Journal of the Marine Biological Association of the United Kingdom最新文献

Large-scale outbreaks of the dinoflagellate Karenia mikimotoi caused substantial mortality of abalone, Haliotis discus hannai in Fujian, China in 2012, resulting in 20 billion in economic losses to abalone industries. However, the mechanism behind the mortality, especially the reaction of abalone to this microalgal toxicity, which possibly differed significantly from the former ‘fish killer’ strain in the South China Sea (SCS). Our study revealed that K. mikimotoi FJ-strain exhibited a four-fold higher haemolytic toxicity than the SCS-strain during the late exponential phase. At the microalgal cell density of 3 × 107 cell L−1, the FJ-strain caused abalone mortality of 67% in 48 h, with decreased granulocyte–hyalinocyts ratio and phagocytic activity by 58.96% and 75.64%, respectively, increased haemocyte viability by 4.8-fold and severe gill damage. The toxic effect only worked for the haemolytic toxicity from active algal cells, which were probably produced under the contact of algal cells and abalone gills. However, under exposure to the SCS-strain, more than 80% of individuals survived under aeration. The results indicated that FJ-strain was a new K. mikimotoi ecotype with stronger toxicity. It evoked severe effects, with complete abalone mortality within 24 h under the cascading effect of non-aeration (dissolved oxygen declined to 2.0 mg L−1), when exposed to K. mikimotoi FJ-strain at the above density. Thus, apart from the microalgal toxicity, DO depletion exacerbated the mortality of abalone in the experiment. The massive abalone mortalities in Fujian were probably caused by the combination of microalgal toxic effects and oxygen depletion, leading to immunological depression and histopathological disruption.

Climate change poses a major threat to marine ecosystems, with its effects felt worldwide. A major effect of climate change on marine ecosystems is the rise in water temperature, leading to a northward expansion of habitats for marine organisms. Herdmania momus, a species of ascidians (sea squirts), originally found in tropical and subtropical regions, was introduced to the Korean Peninsula. In this study, we examined the habitat of H. momus along the southeastern coast of the Korean Peninsula between 2016 and 2022. We found that H. momus settlements were observed across the entire survey area, with confirmed habitation in Busan in 2016, Ulsan in 2021, and Gyeongju (the northernmost location) in 2022. The observed habitation trend indicates a rapid geographical expansion, occurring approximately 79 years earlier than previously predicted. These observations demonstrate that marine organisms are undergoing a more rapid geographical expansion than previously projected. These unexpected findings should inform government policies related to proactive measures and strategies for managing the impact of climate change on marine ecosystems.

Post 2004 tsunami and earthquake, the landmass of Andaman and Nicobar Islands (ANI's) experienced uplift (North Andaman and Mayabunder) and subsidence (South Andaman & Nicobar Islands). The altered geomorphology modified the tidal regime, which resulted in mangrove degradation in their current locations and the formation of new intertidal zones potential for mangrove colonization. Avicennia species; a pioneer in mangrove succession was expected to colonize such new intertidal zones. Therefore, to understand the colonization pattern of Avicennia species in these new intertidal zones and their distribution in the old forests, we surveyed 79 sites across ANI's (55 Andaman and 24 Nicobar Islands). Our survey confirms the presence of three Avicennia species namely A. marina, A. officinalis, and A. alba – a new distribution record to the ANI's. Further, A. marina was found to be the most widely distributed, and abundant among three Avicennia species (Relative Abundance (RA) – 97.92%; Relative Frequency (RF) – 68.75%). In contrast, A. officinalis (RA – 1.93%; RF – 26.25%) and A. alba (RA – 0.16%; RF – 5%) were found limited in their distribution and abundance. As per the IUCN Red List, the Avicennia population is decreasing globally, whereas, its population may increase significantly across ANI's due to the availability of vast new intertidal zones. Hence, Avicennia spp. can be utilized in the plantation programs to facilitate rapid colonization in the unvegetated potential mangrove habitats across ANI's. Such an effort will improve the mangrove ecosystem services that were hampered due to mangrove degradation by the 2004 tsunami.