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Photo Essay – Aquaculture and Acidification Project

Abigail selfie

Follow along in this photo essay as Woods Hole Sea Grant and Cape Cod Cooperative Extension respond to a question asked by members of the Massachusetts shellfish aquaculture industry. Lab studies show that shellfish exposed to acidic conditions will have poor growth and survival. Is this happening now in the waters of Cape Cod? Will oysters and quahogs exposed to varying acidic conditions in their natural environment also have differences in growth or survival? Or will other conditions in the environment like the amount of food available, balance out the effects of acidic water? Please click on each photo from left to right to learn all about this great project!

The Three Bays estuary in Barnstable is made up of Princes Cove, North Bay, Cotuit Bay and West Bay. Many shellfish aquaculture businesses and town recreational and commercial shellfishing beds are located in these bays.
Ocean and coastal acidification is an issue associated with climate change. Carbon dioxide in the air is absorbed by the ocean and causes changes in the chemistry. Lab studies have shown that if juvenile shellfish are exposed to water that is low in pH (acidic), their development and growth can be impaired.
The question that Woods Hole Sea Grant and Cape Cod Cooperative Extension wants to answer is – will oysters and quahogs exposed to varying acidic conditions in their natural environment also have differences in growth or survival? Or will other conditions in the environment like the amount of food available, balance out the effects of acidic water?
To test this, oysters and quahogs were grown in 5 sites from the northern most location at Princes Cove where there are high nutrients and low dissolved oxygen, to a site off of Oregon Beach where water quality improves because of flushing with Nantucket Sound waters.
The study began in June 2021 with a hatchery delivery of tiny oyster seed only 2-3mm long.
500 little oysters were placed in each one of these green bags. Each site got 3 bags placed into a wire mesh cage to keep out predators and prevent the bags from floating away.
These quahogs also started out at just 2-3 mm in length.
The quahogs were placed into boxes dug into the sediment and a net placed over them to protect them from predators. Each site got 3 boxes with 200 quahogs in each.
The water quality is measured by collecting samples in bottles, filtering out sediment, and bringing the samples back to the lab for analysis. The things being measured are salinity, dissolved oxygen, temperature, total alkalinity, dissolved inorganic carbon, nutrients, and the species of phytoplankton present.
Some of the water samples were collected with a piece of equipment called a Van Dorn sampler.
Every other week a sample of 50 oysters was removed from each bag and measured for length .
Every month the researchers counted how many oysters were alive and how many were dead.
From mid June to mid October the oysters grew from 3 to ~70 millimeters. That’s 2.7 inches!
On the opposite weeks one box of quahogs were dug up at each site and measured and counted.
The Center for Coastal Studies is a partner in this study and analyzed the nutrient samples in their lab in Provincetown.
Timing is important! Some days it was a rush to get all the field work done at low tide and collect all the water samples in time to meet their transport up to Provincetown!
With all these samples – labeling is very important.
By the end of the summer the oysters grew to almost legal size!
In October all of the quahog boxes were dug up and the quahogs were brought back to the lab. It took a long time to sort the quahogs from the sand and gravel!
The quahogs were weighed and measured for length and the live and dead were counted
In November all the oysters and the oyster cages were removed from the study sites.
The oysters were brought back to the lab…
…and the oysters were also weighed and measured.
Over the winter the researchers will be analyzing all the data collected but will be dreaming of Year 2 of the study and getting back out on the water in Three Bays.

Thank you to the Town of Barnstable Natural Resources Department, Center for Coastal Studies, Barnstable Clean Water Coalition and the Aquacultural Research Corporation for working on this project with us.

Posted in Announcements, Fisheries and Aquaculture, General Info