“Profiles in Environmentalism” is a recurring segment on our blog where we shine a light on the dedicated people working to preserve the world around them. Big or small, local or national, every environmental organization works towards the same goal: providing a greener world for future generations.

In their natural state, estuaries are one of the most ecologically productive areas on Earth. The mixing of salt water and freshwater in the tidal basin delivers vast amounts of nutrients, making it an ideal habitat for many species. In fact, estuaries provide habitats for 75% of America’s commercial fish catch, as well as providing a vital source of food for migratory birds and local wildlife. They also act as natural flood barriers by absorbing storm surges and flood waters, helping to protect both the wildlife and properties that reside along their embankments.

Despite their ecological importance, many of the world’s estuaries are under threat. With nearly 60% of the world’s population living near estuaries or on the coast, these areas face a variety of threats from human activity including storm water and agricultural runoff, over-fishing, loss of wetlands, and industrial pollution.

A small sliver of the Delaware Estuary, where water meets land.

A small sliver of the Delaware Estuary, where water meets land.

Fortunately, there are many dedicated groups out there that work to restore and preserve these critical habitats. One such group is the Partnership for the Delaware Estuary (PDE), one of 28 organizations across the country that are looking out for the health of our nation’s estuaries. As part of their mission, the PDE studies the keystone species of the Delaware Estuary, and engages with the coastal communities of New Jersey, Pennsylvania, and Delaware to encourage participation in protecting their estuary.

All You Need Are Mussels

One group of animals that are of particular importance to the PDE, and estuaries the world over, is freshwater mussels; bottom-feeders that environmental scientists frequently use to determine the health of riverine and marine ecosystems. Mussels feed on plankton and other microorganisms by filtering the water around them, with some species capable of filtering up to 10 gallons of water per day. This natural filtering action of mussels and other shellfish, such as oysters, helps keep waterways clean. But if a stream or river becomes over-saturated with contaminants, or even nutrients (in the case of agricultural and sewage runoff), mussel populations decline or disappear altogether, signaling that the broader ecosystem is in danger.

Behold the power of mussels oysters!

Waterways that are heavily contaminated can kill off entire populations of mussels, essentially kicking the bottom out from under the local food chain. This unfortunate fate has befallen many species of mussels in the Delaware Estuary; of the 12 native mussel species that existed in the Delaware 100 years ago, only one or two of these species remains. The loss of so many mussels has left many streams and creeks in the Delaware River watershed completely devoid of them, severely reducing the habitability of these ecosystems.

In 2011, the PDE made the first steps toward revitalizing these creeks by transplanting adult mussels from one waterway to another. The PDE transplanted two different species of mussels from the Delaware River and Ridley Creek and moved them to different reaches of both Ridley Creek and nearby Chester Creek, two areas where mussels have disappeared over the last several decades. Each mussel was tagged with a transponder to in order to track their location, making subsequent population surveys easier. These mussels continue to be tracked in order to gain more insight into the various environmental conditions that best support populations of shellfish.

It is hoped that further research along these lines will allow the PDE and other estuary programs to learn the ideal growth conditions for all sorts of mussels and other shellfish. But as is the case with many scientific projects, getting the necessary funding for this research is a constant struggle.

Looking Towards the Future

Though much of the PDE’s work is grounded in improving the present state of the estuary, it is not blind to the risks posed by climate change. In 2010 the PDE worked with the EPA to assess what the greatest impacts of climate change will be on the habitats and communities of the Delaware Estuary as part of its Climate Ready Estuaries Program. Through this partnership, the PDE identified wetlands and tidal marshes as some of the most crucial areas to preserve in preparation of climate change.

Various estimates pinpoint sea levels rising anywhere between 0.9-3.2 feet (IPCC) and 2.6-5.6 feet (PDE) by the end of the 21st century. In either estimation, the Delaware Estuary will experience heavy erosion along its banks, threatening to destroy the tidal marshes and wetlands that act as natural buffers to storm surges and flash flooding.

The PDE’s solution has been to mitigate the erosion of existing marshes and build them up in advance of rising sea levels. This has traditionally been done by placing retaining walls along embankments that act as a physical barrier between the tide and the banks of the estuary. But these walls are not permanent solutions. For one thing, they cut off land dwelling animals from the water, restricting their ability to forage for food or establish new habitats. These walls are also not entirely waterproof and in some cases can cause the sediment directly behind the bulkhead to erode.


Members of the PDE lay down mats to increase sediment capture.

Members of the PDE lay down mats to increase sediment capture.

Instead, the PDE has focused on shaping “living shorelines” that gently slope into the water so that fish, birds, turtles, and other animals have a natural connection between land and water. These natural shorelines are enhanced by placing shellfish and plants along the riverbanks. The shellfish keep the water clean and fertilize the marsh plants, which in turn help to capture and anchor sediment so that it doesn’t go out with the tide. Over time, a natural marsh is retained, providing a modicum of protection from the effects of a rising sea.

Bringing Communities Together, Upstream and Downstream

Of course, the Partnership could not accomplish all that it does without the participation of the people who live around the Delaware Estuary. You can find their volunteers wading into the water from Philadelphia all the way down to Cape Henlopen, conducting surveys of mussel populations and helping to construct natural shorelines. Together, these volunteers gather invaluable data that informs where the organization’s limited resources are needed most and where they can have the greatest impact.

The efforts of the Partnership are having a tremendous impact on the health of the Delaware Estuary. And in the years to come, the organization expects to make the entire basin a place where people can recreate and take their families, providing a clean and vibrant habitat for humans and wildlife alike.