Uploaded April 2020 | Updated September 2026, 51 minutes ago
Sean Anderson presents "Temporal dynamics of Phytoplankton Mortality in the Skidaway River Estuary (GA, USA)"
Abstract: The structure and function of marine microbial food webs is largely determined by the ways in which phytoplankton die, as these mortality processes can differentially influence carbon and nutrient cycles. Temporal shifts in mortality have often been overlooked, hindering our ability to identify drivers of plankton mortality or include plankton loss terms in ecosystem models. To assess temporal mortality dynamics, we performed a series of dilution experiments in the Skidaway River Estuary, measuring phytoplankton growth, microzooplankton grazing, and viral lysis rates at time scales commensurate with tidal (hourly) or seasonal (weekly) periods. Significant variability in grazing rates were detected between semidiurnal tides and seasons, with rates driven by changes in plankton community composition rather than environmental factors (e.g. temperature or chlorophyll). Given the inability to estimate bulk parasitic infection rates from the dilution method, we applied weekly 18S amplicon sequencing to identify temporal trends in the enigmatic parasite group, Syndiniales (Alveolata). Co-occurrence analysis was used to construct protist networks and assess parasite-host interactions. Syndiniales were temporally variable, with highest relative abundances (7-28%) in warmer months from June-October, compared to other times of the year (0.01-6%). Syndiniales taxa accounted for 20% of all interactions, were significantly correlated to a range of confirmed and putative hosts (dinoflagellates, ciliates, and diatoms), and exhibited a generalist interaction strategy. Findings of temporal variability in grazing rates and parasite-host interactions further emphasize the heterogeneous nature of coastal marine systems, with implications for accurate plankton monitoring and ecosystem modeling.
Sean Anderson presents "Temporal dynamics of Phytoplankton Mortality in the Skidaway River Estuary (GA, USA)"
Abstract: The structure and function of marine microbial food webs is largely determined by the ways in which phytoplankton die, as these mortality processes can differentially influence carbon and nutrient cycles. Temporal shifts in mortality have often been overlooked, hindering our ability to identify drivers of plankton mortality or include plankton loss terms in ecosystem models. To assess temporal mortality dynamics, we performed a series of dilution experiments in the Skidaway River Estuary, measuring phytoplankton growth, microzooplankton grazing, and viral lysis rates at time scales commensurate with tidal (hourly) or seasonal (weekly) periods. Significant variability in grazing rates were detected between semidiurnal tides and seasons, with rates driven by changes in plankton community composition rather than environmental factors (e.g. temperature or chlorophyll). Given the inability to estimate bulk parasitic infection rates from the dilution method, we applied weekly 18S amplicon sequencing to identify temporal trends in the enigmatic parasite group, Syndiniales (Alveolata). Co-occurrence analysis was used to construct protist networks and assess parasite-host interactions. Syndiniales were temporally variable, with highest relative abundances (7-28%) in warmer months from June-October, compared to other times of the year (0.01-6%). Syndiniales taxa accounted for 20% of all interactions, were significantly correlated to a range of confirmed and putative hosts (dinoflagellates, ciliates, and diatoms), and exhibited a generalist interaction strategy. Findings of temporal variability in grazing rates and parasite-host interactions further emphasize the heterogeneous nature of coastal marine systems, with implications for accurate plankton monitoring and ecosystem modeling.
