Publications by authors named "Christopher J Gobler"

80 Publications

The role of algal blooms and community respiration in controlling the temporal and spatial dynamics of hypoxia and acidification in eutrophic estuaries.

Mar Pollut Bull 2021 Sep 9;172:112908. Epub 2021 Sep 9.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY 11968, United States of America. Electronic address:

While hypoxia and acidification can be common occurrences in eutrophic coastal zones, the precise, coupled temporal and spatial dynamics of these conditions are poorly described. Here, continuous measurements of water column pH, pCO, carbonate chemistry, and dissolved oxygen (DO) concentrations were made from spring through fall across two, temperate eutrophic estuaries, western Long Island Sound (LIS) and Jamaica Bay, NY, USA. Vertical dynamics were resolved using an underway towing profiler and an automated stationary profiling unit. During the study, high rates of respiration in surface and bottom waters (> -0.2 mg O L h) yielded strongly negative rates of net ecosystem metabolism during the summer (-4 to -8 g O m d). Ephemeral surface algal blooms caused brief periods (< one week) of basification and supersaturation of DO that were succeeded by longer periods of acidification and hypoxia. In deeper regions, hypoxia (< 2 mg L DO) and acidic water (pH < 7; total scale; pCO levels >2000 μatm) that persisted continuously for >40 days in both estuaries was often overlain by water with higher DO and pH. Diurnal vertical profiles demonstrated that oxic surface waters saturated with respect to calcium carbonate and DO during the day transitioned to unsaturated and hypoxic at night. Evidence is presented that, beyond respiration, nitrification in surface water promoted by sewage discharge and oxidation processes in sediments also contribute to acidification in these estuaries. Collectively, this study demonstrates the pervasive, persistent, and dynamic nature of hypoxia and acidification in eutrophic estuaries are likely to shape marine food webs.
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http://dx.doi.org/10.1016/j.marpolbul.2021.112908DOI Listing
September 2021

Mitigation of harmful algal blooms caused by Alexandrium catenella and reduction in saxitoxin accumulation in bivalves using cultivable seaweeds.

Harmful Algae 2021 05 5;105:102056. Epub 2021 Jun 5.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton NY, United States. Electronic address:

Alexandrium catenella is a harmful algal bloom (HAB)-forming dinoflagellate that causes significant damage to the cultivation and harvest of shellfish due to its synthesis of paralytic shellfish toxins.  To evaluate the potential for macroalgae aquaculture to mitigate A. catenella blooms, we determined the effects of three cultivable macroalgae - Saccharina latissima (sugar kelp), Chondrus crispus (Irish moss), and Ulva spp. - on A. catenella in culture- and field-based experiments.  Co-culture growth assays of A. catenella exposed to environmentally realistic concentrations of each macroalgae showed that all species except low levels of C. crispus caused cell lysis and significant reductions in A. catenella densities relative to control treatments of 17-74% in 2-3 days and 42-96% in ~one week (p<0.05 for all assays). In a toxin accumulation experiment, S. latissima significantly lessened (p<0.05) saxitoxin (STX) accumulation in blue mussels (Mytilus edulis), keeping levels (71.80±1.98 µg STX 100 g) below US closure limits (80 µg STX 100 g) compared to the untreated control (93.47±8.11 µg STX 100 g). Bottle incubations of field-collected, bloom populations of A. catenella experienced significant reductions in cell densities of up to 95% when exposed to aquaculture concentrations of all three macroalgae (p<0.005 for all). The stocking of aquacultured S. latissima within mesocosms containing a bloom population of A. catenella (initial density: 3.2 × 10 cells L) reduced the population of A. catenella by 73% over 48 h (p<0.005) while Ulva addition caused a 54% reduction in A. catenella over 96 h (p<0.01).  Among the three seaweeds, their ordered ability to inhibit A. catenella was S. latissima > Ulva spp. > C. crispus. Seaweeds' primary anti-A. catenella activity were allelopathic, while nutrient competition, pH elevation, and macroalgae-attached bacteria may have played a contributory role in some experiments. Collectively, these results suggest that the integration of macroalgae with shellfish-centric aquaculture establishments should be considered as a non-invasive, environmentally friendly, and potentially profit-generating measure to mitigate A. catenella-caused damage to the shellfish aquaculture industry.
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http://dx.doi.org/10.1016/j.hal.2021.102056DOI Listing
May 2021

Metatranscriptome Library Preparation Influences Analyses of Viral Community Activity During a Brown Tide Bloom.

Front Microbiol 2021 31;12:664189. Epub 2021 May 31.

Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN, United States.

There is growing interest in the use of metatranscriptomics to study virus community dynamics. We used RNA samples collected from harmful brown tides caused by the eukaryotic alga within New York (United States) estuaries and in the process observed how preprocessing of libraries by either selection for polyadenylation or reduction in ribosomal RNA (rRNA) influenced virus community analyses. As expected, more reads mapped to the genome in polyadenylation-selected libraries compared to the rRNA-reduced libraries, with reads mapped in each sample correlating to one another regardless of preprocessing of libraries. Yet, this trend was not seen for reads mapping to the Aureococcus anophagefferens Virus (AaV), where significantly more reads (approximately two orders of magnitude) were mapped to the AaV genome in the rRNA-reduced libraries. In the rRNA-reduced libraries, there was a strong and significant correlation between reads mappings to AaV and . Overall, polyadenylation-selected libraries produced fewer viral contigs, fewer reads mapped to viral contigs, and different proportions across viral realms and families, compared to their rRNA-reduced pairs. This study provides evidence that libraries generated by rRNA reduction and not selected for polyadenylation are more appropriate for quantitative characterization of viral communities in aquatic ecosystems by metatranscriptomics.
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http://dx.doi.org/10.3389/fmicb.2021.664189DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8200674PMC
May 2021

Transcriptomic and isotopic data reveal central role of ammonium in facilitating the growth of the mixotrophic dinoflagellate, Dinophysis acuminata.

Harmful Algae 2021 04 27;104:102031. Epub 2021 Apr 27.

Stony Brook University, School of Marine and Atmospheric Sciences, 239 Montauk Hwy, Southampton, NY 11968, United States. Electronic address:

Dinophysis spp. are mixotrophs that are dependent on specific prey, but are also potentially reliant on dissolved nutrients. The extent to which Dinophysis relies on exogenous N and the specific biochemical pathways important for supporting its autotrophic and heterotrophic growth are unknown. Here, the nutritional ecology of Dinophysis was explored using two approaches: 1) N tracer experiments were conducted to quantify the concentration-dependent uptake rates and associated kinetics of various N compounds (nitrate, ammonium, urea) of Dinophysis cultures and 2) the transcriptomic responses of Dinophysis cultures grown with multiple combinations of prey and nutrients were assessed via dinoflagellate spliced leader-based transcriptome profiling. Of the N compounds examined, ammonium had the highest V and affinity coefficient, and lowest K for both pre-starved and pre-fed cultures, collectively demonstrating the preference of Dinophysis for this N source while little-to-no nitrate uptake was observed. During the transcriptome experiments, Dinophysis grown with nitrate and without prey had the largest number of genes with lower transcript abundances, did not increase abundance of transcripts associated with nitrate/nitrite uptake or reduction, and displayed no cellular growth, suggesting D. acuminata is not capable of growing on nitrate. When offered prey, the transcriptomic response of Dinophysis included the production of phagolysosomes, enzymes involved in protein and lipid catabolism, and N acquisition through amino acid degradation pathways. Compared with cultures only offered ammonium or prey, cultures offered both ammonium and prey had the largest number of genes with increased transcript abundances, the highest growth rate, and the unique activation of multiple pathways involved in cellular catabolism, further evidencing the ability of Dinophysis to grow optimally as a mixotroph. Collectively, this study evidences the key role ammonium plays in the mixotrophic growth of Dinophysis and reveals the precise biochemical pathways that facilitate its mixotrophic growth.
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http://dx.doi.org/10.1016/j.hal.2021.102031DOI Listing
April 2021

Marine harmful algal blooms (HABs) in the United States: History, current status and future trends.

Harmful Algae 2021 02 3;102:101975. Epub 2021 Mar 3.

Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA, Seattle, WA, 98112, United States.

Harmful algal blooms (HABs) are diverse phenomena involving multiple. species and classes of algae that occupy a broad range of habitats from lakes to oceans and produce a multiplicity of toxins or bioactive compounds that impact many different resources. Here, a review of the status of this complex array of marine HAB problems in the U.S. is presented, providing historical information and trends as well as future perspectives. The study relies on thirty years (1990-2019) of data in HAEDAT - the IOC-ICES-PICES Harmful Algal Event database, but also includes many other reports. At a qualitative level, the U.S. national HAB problem is far more extensive than was the case decades ago, with more toxic species and toxins to monitor, as well as a larger range of impacted resources and areas affected. Quantitatively, no significant trend is seen for paralytic shellfish toxin (PST) events over the study interval, though there is clear evidence of the expansion of the problem into new regions and the emergence of a species that produces PSTs in Florida - Pyrodinium bahamense. Amnesic shellfish toxin (AST) events have significantly increased in the U.S., with an overall pattern of frequent outbreaks on the West Coast, emerging, recurring outbreaks on the East Coast, and sporadic incidents in the Gulf of Mexico. Despite the long historical record of neurotoxic shellfish toxin (NST) events, no significant trend is observed over the past 30 years. The recent emergence of diarrhetic shellfish toxins (DSTs) in the U.S. began along the Gulf Coast in 2008 and expanded to the West and East Coasts, though no significant trend through time is seen since then. Ciguatoxin (CTX) events caused by Gambierdiscus dinoflagellates have long impacted tropical and subtropical locations in the U.S., but due to a lack of monitoring programs as well as under-reporting of illnesses, data on these events are not available for time series analysis. Geographic expansion of Gambierdiscus into temperate and non-endemic areas (e.g., northern Gulf of Mexico) is apparent, and fostered by ocean warming. HAB-related marine wildlife morbidity and mortality events appear to be increasing, with statistically significant increasing trends observed in marine mammal poisonings caused by ASTs along the coast of California and NSTs in Florida. Since their first occurrence in 1985 in New York, brown tides resulting from high-density blooms of Aureococcus have spread south to Delaware, Maryland, and Virginia, while those caused by Aureoumbra have spread from the Gulf Coast to the east coast of Florida. Blooms of Margalefidinium polykrikoides occurred in four locations in the U.S. from 1921-2001 but have appeared in more than 15  U.S. estuaries since then, with ocean warming implicated as a causative factor. Numerous blooms of toxic cyanobacteria have been documented in all 50  U.S. states and the transport of cyanotoxins from freshwater systems into marine coastal waters is a recently identified and potentially significant threat to public and ecosystem health. Taken together, there is a significant increasing trend in all HAB events in HAEDAT over the 30-year study interval. Part of this observed HAB expansion simply reflects a better realization of the true or historic scale of the problem, long obscured by inadequate monitoring. Other contributing factors include the dispersion of species to new areas, the discovery of new HAB poisoning syndromes or impacts, and the stimulatory effects of human activities like nutrient pollution, aquaculture expansion, and ocean warming, among others. One result of this multifaceted expansion is that many regions of the U.S. now face a daunting diversity of species and toxins, representing a significant and growing challenge to resource managers and public health officials in terms of toxins, regions, and time intervals to monitor, and necessitating new approaches to monitoring and management. Mobilization of funding and resources for research, monitoring and management of HABs requires accurate information on the scale and nature of the national problem. HAEDAT and other databases can be of great value in this regard but efforts are needed to expand and sustain the collection of data regionally and nationally.
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http://dx.doi.org/10.1016/j.hal.2021.101975DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8058451PMC
February 2021

Harmful dinoflagellate Cochlodinium polykrikoides impairs the feeding behavior of larval sheepshead minnows (Cyprinodon variegatus).

J Fish Biol 2021 Jul 14;99(1):153-163. Epub 2021 Mar 14.

Department of Biology, St Joseph's College, Patchogue, New York, USA.

Research evaluating the toxicity of the harmful dinoflagellate Cochlodinium (a.k.a. Margalefidinium) polykrikoides has been dominated by acute bioassays while the sublethal effects remain less well understood. This study examined the sublethal effects of C. polykrikoides exposure on the feeding behavior of larval estuarine fish. Sheepshead minnow (Cyprinodon variegatus) larvae were used in feeding experiments which assessed the total consumption of zooplankton prey (i.e., Artemia nauplii) over defined time periods. Larvae exposed to intermediate concentrations (i.e., 10  cells ml ) of clonal cultures of C. polykrikoides saw statistically significant reductions (range = 10%-81%) in the Artemia consumed compared to controls (i.e., filtered seawater, culture media or nontoxin producing dinoflagellate). These reductions were found independent of whether the larvae were fed or starved prior to experimentation. As these concentrations are similar to those typically found during mild blooms or at the periphery of dense blooms, these findings have significant implications for the feeding behavior of ichthyoplankton.
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http://dx.doi.org/10.1111/jfb.14707DOI Listing
July 2021

Removal of 1,4-dioxane during on-site wastewater treatment using nitrogen removing biofilters.

Sci Total Environ 2021 Jun 26;771:144806. Epub 2021 Jan 26.

New York State Center for Clean Water Technology, Stony Brook University, Stony Brook 11794, United States of America; School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794, United States of America; Department of Civil Engineering, Stony Brook University, Stony Brook, NY 11794, United States of America. Electronic address:

The presence and release of 1,4-dioxane to groundwater from onsite-wastewater treatment systems (OWTS), which represent 25% of the total wastewater treatment in the U.S., has not been studied to date. In this study we monitored 1,4-dioxane in six septic tank effluents (STE) and receiving OWTS installed at residences on Long Island (LI), NY, for a period of 15 months. We specifically evaluated the performance of Nitrogen Removing Biofilters (NRBs) as an innovative/alternative-OWTS, consisting of a top sand layer and a bottom woodchip/sand layer, to simultaneously remove nitrogen and 1,4-dioxane. 1,4-Dioxane levels in STE (mean: 1.49 μg L; range: 0.07-8.45 μg L; n = 37) were on average > 15 times higher than tap water from these residences, demonstrating that 1,4-dioxane primarily originated from the use of household products. NRBs were effective in removing both 1,4-dioxane and total nitrogen with an overall removal efficiency of 56 ± 20% and 88 ± 12%, respectively. The majority of 1,4-dioxane removal (~80%) occurred in the top oxic layer of the NRBs. The detection of functional genes (dxmB, prmA, and thmA), which encode for metabolic and co-metabolic 1,4-dioxane degradation, in NRBs provides the first field evidence of aerobic microbial degradation of 1,4-dioxane occurring in a wastewater system. Given that there are ~500,000 conventional OWTS on LI, the 1,4-dioxane discharge to groundwater from residential wastewater was estimated at 195 ± 205 kg yr , suggesting high risk of contamination to shallow aquifers. The results also demonstrate that installation of NRBs can reduce 1,4-dioxane to levels even lower than the NY State drinking water standard of 1 μg L.
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http://dx.doi.org/10.1016/j.scitotenv.2020.144806DOI Listing
June 2021

The Efficacy of Hydrogen Peroxide in Mitigating Cyanobacterial Blooms and Altering Microbial Communities across Four Lakes in NY, USA.

Toxins (Basel) 2020 06 29;12(7). Epub 2020 Jun 29.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY 11794, USA.

Hydrogen peroxide (HO) has been proposed as an agent to mitigate toxic cyanobacterial blooms due to the heightened sensitivity of cyanobacteria to reactive oxygen species relative to eukaryotic organisms. Here, experiments were conducted using water from four diverse, eutrophic lake ecosystems to study the effects of HO on cyanobacteria and non-target members of the microbial community. HO was administered at 4 µg L and a combination of fluorometry, microscopy, flow cytometry, and high throughput DNA sequencing were used to quantify the effects on eukaryotic and prokaryotic plankton communities. The addition of HO resulted in a significant reduction in cyanobacteria levels in nearly all experiments (10 of 11), reducing their relative abundance from, on average, 85% to 29% of the total phytoplankton community with being highly sensitive, being moderately sensitive, and being most resistant. Concurrently, eukaryotic algal levels increased in 75% of experiments. The bacterial phyla , cyanobacteria, , and were most negatively impacted by HO, with being the most sensitive. The ability of HO to reduce, but not fully eliminate, cyanobacteria from the eutrophic water bodies studied here suggests it may not be an ideal mitigation approach in high biomass ecosystems.
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http://dx.doi.org/10.3390/toxins12070428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7405413PMC
June 2020

An assessment on the intrapopulational and intraindividual genetic diversity in LSU rDNA in the harmful algal blooms-forming dinoflagellate Margalefidinium (= Cochlodinium) fulvescens based on clonal cultures and bloom samples from Jiaozhou Bay, China.

Harmful Algae 2020 06 21;96:101821. Epub 2020 May 21.

CAS Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao 266071, China. Electronic address:

Large subunit ribosomal DNA (LSU rDNA) sequences have been increasingly used to infer the phylogeny and species identity of organisms, a few previous studies, however, have observed high intraspecific and even intraindividual variability in LSU rDNA in some dinoflagellate species due to, assumably, large copy numbers of rDNA in dinoflagellates. Since the copy number of LSU rDNA varies tremendously among dinoflagellate species, the intraspecific and intraindividual diversity for a species of particular interest thus needs to be investigated individually. As a toxic and HABs-forming dinoflagellate, Margalefidinium (= Cochlodinium) fulvescens has been observed to approach blooming density in Jiaozhou Bay, China since 2015 after numerous blooms having been reported from other countries. In trying to identify the source of this newly observed HABs-forming species in China by sequencing the LSU rDNA for both field samples and clonal cultures, we noticed and thus further investigated high intrapopulational and intraindividual genetic diversities of the dinoflagellate. The D1-D6 region of the LSU rDNA (1,435 bases) was amplified from 7 field samples (pooled cells) and 11 clonal cultures, cloned, sequenced, and analyzed phylogenetically for 2,341 sequences obtained. All the numbers of sequences obtained from each clonal culture were far less than the estimated rDNA copy number in M. fulvescens. In the clone library, only one unique sequence was contained in all samples as the most dominant sequence. We found high intrapopulational and intraindividual genetic diversity in M. fulvescens as reflected in the number of polymorphic sites and unique sequences in the clone library for different field samples and clonal cultures in comparison to other species. The mean number of nucleotide differences of each sequence from different field samples and clonal cultures were 6.43 and 4.42 bases, respectively, with the highest being 132 bases, nearly 10%. The sequences with highest variability may be easily annotated as different species if they were obtained from environmental genomic studies because sequence-based species identification in meta-barcoding studies often use "97% identity" threshold. Based on that the mean and overall intrapopulational genetic diversity calculated for 7 field samples was equivalent to the mean and overall intraindividual variability for 11 clonal cultures in indices of genetic diversity, together with the result of AMOVA analysis, we infer that the variability within individual cells (i.e. variability among LSU rDNA polymorphic copies) caused both the intraindividual and intrapopulational genetic diversities observed in the M. fulvescens population, and a higher interpopulational diversity may exist among different geographic populations. The results provide an insightful basis for such a comprehensive interpopulational comparison and important implications for identifying species and establishing new taxa based on the similarity comparison to reference sequences deposited in databases.
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http://dx.doi.org/10.1016/j.hal.2020.101821DOI Listing
June 2020

The Composition and Function of Microbiomes Within Colonies Are Significantly Different Than Native Bacterial Assemblages in Two North American Lakes.

Front Microbiol 2020 28;11:1016. Epub 2020 May 28.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States.

The toxic cyanobacterium is one of the most pervasive harmful algal bloom (HAB) genera and naturally occurs in large colonies known to harbor diverse heterotrophic bacterial assemblages. While colony-associated microbiomes may influence blooms, there remains a limited understanding of the structure and functional potential of these communities and how they may be shaped by changing environmental conditions. To address this gap, we compared the dynamics of -attached (MCA), free-living (FL), and whole water (W) microbiomes during blooms using next-generation amplicon sequencing (16S rRNA), a predictive metagenome software, and other bioinformatic approaches. Microbiomes were monitored through high resolution spatial-temporal surveys across two North American lakes, Lake Erie (LE) and Lake Agawam (LA; Long Island, NY, United States) in 2017, providing the largest dataset of these fractions to date. Sequencing of 126 samples generated 7,922,628 sequences that clustered into 7,447 amplicon sequence variants (ASVs) with 100% sequence identity. Across lakes, the MCA microbiomes were significantly different than the FL and W fractions being significantly enriched in , , , and and depleted of Further, although MCA communities harbored > 900 unique ASVs, they were significantly less diverse than the other fractions with diversity inversely related to bloom intensity, suggesting increased selection pressure on microbial communities as blooms intensified. Despite taxonomic differences between lakes, predicted metagenomes revealed conserved functional potential among MCA microbiomes. MCA communities were significantly enriched in pathways involved in N and P cycling and microcystin-degradation. Taxa potentially capable of N-fixation were significantly enriched ( < 0.05) and up to four-fold more abundant within the MCA faction relative to other fractions, potentially aiding in the proliferation of blooms during low N conditions. The MCA predicted metagenomes were conserved over 8 months of seasonal changes in temperature and N availability despite strong temporal succession in microbiome composition. Collectively, these findings indicate that colonies harbor a statistically distinct microbiome with a conserved functional potential that may help facilitate bloom persistence under environmentally unfavorable conditions.
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http://dx.doi.org/10.3389/fmicb.2020.01016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7270213PMC
May 2020

Dissolved oxygen and pH criteria leave fisheries at risk.

Science 2020 Apr;368(6489):372-373

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, USA.

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http://dx.doi.org/10.1126/science.aba4896DOI Listing
April 2020

Climate Change and Harmful Algal Blooms: Insights and perspective.

Harmful Algae 2020 01 25;91:101731. Epub 2019 Dec 25.

Stony Brook University, School of Marine and Atmospheric Sciences, Southampton, NY, 11968, United States. Electronic address:

Climate change is transforming aquatic ecosystems. Coastal waters have experienced progressive warming, acidification, and deoxygenation that will intensify this century. At the same time, there is a scientific consensus that the public health, recreation, tourism, fishery, aquaculture, and ecosystem impacts from harmful algal blooms (HABs) have all increased over the past several decades. The extent to which climate change is intensifying these HABs is not fully clear, but there has been a wealth of research on this topic this century alone. Indeed, the United Nations' Intergovernmental Panel on Climate Change's (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) approved in September 2019 was the first IPCC report to directly link HABs to climate change. In the Summary for Policy Makers, the report made the following declarations with "high confidence": In addition, the report specifically outlines a series of linkages between heat waves and HABs. These statements about HABs and climate change and the high levels of confidence ascribed to them provides clear evidence that the field of HABs and climate change has matured and has, perhaps, reached a first plateau of certainty. While there are well-documented global trends in HABs being promoted by human activity, including climate change, individual events are driven by local, regional, and global drivers, making it critical to carefully evaluate the conditions and responses at appropriate scales. It is within this context that the first Special Issue on Climate Change and Harmful Algal Blooms is published in Harmful Algae.
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http://dx.doi.org/10.1016/j.hal.2019.101731DOI Listing
January 2020

Dynamic CO and pH levels in coastal, estuarine, and inland waters: Theoretical and observed effects on harmful algal blooms.

Harmful Algae 2020 01 6;91:101594. Epub 2019 Apr 6.

University of Copenhagen, Marine Biological Section, Strandpromenaden 5, DK 3000 Helsingør, Denmark.

Rising concentrations of atmospheric CO results in higher equilibrium concentrations of dissolved CO in natural waters, with corresponding increases in hydrogen ion and bicarbonate concentrations and decreases in hydroxyl ion and carbonate concentrations. Superimposed on these climate change effects is the dynamic nature of carbon cycling in coastal zones, which can lead to seasonal and diel changes in pH and CO concentrations that can exceed changes expected for open ocean ecosystems by the end of the century. Among harmful algae, i.e. some species and/or strains of Cyanobacteria, Dinophyceae, Prymnesiophyceae, Bacillariophyceae, and Ulvophyceae, the occurrence of a CO concentrating mechanisms (CCMs) is the most frequent mechanism of inorganic carbon acquisition in natural waters in equilibrium with the present atmosphere (400 μmol CO  mol total gas), with varying phenotypic modification of the CCM. No data on CCMs are available for Raphidophyceae or the brown tide Pelagophyceae. Several HAB species and/or strains respond to increased CO concentrations with increases in growth rate and/or cellular toxin content, however, others are unaffected. Beyond the effects of altered C concentrations and speciation on HABs, changes in pH in natural waters are likely to have profound effects on algal physiology. This review outlines the implications of changes in inorganic cycling for HABs in coastal zones, and reviews the knowns and unknowns with regard to how HABs can be expected to ocean acidification. We further point to the large regions of uncertainty with regard to this evolving field.
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http://dx.doi.org/10.1016/j.hal.2019.03.012DOI Listing
January 2020

Harmful algal blooms: A climate change co-stressor in marine and freshwater ecosystems.

Harmful Algae 2020 01 21;91:101590. Epub 2019 May 21.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, 11968, United States. Electronic address:

Marine and freshwater ecosystems are warming, acidifying, and deoxygenating as a consequence of climate change. In parallel, the impacts of harmful algal blooms (HABs) on these ecosystems are intensifying. Many eutrophic habitats that host recurring HABs already experience thermal extremes, low dissolved oxygen, and low pH, making these locations potential sentinel sites for conditions that will become more common in larger-scale systems as climate change accelerates. While studies of the effects of HABs or individual climate change stressors on aquatic organisms have been relatively common, studies assessing their combined impacts have been rare. Those doing so have reported strong species- and strain-specific interactions between HAB species and climate change co-stressors yielding outcomes for aquatic organisms that could not have been predicted based on investigations of these factors individually. This review provides an ecological and physiological framework for considering HABs as a climate change co-stressor and considers the consequences of their combined occurrence for coastal ecosystems. This review also highlights critical gaps in our understanding of HABs as a climate change co-stressor that must be addressed in order to develop management plans that adequately protect fisheries, aquaculture, aquatic ecosystems, and human health. Ultimately, incorporating HAB species into experiments and monitoring programs where the effects of multiple climate change stressors are considered will provide a more ecologically relevant perspective of the structure and function of marine ecosystems in future, climate-altered systems.
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http://dx.doi.org/10.1016/j.hal.2019.03.008DOI Listing
January 2020

Experimental acidification increases susceptibility of Mercenaria mercenaria to infection by Vibrio species.

Mar Environ Res 2020 Feb 7;154:104872. Epub 2020 Jan 7.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, 11790, USA. Electronic address:

Ocean acidification alters seawater carbonate chemistry, which can have detrimental impacts for calcifying organisms such as bivalves. This study investigated the physiological cost of resilience to acidification in Mercenaria mercenaria, with a focus on overall immune performance following exposure to Vibrio spp. Larval and juvenile clams reared in seawater with high pCO (~1200 ppm) displayed an enhanced susceptibility to bacterial pathogens. Higher susceptibility to infection in clams grown under acidified conditions was derived from a lower immunity to infection more so than an increase in growth of bacteria under high pCO. A reciprocal transplant of juvenile clams demonstrated the highest mortality amongst animals transplanted from low pCO/high pH to high pCO/low pH conditions and then exposed to bacterial pathogens. Collectively, these results suggest that increased pCO will result in immunocompromised larvae and juveniles, which could have complex and pernicious effects on hard clam populations.
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http://dx.doi.org/10.1016/j.marenvres.2019.104872DOI Listing
February 2020

Impact of groundwater quality and associated byproduct formation during UV/hydrogen peroxide treatment of 1,4-dioxane.

Water Res 2020 Apr 25;173:115534. Epub 2020 Jan 25.

New York State Center for Clean Water Technology, Stony Brook University, Stony Brook, NY, 11794, USA; School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, 11794, USA.

In this study, a semi-batch, bench-scale UV/hydrogen peroxide (UV/HO) advanced oxidation process system was used to investigate how typical groundwater quality parameters (pH, alkalinity, natural organic matter (NOM), nitrate, and iron) influence the treatment of 1,4-dioxane. Deionized (DI) water spiked with 1,4-dioxane (100 μg L), treated using HO (10 mg L) in a commercially available UV system (40 W low-pressure lamp) showed an UV fluence-based first-order rate constant (k') and electrical energy-per-order (EEO) of 4.32✕10 cm-mJ and 0.15 kWh-m-order, respectively. The most abundant byproduct generated in spiked-DI water was oxalic acid (up to 55 μg L), followed by formic and acetic acids. The k' showed no significant difference at pH ranging from 5 to 7 and at low alkalinity concentrations (<20 mg-CaCO L), typical of sandy aquifers. The k' declined by up to 85% with increasing NOM concentration. Elevated production (up to ∼400% increase) of aldehydes and organic acids was observed in NOM-spiked water, implying that NOM is a significant byproduct precursor during UV/HO treatment. High NO concentration (10 mg-N L) in source water reduced the k' by 25%, while no significant impact was observed at lower concentrations (<2 mg-N L). Addition of Fe(II) at 0.5 mg-L resulted in an instantaneous Fenton-reaction-assisted removal of ∼10% 1,4-dioxane in the presence of HO, but did not enhance the performance of UV/HO treatment over time. In contrast, both Fe(II) and Fe(III) addition lowered the k' by 15-27%. The decline of k' observed in these experiments was attributed to reduced UVT (Fe), OH radical scavenging (pH), or both (NO, NOM). Treatment of groundwater samples collected from three 1,4-dioxane-contaminated wells located in Long Island, NY, showed k' values of 13-40% lower than what was observed for DI water due to radical scavenging from a combination of high NO and NOM in the samples. A multiple linear-regression model, developed using water quality data as model input, showed good agreement with field observations (paired t-test: p > 0.05) in predicting k' for the removal of 1,4-dioxane from groundwater. This study provides the first systematic evaluation of the impacts of groundwater quality on UV/HO process to remove environmentally relevant levels of 1,4-dioxane and reports standardized performance-related parameters to aid in the design and evaluation of full-scale systems.
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http://dx.doi.org/10.1016/j.watres.2020.115534DOI Listing
April 2020

Prokaryotic and eukaryotic microbiomes associated with blooms of the ichthyotoxic dinoflagellate Cochlodinium (Margalefidinium) polykrikoides in New York, USA, estuaries.

PLoS One 2019 7;14(11):e0223067. Epub 2019 Nov 7.

Stony Brook University, School of Marine and Atmospheric Sciences, Southampton, NY, United States of America.

While harmful algal blooms caused by the ichthyotoxic dinoflagellate, Cochlodinium (Margalefidinium) polykrikoides, are allelopathic and may have unique associations with bacteria, a comprehensive assessment of the planktonic communities associated with these blooms has been lacking. Here, we used high-throughput amplicon sequencing to assess size fractionated (0.2 and 5 μm) bacterial (16S) and phytoplankton assemblages (18S) associated with blooms of C. polykrikoides during recurrent blooms in NY, USA. Over a three-year period, samples were collected inside ('patch') and outside ('non-patch') dense accumulations of C. polykrikoides to assess the microbiome associated with these blooms. Eukaryotic plankton communities of blooms had significantly lower diversity than non-bloom samples, and non-bloom samples hosted 30 eukaryotic operational taxonomic units (OTUs) not found within blooms, suggesting they may have been allelopathically excluded from blooms. Differential abundance analyses revealed that C. polykrikoides blooms were significantly enriched in dinoflagellates (p<0.001) and the experimental enrichment of C. polykrikoides led to a significant increase in the relative abundance of eight genera of dinoflagellates but a significant decline in other eukaryotic plankton. Amoebophrya co-dominated both within- and near- C. polykrikoides blooms and was more abundant in bloom patches. The core bacterial microbiome of the >0.2μm fraction of blooms was dominated by an uncultured bacterium from the SAR11 clade, while the >5μm size fraction was co-dominated by an uncultured bacterium from Rhodobacteraceae and Coraliomargarita. Two bacterial lineages within the >0.2μm fraction, as well as the Gammaproteobacterium, Halioglobus, from the >5μm fraction were unique to the microbiome of blooms, while there were 154 bacterial OTUs only found in non-bloom waters. Collectively, these findings reveal the unique composition and potential function of eukaryotic and prokaryotic communities associated with C. polykrikoides blooms.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0223067PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6837389PMC
March 2020

3,000 km and 1,500-year presence of Aureococcus anophagefferens reveals indigenous origin of brown tides in China.

Mol Ecol 2019 09 29;28(17):4065-4076. Epub 2019 Aug 29.

School of Marine and Atmospheric Sciences, Stony Brook University, New York, NY, USA.

The nonmotile, spherical, picoplanktonic (2-μm-sized) pelagophyte Aureococcus anophagefferens has caused numerous harmful blooms ("brown tides") across global marine ecosystems. Blooms have developed along the east coast of the USA since 1985, a limited number of times in South Africa around 1997, and frequently in China since 2009. As a consequence, the harmful blooms have caused massive losses in aquaculture and coastal ecosystems, particularly mortalities in cultured shellfish. Therefore, whether A. anophagefferens was recently introduced to China via natural/artificial transport of resting stage cells or has been an indigenous species has become a question of profound ecological significance and broad interest, which motivated our extensive investigation on the geographic and historical presence of this species in the seas of China. We applied a combined approach of extensive PCR-based detection and sequencing, germination experiments and monoclonal antibody staining of germlings to samples of surface sediment and sediment core (dated via combined isotopic measurements) collected from all four seas of China, and searched the supplementary data set of a recent Science publication. We discovered that A. anophagefferens does have a resting stage in the sediment, but it also has a wide geographic distribution both in China (covering a range of ~30° in latitude, ~15.7° in longitude and 2.5-3,456 m in water depth; temperate to tropical and coastal to open oceans) and in almost all oceans of the world and a historical presence of >1,500 years in the Bohai Sea, China. The work revealed that A. anophagefferens is not a recently introduced, but an indigenous species in China and has in fact a globally cosmopolitan distribution.
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http://dx.doi.org/10.1111/mec.15196DOI Listing
September 2019

Ocean warming along temperate western boundaries of the Northern Hemisphere promotes an expansion of Cochlodinium polykrikoides blooms.

Proc Biol Sci 2019 06 5;286(1904):20190340. Epub 2019 Jun 5.

1 School of Marine and Atmospheric Sciences, Stony Brook University , Southampton, NY 11968 , USA.

Since the early 1990s, ocean temperatures have increased and blooms of the icthyotoxic dinoflagellate Cochlodinium polykrikoides (a.k.a. Margalefidinium polykrikoides) have become more widespread across the Northern Hemisphere. This study used high-resolution (1-30 km), satellite-based sea surface temperature records since 1982 to model trends in growth and bloom season length for strains of C. polykrikoides inhabiting North American and East Asian coastlines to understand how warming has altered blooms in these regions. Methods provided approximately 180× greater spatial resolution than previous studies of the impacts of warming on harmful algae, providing novel insight into near shore, coastal environments. Along the US East Coast, significant increases in potential growth rates and bloom season length for North American ribotypes were observed with bloom-favourable conditions becoming established earlier and persisting longer from Chesapeake Bay through Cape Cod, areas where blooms have become newly established and/or intensified this century. Within the Sea of Japan, modelled mean potential growth rates and bloom season length of East Asian ribotypes displayed a significant positive correlation with rising sea surface temperatures since 1982, a period during which observed maximal cell densities of C. polykrikoides blooms have significantly increased. Results suggest that warming has contributed, in part, to altering the phenology of C. polykrikoides populations, potentially expanding its realized niche in temperate zones of the Northern Hemisphere.
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http://dx.doi.org/10.1098/rspb.2019.0340DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6571469PMC
June 2019

Effects of the harmful algae, Alexandrium catenella and Dinophysis acuminata, on the survival, growth, and swimming activity of early life stages of forage fish.

Mar Environ Res 2019 Jun 30;148:46-56. Epub 2019 Apr 30.

School of Marine and Atmospheric Science, Stony Brook Southampton, 39 Tuckahoe Road, Southampton, NY, 11968, USA. Electronic address:

The effects of co-occurring harmful algal blooms (HABs) on marine organisms is largely unknown. We assessed the individual and combined impacts of the toxin producing HABs, Alexandrium catenella and Dinophysis acuminata, and a non-toxin-producing HAB (Gymnodinium instriatum) on early life stages of two estuarine fish species (Menidia beryllina and Cyprinodon variegatus). Lethal (i.e. time to death) and sublethal (i.e. growth, grazing rate, and swimming activity) effects of cultured HABs were investigated for eleutheroembryo and larval life stages. Mixed algal treatments (i.e. A. catenella and D. acuminata mixtures) were often equally toxic as A. catenella monoculture treatments alone, although responses depended on the fish species and life stage. Fish exposed to toxin producing HABs died significantly sooner (i.e. <1-3 days) than controls. Significant differences in sublethal effects were also found between fed controls and toxic HAB treatments, although responses were often similar to G. instriatum or starved controls. Collectively, the results demonstrate that HABs may reduce fish productivity and fitness.
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http://dx.doi.org/10.1016/j.marenvres.2019.04.013DOI Listing
June 2019

The harmful algae, and , elicit stronger transcriptomic and mortality response in larval bivalves () than climate change stressors.

Ecol Evol 2019 Apr 5;9(8):4931-4948. Epub 2019 Apr 5.

School of Marine and Atmospheric Sciences Stony Brook University Southampton New York.

Global ocean change threatens marine life, yet a mechanistic understanding of how organisms are affected by specific stressors is poorly understood. Here, we identify and compare the unique and common transcriptomic responses of an organism experiencing widespread fisheries declines, (bay scallop) exposed to multiple stressors including high CO, elevated temperature, and two species of harmful algae, (aka ) and using high-throughput sequencing (RNA-seq). After 48 hr of exposure, scallop transcriptomes revealed distinct expression profiles with larvae exposed to harmful algae ( and ) displaying broader responses in terms of significantly and differentially expressed (DE) transcripts (44,922 and 4,973; respectively) than larvae exposed to low pH or elevated temperature (559 and 467; respectively). Patterns of expression between larvae exposed to each harmful algal treatment were, however, strikingly different with larvae exposed to displaying large, significant declines in the expression of transcripts (3,615; 87% of DE transcripts) whereas exposure to increased the abundance of transcripts, more than all other treatments combined (43,668; 97% of DE transcripts). Larvae exposed to each stressor up-regulated a common set of 21 genes associated with protein synthesis, cellular metabolism, shell growth, and membrane transport. Larvae exposed to displayed large increases in antioxidant-associated transcripts, whereas acidification-exposed larvae increased abundance of transcripts associated with shell formation. After 10 days of exposure, each harmful algae caused declines in survival that were significantly greater than all other treatments. Collectively, this study reveals the common and unique transcriptional responses of bivalve larvae to stressors that promote population declines within coastal zones, providing insight into the means by which they promote mortality as well as traits possessed by bay scallops that enable potential resistance.
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http://dx.doi.org/10.1002/ece3.5100DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6476759PMC
April 2019

Transcriptional Shifts Highlight the Role of Nutrients in Harmful Brown Tide Dynamics.

Front Microbiol 2019 12;10:136. Epub 2019 Feb 12.

Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, United States.

Harmful algal blooms (HABs) threaten ecosystems and human health worldwide. Controlling nitrogen inputs to coastal waters is a common HAB management strategy, as nutrient concentrations often suggest coastal blooms are nitrogen-limited. However, defining best nutrient management practices is a long-standing challenge: in part, because of difficulties in directly tracking the nutritional physiology of harmful species in mixed communities. Using metatranscriptome sequencing and incubation experiments, we addressed this challenge by assaying the physiological ecology of the ecosystem destructive alga, . Here we show that gene markers of phosphorus deficiency were expressed , and modulated by the enrichment of phosphorus, which was consistent with the observed growth rate responses. These data demonstrate the importance of phosphorus in controlling brown-tide dynamics, suggesting that phosphorus, in addition to nitrogen, should be evaluated in the management and mitigation of these blooms. Given that nutrient concentrations alone were suggestive of a nitrogen-limited ecosystem, this study underscores the value of directly assaying harmful algae for the development of management strategies.
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http://dx.doi.org/10.3389/fmicb.2019.00136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6379262PMC
February 2019

The Individual and Combined Effects of the Cyanotoxins, Anatoxin-a and Microcystin-LR, on the Growth, Toxin Production, and Nitrogen Fixation of Prokaryotic and Eukaryotic Algae.

Toxins (Basel) 2019 01 15;11(1). Epub 2019 Jan 15.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY 11968, USA.

Globally, eutrophication and warming of aquatic ecosystems has increased the frequency and intensity of cyanobacterial blooms and their associated toxins, with the simultaneous detection of multiple cyanotoxins often occurring. Despite the co-occurrence of cyanotoxins such as microcystins and anatoxin-a (ATX) in water bodies, their effects on phytoplankton communities are poorly understood. The individual and combined effects of microcystin-LR (MC-LR) and ATX on the cyanobacteria spp., and (a.k.a. ), and the chlorophyte, were investigated in the present study. Cell density, chlorophyll-a content, and the maximum quantum efficiency of photosystem II (Fv/Fm) of cells were generally lowered after exposure to ATX or MC-LR, while the combined treatment with MC-LR and ATX synergistically reduced the chlorophyll-a concentration of strain LE-3. Intracellular levels of microcystin in LE-3 significantly increased following exposure to MC-LR + ATX. The maximum quantum efficiency of photosystem II of strain UTEX B377 declined during exposure to the cyanotoxins. Nitrogen fixation by UTEX B377 was significantly inhibited by exposure to ATX, but was unaffected by MC-LR. In contrast, the combination of both cyanotoxins (MC-LR + ATX) caused a synergistic increase in the growth of . While the toxins caused an increase in the activity of enzymes that scavenge reactive oxygen species in cyanobacteria, enzyme activity was unchanged or decreased in . Collectively this study demonstrates that MC-LR and ATX can selectively promote and inhibit the growth and performance of green algae and cyanobacteria, respectively, and that the combined effect of these cyanotoxins was often more intense than their individual effects on some strains. This suggests that the release of multiple cyanotoxins in aquatic ecosystems, following the collapse of blooms, may influence the succession of plankton communities.
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http://dx.doi.org/10.3390/toxins11010043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6357180PMC
January 2019

Individual and combined effects of low dissolved oxygen and low pH on survival of early stage larval blue crabs, Callinectes sapidus.

PLoS One 2018 7;13(12):e0208629. Epub 2018 Dec 7.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, New York, United States of America.

A large number of coastal ecosystems globally are subjected to concurrent hypoxic and acidified conditions that will likely intensify and expand with continued climate change. In temperate regions, the spawning of many important organisms including the Atlantic blue crab Callinectes sapidus occurs during the summer months when the severity of coastal hypoxia and acidification is the greatest. While the blue crab earliest larval stage can be exposed to co-occurring hypoxia and acidification observed in many coastal ecosystems, the effects of these concurrent stressors on larval blue crab survival is unknown. This study investigated the individual and combined consequences of low dissolved oxygen (DO) and low pH on blue crab larvae survival through a series of short-term experiments. During 14-day experiments with moderately hypoxic conditions (117-127 μM O2 or 3.74-4.06 mg L-1) and acidified conditions (pH on total scale of 7.16-7.33), low DO and low pH individually and significantly reduced larval survival by 60% and 49%, respectively, with the combination of stressors reducing survival by 87% compared to the control treatment (210-269 μM O2 or 6.72-8.61 mg L-1, 7.91-7.94 DO and pH, respectively). During 4-day experiments with lower DO levels (68-83 μM O2 or 2.18-2.62 mg L-1) and comparable pH levels of 7.29-7.39, low DO individually reduced survival by >90% compared to the control (261-267 μM O2 or 8.35-8.54 mg L-1, 7.92-7.97 DO and pH, respectively), whereas low pH had no effect and there was no interaction between stressors. Over a 4-day period, the DO threshold at which 50% of the larval blue crab population died (LC50) was 121 μM O2 (3.86 mgL-1). In 14-day experiments, the DO and pH effects were additive, yielding survival rates lower than the individual treatments, and significantly correlated with DO and pH concentrations. Collectively, these findings indicate that blue crab sensitivity to both low DO and low pH are acute within the larval stage, depend on the intensity and duration of exposure, and leads to mortality, thereby potentially contributing to the interannual variability and possible regional declines of this fishery.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0208629PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6285982PMC
May 2019

Nitrogen limitation, toxin synthesis potential, and toxicity of cyanobacterial populations in Lake Okeechobee and the St. Lucie River Estuary, Florida, during the 2016 state of emergency event.

PLoS One 2018 23;13(5):e0196278. Epub 2018 May 23.

School of Marine and Atmospheric Sciences, Stony Brook University, NY, United States of America.

Lake Okeechobee, FL, USA, has been subjected to intensifying cyanobacterial blooms that can spread to the adjacent St. Lucie River and Estuary via natural and anthropogenically-induced flooding events. In July 2016, a large, toxic cyanobacterial bloom occurred in Lake Okeechobee and throughout the St. Lucie River and Estuary, leading Florida to declare a state of emergency. This study reports on measurements and nutrient amendment experiments performed in this freshwater-estuarine ecosystem (salinity 0-25 PSU) during and after the bloom. In July, all sites along the bloom exhibited dissolved inorganic nitrogen-to-phosphorus ratios < 6, while Microcystis dominated (> 95%) phytoplankton inventories from the lake to the central part of the estuary. Chlorophyll a and microcystin concentrations peaked (100 and 34 μg L-1, respectively) within Lake Okeechobee and decreased eastwards. Metagenomic analyses indicated that genes associated with the production of microcystin (mcyE) and the algal neurotoxin saxitoxin (sxtA) originated from Microcystis and multiple diazotrophic genera, respectively. There were highly significant correlations between levels of total nitrogen, microcystin, and microcystin synthesis gene abundance across all surveyed sites (p < 0.001), suggesting high levels of nitrogen supported the production of microcystin during this event. Consistent with this, experiments performed with low salinity water from the St. Lucie River during the event indicated that algal biomass was nitrogen-limited. In the fall, densities of Microcystis and concentrations of microcystin were significantly lower, green algae co-dominated with cyanobacteria, and multiple algal groups displayed nitrogen-limitation. These results indicate that monitoring and regulatory strategies in Lake Okeechobee and the St. Lucie River and Estuary should consider managing loads of nitrogen to control future algal and microcystin-producing cyanobacterial blooms.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0196278PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5965861PMC
August 2018

Succession and toxicity of Microcystis and Anabaena (Dolichospermum) blooms are controlled by nutrient-dependent allelopathic interactions.

Harmful Algae 2018 04 13;74:67-77. Epub 2018 Apr 13.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, 11968, United States. Electronic address:

Microcystis and Anabaena (Dolichospermum) are among the most toxic cyanobacterial genera and often succeed each other during harmful algal blooms. The role allelopathy plays in the succession of these genera is not fully understood. The allelopathic interactions of six strains of Microcystis and Anabaena under different nutrient conditions in co-culture and in culture-filtrate experiments were investigated. Microcystis strains significantly reduced the growth of Anabaena strains in mixed cultures with direct cell-to-cell contact and high nutrient levels. Cell-free filtrate from Microcystis cultures proved equally potent in suppressing the growth of nutrient replete Anabaena cultures while also significantly reducing anatoxin-a production. Allelopathic interactions between Microcystis and Anabaena were, however, partly dependent on ambient nutrient levels. Anabaena dominated under low N conditions and Microcystis dominated under nutrient replete and low P during which allelochemicals caused the complete suppression of nitrogen fixation by Anabaena and stimulated glutathione S-transferase activity. The microcystin content of Microcystis was lowered with decreasing N and the presence of Anabaena decreased it further under low P and high nutrient conditions. Collectively, these results indicate that strong allelopathic interactions between Microcystis and Anabaena are closely intertwined with the availability of nutrients and that allelopathy may contribute to the succession, nitrogen availability, and toxicity of cyanobacterial blooms.
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http://dx.doi.org/10.1016/j.hal.2018.03.002DOI Listing
April 2018

characterization of bivalve larval shells: a confocal Raman microscopy study.

J R Soc Interface 2018 04;15(141)

Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, Bremerhaven, Germany.

confocal Raman microscopy (CRM), polarized light microscopy and Fourier transform infrared spectroscopy (FTIR) were used to determine if a significant amount of amorphous calcium carbonate (ACC) exists within larval shells of Baltic mytilid mussels (-like) and whether the amount of ACC varies during larval development. No evidence for ACC was found from the onset of shell deposition at 21 h post-fertilization (hpf) until 48 hpf. Larval shells were crystalline from 21 hpf onwards and exhibited CRM and FTIR peaks characteristic of aragonite. Prior to shell deposition at 21 hpf, no evidence for carbonates was observed through CRM. We further analysed the composition of larval shells in three other bivalve species, , and and observed no evidence for ACC, which is in contrast to previous work on the same species. Our findings indicate that larval bivalve shells are composed of crystalline aragonite and we demonstrate that conflicting results are related to sub-optimal measurements and misinterpretation of CRM spectra. Our results demonstrate that the common perception that ACC generally occurs as a stable and abundant precursor during larval bivalve calcification needs to be critically reviewed.
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http://dx.doi.org/10.1098/rsif.2017.0723DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5938577PMC
April 2018

Evaluation of Rapid, Early Warning Approaches to Track Shellfish Toxins Associated with Dinophysis and Alexandrium Blooms.

Mar Drugs 2018 Jan 13;16(1). Epub 2018 Jan 13.

School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY 11968, USA.

Marine biotoxin-contaminated seafood has caused thousands of poisonings worldwide this century. Given these threats, there is an increasing need for improved technologies that can be easily integrated into coastal monitoring programs. This study evaluates approaches for monitoring toxins associated with recurrent toxin-producing and blooms on Long Island, NY, USA, which cause paralytic and diarrhetic shellfish poisoning (PSP and DSP), respectively. Within contrasting locations, the dynamics of pelagic and cell densities, toxins in plankton, and toxins in deployed blue mussels () were compared with passive solid-phase adsorption toxin tracking (SPATT) samplers filled with two types of resin, HP20 and XAD-2. Multiple species of wild shellfish were also collected during blooms and used to compare toxin content using two different extraction techniques (single dispersive and double exhaustive) and two different toxin analysis assays (liquid chromatography/mass spectrometry and the protein phosphatase inhibition assay (PP2A)) for the measurement of DSP toxins. DSP toxins measured in the HP20 resin were significantly correlated (² = 0.7-0.9, < 0.001) with total DSP toxins in shellfish, but were detected more than three weeks prior to detection in deployed mussels. Both resins adsorbed measurable levels of PSP toxins, but neither quantitatively tracked cell densities, toxicity in plankton or toxins in shellfish. DSP extraction and toxin analysis methods did not differ significantly ( > 0.05), were highly correlated (² = 0.98-0.99; < 0.001) and provided complete recovery of DSP toxins from standard reference materials. Blue mussels () and ribbed mussels () were found to accumulate DSP toxins above federal and international standards (160 ng g) during blooms while Eastern oysters () and soft shell clams () did not. This study demonstrated that SPATT samplers using HP20 resin coupled with PP2A technology could be used to provide early warning of DSP, but not PSP, events for shellfish management.
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http://dx.doi.org/10.3390/md16010028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5793076PMC
January 2018

Impact of nitrogen chemical form on the isotope signature and toxicity of a marine dinoflagellate.

Mar Ecol Prog Ser 2018 23;602:63-76. Epub 2018 Aug 23.

Virginia Institute of Marine Science, Gloucester Point, VA 23062 USA

Despite a global interest in the relationship between harmful algal blooms (HABs) and eutrophication, the impact of natural versus anthropogenic nutrient sources on species composition or toxicity of HABs remains unclear. Stable isotopes are used to identify and track nitrogen (N) sources to water bodies, and thus can be used to ascertain the N source(s) used by the phytoplankton in those systems. To focus this tool for a particular species, the fundamental patterns of N isotope fractionation by that organism must first be understood. While literature is available describing N isotope fractionation by diatoms and coccolithophores, data are lacking regarding dinoflagellates. Here we investigated the effects of N chemical form on isotope fractionation (Δ) and toxin content using isolates of the autotrophic dinoflagellate, in single-N and mixed-N experiments. Growth of exclusively on nitrate (NO ), ammonium (NH ), or urea, resulted in Δ of 2.7±1.4‰, 29±9.3‰, or 0.3±0.1‰, respectively, with the lowest cellular toxicity reported during urea utilization. Cells initially utilized NH and urea when exposed to mixed-N medium, and only utilized NO after NH decreased below 2-4 μM. This pattern of N preference was similar across all N treatments, suggesting that there is no effect of preconditioning on N chemical preference by . In NO and urea-rich environments, the δN of would resemble the source(s) of N utilized, supporting this tool's utility as a tracer of N source(s) facilitating bloom formation, however, caution is advisable in NH rich environments where the large Δ value could lead to misinterpretation of the signal.
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http://dx.doi.org/10.3354/meps12619DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6874107PMC
August 2018

Effects of Microcystis on development of early life stage Japanese medaka (Oryzias latipes): Comparative toxicity of natural blooms, cultured Microcystis and microcystin-LR.

Aquat Toxicol 2018 Jan 2;194:18-26. Epub 2017 Nov 2.

School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000 United States. Electronic address:

Freshwater cyanobacterial harmful algal blooms (CyanoHABs) caused by algae in the genus Microcystis have been increasing in frequency and severity in recent decades. Microcystis blooms threaten aquatic organisms through effects associated with the rapid increase of biomass and the production of the hepatotoxin microcystin (MC) by toxic strains. Among fish, effects of blooms are likely to be more severe for early life stages, and physiological impacts on this life stage could significantly impact recruitment and fish populations. This study explores the effects of Microcystis blooms on the development of fish using the model organism, the Japanese medaka (Oryzias latipes), under realistic exposure conditions. Medaka embryos were exposed to natural blooms collected from New York City (USA) lakes, lab cultures of Microcystis, and MC-LR solutions. Field collected samples were more toxic than lab cultures (even when compared at the same algal density or MC concentration), causing decreased survival, premature time to hatch, reduced body length, yolk sac edema, and decreased heart rate, while lab culture exposures only resulted in bradycardia. Heart rate was the most sensitive endpoint measured, being depressed in embryos exposed to both lab cultures and field collected blooms. Generalized linear model analysis indicated bradycardia was statistically associated with both cell densities of blooms and MC concentrations, while single factor analysis indicated that MC concentrations had a stronger correlation compared to cell densities. However, MC exposure could not fully explain the effects observed, as exposures to MC-LR solutions alone were not able to reduce heart rate as severely as algal exposures. Collectively, these experiments indicate that factors beyond exposure to MC or even isolated Microcystis strains influence heart rate of fish exposed to Microcystis blooms. Enhanced mortality, depressed heart rate, and abnormal development observed in response to environmentally realistic exposures of Microcystis blooms could affect success of fish at both individual or population levels.
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http://dx.doi.org/10.1016/j.aquatox.2017.10.026DOI Listing
January 2018
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