Aquatic Conservation-Marine and Freshwater Ecosystems最新文献

Since the early 1980s, the recruitment of the European eel (Anguilla anguilla L.) to the European continent has declined dramatically. There is a lack of research utilizing biotic variables to determine European eel habitat selection, particularly in short karstic coastal catchments. This study provides the first reference on the habitat preferences of European eels in the Croatian karst region. The research was conducted at six lotic waterbodies within the Adriatic Basin in Croatia. A total of 380 European eel specimens were sampled. Environmental parameters were recorded at each sampling location, including water quality, bottom substrate, instream cover and the degree of anthropogenic alteration. Individuals were classified into three length classes: Class 1 (< 20 cm); Class 2 (20–45 cm) and Class 3 (> 45 cm). Multivariate analysis identified habitat degradation, instream cover, conductivity and sea distance as key factors influencing European eel habitat preferences. Class 1 was associated with lower altitude, proximity to the sea and coarse bottom substrate. Class 2 exhibited a strong association with greater distance and higher altitudes, water depth and channel width. Class 3 was primarily associated with conductivity, instream cover and heterogeneity of bottom substrates. All three length classes show high sensitivity to modifications of the riverbanks or riverbed. These alterations, along with the loss of instream cover, may lead to a significant decline of the species and local extirpation. This study could help prioritize areas for habitat protection and support conservation efforts aimed at restoring European eel habitats in short, isolated Mediterranean rivers.

Biomagnification of environmental toxins is influenced by food chain length, which in turn is shaped by habitat connectivity and food web dynamics. Dam removals are increasingly used as restoration measures, yet their role in reducing contaminant exposure has rarely been quantified. We tested if mercury concentration in pike (Esox lucius) muscle tissue was reduced by removals of lake outlet dams in five oligotrophic, boreal lakes, using a before-after design. For pike of average size (50 cm), mean mercury concentration decreased from 843 to 598 μg Hg per kg muscle tissue following dam removal, which corresponds to a 29% reduction. These results show that dam removal can lower mercury bioaccumulation in apex predators, providing an additional conservation benefit of restoring natural aquatic connectivity, with positive implications for both ecosystem integrity and human health.

In the first study on Neogoniolithon species for the Southwestern Atlantic Ocean, based on both molecular (COI-5P, psbA and SSU rDNA) and morpho-anatomical data, three taxa were identified for the Brazilian coast, including two new species. DNA-based species delimitation methods distinguished Neogoniolithon crypticum sp. nov. from other sequences morpho-anatomically identified as N. brassica-florida, which has its type locality in South Africa. Neogoniolithon fluminense sp. nov. has the length of the carposporangial conceptacle diameter as a diagnostic feature, which is smaller than in other species. Neogoniolithon rhizophorae is a new record for this region and includes the first reporting of carposporangial conceptacles for the species. This study provides additional characters considered useful for morpho-anatomically distinguishing Neogoniolithon species and includes comparisons of branched and unbranched thalli, trichocyte arrangement, carposporangial conceptacle chamber diameter and the number of cells in the carposporangial conceptacle roof.

Freshwater mussels are ecosystem engineers: They modify substrates through burrowing, mediate water quality through filtration, provide food and habitat for other organisms and play a substantial role in the biogeochemical cycling of nutrients; they are also seriously threatened globally. This study used a combination of predictive modelling, hydrological analysis and field surveys to explore the extent of subpopulation decimation of the endemic hyriid freshwater mussel, Alathyria jacksoni, in Australia's northern Murray–Darling Basin (nMDB) after one of the most severe hydrological droughts on record. Predictive species distribution modelling suggested A. jacksoni should occur in the mid to lowland reaches of most rivers of the nMDB but be absent from the westerly Warrego and Paroo Rivers. Field surveys during and after the severe drought of 2017–2020 found that mussels did occur in the reaches as predicted, but in a large number of sites surveyed, mussel mortality was extreme at 97–100%. Hydrological analysis showed the duration of cease to flow (CTF) events during this drought was substantially longer than the maximum CTF duration for the preceding 37 years. This dramatic increase in the duration of dry conditions has had a devastating impact on mussel subpopulations and highlights the risk to northern mussel subpopulations of the combined impact of anthropogenic water resource use and increasing hydroclimatic variability related to climate change. Given the importance of freshwater mussels in riverine ecosystems, the loss of this large benthic invertebrate over an extensive area of river system is likely to have profound ecological and ecosystem impacts.

Turtles are among the world's most endangered vertebrates, with habitat destruction and predation as major contributors to population declines. Hatchling release programmes are increasingly implemented to enhance juvenile recruitment in threatened populations, but limited understanding of hatchling ecology impedes evidence-based management. To address this, we tracked western saw-shelled turtle (Myuchelys bellii) hatchlings using VHF micro-transmitters to quantify movement, habitat preferences, and survival during their first 2 weeks in the wild. We also compared soft-release and hard-release methods. Hatchlings moved an average of 47–62 m daily, dispersing both up- and downstream. Movement was influenced by water temperature and level, with higher water levels prompting increased downstream movements. The maximum cumulative distance moved by an individual hatchling was 2008 m over 13 days of tracking. Strong diurnal movement patterns were observed. Hatchlings predominantly used vegetation along the water's edge (99% of observations). They preferred shoals over steeply descending underwater banks and selected sedge-dominated areas more often than expected, avoiding phragmites-dominated areas, bare banks, and open water. Hatchling survival rates exceeded 90% during the tracking period. A comparison between soft- and hard-release methods revealed no advantage for soft-release animals. Our findings suggest that releasing M. bellii hatchlings into preferred microhabitats could enhance conservation outcomes. Furthermore, we highlight the crucial role of vegetative cover along stream edges in providing shelter for hatchlings.