Dinoflagellate vertical migration fuels an intense red tide

Abstract

Harmful algal blooms (HABs) are increasing globally, causing economic, human health, and ecosystem harm. In spite of the frequent occurrence of HABs, the mechanisms responsible for their exceptionally high biomass remain imperfectly understood. A 50-y-old hypothesis posits that some dense blooms derive from dinoflagellate motility: organisms swim upward during the day to photosynthesize and downward at night to access deep nutrients. This allows dinoflagellates to outgrow their nonmotile competitors. We tested this hypothesis with in situ data from an autonomous, ocean-wave-powered vertical profiling system. We showed that the dinoflagellate Lingulodinium polyedra ’s vertical migration led to depletion of deep nitrate during a 2020 red tide HAB event. Downward migration began at dusk, with the maximum migration depth determined by local nitrate concentrations. Losses of nitrate at depth were balanced by proportional increases in phytoplankton chlorophyll concentrations and suspended particle load, conclusively linking vertical migration to the access and assimilation of deep nitrate in the ocean environment. Vertical migration during the red tide created anomalous biogeochemical conditions compared to 70 y of climatological data, demonstrating the capacity of these events to temporarily reshape the coastal ocean’s ecosystem and biogeochemistry. Advances in the understanding of the physiological, behavioral, and metabolic dynamics of HAB-forming organisms from cutting-edge observational techniques will improve our ability to forecast HABs and mitigate their consequences in the future.

No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ13C) of shallow dwelling planktic foraminifera over the past 160 kyr

“…In order to facilitate calcification, G. ruber and T. sacculifer may actively influence the pH at the shell surface by seeking specific (optimum) light levels through vertical migration, thereby keeping the CIE constant over time. Vertical migration to optimise both nutrient uptake and light has been proposed to play an important role in phytoplankton by modelling (Wirtz et al, 2022), an effect which recently has been supported by field data (Zheng et al, 2023). We speculate similar behaviour could occur in the two planktic foraminifera species.…”

Patchiness of plankton communities at fronts explained by Lagrangian history of upwelled water parcels

“…Simultaneously measuring several physical and biogeochemical variables (including vertical currents, nutrient fluxes, growth and grazing rates, etc.) is a continuing challenge, but new technologies are developing to improve our measurements (Zheng et al, 2023).…”

Naturally and Anthropogenically Induced Lingulodinium polyedra Dinoflagellate Red Tides in the Galician Rias (NW Iberian Peninsula)

“…Harmful algal blooms (HABs) caused by dinoflagellates, although their causes are still poorly understood, have a great ecological impact on marine food webs due to the ability of dinoflagellates to produce different types of toxins, which can affect fish populations. For this reason, these events can have a considerable impact on local economies and health [ 5 , 6 , 7 , 8 ]. A distinctive bloom-forming species is the ecologically important Lingulodinium polyedra (Stein) Dodge (= Lingulodinium polyedrum (Stein) Dodge, Gonyalulax polyedra Stein).…”