Humans have had a significant influence on estuaries through land use change and increased use of fertilizers, causing proliferation of algal blooms, hypoxia, and presence of harmful microbes. Now, acidification due to myriad processes has been identified as a potential threat to many estuaries. In Texas estuaries for example, short-term acidification as a result of episodic hypoxia is a well-documented phenomenon. Unfortunately, a longer-term trend toward chronic acidification (decreasing alkalinity, pH) has now been observed. The alkalinity decrease is likely caused by a reduction in riverine alkalinity export due to precipitation declines under drought conditions and freshwater diversions for human consumption.
Based on our existing long-term data, we hypothesize that hydrology acts as a switch, where increased river flows cause hypoxia and short-term acidification due to increased loads of organic matter, whereas prolonged low flows cause long-term acidification due to reduced loads of riverine alkalinity and calcification. In urbanized, wastewater-influenced systems, we hypothesize that reduced flows out of the watershed may lead to long-term acidification and chronic hypoxia due to reduced loads of riverine alkalinity and presence of low pH, high nutrient/organic matter wastewater.
To test our hypotheses, field and modeling studies are proposed to examine the relationships between estuarine acidification and other stressors (i.e., reduced freshwater inflow, hypoxia, and nutrient loading). Analysis of changes in ecosystem health and model calibration will be conducted based on long-term data. Mechanistic linkages between acidification, eutrophication and flow will be quantified through a field campaign. Chemical markers of organic matter sources fueling hypoxia will be determined. Future ecological states of the estuaries will be predicted using ecosystem models that account for projected changes in aforementioned parameters and ocean conditions based on IPCC estimates. The combination of prediction and consequence will be useful to multiple stakeholder groups.
The California Current System (CCS) is one of the most biologically productive regions of the world ocean, but seasonal upwelling of low oxygen and low-pH waters makes it particularly vulnerable to even small additional reductions in O2 and/or pH, which have both been observed in recent decades. Three prominent coastal phenomena have been implicated in precisely these changes: 1) large scale acidification and deoxygenation of the ocean associated with climate warming, 2) natural climate variability, and 3) anthropogenic pollution of coastal waters, especially from nutrient discharge and deposition. The relative importance of these drivers has not been systematically evaluated, and yet is critical information in any cost-effective strategy to manage coastal resources at local scales. Disentangling the magnitude and interaction of these different ecosystem stresses requites an integrated systems modeling approach that is carefully validated against available datasets.
The goals of this project are three-fold: 1) develop an ocean hypoxia and acidifcation (OHA) model of the CCS (Baja California to British Columbia), comprising the circulation, biogeochemical cycles, and lower-trophic ecosystem of the CCS, with regional downscaling in the Southern California Bight, Central Coast, and the Oregon Coast; 2) use the model to understand the relative contributions of natural climate variability, anthropogenically induced climate change, and anthropogenic inputs on the status and trends of OHA in the CCS; and 3) transmit these findings to coastal zone mangers and help them explore the implications for marine resource management and pollution control.
In terms of the commercial value of its shellfish and its importance as a finfish breeding ground, the western Gulf of Maine (GOM) is certainly one of the most valuable ecosystems in the United States. Because over 80% of organisms landed in the GOM must utilize calcium carbonate during certain critical life stages, the effects of ocean acidification (OA) on ecosystems are a topic of increasing regional concern. This notion was accentuated by recent demands from marine industry stakeholders and the State Legislature in Maine who convened an Ocean Acidification Commission to study and mitigate the effects of OA. By nature of its cool temperatures and copious freshwater subsidies from both remote and local origins, the western GOM may be particularly sensitive to future acidification stresses (Salisbury et al, 2008; Wang et al, 2013). With the goals of 1) providing data critical for climate studies and local decision support, and 2) understanding of regional processes affecting acidification, we propose to maintain data collection efforts at and proximal to UNH-PMEL acidification buoy. We will deploy, maintain and recover the buoy and its suite of instruments that provide quality oceanographic and carbonate system data. We will supplement these activities with seasonal cruises that map surface regional pCO2 and several surface variables supplemented with hydrographic and optical profiles at six stations along the UNH Wilkinson Basin Line (aka Portsmouth Line), which runs orthogonal to the coast. This in turn will be supplemented with ancillary bottle sampling and all will be used in research aimed at understanding processes controlling the dynamically evolving carbonate system in the western GOM.
The Ecosystem Monitoring program of the Northeast Fisheries Science Center conducts four dedicated cruises per year covering the entire extent of the Northeast United States (NEUS). NOAA OAP provides funding for the processing of dissolved inorganic carbon (DIC) and total alkalinity (TAlk ) samples from two Ecosystem Monitoring cruises. As part of these cruises, water samples have been taken at a subset of locations and at a range of depths. The depth-discrete nature of this sampling is very important and provides data to complement the more intensive surface sampling conducted by the pCO2 sensors. These samples are used to measure DIC and TAlk and their analyses are conducted by AOML. In addition, samples for among lab comparisons have been collected. Nutrient samples are also taken and are analyzed at University of Maine.
Initially, these samples will be used for an analysis comparing the extent of ocean acidification on the NEUS compared to the late 1970's. Subsequently, these samples will be used to provide continued monitoring of the state of ocean acidification. In addition, these samples will be used to better understand the relationship between carbonate chemistry and nutrient speciation on the NEUS. While interpretation of this data is complex, a consolidated analysis is being undertaken to develop an “Ocean Acidification Indicator” for the Northeast Shelf. This metric will provide resource managers and vested stakeholders a concise interpretation of current and near-term expected conditions of acidification in the region. This project also coordinates and cooperates with a number of other regional partners in an attempt to fulfill the regional monitoring vision of National OA Plan.
NOAA academic partners Salisbury and Cai will organize and lead a 34-days cruise covering 12 transects of the U.S. and Canadian coast oceans from Nova Scotia in the north to the Gulf of Maine, Long Island Sound, Mid-Atlantic and Southern Bight regions, ending with a transect off of mid Florida. This cruise will serve as a synoptic characterization of the marine carbonate parameters of the coastal ocean with increased coverage in nearshore areas that have not surveyed in the previous cruises and subsurface dynamics that are not captured from using buoyed assets or ships of opportunity. The climate quality data from these cruises provide an important link to the Global Ocean Acidification Network (GOAN) effort, and serves as a start of a long-term record of dynamics and processes controlling Ocean Acidification (OA) on the coastal shelves. To this end there is an increasing focus on these cruises to perform rate measurements (e.g. NPP/NEP/NEC) for validation measurements of autonomous assets and buoyed assets, for algorithm development utilizing remotely sensed signals that are used to characterize saturation states, and to project the future state of ocean acidification in the project area.