Ponds and Freshwater Wetlands Monitoring

Female scientists sits on a canoe on a large pond holding a plastic container. — Water samples are collected by Seashore scientists as part of the pond monitoring program.
NPS / Katy Perrault

If you've been to Cape Cod National Seashore, chances are you've been to the beach. In addition to the salty marine and estuarine environments, the Cape is also home to over 1000 freshwater ponds and many freshwater wetlands. Ponds and freshwater wetlands are affected by changing temperatures and precipitation patterns, air quality, and human activities which in turn affects the organisms that call these ecosystems home. Understanding these changes allows Seashore scientists to not only protect these important natural and recreational resources, but also the communities - both human and natural - that interact with them. This monitoring work as well as research about the kettle ponds are critically supported through partnerships, which are extremely important pieces of this and many monitoring programs across the National Park Service.

Within Ponds and Freshwater Wetlands, three vital signs are measured: kettle pond water quality, kettle pond vegetation, and vernal wetland vegetation. Related monitoring programs include the monitoring of air quality, hydrology, and estuarine and salt marsh ecosystems.

Kettle Ponds

There are over 1000 ponds on Cape Cod, large and small, which are part of ecologically complex systems of abiotic (non-living) and biotic (living) components including water, plants, fungi, and animals. These ponds were formed after the last glacial maxima (ice age) when blocks of ice left behind by the retreating ice sheet formed depressions in the landscape - called kettle holes - that later filled in with fresh groundwaters. Ponds formed in glacial soil have low buffering capacity (ability to withstand changes in pH) and naturally low concentrations of nutrients, which make them sensitive to atmospheric and environmental changes, such as changes in temperature, pH, and nutrients.

These ponds are unique, both from each other and from other ecosystems on the Cape and elsewhere, ranging in trophic status (the amount of biological productivity/living things they sustain) as well as the habitat they provide, creating a diversity that supports many native species - some rare or threatened in other areas of New England! This value has been widely recognized and the Massachusetts Natural Heritage Program has designated the kettle ponds of Cape Cod National Seashore as ecological, recreational, and aesthetic treasures for their biodiversity and rare species.

Due to their high sensitivity, ecological importance, and impacts of heavy recreational usage, Cape Cod National Seashore and partners prioritize monitoring for changes in these ecosystems, especially water quality.

Kettle Pond Water Quality

A scientist sits on a canoe on a pond holding an instrument in the water. — Park scientists and partners use an instrument called a Secchi desk and a special tube, which you can see in this aquatic ecology assistant's hand, to collect data on kettle pond turbidity (how much stuff is suspended in the water) by seeing how deep they can still see a disk.
NPS / Katy Perrault

Kettle pond water quality monitoring helps Cape Cod National Seashore and the surrounding communities to understand changes in trophic status, seasonal hydrologic processes, acidity, thermal structure (separation within the water by temperature that affects nutrient cycling and oxygenation). Human activities have also increased around ponds, in particular residential and recreational uses, which have led to increasing pollution from wastewater (additional phosphorus, nitrogen, and pharmaceuticals going into pond water), as well as extensive vegetation trampling and removal. The kettle pond water quality monitoring provides critical information to improve the visitor experience, ensure safe recreation, provide public health information, and ensure the health of these unique ecosystems.

In the spring, as the sun becomes stronger and air temperatures warm, the kettle ponds become stratified (layered). Think of a stratified pond like a multi-layer cake - when the air temperature warms, the surface of the pond becomes warmer and less dense, while the bottom remains cooler and denser, creating separated layers that don't mix (and neither do the nutrients and oxygen within them). They remain stratified until temperatures cool in fall when ponds turn over, mixing the waters and redistributing nutrients and oxygen throughout the water column. To track this process and gather data on pond water chemistry, clarity, quality, and level, the kettle ponds are monitored beginning in the early spring before stratification through fall turnover, which usually happens in the late fall.

How this is monitored:

Ponds are monitored from March to December (turn over) annually.

10 primary ponds representing all three trophic levels (oligotrophic, eutrophic, mesotrophic) are sampled biweekly; all 20 ponds are sampled once in spring, summer, and fall
- Paddle out in a canoe to a sampling station at the deepest point.
- Use a Secchi disk and EXOSonde to gather data on environmental parameters; collect water samples for lab analysis.
  - Environmental parameters: temperature, conductivity, dissolved oxygen, pH, anions, cations, nutrients, redox potential, alkalinity, transparency, light, chlorophyll, nitrogen, phosphorous
Spring: all 20 ponds are sampled.
- Provides data during the well-mixed period before stratification.
Summer: all 20 ponds are sampled.
- Provides data on the annual characterization of the degree of eutrophication and strongest stratification period.
Fall: all 20 ponds are sampled.
- Provides data during turnover (water column mixing with release of pond bottom phosphorus and nitrogen).

Long-term monitoring provides the best opportunity to assess changes, which can inform management decisions. Initial kettle pond water quality monitoring began in the 1970's and is one of the longest freshwater monitoring programs in the nation! From this decades-long monitoring data set, for example, scientists at the Seashore were able to learn about increasing pH and temperature and changing thermocline structure that have implications for pond food webs and harmful algal blooms. Air temperatures are rising, and with them so are pond temperatures. Furthermore, stratification is longer and stronger, creating more stressful ecological conditions for pond organisms. On the flip side, Seashore scientists were also able to see the positive impacts on pond acidity (less acidic pond waters), due to regulating environmentally detrimental components, such as the amount of pollutants going into the air, through national legislation.

The kettle pond water quality protocol and data packages are not currently available for public view. Below you can view a video taking you through how scientists monitor for kettle pond water quality.

Kettle Pond Vegetation

Another vital sign monitored by park scientists is pond vegetation. Many plant species that can be found at the ponds are listed as endangered, threatened, special concern, or watch list by the State of Massachusetts, which in conjunction with increasing impacts of human use and recreation such as trampling, erosion, urination by swimmers, and septic runoff, raise important reasons for monitoring vegetation at the ponds.

You can read more about pond vegetation monitoring in the documents below. Data packages are not available at this point.

Here you can find the monitoring documents available for kettle pond vegetation.

Source: NPS DataStore Collection 9714. To search for additional information, visit the NPS DataStore.

Vernal Ponds Vegetation

Vernal ponds vegetation is also monitored by park scientists. Vernal wetlands are wetlands that are seasonal, meaning they aren't always inundated with water, but when they are, shallow ponds are created. They're often covered with shallow water from winter to spring and then completely dry in summer and fall - you might have no idea they're a wetland depending on what time of year you visit! These conditions, although harsh, are uniquely suited to numerous rare plants and animals, making them important to understand and monitor.

You can learn more about vernal pond vegetation monitoring in the documents below. Data packages are not readily available at this time.

Here you can find our currently available vernal wetland vegetation monitoring documents.

Source: NPS DataStore Collection 9715. To search for additional information, visit the NPS DataStore.

Dune Slack Wetland Monitoring

In the dunes, especially around Province Lands, features of the topography create unique situations where freshwater interdunal wetlands, called dune slack wetlands, exist. These wetlands occur when wind blows away enough sand that the surface elevation in the area intersects with the groundwater table, creating "permanent" wetlands (they are around for at least 60 years, which is nothing in environmental time but quite a bit relative to our lifetimes). Water levels fluctuate rapidly in response to evapotranspiration (water released by plants during respiration) and precipitation, which is changing due to changes in Earth's atmosphere and climate.

As important refuges for plants species like insectivorous sundews and orchids, as well as many invertebrates and amphibians, these systems provide important benefits to the Seashore's inhabitants. They also provide water to larger mammals and stabilization of the ground, important to both dune slack wetland ecosystems and those that surround them. Despite their role, relatively little is known about dune slack wetlands, which monitoring helps address. Reliant on water tables that are strained by increasing human use in surrounding communities, impacts of sea level rise, and saltwater intrusion, understanding these systems is extremely important.

Here you can find available monitoring documents for dune slack wetlands!

Source: NPS DataStore Collection 9716. To search for additional information, visit the NPS DataStore.