Measuring Life Beneath the Surface: OARS’ 2025 Aquatic Biomass Surveys

October 10, 2025

OARS River Log | By Heather Conkerton, OARS’ Ecological Restoration Coordinator | Published Oct 10, 2025

If you’ve ever paddled through a patch of water lilies or spotted tall stands of pickerelweed along the shoreline, you’ve seen part of what makes our rivers alive. This past August, OARS 3 Rivers conducted aquatic biomass surveys in three dam impoundments across the watershed to better understand the health and balance of these underwater plant communities.

Why Biomass Matters

Aquatic biomass surveys measure the total amount of plant life growing in a section of river or ponded area. Tracking these measurements over time helps scientists assess ecosystem health—revealing how nutrients, flow conditions, and invasive species shape aquatic habitats.

Healthy levels of aquatic vegetation support fish, invertebrates, and birds, while helping stabilize sediments and keep oxygen levels balanced. Too much growth, or the wrong kinds of plants, can indicate problems such as nutrient pollution or restricted water flow.

A section of river dense with aquatic vegetation—a sign of high biomass—provides habitat for wildlife like this great blue heron in the background. Monitoring these plant communities helps OARS track ecosystem balance and identify areas where invasive growth may be impacting river health.

What We Found

During this year’s surveys, OARS staff documented a mix of native aquatic plants—essential components of a thriving river ecosystem—alongside a significant presence of invasive species common in dam impoundments. These invasive plants can outcompete native species, change water chemistry, and alter habitats for fish and invertebrates.

OARS Ecological Restoration Coordinator Heather Conkerton removes invasive water chestnut from a dam impoundment during the 2025 biomass surveys. These fast-spreading plants can blanket the water’s surface, blocking sunlight and disrupting the natural balance of river ecosystems.

Early detection and tracking of these invaders are key to understanding where management or restoration is needed most.

Guiding Future River Health

The data gathered from these surveys will help guide future restoration and conservation work, including invasive species management, dam removal planning, and habitat restoration. Over time, this information paints a clearer picture of how our rivers are responding to both natural changes and human impacts.

By continuing to measure what grows beneath the surface, OARS is working to ensure that our rivers remain healthy, balanced, and full of life—from the tiniest algae to the largest fish.

River Log

~30%

of the SuAsCo rivers watershed is wetlands, crucial for wildlife habitat and water quality

~30%

of water samples in the SuAsCo rivers watershed contain PFAS, leading to increased monitoring and remediation by local authorities and environmental groups

~70%

of dams in the SuAsCo watershed are over a century old, requiring extensive upkeep and presenting obstacles to river restoration and fish passage

>40%

of the land within the watershed is publicly accessible, offering recreational opportunities such as hiking, boating, and birdwatching to the community

~15%

of the land in the SuAsCo rivers watershed is covered by impervious surfaces such as roads, rooftops, and parking lots. This contributes to stormwater runoff and water pollution issues

>40%

of the land within the Sudbury, Assabet, and Concord rivers watershed is publicly accessible, providing endless opportunities for paddling, hiking, and wildlife exploration.