EFFECTS OF NUTRIENT LIMITATION ON MICROALGAL COMPOSITION AND NUTRITIONAL QUALITY TO A COPEPOD CONSUMER

Nutrient limitation structures the taxonomic composition, abundance, and physiology of producers, and consequently the prey abundance and quality available to consumers. While some types of marine microalgae are strictly autotrophic, others are able to ingest particles in a form of mixotrophy. It has been proposed that mixotrophs have more stable nutrient stoichiometry under variable/limiting nutrient conditions, which could make them a particularly valuable nutritional resource. We reared microalgal taxa under nutrient replete and nutrient limiting conditions and measured particle ingestion and biochemical composition. The chlorophyte Dunaliella sp. unexpectedly exhibited mixotrophy and maintained stable stoichiometry under low-nutrient conditions. Pyramimonas parkeae, Heterocapsa triquetra, Rhodomonas salina and Thalassiosira weissflogii exhibited more variable nutrient stoichiometry. These algal strains were tested as prey for the copepod Centropages typicus through multi-day feeding experiments with adult females. At high food levels (>400 ugC/L), most prey reared under nutrient-limited and -replete conditions supported similar levels of egg production by C. typicus. However, egg production decreased in copepods fed nutrient-limited diatoms (T. weissflogii) and increased in those fed nutrient-limited R. salina. Overall, our results show that even with high levels of food, C. typicus reproduction is sensitive to nutrient limitation of strictly autotrophic prey, but robust to moderate stoichiometric changes in potentially mixotrophic prey. 

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Ann Tarrant, Woods Hole Oceanographic Institution (atarrant@whoi.edu)

Authors:

Ann Tarrant, Woods Hole Oceanographic Institution  (atarrant@whoi.edu)

Philip Alatalo, Woods Hole Oceanographic Institution  (palatalo@whoi.edu)

Rebecca Gast, Woods Hole Oceanographic Institution  (rgast@whoi.edu)