Ecology of the Bay
The foundation of South Portage Bay's ecology is a peat bog that has formed over thousands of years. Much of the bog has been filled and converted to the Montlake Playfield, however, portions remain along the forested edge that provide a rich diversity of habitat for birds and wildlife. There is even a beaver lodge that you can see right from the shoreline! The beavers are very active and create multiple canals that promote further biodiversity. Challenges include diversion of streams that used to feed the peat bog, peat being pushed out by the playfield, previous invasive water plants, and struggle for plants to thrive in mudflat regions.
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Let's Talk Peat!
Benefits:
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Major carbon sequestration and storage benefits
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Has flood reducing capabilities and can filter water, acts like a sponge
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Can encourage biodiversity even though it is considered poor in nutrients
Disadvantages:
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Poor foundation material that is prone to settlement
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Can push outwards when pressured by fill
Image from SDCI mapping website
Birds Galore!
South Portage Bay is home to over 85 bird and waterfowl species, regularly observed by birding groups. Many of the birds are protected by the Migratory Bird Treaty Act.
Photo taken by Eric Kowalczyk 2018
Photo taken by Eric Kowalczyk 2016
Photo taken by Bill Butler 2018
Lily Pads
Lily Pad coverage in 2018, prior to treatment. (Photo from Google Earth)
Lily Pad coverage in 2020, during treatment. (Photo from Google Earth)
Too Much of a Good Thing...
Lily pads had an extensive coverage within South Portage Bay from the early 2000's up until 2020. The lily pads would often reach their peak coverage around late spring through to early fall. Due to this extreme coverage, oxygen was depleted in the water, fish presence declined, and they created a "dead zone" that would lead to a buildup of organic matter. In order to solve this ecological issue, the Friends of South Portage Bay volunteer group collaborated with Washington State Department of Ecology and the County Weed Board to get the lily pads treated. Future management is required, the challenge being how do we continue treating them in an ecologically ethical way?
The Cattail Marsh
In the past, the shoreline was characterized by the cattail marsh, and the extent was quite large. In recent years, we have noticed that these ecosystems have retreated. More importantly, this started happening around the time the herbicide was used to treat the lily pads. Another factor may be due to Nutria (treated from 2008-2013). The Nutria would frequently feed on the cattail marsh, and it would be seen drifting out into the bay. Cattail marshes are important to wetland ecosystems as they are able to remove pollutants. We are left wondering, if cattail marshes are capable of spreading their seeds and replanting in multiple regions, why haven't they made a comeback in the bay?
Cattail marsh extent represented in three different years: yellow is our control from 2002, orange is before lily pad treatment in 2018, and green is present day (2025)