Composition of particulate matter in the neutrally buoyant plumes of the TAG and Broken Spur Hydrothermal Fields

This publication considers data on aquatic anomalies (hydrothermal plumes) in the areas of 26° and 29°N of the Mid-Atlantic Ridge (MAR). Mass of hydrothermal iron supply and intensity of iron sedimentation onto the bottom were estimated by means of sediment traps. It was found that the plume of the TAG hydrothermal vent 6 km**3 in volume contained about 67 tons of particulate Fe; the plume of the Broken Spur field (up to 8.24 km**3 in volume) contained 23.5 tons of particulate Fe or less because of its lower concentration. Data on sediment matter fluxes showed that 0.3-0.5% of hydrothermal iron was precipitated immediately from the neutrally buoyant plume onto the bottom; the bulk of iron was dissipated into environment. From dimensions of the plumes, flow dynamics, iron concentrations in the plumes, and amounts of iron supplied by hydrothermal vents, it was found that resident time of the plumes considered was from 5 to 10 days.

Ocean acidification weakens the immune response of blood clam through hampering the NF-kappa beta and toll-like receptor pathways

The impact of pCO2 driven ocean acidification on marine bivalve immunity remains poorly understood. To date, this impact has only been investigated in a few bivalve species and the underlying molecular mechanism remains unknown. In the present study, the effects of the realistic future ocean pCO2 levels (pH at 8.1, 7.8, and 7.4) on the total number of haemocyte cells (THC), phagocytosis status, blood cell types composition, and expression levels of twelve genes from the NF-kappa beta signaling and toll-like receptor pathways of a typical bottom burrowing bivalve, blood clam (Tegillarca granosa), were investigated. The results obtained showed that while both THC number and phagocytosis frequency were significantly reduced, the percentage of red and basophil granulocytes were significantly decreased and increased, respectively, upon exposure to elevated pCO2. In addition, exposure to pCO2 acidified seawater generally led to a significant down-regulation in the inducer and key response genes of NF-kappa beta signaling and toll-like receptor pathways. The results of the present study revealed that ocean acidification may hamper immune responses of the bivalve T. granosa which subsequently render individuals more susceptible to pathogens attacks such as those from virus and bacteria.