Cyst-forming dinoflagellates in a warming climate

Abstract

Many phytoplankton species, including many harmful algal bloom (HAB) species, survive long periods between blooms through formation of benthic resting stages. Because they are crucial to the persistence of these species and the initiation of new blooms, the physiology of benthic stages must be considered to accurately predict responses to climate warming and associated environmental changes. The benthic stages of dinoflagellates, called resting cysts, germinate in response to the combination of favorable temperature, oxygen-availability, and release from dormancy. The latter is a mechanism that prevents germination even when oxygen and temperature conditions are favorable. Here, evidence of temperature-mediated control of dormancy duration from the dinoflagellates Alexandrium catenella and Pyrodinium bahamense-two HAB species that cause paralytic shellfish poisoning (PSP)-is reviewed and presented alongside new evidence of complementary, temperature-based control of cyst quiescence (the state in which cysts germinate on exposure to favorable conditions). Interaction of the two temperature-based mechanisms with climate is explored through a simple model parameterized using results from recent experiments with A. catenella. Simulations demonstrate the importance of seasonal temperature cycles for the synchronization of cysts' release from dormancy and are consistent with biogeography-based inferences that A. catenella is more tolerant of warming in habitats that experience a larger range of seasonal temperature variation (i.e., have higher temperature seasonality). Temperature seasonality is much greater in shallow, long-residence time habitats than in deep, open-water ones. As warming shifts species' ranges, cyst beds may persist longer in more seasonally variable, shallow inshore habitats than in deep offshore ones, promoting HABs that are *

Predicting the Effects of Climate Change on the Occurrence of the Toxic Dinoflagellate Alexandrium catenella Along Canada’s East Coast

“…A. catenella is projected to bloom earlier in the season (May) and to remain active until September-October due to longer favorable conditions in the EGSL. Earlier blooming in phytoplankton has already been measured and verified in the North Atlantic (Barton et al, 2016;Gobler et al, 2017) and is predicted to continue during the 21st century (Brosnahan et al, 2020). In the mitigation scenario MPI-ESM-LR RCP 4.5, more risk days are predicted to take place through the entire May-October period.…”

“…Temperatures and salinity are already known to have direct effects on Alexandrium's growth (Bill et al, 2016;Brosnahan et al, 2020). Salinity, however, could fulfill multiple roles in our model as it is linked to a variety of different factors which are known to affect A. catenella bloom occurrence.…”

Interannual Variability in the Thermal Habitat of Alexandrium catenella in the Bay of Fundy and the Implications of Climate Change

“…The current forecast model for A. catenella distribution in the Gulf of Maine (Stock et al, 2005;Anderson et al, 2014) includes temperature in both physical and biological components (e.g., growth rates; He et al, 2008) as well as freshwater discharge in the physical component. Moreover, any responses of cysts germination to changes in temperature and its seasonality also play a role in the dynamics of A. catenella blooms in a warming climate (Brosnahan et al, 2020). Recently, Devred et al (2018) developed a remote sensing approach to early detection of A. catenella in the Bay of Fundy using climatological surface temperature values to determine detection thresholds for their model.…”

“…The response of HABs to climate change, however, extends beyond just growth rates and thermal response curves. Changes in other aspects of their physical environment (e.g., increased stratification, changes in the phenology and amount of precipitation and freshwater discharge) are also expected to affect HABs species (Hallegraeff, 2010) as well as their life cycle and cysts dynamics (Brosnahan et al, 2020). Understanding the present thermal habitat of HAB species and its trends, and how the physical structure of the environment impacts the development of blooms is a crucial aspect of predicting future scenarios.…”

First Application of IFCB High-Frequency Imaging-in-Flow Cytometry to Investigate Bloom-Forming Filamentous Cyanobacteria in the Baltic Sea

“…(Campbell et al, 2010(Campbell et al, , 2013Harred and Campbell, 2014). IFCB has proven its versatility by being applicable for detailed studies on life cycles and growth rate estimates, identifying parasitic infections and the ecological influence of these on the host species (Brosnahan et al, 2014(Brosnahan et al, , 2015(Brosnahan et al, , 2017(Brosnahan et al, , 2020Peacock et al, 2014) as well as detecting rare species and analyzing species morphology against phylogeny (Henrichs et al, 2011(Henrichs et al, , 2013.…”