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How Will Atlantic Surfclams Fare in a Changing Ocean?

April 18, 2022

Molly Roberts takes us behind the scenes of research on carbonate chemistry effects on the growth of this iconic species off Cape Cod.

A pair of researchers work together, one of them sitting in a small boat. Further away, a pair of researchers stand in ankle-deep water with equipment. The sun sets over the submerged sandbar in the background. NOAA Fisheries and student researchers collect seawater samples and measure environmental conditions in Barnstable Bay, Massachusetts. Credit: NOAA Fisheries/Ben Tuttle

Where does the Atlantic surfclam grow the fastest? How will this species respond to global change, including ocean acidification, over the long term? These questions drive us to study surfclam growth around Cape Cod, Massachusetts.

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Small surfclam shells and a pair of calipers, showing the length of the shell being measured is about 5.6 millimeters.
Surfclams ranging from 5 to 16 millimeters collected from Provincetown on Cape Cod, Massachusetts. Credit: NOAA Fisheries/Matt Poach

March was a busy month at the Northeast Fisheries Sciences Center’s Milford Laboratory. Our team has been working to set up an experiment we’ve been planning all winter. Now that the ice has melted, we are ready.

Since last summer, we've been visiting a number of sites on Cape Cod. At each site we look for surfclams and sample the seawater. We’re interested in the environmental conditions that the clams live in, such as the water they pull through their mantles to filter feed. We also look at the water they’re exposed to within the sand, called sediment pore-water. We hope to find out if their growth rate correlates with the chemistry of the sediment they burrow into.

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Female scientist wearing an orange life vest and knit hat stands in shallow water beside a small boat with four Massachusetts Maritime Academy students, all wearing jackets and waders. Water and the sunset make up the background.
Massachusetts Maritime Academy students (right to left) Ben Tuttle, Shannen Allen, and Grace Calvert work with us to sample seawater and surfclams to bring back to the lab. Credit: NOAA Fisheries / Emily Roberts

Massachusetts Maritime Academy students are a major part of our team. Along with their capable boating skills, these students bring their enthusiasm for environmental chemistry and marine operations.

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Scientist wearing boots, waders, and an orange jacket rakes the sand for surfclams at low tide in a tidal marsh.
Research chemist Matt Poach raking for clams in Chatham, Massachusetts, an area we are monitoring. The clams collected are measured and aged for our study. Credit: NOAA Fisheries/Emily Roberts

This March we prepared for a transplant experiment in which we will grow two subspecies of surfclams in enclosures. This will help us to better understand the role of the environment versus population on their growth. To better understand the role of the environment on growth, we will compare the growth of the northern subspecies at different sites. At one southern Cape Cod site that has a large population of the southern subspecies we will also compare the growth of the two subspecies. 

wo side-by-side images of clam shells inside plastic buckets. The bucket on the left contains white fragments of surfclam shell, while the one on the right contains ground-up shell called hash.
Surfclam shell (left) is ground up to shell hash (right) that will be used in the transplant experiment. Credit: NOAA Fisheries/Emily Roberts

Meanwhile, I’ve been crushing surfclam shell into small (less than 4 millimeter) pieces. We will mix the shell into the sand within the enclosures. We think adding this calcium carbonate shell may change the chemistry of the water between the grains of sand.

One side effect of fossil fuel pollution is known as ocean acidification. When carbon dioxide in the atmosphere from fossil fuels dissolves into seawater, this increases the acidity of the seawater, making it less basic (or alkaline). We think that adding shell might alleviate stress on the surfclams caused by this change in chemistry of the seawater.

Three researchers stand in ankle-deep water wearing jackets, waders, and boots. The background is a sandbar and cloudy sky.
Researchers on a tidal flat discussing how to anchor artificial enclosures that will contain surfclams growing in the sandy bottom. Left to right: NOAA researchers Matt Poach and Daniel Hennen, and Massachusetts Maritime Academy student Shannen Allen). Credit: NOAA Fisheries/Emily Roberts

We made it out into the field to install our enclosures, but unfortunately our anchors did not arrive on time. This setback gave us time to test deploying the enclosures at the different sites before the final installation, which will include 32 enclosures at each site.

Two researchers stand on a beach in ankle deep water wearing jackets, waders, and boots.
Matt Poach (right) shows off his prowess in installing a surfclam cage deep in the sediment of a tidal flat. My method of using a sledgehammer was sadly not as effective (Emily Roberts, left). Shellfish aquaculture plots are in the background. Credit: NOAA Fisheries/Shannen Allen
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Plastic mesh sewn around an 8 inch metal cylinder with miscellaneous lab equipment in the background.
To make the enclosures in which clams will grow, we sew plastic mesh around 8 inch metal cylinders. This setup was designed by research chemists George Sennefelder and Matt Poach of the Milford Laboratory. Credit: NOAA Fisheries/Emily Roberts

The transplant experiment will last 9 to 12 months and include at least three sampling periods. We’ll study the growth of the surfclams and monitor their environment during this time. We’ll use the data we collect to validate a model of surfclam growth and reproduction under different ocean conditions. We then plan to use this model to predict the effect of ocean warming and ocean acidification on surfclam growth at these sites.

 A student researcher poses on a tidal flat while holding a mesh surfclam growth enclosure, while another researcher pulls a cart in the background. The background is a beach and cloudy sky.
Completing a day of field research with surfclams on Cape Cod, Massachusetts. Credit: NOAA Fisheries / Emily Roberts

The end!

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