Effects Of 2 Bloom-Forming Dinoflagellates, Prorocentrum-Minimum And Gyrodinium-Uncatenum, On The Growth And Survival Of The Eastern Oyster, Crassostrea-Virginica (Gmelin 1791)

Laboratory experiments were conducted to investigate the effects of the dinoflagellates Prorocentrum minimum and Gyrodinium uncatenum on the growth and survival of juvenile eastern oysters, Crassostrea virginica. In separate experiments lasting 30 d and 18 d for P. minimum and G. uncatenum, respectively, the dinoflagellates were offered to the oysters in both unialgal and mixed diets (with the diatom Thalassiosira weisflogii). Eight diets were used in each experiment: (i) the dinoflagellate at bloom density, (ii) the dinoflagellate at 33% bloom density, (iii) the dinoflagellate at 5% bloom density, (iv-vi) the diatom at the above densities, (vii) 50% dinoflagellate bloom density + 50% diatom bloom density, and (viii) 5% dinoflagellate bloom density + 95% diatom bloom density. P. minimum at bloom density resulted in 100% mortality of juvenile oysters within 14 d and at 33% bloom density it resulted in 43% mortality within 22 d. Diets containing 5% P. minimum density did not cause mortality and supported good shell growth. No mortality was observed among oysters fed G. uncatenum and diets which included this dinoflagellate resulted in significantly greater growth than diets of the diatom T. weisflogii

Climate Change and the Potential Spreading of Marine Mucilage and Microbial Pathogens in the Mediterranean Sea

Background: Marine snow (small amorphous aggregates with colloidal properties) is present in all oceans of the world. Surface water warming and the consequent increase of water column stability can favour the coalescence of marine snow into marine mucilage, large marine aggregates representing an ephemeral and extreme habitat. Marine mucilage characterize aquatic systems with altered environmental conditions. Methodology/Principal Findings: We investigated, by means of molecular techniques, viruses and prokaryotes within the mucilage and in surrounding seawater to examine the potential of mucilage to host new microbial diversity and/or spread marine diseases. We found that marine mucilage contained a large and unexpectedly exclusive microbial biodiversity and hosted pathogenic species that were absent in surrounding seawater. We also investigated the relationship between climate change and the frequency of mucilage in the Mediterranean Sea over the last 200 years and found that the number of mucilage outbreaks increased almost exponentially in the last 20 years. The increasing frequency of mucilage outbreaks is closely associated with the temperature anomalies. Conclusions/Significance: We conclude that the spreading of mucilage in the Mediterranean Sea is linked to climate-driven sea surface warming. The mucilage can act as a controlling factor of microbial diversity across wide oceanic regions and could have the potential to act as a carrier of specific microorganisms, thereby increasing the spread of pathogenic bacteria