Marine Ecology-An Evolutionary Perspective最新文献

Despite the ongoing and increasingly disruptive process of deoxygenation, deep–sea sharks Hexanchus griseus, Centrophorus uyato, and Oxynotus centrina, continue to access the hypoxic slope waters of the northern Sea of Marmara although the frequency of such excursions remains unknown. This study shows that H. griseus, C. uyato, and O. centrina can tolerate at least moderately hypoxic conditions and may have the potential for much higher hypoxic tolerance than previously appreciated. Investigating the spatial and depth distribution of mesophotic habitats, mainly composed of Eunicella cavolini and Savalia savaglia in the bathyal zone, and investigating their potential use by deep–sea sharks are essential steps for future shark conservation and management plans.

Previous studies on ciliate tintinnids in the Mediterranean Sea have primarily focused on surface and subsurface layers, leaving their vertical distribution in deep oceanic waters largely unexplored. This study investigates the vertical distribution and diversity of tintinnids across multiple depths (0, 80, 150, 250, 400, and 600 m) based on four cruises conducted between 2018 and 2020 in the Eastern Mediterranean Sea. Temperature, salinity, and nutrient levels were recorded at each depth. Despite their relatively low abundance, a considerable species richness was observed. A total of 109 tintinnid taxa were identified, with 46 taxa at the surface, 56 at 80 m and 150 m, 47 at 250 m, 35 at 400 m, and 37 at 600 m depth. Species richness peaked at 80 m depth in October 2018 (37) and December 2019 (35), while the lowest number (6) was observed at 250 to 600 m in September 2019. Tintinnid abundance was significantly influenced by temperature and salinity, with higher abundances in the upper layer (0–150 m). A bimodal vertical pattern was observed, with abundance peaks at the surface (18 Ind.L⁻¹) and 80 m (36 Ind.L⁻¹) in December 2019 and at 80 m (21 Ind.L⁻¹) and 150 m (23.3 Ind.L⁻¹) in October 2018, followed by a decline with increasing depth. Four distinct assemblages were identified based on depth-specific preferences. Notably, nine tintinnid species were recorded for the first time in Lebanese waters. These findings expand our understanding of tintinnid biogeography and underscore the importance of deep-sea sampling.

Many reef ecosystems around the world are threatened by invasive alien species. On the Brazilian coast, the invasive bivalve Isognomon bicolor has recently undergone an expansion in distribution and abundance. In this study, we evaluate the impact of invasive I. bicolor on the native benthic community through an in situ experiment in which the invasive species was removed and the benthic community monitored over the following year. Post-removal, significant changes were observed in the structure of the native community, but the results were different in the two studied sites. We conclude that the establishment of I. bicolor on consolidated substrates can change the structure of the benthic community. Knowledge about the interactions between native and invasive species and how this species alters native communities in different environments is essential for predicting the course of future invasions and mitigating the impacts caused.

Coral reefs in the Mexican Pacific coast have been significantly impacted by the El Niño events in the last decades. During 2015 and 2023, two severe events caused several key coral stress indicators related to sea surface temperature reaching record highs (SST ≅ 32.68°C, DHW ≅ 16.66, ONI = 2.6), resulting in a devastating response across all coral populations of Zihuatanejo, Guerrero. The composition of the substrate changed significantly over a 15-year period (ANOSIM, R = 0.489, p = 0.001). High levels of live coral cover were recorded in 2010 (56.35% ± 38.25%), followed by high cover of bleached corals during the 2015 El Niño event (up to 31.89% ± 20.98%), then pale corals in 2023 (up to 61.33% ± 21.39%), and finally, near-total cover of dead coral in 2024 (86.67% ± 9.02%). Significant changes in algae cover were observed at sites that were still relatively healthy prior to the 2023 El Niño, showing a clear regime shift from reefs dominated by healthy corals to completely dominated by algae after this event. The future of these reefs is now uncertain, especially given the lack of recovery observed from coral losses sustained during the 2015 event. Increased conservation efforts for surviving coral populations along the Mexican Pacific coast, coupled with enhanced monitoring of coral recruitment, are crucial. Carbonate budget monitoring methods, such as Reef Budget, could prove invaluable in tracking the trajectory of change in these reefs.

Axianassa darrylfelderi is a rare species of mud shrimp. Recently, it was discovered in the Mexican Central Pacific; therefore, it is exposed to the strong climate variability of this ecoregion. This study hypothesized that the population structure and dynamics of A. darrylfelderi are affected by variations in environmental conditions. The organisms were collected during 2014, 2015, and 2018—years that featured The Blob and El Niño Southern Oscillation events. The variables temperature, precipitation, and chlorophyll-α concentration did not strongly influence the structure and fecundity but did have a strong influence on the population dynamics. Individual growth was seasonal with slow phases in rainy periods; mortality was high and began at small sizes attributed to estuary runoff, while somatic production was supported by large and abundant organisms that have more stable burrows that require less maintenance. A. darrylfelderi presented similar parameters to other burrowing shrimp, and these vary due to the synergy of the environmental variables of each season.

The biodiversity of copepod populations was studied over a 4-year period (2014–2017) in Bou Ismail and Algiers Bays through qualitative and quantitative monitoring. The results support three objectives: (i) the seasonality of copepod abundance subject to temperature, salinity, and food availability (Chl a concentrations) regulations; (ii) the trophodynamics of copepods as prey for gelatinous zooplankton and jellyfish; and (iii) the impact of climate on species abundance patterns. A total of 53 copepod species are recorded and encompass 3 orders (calanoida, cyclopoida and harpacticoida), 20 families, and 31 genera. These are either perennial with Atlantic characters (11 species), neritic (11 species) or bathymetric migrants (14 species). The rare species (Fi < 25%) are qualitatively important (22 species). The abundances are subject to geographical and temporal variability. The functioning of the ecosystems is regulated by characteristic populations, so-called abundant species Temora stylifera, Oithona plumifera, Nannocalanus minor, Neocalanus gracilis, Subeucalanus elongatus, S. monachus, Centropages typicus, C. hamatus, Microcalanus pygmaeus, Mecynocera clausi, Agestus flaccus, A. limbatus, Oncaea mediterranea, Xanthocalanus mixtus, Triconia minuta). By using a Principal Components Analysis, their increase is characterized by a seasonality that is strongly correlated with hydrological (temperature, salinity and chlorophyll a), climatic (NAO index) variations, and is also involved in prey–predator relationships where 4 seasonal trends are described. Multimodal Growth Populations (MGP; Oithona plumifera and Temora stylifera) have affinities for all seasons. Trimodal Growth Populations (TGP; N. minor and O. mediterranea) have winter, spring, and summer affinities. Bimodal Growth Populations (BGP; in spring and summer for M. clausi and E. elongatus elongatus and in winter and spring for S. monachus). Unimodal Growth Populations (UGP; in spring for M. pygmaeus, N. gracilis, A. flaccus, A. limbatus, C. hamatus, C. typicus, X. mixtus and T. minuta). The qualitative distributions of richness species and their occurrence did not show any seasonality.