Covariability of dissolved oxygen with physical processes in the summertime Chesapeake Bay

Long, rapidly sampled time series measurements of dissolved oxygen, temperature, salinity, currents, winds, tides, and insolation were collected during the summer of 1987 across the mesohaline Chesapeake Bay. Analyses of the data show that short term variability of dissolved oxygen was both large and spatially heterogeneous. Time scales of variability ranged from the longest period fluctuations resolved (several days) to the sampling interval (several minutes). The largest variability was associated with large amplitude, wind and tide forced lateral internal oscillations of the pycnocline in the mainstem of the Bay. These resulted in advection of saline, hypoxic water from below the pycnocline onto the flanks of the Bay and into the lower reaches of the Choptank River, an adjoining tributary estuary. Advective variability at higher frequencies was likely due to internal waves, internal mixing, and/or spatial patchiness. Dissolved oxygen also responded to the daily cycle of insolation, but lagged insolation by at least 90° (6 h). Advective variability of dissolved oxygen is implicated as an important characteristic of the majority of summertime benthic environments in the mesohaline Chesapeake Bay and lower reaches of adjoining tributaries

Preface

Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 103 (2014): 1-5, doi:10.1016/j.dsr2.2014.02.007.The Gulf of Maine (GOM) is a continental shelf sea in the northwest Atlantic, USA that supports highly-productive shellfisheries that are frequently contaminated by toxigenic Alexandrium fundyense blooms and outbreaks of paralytic shellfish poisoning (PSP), resulting in significant economic and social impacts. Additionally, an emerging threat to these resources is from blooms of toxic Pseudo-nitzschia species that produce domoic acid, the toxin responsible for amnesic shellfish poisoning (ASP). Nearshore shellfish toxins are monitored by state agencies, whereas most offshore stocks have had little or no routine monitoring. As a result, large areas of federal waters have been indefinitely closed or their shellfish beds underexploited because of the potential risk these toxins pose and the lack of scientific understanding and management tools. Patterns and dynamics of Alexandrium blooms and the resulting shellfish toxicity in nearshore waters were examined in a number of research projects, the largest being the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB)-Gulf of Maine (GOM), a five-year regional program emphasizing field surveys, laboratory studies and numerical modeling. At the completion of the ECOHAB-GOM program (documented in Anderson et al., 2005), great progress was made in understanding A. fundyense blooms and resulting shellfish toxicity in nearshore waters, but there were major unknowns that still required investigation. For example, little was known about A. fundyense bloom dynamics in the waters south and east of Cape Cod, Massachusetts, and in particular, about the link between blooms in surface waters and toxicity in deep offshore shellfish. Large areas of offshore shellfish beds were off limits to harvest, including a 40,000 km2 region closed during the 2005 bloom and a much larger zone (~80,000 km2) including portions of Georges Bank was closed in 1990 after high levels of PSP toxicity were detected. In recent years, pressures were mounting from industry to open those offshore areas and to develop management strategies so that surfclam (Spisula solidissima), ocean quahog (Arctica islandica), and roe-on sea scallop (Placopecten magellanicus) fisheries could be opened. In response to these unknowns and societal needs, a new multi-investigator program, GOMTOX (Gulf of Maine Toxicity), was formulated and ultimately funded through the NOAA ECOHAB program. GOMTOX was a regional observation and modeling program that investigated the patterns and mechanisms underlying A. fundyense and Pseudo-nitzschia blooms and the resulting toxicity in shellfish in the southern GOM and its adjacent New England shelf waters, with special emphasis on the delivery pathways, mechanisms, and dynamics of offshore shellfish toxicity. The GOMTOX team of investigators included 16 principal investigators from eight institutions and, continuing in the ECOHAB-GOM tradition, strong participation from federal and state resource managers as well as representatives of the shellfish industry. This team worked together for over five years, running numerous large-scale survey cruises of Alexandrium cells and cysts, and also supporting industry cruises to collect shellfish from offshore sites including Georges Bank. Other efforts included participation in National Marine Fisheries Service surveys for shellfish (sea scallops, surfclams, and ocean quahogs), numerical modeling studies, deployment of sediment traps, and laboratory and ship-based experiments to investigate grazing and other processes that might regulate blooms and deliver toxins to shellfish in deeper waters. A smaller-scale but concurrent effort collected samples to characterize Pseudo-nitzschia species and their potential toxicity in the region.We gratefully acknowledge the support of NOAA through the ECOHAB program. Partial support for some of the studies contained herein was provided by NSF and NIEHS through the Woods Hole Center for Oceans and Human Health. Funding for J.L. Martin’s contributions from the Bay of Fundy was provided by Fisheries and Oceans Canada and NERACOOS, which is a part of the U.S. Integrated Ocean Observing System, funded in part by National Oceanic and Atmospheric Administration (NOAA)

The importance of human dimensions research in managing harmful algal blooms

Author Posting. © Ecological Society of America, 2010. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Frontiers in Ecology and the Environment 8 (2010): 75–83, doi:10.1890/070181.Harmful algal blooms (HABs) are natural freshwater and marine hazards that impose substantial adverse impacts on the human use of coastal and marine resources. The socioeconomic and health impacts of HABs can be considerable, thereby making a case for “human dimensions” research to support HAB response. Human dimensions research is multidisciplinary, integrating social science, humanities, and other fields with natural science to enhance resource management by addressing human causes, consequences, and responses to coastal environmental problems. Case studies reported here illustrate the importance of human dimensions research. Incorporating such research into the scientific agenda – as well as into management decisions of public agencies concerned with natural resource management, environmental protection, and public health and welfare – requires the development of both strategic guidance and institutional capacity. The recent development of a multi-agency research strategy for HAB response and a strategic plan for human dimensions research represent two important steps in this direction.This paper was developed with partial support from NOAA’s National Centers for Coastal and Ocean Science

Secondary metabolite gene expression and interplay of bacterial functions in a tropical freshwater cyanobacterial bloom

Cyanobacterial harmful algal blooms (cyanoHABs) appear to be increasing in frequency on a global scale. The Cyanobacteria in blooms can produce toxic secondary metabolites that make freshwater dangerous for drinking and recreation. To characterize microbial activities in a cyanoHAB, transcripts from a eutrophic freshwater reservoir in Singapore were sequenced for six samples collected over one day-night period. Transcripts from the Cyanobacterium Microcystis dominated all samples and were accompanied by at least 533 genera primarily from the Cyanobacteria, Proteobacteria, Bacteroidetes and Actinobacteria. Within the Microcystis population, abundant transcripts were from genes for buoyancy, photosynthesis and synthesis of the toxin microviridin, suggesting that these are necessary for competitive dominance in the Reservoir. During the day, Microcystis transcripts were enriched in photosynthesis and energy metabolism while at night enriched pathways included DNA replication and repair and toxin biosynthesis. Microcystis was the dominant source of transcripts from polyketide and non-ribosomal peptide synthase (PKS and NRPS, respectively) gene clusters. Unexpectedly, expression of all PKS/NRPS gene clusters, including for the toxins microcystin and aeruginosin, occurred throughout the day-night cycle. The most highly expressed PKS/NRPS gene cluster from Microcystis is not associated with any known product. The four most abundant phyla in the reservoir were enriched in different functions, including photosynthesis (Cyanobacteria), breakdown of complex organic molecules (Proteobacteria), glycan metabolism (Bacteroidetes) and breakdown of plant carbohydrates, such as cellobiose (Actinobacteria). These results provide the first estimate of secondary metabolite gene expression, functional partitioning and functional interplay in a freshwater cyanoHAB.Singapore. National Research Foundation (Singapore MIT Alliance for Research and Technology (SMART), Center for Environmental Sensing and Modeling (CENSAM) research program)National Science Foundation (U.S.) (Postdoctoral Research Fellowship in Biology, Grant No. DBI-1202865)National Institute of Environmental Health Sciences (NIEHS Grant P30-ES002109 to the MIT Center for Environmental Health Sciences)MIT International Science and Technology Initiatives (MISTI-Hayashi fund

Physiology, ecology and toxic properties of marine cyanobacteria blooms

Cyanobacteria blooms in marine waters are limited to only a few taxa with Trichodesmhm, Richelia, Nod&aria, and Aphanizomenon being most commonly observed. Nonhetcrocystous, nitrogen-fixing Trichodesmium spp. are found throughout low and mid-latitude oceans and seas of the Atlantic, Pacific, and Indian Oceans, and this genus is thought to be a major contributor to new nitrogen influx into these nitrogen-poor systems. Hcterocystous, nitrogenfixing Richelia and other cyanobacteria form unique symbioses with the centric diatoms, Rhizosolenia and Hemiaulus, in the North Pacific, Caribbean, and North Atlantic. Hcterocystous, diazotrophic, toxic Nodularia spumigena is restricted to brackish waters of the Baltic Sea and a coastal estuary of southern Australia and often arises from elcvatcd phosphorus input accompanying anthropogenic activities or vertical mixing processes. The nontoxic nitrogcn-fixing Aphanizomenon$os-uquae is also common in the Baltic, often co-occuning with Nodularia in the Baltic and Gulf of Finland but more often found in lower salinity areas of the region. Although each taxon responds to its environment uniquely, it appears that bloom production in the three free-living cyanobactcria largely supports an active microbial food web through dissolved organic compound flux to hetcrotrophic bacterial communities and their grazers. Blooms of cyanobacteria are common to freshwater system

The global, complex phenomena of harmful algal blooms

Author Posting. © Oceanography Society, 2005. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 18, 2 (2005): 136-147.Marine and fresh waters team with life, much of it microscopic, and most of it harmless; in fact, it is this microscopic life on which all aquatic life ultimately depends for food. Microscopic algae also play an important role in regulating atmospheric CO2 by sequestering it during production and transporting it to deeper waters. Yet some of the microscopic “algae” cause problems when they accumulate in sufficient numbers, due either to their production of endogenous toxins, or to their sheer biomass or even their physical shape. These are known as the harmful algae, or, when in sufficient numbers, harmful algal blooms (HABs). These blooms were formerly called “red tides” because many were composed of dinoflagellates containing red pigments that in high densities colored the water red, but blooms may also be green, yellow, or brown, depending on the type of algae present and their pigmentation. As with all blooms, their proliferation results from a combination of physical, chemical, and biological mechanisms and their interactions with other components of the food web that are for the most part poorly understood. Most HABs are dinoflagellates or cyanobacteria, but other classes of algae, including diatoms, have members that may form HABs under some conditions. As stated by J. Ryther and co-workers many years ago, “...there is no necessity to postulate obscure factors which would account for a prodigious growth of dinoflagellates to explain red water. It is necessary only to have conditions favoring the growth and dominance of a moderately large population of a given species, and the proper hydrographic and meteorological conditions to permit the accumulation of organisms at the surface and to effect their future concentrations in localized areas” (Ryther, 1955).Funding for these activities has been provided by NSF, NOAA, and the European Commission DG Research-Environment Directorate. GEOHAB is an initiative of SCOR (Scientific Committee on Oceanic Research) and IOC (Intergovernmental Oceanographic Commission of UNESCO). P. Glibert and D. Anderson were funded by the National Oceanic and Atmospheric Administration (NOAA), ECOHAB, MERHAB and NSF