Environmental Monitoring

Our approach to conservation is ecosystem-based.

We use the natural environment to solve the problems humans have created. We have implemented six innovative programs that focus on mitigating contamination and restoring the bay for fishing and recreational use.


Tracking the health of Quahog Bay


Fishing for plastics


Creating a market for the invasive green crab


Water Quality Monitoring Sites

Each week, the QBC team collects water samples at nine different sites in Quahog Bay. Data is collected from the surface waters at each location and then processed and analyzed in our lab. We collect measurements of temperature, salinity, pH, and dissolved oxygen. In addition, we monitor levels of bacteria and various species of phytoplankton in order to track harmful algal blooms (HABs), more commonly known as “red tide” (see below for more information).

What do these measurements tell us about water quality?

Temperature – Research has shown that the Gulf of Maine is warming 99% faster than any other world ocean. We collect temperature data in Quahog Bay to monitor local trends and the seasonal turnover of the water column.

Salinity – Salinity is the amount of dissolved salts in water. On average, the salinity of seawater is 35 parts per thousand (ppt), meaning there are 35 grams of dissolved salts in every one liter. Freshwater has a salinity of 0 ppt. After a heavy rainstorm (a large freshwater influence), we often observe lower salinity values in the surface waters.

pH – The scale by which “acidity” is measured. Acidity indicates the concentration of hydrogen ions in a liquid. Biological, physical, and geological processes all naturally affect acidity levels, but human influences such as CO2 pollution can also impact ocean pH. A drop in pH indicates an increase in ocean acidity, which can affect shellfish by inhibiting calcification (skeleton/shell building).

pH scale with examples of common solutions and their pH values (NOAA)

Dissolved Oxygen (DO) – The amount of oxygen present (dissolved) in water. All aquatic animals need DO to breathe. Lower oxygen levels often occur in bottom waters where organic matter is decomposing and microorganisms are consuming DO. DO levels below 3 milligrams per liter (mg/L) raise concern for poor water quality that cannot sustain many species of marine life.

Bacteria – Bacteria are a natural part of microbiology. We test for the presence of disease-causing organisms or pathogenic bacteria, which indicate that the water has been contaminated with the fecal material of humans or other animals.

Phytoplankton – Phytoplankton are the foundation of the marine food web. Cell counts of different species of phytoplankton inform us about the abundance of each species in the seawater. Many species bloom in the spring and fall, but some are toxic to humans and have been categorized as harmful algal blooms (HABs) and/or red tide (see below for more information).

Red Tide – Maine’s “red tide” is monitored by The Marine Biotoxin Monitoring Program which is administered by the Department’s Bureau of Public Health. It uses the standards outlined in the National Shellfish Sanitation Program (NSSP) to monitor levels of PSP (“Red Tide”) and other marine biotoxins in the shellfish of the State of Maine and is regularly checked to prevent any shellfish illness.

For more information from the Department of Marine Resources concerning Marine Biotoxin Monitoring, visit their website: https://www.maine.gov/dmr/fisheries/shellfish/bureau-of-public-health-programs/marine-biotoxin-monitoring

We have identified six OBD systems and have removed and replaced four of them. We are currently negotiating with the last two property owners to update their systems.

In 2018,  QBC team was trained by DMR Public Health Officials to be phytoplankton volunteers. We collect water samples in the spring, summer, and fall using field microscopes to identify toxic phytoplankton species. Volunteers work independently after receiving training and equipment needed to collect samples.


Since 2014, we have removed hundreds of cubic yards of marine debris from the bay— enough fishing gear, Styrofoam, bottles, cigarette butts, tires, and even car batteries to fill massive dumpsters.

If we see trash on the water or on the shore, we go get it. But we don’t stop there. We have certified divers on staff who use SCUBA gear to find and remove trash from the seabed, and we have a boat with a mechanical lift to haul heavy debris to the surface.

We also work to educate the community about the impact of trash on the health and beauty of the Quahog Bay.

2021 Maine Debris RemovalFigure 1. Number of dumpsters filled each month throughout 2021 in Quahog Bay. One dumpster is equivalent to 4 cubic yards.

Figure 2. Number of dumpsters filled each month throughout 2020 in Quahog Bay. One dumpster is equivalent to 4 cubic yards.

Figure 3. Number of dumpsters filled each month throughout 2019 in Quahog Bay. One dumpster is equivalent to 4 cubic yards.


Green Crab Harvesting Sites

The European green crab (Carcinus maenas) is one of the most aggressive invasive predators in coastal marine systems, having established itself on every continent except Antarctica. The green crab came to the Atlantic coast of North America nearly 200 years ago, and today is one of the most ecologically and economically damaging predators. Our cold waters had kept their population in check, but now, with the Gulf of Maine warming 99% faster than any other world ocean, the green crab populations have rapidly expanded in size and range.

Green crabs consume nearly everything in their paths, destroying mussel beds, clam flats, and scallop stocks. This has devastating impact on local fishers who depend on shellfish production for their livelihood. In addition, green crabs slice through eelgrass habitat and burrow in salt marshes, causing increased erosion in bays and estuaries.

As the forces of climate change continue to amplify this threat, new strategies are needed to mitigate its ecological and socioeconomic impacts. QBC has developed a localized management plan that investigates and collects data on green crab population dynamics. We will use that information to increase our catch per unit effort (CPUE) and learn more about the species. Our management plan includes a) Prevention and Containment; b) Detection and Forecasting; c) Removal, Control, and Mitigation; and d) Data Management and Education.

QBC’s management plan takes a three-phase approach that aims to solve the green crab crisis.

Phase I: Remove Green Crabs. It is highly unlikely that we will ever be able to eradicate them entirely. Yet, to alleviate the pressure that green crabs have put on our ecosystem, we want to remove as many as we can. As the largest green crab harvester in Maine, QBC has developed harvesting methods that remove thousands of pounds of green crab each year.

Phase II: Research Green Crabs. We collect data every time we fish for green crab. We track their abundance in Quahog Bay and population trends from May through November, creating a database for monitoring year to year.

Phase III: Develop a Lucrative Fishery. Our goal is to create a viable product that would provide a new source of economic opportunity for fishers and coastal communities. Utilizing an invasive species to diversify fisheries’ resources may ultimately enhance the future resiliency of Maine’s coastal communities. This could serve as a model for how to mitigate and adapt to the ecological and socioeconomic impacts of climate-driven change.

QBC has partnered with local fishers to investigate the viability of green crab as a fertilizer. We are partnering with businesses and other stakeholders in our marine ecosystem to identify and develop other ideas for eradicating the green crab.

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