Chesapeake Bay Acidification
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4
acidification in Washington state waters, including processes at local and regional levels, and made
recommendations for how the state should respond to the observed conditions (Feely et al
.,
2012). The
panel identified several local and regional scale processes that exacerbate acidification, including: 1)
Seasonal upwelling of high CO
2
/low pH and nutrient-rich water from the deep ocean, a process that is
now enriched by anthropogenic carbon that was put into the atmosphere approximately a half century
ago; 2) Nutrient and carbon runoff at the land:sea interface, which can strongly affect biological
productivity, producing hypoxic conditions locally; and 3) Local upwind sources of CO
2
, and oxides of
nitrogen and sulfur, all of which can function as acids to reduce surface pH in coastal waters. Depth was
identified as an especially important characteristic of estuaries with respect to local acidifying processes.
With the exception of upwelling, Chesapeake Bay is subject to all of the same acidifying processes that
occur in west coast estuaries. Because Chesapeake Bay is a shallow estuary with high nutrient loading
and extensive muddy sediments, it supports rich biological productivity (photosynthesis and benthic
respiration) that strongly influences pCO
2
/pH patterns and dynamics. Land use patterns, including
shoreline and watershed habitat and development, affect Chesapeake Bay’s water quality (e.g., freshwater
riverine input, point and non-point sources). Although a lot of focus has been placed on nutrient loading
in the Bay, especially as it relates to eutrophication, far less attention has been paid to those parameters
that directly affect carbonate chemistry, such as the flux of total CO
2
(TCO
2
also referred to in this
document as dissolved inorganic carbon, DIC) and total alkalinity across the land:water interface, and
CO
2
flux across the atmosphere and bay water interface. Further, the effects of intertidal and subtidal
habitats, such as salt marshes and seagrasses, on local carbonate chemistry have not been investigated.
Lastly, the exchange of TCO
2
of the bay with the offshore ocean water is not known either.
The complex and dynamic nature of Chesapeake Bay is known to cause a high degree of spatial and
temporal variability in salinity, temperature, dissolved oxygen, turbidity and other measures of water
quality, which in turn shape the distribution of aquatic species in the Bay. In contrast, we know very little
about the spatial and temporal variation in carbonate chemistry parameters such as pCO
2
and pH.
Understanding how local-scale carbonate chemistry affects the distribution of species and ecosystem
services will inform better practices for managing natural resources (e.g., natural habitats and fisheries),
aquaculture inside and outside of hatcheries, and restoration of foundational species that build habitat
such as oysters, other shellfish, and seagrasses. Much of this local variation is driven by biological and
biogeochemical processes such as photosynthetic drawdown of CO
2
, benthic respiration by microbes and
macrofauna, tidal export of TCO
2
and total alkalinity from saltmarshes. A holistic understanding of the
biological and physical process operating at local and regional scales on carbonate chemistry can inform
where to site hatcheries, oyster hatcheries, and other management decisions.
Given the heterogeneous nature of Chesapeake Bay, an observing network that focuses on carbonate
chemistry will require highly resolved spatial density and temporal observations from shore-, vessel-, and
buoy-based sampling stations. Optimizing these measurements to provide accurate and reliable
information for the least effort is a key challenge that will require strong interdisciplinary collaborations
and leveraging of existing observing and research programs and assets. We advocate incorporating
observing efforts across the many biogeochemical features of Chesapeake Bay, with special focus on the
fluxes across environmental compartments (Fig. 1) to elucidate carbon chemistry dynamics. Additionally,
research should focus on the localized effects these fluxes and chemical dynamics have on surrounding
biota in order to understand current and future impacts.
