiro wetland, northern Japan

Effects of environmental variables on the distribution of benthic macroinvertebrates inhabiting sediments were studied at 25 sites along the shoreline of Lake Takkobu in the Kushiro wetland of northern Japan in summer 2003. During the last decade, the lake’s status has undergone a drastic shift from clear water dominated by submerged macrophytes to turbid water dominated by phytoplankton. The canonical correspondence analysis showed that four environmental variables explained the significant variation in the macroinvertebrate species composition: submerged plant biomass, bottom sediment organic matter content (OMC), distance from the mouth of the Takkobu River, and bottom-layer pH. Five species of Chironomidae [Chironomus sp. (except plumosus group), Psectrocladius sp., Corynoneura sp., Parachironomus sp. arcuatus group, and Zavreliella sp.] occurred in sites with relatively lower pH and a high submerged plant biomass, whereas three species of Tubificidae (Tubifex tubifex, Aulodrilus limnobius and Aulodrilus sp.) and two of Chironomidae (Nanocladius sp. and Monodiamesa sp.) occurred in sites with high pH and little vegetation. The three Tubificidae species also preferred organic-rich sediments. Irrespective of aquatic vegetation, Sphaerium sp. (Bivalvia) and Monodiamesa sp. (Chironomidae) occurred in low-OMC sites, whereas Tanypus sp. (Chironomidae) preferred high-OMC sites. The number of macroinvertebrate taxa showed the highest correlation with the number of submerged plants, suggesting that macroinvertebrate species richness was related mostly to submerged plant species diversity in this lake. The quantity and species richness of submerged plants and OMC are thus important determinants of the community structure of macroinvertebrates inhabiting sediments in Lake Takkobu.     

Biogeographical patterns of benthic macroinvertebrates in the Southeastern Pacific littoral

Aim To use new collections and taxonomic reviews of the Chilean coastal biota, and studies on biodiversity on a reappraisal of Southeastern Pacific littoral biogeography. Location The temperate coastline of the Southeastern Pacific, extending over 6000 km from northern Peru to the southern tip of Chile. Methods Records of coastal macroinvertebrates were assigned to ten geographic zones along the Chilean coast. The Spearman rank correlation coefficient, ρ, was used to establish the relationship between the total number of species and the number of single records for each zone. Regions and underlying faunal gradient were verified via an unweighted paired group method using arithmetic averages (UPGMA), and ordination non-metric multidimensional scaling (nMDS) analysis based on a disagreement distance matrix of presence/absence data. Abundance down-weighting was preferred to rare species down-weighting, owing to the nature of the records, where a larger number of references for a given taxon did not necessarily indicate a greater abundance or commonness. The dissimilarity matrices between the different zones were used to establish the degree of agreement between the different levels of analysis, using a weighted Spearman rank correlation coefficient ρ_w. Statistical significance was established using a randomization (permutation) test. Main conclusions Analysis of new macroinvertebrate data and taxonomic reviews of the Chilean coastal fauna indicates a Transitional-Temperate Region for the Southeastern Pacific littoral, located between 35°S and 48°S where a gradual mixing and replacement of species negates previous hypotheses on the existence of a marked distributional break at 42°S.     

Changes in the water level of Lake Peipsi and their reflection in a sediment core

A comprehensive study (chronological, lithological and geochemical) of an 8.5 m postglacial sediment sequence from Lake Peipsi was conducted to elucidate the effects of lake-level changes on the sedimentary environment and biogeochemical dynamics in a large lake. Four lithological units were distinguished in the sediment sequence studied: clayey silt, slightly laminated greyish carbonaceous gyttja, brownish-grey gyttja and dark gyttja. These units indicate that large shifts in sedimentation processes occurred in the past. The sediment data show that fluctuations in water depth had a profound impact on the lake environment, recorded as changes in the lithological composition, phosphorus content of sediments and composition of diatom assemblages. The corresponding changes are best reflected in sediments accumulated during phases of regression when the lake area was also smaller. As the water depth and area of the lake increased, wave-induced erosion and resedimentation smoothed or even disturbed the initial information. The increase of phosphorus content in the unconsolidated, high-porosity surface sediments (0.5 m) is most probably connected with active diffusion and matter exchange between the water-sediment pools.     

东湖沿岸带底栖藻类群落的时空变化

武汉东湖是一个浅水富营养湖泊,其沿岸带底栖藻类群落的季节分布特征明显,夏季的优势种群是一些体积很小的硅藻类曲壳藻(Achnanthes spp.),其他大部分季节是绿藻门的团集刚毛藻(Cladophora glomerata)和硅藻门的变异直链藻(Melosira varians)。不同样点间的底栖藻类现存量差异不显著,但优势种类不同,以团集刚毛藻为优势的绿藻在处于中富营养区域的磨山样点比例最高,以变异直链藻为优势种的硅藻在严重富营养化的水果湖样点中比例最高。底栖藻类月平均现存量(以叶绿素a计)的时间变化格局为夏季最低(41.5μg/cm2),逐渐增加到秋、冬季节的最高峰值(55.3μg/cm2)。造成东湖夏季底栖藻类现存量低的原因是雨季水体环境的不稳定性和水位升高造成的低光照。不同样点间的chlb、chlc及chlb/a、chlc/a值具有显著差异,分析这种差异显示:在东湖的富营养化条件下,过渡的富营养化能增加底栖藻类群落中硅藻的比例,却降低了绿藻的比例;不同环境条件下的底栖藻类群落结构具有特异性,分析底栖藻类群落结构可以用来评价水环境健康状况。东湖底栖藻类现存量的季节变化规律与浮游藻类不同,它和水温成显著的负相关,但温度和浮游藻类并不是影响东湖沿岸带底栖藻类生物量变化的直接因子。团集刚毛藻等底栖丝状藻类给各种底栖动物提供了食物和栖息环境,在东湖生态系统中具有重要的作用和功能。     

松花江流域大型底栖动物群落结构与水质评价

【目的】松花江流域是中国最早的工业基地之一,其水生态环境遭到严重破坏,环境保护工作面临巨大挑战。开展松花江流域水质评价及典型生物类群多样性状况调查,可为松花江流域生态系统的保护和修复提供依据。【方法】于2016年7月调查整个松花江流域近岸的大型底栖动物群落组成和测定水质理化指标,开展其水质理化特征评价和生物指数评价,并探讨底栖动物群落分布与水环境因子间的关系。【结果】理化指标评价结果显示,南源松花江水质状况最差,处于中度污染;北源松花江处于轻度污染;梧桐河水质最好,处于良好状态。松花江流域3个河段的底栖动物群落结构存在空间差异性。另外,梧桐河的物种多样性最高,北源松花江次之,南源松花江最低。溶解氧和营养元素K的浓度是驱动底栖动物群落组成发生显著性差异的主要环境因子。生物指数评价结果显示,3个河段水质均处于轻度污染状态。【结论】松花江流域水质处于轻度到中度污染状态。有机污染是松花江流域面临的主要水质环境问题,对松花江流域底栖动物群落结构产生了显著影响。因此,控制有机质的输入是维持松花江流域水生态系统平衡的重要举措之一。     

扬州宝应湖底栖大型无脊椎动物的生物多样性及其变化

底栖大型无脊椎动物作为水环境监测的重要指示生物, 其群落结构和多样性能够有效地反映水环境的健康状况。为了更好地了解扬州宝应湖大型底栖动物的群落多样性, 本文于2015-2019年对扬州宝应湖底栖大型无脊椎动物进行野外调查和采样, 联合经典形态学和高通量测定DNA条形码方法进行物种鉴定, 进一步分析了这些大型无脊椎动物群落结构和多样性的年度变化, 并应用Shannon-Wiener指数(H′)和污染生物指数(biotic index, BI)对水质状况进行生物评价。结果显示: 共记录大型底栖动物3门5纲57种, 其中软体动物门23种, 隶属2纲9科(腹足纲7科15种, 双壳纲2科8种); 环节动物门寡毛纲12种, 隶属2科; 节肢动物门22种, 隶属2纲6科(软甲纲4科5种, 昆虫纲2科17种)。腹足纲是优势类群, 5年间的密度占比均在65%以上。优势种是赤豆螺(Bithynia fuchsiana)、槲豆螺(B. misella)和长角涵螺(Alocinma longicornis)。Margalef丰富度指数(2.27 ± 0.28)、Simpson优势度指数(0.82 ± 0.02)和Pielou均匀度指数(0.78 ± 0.08)在5年间呈现明显的波动变化。对水质状况的生物评价结果表明, 湖区水体环境在5年间均呈现不同程度的污染状态, 这与过度围湖水产养殖等经济活动引起水体富营养化有一定关系。     

Identification of priority areas for conservation in an arid zone: application of parsimony analysis of endemicity in the vascular flora of the Antofagasta region, northern Chile

Endemic taxa are those restricted to a specific area, and could bedefined as the exclusive biodiversity of a region. An area of endemismcontains taxa found nowhere else and could be catalogued as irreplaceable and of highpriority for conservation. proposed the parsimony analysis of endemicity (PAE) as a tool to detect areas ofendemism. PAE, a method of historical biogeography, is analogous to cladisticmethods used in phylogenetics analysis, and unites areas (taxa in cladistics)based on their shared species (characters in cladistics) according to the mostparsimonious solution. In this paper we determined with PAE, prioritary areasfor conservation on the basis of concentrations of endemic species in the aridregion of Antofagasta, northern Chile, and compared the results with theirrepresentation in the current Chilean National Parks and Reserves System. Wefound two areas suggested as priorities, one located in the north Andean zone ofthe region, and another at the coast. The area with the higher biodiversity andconcentration of endemics was that located at the coast. However, coastalecosystems are currently under-represented in the Chilean National Parks andReserves System. The establishment of a new protected area in the coastal zoneof the region of Antofagasta is currently under consideration, coinciding withthe area suggested with PAE as priority. This new area would not only allowconserving species with evident problems of conservation, but also preserving anarea where higher levels of endemism exist.     

Investigating the possible role of benthic macroinvertebrates and zooplankton in the life cycle of the haplosporidian Bonamia ostreae

Bonamia ostreae is a protistan parasite of the European flat oyster, Ostrea edulis. Though direct transmission of the parasite can occur between oysters, it is unclear if this represents the complete life cycle of the parasite, and the role of a secondary or intermediate host or carrier species cannot be ruled out. In this preliminary study, benthic macroinvertebrates and zooplankton from a B. ostreae-endemic area were screened for the presence of parasite DNA, using polymerase chain reaction (PCR). Eight benthic macroinvertebrates and nineteen grouped zooplankton samples gave positive results. Certain species, found positive for the parasite DNA, were then used in laboratory transmission trials, to investigate if they could infect na?ve oysters. Transmission of B. ostreae was effected to two na?ve oysters cohabiting with the brittle star, Ophiothrix fragilis.     

The respiration of common benthic invertebrate species from the shallow littoral zone of Lake Esrom,Denmark

To enable estimation of the total assimilation of benthic populations, we measured the oxygen consumption of macroinvertebrates from the littoral zone of a eutrophic lake. The animals were collected all the year round, and their respiration was measured at field temperatures using a closed-bottle method. Multiple regressions relating the rate of oxygen consumption to temperature and body size were established for 22 taxa, including data derived from the literature for meiofaunal groups.     

Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream

1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%). 3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment. 4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.     

The efficacy of DNA barcoding in the classification,genetic differentiation,and biodiversity assessment of benthic macroinvertebrates

Macroinvertebrates have been recognized as key ecological indicators of aquatic environment and are the most commonly used approaches for water quality assessment. However, species identification of macroinvertebrates (especially of aquatic insects) proves to be very difficult due to the lack of taxonomic expertise in some regions and can become time‐consuming. In this study, we evaluated the feasibility of DNA barcoding for the classification of benthic macroinvertebrates and investigated the genetic differentiation in seven orders (Insecta: Ephemeroptera, Plecoptera, Trichoptera, Diptera, Hemiptera, Coleoptera, and Odonata) from four large transboundary rivers of northwest China and further explored its potential application to biodiversity assessment. A total of 1,144 COI sequences, belonging to 176 species, 112 genera, and 53 families were obtained and analyzed. The barcoding gap analysis showed that COI gene fragment yielded significant intra‐ and interspecific divergences and obvious barcoding gaps. NJ phylogenetic trees showed that all species group into monophyletic species clusters whether from the same population or not, except two species (Polypedilum. laetum and Polypedilum. bullum). The distance‐based (ABGD) and tree‐based (PTP and MPTP) methods were utilized for grouping specimens into Operational Taxonomic Units (OTUs) and delimiting species. The ABGD, PTP, and MPTP analysis were divided into 177 (p = .0599), 197, and 195 OTUs, respectively. The BIN analysis generated 186 different BINs. Overall, our study showed that DNA barcoding offers an effective framework for macroinvertebrate species identification and sheds new light on the biodiversity assessment of local macroinvertebrates. Also, the construction of DNA barcode reference library of benthic macroinvertebrates in Eurasian transboundary rivers provides a solid backup for bioassessment studies of freshwater habitats using modern high‐throughput technologies in the near future.     

Effect of artificial destratification on iron,manganese, and zinc in the water,sediments, and two species of benthic macroinvertebrates in an Oklahoma lake

Ham's Lake was destratified in the summers of 1977 and 1978 by pumping surface water to the bottom. However, an arm was prevented from mixing by a submerged dam of a former farm pond and remained stratified. The concentration of manganese in the water increased to over 5 000 µg 1^–1 in the hypolimnion of the anoxic arm in summer. Soluble manganese averaged 28% of total concentration. Total iron concentrations were relatively high in the water and sorbed iron values were extremely low in the sediments. Soluble iron averaged 12% of total concentration. Zinc values were low in the water and sediments. Chaoborus punctipennis and Chironomus riparius concentrated iron and zinc and discriminated against manganese. Concentration factors were unaffected by mixing.     

The ecological importance of crocodylians: towards evidence‐based justification for their conservation

Large‐bodied predators are well represented among the world's threatened and endangered species. A significant body of literature shows that in terrestrial and marine ecosystems large predators can play important roles in ecosystem structure and functioning. By contrast, the ecological roles and importance of large predators within freshwater ecosystems are poorly understood, constraining the design and implementation of optimal conservation strategies for freshwater ecosystems. Conservationists and environmentalists frequently promulgate ecological roles that crocodylians are assumed to fulfil, but often with limited evidence supporting those claims. Here, we review the available information on the ecological importance of crocodylians, a widely distributed group of predominantly freshwater‐dwelling, large‐bodied predators. We synthesise information regarding the role of crocodylians under five criteria within the context of modern ecological concepts: as indicators of ecological health, as ecosystem engineers, apex predators, keystone species, and as contributors to nutrient and energy translocation across ecosystems. Some crocodylians play a role as indicators of ecosystem health, but this is largely untested across the order Crocodylia. By contrast, the role of crocodylian activities in ecosystem engineering is largely anecdotal, and information supporting their assumed role as apex predators is currently limited to only a few species. Whether crocodylians contribute significantly to nutrient and energy translocation through cross‐ecosystem movements is unknown. We conclude that most claims regarding the importance of crocodylians as apex predators, keystone species, ecosystem engineers, and as contributors to nutrient and energy translocation across ecosystems are mostly unsubstantiated speculation, drawn from anecdotal observations made during research carried out primarily for other purposes. There is a paucity of biological research targeted directly at: understanding population dynamics; trophic interactions within their ecological communities; and quantifying the short‐ and long‐term ecological impacts of crocodylian population declines, extirpations, and recoveries. Conservation practices ideally need evidence‐based planning, decision making and justification. Addressing the knowledge gaps identified here will be important for achieving effective conservation of crocodylians.     

The importance of forest patch networks for the conservation of the Thorn-tailed Rayaditos in central Chile

Conservation of forest birds in fragmented landscapes requires not only determining the critical patch characteristics influencing local population persistence but also identifying patch networks providing connectivity and suitable habitat conditions necessary to ensure regional persistence. In this study, we assessed the importance of patch attributes, patch connectivity, and network components (i.e., groups of interconnected patches) in explaining the occupancy pattern of the Thorn-tailed Rayadito (Aphrastura spinicauda), a forest bird species of central Chile. Using a daily movement threshold distance, we identified a total of 16 network components of sclerophyllous forest within the study area. Among those components, patch area and vegetation structure-composition were important predictors of patch occupancy. However, the inclusion of patch connectivity and component size (i.e., the area of a network component) into the models greatly increases the models’ accuracy and parsimony. Using the best-fitted model, a total of 33 patches were predicted to be occupied by rayaditos within the study area, but such occupied patches were distributed in only six network components. These results suggest that persistence of rayaditos in central Chile requires the maintenance of large single patches and patch networks providing habitat and connectivity.     

The effect of wind exposure and filamentous algae on the distribution of surf zone macroinvertebrates in Lake Esrom,Denmark

Distribution and composition of the epilithic macroinvertebrate fauna was studied on 21 different sites situated in the surf zone of Lake Esrom. A relative degree-of-exposure (windinduced wave activity) was calculated for each station from the specific number of wind days, wind velocity and a measured wind fetch. Macroinvertebrate abundance averaged 20 200 ind. m^–2 stone bottom, and was composed primarily of six taxa (70% of the mean densities). The distribution patterns of the 48 most common taxa were compared to exposure, the amount of filamentous algae and shore slope, by regression, cluster analysis and ordination analysis (PCA and RDA). The abundance of 25 taxa was significantly correlated to the amount of filamentous algae, and a protectional effect of algae growth was suggested for the exposed sites. Seventeen taxa showed significant difference in abundance between sheltered western stations and exposed eastern stations. Stations with a gentle slope were characterised by sand covered stones and a fauna that qualitatively was similar to the fauna at greater depth in the littoral. Redundancy analysis (RDA) showed filamentous algae and slope to be the most important factors controlling the species distribution, whereas the gradient of exposure in Lake Esrom was too short to explain the species tolerance range.     

Use of artificial substrates for standardized sampling of macroinvertebrates in the assessment of water quality by the Belgian Biotic Index

The paper reviews 3 years of experience in Belgium and Portugal with artificial substrates for collecting macroinvertebrates used in water quality assessment by means of the Belgian Biotic Index (B.B.I.).Artificial substrates provide a valid alternative method for sampling the macroinvertebrate fauna and the possibility of standardizing the sampling effort, whereas sampling with a handnet may be more subjective.Research has been focussed on the effect of sampler design and composition as well as conditions of exposure on the number of systematic units and the biotic index obtained.With artificial substrates correct assessments could be performed in different types of watercourses, including lowland brooks and canals as well as fast running upland rivers located in different climates.Guidelines for the development of a simple standard procedure with artificial substrates are proposed.     

Use of the BEAST model for biomonitoring water quality in a neotropical basin

The use of predictive models in Neotropical basins is relatively new, and applying these models in large basins is hindered by the lack of ecological, geographical, and social-environmental knowledge. Despite these difficulties, we used data from the das Velhas River basin to apply the BEAST (Benthic Assessment of SedimenT) methodology to evaluate and classify the level of environmental degradation. Our two main objectives were to modify and implement the BEAST methodology for use in biomonitoring programs of Brazilian basins, and to test the hypothesis that a gradient of environmental degradation determines a gradient in the structure and composition of benthic macroinvertebrate assemblages. We evaluated 37 sites: 8 in the main river, 15 in the main tributaries with different impact levels, and 14 in tributaries with minimally disturbed conditions (MDC). The BEAST model allowed us to classify 16 test sites: two as natural, four as altered, three as highly altered, and seven as degraded. Our results indicated degradation of the das Velhas River basin near its urban areas. The BEAST model indicated that the pollution gradient found among the sites generated a gradient of the macroinvertebrate assemblages, corroborating the hypothesis. Handling editor: S. M. Thomaz