Hydrobiologia最新文献

Current methods for assessing the environmental impacts of marine non-indigenous species (NIS) are limited by insufficient data, an over-reliance on expert judgement and too coarse a spatial resolution, which hampers accurate local management. However, advances in data-driven analyses offer significant potential for developing more comprehensive and accurate frameworks for assessing the impacts of NIS in marine ecosystems. This study fills this major gap in NIS management by proposing a comprehensive and practical framework that integrates systematic reviews, meta-analyses, species distribution modelling, and expert judgement to assess NIS impacts across varying levels of information availability. The framework also recommends complementary, under-utilised data sources, and tools to reduce significantly existing information constraints. The framework presented in this study not only advances scientific understanding of NIS impacts by providing a scalable and adaptable framework for assessing NIS impacts in different ecological contexts, but also provides practical tools for environmental managers implementing legislation on NIS. We recognise that although our data-driven approach to NIS management is best handled by specialists, maximising its potential requires making the information accessible and user-friendly to a broader audience. This can be achieved through digital tools that simplify and facilitate the understanding of these assessments for environmental managers.

Alien species impact native amphibians through various direct effects, including predation, and pose a significant threat to naïve prey populations. In this study, we exposed tadpoles of three brown frog species (Rana dalmatina, Rana latastei, and Rana temporaria) to the olfactory cues of two alien predators, the pond slider (Trachemys scripta) and red swamp crayfish (Procambarus clarkii), and compared their responses to those induced by the aquatic larvae of a widespread native predator, the Southern hawker (Aeshna cyanea). We recorded two tadpole defensive behaviors, the proportion of time they were active and the number of freezing events. Both agile frog species, R. dalmatina and R. latastei, showed moderate responses to red swamp crayfish kairomones and strong responses to both odonate larvae and pond sliders. In contrast, the common frog (R. temporaria) displayed a less intense response to crayfish with respect to odonate larvae, and a negligible response to pond sliders. Long-lasting coexistence with either European pond turtles or pond sliders may explain the strength of agile frogs’ response toward the alien species; while, the historical range of the white-clawed crayfish (Austropotamobius pallipes) overlapped that of the common frog, enhancing the co-option of alien crayfish cues by this anuran species.

Nitrogen stable isotope ratios (δ¹⁵N) are widely used to quantify trophic position in aquatic ecosystems. Comparing trophic position across space requires identifying baselines to account for variation in δ¹⁵N values of basal energy resources, but few standardized methods exist for identifying suitable baselines. We evaluated a standardized method for identifying optimal isotopic baselines in streams spanning the Rocky Mountains–Great Plains ecotone. We assessed candidate taxonomic groups and feeding groups following four criteria: (1) Organisms should be easy to collect and widely distributed, (2) Within-site δ¹⁵N variation should be low (representative of uniform feeding behavior), (3) δ¹⁵N values should be correlated with geographic variability in δ¹⁵N values, and (4) Trophic position of consumers calculated using the baseline should be independent of geographic δ¹⁵N variability when there is no change in diet. Simuliidae (obligate, sestonic filter feeders) met all four criteria for four fishes and produced trophic position estimates consistent with dietary changes for brown trout along a longitudinal stream gradient. The four-criteria screening method is suitable for temperate streams in North America and supports the recommendation to use Simuliidae or potentially grouped filter feeders as baseline organisms for stable isotope studies quantifying trophic position in higher-order consumers.

In order to describe large-scale spatial structure of sockeye salmon on the Asian part of the range, the variability of 45 SNP loci was analyzed in 22 samples from the Northwest coast of the Pacific Ocean. Three large regional population complexes were identified: Southwest Kamchatka, Kamchatka River basin, and the Northeast (comprising stocks from Koryak Highlands). Populations within the identified complexes are connected by gene migration and have a common origin, close geographic proximity, comparable climatic, landscape, and environmental conditions in the freshwater and early marine periods of sockeye salmon life. Populations confined to watersheds of the North coast of the Sea of Okhotsk (Palana and Okhota rivers), along with island populations, displayed distinctions from the isolated population complexes. It is hypothesized that the marked divergence observed in island populations is primarily caused by genetic drift occurring during long periods of isolation. The pronounced divergence of Palana River population may be the result of both genetic drift and natural selection, driven by the challenging smoltification and specific conditions of freshwater period in this watershed. At the same time in the Okhota River population, demographic factors such as genetic drift and bottlenecks played a key role.

Red macroalgae in the genus Porphyra are widely collected for human consumption and increasingly harvested along the North Atlantic coasts but their ability to withstand repeated harvesting and maintain high cover and abundance on natural shorelines remains poorly explored, raising sustainability concerns. Therefore, we investigated the effect of frequent hand-harvesting on Porphyra dioica in a population in South Wales, UK, where it is commercially harvested. Twelve control and twelve treatment quadrats were installed in spring and six control and treatment plots in autumn. Monthly hand-harvesting of P. dioica individuals larger than 5 cm was performed in the treatment plots, while the control plots remained undisturbed. We monitored P. dioica percentage cover, yield, thallus length and recruit density, as well as benthic flora and fauna. Harvesting only impacted P. dioica thallus length, resulting in 41% smaller thalli compared to unharvested plots during summer, with possible long-term implications (e.g. reproductive output). Strong seasonality of P. dioica cover and yield was observed, peaking during spring and summer. The results suggest high resilience of the opportunistic life strategy of P. dioica under frequent harvesting, but to allow for full recovery, we urge for a recovery period of more than the tested 4 weeks.

Reconstructing the origin and historical biogeography of the Austropotamobius torrentium is hampered by insufficient phylogeographic coverage of the Balkans and deep contradictions in previous molecular dating. The present work extends the phylogeographic coverage to Serbia, a country crucial for understanding the species southward dispersal. Our analysis revealed that the Southern Balkans lineage occurs in most of the country, the Central and southeastern Europe lineage is restricted to the southwest and northeast of the country, while a single population in the north of the country harbors the Lika and Dalmatia lineage, which was previously thought to be restricted to the northern-central Dinarides. Dataset expansion led to revised phylogenetic relationships, which indicated that the Apuseni lineage is not nested within Northern-central Dinarides lineages but arose after the most basal split within Austropotamobius torrentium. This ‘Apuseni first’ phylogeny provides a new perspective for molecular dating, according to which the split between Austropotamobius pallipes and A. torrentium took place in the Late Oligocene, while the formation of the phyletic lineages and the dispersal from the Dinarides to Serbia occurred in the late Miocene and is probably associated with the complex and protracted process of disintegration of the Neogene freshwater lakes in southeastern Europe.

Asexual eukaryotes tend to occupy broader geographical ranges than their sexually reproducing relatives, with this phenomenon seemingly linked to ecological differentiation among closely related asexual and sexual lineages. Here, we used sympatric asexual and sexual Corbicula lineages to assess their ecological niche divergence and genetic differentiation within East and Southeast Asia. The predicted suitable area for asexual lineages was concentrated to Southern China, South Korea, Japan and a small region in Thailand and Vietnam, while that for sexual lineages mainly covered the middle and lower reaches of the Yangtze River in China, Japan, Malaysia, Philippines as well as Indonesia. Potential sympatric distribution of both lineages was found in the Yangtze River Basin in China, the Central and Southern Japan. Anthropogenic activity was an important variable for the distribution of asexual lineages, while precipitation variables underpinned that of sexual lineages. Although both lineages had distinct distribution patterns, the identity and similarity tests overall indicated that the asexual and sexual lineages had similar niche. Genetic analyses suggested that 348 COI sequences from 47 populations were separated into two major clusters; one consisted of sexual lineages, and the other comprised asexual lineages across all studied regions and minor sexual lineages from China. The present study suggests that sexual and asexual Corbicula lineages have similar ecological niches accompanying COI genetic differentiations in East and Southeast Asia.

Cyanobacterial blooms are widespread phenomena, expected to increase in frequency, magnitude, and duration due to a changing climate and increasing temperatures. We looked at remote sensing (optical, microwave, thermal) possibilities to enhance our understanding of bloom dynamics and its parameters, retrievable from satellite data in the shallow, eutrophic, transboundary lake Peipsi. Sentinel-3/OLCI (Ocean_and_Land_Colour_Instrument) and ENVISAT/MERIS (Medium_Resolution_Imaging_Spectrometer) data were used for Chlorophyll a (Chl a) detection, from which bloom parameters were retrieved. Pixels were categorized as “bloom” when Chl a concentration exceeded the long-term average by at least 5%. Maximal bloom coverage was about 100% in all parts of the lake, but on average, the blooms covered 96.5% of Lämmijärv, 85.0% of Peipsi sensu stricto (s.s.), and 84.5% of Lake Pihkva. On average, the blooms lasted 101 days in Peipsi s.s., 78 days in Lämmijärv, and 69 days in Lake Pihkva. Higher water levels resulted in significantly shorter blooms in Lämmijärv and Lake Pihkva. Traditional microscopy gave an overview of the main bloom-formers and their changes over a 20-years period. The importance of Gloeotrichia echinulata P.G.Richter has decreased in the last 10 years in Peipsi s.s and the importance of Aphanizomenon has increased in the entire lake.

The plant diversity of riparian zones has significantly deteriorated due to human disturbances, making their restoration a key focus in research. However, restoration efforts often fail due to the lack of available propagules. Hydrochory, i.e., plants dispersed via water, which plays a critical role in transporting propagules downstream and is pivotal for riparian habitat recovery. Although hydrochory is closely related to the establishment and restoration of downstream riparian vegetation, most previous studies have concentrated mainly on the species richness and the number of propagules dispersed by water, but have overlooked the functional diversity. We explored the temporal variations in functional traits composition and functional diversity of hydrochorous propagules in three upland rivers within the upper Yangtze River catchment, situated in a humid subtropical monsoon climate. We find that during the high flows of summer, these rivers transport more species and exhibit higher functional diversity. This underscores the critical role of high summer flows for breaking the dispersal bottleneck of species with limited dispersal ability, and emphasizes the importance of hydrochory during the flood season for the recovery of riparian vegetation and maintaining high river flows is a critical strategy for restoration in the era of global flow regulation.

Although the invasion dynamics and establishment of quagga mussels (Dreissena rostriformis bugensis) into the nearshore areas of north-temperate lakes are well studied, their continued expansion into deep profundal zones is poorly understood, having implications for offshore benthic and pelagic communities. To assess the expansion of quagga mussels into the Lake Michigan profundal, we used U.S. EPA's Great Lakes National Program Office long-term benthic monitoring data (2007–2022) to document changes in density, biomass, average length, and size-frequency distributions within and across three distinct depth zones (> 30–50 m; > 50–90 m; and > 90 m). We found significant differences in mussel density, biomass, and average length across depth zones. While the average dreissenid density at the > 50–90 m and > 90 m depth zones declined throughout the study period, biomass remained unchanged, and the average length of mussels at > 50–90 m depth zone increased, conflicting trends were found at the station level. We found the greatest variation of station size-frequency in the shallowest zone, while deeper zones followed similar demographic patterns. Our results indicate that the management of quagga mussels requires a combined approach that includes demographic data and considers within station variation.