Red waters of Myrionecta rubra are biogeochemical hotspots for the Columbia River estuary with impacts on primary/secondary productions and nutrient cycles

Biogeochemical, microscopy, physiological and molecular data collected in the Columbia River estuary during the 2007-2010 Myrionecta rubra red tides demonstrated important biogeochemical impacts on estuarine water containing cells of this photosynthetic ciliate. M. rubra blooms affected the estuarine nutrient cycles being associated with high and low concentrations of organic nutrients and inorganic nitrogen, respectively. These blooms also altered the energy transfer pattern in patches of the Columbia River estuary that contain the ciliate by creating areas characterized by high primary production and large amount of fresh in situ particulate organic matter, therefore shifting the trophic status in patches of the estuary from net heterotrophy towards autotrophy. The pelagic estuarine bacterial community structure of these patches were however not affected, but red tides of the ciliate do offer a strong link between autotrophic and heterotrophic processes since they were associated with elevated dissolved organic matter and microbial secondary production.