Lower Oceanic O2 and Higher Temperatures Will Lead to a Shrinking Habitable Ocean Range

by Wendy Noreña

The effects of oceanic dead zones and lower dissolved oxygen on marine populations are now generally common knowledge as media reports about fishery devastation and coastal habitat destruction have reached popular media. However, serious scientific inquiries into declining O2 in our oceans have moved beyond the macroscale of events like dead zones and have begun to focus on the day-to-day utilization and depletion of oceanic oxygen in the face of climate change. Deutsch et al. (2015) contribute to future oceanic warming predictions with a metabolic index that puts the combined effects of decreased oxygen and increased temperature into perspective. Using data on four extensively researched marine ectotherms, including an open water fish (Atlantic cod), a benthic crustacean (Atlantic rock crab), a subtropic fish (sharpsnout seabream), and a common eelpout, the researchers calculate a ratio that compares the, “maximum sustainable metabolic rate,” of an oceanic region or depth with the minimum metabolic rate needed for the survival of a defined species. Ultimately, the study finds that we can expect a decrease of 14 to 26% in the habitable ocean regions for the four species outlined in their research and that similar numbers could likely be found for any other species’ data put through their metabolic model. Continue reading

Mean Temperature of Catch Shows Impact of Ocean Warming on Fisheries

by Hannah Tannenbaum

Understanding the impact of climate change on marine fisheries viability has important implications for the sustainability of the industry. Cheung, Watson and Pauly (2013) collected catch and supplemental data, and computed mean temperature of catch, MTC from average inferred temperature of over 900 species of exploited fish weighted with their annual catch rates. MTC was inferred from modeled distributions for the years 1970 to 2006. It was shown that there is a positive relationship between increased rate of SST change and increases to MTC, and that global fisheries have responded with ‘tropicalization,’ shifts. Continue reading