Ocean Acidification of Estuaries and Coastal Waters
The chemistry of world’s oceans is undergoing rapid change. Excess CO2 from the burning of fossil fuels and deforestation is making its way into marine ecosystems where the water is becoming more acidic. While the chemistry of ocean acidification is well understood, the impacts to marine biota and their ecology are only now beginning to be appreciated. It is not clear how acidification will change physiological function, behavior, or the ecological interactions among animal and plant species. Most attention has focused on plankton and coral reefs, where acidification appears to alter their capacities to build calcium carbonate structures, yet nobody has been studying coastal waters or estuaries, where the effects of CO2 will likely be most rapid and acute. These ecosystems are among the most biologically productive on earth and maintain some of the most extensive and measurable ecosystem services of any on the planet (e.g., commercial and recreational fisheries, water purification, flood and storm surge protection, human recreation.) While most people are aware of CO2 as a greenhouse gas, few realize its global impact on our oceans. This experimental research aims to understand how this is affecting the biology and ecology of our coastal ecosystems.
Microscopic view of D-stage and umbo-stage oyster larvae.
Effects of Elevated CO2 in Estuaries:
Oceans have steadily absorbed 30% of all CO2 emitted by human activities during the last 200 years. Elevated CO2 concentrations in oceans (both off shore and inshore habitats) have lowered the pH of these water bodies. Low pH conditions reduce the availability of carbonate ions for shell building and production of other vital calcium carbonate structures. While many groups are studying fully marine ecosystems like coral reefs, SERC has specifically targeted its research on estuarine habitats and their biota. Estuaries, like the Chesapeake Bay, support some of the most productive and economically important fisheries in the world, but because of their low salinity, these habitats are more susceptible to acidification than the open ocean.
Some Important Characteristics of Estuaries:
- Shallower, lower salinity and have less total alkalinity (less buffered) than pelagic ocean
- Carbon flux is more complex than simple CO2 diffusion from the atmosphere (runoff, air pollution, regional geology, biogeochemistry)
- Aragonite under-saturation already occurs
- Acidification effects virtually unstudied
- Biological resilience is unknown (How do biota react to increased acidity and reduced CaCO3 saturation?)
Our investigations have already determined that calcification and growth rates of native Eastern oyster larvae are significantly reduced at elevated CO2, but that such effects are not uniform across species. Such species-specific responses to acidification suggest that elevated CO2 will have complex effects on estuarine ecosystems. We are developing experimental mesocosms that will enable us to modify local CO2 regimes in the field as a method for measuring the ecological responses to acidification. This ocean acidification research extends and complements SERC’s already renowned expertise in CO2 studies.
Bank of pH meters is part of our CO2 delivery and control system.
Hourly output from pH controllers over the course of 110 h.
Image analysis is used to measure the surface area of larval oysters.
Species-specific responses to elevated CO2 in growth and calcification between Eastern oysters (Crassostrea virginica) and Suminoe oysters (C. ariakensis).