Habitat description
Primarily acidic, nutrient-poor, groundwater fed ponds with fluctuating water levels driven by precipitation and evapotranspiration patterns. Although most Coastal Plain Ponds (CPPs) do not have permanent inlets or outlets, some larger ponds may have stream outflows, but still experience groundwater-mediated water level fluctuations. Formed in glacial outwash plains or glacial lake beds dominated by sand and gravel deposits, CPPs are concentrated in Cape Cod and southeastern MA and at fewer inland sites in the Connecticut River watershed. CPP’s can occur in clusters tied to a single groundwater source or aquifer. CPP’s are quite variable in their physical features (i.e., morphometry) ranging in surface area, basin slope, mean/max depths, and shoreline shape. This contributes to variable shore and basin substrates with sand, gravel, cobble, or organic bottoms where plant matter accumulates. The mix of physical features, water quality, and natural water level fluctuations sets the stage for the assembly of distinct, rare, and rich plant and invertebrate communities found within this freshwater habitat type.
Associated habitat types
- Barrens: Pitch Pine-Scrub Oak Shrubland, Oak - Pitch Pine Forest/Woodland
- Hydrologically may relate to small coastal plain stream, acidic shrub swamp.
Characteristic communities and species
Pondshore and aquatic communities may shift and vary in size and composition from year to year, dependent on seasonal and annual water level fluctuations. Plant communities of the gently sloping shore follow a typical zonation from dry to inundated. The upper shoreline is often characterized by tree Oaks and Pitch Pine, bordered by a narrow shrub zone of Highbush Blueberry, Sweet Pepperbush, and Greenbrier. In low water years, a very pronounced zonation of emergent herbaceous vegetation occurs and may include grasses, sedges, and wildflowers of state and regional significance such as Torrey’s Beak-Sedge, Thread-leaved Sundew, New England Boneset, and Plymouth Gentian. In high water years, only a few emergent plants such as Bayonet Rush, Robbin’s Spike-sedge, and floating leaved aquatic plants including Pondweed and White or Yellow Water-lily are visible. Larger CPP’s with fish populations (i.e., waterbodies typically with surface outflows), can harbor relatively rich freshwater mussel assemblages including species of conservation concern such as the Tidewater Mucket, Eastern Pondmussel, Triangle Floater, and Alewife Floater. Other mussel species include Eastern Lampmussel, Alewife Floater, Eastern Floater, and Eastern Elliptio. CPP’s also harbor rich dragonfly and damselfly assemblages with several species endemic to the northeast region. Several Bluet (e.g., Enallagma) damselflies specialize in this habitat type including Pine Barrens Bluet, Scarlet Bluet, Attenuated Bluet (all state conservation priorities), New England Bluet, Little Bluet, and Atlantic Bluet. Dragonfly species almost exclusively observed in CPP’s include Comet Darner, Common Sanddragon, Blue Corporal, Golden-winged Skimmer, and Martha’s Pennant among others.
Associated Fauna
Waterfowl, Migratory Shorebirds, Freshwater Turtles including the Plymouth Red-bellied Turtle, Warmwater Fish, and Osprey.
Ecological processes
Seasonal and interannual water level fluctuations driven by groundwater flux, and seasonal precipitation and evapotranspiration events are major drivers of plant zonation in distinct rings around the pondshore from the upland edge to the submerged aquatic zone. Water levels are typically lower by late summer and fall supporting wider zones of emergent herbaceous vegetation. Water levels reach high marks typically in the winter and spring when ice scour and wind/wave action also act upon substrates and maintain open sandy substrates occupied by specialized coastal plain flora adapted to the harsh growing conditions and infertile sandy soils. Several of the specialized and regionally rare plants which occur here are considered stress tolerant with low competitive abilities. They do not compete well with other native plants in more fertile habitats and are adapted to irregular disturbance regimes (long periods of inundation and occasional fire). For example, several species are insectivorous adapted to low nutrient conditions, some have long-lived seeds that germinate only during periods of low water or after fire, and others are slow growing perennials forming small rosettes which allow them to withstand wave action and remain submerged under water for long periods until water levels recede and growing conditions are suitable for flowering and fruiting. Many coastal plain ponds occur within the barrens landscape and have a history of historic fire as documented in fossil pollen studies conducted in southeastern Massachusetts. The careful reintroduction of prescribed fire in this setting is warranted.
Threats
Water level stabilization and eutrophication are major threats to coastal plain pond habitats whose flora depend on irregular water level fluctuations, infertile substrates, and low competition from other plants. Increases in summer droughts, winter precipitation, and sea level rise associated with climate change will influence CPP water level regimes. Increased surface air temperature combined with enhanced nutrient input from anthropogenic pondshore and watershed activities, may increase the probability of harmful algal blooms. CPP’s will respond differently to climate change based on their water clarity, depth, surface area, and volume.
Pondshore development, (hard/armored pondshore), off-road vehicles, human water demand, excessive wave action from boats, invasive plants (Grey Willow, Common Reed) and bivalves (Asian Clam), eutrophication, cyanobacteria blooms, nutrient input to groundwater via agriculture, cranberry bogs, anthropogenic winter water level drawdowns, herbicide and pesticide runoff, excessive herbicide use within ponds, trampling from excessive pedestrian activity.
Restoration & management recommendations
Relevance, Scale, and General Effort
Globally restricted habitat and natural communities. Decision questions to help partners decide whether, where, and when management is appropriate. at what scale restoration is meaningful for the community group, how landscape context should be considered for the group, and what general commitment can be expected?
- Pond scale
- Watershed scale
- Aquifer scale - CPP’s can be concentrated in clusters
- Massachusetts contains the most CPP’s found in New England making CPP management efforts critical for regional conservation.
- Environmental variables to consider to maximize restore/management success
Management
- Water Quality and Quantity Restoration:
- Maintain and restore natural hydrology and variable water level regimes to the extent possible. Determine how ground and surface water moves through the wetland ecosystem and within the watershed with the assistance of hydrologists and restoration ecologists. Remove derelict impoundments and historical ditches. Avoid excessive long-term drawdown and/or flooding. Avoid activities that would harden pond substrates or alter wetland habitats. Reroute trails and roads around wetlands and wetland buffer zones.
- Establish long term monitoring of water level fluctuations to evaluate effects of climate change. Balance human water demands with ecological needs to sustain CPP ecosystem integrity in anticipation of climate change driven drought, storm events, and sea-level rise. Working with a hydrologist is critical to understand a particular site and the proper techniques to restore the water levels.
- Maintain and restore water quality in these naturally nutrient poor ecosystems. Restore nearshore natural vegetation buffers and reduce storm-water run-off, road drainage, and nutrient inputs such as lawn and agricultural fertilizers, salt, pesticides, and animal waste from grazing Canada Geese and Horses. Work with pondshore neighbors and local authorities to develop other best management practices to reduce stormwater impacts and eutrophication.
- Invasive Plant Control: The primary species of concern are Common Reed (Phragmites australis) and Grey Willow (Salix cinerea). However, many of the invasive species known to occur in Massachusetts can be present and adversely affect these communities; even species that are generally considered to be indicators of terrestrial environments. The careful application of herbicide is the most effective way to treat nearly all invasive species occurrences, though it should be expected that it will take several years of treatment to completely eradicate any established invasive occurrences due to persistent seedbanks and the clonal nature of certain species. It should also be noted that the continued presence of invasive species may be an indicator of an underlying stressor such as altered hydrology or unnatural chemical inputs, and therefore addressing both the invasive species and the underlying stressors is critical to restoring the long-term viability of a site.
- Access control: Control access, relocate trails, and refrain from pond shore disturbances such as raking vegetation and illegal off-road vehicular use which increase potential pathways for invasive plants, destroy vegetation, and compact soil substrates.
- Prescribed Fire: Reintroduce prescribed fire within appropriate coastal plain pondshores and adjacent terrestrial buffers associated with barren restoration and management efforts. Prescribed fire may be employed to improve habitat conditions for fire dependent pondshore herbaceous plants, to remove thatch and debris associated with invasive species control efforts, improve nesting habitat for wildlife, and to control woody understory vegetation encroaching on pondshores.
Examples
- Myles Standish State Forest
- Nickerson State Park
- Hyannis Ponds Wildlife Management Area
Additional resources
Cape Cod Freshwater Ponds Restoration Projects
Sorrie, B. A. 1994. Coastal Plain Ponds in New England. Biological Conservation 68:225 – 233.
Smith, S. M., and K. C. Medeiros. 2019. Recent groundwater and lake-stage trends in Cape Cod National Seashore: relationships with sea level rise, precipitation, and air temperature. Journal of Water and Climate Change 10.4:953 – 967.
Perales, K. M., C. L. Hein, N. R. Lottig, M. J. Vander Zanden. 2020. Lake water level response to drought in a lake-rich region explained by lake and landscape characteristics. Canadian Journal of Fisheries and Aquatic Science 77:1836-1845.