Blooms of surf-zone diatoms along the coast of the Olympic Peninsula,Washington. XI. Regeneration of ammonium in the surf environment by the Pacific razor clam Siliqua patula

A 20 month field study was conducted on ammonium excretion rates of the Pacific razor clam Siliqua patula Dixon along the beaches of Washington State, USA. Excretion rates of all those nutrients likely to be regenerated in sufficient quantity to affect surf diatom growth were measured; ammonium appeared to be the most important metabolite. Excretion of ammonium by razor clams far exceeded that by other beach fauna. Ammonium excretion rates of razor clams were positively correlated with shell length, but no correlation between ammonium excretion rate and water temperature was evident. This may be an artifact or may represent some degree of seasonal acclimation of the species to temperature. Weight-specific ammonium excretion rates were negatively related to clam size, indicating a possible large (and unknown) contribution of regenerated ammonium by smaller clams in their first year of growth; smaller clams were rarely captured during this study.Contribution No. 1048 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA.