MEPS 582:105-120 (2017)  -  DOI: https://doi.org/10.3354/meps12328

Effect of green macroalgal blooms on the behavior, growth, and survival of cockles Clinocardium nuttallii in Pacific NW estuaries

Nathaniel S. Lewis1,*, Theodore H. DeWitt2

1ORISE Research Fellow, Pacific Coastal Ecology Branch, Western Ecology Division, US Environmental Protection Agency, Newport, OR 97365, USA
2Pacific Coastal Ecology Branch, Western Ecology Division, US Environmental Protection Agency, Newport, OR 97365, USA
*Corresponding author:

ABSTRACT: Nutrient over-enrichment can produce adverse ecological effects within coastal ecosystems and negatively impact the production of ecosystem goods and services. In small estuaries of the US Pacific Northwest, seasonal blooms of green macroalgae (GMA; family Ulvaceae) are primarily associated with natural nutrient input, rather than anthropogenic sources. This provided us a unique opportunity to investigate the effects of naturally stimulated macroalgal blooms on intertidal bivalves. Heart cockles Clinocardium nuttallii are an important species for shellfisheries in the region. In summer population surveys, we found that cockles emerged from the sediment with greater frequency as GMA biomass increased. Experimental manipulation of GMA biomass in the field showed that GMA elicited emergence, evoked above-ground lateral movement, inhibited shell growth, and increased mortality (by 34.0 ± 15.2%) in cockles. Laboratory experiments revealed that the interaction of a weighted barrier at the sediment surface and GMA presence elicited rapid emergence among cockles. Risk assessment of the emergence response in cockles showed that the in situ emergent population experienced 11.0 ± 8.0% mortality due to gull predation, while laboratory exposure to elevated temperatures (≥34°C) slowed valve-closure, inhibited reburial, and increased mortality, which could have translated to 7.1 ± 1.5% in situ mortality. We found that cockles avoided mortality due to burial below GMA mats by emerging from the sediment, but that behavior consequently put them at risk of mortality due to heat stress or gull predation. Regardless of nutrient source, our research showed that GMA blooms pose a threat to the survival of intertidal bivalves.


KEY WORDS: Bivalves · Ulvoid · Ecosystem services · Nutrient enrichment · Behavior · Intertidal · Emergence · Eutrophication


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Cite this article as: Lewis NS, DeWitt TH (2017) Effect of green macroalgal blooms on the behavior, growth, and survival of cockles Clinocardium nuttallii in Pacific NW estuaries. Mar Ecol Prog Ser 582:105-120. https://doi.org/10.3354/meps12328

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