Citation:

Grear, J. Predicting Effects of Coastal Acidification on Marine Bivalve Populations. IN: Fish and Shellfish Program Newsletter, U.S. EPA Office of Research and Development, Washington, DC, 3-4, (2016).

Impact/Purpose:

This summary article is for publication in EPA's Fish and Shellfish Program Newsletter, the target audience for which includes States, academics, territories, tribes, consultants, other federal agencies, plus others are on my email distribution list for the newsletter. The impact of the article is to inform this audience about ongoing research and an expected publication that they may wish to consider in their own activities.

Description:

The partial pressure of carbon dioxide (pCO2) is increasing in the oceans and causing changes in seawater pH commonly described as ocean or coastal acidification. It is now well-established that, when reproduced in laboratory experiments, these increases in pCO2 can reduce survival and growth of early life stage bivalves. However, the effects that these impairments would have on whole populations of bivalves are unknown. In this study, these laboratory responses were incorporated into field-parameterized population models to assess population-level sensitivities to acidification for two northeast bivalve species with different life histories: Mercenaria mercenaria (hard clam) and Argopecten irradians (bay scallop). The resulting models permitted translation of laboratory pCO2 response functions into population-level responses to examine population sensitivity to future pCO2 changes. Preliminary results from our models indicate that if the current M. mercenaria negative population growth rate was attributed to the effects of pCO2 on early life stages, the population would decline at a rate of 50% per ten years at 420 microatmospheres (µatm) pCO2. If the current population growth rate was attributed to other additive factors (e.g., harvest, harmful algal blooms), M. mercenaria populations were predicted to decline at a rate of 50% per ten years at the preliminary estimate of 1010 µatm pCO2. The estimated population growth rate was positive for A. irradians, but was predicted to become negative at ≥ 530 µatm pCO2, with a 50% decline per ten years at ≥ 610 µatm pCO2. Given the continual rise of atmospheric pCO2, mitigation of eutrophication-based pCO2 or other stressors is required for sustainable populations. This study demonstrates that elevated rates of early life stage mortality wrought by moderate levels of acidification are enough to produce significant declines in projected abundances and potentially hinder some bivalve restoration efforts. These results are described in a manuscript prepared in collaboration with scientists from Stony Brook University and Long Island University and are currently under review for publication in the peer-reviewed literature.

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