Spatial heterogeneity in gross biochemical composition and reproductive cycle of the Manila clam Ruditapes philippinarum in a macrotidal embayment of Korea

Abstract

To examine the influence of habitat disturbance by tideflat reclamation on phenology of Ruditapes philippinarum, seasonal variations in its condition, gross biochemical composition, and reproductive cycle were compared for a year between an adjacent site (GS) to the reclaimed flat and a reference site (HJ) of natural flat in Gomso Bay of Korea. Concentrations of chlorophyll a, seston, and food energy as food available to the clam were consistently higher at HJ than at GS. Condition, dry tissue weight, and energy reserves (proteins and carbohydrates) of the clams were much higher at HJ than at GS during spring−summer when fast growth and gametogenic development occur. Furthermore, clams gametogenic development in spring were advanced at HJ and thereby spawning delayed a month at GS. Our results suggested that the Manila clam in the altered habitats meet with nutritionally stressful environmental conditions that lead to lowered nutrient accumulation and changing reproductive cycle.