Project description:In this research we present a transcriptomics analysis of the physiological response of a marine calcifier, Strongylocentrotus purpuratus, to ocean acidification, a decline in ocean pH that results from the absorption of anthropogenic carbon dioxide (CO2). Larvae were raised from fertilization to prism stage in seawater with elevated CO2 conditions based upon IPCC emissions scenario B1 (540ppm CO2) and A1FI (1020ppm CO2).
Project description:Seamounts, often rising hundreds of metres above the surrounding seafloor, obstruct the flow of deep-ocean water. While the resultant entrainment of deep-water by seamounts is predicted from ocean circulation models, its empirical validation has been hampered by the large scale and slow rate of the interaction. To overcome these limitations we use the growth of planktonic bacteria to assess the interaction rate. The selected study site, Tropic Seamount, in the North-Eastern Atlantic represents the majority of isolated seamounts, which do not affect the surface ocean waters. We prove deep-water is entrained by the seamount by measuring 2.3 times higher bacterial concentrations in the seamount-associated or ‘sheath’ water than in deep-ocean water unaffected by seamounts. Genomic analyses of the dominant sheath-water bacteria confirm their planktonic origin, whilst proteomic analyses indicate their slow growth. According to our radiotracer experiments, the doubling time of sheath-water bacterioplankton is 1.5 years. Therefore, for bacterioplankton concentration to reach 2.3 times higher in the ambient seawater, the seamount would need to retain deep-ocean water for more than 3.5 years. We propose that turbulent mixing of the retained sheath-water could stimulate bacterioplankton growth by increasing the cell encounter rate with the ambient dissolved organic molecules. If some of these molecules chelate hydroxides of iron and manganese, bacterioplankton consumption of the organic chelators would result in precipitation of insoluble hydroxides. Hence precipitated hydroxides would form ferromanganese deposits as a result of the bacterioplankton-mediated deep-water seamount interaction.
Project description:In this research we present a transcriptomics analysis of the physiological response of a marine calcifier, Strongylocentrotus purpuratus, to ocean acidification, a decline in ocean pH that results from the absorption of anthropogenic carbon dioxide (CO2). Larvae were raised from fertilization to prism stage in seawater with elevated CO2 conditions based upon IPCC emissions scenario B1 (540ppm CO2) and A1FI (1020ppm CO2). Adult S. purpuratus were collected using SCUBA from Goleta Pier (Goleta,CA, USA) and maintained in flowing seawater tables at 15-16°C. Spawning was induced by coelomic injection of 0.5M KCl following standard methods (Strathmann 1987). Eggs were collected from 3 females and separately fertilized by sperm from a single male (i.e. all larvae were full or half-siblings). Each of the three replicate cultures were divided in three (nine cultures total) and held in 10L flow-through containers filled with seawater aerated through a side arm with commercially manufactured air containing three different pCO2: 380ppm CO2 (present day atmospheric CO2 level, pH 8.01 ± 0.01), 540ppm CO2, an optimistic atmospheric CO2 concentration predicted by the Intergovernmental Panel on Climate Change for 2100 (B1 scenario, pH 7.96 ± 0.01) and 1020ppm CO2 (A1FI scenario, pH 7.88 ± 0.01). Larvae were cultured at 15°C until prism stage (40h post-fertilization). At the 40 hour time point, a sample of 60,000 larvae was removed from each of the 9 cultures in the 380, 540 and 1020 ppm treatments and stored in 1 mL Trizol at -80 ºC for later RNA analysis. The larval cDNA sample from each replicate 540ppm CO2 culture was competitively hybridized against the 380ppm CO2 control culture from the same replicate female. Similarly, the larval cDNA sample from each replicate 1020ppm CO2 culture was competitively hybridized against the 380ppm CO2 control culture from the same replicate female. Using dye swaps of technical replicates, treatment effects could be estimated independently of dye effects.