Influence of diet on chitobiase-based production rates for the harpacticoid copepod Tigriopus californicus

摘要

The influence of diet on copepod production is important when examining energy transfer within marine food webs, yet a direct link between diet and copepod production is lacking. Recently, measurements of the crustacean moulting enzyme chitobiase have allowed for rapid estimates of production rates for zooplankton communities. We tested the sensitivity of this method as a tool for measuring the productivity response of copepods to different diets by rearing the harpacticoid splash-pool copepod, Tigriopus californicus, on single and mixed species phytoplankton diets. Chitobiase-based productivity measurements demonstrate that a single species algal diet of the diatom Thalassiosira weissflogii was the best food item for T. californicus. In contrast, the dinoflagellate Amphidinium carterae was likely toxic given that copepods reared on this diet spent more time in early developmental stages and ultimately failed to survive. Copepod production and daily growth rates of T. californicus were higher on the T. weissflogii and natural food assemblage diets compared with the A. carterae or mixed (A. carterae/T. weissflogii) diets. Our use of the chitobiase method in a lab setting demonstrates the potential utility and sensitivity of this approach for field studies examining the impact and significance of short-term shifts in food quality on entire crustacean zooplankton communities.