Macroalgae and Bivalve Interactions: A Review of Trophic and Feeding Studies to Assess the Contribution of Macroalgal Detritus to Bivalves

ABSTRACT

There is growing interest in the co‐culture of macroalgae and filter‐feeding bivalves due to anticipated trophic benefits that may enhance the productivity of both organisms. Detritus from cultured macroalgae has the potential to supplement bivalve diets, yet few studies have directly examined this relationship in co‐culture systems. This review synthesizes findings from over 70 studies encompassing a broad range of macroalgae and bivalve species to assess the potential for macroalgal material to contribute to bivalve nutrition. No consistent patterns of macroalgal utilization by bivalves were found across regions, seasons, bivalve taxa, or macroalgal groups. In situ trophic assessments using stable isotopes and fatty acids produced divergent estimates of macroalgal dietary contributions, averaging 23.7% and 6.1%, respectively. Feeding studies of bivalves fed various forms of macroalgal material found that while relatively high rates of assimilation efficiency were measured for some bivalve species, the generally poor performance of bivalves in longer term feeding studies strongly indicated that the nutritional composition of the macroalgal material is insufficient, and/or that the macroalgal material contains compounds that actively inhibit bivalve growth. The majority of feeding studies found that regardless of the diet preparation method or species of macroalgae used, bivalve growth was reduced when macroalgae was incorporated at rates higher than a 25% replacement of feed dry weight. Overall, the findings point toward a generally limited potential for filter feeding bivalves to benefit significantly from co‐culture with macroalgae, although specific pairing of macroalgae and bivalve species may derive greater advantage from co‐culture.