title: Metabolic and physiological changes in Prymnesium parvum when grown under, and grazing on prey of, variable nitrogen:phosphorus stoichiometry.
abstract: Mixotrophy is found in almost all classes of phytoplankton in a wide range of aquatic habitats ranging from oligotrophic to eutrophic marine and freshwater systems. Few studies have addressed how the nutritional status of the predator and/or the prey affects mixotrophic metabolism despite the realization that mixotrophy is important ecologically. Laboratory experiments were conducted to examine changes in growth rates and physiological states of the toxic haptophyte Prymnesium parvum when fed Rhodomonas salina of varying nutritional status. Haemolytic activity of P. parvum and prey mortality of R. salina were also measured. P. parvum cultures grown to be comparatively low in nitrogen (low-N), phosphorus (low-P) or low in both nutrients (low-NP) were mixed with low-NP, low-N, and low-P R. salina in all possible combinations, i.e., a 3×3 factorial design. N deficiency was obtained in the low-N cultures, while true P deficiency may not have been obtained in the low-P cultures. Mortality rates of R. salina (both due to ingestion and/or cell rupture as a function of grazing or toxic effects) were higher when R. salina cells were low-P, N-rich, regardless of the nutritional state of P. parvum. Mortality rates were, however, directly related to the initial prey:predator cell ratios. On the other hand, growth of the predator was a function of nutritional status and a significant positive correlation was observed between growth rates of P. parvum and cell-specific depletion rates of N, whereas no such relationship was found between P. parvum growth rates and depletion rates of P. In addition, the greatest changes in chlorophyll content and stoichiometric ratios of P. parvum were observed in high N:P conditions. Therefore, P. parvum may show enhanced success under conditions of higher inorganic N:P, which are likely favored in the future due to increases in eutrophication and altered nutrient stoichiometry driven by anthropogenic nutrient loads that are increasingly enriched in N relative to P.
authors.affiliation: Department of Biology and Environmental Sciences, Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, 39231 Kalmar, Sweden. Electronic address: veronicalundgren82@gmail.com.
authors.forename: Veronica M
authors.initials: VM
authors.lastname: Lundgren
authors.affiliation: University of Maryland Center for Environmental Science, Horn Point Laboratory, P.O. Box 775, Cambridge, MD 21613, USA.
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Glibert
authors.affiliation: Department of Biology and Environmental Sciences, Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, 39231 Kalmar, Sweden; Lund University, Biological Institution, Aquatic Ecology, Box 118, 22100 Lund, Sweden; Everglades Wetland Research Park, 110 Kapnick Center, Florida Gulf Coast University, 4940 Bayshore Drive, Naples, FL 34112, USA.
authors.forename: Edna
authors.initials: E
authors.lastname: Granéli
authors.affiliation: Department of Biology and Environmental Sciences, Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, 39231 Kalmar, Sweden.
authors.forename: Nayani K
authors.initials: NK
authors.lastname: Vidyarathna
authors.affiliation: Department of Biology and Environmental Sciences, Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, 39231 Kalmar, Sweden; Interdepartmental Center for Research in Environmental Science (CIRSA), University of Bologna, Via S. Alberto 163, 48123 Ravenna, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Fiori
authors.affiliation: Department of Biology and Environmental Sciences, Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, 39231 Kalmar, Sweden; Research Center of Harmful Algae and Marine Biology and Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institutes, Jinan University, 510632 Guangzhou, China.
authors.forename: Linjian
authors.initials: L
authors.lastname: Ou
authors.affiliation: Centre for Sustainable Aquatic Research (CSAR), Swansea University, Swansea SA2 8PP, UK.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Flynn
authors.affiliation: Centre for Sustainable Aquatic Research (CSAR), Swansea University, Swansea SA2 8PP, UK.
authors.forename: Aditee
authors.initials: A
authors.lastname: Mitra
authors.affiliation: University of Maryland Center for Environmental Science, Horn Point Laboratory, P.O. Box 775, Cambridge, MD 21613, USA.
authors.forename: Diane K
authors.initials: DK
authors.lastname: Stoecker
authors.affiliation: Centre for Ocean Life, Marine Biological Section, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, Denmark.
authors.forename: Per J
authors.initials: PJ
authors.lastname: Hansen
mesh_terms: D002734:Chlorophyll / Q000032:analysis; D017753:Ecosystem; D058087:Haptophyta / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D009747:Nutritional Physiological Phenomena; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism*; D010839:Phytoplankton / Q000254:growth & development / Q000378:metabolism / Q000502:physiology
chemical_list: D002734:Chlorophyll; D010758:Phosphorus; D009584:Nitrogen
keywords: Mixotrophy; Nitrogen; Phosphorus; Prymnesium parvum; Variable stoichiometry