MEPS 468:231-243 (2012)  -  DOI:

An oceanographic, meteorological, and biological ‘perfect storm’ yields a massive fish kill

Beth A. Stauffer1,3,*, Alyssa G. Gellene1, Astrid Schnetzer1,4, Erica L. Seubert1, Carl Oberg2, Gaurav S. Sukhatme2, David A. Caron1

1Department of Biological Sciences and 2Department of Computer Science, University of Southern California, Los Angeles, California 90089, USA
3Present address: Lamont-Doherty Earth Observatory at Columbia University, Biology and Paleo-Environment, Palisades, New York 10964, USA
4Present address: Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA

ABSTRACT: Mass mortality events are ephemeral phenomena in marine ecosystems resulting from anthropogenically enhanced and natural processes. A fish kill in King Harbor, Redondo Beach, California, USA, in March 2011 killed ~1.54 × 105 kg of fish and garnered international attention as a marine system out of balance. Here, we present data collected prior to, during, and following the event that describe the oceanographic conditions preceding the event, spatial extent of hypoxia (dissolved oxygen < 1.4 ml l−1), and subsequent recovery of the harbor. In situ sensors within the harbor revealed rapid decreases in dissolved oxygen in surface waters from 7 to 9 March 2011, coincident with the mortality event on 8 March. Continuous observations provided evidence that respiration of a large population of fish within the harbor, potentially exacerbated by an incursion of upwelled low-oxygen water, resulted in significant oxygen reduction in the harbor and ultimately caused mortality of the fish population. The hydrodynamically constrained northern basin transitioned to nearly anoxic conditions, while spatially variable hypoxia was observed throughout the harbor and adjacent bay for >10 d following the event. Initial recovery of dissolved oxygen in the harbor was facilitated by storm-mediated mixing. No connection was apparent between increased algal biomass or phycotoxins within the harbor and the mortality event, although the fish showed evidence of prior exposure to the algal neurotoxin domoic acid. Our findings underscore the essential role of ocean observing and rapid response in the study of these events and the role that oceanographic processes play in hypoxia-driven fish mortalities. Alterations in upwelling regimes as a consequence of climate change are likely to further increase the frequency and magnitude of upwelling-driven hypoxia and mortality events.

KEY WORDS: Fish kill · Hypoxia · Nearshore embayment · Upwelling · Mixing

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Cite this article as: Stauffer BA, Gellene AG, Schnetzer A, Seubert EL, Oberg C, Sukhatme GS, Caron DA (2012) An oceanographic, meteorological, and biological ‘perfect storm’ yields a massive fish kill. Mar Ecol Prog Ser 468:231-243.

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