Physiological energetics of juvenile clams Ruditapes decussatus in a high CO2 coastal ocean

Effects of coastal ocean acidification, other than calcification, were tested on juvenile clams Ruditapes decussatus during a controlled CO2 perturbation experiment. The carbonate chemistry of natural (control) seawater was manipulated by injecting CO2 to attain 2 reduced pH levels (-0.4 and -0.7 pH units) as compared with the control seawater. After 87 d of exposure, we found that the acidification conditions tested in this experiment significantly reduced the clearance, ingestion and respiration rates, and increased the ammonia excretion rate of R. decussatus seeds. Reduced ingestion combined with increased excretion is generally associated with a reduced energy input, which will likely contribute to a slower growth of the clams in a future high CO2 coastal ocean. These results emphasize the need for management policies to mitigate the adverse effects of global change on aquaculture, which is an economically relevant activity in most coastal areas worldwide.Regional Ministry of Innovation and Industry of the Galician Government [08MDS018402PR]; Italian Ministry for Environment, Land and Sea; Foundation for Science and Technology of Portugal [ERA-CIRCLE/0004/2007]; European Commissio

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, Azores-I

Temperate, transitional and subtropical waters of the remote Azores Front region east of Azores (24-40°N, 22-32°W) were sampled during three cruises conducted under increasing stratification conditions (April 1999, May 1997 and August 1998). Despite the temporal increase of surface temperature (by 5 °C) and stratification (by 2.1 1/min**2), as well as the thermocline shoaling (by ~15 m), dissolved organic carbon (DOC) and nitrogen (DON) in the surface layer were not significantly different for the early spring, late spring and summer periods, with average concentrations of 69±2 µM-C and 5.2±0.4 µM-N, respectively. The surface excess of semi-labile DOC, compared with the baseline DOC concentration in the deep ocean (47±2 µM-C), represents 33% of the bulk DOC concentration and as much as 85% of the TOC (=POC+DOC) excess. When compared with the winter baseline (56±2 µM-C), the seasonal surface DOC excess is 20% of the bulk DOC concentration and 87% of the seasonal TOC excess. These results confirm the major role played by DOC in the carbon cycle of surface waters of the Azores Front region. The total amount of bioreactive DOC transported from the temperate to the subtropical North Atlantic by the Ekman flux between March and December represents only ~15% of the average annual primary production, and ~15% and ~30% of the measured sinking POC flux+vertical DOC eddy diffusion during early spring and summer, respectively. Vertical eddy diffusion is 35% and 2% of the spring and summer sinking POC flux, respectively. On the other hand, DOC only contributes 13% to the local oxidation of organic matter in subsurface waters (between the pycnocline and 500 m) of the study region

Seawater carbonate chemistry and physiological energetics of juvenile clams Ruditapes decussatus

Effects of coastal ocean acidification, other than calcification, were tested on juvenile clams (Ruditapes decussatus) during a controlled CO2 perturbation experiment. The carbonate chemistry of natural (control) seawater was manipulated by injecting CO2 to attain two reduced pH levels: -0.4 and -0.7 pH units as compared with the control seawater. After 87 days of exposure, we found that the acidification conditions tested in this experiment significantly reduced the clearance, ingestion and respiration rates, and increased the ammonia excretion rate of R. decussatus seeds. Reduced ingestion combined with increased excretion is generally associated with a reduced energy input, which will likely contribute to a slower growth of the clams in a future high CO2 coastal ocean. These results emphasize the need for management policies to mitigate the adverse effects of global change on aquaculture, which is an economically relevant activity in most coastal areas worldwide

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, Bransfield and Gerlache Straits

During FRUELA'95 cruise, seawater samples were collected at the Bransfield and Gerlache Straits for the analysis of dissolved organic carbon (DOC) profiles throughout the water column. An excess of DOC probably derived from phytogenic material was observed in the upper mixed layer (UML; average: +22±13 µmol C/l), compared to the constant concentration of refractory DOC below 400 m (44±4 µmol C/l). The average excess DOC concentration was higher than the particulate organic carbon concentration indicating the major contribution of DOC to carbon export in this area. However, large spatial variability of DOC in the upper mixed layer (52-102 µmol C/l) was observed: excess DOC contributed from 15% to 57% to the actual DOC concentration. Maximum average DOC concentrations in the UML were recorded in the Gerlache Strait (71 µmol C/l) and in the Gerlache-Bransfield confluence (80 µmol C/l), whereas minimum values were recorded in the Bransfield Strait (61 µmol C/l). Several shelf and slope stations showed a slight increase of DOC (5-10 µmol C/l) in the deep layer which might be related to organic matter release from the underlying sediments. Considering the net DOC release from phytoplankton, the low bacterial biomass and the reduced vertical DOC export, the DOC excess could build up in about 6 days for most of the sampling stations. The probable fate of the DOC excess is the eastwards horizontal transport by the Bransfield Current out of the study area

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, WOCE14

Total organic carbon (TOC) samples were collected at 6 stations spaced ~800 km apart in the eastern South Atlantic, from the Equator to 45°S along 9°W. Analyses were performed by high temperature catalytic oxidation (HTCO) in the base laboratory. Despite the complex advection and mixing patterns of North Atlantic and Antarctic waters with extremely different degrees of ventilation, TOC levels below 500 m are quasi-constant at 55±3 µmol C/l, pointing to the refractory nature of deep-water TOC. On the other hand, a TOC excess from 25 to 38 g C/m**2 is observed in the upper 100 m of the permanently stratified nutrient-depleted Equatorial, Subequatorial and Subtropical upper ocean, where vertical turbulent diffusion is largely prevented. Conversely, TOC levels in the nutrient-rich upper layer of the Subantarctic Front only exceeds 9 g C/m**2 the deep-water baseline. As much as 70% of the TOC variability in the upper 500 m is due to simple mixing of reactive TOC formed in the surface layer and refractory TOC in deep ocean waters, with a minor contribution (13%) to oxygen consumption in the prominent subsurface AOU maximum at 200-400 m depth

Water mass proportions, hydrographic and biogeochemical data below 1000 dbar along the GOSHIP A16N&S 2013 sections

Database including the hydrographic and biogeochemical data collected along the A16N&S, within the GO-SHIP program in 2013. The database also includes the water mass proportions calculated using an OMP analysis. This is the database that was used in the paper "Net additions of recalcitrant dissolved organic carbon in the deep Atlantic Ocean", submitted to Global Biogeochemical Cycles

Optimum Multiparameter Analysis for the Atlantic Ocean focused on dissolved organic carbon

Optimum Multiparameter Model in Matlab code to solve the mixing of water masses in the North and South Atlantic ocean based on GOSHIP cruises with available Dissolved Organic Carbon (DOC) data. Data below 250 dbar and colder than 14ºC are considered. The scripts solve the mixing of central, intermediate, deep and bottom waters crossed by the GOSHIP lines (A22-2012, A20-2012, A13.5-2010, A16N-2013, A16S-2013). INPUT variables are the comprised within a matlab file (OMP_ATL_DOM.mat) containing hydrographic and biogeochemical data as provided in the OCADS repository for Repeat Hydrography. The OUTPUT is generated in the file OMP_RESULTS.xlsx containing self explaining names of the output variables. A detailed explanation of the OMP settings, constraints and results to analyse and check is given in the linked Global Biogeochemical Cycles manuscript. To inititate the OMP analysis just run "Megaprograma.m", the analysis will start and when ending the results will appear in the xlsx file

Seawater carbonate chemistry, biomass and metabolic rates (leucine incorporation, CO2 fixation and respiration) of Rhodobacteraceae (strain MED165) and Flavobacteriaceae (strain MED217) in a laboratory experiment

Experimental results related to the effects of ocean acidification on planktonic marine microbes are still rather inconsistent and occasionally contradictory. Moreover, laboratory or field experiments that address the effects of changes in CO2 concentrations on heterotrophic microbes are very scarce, despite the major role of these organisms in the marine carbon cycle. We tested the direct effect of an elevated CO2 concentration (1000 ppmv) on the biomass and metabolic rates (leucine incorporation, CO2 fixation and respiration) of 2 isolates belonging to 2 relevant marine bacterial families, Rhodobacteraceae (strain MED165) and Flavobacteriaceae (strain MED217). Our results demonstrate that, contrary to some expectations, high pCO2 did not negatively affect bacterial growth but increased growth efficiency in the case of MED217. The elevated partial pressure of CO2 (pCO2) caused, in both cases, higher rates of CO2 fixation in the dissolved fraction and, in the case of MED217, lower respiration rates. Both responses would tend to increase the pH of seawater acting as a negative feedback between elevated atmospheric CO2 concentrations and ocean acidification