Mapping and Monitoring

Cape Cod: Freshwater Systems


Quaking Bogs

Quaking bogs are wetlands that have formed across the surface of shallow ponds. These ponds are characterized by slow groundwater flow, which causes the pond water to be acidic and low in dissolved oxygen (DO). The roots and rhizomes of invading wetland plants form floating mats across the pond, which creates an unstable, "quaking" surface. Over time, leaves, stems and other organic matter may accumulate below the mat and stabilize it. Nutrients are slowly released into the bog by bacterial decomposition at the surface.

Depending on the availability of nutrients, degree of soil saturation, water pH and DO level in a given bog, the site may evolve into a marsh or swamp. Quaking bogs support rare bog plants, such as dragon's mouth orchid (Arethusa bulbosa), and few fruited sedge (Carex oligosperma).

The world's largest known quaking bog found on a barrier beach is in the Shank Painter Pond system in Provincetown. Bogs are threatened by land development, changes in water flow, and pollution from runoff.

Sphagnum Bogs

Sphagnum Bogs are rare wetlands that formed in wet depressions and have thick sphagnum mats and deep peat layers that are permeated by stagnant, acidic and mostly anoxic waters. The dominant plants of these bogs are herbaceous, low shrubs such as cranberry (Vaccinium macrocarpon) and leatherleaf (Chamaedaphne calyculata), as opposed to marshes and swamps, which are dominated by grasses and trees, respectively. The water quality inhibits decay, so fallen trees, pollen, or other organic material may remain preserved beneath the surface of the bog for thousands of years. Nutrients are locked up in the undecayed material, so growth conditions in the bog are nutrient-poor, and the bog plants are adapted accordingly.

The insectivorous pitcher plant (Sarracenia purpurea), and sundew (Drosera spp.), which obtain nutrients by trapping and digesting insects, are found in Cape Cod's sphagnum bogs. Some plants, such as dragon's mouth orchid (Arethusa bulbosa), and few fruited sedge (Carex oligosperma), are rare because they grow mainly in rare sphagnum bogs. Bogs are threatened by land development, changes in water flow, and pollution from runoff.

Cedar Swamps

Atlantic white cedar swamps are globally threatened ecosystems native only to isolated hollows in a 100-mile wide strip on the US Atlantic and Gulf coasts. They are characterized by saturated, acidic organic-peat soils, and dominated by Atlantic white cedar (Chamaecyparis thyoides). Abundant sphagnum mosses cover the cedar roots and the tea-colored, tannin-rich water. Atlantic white cedar only colonize open boggy areas because its seedling do not grow well in the shade. Common red maples will replace cedar.

Atlantic white cedar swamps are home to a variety of plants and wildlife, some rare, including: bushy sweet gale (Myrica gale), highbush blueberry (Vaccinium corymbosum), swamp azalea (Rhododendron viscosum), heartleaf twayblade (Listera cordata), spotted turtles (Clemmys guttata), and sharp-shinned hawks (Accipiter striatus). In fact, in Massachusetts, heartleaf twayblade is only found in one swamp on the Cape.

Swamps also act to buffer surrounding communities from flooding by holding large amounts of rainwater and spring runoff. This globally rare habitat was once abundant, but was largely destroyed, along with the rest of Cape Cod's native forests, for lumber, fuel, and through the conversion of land to agriculture. The largest cedar swamp remaining on the Cape (11.9 acres) is at Marconi Station in Wellfleet. There are few wetlands suitable for cedar colonization left on highly developed Cape Cod, and the current number and distribution of seed-producing cedars is low.

Remaining swamps are threatened by development, which may fill the wetland, or channel excessive runoff directly into a swamp, thereby drowning the cedars.