Climate Change in Delaware Bay

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Ted Williams wrote a piece this week for Yale Environment 360 on the impact climate change is having on the Delaware Bay. Although this estuary is much smaller than the Chesapeake Bay (782 square miles to the Chesapeake’s 64,299 square miles), the two watersheds have a lot in common, in terms of geographic location, features, and marine and shorebird species. The changes Williams sees occurring in Delaware Bay are either issues we are currently seeing in the Chesapeake, or could be a sign of changes to come.

The most dramatic change occurring in the Delaware Bay is the loss of tidal wetlands due to sea level rise and erosion. The watershed is losing an acre a day of its wetlands. With rate loss expected to increase, by 2100, 90% of these wetlands may be lost.

Wetland loss impacts lifecycle processes of several species. Atlantic menhaden larvae require tidal marshes. Ribbed mussels (an important filter feeder in the Bay) form tight-knit clusters in marshes; erosion makes the mussels more susceptible to predation.

Sea level rise contributes to beach erosion and shoreline tree loss. Horseshoe crabs, which use beaches in the Delaware Bay watershed as spawning grounds, are losing their grounds to sea level rise. Some shorebird species dependent on horseshoe crab eggs, such as the red knot, are at risk from these environmental changes.

Certain species in the Delaware Bay may see short-term benefits from climate change. With fewer freezes occurring, Delaware Bay oysters can survive in intertidal zones. However these now warmer zones are hosts to diseases (MSX and Dermo) and predators (oyster drills).

Warmer waters exacerbate pollution issues. Nutrients build up, dissolved oxygen can decrease, and algal blooms can increase in frequency.

The Chesapeake Bay is also experiencing shoreline loss and erosion. Places like Dameron Marsh and Hughlett Point in Virginia have been discussed here previously in terms of erosion and sea level rise. Naturally warmer waters in the Bay mean that diseases such as MSX and Dermo have been impacting native oysters for decades. It will be interesting to see how warmer waters -associated with climate change- host new or increased populations of pests/predators for our oysters. Ocean acidification may also be a concern. The changes occurring between species relationships, such as between Delaware’s red knot and horseshoe crab, will certainly be something to look out for in this watershed.

To read Ted Williams’ article, please visit e360.yale.edu.

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