Productivity and Production: Biomass Ratios of Bivalve and Gastropod Populations in an Eastern Canadian Estuary

Abstract

In a narrow, shallow estuary on the east coast of Canada, the dominant intertidal invertebrates were bivalve and gastropod molluscs. On a sand flat Mya arenaria produced 11.6 g∙m⁻²∙yr⁻¹ flesh dry weight with a production:biomass ratio of 2.54, whereas Macoma balthica produced 1.93 g∙m⁻²∙yr⁻¹ with a P:B ratio of 1.53. On a Spartina marsh, Littorina saxatilis produced 3.25 g∙m⁻²∙yr⁻¹ with a P:B ratio of 4.11. Approximate P:B ratios were applied to biomass figures for four other species to give the following estimates of productivity: Mytilus edulis on Zostera beds 19.7 g∙m⁻²∙yr⁻¹ flesh dry weight; M. edulis on Spartina beds 3.5 g∙m⁻²∙yr⁻¹; Nassarius obsoletus 1.15 g∙m⁻²∙yr⁻¹; Melampus lineatus 1.1 g∙m⁻²∙yr⁻¹; Lacuna vincta 0.06 g∙m⁻²∙yr⁻¹. A total production of the molluscs in the estuary is estimated at 4.7% of the production of Spartina and Zostera (all measured in kcal). It is postulated that molluscs are the chief primary consumers in the inlet.