Toxicological effects of cadmium on deep-sea mussel Gigantidas platifrons revealed by a combined proteomic and metabolomic approach

IntroductionMarine metal contamination caused by deep-sea mining activities has elicited great concern from both social and scientific communities. Among the various metals deep-sea organisms might encounter, cadmium (Cd) is a widely detected metal that in very small amounts is nonetheless capable of severe toxicity. Yet due to both remoteness and technical challenges, insights into the effects of metal exposure resulting from mining activities upon deep-sea organisms are limited.MethodsHere, we investigated Cd’s toxicological effects on deep-sea mussels of Gigantidas platifrons exposed to 100 or 1000 g/L of Cd for 7 days; an integrated approach was used that incorporated proteomics and metabolomics along with traditional approaches (metal concentrations, metal subcellular distribution, and anti-oxidative and immune-related biochemical indexes).Results and DiscussionResults showed that Cd exposure caused significant Cd’s accumulation in mussel gills and redistribution of Cd among subcellular compartments, with cellular debris being the primary binding site. Although anti-oxidative enzymes activities (superoxide dismutase and catalase) were not significantly altered in mussel gills of both exposed groups, the markedly increased level of glutathione S-transferase detected via proteomic technique clearly evinced that deep-sea mussels suffered from oxidative stress under Cd exposure. Besides, altered activities of acid phosphatase and alkaline phosphatase assayed by traditional methods along with the predominant presence of largely altered immune-related proteins detected by proteomic data strongly revealed an immune response of deep-sea mussels elicited by Cd. In addition, results of proteomics combined with those of non-targeted metabolomics demonstrated that Cd could exert toxicity by disrupting cytoskeleton structure, ion homeostasis, and primary metabolisms of energy, lipid, and nucleotide in deep-sea mussels. As demonstrated in this study, proteomics and metabolomics can be used in tandem to provide valuable insights into the molecular mechanisms of deep-sea organisms’ response to Cd exposure and for helping to discover potential biomarkers for application during deep-sea mining assessments

Progress of Chinese zooplankton ecology research in Prydz Bay, Antarctica

Zooplankton are considered an important trophic link between primary producers and higher trophic level species in the Southern Ocean ecosystem. Since 1989, when the Chinese Antarctic Zhongshan Station was built, zooplankton have regularly been sampled and investigated in Prydz Bay through oceanographic surveys of each Chinese National Antarctic Research Expedition. This review summarizes the main results from zooplankton ecology studies conducted in Prydz Bay by Chinese researchers. Major topics covered in this review are: (1) a description of the biology and ecology of Antarctic krill (Euphausia superba), the key zooplankton species of the Southern Ocean ecosystem; (2) zooplankton community structure, including the horizontal distribution in the epipelagic region and vertical distribution between 0−1500 m; (3) feeding ecology of dominant species such as Antarctic krill, salps and copepods; (4) a short introduction to the molecular research; and (5) prospects for future research

Marine protected areas in the Southern Ocean: status and future

Marine protected areas (MPAs) in the Southern Ocean are receiving more and more global attention. The Southern Ocean is one of the world’s last regions not yet seriously impacted by human activities, signifying its ecological importance and unique value for scientific research. In response to climate change and growing commercial fishing interests in the Southern Ocean and their impacts on the marine ecosystem, the Commission on the Conservation of Antarctic Marine Living Resources (CCAMLR) is reacting to growing international pressure to establish a system of MPAs in the Southern Ocean to manage fisheries and conserve vital species—such as the keystone resource Antarctic krill and the dominant fish predator Antarctic toothfish—as well as to protect whole ecosystems. This review summarizes progress in the establishment of MPAs in the Southern Ocean by focusing on several major topics: (1) the current status of MPAs in the Southern Ocean; (2) the purpose and objective of MPAs in the Southern Ocean; (3) a short description of the largest high-sea MPA (the Ross Sea MPA); (4) ecological observation and monitoring for the planned MPAs in the Southern Ocean; and (5) the importance of international cooperation in the design, establishment and future management of MPAs in the Southern Ocean

Restructuring of a zooplankton community by perturbation from a wind-forced coastal jet

The impact of transient wind events on an established zooplankton community was observed during a field survey in a coastal region off northern Norway in May 2002. A transient wind event induced a coastal jet/filament intrusion of warm, saline water into our survey area where a semi-permanent eddy was present. There was an abrupt change in zooplankton community structure within 4–7 days of the wind event, with a change in the size structure, an increase in lower size classes less than 1 mm in equivalent spherical diameter (ESD) and a decrease in larger size classes greater than 1.5 mm in ESD. The slope of zooplankton biovolume spectra changed from −0.6 to −0.8, consistent with the size shifting towards smaller size classes. This study shows that even well established zooplankton communities are susceptible to restructuring during transient wind events, and in particular when wind forcing induces horizontal currents or filaments

Macrofauna community of the cold seep area at Site F, South China Sea

A cold seep is one of the typical deep-sea chemical energy ecosystems and a hotspot for studying unique life processes and biogeochemical cycles in the deep sea. Macrofauna, which is one of the most important components of the cold seep ecosystem, has not been thoroughly studied. We examined the macrofauna community at Site F using images collected in 2016 by an imaging and laser profiling system and biological samples collected in 2020 and 2021 by TV grab and a remotely operated vehicle. In total, 41 species were found. The overall number of macrofauna identified at Site F (20,000 m2) reached 252,943 individuals, and the biomass reached 726.15 kg by dry weight. As the dominant species, Gigantidas platifrons and Shinkaia crosnieri reached their highest densities of 629 and 396 individuals/m2, respectively. The comparisons between different stations revealed that the diversity and density, even the biomass of dominant species, were much higher in the south than in the north at Site F in 2020. Correlation analysis showed that methane had a positive effect on macrofauna density. Compared with S. crosnieri, G. platifrons seems to be more adapted to the harsh cold seep environment. Methane consumption rates of the dominant species show that macrofauna are important in influencing seafloor methane fluxes. Our findings provide valuable insights into the ecology, community structure, and biota-environment interaction in the cold seep at Site F

Distribution and abundance of euphausiid larvae and salps during austral summers in Prydz Bay, Antarctica

The distribution and abundance of euphausiid larvae and salps was studied from samples collected in 2002 and 2006 from Prydz Bay, Antarctica. Larvae of Thysanoessa macrura and Euphausia superba were mainly distributed in the north of the continental shelf. T. macrura was more abundant and had a relatively wider distribution. In 2006, with ice having retreated and higher seawater temperatures and chlorophylla levels, E. superba and T. macrura occurred in higher abundances and at more mature developmental stages. Euphausia crystallorophias was mainly distributed in the neritic region. In 2002, with severe ice conditions in the neritic region, abundance of E. crystallorophias was only 95.6 ind · (1000m)-3. In 2006 when a polynya existed, the abundance of E. crystallorophias reached 43966.6 ind · (1000m)-3. The population mainly consisted of metanauplius (MN) and calyptopisI (CI). Salps, mostly Salpa thompsoni, had a low abundance in Prydz Bay. In 2002, S. thompsoni was only found at one station in the north of the bay with an abundance of 10 ind · (1000m)-3. In 2006, S. thompsoni was found at three stations located near the continental slope and average abundance reached 146.7 ind·(1000m)-3. Environmental factors, such as the timing of icemelt, polynya formation and food concentration appear to have a marked effect on the distribution and abundance of euphausiid larvae and salps

Variation in epibiotic bacteria on two squat lobster species of Munidopsidae

The relationships between epibiotic bacteria on deep-sea hosts and host lifestyle factors are of particular interest in the field of deep-sea chemoautotrophic environmental adaptations. The squat lobsters Shinkaia crosnieri and Munidopsis verrilli are both dominant species in cold-seep ecosystems, and they have different distributions and feeding behaviors. These species may have evolved to have distinct epibiotic microbiota. Here, we compared the epibiotic bacterial communities on the M. verrilli carapace (MVcarapace), S. crosnieri carapace (SCcarapace), and S. crosnieri ventral plumose setae (SCsetae). The epibiotic bacteria on SCsetae were dense and diverse and had a multi-layer configuration, while those on MVcarapace and SCcarapace were sparse and had a monolayer configuration. Chemoautotrophic bacteria had the highest relative abundance in all epibiotic bacterial communities. The relative abundance of amplicon sequence variant 3 (ASV3; unknown species in order Thiotrichales), which is associated with sulfide oxidation, was significantly higher in SCsetae than MVcarapace and SCcarapace. Thiotrichales species seemed to be specifically enriched on SCsetae, potentially due to the synthetic substrate supply, adhesion preference, and host behaviors. We hypothesize that the S. crosnieri episymbionts use chemical fluxes near cold seeps more efficiently, thereby supporting the host’s nutrient strategies, resulting in a different distribution of the two species of squat lobster