International Review of Hydrobiology最新文献

The explosive global spread of Sinadonta woodiana, a large-bodied unionid mussel of East Asian origin, potentially affects the functioning of freshwater habitats and threatens native mussels. Molecular data indicate that its invasion in Europe started with a single colonization event, followed by in situ adaptation. This study traces one of the possible routes of such adaptation. It documents a population of S. woodiana with a known history of a two-stage introduction: first, from a heated water source to a production fish pond in northern Poland, and subsequently from that pond to the study site. As the latest local transfer occurred more than 15 years before the study, the abundance of young S. woodiana in various age classes provides proof of ongoing in situ reproduction and resolves the question of the ability of S. woodiana to permanently colonize thermally unpolluted water bodies in areas with prolonged and cold winters. The study also shows that translocations of glochidia-infested fish and/or adult mussels between water bodies in such areas result in the establishment of new self-recruiting populations. Together, these findings show that further expansion of S. woodiana into colder regions and establishment of new populations in already invaded areas are to be expected. The relative abundance of S. woodiana and the native unionids: Anodonta anatina and A. cygnea was 40%, 18%, and 42%, respectively. S. woodiana contributed to 65% of the total mussel biomass. Individuals in the first three size classes, corresponding to the 2- to 4 year age classes, composed 50% of S. woodiana, 37% of A. anatina, and 26% of A. cygnea. The high proportion of young individuals in S. woodiana indicates population trajectories toward a gradually increasing dominance of this species and possibly reflects its negative impacts via interactions with host fish and competition for resources.

The specific biota of isolated habitats is determined by habitat properties (e.g., age, size, environmental conditions), their spatial isolation and the characteristics of the surrounding landscape matrix. In this study, we examine the contrast in Trichoptera assemblages between isolated island-like Western Carpathian spring fens and nearby headwater streams. We evaluate the potential of streams and their mesohabitats to serve as stepping-stone habitats for fen species, and identify factors determining the dissimilarity of the Trichoptera between the fens and streams. Of 24 studied fen-stream pairs, 80 Trichoptera taxa, mainly species, were identified. Out of these, 17 and 34 species were exclusive for fens and streams, respectively. Although the remaining 29 species were in common, a clear preference of each species to one of these two habitat types was observed, which resulted in highly contrasting assemblages in terms of species composition. A clear difference was found also at the level of species traits, as cold-adapted crenobiont and crenophilous species of small body size, limited dispersal ability, and long larval development prevailed at the fens. The fen-stream dissimilarity of Trichoptera was not associated either with fen habitat properties (age, size and environmental conditions) or with the distance between the habitats. Only stream characteristics reducing the fen-stream environmental contrast were important. Abundance of fen species at streams was negatively related with substrate roughness and stream size, suggesting that small streams with a fine substrate can serve preferably as stepping-stone habitats for the fen species. Our results show the high conservation value of spring-fen Trichoptera assemblages due to the prevalence of habitat specialists as well as cold stenothermic and pollution-sensitive species. It also seems that the isolation of fens surrounded only by unsuitable streams is additionally increased by a lack of stepping-stone habitats in the surrounding matrix.

Bosmina longirostris is a polymorphic cladoceran, widely distributed throughout the world in temperate and tropical climates, where it colonises all kinds of freshwater bodies regardless of their trophy, acidification, or salinity. In this paper, we test the hypothesis that the ability of B. longirostris to colonise new freshwater bodies results from their maintenance of morphotypes with different life histories. To test the above hypothesis, the life histories of four morphotypes of B. longirostris were analysed through daily observations of individuals cultured separately under uniform optimal conditions. We demonstrated that these morphotypes differed in somatic growth, reproductive effort, lifespan, and fitness, and differences in life histories among morphotypes resulted from the trade-offs between these parameters. Next, we examined the role of distinct morphotypes (each with specific life-history) in populations subjected to stress: we maintained two populations of B. longirostris under biotic stress (the presence of invertebrate predators) or abiotic stress (elevated salinity). At the end of the experiment these populations differed from one another in the relative density of morphotypes in comparison with the population cultured in the optimal environment. In populations that suffered from predatory pressure we found an increase in the relative density of morphotypes that grew considerably quicker, had a shorter lifespan, reproduced infrequently but delivered many offspring at each reproductive event. In populations that suffered from elevated salinity, we observed an increase in morphotypes that exhibited low reproductive effort but had the highest survival. Simultaneously, with phenotypic regrouping of populations, morphotypes adapted to novel conditions by altering the expression of life-history traits. The observed switches in the phenotypic structure of B. longirostris suggest that the persistence of morphotypes with different life histories is beneficial to populations colonising varying environments and their relative abundances in a population are conditioned by the diverseness of local stressors.

Most tropical rivers, especially in the Asian region, are severely impacted by various human perturbations and the diverse habitats in streams support rich invertebrate and vertebrate communities. It is hypothesized that the fish assemblages and their dietary structure in two tropical streams differ because they flow through different terrains and are exposed to different climatic conditions. In the wet-zone stream, which is geomorphologically more complex, fish faunal diversity showed a significant variation and presence of endemic fish species. In the diets of fish, the taxonomic composition was different along the longitudinal gradients, but dietary taxa richness in the two streams was virtually similar having 32 dietary taxa in the wet-zone stream and 36 taxa in the dry-zone stream. In the wet-zone stream, we observed a lower proportion of specialist feeding species than those in the dry-zone stream. Trophic indices of individual species in fish assemblages ranging from herbivory to carnivory also indicate structuring of fish communities along the longitudinal gradients of the two streams based on the dietary structure. The main differences between the fish assemblages in the wet zone compared with the dry zone were the higher number of endemic species and the lower percentage of specialist feeders with higher trophic indices. The outcome of this study, hopefully, contributes to planning future biodiversity conservation management schemes under various river-basin development strategies.

The abundance of the European eel has seriously declined during recent decades. Hydropower production is one of the main threats, and solutions at power stations are needed to reduce the mortality of the downstream migrating silver eel. We examined the mortality, migration routes, and behavior of silver eel at a power station in Germany, after the power station was rebuilt to reduce the mortality of downstream migrating fish. Of 270 eels implanted with radio transmitters and released upstream of the power station, 222 eels passed the power station, primarily in October and November, although some descended during winter and spring. Most eels followed the main flow and passed over the spillway gate (59% and 49% in the 2 study years) or followed the route toward the bar racks in front of the turbines (24% and 27%), where they were guided to a route outside the turbines via the flushing channel. Some eels used the vertical slot fish passage (12% and 8%), whereas few used a nature-like fishway, canoe pass, or custom-made bypasses for eel. The eels showed large individual variation in migration timing, migration speeds, and choice of bypass. No eels were killed in the turbines, as none passed through them, likely due to the narrow bar spacing of the racks (10 mm). The results demonstrated that the mortality of eel passing power stations can be low (0–4% and 0–8% in the 2 study years) when the turbine intake is covered by racks hindering eels from entering turbines and safe bypass routes are available. Mortality estimates are given as ranges because the fate of 4% and 8% of the individuals could not be determined. Potential mortality could have been related to injuries in the bypass routes or increased predation risk, but there were no indications of injuries caused by installations in any of the bypass routes.

Dissolved organic nitrogen (DON) plays important biogeochemical and ecological roles in aquatic systems. However, little is known about its importance in small tropical lakes and reservoirs. We hypothesized that (a) DON is higher in these systems than dissolved inorganic N (DIN), and that (b) relative contributions of DON and DIN to the total dissolved nitrogen (TDN) pool decrease and increase, respectively, with trophic status. To test these hypotheses, we measured DON and DIN in six lakes and two reservoirs at the Atlantic forest-Cerrado savanna transition in Southeast Brazil, in the rainy and the dry season. With one exception in each season, all oligo- and mesotrophic systems had DON:DIN ratios >1. DON:DIN ratios were negatively correlated with total phosphorus (TP). This pattern was due to high DIN, mainly ammonium, in eutrophic and hypertrophic systems. DON:DIN ratios <1 occurred at TP higher than 103 and 104 µg L⁻¹ in the rainy and dry season, respectively. We found a general dominance of DON in near-natural lentic systems at the Atlantic forest-Cerrado savanna transition, which was more pronounced than that reported for other regions. Human alterations to the TDN pool may affect biological communities and ecosystem functioning of these systems.

Most faunistic studies of large-scale patterns concern terrestrial vertebrates, whereas smaller organisms, and in particular, freshwater invertebrates like rotifers receive less attention. As a result, the “rotiferologists” effect”, that is sampling intensity, is among the most influential factors observed, globally or locally, on species richness.

Because there are many more small, isolated patches of habitats available to the specialist species, greater specialization has occurred in those forms than in ubiquitous species. This rule also applies to rotifers. Results show that: (a) the total number of rotifer species observed in a lake depends on both the number of samples collected and the type and number of lake habitats involved; and (b) the originality (variability) of rotifer fauna in particular lakes is more pronounced with the more species found in a lake.

The important purpose of faunistic studies is the registration of indigenous species. The inflow of alien species is currently one of the greatest threats to the preservation of natural fauna. However, if we do not recognize the composition of natural communities, we will not be able to recognize the invaders. The second most important goal is to enable tracking of long-term changes in species diversity of rotifer fauna. Rotifers seem to be sensitive enough to climate change and pollution of the aquatic environment. Thus, for the reasons described above, faunistics will be still necessary.

The feeding ecology of the two gobiid species monkey goby Neogobius fluviatilis and western tubenose goby Proterorhinus semilunaris was studied in four natural lakes of the Marmara Region (NW Turkey), with special emphasis on seasonal and ontogenetic shifts in diet. Both species had similar food composition consisting of zooplankton and detritus. However, diet composition of both species significantly varied amongst lakes, and particularly so for P. semilunaris with seasonal and ontogenetic differences. Diet composition and seasonal/ontogenetic differences were overall similar to other populations of these gobiid species from both their native and nonnative ranges. The present findings suggest high plasticity in the diet of these two gobies, which can opportunistically utilize available food resources.

We studied two populations of Boeckella gracilipes and two populations of Boeckella gibbosa that inhabit mountain lakes from North-Patagonian Andes with different optical properties. We combined field and laboratory experiments to determine the effects of ultraviolet radiation (UVR) on clearance rate among these taxa that had different UVR defences. The copepod populations differed in photoprotective compounds (carotenoids and mycosporine-like amino acids [MAAs]) and antioxidant enzymes (glutathione S-transferase [GST]). These variations were related to elevation, dissolved organic carbon content and the optical features of the inhabited lakes. Laboratory experiments showed a decrease in the clearance rate (CR) in all populations exposed to UVR. Consistently, the long-term field experiment showed a negative impact of UVR on CR. We conclude that UVR exposure affects feeding, however, the magnitude of this negative effect depends on the exposure intensity and the photoprotective mechanisms used by zooplankton.