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1. MurKy waters: modeling the succession from r to K strategists (diatoms to dinoflagellates) following a nutrient release from a mining facility in Florida

   https://doi.org/10.1002/lno.12420  

   Chen, Yuren; Li, Ming; Glibert, Patricia M.; Heil, Cynthia (October 2023, Limnology and Oceanography)

   Burford, Michele (Ed.)

   Abstract The impacts of pulsed nutrient injections or extreme runoff events on marine ecosystems are far less studied than those associated with long‐term eutrophication, particularly in regard to mechanisms regulating the response of plankton community structure. Over 800 million liters of nutrient‐rich water from a fertilizer mine were discharged over a 2‐week period into Tampa Bay, Florida, in 2021, providing a unique opportunity to document the plankton response. A 3D‐coupled hydrodynamic biogeochemical model was developed to investigate this response and to understand the observed succession of a large, short diatom bloom followed by a secondaryKarenia brevisbloom that lasted through the summer. The model reproduced the observed changes in nutrient concentration, total chlorophylla, and diatom andK. brevisbiomass in Tampa Bay. With a faster growth rate and spring temperature close to the optimal window of growth, diatoms had an initial competitive advantage, with 2/3 of the nutrient uptake due to ammonium and 1/3 due to nitrate. However, exhaustion of external nutrients led to the rapid decline of the diatom bloom, and the associated particular organic nitrogen sank onto the bay sediment. Enhanced sediment release of ammonium during the weeks following, and summer remineralization of dissolved organic nitrogen provided sufficient regenerated nitrogen to support slow‐growingK. brevisthat could capitalize on low nutrient conditions. Modeling analysis largely confirmed Margalef's conceptual model ofrtoK‐selected species succession and provided additional insights into nutrient cycling supporting the initial diatom bloom and the subsequent bloom of a slow‐growing harmful algal species. 

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2. Effect of salinity stress and nitrogen depletion on growth, morphology and toxin production of freshwater cyanobacterium Microcoleus anatoxicus Stancheva & Conklin

   Stancheva, R; Brown, S; Boyer, G; Wei, B; Goel, R; Henry, S; Kristan, N; Read, B (June 2024, Hydrobiologia)

   Cyanobacterium Microcoleus anatoxicus, isolated from a coastal stream in northern California, produces both anatoxin-a (ATX) and dihydroanatoxin- a (dhATX), responsible for dog deaths, but its environmental preferences are unknown. We tested the effect of environmentally relevant stressors, e.g., salinity enrichment and nitrogen (N) depletion, on mat formation and toxicity of M. anatoxicus during the stationary growth phase in culture. Microcoleus anatoxicus showed broad salinity tolerance and the potential to enter estuaries and produce toxins in mesohaline conditions. Maximum growth was observed in oligohaline waters with salinity of 4.6 ppt. Moderate salinity stress (up to 7.8 ppt) did not affect dhATX production significantly. In contrast, higher salinity above 9.3 ppt had a detrimental effect on cell growth and significantly suppressed dhATX production. Formation of a common polysaccharide sheath covering multiple filaments was characteristic with increased salinity and may provide protection against osmotic stress. Microcoleus anatoxicus grown for 40 days in N-depleted medium formed mats with significantly elevated dhATX and increased ATX concentrations. Phycobilisome degradation was a possible acclimation response to N-limitation, as indicated by distinctly keritomized and pale cells in these cultures. In both experiments, most of the anatoxins were extracellular,probably due to toxin leaking during the stationary growth phase. 

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3. Formation, Development, and Propagation of a Rare Coastal Coccolithophore Bloom

   https://doi.org/10.1029/2019JC015072  

   Matson, Paul G.; Washburn, Libe; Fields, Erik A.; Gotschalk, Chris; Ladd, Tanika M.; Siegel, David A.; Welch, Zoë S.; Iglesias‐Rodriguez, M. Debora (May 2019, Journal of Geophysical Research: Oceans)

   Abstract This study examines an unprecedented bloom ofEmiliania huxleyialong the California coast during the NE Pacific warm anomaly of 2014–2015. Observations of coccolithophore populations from microscopy and flow cytometry, surface current data derived from high‐frequency radar, and satellite ocean color imagery were used to track the population dynamics of the bloom in the Santa Barbara Channel. Results show a coastal bloom of mostlyE. huxleyithat reached cell concentrations up to 5.7 × 10⁶cells per liter and a maximum spatial extent of 1,220 km². We speculate that the rare cooccurrence of warm water, high water column stability, and an extensive preceding diatom bloom during the anomaly contributed to the development of this bloom. Flow cytometry measurements provided insight on the phases of bloom development (e.g., growth versus senescence) with calcified cells comprising up to 64% of particles containing chlorophyll a and detached‐coccolith:cell ratios ranging from 10 to >100. Lagrangian particle trajectories estimated during two nonoverlapping 48‐ and 72‐hr periods showed the changes in the surface structure of the bloom due to advection by surface currents and nonconservative biological and physical processes. Time rates of change of particulate inorganic carbon were estimated along particle trajectories, with rates ranging from −4 to 6 μmol·L⁻¹·day⁻¹. The approach presented here is likely to be useful for understanding the evolution of coastal phytoplankton bloom events in a general setting. 

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4. A Regional, Early Spring Bloom of Phaeocystis pouchetii on the New England Continental Shelf

   Smith, W.O. (January 2021, Journal of geophysical research)

   null (Ed.)

   The genus Phaeocystis is distributed globally and has considerable ecological, biogeochemical, and societal impacts. Understanding its distribution, growth and ecological impacts has been limited by lack of extensive observations on appropriate scales. In 2018, we investigated the biological dynamics of the New England continental shelf and encountered a substantial bloom of Phaeocystis pouchetii. Based on satellite imagery during January through April, the bloom extended over broad expanses of the shelf; furthermore, our observations demonstrated that it reached high biomass levels, with maximum chlorophyll concentrations exceeding 16 μg L−1 and particulate organic carbon levels > 95 μmol L−1. Initially, the bloom was largely confined to waters with temperatures <6°C, which in turn were mostly restricted to shallow areas near the coast. As the bloom progressed, it appeared to sink into the bottom boundary layer; however, enough light and nutrients were available for growth. The bloom was highly productive (net community production integrated through the mixed layer from stations within the bloom averaged 1.16 g C m−2 d−1) and reduced nutrient concentrations considerably. Long-term coastal observations suggest that Phaeocystis blooms occur sporadically in spring on Nantucket Shoals and presumably expand onto the continental shelf. Based on the distribution of Phaeocystis during our study, we suggest that it can have a significant impact on the overall productivity and ecology of the New England shelf during the winter/spring transition. 

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5. Genomic signatures of Lake Erie bacteria suggest interaction in the Microcystis phycosphere

   https://doi.org/10.1371/journal.pone.0257017  

   Hoke, Alexa K.; Reynoso, Guadalupe; Smith, Morgan R.; Gardner, Malia I.; Lockwood, Dominique J.; Gilbert, Naomi E.; Wilhelm, Steven W.; Becker, Isabella R.; Brennan, Grant J.; Crider, Katherine E.; et al (September 2021, PLOS ONE)

   Humbert, Jean-François (Ed.)

   Microbial interactions in harmful algal bloom (HAB) communities have been examined in marine systems, but are poorly studied in fresh waters. To investigate HAB-microbe interactions, we isolated bacteria with close associations to bloom-forming cyanobacteria, Microcystis spp., during a 2017 bloom in the western basin of Lake Erie. The genomes of five isolates ( Exiguobacterium sp. JMULE1, Enterobacter sp. JMULE2, Deinococcus sp. JMULE3, Paenibacillus sp. JMULE4, and Acidovorax sp. JMULE5.) were sequenced on a PacBio Sequel system. These genomes ranged in size from 3.1 Mbp ( Exiguobacterium sp. JMULE1) to 5.7 Mbp ( Enterobacter sp. JMULE2). The genomes were analyzed for genes relating to critical metabolic functions, including nitrogen reduction and carbon utilization. All five of the sequenced genomes contained genes that could be used in potential signaling and nutrient exchange between the bacteria and cyanobacteria such as Microcystis . Gene expression signatures of algal-derived carbon utilization for two isolates were identified in Microcystis blooms in Lake Erie and Lake Tai ( Taihu ) at low levels, suggesting these organisms are active and may have a functional role during Microcystis blooms in aggregates, but were largely missing from whole water samples. These findings build on the growing evidence that the bacterial microbiome associated with bloom-forming algae have the functional potential to contribute to nutrient exchange within bloom communities and interact with important bloom formers like Microcystis . 

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