Friends and foes: symbiotic and algicidal bacterial influence on blooms.

Harmful Algal Blooms (HABs) of the toxigenic dinoflagellate (KB) are pivotal in structuring the ecosystem of the Gulf of Mexico (GoM), decimating coastal ecology, local economies, and human health. Bacterial communities associated with toxigenic phytoplankton species play an important role in influencing toxin production in the laboratory, supplying essential factors to phytoplankton and even killing blooming species. However, our knowledge of the prevalence of these mechanisms during HAB events is limited, especially for KB blooms.

In hot water: Interactions of temperature, nitrogen form and availability and photosynthetic and nitrogen uptake responses in natural Karenia brevis populations.

During 2020-2021, an unusually prolonged bloom of the toxigenic dinoflagellate Karenia brevis persisted for more than 12 months along the Gulf coast of Florida, resulting in severe environmental effects. Motivated by the possibility that unusual nutrient conditions existed during summer 2021, the short-term interactions of temperature, nitrogen (N) forms (ammonium (NH), nitrate (NO), and urea) and availability on photosynthesis-irradiance responses and N uptake rates were examined in summer 2021 and compared to such responses from the earlier winter. Winter samples were exposed to temperatures of 15, 20, 25, 30 °C while summer samples were incubated at 15, 25, 30, 33 °C, representing the maximum range the cells might experience throughout the water column due to daytime surface heating or extreme weather events.

Mixoplankton and mixotrophy: future research priorities.

Phago-mixotrophy, the combination of photoautotrophy and phagotrophy in mixoplankton, organisms that can combine both trophic strategies, have gained increasing attention over the past decade. It is now recognized that a substantial number of protistan plankton species engage in phago-mixotrophy to obtain nutrients for growth and reproduction under a range of environmental conditions. Unfortunately, our current understanding of mixoplankton in aquatic systems significantly lags behind our understanding of zooplankton and phytoplankton, limiting our ability to fully comprehend the role of mixoplankton (and phago-mixotrophy) in the plankton food web and biogeochemical cycling.

A three-dimensional mixotrophic model of Karlodinium veneficum blooms for a eutrophic estuary.

Blooms of dinoflagellate Karlodinium veneficum are widely distributed in estuarine and coastal waters and have been found to cause fish kills worldwide. K. veneficum has a mixed nutritional mode and relies on both photosynthesis and phagotrophy for growth; it is a mixotroph.

Seasonal gut contents of the eastern oyster, , in the Rhode River, Chesapeake Bay, USA: Growth, phytoplankton and signature pigment data.

A 2-year study was undertaken to understand feeding preferences of the eastern oyster when growing in conditions of eutrophication and variable flow. Oysters were suspended in the Rhode River, a tributary of Chesapeake Bay, Maryland, USA, and a subset of these oysters was collected monthly, measured in height to determine growth, and the phytoplankton in their gut were examined both microscopically and using indicator pigments and compared with phytoplankton abundance and composition in the water column. The data herein summarize the oyster growth and the gut contents with respect to phytoplankton cell numbers and composition and with respect to signature pigments.