Quantitative Response of Alexandrium catenella Cyst Dormancy to Cold Exposure

Fischer, Alexis D.; Brosnahan, Michael L.; Anderson, Donald M.

doi:10.1016/j.protis.2018.06.001

Cited by 27 publications

(37 citation statements)

References 54 publications

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“…These can survive in sediments of lakes and oceans for many years and even decades (Ribeiro et al, 2011). Their germination may be endogenously controlled (Fischer et al, 2018), but typically defined environmental settings, often representative of suitable growth conditions for the respective species (Rengefors & Anderson, 1998) trigger excystment. Germination may be highly synchronized, leading to excystment of the entire viable seed pool once the right trigger is present (Anderson & Rengefors, 2006;Genovesi et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Future temperature and salinity do not exert selection pressure on cyst germination of a toxic phytoplankton species

Jerney

Suikkanen

Lindehoff

et al. 2019

Ecology and Evolution

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Environmental conditions regulate the germination of phytoplankton resting stages. While some factors lead to synchronous germination, others stimulate germination of only a small fraction of the resting stages. This suggests that habitat filters may act on the germination level and thus affect selection of blooming strains. Benthic “seed banks” of the toxic dinoflagellate Alexandrium ostenfeldii from the Baltic Sea are genetically and phenotypically diverse, indicating a high potential for adaptation by selection on standing genetic variation. Here, we experimentally tested the role of climate‐related salinity and temperature as selection filters during germination and subsequent establishment of A. ostenfeldii strains. A representative resting cyst population was isolated from sediment samples, and germination and reciprocal transplantation experiments were carried out, including four treatments: Average present day germination conditions and three potential future conditions: high temperature, low salinity, and high temperature in combination with low salinity. We found that the final germination success of A. ostenfeldii resting cysts was unaffected by temperature and salinity in the range tested. A high germination success of more than 80% in all treatments indicates that strains are not selected by temperature and salinity during germination, but selection becomes more important shortly after germination, in the vegetative stage of the life cycle. Moreover, strains were not adapted to germination conditions. Instead, highly plastic responses occurred after transplantation and significantly higher growth rates were observed at higher temperature. High variability of strain‐specific responses has probably masked the overall effect of the treatments, highlighting the importance of testing the effect of environmental factors on many strains. It is likely that A. ostenfeldii populations can persist in the future, because suitable strains, which are able to germinate and grow well at potential future climate conditions, are part of the highly diverse cyst population. OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.c8c83nr .

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Section: Introductionmentioning

confidence: 99%

Future temperature and salinity do not exert selection pressure on cyst germination of a toxic phytoplankton species

Jerney

Suikkanen

Lindehoff

et al. 2019

Ecology and Evolution

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“…These findings suggest that release from dormancy was mediated by extended exposure to cool temperatures (in nature and in storage) rather than an internally controlled cycle and have important implications for applied work (e.g., predictive models of bloom dynamics). Fischer et al () similarly found cold conditioning to be an important predictor of dormancy release in temperate populations of Alexandrium catenella . Improving the time‐temperature thresholds beyond which P. bahamense cysts are released from dormancy could allow derivation of a simple yet reliable index for predicting germination each year, comparable to the “chilling unit” index proposed by Fischer et al ().…”

Section: Discussionmentioning

confidence: 98%

“…Fischer et al () similarly found cold conditioning to be an important predictor of dormancy release in temperate populations of Alexandrium catenella . Improving the time‐temperature thresholds beyond which P. bahamense cysts are released from dormancy could allow derivation of a simple yet reliable index for predicting germination each year, comparable to the “chilling unit” index proposed by Fischer et al ().…”

Section: Discussionmentioning

confidence: 98%

“…We also apply lessons from plant ecology to explore external controls of dormancy release and dormancy return. Externally induced secondary dormancy has been proposed as an important mechanism to explain observations of dormancy cycling in dinoflagellate resting cysts in nature (Rathaille and Raine ; Moore et al ; Fischer et al, ). Our findings provide an additional line of evidence for this mechanism by directly demonstrating secondary dormancy in response to an environmental exposure in a controlled experiment.…”

Section: Frequently Used Terms Related To Physiological Dormancy and mentioning

confidence: 99%

“…There has been less focus on externally mediated secondary dormancy in dinoflagellates, but recent studies have pointed to this phenomenon as an explanation for seasonal dormancy in shallow water Alexandrium spp. in Cork Harbour, Ireland (Rathaille and Raine 2011), in Puget Sound, Washington (Moore et al 2015), and in Nauset Marsh, Massachusetts (Fischer et al 2018 (Azanza et al 2018). The few studies that have investigated P. bahamense germination requirements have focused on the time required for cyst maturation in primary dormancy (Corrales et al 1995, Sakamoto et al 2009) and the environmental triggers for germination of nondormant cysts (Sakamoto et al 2009, Morquecho et al 2014, Lopez et al 2016.…”

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confidence: 99%

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Temperature mediates secondary dormancy in resting cysts ofPyrodinium bahamense(Dinophyceae)

Lopez

Karim

Murasko

et al. 2019

Journal of Phycology

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High‐biomass blooms of the toxic dinoflagellate Pyrodinium bahamense occur most summers in Tampa Bay, Florida, USA, posing a recurring threat to ecosystem health. Like many dinoflagellates, P. bahamense forms immobile resting cysts that can be deposited on the seafloor—creating a seed bank that can retain the organism within the ecosystem and initiate future blooms when cysts germinate. In this study, we examined changes in the dormancy status of cysts collected from Tampa Bay and applied lessons from plant ecology to explore dormancy controls. Pyrodinium bahamense cysts incubated immediately after field collection displayed a seasonal pattern in dormancy and germination that matched the pattern of cell abundance in the water column. Newly deposited (surface) cysts and older (buried) cysts exhibited similar germination patterns, suggesting that a common mechanism regulates dormancy expression in new and mature cysts. Extended cool‐ and warm‐temperature conditioning of field‐collected cysts altered the cycle of dormancy compared with that of cysts in nature, with the duration of cool temperature exposure being the best predictor of when cysts emerged from dormancy. Extended warm conditioning, on the other hand, elicited a return to dormancy, or secondary dormancy, in nondormant cysts. These results directly demonstrate environmental induction of secondary dormancy in dinoflagellates—a mechanism common and thoroughly documented in higher plants with seasonal growth cycles. Our findings support the hypothesis that a seasonal cycle in cyst germination drives P. bahamense bloom periodicity in Tampa Bay and point to environmentally induced secondary dormancy as an important regulatory factor of that cycle.

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