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1. Evidence for massive and recurrent toxic blooms of Alexandrium catenella in the Alaskan Arctic

   https://doi.org/10.1073/pnas.2107387118  

   Anderson, Donald M. ; Fachon, Evangeline ; Pickart, Robert S. ; Lin, Peigen ; Fischer, Alexis D. ; Richlen, Mindy L. ; Uva, Victoria ; Brosnahan, Michael L. ; McRaven, Leah ; Bahr, Frank ; et al ( October 2021 , Proceedings of the National Academy of Sciences)

   Among the organisms that spread into and flourish in Arctic waters with rising temperatures and sea ice loss are toxic algae, a group of harmful algal bloom species that produce potent biotoxins. Alexandrium catenella , a cyst-forming dinoflagellate that causes paralytic shellfish poisoning worldwide, has been a significant threat to human health in southeastern Alaska for centuries. It is known to be transported into Arctic regions in waters transiting northward through the Bering Strait, yet there is little recognition of this organism as a human health concern north of the Strait. Here, we describe an exceptionally large A. catenella benthic cyst bed and hydrographic conditions across the Chukchi Sea that support germination and development of recurrent, locally originating and self-seeding blooms. Two prominent cyst accumulation zones result from deposition promoted by weak circulation. Cyst concentrations are among the highest reported globally for this species, and the cyst bed is at least 6× larger in area than any other. These extraordinary accumulations are attributed to repeated inputs from advected southern blooms and to localized cyst formation and deposition. Over the past two decades, warming has likely increased the magnitude of the germination flux twofold and advanced the timing of cell inoculation into the euphotic zone by 20 d. Conditions are also now favorable for bloom development in surface waters. The region is poised to support annually recurrent A. catenella blooms that are massive in scale, posing a significant and worrisome threat to public and ecosystem health in Alaskan Arctic communities where economies are subsistence based. 

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2. Harmful Algal Blooms in the Alaskan Arctic: An Emerging Threat as the Ocean Warms

   https://doi.org/10.5670/oceanog.2022.121  

   Anderson, Donald ; Fachon, Evangeline ; Hubbard, Katherine ; Lefebvre, Kathi ; Lin, Peigen ; Pickart, Robert ; Richlen, Mindy ; Sheffield, Gay ; Van Hemert, Caroline ( January 2022 , Oceanography)

   Harmful algal blooms (HABs) present an emerging threat to human and ecosystem health in the Alaskan Arctic. Two HAB toxins are of concern in the region: saxitoxins (STXs), a family of compounds produced by the dinoflagellate Alexandrium catenella, and domoic acid (DA), produced by multiple species in the diatom genus Pseudo-nitzschia. These potent neurotoxins cause paralytic and amnesic shellfish poisoning, respectively, in humans, and can accumulate in marine organisms through food web transfer, causing illness and mortality among a suite of wildlife species. With pronounced warming in the Arctic, along with enhanced transport of cells from southern waters, there is significant potential for more frequent and larger HABs of both types. STXs and DA have been detected in the tissues of a range of marine organisms in the region, many of which are important food resources for local residents. The unique nature of the Alaskan Arctic, including difficult logistical access, lack of response infrastructure, and reliance of coastal populations on the noncommercial acquisition of marine resources for nutritional, cultural, and economic well-being, poses urgent and significant challenges as this region warms and the potential for impacts from HABs expands. 

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3. Temperature Affects the Biological Control of Dinoflagellates by the Generalist Parasitoid Parvilucifera rostrata

   https://doi.org/10.3390/microorganisms10020385  

   Schmitt, Matthew ; Telusma, Aaron ; Bigeard, Estelle ; Guillou, Laure ; Alves-de-Souza, Catharina ( February 2022 , Microorganisms)

   The increase in emerging harmful algal blooms in the last decades has led to an extensive concern in understanding the mechanisms behind these events. In this paper, we assessed the growth of two blooming dinoflagellates (Alexandrium minutum and Heterocapsa triquetra) and their susceptibility to infection by the generalist parasitoid Parvilucifera rostrata under a temperature gradient. The growth of the two dinoflagellates differed across a range of temperatures representative of the Penzé Estuary (13 to 22 °C) in early summer. A. minutum growth increased across this range and was the highest at 19 and 22 °C, whereas H. triquetra growth was maximal at intermediate temperatures (15–18 °C). Interestingly, the effect of temperature on the parasitoid infectivity changed depending on which host dinoflagellate was infected with the dinoflagellate responses to temperature following a positive trend in A. minutum (higher infections at 20–22 °C) and a unimodal trend in H. triquetra (higher infections at 18 °C). Low temperatures negatively affected parasitoid infections in both hosts (i.e., “thermal refuge”). These results demonstrate how temperature shifts may not only affect bloom development in microalgal species but also their control by parasitoids. 

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4. Investigating the Relationship between Nitrate, Total Dissolved Nitrogen, and Phosphate with Abundance of Pathogenic Vibrios and Harmful Algal Blooms in Rehoboth Bay, Delaware

   https://doi.org/10.1128/aem.00356-22  

   Rosales, Detbra ; Ellett, Ava ; Jacobs, John ; Ozbay, Gulnihal ; Parveen, Salina ; Pitula, Joseph ( July 2022 , Applied and Environmental Microbiology)

   Dozois, Charles M. (Ed.)

   ABSTRACT Vibrio spp. and phytoplankton are naturally abundant in marine environments. Recent studies have suggested that the co-occurrence of phytoplankton and the pathogenic bacterium Vibrio parahaemolyticus is due to shared ecological factors, such as nutrient requirements. We compared these communities at two locations in the Delaware Inland Bays, representing a site with high anthropogenic inputs (Torquay Canal) and a less developed area (Sloan Cove). In 2017 to 2018, using light microscopy, we were able to identify the presence of many bloom-forming algal species, such as Karlodinium veneficum , Dinophysis acuminata , Heterosigma akashiwo , and Chattonella subsalsa . Dinoflagellate biomass was higher at Torquay Canal than that at Sloan Cove. D. acuminata and Chloromorum toxicum were found only at Torquay Canal and were not observed in Sloan Cove. Most probable number real-time PCR revealed V. parahaemolyticus and Vibrio vulnificus in environmental samples. The abundance of vibrios and their virulence genes varied between sites, with a significant association between total dissolved nitrogen (TDN), PO 4 − , total dissolved phosphorus (TDP), and pathogenic markers. A generalized linear model revealed that principal component 1 of environmental factors (temperature, dissolved oxygen, salinity, TDN, PO 4 − , TDP, NO 3 :NO 2 , NO 2 − , and NH 4 + ) was the best at detecting total ( tlh+ ) V. parahaemolyticus , suggesting that they are the prime drivers for the growth and distribution of pathogenic Vibrio spp. IMPORTANCE Vibrio-associated illnesses have been expanding globally over the past several decades (A. Newton, M. Kendall, D. J. Vugia, O. L. Henao, and B. E. Mahon, Clin Infect Dis 54:S391–S395, 2012, https://doi.org/10.1093/cid/cis243 ). Many studies have linked this expansion with an increase in global temperature (J. Martinez-Urtaza, B. C. John, J. Trinanes, and A. DePaola, Food Res Int 43:10, 2010, https://doi.org/10.1016/j.foodres.2010.04.001 ; L. Vezzulli, R. R. Colwell, and C. Pruzzo, Microb Ecol 65:817–825, 2013, https://doi.org/10.1007/s00248-012-0163-2 ; R. N. Paranjpye, W. B. Nilsson, M. Liermann, and E. D. Hilborn, FEMS Microbiol Ecol 91:fiv121, 2015, https://doi.org/10.1093/femsec/fiv121 ). Temperature and salinity are the two major factors affecting the distribution of Vibrio spp. (D. Ceccarelli and R. R. Colwell, Front Microbiol 5:256, 2014, https://doi.org/10.3389/fmicb.2014.00256 ). However, Vibrio sp. abundance can also be affected by nutrient load and marine plankton blooms (V. J. McKenzie and A. R. Townsend, EcoHealth 4:384–396, 2007; L. Vezzulli, C. Pruzzo, A. Huq, and R. R. Colwell, Environ Microbiol Rep 2:27–33, 2010, https://doi.org/10.1111/j.1758-2229.2009.00128.x ; S. Liu, Z. Jiang, Y. Deng, Y. Wu, J. Zhang, et al. Microbiologyopen 7:e00600, 2018, https://doi.org/10.1002/mbo3.600 ). The expansion of Vibrio spp. in marine environments calls for a deeper understanding of the biotic and abiotic factors that play a role in their abundance. We observed that pathogenic Vibrio spp. were most abundant in areas that favor the proliferation of harmful algal bloom (HAB) species. These results can inform managers, researchers, and oyster growers on factors that can influence the growth and distribution of pathogenic Vibrio spp. in the Delaware Inland Bays. 

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5. Thermal acclimation influences the growth and toxin production of freshwater cyanobacteria

   https://doi.org/10.1002/lol2.10197  

   Layden, Tamara J. ; Kremer, Colin T. ; Brubaker, Delaney L. ; Kolk, Maeve A. ; Trout‐Haney, Jessica V. ; Vasseur, David A. ; Fey, Samuel B. ( May 2021 , Limnology and Oceanography Letters)

   Understanding how altered temperature regimes affect harmful cyanobacterial bloom formation is essential for managing aquatic ecosystems amidst ongoing climate warming. This is difficult because algal performance can depend on both current and past environments, as plastic physiological changes (acclimation) may lag behind environmental change. Here, we investigate how temperature variation on sub‐weekly timescales affects population growth and toxin production given acclimation. We studied four ecologically important freshwater cyanobacterial strains under low‐ and high‐nutrient conditions, measuring population growth rate after acclimation and new exposure to a range of temperatures. Cold‐acclimated populations (15.7°C) outperformed fully acclimated populations (held in constant conditions) across 65% of thermal environments, while hot‐acclimated populations (35.7–42.6°C) underperformed across 75% of thermal environments. Over a 5‐day period, cold‐acclimatedMicrocystis aeruginosaproduced ~2.5‐fold more microcystin than hot‐acclimated populations experiencing the same temperature perturbation. Our results suggest that thermal variation and physiology interact in underappreciated ways to influence cyanobacterial growth, toxin production, and likely bloom formation.

    

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