Importance of dynamics of acquired phototrophy amongst mixoplankton; a unique example of essential nutrient transmission in community ecology

Abstract Transfers of energy and nutrients from producers to consumers are fundamental to ecosystem structure and functioning. A common example is the transfer of essential amino acids and fatty acids, produced by phototrophs, up through successive trophic levels. A highly specialised example is the transmission of acquired phototrophy between certain plankton. There are > 250 species of marine plankton that exploit acquired phototrophy; the Teleaulax - Mesodinium - Dinophysis (TMD) trinity is the most studied complex. In the TMD-trinity, plastids and nuclear material produced by the cryptophyte Teleaulax are transferred during feeding to the ciliate, Mesodinium and these acquired plastids are subsequently transferred from Mesodinium to its predator, the dinoflagellate Dinophysis . These plastidic non-constitutive mixoplankton, Mesodinium and Dinophysis , are globally ubiquitous and ecologically important organisms. Mesodinium can form red-tide blooms, while Dinophysis spp. cause diarrhetic shellfish poisoning events and shellfisheries closures. However, very little is known about the impact of different environmental stressors on the transmissions of acquired phototrophy, the subsequent decay of that phototrophic potential over time, and the implications for community trophic dynamics. Here, for the first time, the implications of the transmission dynamics of acquired phototrophy for the success of the TMD-trinity were explored under different nitrogen and phosphorus (N:P) nutrient ratios and loadings (eutrophic, mesotrophic, oligotrophic). Using a multi-nutrient simulator, bloom dynamics were shown to be markedly different under these scenarios, highlighting the importance of variable stoichiometry in community ecology. Importantly, dynamics were sensitive to the longevity (half-life) of the acquired phototrophy (especially for Dinophysis at low nutrient high N:P), a feature for which appropriate empirical data are lacking. This work highlights the need to enhance our understanding about how environmental stressors arising from anthropogenic activities (including climate change) will impact transference of acquired phototrophy between trophic levels and thence marine biodiversity and ecosystem services.