Oshawa Second Marsh: Exposed!

Drained marsh sets the stage for a dramatic reveal

Oshawa Second Marsh is now a dry, exposed mud flat. The drawdown is part of a process that mimics the natural conditions that historically occurred in Lake Ontario. ©DUC

Don’t let its dry, cracked, mudflats fool you. Oshawa Second Marsh is coming to life. With a little patience, time and care, this ugly duckling of a wetland will slowly emerge as a beautiful swan.

You don’t have to look far to see the transformation in progress.

Oshawa Second Marsh is one of the few coastal wetlands left in the GTA. Poor water quality, invasive carp and low biodiversity left this critical marsh in need of a little TLC. That’s why DUC, Friends of Second Marsh, City of Oshawa, and Central Lake Ontario Conservation Authority (CLOCA), have stepped-up to give Second Marsh a makeover.

Early this spring, the partners began a drawdown at the marsh using an onsite pumping system. This de-watering process mimics the natural conditions that historically occurred in Lake Ontario during alternating periods of high and low water levels. The process improves marsh health, enhances biodiversity, improves water quality and maintains a healthy wetland ecosystem for wildlife and migrating birds.

Fully drained as of late spring, the marsh is now a dry, exposed mudflat.

Although the wetland appears desolate at first, the sunshine has worked wonders. The seeds buried in the mudflats have begun to germinate, providing a carpet of native wetland plants like cattails, soft stem bulrush, arrowhead and smartweed.

According to Heather Brooks, Director, Watershed Planning and Natural Heritage for CLOCA, the mudflats and renewed vegetation has brought with it many welcomed visitors, including a variety of shorebirds, leopard frogs and American toads.

“Having diverse and abundant plant life provides habitat for endangered and threatened species like least bittern and king rail” Brooks explains. “Also, aquatic vegetation is a fabulous filter, improving water quality, which appeals to spawning pike and other fish species.

The new marsh vegetation germinating on the mudflat is key to a healthy wetland. When the marsh is eventually refilled with water, this vegetation will provide habitat, food and cover for wildlife. In the meantime, the exposed mudflat is attracting a number of rarely seen bird species to the area, which has made Second Marsh a hot spot for local bird watchers.

Oshawa Second Marsh vegetation
The drawdown will help the marsh’s vegetation.
©DUC

According to DUC biologist Dave McLachlin, people have seen wading birds like sandpipers and other shorebirds that migrate from the Arctic including lesser yellowlegs, Wilson’s phalarope and least sandpiper. The rarely observed American avocet and the endangered piping plover have also made recent appearances. In fact, 305 bird species have been spotted.

“Although nearly all the water is gone, it’s simply teeming with wildlife,” says McLachlin.

While a Mecca for migrating birds, the current state of Second Marsh is great news for local birds as well.  Remaining shallow water and mud areas have created a great buffet for ducks, geese, great blue herons and other resident bird species.

“As the restoration process continues we can expect to see more birds using the area,” continues McLachlin. “Visitors to the marsh will continue to have a great opportunity to view the wildlife in action. However, it’s important to respect the needs of the birds.”

McLachlin explains that for migrating birds coming from the Arctic, Second Marsh is an important resting and feeding stop on their long journeys. Any constant disruption that interferes with energy replenishment could affect the birds’ survival. By keeping your distance to avoid disrupting the wildlife, everyone will eventually get to witness the beauty that the drawdown will achieve.

Bird at Oshawa Second Marsh
Visitors to Oshawa Second Marsh can expect to see more birds visiting the area.
©DUC

By respecting the bird’s space, new aquatic plants will also be able to grow in the best conditions. Watching from a distance and not infringing on this critical growth stage, will give these aquatic plants time to develop before the wetland is re-flooded.

“A lot of planning, time and effort has gone into creating the perfect condition for growth and germination of the aquatic plants,” says Brooks. “By watching from afar we can ensure that the plants do not get trampled and the ecosystem has the opportunity to continue to restore itself.”

The next phase of the drawdown will begin in late summer 2016, when a shallow level of water will be returned to the marsh. By 2018, it’s expected that water levels will be back to normal and water quality and overall marsh health will be restored.  And so, this tale of transformation continues. But like the swan, once mature this project will be one of the most beautiful of them all.

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