By Dr Jen Karberg, Research Program Supervisor

30 miles off the mainland, anchored in the Atlantic Ocean, Nantucketer’s know better than many how water shapes our natural world. Wetlands are the places where water comes in contact with land and surrounded by the ocean and our many harbors, it can be easy to think that salt water wetlands dominate our landscape. Lately, we’ve spent a lot of time talk about our coastal salt water wetlands and coastal resilience. But turning inland, Nantucket’s freshwater wetlands are just as important for the diversity, beauty, and resilience of the island.

This week, World Wetlands Day 2021 celebrated the variety and importance of freshwater wetlands – the life of the world! (visit the website below, the home page graphic is stunning)

Water is the key ingredient to create wetlands – the kind of water, the amount of water and the seasonality of water determine the plants and soils and animals that fill that wetland and together those things define the type of wetland. Freshwater can come from three place: rainwater which is usually a little bit acidic, surface water running over and just under the soil and groundwater moving up from reservoirs through the soil. Nantucket’s glacial history means that our island is home to so many different kinds of fascinating freshwater wetlands. So lets take a little tour through a few!

When walking through the Middle Moors, take a peak into the valleys and low spots. The Moors are dotted with depressions of all sizes. These kettleholes are the legacy of blocks of glacial ice left on the landscape by retreating glaciers. Sometimes the depressions made by these melting blocks were just that, low swales in the rolling landscape. Some of them were low enough to intersect the groundwater turning into coastal plain ponds. Other ice blocks were actually covered with a layer of clay soil when the glacier retreated, and as the block melted, that clay settled down into the depression and created a bowl to capture rain and surface water – these are the true bogs!

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Kettle hole glacial formation over time

The coastal plain pond: typically has an open water pond surrounded by a ring of wetland vegetation. Fed by groundwater, pond water levels rise and fall seasonally. Low water years expose long wet soils and plant seeds that quickly germinate and flower and seed – taking advantage of a rare window for reproduction. Some of Nantucket’s rarest plants can be found along Coastal plain pondshores, only showing up every 5-10 years. Almanac Pond and the Pout Ponds are some of the more well known coastal plain ponds in the Moors.

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Almanac Pond in the Spring, moderate high water levels.

The true bog or poor fen: on Nantucket, mentioning bogs usually makes one think of bright red cranberries. But the wetland ecologist definition of a bog is very specific. Bogs are very unique wetlands whose water comes almost exclusively from rainwater, which makes bogs very acidic and very nutrient poor. Very few plants can grow and thrive in this environment. Sphagnum moss is one of those plants that prefers an acidic place and bog surfaces are typically covered in mounds of Sphagnum moss. Carnivorous plants thrive on low Sphagnum hummocks, capturing and eating insects to get nutrients not found in these wetlands. Read our Carnivorous Plant blog post to learn about all the different insect eating plants on Nantucket – we have a few! Catching a glimpse of these true bogs can be hard as it usually involves wading through knee to waist-deep water but if you’re feeling adventurous search out Donut Pond on a map.

Cross section of a raised bog, like Donut Bog. Precipitation comes into the wetland and a clay layer at the bottom of the kettle hole holds in the water and prevents groundwater from entering.
Cross section of a raised bog, like Donut Bog. Precipitation comes into the wetland and a clay layer at the bottom of the kettle hole holds in the water and prevents groundwater from entering, reducing nutrients and creating the perfect environment for carnivorous plants.

Red Maple Sphagnum swamps: wander over to the northeastern corner of the island and it feels like you’ve been transported off island. Heavy clay and shallow groundwater in the Squam/Wauwinet area of the island make for extensive swamp wetlands. By definition a swamp is a wetland dominated by trees and on Nantucket that tree is often the red maple. Sweeping and magestic trunks often rise from damp Sphagnum soil or even standing water with pools and squishy soil in between. The swamps might be harder for humans to take a walk through but they are much loved by wildlife, home to spotted turtles and salamanders and small mammals, harrier hawks and deer – Squam Swamp is a sweetly diverse spot, even in the winter!

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A stop along the NCF Squam Swamp guided trail.

This is just a snapshot of some of the freshwater wetlands on Nantucket, all connected to freshwater moving from beneath and above the island. To see and learn more, join NCF’s Neil Foley on a video walk through the wetlands of Nantucket and then get out and take a wander yourself! Let the ACKTrails app guide you around to all these special places.