Sea butterfly in the Limacina helicina species. Sampling sea butterflies in the species Limacina helicina off California, Washington, and Oregon in the summer of 2011, researchers found that over 50 percent of onshore sea butterflies suffered from 'severe dissolution damage'. Offshore, 24 percent of individuals showed such damage. Photo: Russ Hopcroft / University of Alaska, Fairbanks / NOAA

By Jeremy Hance
8 May 2014

(mongabay.com) – It could be the plot of a horror movie: humans wake up one day to discover that chemical changes in the atmosphere are dissolving away parts of their bodies. But for small marine life known as sea butterflies, or pteropods, this is what's happening off the West Cost of the U.S. Increased carbon in the ocean is melting away shells of sea butterflies, which are tiny marine snails that underpin much of the ocean's food chain, including prey for pink salmon, mackerel, and herring.

"We did not expect to see pteropods being affected to this extent in our coastal region for several decades," said William Peterson, Ph.D., an oceanographer at National Oceanic and Atmospheric Administration (NOAA)'s Northwest Fisheries Science Center who co-authored the findings in a paper for the journal, Proceedings of the Royal Society B.

Sampling sea butterflies in the species Limacina helicina off California, Washington, and Oregon in the summer of 2011, researchers found that over 50 percent of onshore sea butterflies suffered from "severe dissolution damage," according to the paper. Offshore, 24 percent of individuals showed such damage.

The shells of sea butterflies are dissolving due to increased acidification in the oceans caused by society's CO2 emissions. While emissions from burning coal, gas, and oil are pumped into the atmosphere, the oceans eventually soak up nearly a third of the global cumulative emissions. This increase in CO2 in the oceans leads to a decrease in the availability of calcium carbonate and its crystal form, aragonite, which sea butterflies use to make their shells. Many other key species require calcium carbonate, such as corals, crustaceans, mollusks, and some plankton species. [more]

Underwater horrors: shells of marine life melting off the coast of the U.S.


ABSTRACT: Few studies to date have demonstrated widespread biological impacts of ocean acidification (OA) under conditions currently found in the natural environment. From a combined survey of physical and chemical water properties and biological sampling along the Washington–Oregon–California coast in August 2011, we show that large portions of the shelf waters are corrosive to pteropods in the natural environment. We show a strong positive correlation between the proportion of pteropod individuals with severe shell dissolution damage and the percentage of undersaturated water in the top 100 m with respect to aragonite. We found 53% of onshore individuals and 24% of offshore individuals on average to have severe dissolution damage. Relative to pre-industrial CO2 concentrations, the extent of undersaturated waters in the top 100 m of the water column has increased over sixfold along the California Current Ecosystem (CCE). We estimate that the incidence of severe pteropod shell dissolution owing to anthropogenic OA has doubled in near shore habitats since pre-industrial conditions across this region and is on track to triple by 2050. These results demonstrate that habitat suitability for pteropods in the coastal CCE is declining. The observed impacts represent a baseline for future observations towards understanding broader scale OA effects.

Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem

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