ALBERT

Description: [1]  In recent decades, it has been found useful to partition the pelagic environment using the concept of biogeochemical provinces, or BGCPs, within each of which it is assumed that environmental conditions are distinguishable and unique at global scale. The boundaries between provinces respond to features of physical oceanography and, ideally, should follow seasonal and inter-annual changes in ocean dynamics. But this ideal has not been fulfilled except for small regions of the oceans. Moreover, BGCPs have been used only as static entities having boundaries that were originally established to compute global primary production. In the present study, a new statistical methodology based on non-parametric procedures is implemented to capture the environmental characteristics within 56 BGCPs. Four main environmental parameters (bathymetry, chlorophyll-a concentration, surface temperature and salinity) are used to infer the spatial distribution of each BGCP over 1997–2007. The resulting dynamic partition allows us to integrate changes in the distribution of BGCPs at seasonal and inter-annual timescales, and so introduces the possibility of detecting spatial shifts in environmental conditions.

Description: This study examines the combined contributions of climate change and fishing to the risk of impacts of 825 species of exploited fishes, and the scope for climate‐risk reduction from fisheries management. We show that areas with more at‐risk species to climate change are in tropical and subtropical oceans, while those that are at risk to fishing are distributed more broadly, with higher concentration of at‐risk species in North Atlantic and South Pacific Ocean. This study highlights the substantial opportunities for climate‐risk reduction through effective fisheries management. Abstract Risk of impact of marine fishes to fishing and climate change (including ocean acidification) depend on the species’ ecological and biological characteristics, as well as their exposure to over‐exploitation and climate hazards. These human‐induced hazards should be considered concurrently in conservation risk assessment. In this study, we aim to examine the combined contributions of climate change and fishing to the risk of impacts of exploited fishes, and the scope for climate‐risk reduction from fisheries management. We combine fuzzy logic expert system with species distribution modeling to assess the extinction risks of climate and fishing impacts of 825 exploited marine fish species across the global ocean. We compare our calculated risk index with extinction risk of marine species assessed by the International Union for Conservation of Nature (IUCN). Our results show that 60% (499 species) of the assessed species are projected to experience very high risk from both overfishing and climate change under a “business‐as‐usual” scenario (RCP 8.5 with current status of fisheries) by 2050. The risk index is significantly and positively related to level of IUCN extinction risk (ordinal logistic regression, p 〈 0.0001). Furthermore, the regression model predicts species with very high risk index would have at least one in five (〉20%) chance of having high extinction risk in the next few decades (equivalent to the IUCN categories of vulnerable, endangered or critically endangered). Areas with more at‐risk species to climate change are in tropical and subtropical oceans, while those that are at risk to fishing are distributed more broadly, with higher concentration of at‐risk species in North Atlantic and South Pacific Ocean. The number of species with high extinction risk would decrease by 63% under the sustainable fisheries‐low emission scenario relative to the “business‐as‐usual” scenario. This study highlights the substantial opportunities for climate‐risk reduction through effective fisheries management.

Description: The “biological carbon pump” causes carbon sequestration in deep waters by downward transfer of organic matter, mostly as particles. This mechanism depends to a great extent on the uptake of CO 2 by marine plankton in surface waters, and subsequent sinking of particulate organic carbon (POC) through the water column. Most of the sinking POC is remineralized during its downward transit and modest changes in remineralization have substantial feedbacks on atmospheric CO 2 concentrations, but little is known about global variability in remineralization. Here we assess this variability based on modern underwater particle imaging combined with field POC flux data, and discuss the potential sources of variations. We show a significant relationship between remineralization and the size structure of the phytoplankton assemblage. We obtain the first regionalized estimates of remineralization in biogeochemical provinces, where these estimates range between -50 and +100% of the commonly used globally uniform remineralization value. We apply the regionalized values to satellite-derived estimates of upper ocean POC export to calculate regionalized and ocean-wide deep carbon fluxes and sequestration. The resulting value of global organic carbon sequestration at 2000 m is 0.33 Pg C y -1 , and 0.72 Pg C y -1 at the depth of the top of the permanent pycnocline, which is up to 3 times higher than the value resulting from the commonly-used approach based on uniform remineralization and constant sequestration depth. These results stress that variable remineralization length scale and sequestration depth should be used to model ocean carbon sequestration and feedbacks on the atmosphere.