Aquatic Conservation-Marine and Freshwater Ecosystems最新文献

Rhodolith beds (RBs) are known to increase the seabed complexity and act as a hotspot, supporting a unique biodiversity. This increased structural complexity due to the presence of rhodolith nodules is expected to influence benthic diversity at a local scale. To investigate this further, we tested the hypothesis that high-density rhodolith beds hold higher meiofaunal diversity than low-density beds. We used metabarcoding (V9 hypervariable region from 18S SSU rRNA) on sediment samples from a region with extensive rhodolith beds in the Eastern Brazil Marine Ecoregion, with distinct areas covered by high- and low-density beds. The sediment underneath high-density beds showed higher food availability (biopolymeric carbon) and organic matter quality (protein content and protein-to-carbohydrate ratio); however, meiofaunal composition and phylogenetic diversity was similar among all rhodolith beds sampled in the study area. Shannon's diversity was lower in high-density beds, which may be attributed to the higher organic matter content and quality supporting strong competitors, such as crustaceans and annelids that may dominate and suppress the presence of other meiofaunal taxa. Our results showed that rhodolith beds host a number of meiofaunal zoobenthos that are rarely sampled with traditional morphology-based methods, and we suggest that metabarcoding may become an important complementary method to study rhodolith beds globally. As assessing biodiversity is a prerequisite for any conservation measures, this study can provide insights when managing valuable marine habitats.

Amidst accelerated degradation of marine ecosystems due to anthropogenic disturbances, marine protected areas (MPAs) have been implemented globally to protect marine biodiversity, mitigate ecosystem degradation and replenish fisheries. In many countries, the creation of MPAs increased after the 2011 Aichi Targets, but in most cases, MPAs face significant operational and logistical challenges and suffer from important structural limitations that restrict their efficacy. Here, we use novel databases of taxonomic and functional diversity of 2125 coastal species (< 30 m depth), habitat continuity and climate velocities to assess the efficacy of the existing MPAs located in the Tropical, Southern, Chilean and Magellan ecoregions of the Eastern Pacific (EP). We then use optimization models to locate new MPA sites that improve protection of geographic rarity and maximize their role as climate refugia while maintaining total area protected. Existing MPAs captured between 75% and 95% of species richness in all ecoregions, largely due to the large biogeographic ranges of most species, but under-represented rare endemic species, capturing between 3% and 66%, of single-occurrence species among ecoregions. In general, MPAs are located in areas of ‘moderate’ to ‘high’ functional diversity, representing relatively well this feature within ecoregions, but less effectively across all SEP. There is a large geographical mismatch between current MPA locations and regions that might act as ‘climatic refugia’, which threatens the long-term conservation value of existing MPAs. Our spatial optimization models provide valuable support for enhancing the effectiveness of MPAs, through complementation or relocation, improving their efficacy to conserve different aspects of biodiversity and resilience in the face of climate change in all ecoregions. Notably, these improvements do not necessitate expanding the total area under protection, underscoring that current MPA siting did not prioritize these criteria and suggesting that modifications may be socio-politically possible.

Coastal mussel populations have declined worldwide, largely due to overharvesting, water pollution, climate change, invasive species and other anthropogenic stressors. Mussel restoration projects have emerged to combat these declines, with restoration methods primarily prioritizing mussel transplantations from healthy populations into degraded areas. While this technique can be effective, it is also costly and often infeasible to upscale. One alternative restoration technique is assisted juvenile recruitment through plantigrade or spat provision, which has facilitated the creation of mussel reefs on small scales. This study assessed the effectiveness of upscaled assisted recruitment of juvenile mussels, specifically using plantigrades attached to macroalgae experimentally placed into restored mussel reefs and adjacent bare cobble habitat. Ultimately, low natural settlement of plantigrades to macroalgae (eight plantigrades per gram macroalgae) and high post-settlement losses of plantigrades (> 99%) resulted in assisted recruitment being unsuccessful as very few juvenile mussels small enough to have originated from the plantigrade provision (0.6 juveniles/m²) were found in either habitat. These results demonstrate two key barriers limiting the success of assisted recruitment as a restoration technique: highly variable natural settlement processes to macroalgae and low successful progression from post-settlement plantigrades to established juveniles due to mortality or emigration. Addressing these limitations will require assessing more reliable sources of plantigrades, such as hatcheries, and identifying the mechanisms currently impeding the transition of plantigrades to juvenile recruits.

Thermal anomalies caused by climate change have emerged as a major threat to reef ecosystems globally. While the effects of warming oceans have been extensively investigated in tropical reefs, its effects on subtropical reefs, where coral diversity is lower, remain largely unstudied. We analysed the spatial distribution, mean cover and health status of scleractinian corals in the subtropical rocky reefs of the Alcatrazes Archipelago, a no-take marine protected area located 30 km off the coast of São Paulo state, Brazil (24° S). Data were collected before (2018) and after (2022) the most intense marine heatwave ever recorded in the region, in 2019, using either fixed or random photoquadrats. Five scleractinian corals were recorded as follows: The zooxanthellate massive species Mussismilia hispida and Madracis decactis, the azooxanthellate solitary corals Astrangia spp. and Coenocyathus sebroecki and the invasive sun coral Tubastraea spp. M. hispida and M. decactis were the most abundant species, particularly in the sheltered sites, while Astrangia spp. and C. sebroecki were less abundant and only recorded in the exposed side of the island. In the single site where Tubastraea spp. colonies prevailed, other coral species were nearly absent. Both M. hispida and M. decactis exhibited resilience to the 2019's bleaching event, with their abundance remaining almost the same in 2022. Our findings add evidences to the emerging idea that subtropical reefs in the southwestern Atlantic may serve as refuges during future thermal anomalies, highlighting the importance of monitoring these reefs in the context of changing habitats driven by warming oceans.

Non-native species represent a significant threat to biodiversity, particularly in aquatic environments where they are often introduced for purposes such as fishing or the aquarium trade. This study aimed to evaluate the influence of isolation and the size of federal protected areas (PAs) on the number of non-native and native freshwater fish species in Brazilian PAs. Data from Brazilian PAs were gathered, including year of creation, buffer of human impacts around the PA, PA categories, coverage by freshwater, tourist visits, sampling sites, geographical coordinates (predictor variables) and information on the number of non-native and native freshwater fish species (response variables). Linear regression analysis was employed to examine the influence of predictor variables on the number of non-native and native fish species. A total of 33 different non-native fish species were identified, with Poecilia reticulata, Hyphessobrycon eques, Hoplias lacerda and Cichla kelberi being the most widespread, occurring in 15, 7, 5 and 4 distinct PAs, respectively. The overall fish biodiversity within PAs encompassed 2670 species, with the National Park of Anavilhanas and the Environmental Protection Area of Ilha e Várzea do Paraná exhibiting the highest species richness. Greater human impact, larger coverage by freshwater and increased sampling effort were positively correlated with the number of recorded non-native species. Factors such as year of creation, type of PA and tourist visitation did not have a significant effect. In contrast, native species exhibited a higher number of occurrences in PAs with lower human impact, longer histories, larger freshwater coverage areas and more extensive sampling efforts. These findings underscore the necessity for comprehensive management strategies to mitigate the impact of non-native species on biodiversity within PAs.

Despite its biogeographical importance and high endemism, the freshwater biodiversity in Algeria and the wider arid region of North Africa has been significantly under-researched and underestimated. Mayflies (Ephemeroptera) are crucial for the maintenance of ecological integrity of hydrosystems and could serve as indicators of changes of North African freshwater biodiversity. This study focuses on mayflies in Algeria, particularly in the Djurdjura Mountains, including the Djurdjura National Park in central-northern Algeria. The aim is to establish an updated checklist, map the distribution of mayfly species and determine the ecological requirements of their assemblages. Twenty-four mayfly taxa were identified during the study, including five new, undescribed species. Through multivariate analysis, the study revealed that land-use practices, altitude and slope orientation significantly influenced mayfly assemblages in the studied streams. This study emphasises the urgent need for conservation action and lays the foundation for future research and conservation efforts that are essential to protecting the integrity of the critical freshwater habitats of the Djurdjura Mountains, which are hotspots for North African endemic species.

Many years of land use transformation within river valleys have drastically changed these ecosystems. Black poplar is a tree species characteristic of riparian habitats, but due to specific environmental requirements, their populations have difficulties with natural regeneration. Here, we genotyped 623 black poplar individuals from four populations located along different sections of the Vistula River. This river, which is the largest in Poland, is characterized by the variable degrees of regulation and transformation of its natural environment. Each black poplar population consisted of a group of mature trees and a group of naturally regenerated trees. Our main goal was to assess the differences between the gene pools of mature trees and natural regenerations. The results showed that all populations were characterized by high and comparable values of the parameters of genetic diversity. Despite this, we distinguished two to three genetic clusters (depending on the method). The genetic differentiation among the natural regeneration groups was almost twice as high as that among the mature tree groups. The gene pools of most natural regenerations diverged from the gene pools of mature tree groups except for one population. This was also the only population where fully generative regeneration occurred, growing in the least transformed middle section of the river. Our research confirms the need to monitor seedlings and saplings along major rivers and to conduct molecular analyses to assess their gene pools. It can be assumed that due to the lack of suitable areas for seed germination, black poplar will reproduce mainly vegetatively, which may be a way to ensure the survival of the species. However, the adaptive potential of the youngest generations is unknown, especially in the face of progressive climate change. We conclude that to preserve black poplar genetic resources, ex situ protection in the form of local clone archives is necessary.

This study provides novel data on fecundity and oviposition rate of Rioraja agassizii and complementary information on incubation period in captivity. Two females of R. agassizii were maintained in captivity over 1-year period. Oviposition rate was 0.28 and 0.26 egg cases per day, and fecundity was 114 and 92 egg cases for each female. Incubation period was determined for two embryos resulting in 105 and 114 days with average incubation temperatures ranging from 17.5°C (± 0.81) to 22.1°C (± 1.32). Captive studies contribute to a better understanding of the reproductive biology and complement investigations carried out in the wild.

Wetlands are pivotal in supporting the natural ecosystem and maintaining biodiversity while being susceptible to anthropogenic activities and climate change. However, monitoring wetlands over a large geographical and temporal extent is challenging. Vegetation health can be considered a good indicator of wetland conditions, and measuring chlorophyll content will provide insight into vegetation health. Linking wetland species mapping from chlorophyll spectral indices to local and regional conservation strategies could improve biodiversity conservation. Here, we apply this to Keetham Lake, India, using machine learning methods (relevance vector model) and hyperspectral measurements. From 10 chlorophyll-sensitive spectral indices, we identified four as best performing, particularly for: TVI + CCCI + NDRE for calibration and NDRE + TVI for validation data. The least performing combinations were MCARI for calibration and TVI + CCCI + NDRE + MCARI for validation. Overall, we identified that NDRE + TVI was the best-performing pair of spectral indices for chlorophyll assessment and implementation in wetland species. This approach allows for precise mapping of wetland species, providing data on their extent and the area they cover. By creating a digital database, this method enables long-term monitoring of changes in wetland species' numbers and distribution, helping to assess trends of increase or decline in freshwater ecosystems. Such strategies are vital for supporting both local and global conservation efforts, offering insights for forward-looking, data-driven preservation initiatives.

Freshwater biodiversity is declining sharply. The conservation of these biodiverse habitats has generally depended on their designation as protected areas, but specific groups such as plankton tend to be overlooked. The Salado River (Argentina) constitutes a highly characteristic morphologic feature of the pampas, having a basin of 150,000 km². The Las Flores system, particularly, is key in the development of the river, and the presence of two tributaries adds landscape heterogeneity with habitats such as shallow lakes, backwater ponds and wetlands. Our aim in this work was thus to evaluate the Salado River conservation status by measuring the specific richness of its planktonic community in order to argue for the Salado's establishment as a protected reserve. An analysis of the phytoplankton and zooplankton assemblages after several years of sampling in the river, streams and backwater ponds indicated that habitat heterogeneity increased the diversity of the region and that sites such as backwater ponds or streams were critical for the functioning of the river system as a whole through adding particular species or acting as species reservoirs. This supports habitat fragmentation in the area, which combined with environmental heterogeneity contributed to high ß diversity values. However, such separation also involves a trade-off because prolonged isolation between subsystems can result in net species loss. Finally, the present work focused on the significance of biodiversity at the landscape level, with planktons as a model for the conservation of a principal site in one of the main rivers of Argentina.