NECAN: The Northeast Coastal Acidification Network
NECAN is currently hosting stakeholder engagement workshops to inform and learn from fishermen, clam harvesters, aquaculturists, and coastal water quality programs regarding ocean and coastal acidification.
- Maine Workshop December 10 Meeting Summary
- Massachusetts South Shore Workshop April 27 Meeting Summary
- Rhode Island Workshop June 5 Meeting Summary
- Massachusetts North Shore Workshop June 23 Meeting Summary
- SYNTHESIS of Workshops 1-4
- Canada Workshop October 6 Meeting Summary
- Long Island Sound Workshop January 11
If you have any questions regarding these workshops, please contact Cassie Stymiest (firstname.lastname@example.org).
NECAN's publication "Ocean and Coastal Acidification off New England and Nova Scotia" is now available in the new special issue of Oceanography magazine. This is the result of the state of the science webinars and workshops that NECAN conducted last year.
Click here or the registration tab above to register for the NECAN Listserve for webinars and other important information.
Who are we? The Northeast Coastal Acidification Network (NECAN) represents a nexus of scientists, federal and state agency representatives, resource managers, and affected industry partners dedicated towards coordinating and guiding regional observing, research, and modeling endeavors. The purpose is to better identify critical vulnerabilities, particularly with respect to regionally important and economically significant marine resources. NECAN is part of the larger Integrated Sentinel Monitoring Network coordinated by the joint Ocean and Coastal Ecosystem Health Committee of NERACOOS and the Northeast Regional Ocean Council (NROC). The NECAN steering committee includes:
- Ru Morrison* (NERACOOS)
- Todd Capson (Independent Consultant)
- Mel Cote (EPA)
- Dwight Gledhill (NOAA/OAP)
- Bill Mook (Mook Sea Farm)
- Joe Salisbury (UNH)
- Elizabeth Turner (NOAA/NOS/NCCOS)
- Esperanza Stancioff (UMaine Cooperative Extension / ME Sea Grant)
- Cassie Stymiest (NERACOOS)
- Helmuth Thomas (Dalhousie University)
- Sylvain DeGuise (CT Sea Grant)
NECAN serves as a necessary interface between research and industry interests whereby state-of-the-science information can be readily exchanged. Regional interest groups and key data and information synthesis products can as a result be specifically tailored and informed by user group needs. NECAN's area of focus is on the waters from Long Island Sound to the Scotian Shelf.
June 30, 2015: "The NECAN story – Linking Ocean and Coastal Acidification science to managers, policymakers, and coastal communities in the northeast United States and Canadian Maritimes" presented by presented by J. Ruairidh Morrison, Northeast Regional Association of Coastal Ocean Observation Systems; Todd Capson; Mel Cote, U.S. EPA; Dwight Gledhill, U.S. NOAA Ocean Acidification Program; Matt Liebman, U.S. EPA; Bill Mook, Mook Sea Farms; Joe Salisbury, University of New Hampshire; Esperanza Stancioff, University of Maine Sea Grant Extension; Cassie Stymiest, Northeast Regional Association of Coastal Ocean Observation Systems; Helmuth Thomas, Dalhousie University; Elizabeth Turner, U.S. NOAA National Centers for Coastal Ocean Science
Public awareness and concern about Ocean Acidification (OA) is growing at the same time as the science is still maturing. In addition to the trend in global OA, near-coastal areas experience Coastal Acidification that is highly dependent on factors such as freshwater and nutrient delivery which are beyond the general increase in atmospheric carbon dioxide, but may be influenced by other human use and climate trends. Addressing these interacting stresses, their influences on Ocean and Coastal Acidification (OCA), and impacts to coastal resources is complex and challenging, both due to the relative paucity of OCA studies and communication gaps between scientists and stakeholders. The Northeast Coastal Acidification Network (NECAN) is a cross border collaboration of scientists, agency representatives, industry and non-governmental organizations that seeks to provide relevant information about OCA to stakeholders in the Canadian Maritimes, Gulf of Maine and Long Island Sound. Efforts to date include a webinar series, state-of-the-science meeting and publications, web-based translation materials and face-to-face interactive stakeholder engagement workshops. The ultimate goal is to develop a regional implementation plan that will outline the information needed by stakeholders, including managers, policymakers, and industry, as well as the required observations, research, and communication mechanisms. This presentation will review these approaches, where we are to date, and the work that remains.
Note: The NECAN Webinar Series is concluded. Since November 2013, NECAN sponsored a series of 16 webinars on topics related to regional coastal acidification. The recorded webinars are available below along with abstracts of the presentations.
March 18, 2014: “An Integrated Assessment Model for the U.S. Commercial Sea Scallop Fishery” presented by Sarah Cooley, Ocean Conservancy with contributions from J. Rheuban, S.C. Doney, D. Glover (WHOI); D. Hart, J. Hare (NOAA NMFS); and V. Luu (Boston College)
The sea scallop (Placopecten magellanicus) is the nation's most valuable single-species fishery, providing $559 million in ex-vessel revenue in 2012, but this lucrative natural resource faces ongoing pressures including changing climate, increasing ocean acidification, continuing harvests, and fluctuating markets. Currently, the combined impact of these different factors is difficult to incorporate adequately into policy decisions. We present an integrated assessment model (IAM) comprising reduced-form biogeochemical, population, and economic numerical submodels. The one-dimensional biogeochemical model including anthropogenic and natural factors has been developed for sea scallop habitats in Georges Bank and the Mid Atlantic Bight. Preliminary results indicate good model skill for each submodel. We are testing the sensitivity of the coupled natural–socioeconomic system to different scenarios involving scallop harvest levels, price fluctuations, fishery rules, environmental conditions (including the overlapping stressors of ocean acidification and temperature), and national and international demand. This will lead to development of a dashboard interface where decisionmakers can interact with model results and consider the influence of different policy decisions.
March 13, 2014: "Coastal ocean acidification and its co-occurrence with multiple stressors: Implications for marine organisms” presented by Chris Gobler, Stony Brook University
In coastal zones, ocean acidification is already effecting marine life. This talk will present data from estuaries across the US Northeast that display low pH conditions (<< 8) during summer and fall months concurrent with the decline in DO concentrations. While hypoxic waters and/or regions in close proximity to sewage discharge can experience extreme acidification (pH <7.0), even near-normoxic but eutrophic regions of some estuaries are often relatively acidified (pH<7.7) during late summer and/or early fall. The close spatial and temporal correspondence between DO and pH and the occurrence of extremes in these conditions in regions with the most intense nutrient loading indicated that they were driven primarily by microbial respiration. In addition to acidification, coastal animals are concurrently exposed to an array of additional stressors including hypoxia, thermal stress, and harmful algal blooms. All of these stressors are expected to intensify along with ocean acidification in the coming decades. This talk will review that state of acidification in northeast US estuaries and will review how multiple stressors interact with and/or co-occur with ocean acidification. The effects of these combined stressors on early life stage finfish and shellfish will also be presented.
March 11, 2014: "Including effects of ocean acidification in fisheries population and ecosystem models" presented by Gavin Fay, National Marine Fisheries Service
Models for the assessment of living marine resources that account for the effects of ocean acidification (OA) are crucial for understanding the consequences of these effects for fisheries and ecosystem management. In this webinar, I will review the status of efforts to integrate data on the effects of OA into the types models currently used to provide scientific advice to fisheries managers, to evaluate the effects of OA with respect to those of other ecosystem drivers (e.g. exploitation). These include single-species stock assessment approaches that estimate acidification-dependent recruitment relationships, with population dynamics models using these relationships then projected given scenarios for the magnitude of OA. Ecosystem models have also been used to explore the effects of OA on ecosystem structure and function, and to quantify associated changes in ecosystem services. Although model scenarios implemented to date have been simple, they are useful for demonstrating possible consequences of OA, and for quantifying the effects on local and regional economies. Scenarios show a large range of effects on both fisheries yield and the biomass of species both directly and indirectly affected by OA. However, the magnitude and precise nature of OA effects, and interaction with other system drivers (e.g. fishing, warming, habitat loss, etc.) will ultimately depend on understanding species’ responses to acidification. The modeling tools being developed in the Northeast US and elsewhere provide frameworks that can guide both managers and scientists as they are updated with new information from monitoring activities and experimental work to explore the impacts of acidification.
March 10, 2014: “An Experimental Investigation of the Surf Clam Response to Ocean Acidification” presented by Anne Cohen and Daniel McCorkle, Woods Hole Oceanographic Institution, with contributions from Lisa Milke, James Widman, Jr, Barbara Ramon
In situ measurements reveal that seawater pH and Ωar in estuaries and coastal embayments along much of the Northeastern US are already significantly different from open ocean values, and that year round aragonite under-saturation (Ωar<1) will be reached by mid-century, if current CO2 emissions trends continue. We asked whether these projected levels of ocean acidification (OA) would negatively affect early development of the Atlantic surf clam, Spisula solidissima, which is currently the most important commercial clam species in the US. We also asked whether feeding could offset any negative effects of OA on growth and development. Embryos were introduced to acidified seawater treatments within four hours post-fertilization and reared over a period of 6 days. Air and Air-CO2 mixtures bubbled into ambient Vineyard Sound seawater yielded Ωar values ranging from ambient (2.2) to substantially under-saturated (0.5 to 0.7). Larvae were reared in both nutritionally replete and nutritionally depleted conditions, and growth was monitored by subsampling on days 3 (formation of PDI) and 6 (formation of PDII). The effects of OA and feeding on growth and development were evaluated by measurements of shell length, shell weight and scanning electron microscope (SEM) imaging to detect shell deformities. Overall, OA had no statistically significant effect on shell growth or development and shell formation was normal even in under-saturated conditions. At 6 days post-fertilization, OA had no impact on mortality. Conversely, growth rates of larvae reared in nutritionally replete conditions were significantly higher than those reared in nutritionally depleted conditions, across all CO2 treatment levels. We compare the response of S. solidissima to that of other east coast species at the same stage of development and reared under the same experimental conditions. Our results suggest that early development of S. solidissima may be remarkably resilient to levels of acidification projected for the US east coast region by the end of this century.
March 4, 2014: "Ocean Acidification in Alaska: Perceptions, Risks and Economics" presented by Jeremy T. Mathis, NOAA Pacific Marine Environmental Laboratory with contributions from: Sarah Colley, Lauren Frisch, Wiley Evans, Jessica Cross, Stacey Reisdorph, Natalie Monacci, Noelle Lucey, Claudine Hauri, Julie Ekstrom, Tom Hurst, and Steve Colt
The extremely valuable commercial and subsistence fisheries around Alaska are located in seas projected to experience rapid transitions in pH and other chemical parameters caused by ocean acidification (OA) in the coming decades. Many of the marine organisms that are most intensely affected by OA, such as mollusks contribute substantially to the region’s commercial activities as well as the gross domestic product (GDP) of the United States as well as other countries. Prior studies of OA’s potential impacts on human communities have focused on possible economic losses from specific scenarios of human dependence on harvests and damages to marine species. However, non-economic impacts due to OA are likely to also manifest, such as changes in food security or shifts in livelihoods. Here, we describe the current patterns of dependence on marine resources within the region that could be negatively impacted by OA and current community characteristics to determine the risk to the region’s fishery sector. Results suggest that OA merits consideration in policy and adaptation planning, as it may represent yet another challenge to many communities that are already in socioeconomic decline. To determine the public awareness and understanding of this potentially game-changing threat we conducted a regional survey to better understand the multitude of variables that influence the perceptions of the risk associated with OA, as well as environmental literacy and support for mitigation efforts. This has helped us identify where there are gaps in understanding of OA and how future OA initiatives can be implemented in order to prepare individuals, communities, and the fishing industry for future changes in ocean chemistry.
February 18, 2014: “Effects of elevated CO2 on the early life-stages of marine fishes and potential consequences of ocean acidification” presented by R. Christopher Chambers, NOAA NEFSC
The limited available evidence about effects of high CO2 and associated acidification of oceans on marine fishes suggests that effects will differ among species and life-stages, may be subtle, and may interact with other stressors. This presentation summarizes activities underway at the NEFSC’s Howard Laboratory to better understand ocean acidification (OA) effects on the early life-stages of marine fishes and how to communicate these results to the public. These activities include collection and analysis of metadata, experimental studies, and outreach. We are using meta-analysis to establish context of what is known about high-CO2 effects on marine fishes, to draw generalities where appropriate, and to serve as a framework for our experimental approach. We have designed a laboratory CO2-delivery system with which to challenge early life-stages of locally important fish taxa to a stepped series of experiments on the effects of CO2 and co-stressors. To date, we have completed three experiments – one 1-way (factor: CO2) and two 2-way (CO2 × temperature) – using this system to evaluate responses of summer flounder (Paralichthys dentatus) and winter flounder (Pseudopleuronectes americanus). Results from the 1-way experiment on summer flounder have been digested and have shown several significant outcomes. Concentration of CO2 had a direct effect on embryonic period mortality, and on the growth and developmental rates of larvae. Cranial-facial measurements from cleared-and-stained larval specimens were consistent with accelerated larval development at high CO2. Further, histopathology sections of larvae showed a higher prevalence of abnormalities at elevated CO2 concentrations. Implications of these sublethal effects on ontogenetic rates of summer flounder will be discussed. Lastly, we are developing and evaluating age-appropriate outreach materials on OA effects on marine ecosystems that can be used for in-house and off-campus outreach opportunities.
February 11, 2014- "Effects of ocean acidification on phytoplankton in the coastal ocean" presented by Andrew King
Phytoplankton, single-celled photosynthesizing microorganisms, account for about half of global primary production. They are inextricably linked to the ocean in two major ways: the cycling of major and trace elements, and the synthesis of compounds that drive marine foodwebs. If and how long-term changes in the ocean (including carbonate chemistry) will affect phytoplankton and their roles in the ocean's biogeochemical cycles and foodwebs remains a heavily researched topic. In particular, studies have suggested that ocean acidification (OA) could modify the marine nitrogen cycle, phytoplankton community structure, and phytoplankton nutritional composition. In this talk, I will summarize significant findings regarding phytoplankton and OA, and I will discuss ongoing research and future directions relevant to the North American northeast region.
January 28, 2014- "Developmental and energetic basis linking larval oyster shell formation to ocean acidification" presented by George Waldbusser, Oregon State University
Much interest has been generated about the Pacific Northwest oyster seed crisis that began in the mid to late 2000’s. Although empirical evidence had shown a strong relationship between conditions in which larvae are spawned and production output in the Whiskey Creek Shellfish Hatchery, a mechanism linking the higher CO2 (but not thermodynamically corrosive) waters to larval success was lacking. We proposed that the rate of shell formation during the precipitation of the first shell in larval oysters put a strong energetic demand on the larvae at a period of time when they are reliant almost solely on endogenous energy (egg reserves). I will discuss our ongoing work with the industry here in the Pacific Northwest, more recent experimental work that is supporting our hypothesis that kinetics (rates) of shell formation is an important predictor in understanding sensitivities, and some preliminary work to understand the biological mechanisms for how oyster larvae may precipitate shell material so quickly. In addition, changes in the marine carbonate chemistry of the California Current Ecosystem and the estuaries tightly coupled to it help to explain why the larval oysters in the Pacific Northwest have served to be a canary in the coal mine.
January 21, 2014-"The American lobster in a changing climate“ presented by Richard A. Wahle, University of Maine School of Marine Sciences
This webinar examines ocean warming and acidification in the context of the broader challenges confronting the American lobster (Homarus americanus) fishery across the Northeast US and Atlantic Canada. The story of the American lobster over the past two decades is one of contrasting trajectories. Lobster populations in the southern end of the species’ range are collapsing, just as those in the Gulf of Maine and Atlantic Canada have soared to historic highs. The effects of ocean warming are evident as a retreat of lobsters to deeper waters in the south and a net northward shift of the center of the population. In southern New England, extreme warm events and hypoxia have triggered mass mortality and disease, while northern waters that have historically been on the cool side for lobster are becoming more habitable. In the Gulf of Maine, warming, coupled with the widespread depletion of predatory groundfish may largely explain the lobster boom over the past two decades. But the astonishing glut of lobsters and the 2008 global financial crisis have driven lobster prices to a 50-year low. With fuel costs inexorably rising, the business of lobstering is becoming ever more challenging. Against this background, recent evidence that ocean acidification adversely affects shellfish is heightening concerns for the fate of the lobster fishery. A review of the literature on acidification effects on marine organisms suggest sensitivities to acidification are species- and life-stage-specific. One study on the European lobster (H. gammarus) suggests acidified seawater did not affect larval survival or growth, but exoskeletons were less mineralized than controls in ambient seawater. In contrast, in another study older benthic juvenile H. americanus had more calcified skeletons under prolonged acidified treatments. Elevated pCO2 acidifies lobster blood and other tissues and could interfere with enzymatic regulation, hormonal systems, and biomineralization of the exoskeleton. To date shell disease in lobsters has not been linked to ocean acidification. Whether the levels of CO2 projected for coastal and shelf waters in the coming decades will adversely affect lobster populations in the future remains unclear.
January 14, 2014- "Oceanographic variability across the Gulf of Maine as measured by GNATS (Gulf of Maine North Atlantic Time Series)" presented by William M. Balch, Bigelow Laboratory for Ocean Sciences
William Balch will give an overview of the Gulf of Maine North Atlantic Time Series (GNATS) which is a 35+year, NASA-centric, field program that crosses the Gulf of Maine (GoM) between Portland, Maine and Yarmouth, NS using ferries and ships of opportunity. Data are collected on bio-optical, hydrographical, biological, biogeochemical and chemical variables for use in satellite calibration/validation studies, as well as a long-term transect time series of the region. The 35-year portion of GNATS includes temperature, salinity, chlorophyll and nutrient measurements by C. Yentsch and D. Phinney (Bigelow Lab; started late 70’s) and C. Boyd (Dalhousie; started early 80’s) as well as MARMAP observations near the transect over the years. We began making more extensive measurements along the same transect in 1998 aboard the Scotia Prince ferry. We now use a combination of satellite, shipboard and autonomous underwater vehicle measurements to describe the GOM variability. GNATS measures all four parts of the marine carbon cycle: particulate organic carbon (POC), particulate inorganic carbon (PIC; calcite), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC; e.g., CO2, HCO3-, and CO3= plus alkalinity which can be used to derive pH). These four parts of the carbon cycle (including reservoirs and fluxes) provide insights about the major processes affecting the coastal ocean, from changes in productivity (i.e. POC variability through time associated with changes in hydrography, different phytoplankton functional groups, etc.), land-sea carbon transport (i.e. DOC and POC variability caused by major riverine flood events and droughts), and changes associated with ocean acidification (i.e. changes in DIC and PIC caused by changes in carbonate saturation). There is only time in this presentation to highlight a few of the results from the time series. We hypothesize that river runoff plays a key role with the physical, chemical, optical and biological oceanography of the GoM, including its carbon cycle. There have been some major changes in the environment (e.g. river runoff) that have had large effects on the lower end of the food web (e.g. a massive multi-year drop in primary production). I will show our results on variability of DIC, but these measurements were only funded two years ago, however, so it is too soon to say how observed GOM changes are explicitly related to OA. Our biological measurements focus on microbial populations up to phytoplankton; it is not unreasonable to hypothesize that the changes at the lower end of the food web are relevant to higher trophic levels and fisheries.
January 6, 2014- "Estuarine acidification: a conceptual discussion with examples" presented by Wei-Jun Cai, University of Delaware
Wei-Jun Cai will discuss how estuarine pH is affected by mixing between river and the anthropogenic CO2 enriched seawater and by respiration under various conditions (salinity, temperature and river endmmber alkalinity). A few rivers with different levels of weathering products and temperature are selected for the discussion. It is shown here that estuaries receiving low to moderate levels of weathering products exhibit maximum pH decrease in mid-salinity region as a result of anthropogenic CO2 intrusion. Such maximum pH decrease coincides with a mid-salinity minimum buffer zone. In addition, water column oxygen consumption can further depress pH for all simulated estuaries. Recognition of the estuarine minimum buffer zone may be important for studying estuarine calcifying organisms and pH-sensitive biogeochemical processes.
December 17, 2013- "Factors contributing to variability in pCO2 and calcite mineral saturation state in the coastal Gulf of Maine" presented by Joe Salisbury, UNH.
In light of high its economic value and observed recent changes in terrestrial discharge, ocean temperature, and circulation, the Gulf of Maine (GOM) is a critical region for understanding the impacts of chemical and physical variations upon marine resources. We begin by highlighting the unique features that make the coastal GOM particularly sensitive to acidification. We then survey several carbonate parameter time series in the GOM drawing special attention to the sub-daily measurements at the UNH-PMEL-NERACOOS mooring. These data are used to explore the causes of variation in pCO2 and Omega within the context of a time-evolving mass conservation process control model. Our preliminary results indicate: 1) first-order control imposed by variation in CO2 solubility and air-sea flux throughout the year, 2) the additive effects of net community production (NCP) and freshwater flux, particularly from April to June, 3) apparent summer NCP that proceeds in spite of assumed nutrient limitations, and 4) the importance of diffusion and vertical mixing during the latter half of the year. Each of the contributing factors exhibits considerable interannual variability arising from sensitivity to hydrological and physical processes that vary from year to year.
December 10, 2013- "Shipboard Surveys on the U.S. Northeast Shelf: Quantification of Variability in Carbonate Chemistry and Potential Biological Implications" presented by Nathan Rebuck, NOAA NMFS.
The dominant ecological and physical characteristics of the Northeast U.S. Shelf are well studied and modeled, however there are still many unknowns of carbonate variability in the region and the potential effects of acidification on the ecosystem and managed species. This presentation aims to evaluate the seasonal and regional variability in the dissolved inorganic carbon cycle and evaluate the changes in the past 30 years. Having quantified the variability, another objective is to demonstrate the complexity of the carbonate environment of the Northeast U.S. Shelf and how it must be accounted for when projecting the effects of ocean acidification (OA) on individual resource species. Using data collected as part of the NOAA Marine Resources Monitoring, Assessment, and Prediction (MARMAP) program from 1977-1987, a spatially explicit historical seasonal baseline is developed for the inorganic carbon components on the Northeast U.S. Shelf. Measurements from 2009-2010 from the NOAA Ecosystem Monitoring (EcoMon) program, NASA’s Climate Variability on Primary Productivity and Carbon Distributions in the Middle Atlantic Bight and Gulf of Maine Program (CliVEC), and other published studies are used to compare the regional change to documented global changes. Finally, qualitative comparison of four species with varying life histories and distributions are presented to demonstrate important considerations when evaluating the potential consequences of OA to in situ populations. Field monitoring efforts must be aware of the scales of natural variability inherent in the system, and projections of impacts to resource species will need to isolate the acidification component most relevant to the species of interest.
December 3, 2013- "Ocean acidification along the East and Gulf coast of the USA" presented by Rik Wanninkhof, NOAA/AOML, Miami.
In response to the requirements of the Federal Ocean Acidification (OA) Research and Monitoring (FOARAM) Act the NOAA Ocean Acidification Program is determining patterns and trends of ocean acidification in the coastal oceans surrounding the USA. Here I’ll provide an overview of the regional efforts along the East and Gulf coasts utilizing ships of opportunity, moorings and dedicated research cruises with focus on the Northeast region. The requirements to meet key performance measure of determining the aragonite saturation state in the realm to 0.2 will be discussed. The talk will address the parameters that need to be measured to constrain the OA forcing. The spatial trends with emphasis on offshore/nearshore differences and the causes thereof will be described. Efforts to anticipate changes in ocean acidification trends will be outlined.
November 19, 2013- "Carbon Cycling on the Scotian Shelf, NW Atlantic" presented by Helmuth Thomas, Dalhousie University.
This presentation intends to describe the biogeochemical context for ocean acidification studies on the Scotian Shelf. The seasonality of the dominant processes, regulating surface ocean CO2 conditions, including pH, will be assessed as well as cross-shelf transports of CO2, acidity and nutrient, the latter ones exerting the “subsurface control” of CO2 air-sea fluxes and surface pH.
The seasonal variability of inorganic carbon in the surface waters of the Scotian Shelf region of the Canadian northwestern Atlantic Ocean was assessed using hourly measurements of the partial pressure of CO2 (pCO2), and hydrographic variables obtained by an autonomous moored instrument (44.3°N and 63.3°W). These measurements were complemented by seasonal shipboard sampling of dissolved inorganic carbon (DIC), total alkalinity (TA), and pCO2, at the mooring site, and over the larger spatial scale. Biological processes were found to be the dominant control on mixed-layer DIC, with the delivery of carbon-rich subsurface waters also playing an important role. The region acts as a net source of CO2 to the atmosphere at the annual scale, with a reversal of this trend occurring only during the diatom dominated spring phytoplankton bloom, when a pronounced undersaturation of the surface waters is reached for a short period. During that time, the pH is at its annual maximum (pH≈8.15), while the Aragonite saturation state reaches its minimum just before the onset of the spring bloom in late March. After of the spring bloom period, the competing effects of temperature and biology influence surface pCO2 in roughly equal magnitude. During that time carbon fixation is driven by the smaller phytoplankton size classes, which can grow in warmer, nutrient poor conditions. In the Scotian Shelf region the summertime population these numerically abundant small cells accounts for approximately 20% of annual carbon uptake. While after the collapse of the spring bloom the concurrent warming of the waters maintains fairly homogenous, and lowest pH (pH≈7.9) conditions, the Aragonite saturation reaches its maximum at the end of the summertime. With the help of lateral diffusion coefficients, established from Ra isotope studies, onshore gradients of CO2 and nutrient species yield onshore carbon, nutrient and hydrogen ion (H+) fluxes in subsurface waters, which in turn regulate surface pH and fuel the CO2 outgassing from the Scotian Shelf.
November 12, 2013- "Ocean Acidification of the Shelf Waters of NECAN: The marine inorganic carbon system along Atlantic and Gulf of Mexico coasts of the United States” presented by Zhaohui Aleck Wang, Associate Scientist, Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts.
Distributions of total alkalinity (TA), dissolved inorganic carbon (DIC), and other parameters relevant to the marine inorganic carbon system were investigated in shelf and adjacent ocean waters during a United States Gulf of Mexico and East Coast Carbon (GOMECC) cruise in July–August 2007. TA exhibited near-conservative behavior with respect to salinity. Shelf concentrations were generally high in southern waters (Gulf of Mexico and East Florida) and decreased northward from Georgia to the Gulf of Maine. DIC was less variable geographically and exhibited strongly nonconservative behavior. As a result, the ratio of TA to DIC generally decreased northward. The spatial patterns of other CO2 system parameters closely followed those of the TA:DIC ratio. All sampled shelf waters were supersaturated with respect to aragonite (saturation state ΩA > 1). The most intensely buffered and supersaturated waters (ΩA > 5.0) were in northern Gulf of Mexico river plume waters; the least intensely buffered and least supersaturated waters (ΩA < 1.3) were in the deep Gulf of Maine. Due to their relatively low pH, ΩA, and buffer intensity, waters of the northeastern U.S. shelves may be more susceptible to acidification pressures than are their southern counterparts. In the Mid-Atlantic Bight, alongshore mixing tended to increase DIC concentrations southward, but this effect was largely offset by the opposing effects of biogeochemical processing. At the southern New England shelf break, another productive, low pH area, cross-shelf exchange and biology may have significant impacts on carbonate chemistry. Long-term change in circulation and inputs may potentially have impacts on carbonate chemistry in the region.