Emergence of Anoxia in the California Current Large Marine Ecosystem

Abstract

Eastern boundary current systems are among the world's most productive large marine ecosystems. Because upwelling currents transport nutrient-rich but oxygen-depleted water onto shallow seas, large expanses of productive continental shelves can be vulnerable to the risk of extreme low-oxygen events. Here, we report the novel rise of water-column shelf anoxia in the northern California Current system, a large marine ecosystem with no previous record of such extreme oxygen deficits. The expansion of anoxia highlights the potential for rapid and discontinuous ecosystem change in productive coastal systems that sustain a major portion of the world's fisheries.

Chapter 1 Impacts of the Oceans on Climate Change

“…N 2 O production is enhanced in areas where oxygen levels are depleted and nitrate fuels denitrification. These conditions are combined in upwelling areas and it has been suggested that the global expansion of hypoxic/ anoxic zones (Chan et al, 2008) is leading to increased production of N 2 O and the accumulation of this radiatively active trace gas in the atmosphere (Naqvi et al, 2000).…”

Oceanography: Dead in the water

“…Starfish and mussels died, and rockfish and other mobile fish fled the hypoxic zone, which grew to 3,000 square kilometres (ref. 2).…”

Expansion of oxygen minimum zones may reduce available habitat for tropical pelagic fishes

“…When dissolved oxygen is minimized, widespread mortality 11,12 or avoidance 13 of affected areas can result. OMZs in the eastern tropical seas represent the largest contiguous areas of naturally occurring hypoxia 9 in the world's oceans.…”