Hydrobiologia最新文献

Along the U.S. east coast, the widespread non-native red alga Gracilaria vermiculophylla provides habitat for an array of macroinvertebrates, including the eastern mudsnail Ilyanassa obsoleta. Though I. obsoleta tolerates a wide temperature range, increases in summer water temperatures may enhance mortality; furthermore, the presence of non-native algae in rising seawater temperatures could exacerbate harmful conditions. We tested how the presence or absence of G. vermiculophylla influenced snail mortality across a range of summer temperatures over a 3-week period. We found that I. obsoleta survived the longest in the lowest temperature (27 °C), followed by the medium (32 °C), and lastly the highest (36 °C) where all snails died within 2 days. Mortality was also higher and faster for snails in the presence versus absence of G. vermiculophylla. We suspected dissolved oxygen became very low at the higher temperatures with G. vermiculophylla; thus we conducted a laboratory-based dissolved oxygen experiment. We found that G. vermiculophylla degraded and oxygen declined faster at the highest temperature treatment, thereby creating anoxic conditions. Altogether, our results demonstrate that G. vermiculophylla could enhance anoxic conditions at high summer temperatures, potentially leading to enhanced faunal mortality.

Recruitment of the catadromous and critically endangered European eel Anguilla anguilla in Europe has declined substantially since the 1980s, with considerable knowledge gaps remaining in many aspects of their life cycle. The aim was to assess eel migration phenology in three regulated rivers in England between 2009 and 2019 through analyses of eel numbers using passes at their tidal limits, with calculation of the annual timings of migration initiation (10% of all eels passed, T₁₀), peak (50%, T₅₀) and conclusion (90%, T₉₀). Across the three rivers, T₁₀ varied between Julian Day (‘Day’) 94 and 173. Years of earlier T₁₀ had significantly earlier T₅₀, where T₅₀ varied between Day 105 and 200. The considerable inter-annual variability in migration timings was associated with environmental variables; earlier T₁₀ and T₅₀ occurred in years of warmer river temperatures (RTs) and cooler sea surface temperatures (SST), and in years where RTs were higher than SSTs. No environmental variables were significant predictors of T₉₀. These results indicate that whilst there is annual variability in the timing of eel migration initiation and peak into freshwaters, this variability is predictable according to differences in environmental conditions. As many of these conditions associated with annual variability in temperature and precipitation then climate change has the potential to shift these migration timings.

Accurate species delimitation and phylogenetic reconstruction are vital to understand biodiversity assessments, conservation management, evolutionary patterns, evolutionary processes, and historical biogeography. The taxonomy and phylogeny of the genus Neolissochilus (Cyprinidae) have a confusing history. We investigated the taxonomy and phylogeny of this group and related lineages using complete mitochondrial genome sequence data from 53 Cyprinidae species and one outgroup species. These analyses show that the monophyly of Neolissochilus and Tor is not supported. N. benasi might represent a new genus, and T. qiaojiensis should be moved into Neolissochilus. We estimated divergence times, evaluated the monophyly of this group, their relationship to other cyprinids, as well as the time course and geography of speciation. The results indicated that the family Cyprinidae likely diverged from other taxa during the Eocene (ca. 54.78 Mya), and species of various genera began to undergo massive diversification events during the Cenozoic Tertiary. The differentiation and diffusion of the family Cyprinidae might be attributed to the Qinghai–Tibet Plateau uplift events, one of the geological events marking the Cenozoic Tertiary period, which cut off genetic exchange between populations through geographic isolation, thus facilitating genetic divergence between populations and eventually leading to the formation of new species. In addition, the results of this study still need further improvement. The limitations are mainly due to the small sample size and the use of only mitochondrial data; therefore, it still needs to be further verified by combining nuclear genome data.

We present a 57-year time series and relationship with environmental parameters of a zooplankton species Chydorus sphaericus, a common small-sized cladoceran species in eutrophic lakes, in a large, shallow and eutrophic Lake Võrtsjärv (Estonia). We show that over the course of more than five decades, the abundance, mean weight and the proportions of C. sphaericus among metazooplankton biomass in this lake have markedly changed. Planktivorous fish (bleak Alburnus alburnus in particular) and total phosphorus were the most influential variables explaining the interannual changes of C. sphaericus individual weight. Abundance and the C. sphaericus proportion among metazooplankton biomass were dependent of a complex set of antagonistic interactions between water temperature, cyanobacteria biomass and pH. Cyanobacterial biomass stood out as the most influential factor for C. sphaericus at the monthly scale. Chydorus sphaericus metrics were negatively correlated with cyanobacteria, positively when cyanobacteria biomass was paired with pH or water temperature, and negatively again when all three variables were present at the same time. Our results confirm that C. sphaericus occupies an important position in a eutrophic lake food web and has been able to thrive in the recent decades through adaptative interactions with its environment.

Invasive alien anurans are introduced worldwide in freshwater ecosystems where they can have a strong impact on native organisms such as amphibians. The risk for natives is dependent on the degree of niche overlap and co-occurrence in pond-breeding sites. In the present study, we focused on alien marsh frogs (Pelophylax ridibundus) that are invading nationwide areas in Western Europe and which prey on both caudates and anurans. We assessed aquatic habitat preferences, pond use and environmental niche overlap between invasive populations of marsh frogs and five species of native amphibian prey of the Larzac plateau (southern France). Due to their large environmental niche, marsh frogs have become the most ubiquitous amphibians in the area. Occupancy models revealed that they had aquatic habitat preferences (e.g., water depth and aquatic vegetation) similar to most species of native amphibians. This resulted in a large overlap between the environmental niche of the invader and its potential prey. The frequent coexistence in ponds therefore exposed native species to predation risk and other potential disturbances caused by marsh frogs. Altogether, these results highlight on the risks posed by such opportunist invaders for native amphibians that occur in their wide invasion range.

Bacterial community composition (BCC) can be modulated by different indirect and direct factors. The Strobel Lake Plateau (Patagonia, Argentina) holds natural fishless lakes. Fish introduction in some of these lakes has affected the structure of their zooplankton, phytoplankton and autotrophic picoplankton communities, whereas its effects on bacterioplankton are unknown. Hence, we analyzed BCC to assess the potential effect of fish introduction on this community in lakes of this region. We sampled fishless and fish-stocked lakes during three summer campaigns and analyzed the BCC. Our results revealed a contrasting arrangement in the main limnological variables and significant differences in the BCC between fishless and stocked lakes. In fish-stocked lakes, Alphaproteobacteria class had a higher proportion and SAR11_cladeIII was the most abundant amplicon sequence variant (ASV); these lakes also showed a marginally higher mean richness but less exclusive ASVs. Environmental and biotic factors contributed to explain BCC variations. The lower percentage of exclusive ASVs and the closer BCC ordination in a non-metric multidimensional scaling suggest a homogenizing effect in fish-stocked lakes. This study contributes to understand the consequences of fish introduction on the plankton communities in lakes of this invaluable region for biodiversity conservation.

The ecological impact of dreissenid mussel (e.g., quagga and zebra) populations and their empty shells on native fauna in large rivers and lakes has been extensively studied. However, there is limited information on their effects in small wadable streams. Although established mussel populations in these systems are uncommon, their shells are found in high densities in benthic environments and may adversely impact stream communities. Shell densities were quantified using quadrats in two wadable streams to assess impacts on native benthic macroinvertebrates and fish. Eight reaches of each river were sampled, four with dreissenids and four without, totaling 16 locations. Macroinvertebrate and fish communities were characterized using diversity and environmental tolerance indices. Shell densities were significantly higher in dreissenid-invaded sites compared to sites with only native bivalves in both rivers. Dense shell beds had degraded biological conditions with fewer sensitive macroinvertebrates, but bed density did not affect overall macroinvertebrate or fish diversity. These findings differ from lake and large river studies, which found a greater impact of dreissenid shell deposition on macroinvertebrate and fish diversity than we observed in small wadable streams. Thus, a different approach to management and restoration may be necessary to maintain a natural community composition in wadable streams.

Studying the routes of invasion of the threespine stickleback is important both because it serves as a model species in evolutionary research and because it may play a substantial role in ecosystems. The goal of this study was to determine the recent pathways of threespine stickleback invasion into the Black and Caspian Sea basins. The partial COI and cyt b mitochondrial gene sequences and the mtDNA region between them (a total of 9926 bp) have been analyzed in a priori separate phylogenetic lineages, Black Sea and American ones. The results indicate that similar sequences of the COI gene may result from parallel evolution in different lineages. The basins of the Volga and Dnieper, the largest rivers of the Ponto-Caspian basin, are currently inhabited only by carriers of the European lineage haplotypes; this agrees with the data on the disappearance of aboriginal stickleback populations from these river basins in the first half of the twentieth century. Only Black Sea lineage haplotypes have been found in stickleback from the recently formed populations of the Caspian Sea coast. The results show that alien conspecifics may substantially affect the genetic structure of threespine stickleback populations in the native species range.

While there is a global trend in kelp forests decline, sub-Antarctic Beagle Channel kelp ecosystems are among the most stable and extensive in the world, acting as a climatic refuge, indicating its high conservation value. Nevertheless, these coastal ecosystems are increasingly exposed to anthropogenic drivers that can affect kelp strategies and promote their replacement by turf. This study evaluated the urban impact of a coastal city in the Beagle Channel (Ushuaia, 54° S 68° W) on giant kelp (Macrocystis pyrifera) population dynamics. Seasonal samplings were conducted between 2020 and 2023 in two contrasting sites: an urban site directly exposed to Ushuaia pressures and a non-urban site. Our results indicate a reduction in both kelp adult density and kelp recruitment at the urban site. Here, high sediment inputs were the main factor affecting kelp recruitment, but higher density of potential grazers, and changes in the understory macroalgae assemblage were further observed. Morpho-functional composition and sediment trapped within the macroalgae suggest the prevalence of turf-forming algae dominating the urban site’s understory assemblage. If neglected, the decline in kelp recruitment rates and the replacement of the forest by turf could eventually lead to a local loss of this urban-influenced sub-Antarctic kelp forest.

Sulfur deposition and eutrophication accelerated the production of hydrogen sulfide (H₂S) in aquatic ecosystems. However, the understanding of how H₂S affects the invasive potential of exotic aquatic plants is inadequate. Here, the exotic Elodea nuttallii (Planch.) H. St. John was exposed to five H₂S concentrations (0–1.0 mM) and compared with the native Hydrilla verticillata (L. f.) Royle. Both plants grew well below 0.5 mM H₂S, with E. nuttallii showing better performance. E. nuttallii and H. verticillata maintained their height growth rates by reducing the ramets number and the relative growth rate, respectively. This trade-off in morphological traits was for adequate light and oxygen. Furthermore, E. nuttallii exhibited higher chlorophyll and carotenoids content but lower chlorophyll a/b, indicating better utilization of low light in the water body. High concentrations of H₂S induced oxidative stress in E. nuttallii, leading to higher superoxide dismutase (SOD), soluble sugars, and starch. The utilization strategies of C, N, P and S by E. nuttallii remained unchanged with varying H₂S concentrations, demonstrating higher stoichiometric stability. In conclusion, E. nuttallii showed greater resistance to H₂S compared to H. verticillata. The invasive potential of E. nuttallii in H₂S-enriched aquatic environments was depending on the H₂S concentration of native community.