Seasonal variations of allocation strategy in carbon, nitrogen and phosphorus among tissues of male Mytilus coruscus are regulated by the gametogenic cycle: a case study in a mariculture system

Abstract

This study examines the seasonal allocation strategy of carbon, nitrogen, and phosphorus in tissues of male Mytilus coruscus within a mariculture system at Gouqi Island, providing insights into the mussels' reproductive and nutritional adaptations. The reproductive cycle of mussels is bifurcated, with a resting phase in summer and active gametogenesis from autumn to spring. Digestive enzyme activity in mussels correlates negatively with food conditionality, especially when food is scarce in winter, enzyme activity is heightened to enhance nutrient extraction, whereas in summer, with an abundance of food, enzymatic activity is conserved for other physiological processes. This suggests an adaptive modulation to optimize energy allocation between growth, maintenance, and reproduction. Allometric growth analysis reveals that smaller mussels exhibit uniform nutrient allocation across tissues, focusing on somatic growth. In contrast, larger, mature mussels prioritize phosphorus utilization in gonads, indicative of reproductive investment. This shift aligns with the predictive adaptive response model, anticipating future reproductive demands by adjusting resource allocation. The study also identifies seasonal fluctuations in nutrient demand and allocation among tissues, with gonadal tissues showing preferential accumulation of nitrogen and phosphorus during mature phases. Although mussels preferentially allocate nutrients to the shell only in autumn, a consistent preferential accumulation of nitrogen and phosphorus to this critical structural component, highlighting the importance of these elements in biomineralization and shell maintenance. This research elucidates the complex interplay between environmental factors, physiological processes, and nutrient dynamics in male M. coruscus, and underscore the importance of considering seasonal variations in nutrient allocation for sustainable mariculture practices.