Marine and Freshwater Research最新文献

Habitat quality (HQ) is vital for achieving sustainable regional development. Understanding the spatial patterns and temporal evolution of HQ in the context of land use–cover change (LUCC) is crucial for promoting ecological civilisation and high-quality growth, especially for regions with rapid economic development.

In order to analyse the impact of LUCC on habitat quality in the coastal areas with frequent human activities.

This study focused on the Greater Bay Area around Hangzhou Bay and analysed the HQ on the basis of LUCC data during 2010–2020 by using the InVEST model and spatial autocorrelation analysis. Additionally, land-use data for multiple scenarios in 2030 were predicted using the PLUS model, and the variations in land use and HQ in the study region during 2020–2030 were assessed.

During 2010–2020, the construction land in the region expanded by 1932.79 km², primarily at the expense of cropland and water areas. The mean HQ values were 0.6287, 0.6181 and 0.6037 for 2010, 2015 and 2020 respectively, indicating a continuous decline. Spatially, HQ exhibited strong clustering during this period. However, there was a clear trend of fragmentation and reduction in ‘high–high’ cluster areas along the coast, mostly owing to the transformation of water areas and wetlands into construction land and cropland. In the projected scenarios (natural development, ND; economic development, ED; crop protection, CP; and ecological protection, EP) for 2030, the mean HQ values are estimated to be 0.5881, 0.5837, 0.5915 and 0.5965 respectively. Compared with 2020, there will be a certain decrease in HQ, with the EP scenario showing the lowest decrease of 0.0052.

The HQ changes were closely linked to LUCC, the construction-land expansion was the main cause of HQ destruction in the Greater Bay Area around Hangzhou Bay. To alleviate the trend of declining HQ, it is essential to select appropriate development scenarios for each city in the region and coordinate the development of the cities.

These findings provide valuable insights for promoting sustainable economic growth in the Greater Bay Area around Hangzhou Bay.

The increasing number and length of droughts is a threat for many freshwater turtle populations.

Our study investigated the movement and survival of Emydura macquarii, Chelodina expansa and Chelodina longicollis in drought and flood conditions.

Turtles were captured in the Gwydir Wetland, New South Wales, Australia. We assessed the species composition of live captures and carcasses over the drought to assess relative survival among species. Using radiotelemetry, we compared the movement of E. macquarii and C. longicollis over a severe drought followed by a flood.

For tracked turtles with known fates, 28.6% of E. macquarii and 7.1% of C. longicollis, died during the drought. The proportional composition of captured turtles compared with those of desiccated shells suggested that C. expansa had the highest mortality. E. macquarii and C. longicollis both appeared to navigate terrestrially and moved further in the flood water than in the drought, but C. longicollis moved further generally.

Our findings suggest that turtles in isolated wetlands of the northern Murray–Darling Basin are at high risk of mortality during severe drought.

Environmental water delivery during periods of sustained drought will be critical to ensure persistence of populations of long-lived species such as turtles.

The Murray–Darling Basin serves as a crucial habitat for aggregating waterbirds; however, decades of large-scale regulation of rivers and water resources have adversely affected waterbird breeding in the Basin.

To understand the characteristics of wetlands that attract and support aggregating waterbirds, focusing on identifying environmental conditions conducive to waterbird breeding.

In total, 52 wetland sites across the Murray–Darling Basin, with high waterbird abundances, were identified, of which 26 supported waterbird breeding. Classification models were developed using temporally static and dynamic environmental datasets to discern wetland characteristics associated with waterbird breeding.

Analyses showed that wetlands supporting waterbird breeding contained a maximum inundated area of ‘other shrublands’ exceeding 3.635 km² and variation in normalised difference vegetation index, possibly reflective of a ‘boom and bust’ ecological response.

Understanding the habitat requirements of wetlands to prompt waterbird breeding is critical for effective environmental water management and conservation strategies.

Targeted wetland management and environmental water allocation to support waterbird breeding populations in the Murray–Darling Basin is essential for continued waterbird breeding. There is a need for continued research to refine management strategies and ensure the long-term sustainability of waterbird populations in the face of ongoing environmental challenges.

Sailfin catfishes (Pterygoplichthys spp.) are a group of fishes introduced to several freshwater habitats across the globe. Sailfin catfishes are a hard-armoured fish with no economic importance as a food species. These catfishes have been reported to be affecting the growth of several economically valuable species that are native to different freshwater ecosystems. In this manuscript, we developed a TaqMan-based assay targeting the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene, to specifically detect the presence of catfishes by environmental DNA (eDNA) measurements. The developed assay was screened against 16 species of fish and mussel that co-occur in the habitats along with sailfin catfishes, and the qPCR reaction did not have any non-target amplifications. The assay was further validated under laboratory conditions by measuring eDNA from tanks having different biomass of catfishes (1 and 0.5 g L⁻¹), and the copy number of the amplified product was directly proportional to the biomass maintained in the tanks. Overall, the study provides a robust molecular tool based on eDNA measurements to facilitate detection of invasive sailfin catfishes and, in turn, contributes towards the management of the invaded habitats.

The fugacity of surface-seawater CO₂ (fCO_2sw) and the sea–air CO₂ fluxes in the south-western tropical Atlantic (SWTA) were studied to increase the knowledge about the carbon cycle in this region.

This paper aims to describe the distribution of fCO_2sw in SWTA.

The fCO_2sw was measured from 2008 to 2020 by volunteer merchant ships with an onboard system that measures pCO₂ while the vessels were underway.

Higher values occurred north of 8°S than in the region south of 8°S. The north is a strong source of CO₂ for the atmosphere, with an annual mean value of 3.14 ± 0.52 mmol m⁻² day⁻¹. The south is a weaker source of CO₂, with an annual average of 0.93 ± 0.90 mmol m⁻² day⁻¹. In the months of July and August, a weak sink of CO₂ was observed, with a mean of −0.55 mmol m⁻² day⁻¹.

The differences between these two regions are explained by the origin of the surface-water masses encountered along the ship track. The central branch of the South Equatorial Current (SEC) transports surface water, with a higher CO₂ concentration and lower salinity, north of 8°S, whereas the surface waters between 8 and 14°S come from the southern branch of the SEC. The intertropical convergence zone is another physical process influencing the region north of 8°S.

Handling of wild animals can have adverse effects on individuals that scale up to affect populations and ultimately species. Limited mobility and high harvest pressure expose the threatened Australian freshwater crayfish (Euastacus armatus) to multiple handling events by fishers that cause egg loss.

Our aim was to assess the effects from harvest pressure on the reproductive output of an E. armatus population.

A stochastic model based on empirical data and estimated harvest pressures was used to predict the effect of repetitive handling of individuals on a population of E. armatus subject to harvest and consequent egg loss.

Egg loss resulted in substantial predicted population-level declines, most pronounced in populations subject to high and extreme harvest pressures.

We advocate educating fishers to visually determine the reproductive condition of female crayfish by inspecting gonopore setation, eliminating the need for unfurling the tail.

Maximising species reproductive output through limiting handling loss supports the management and conservation of E. armatus populations.

Overfishing is a major cause of decline for many shark species globally, which can be largely offset by shifting consumer demand to sustainable harvests. The inherent difficulty identifying shark species after processing makes informative labelling fundamental to achieving a sustainable market.

We evaluated the level of mislabelling in Australia from shark flesh samples obtained from seafood suppliers across the country.

We used sequence data from the cytochrome oxidase subunit one gene (COI) and the 12S mitochondrial RNA gene (12S) to identify genera and likely species.

We used genetic sequence data to identify species from tissue samples from 91 fillets labelled as shark. Of these, 64 (70%) were mislabelled, and 9 comprised three species listed as threatened in Australia, the scalloped hammerhead (Sphryna lewini), greeneye spurdog (Squalus chloroculus) and school shark (Galeorhinus galeus). The scalloped hammerhead and greeneye spurdog were being sold under the label ‘flake’. Overall, 70% of samples were mislabelled and the proportion of mislabelling was significantly greater in takeaways compared with fish markets and wholesalers.

High levels of mislabelling of shark product in Australian fish markets and seafood shops was apparent both with respect to the genetically identified shark sample not matching the label and the use of ambiguous labels that do not adhere to the Australian Fish Names Standard. Mislabelling masked the presence of threatened species.

Our results reveal labelling practices that are not providing consumers with reliable information to identify shark products, and we demonstrate the utility of molecular methods in seafood trade monitoring.

Hydrological dynamics are crucial in fish ecology.

To evaluate the effect of the flood pulse on the feeding ecology of Doras higuchii in the reduced-flow section of the Belo Monte dam, Xingu River, Brazil.

Collections were conducted between December 2020 and November 2021. The fish were measured and had their stomachs removed. Muscle tissue was also extracted for stable-isotope analysis. Stomach contents were inspected to assess diet, testing the influence of hydrological periods by using GLM. In addition, we evaluated the effect of the flood pulse on the δ¹³C and isotopic ratios of individuals

In total, 362 specimens of D. higuchii were analysed, highlighting a diet mainly on the basis of sediment (74.9%) and aquatic insects (24.8%), not varying between periods characterising the species as a specialist for having detritivorous habit, as well as the extension of the trophic niche. There was variation in food intensity, with higher average food consumption in the flood period. The isotopic composition (δ¹³C and δ¹⁵N) also did not differ between periods. Finally, δ¹⁵N did not vary by length class.

This information helps understand the interface between environmental and biological factors in an environment affected by a hydroelectric dam.

Our results may help fill gaps in knowledge about the diet of doradid fishes.

Water-regulation services significantly affect local social and economic development in the Qinghai area of Qilian Mountain National Park, China, and also affect the role of a ‘solid reservoir’ in China.

The value and change trend of water regulation was assessed through the evaluation and prediction of the water-regulation value of ecosystems.

InVEST water yield model and SVR model are used to evaluate and predict the water-regulation value of ecosystem in this study.

Grassland plays an important role in water regulation, although the area of forestland is not large, its water-regulation monetary value in 2020 accounted for 13.92% of the total evaluation value. From 2010 to 2020, the physical value of water regulation increased by 2.24% and the monetary value increased ~0.97% annually. In 2030, the amount of physical and monetary value of water regulation will be increased.

Grassland plays an important role in water regulation. It is necessary to strengthen the asset management of water regulation and optimise the ecological resources.

The study findings are utilised to enhance monitoring and establish ecological big-data platform, thereby elevating the quality of national park development management and decision-making services.

High temperature and oil pollution are typical examples of environmental stress to sea cucumber (Apostichopus japonicus) in northern China.

Evaluate the combined effects of high temperature and oil pollution on the immune responses of sea cucumbers.

In this study, we investigated the immune responses in the respiratory tree of sea cucumber subjected to the optimal temperature (16°C), high temperature (26°C), Oman crude oil (OCO) water-accommodated fractions (WAF) at 16°C (WAF + 16°C) and OCO WAF at 26°C (WAF + 26°C) for 48 h.

All three treatments significantly up-regulated total antioxidant capacity and disturbed active oxygen species homeostasis in sea cucumbers. Moreover, all three treatments caused immune-enzyme activity disorders, manifested by a significant increase in acid–alkaline phosphatase and nitric oxide synthase activities and a noticeable decline in lysozyme activity.

Combining the integrated biomarker-response index (WAF + 26°C > 26°C > WAF + 16°C), the combined stress could result in a more adverse effect on the immune responses of sea cucumbers than do high temperature or oil pollution alone, which might further exacerbate the health challenges for sea cucumbers in response to environmental stress.

This study has provided an insight into the immune impacts in benthic organisms caused by high temperature and oil pollution.