Thursdays, 4:30–5:30 pm
6 January–10 March 2011
School of Aquatic & Fishery Sciences
102 Fishery Sciences (auditorium)
1122 NE Boat Street (map)
University of Washington
Reception follows each talk

For more information, contact:
Trevor Branch, 206-221-0776
tbranch@u.washington.edu
courses.washington.edu/susfish

Funding for the Series is generously
provided by Tanya Bevan, friends of Don
Bevan, the UW School of Aquatic and
Fishery Sciences, and NOAA's Alaska
Fisheries Science Center and
Northwest Fisheries Science Center.

Ocean Acidification: Effects on Fisheries and Oceans

10 Mar

Rod Wilson

Professor, Integrative Animal Physiology, College of Life & Environmental Sciences, University of Exeter, UK

Can Fish Fight Back? Carbonate Production in an Acidic Ocean

Abstract

The inorganic half of the marine carbon cycle is based on the biogenic precipitation of calcium carbonate (CaCO₃) in the process of calcification. This bio-mineral is used as skeletal material in a wide range of marine biota and has important implications for current ocean chemistry, as well as providing valuable geological information about historical climate change. The majority of oceanic production of calcium carbonate is conventionally attributed primarily to marine plankton (coccolithophores and foraminifera in particular). However, marine teleost fish also precipitate carbonates within their intestine and excrete these at remarkably high rates. This is a by-product of their osmoregulatory need to drink large volumes of sea water and precipitate the ingested calcium ions as calcium carbonate (in the mineral form “high Mg-calcite”) as it passes through the intestine. This plays important roles for the fish in a variety of physiological processes including salt and water balance, acid-base regulation and respiratory function. However, from an environmental perspective we have recently produced the first predictive model of global fish biomass and community structure and from this estimated that fish contribute between 3 and 45 % of the global surface production of marine calcium carbonate. Fish carbonates have generated further environmental interest as they have higher magnesium content than most biotic sources, which is likely to speed up their dissolution with depth. This may explain up to a quarter of the increase in total alkalinity within 1000 m of the ocean surface, a controversial phenomenon that has puzzled oceanographers for decades and which helps to replenish the surface ocean alkalinity and enhance the absorption of atmospheric CO₂.

Total carbonate production is linked to fish size (doubling for every 10-fold drop in body mass) and overall abundance. Fishing selectively removes larger fish so total carbonate production falls less than expected based on population biomass. However, importantly for conservation issues, modeling suggests that fish carbonate production falls rapidly at lower rates of fishing than those used as management targets for sustainable yield. The role of fish in ocean chemistry may be important to consider when assessing fishing impacts. Climate change complicates future predictions as the increases in temperature and CO₂ expected over the next century are predicted to substantially increase carbonate production by fish. This is in contrast to many other calcifying organisms, thus fish have the potential to become an even more important component of the inorganic carbon cycle in the future.

Bio

My research focuses upon the mechanisms by which animals maintain homeostasis in the face of environmental variability—in particular regarding ion, water and acid-base balance, respiratory gas exchange and metabolism and how these mechanisms are integrated to provide appropriate responses to environmental changes. My research embraces techniques ranging from molecular genetics to in vivo physiology and the behaviour of fish in the laboratory and in the wild. This multi-disciplinary emphasis aims to provide a more holistic appreciation of the homeostatic responses in complex multicellular organisms. The role of gut carbonate production in physiology is of particular interest together with the subsequent influence the excreted carbonates have on the global ocean system.

Readings

• Jennings S, Melin F, Blanchard JL, Forster RM, Dulvy NK, Wilson RW. (2008) Global-scale predictions of community and ecosystem properties from simple ecological theory. Proc. Roy. Soc. B – Biol. Sci. 275: 1375-1383.
• Wilson, RW, Millero, FJ, Taylor, JR, Walsh, PJ, Christensen, V, Jennings, S, Grosell, M. (2009). Contribution of fish to the marine inorganic carbon cycle. Science 323: 359-362.
• Jennings, S, Wilson, RW. (2009). Fishing impacts on the marine inorganic carbon cycle. J. Appl. Ecol. 46(5): 976-982. (doi: 10.1111/j.1365-2664.2009.01682.x).
• Wilson, RW, Wilson JM, Grosell M (2002) Intestinal bicarbonate secretion by marine teleost fish - why and how? Biochimica Biophysica Acta - Biomembranes 1566: 182-193.
• Perry, C.T., M.A. Salter, A.R. Harborne, S.F. Crowley, H.L. Jelks, and R.W. Wilson. 2010. Fish as major carbonate mud producers and missing components of the tropical carbonate factory. PNAS Early Edition.