Estuaries in Flux: The Daily Drama of Oxygen and Acidity in Coastal Ecosystems.
What if the waters that teem with life by day became inhospitable graveyards by night?
In the warm months of May through October, researchers from Stony Brook University set out aboard the R/V Paumanok to study the waters of Long Island Sound and Jamaica Bay.
Their mission: to unravel the complex interplay of dissolved oxygen, carbon dioxide, and pH in these bustling coastal ecosystems.
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The scientists, led by Ryan B. Wallace and Christopher J. Gobler, deployed an arsenal of instruments to capture the estuaries’ chemical vital signs. A CTD-rosette system plumbed the depths, while sensors provided a continuous stream of data on oxygen, temperature, and acidity. Among their tools was a coulometer from UIC Inc., used to measure dissolved inorganic carbon with precision.
The data painted a picture of estuaries in flux.
Brief algal blooms saturated surface waters with oxygen, but these episodes were short-lived, giving way to longer periods of oxygen depletion and increasing acidity. In deeper waters, zones of dangerously low oxygen and high acidity persisted for weeks, often lurking beneath more hospitable surface waters.
Daily rhythms emerged through round-the-clock sampling.
Waters that were oxygen-rich and chemically balanced during daylight hours transformed under cover of darkness. By dawn, the same waters had become oxygen-poor and acidic, a nightly cycle driven by the respiration of countless organisms.
The implications of these findings are profound.
The levels of acidification observed – with pH dropping below 7.5 and carbon dioxide levels exceeding 2000 μatm – surpass projections for open ocean acidification.
Such conditions have been shown to impair the growth and survival of calcifying bivalves, crustaceans, and finfish in laboratory settings.
In Grassy Bay, a particularly troubled area, hypoxic and acidified conditions prevailed more than half the time from April to October. These persistent stressors could pose significant challenges for marine life and complicate ecosystem restoration efforts.
The researchers’ work reveals that while surface waters may appear hospitable during the day, nightly transitions to hypoxia and acidification create a challenging environment for marine organisms, especially in their early life stages. This dynamic interplay of chemistry and biology in estuaries like Long Island Sound and Jamaica Bay underscores the complexity of coastal ecosystems and the challenges they face in an era of environmental change.
As we look to the future, these findings suggest that estuarine management will need to account for both short-term fluctuations and long-term trends in oxygen and acidity.
The health of these vital coastal waters – and the diverse life they support – may well depend on our ability to understand and address these intertwined challenges.
