Explore the vast range of titles available.

The great lakes of the world represent a global heritage of surface freshwater and aquatic biodiversity. Species lists for 14 of the world's largest lakes reveal that 15% of the global diversity (the total number of species) of freshwater fishes, 9% of noninsect freshwater invertebrate diversity, and 2% of aquatic insect diversity live in this handful of lakes. The vast majority (more than 93%) of species inhabit the shallow, nearshore littoral zone, and 72% are completely restricted to the littoral zone, even though littoral habitats are a small fraction of total lake areas. Most fish species exploit benthic resources, which increases food web complexity. Moreover, littoral zones are both more negatively affected by human activity and less intensively studied than offshore waters. Conservation of the remarkable biodiversity and biotic integrity of large lakes will require better integration of littoral zones into our understanding of lake ecosystem functioning and focused efforts to alleviate human impacts along the shoreline.

Lake phytoplankton studies outnumber studies on lake periphyton by an order of magnitude, and most periphyton research has been done in streams. Most benthic algal taxa found in lakes also can be found in lotic systems, but assemblages and taxa differ in a number of ways. The ecological characteristics of some lake benthic algae reflect habitat coupling. Littoral zones (benthic areas above the light compensation depth) are areas of high productivity and biodiversity. The proportion of benthic and planktonic primary production (autotrophic structure) is a key ecosystem property. The distribution of lake benthic algae is markedly influenced by the depth gradient and substratum, and assemblages change with depth from epilithic and epiphytic rheobionts to epipsammic and epipelic limnobionts. At shallow depths, periphyton must cope with the effects of high radiation, water-level fluctuations, wave action (e.g., desiccation, ultraviolet radiation exposure, shear stress), and seasonal shifts in temperature. This situation selects for widely distributed rheophilic species. In contrast, the deeper littoral zone is stable and hosts a distinct subset of lentic periphyton. However, species experience low light intensity, which becomes increasingly severe with increasing depth, and are often threatened by eutrophication-driven increased shading by phytoplankton. Besides change across depths and substrata, adaptations to disturbance levels, competition, microdistribution of phenological stages, and physiomorphological regulation generate multiple and complex spatial patterns at different scales. Lake shores are the focus of human activities with significant consequences for periphyton. In this review, we introduce a series of 15 papers on the topic and suggest directions for future research. Overall, this special series illustrates that, despite the many important ecosystem services provided by lake benthic algae, the topic is understudied.

The lake littoral zone is periodically exposed to water due to water level fluctuations, driving the succession and distribution of littoral vegetation covers, which complexly affect nutrient biogeochemical transformation. However, the combined effects of water level fluctuations and other environmental factors on microbial characteristics and functions at the regional scale remain unclear. In this study, typical vegetation cover types along various water levels were chosen to investigate the effects of water level and vegetation cover on the microbial community and functional genes in the Lake Erhai littoral zone. The results showed that water level fluctuations influenced oxygen and nitrogen compound contents due to oxic–anoxic alternations and intensive material exchange. Meanwhile, vegetation cover affected the organic matter and total nitrogen content through plant residues and root exudation supplying exogenous carbon and nitrogen. Along the hydrological gradient, the high microbial diversity and abundant microbes related to nitrogen cycling were observed in interface sediments. It was attributed to the alternating aerobic–anaerobic environments, which filtered adaptable dominant phyla and genera. The abundances of amoA AOA, nirS, and amx were higher than those of the other genes and were strongly related to flooding days and water content. In conclusion, water level fluctuations and vegetation type jointly affect microbial community structure and nitrogen-related functional genes.

Lake littoral environments are heterogeneous, and different organisms typically show specific responses to this environmental variation. We examined local environmental and spatial factors affecting lake littoral biodiversity and the structuring of assemblages of phytoplankton, zooplankton and macroinvertebrates within and among three basins of a large lake system. We explored congruence of species composition and species richness among the studied organism groups to evaluate their general indicator potential to represent spatial variation in other groups. We expected that effects of water chemistry on plankton assemblages were stronger than effects of habitat characteristics. In contrast, we anticipated stronger effects of habitat on macroinvertebrates due to their mainly benthic mode of life. We also expected that within-basin spatial effects would be strongest on macroinvertebrates and weakest on phytoplankton. We predicted weak congruence in assemblage composition and species richness among the organism groups. Phytoplankton assemblages were mainly structured by the shared effects of water chemistry and large-scale spatial factors. In contrast to our expectations, habitat effects were stronger than water chemistry effects on zooplankton assemblages. However, as expected, macroinvertebrate species composition and richness were mainly affected by habitat conditions. Among-group congruence was weak for assemblage composition and insignificant for richness. Albeit weak, congruence was strongest between phytoplankton and zooplankton assemblages, as we expected. In summary, our analyses do not support the idea of using a single organism group as a wholesale biodiversity indicator.

Development of effective methods for assessing the ecological status of lakes based on littoral benthic fauna has been hampered by the lack of quantitative data on the relative impacts of key pressures on the benthic community. We used variance partitioning at 126 sites belonging to 14 natural Mediterranean lakes to analyze the pure and shared effects of eutrophication, morphological alterations, microhabitat type, lake morphometry and geographic position on the littoral macroinvertebrate community. The spatial arrangement of the sampling sites was responsible for 9.1% of the total variance in littoral benthic community composition, lake morphometry accounted for 4.3% of variation, and microhabitat type accounted for 3.9%. Communities appeared to be affected primarily by morphological alterations to lake shorelines, and their impact was 2.5 times as important as that of eutrophication. The structure of littoral benthic communities was governed by processes acting at several spatial scales from region to lake scale. Thus, several pressures and the various spatial scales at which these act should be taken into account when implementing methods of assessing lake ecological condition based on littoral benthic invertebrates. Region-specific methods for subalpine and volcanic lakes might enhance the validity of assessment of results of morphological alterations and improve management of those water resources.

The high levels of species diversity observed within many biological communities are captivating, yet the mechanisms that may maintain such diversity remain elusive. Many of the phenotypic differences observed among species cause interspecific trade‐offs that ultimately act to maintain diversity through niche‐based coexistence. In contrast, neutral community theory argues that phenotypic differences among species do not contribute to maintaining species diversity because species are ecologically equivalent. Here we provide experimental and observational field evidence that two phylogenetically very distant Enallagma species appear to be ecologically equivalent to one another. Experimental abundance manipulations showed that each species gains no demographic advantage at low relative abundance, whereas manipulations of total Enallagma abundance resulted in large increases in per capita mortality and large decreases in growth for both species. Moreover, demographic rates and relative abundances of multiple Enallagma species were uncorrelated with major environmental gradients in an observational study of 20 natural lakes. These are the expected patterns if species are ecologically equivalent. However, these results do not imply that all damselflies in these lakes are ecologically identical. Previous experimental results have demonstrated the operation of strong coexistence mechanisms maintaining Enallagma and its sister‐genus Ischnura in these littoral food webs. Combined with a simple theoretical model we present, these results taken together show how both neutral and niche dynamics can jointly structure communities.

Witkowski, A.; Li, C. L.; Zg[lstrok]obicka, I.; Yu, S. X.; Ashworth, M.; Dąbek, P.; Qin, S.; Tang, C.; Krzywda, M.; Ruppel, M.; Theriot, E. C.; Jansen, R. K.; Car, A.; Płociński, T.; Wang, Y. C.; Sabir, J. S. M.; Daniszewska-Kowalczyk, G.; Kierzek, A., and Hajrah, N. H., 2016. Multigene assessment of biodiversity of diatom (Bacillariophyceae) assemblages from the littoral zone of the Bohai and Yellow Seas in Yantai region of Northeast China with some remarks on ubiquitous taxa. Diatoms are important contributors to the benthic microeukaryote flora. This manuscript lays the foundation for future metagenomic and environmental sequencing projects off coastal China by curating diatom DNA sequences from the Yantai region of the Bohai and Yellow Seas (Northeast China). These studies are based on cultures established from samples collected in different seasons from marine littoral and supralittoral zones in 2013 and 2014. Thirty-six diatom strains were cultured successfully and identification of these clones was determined by light and scanning electron microscopy(LM and SEM) and DNA sequencing of the nuclear-encoded small subunit ribosomal RNA (SSU)and chloroplast-encoded rbcL and psbC genes. The strains primarily represent raphid pennate genera, such as Amphora, Amphora (Oxyamphora), Caloneis, Diploneis, Halamphora, Navicula, Nitzschia, Parlibellus, Pleurosigma, Surirella and Tryblionella. When the DNA markers from these strains were analysed in a multi-gene phylogeny, we found that some clones-particularly within the genera Amphora, Navicula and Nitzschia—show greater than expected genetic diversity despite their very similar morphology and morphometrics. We also compared the molecular and morphological identities of several seemingly ubiquitous marine littoral taxa in the genera Amphora and Nitzschia from the Indian Ocean and Atlantic Ocean, the Red Sea and Adriatic Sea to their Yellow Sea counterparts.

A new approach for visual fish survey in reservoirs using underwater drones (remotely operated vehicle- ROV) is presented. The ROV was applied to identify abiotic gradients and to compare fish assemblages on the steep slopes in a tropical reservoir. The tested hypothesis is that fish are concentrated in the littoral zone due to the better physicochemical and habitat conditions, compared to deep and hypoxic layers. Twelve species were recorded (seven native, five exotic), with all species occurring in the littoral zone, seven species in the transition, and four in the profundal zone. A greater fish abundance and richness was found in the littoral zone corroborating the main hypothesis. The littoral zone was dominated by exotic cichlids (Cichla spp., Coptodon rendalli), while native catfish (Loricariichthys castaneus, Pimelodella lateristriga) occupied deeper areas. The fish distribution seems to be driven by local factors, such as oxygen availability and habitat structure. The preference for the littoral zone by alien cichlids may have led to the extirpation/decrease of native characids and induced catfishes to occupy deep habitats. Underwater drones can be a valuable tool for the simultaneous collection of abiotic/biotic data, especially in deep reservoirs with complex habitats, resulting in advances in the environmental monitoring.

AIMS: Plants have been suggested to have significant effects on methane (CH₄) and nitrous oxide (N₂O) fluxes from littoral wetlands, but it remains unclear in subtropical lakes. METHODS: We conducted in situ measurement of CH₄ and N₂O fluxes for two years. To distinguish between the effects of shoots and roots, three treatments (i.e., intact plants as control, shoot clipping, and root exclusion) were used. Effects of plant biomass, temperature, and soil moisture on CH₄ and N₂O fluxes were analyzed. RESULTS: The mean ecosystem CH₄ emission rate was 36 μg CH₄ m⁻² h⁻¹ for drying periods, but 8219 μg CH₄ m⁻² h⁻¹ for drying-wetting transition periods. CH₄ fluxes were positively correlated with below-ground and total biomass, but not with above-ground biomass. Clipping did not significantly alter CH₄ flux rate, but root exclusion decreased the CH₄ flux by 116 % as compared to the control. N₂O emissions were similar for both the drying and drying-wetting transition periods, with a mean rate of 20 μg N₂O m⁻² h⁻¹. Both clipping and root exclusion significantly increased N₂O fluxes as compared to the control. CONCLUSIONS: There was no significant correlation between CH₄ and N₂O fluxes. Roots dominated plant-mediated enhancement in CH₄ fluxes, but played almost an equal role as shoots in plant-regulated suppression on N₂O fluxes in this Carex meadow during drawdown periods.

The intertidal zone is unique in terms of its ecological conditions and faunal assemblages. Molluscs form a key link in the food chain and have a high socioeconomic value for coastal fisheries. Intertidal habitats of Karnataka are modified by anthropogenic disturbances which threaten the animals living there including molluscs. The present study is designed to know the diversity of molluscs of Karnataka coast, India and to understand the factors influencing variations in molluscan diversity. Thirteen intertidal habitats of coastal Karnataka were selected for the study of which six sites were visited on monthly basis from February 2017 to January 2018. Molluscan shells were collected from these sites using quadrates of 0.25m² from fixed intervals. The other sites were visited once during the study and molluscs were collected using quadrates and by handpicking. Molluscs were brought to the laboratory, preserved in 70% alcohol, and identified using the standard identification keys. Abiotic parameters such as air temperature, water temperature, wave frequency were noted in the field. Environmental variable such as precipitation was studied. Physico-chemical parameters of water (salinity, electrical conductivity, pH of water) were analysed using standard methods. A total of 36 species of molluscs were recorded from the intertidal habitats of coastal Karnataka. It includes 21 species of gastropods and 15 species of bivalves. Bullia melanoides, Saccostrea cucullata and Echinolittorina leucostica were found throughout the study. Abranda myeformis, Mactra luzonica, Sunetta sp, Turricula tornata fulminata were the rare shells found on the beaches of coastal Karnataka. The abundance of molluscs was observed post-monsoon in all the sites. Species richness of molluscs was more in post-monsoon in all the intertidal areas except beaches of Kaup and Kota-Padukere. Shannon-Weiner index and Simpsons index were more in post-monsoon in the beaches of Someshwar, Panambur, Sasihithlu, and Gangolli whereas diversity indices were highest in intertidal areas of Kaup and Kota-Padukere in premonsoon. Kruskal–Wallis test showed the significant differences between abundance (P=0.001) and species richness (P=0.002) of molluscs with the seasons. During the study salinity, electrical conductivity, and pH of water ranged between 21.7–33.66ppt, 41.42–57.90 mS/m, and 7.36–8.47 respectively. Average values of air temperature, water temperature, and wave frequency varied between 26.50⁰C–30.25⁰C, 27.75⁰C–30.25⁰C, and 6–9 between the seasons. However, no significant correlation was found between these parameters and species diversity. The number of molluscs was more when the wave frequency was between 6–7. A significant negative correlation of wave frequency with molluscan abundance was observed which shows that reduced wave-action increases the molluscan diversity. A significant correlation between the electrical conductivity of water with species richness indicates that this is the important physico-chemical parameter responsible for the distribution of molluscan species on the coast. Wave frequency and electrical conductivity are the parameters are responsible for molluscan diversity in the intertidal zones. Thus the littoral zones of the Karnataka coast provide suitable habitats for molluscs.