1. Sediment characteristics and temperatures as pre-requisites to population
success of Mya arenaria.
Madeline Macfarlane
Abstract- Populations of the economically valuable soft shell clam, Mya arenaria,
are subjected to increasing seawater temperatures along the east coast. The current
study was conducted to identify potential habitats that are most conducive to a high
animal survival rate for future reseeding efforts. Environmental characterizations
were conducted by evaluating historical seawater temperatures and gathering
sediments from sites along the Delmarva Peninsula. Sediments collected from the
southernmost distribution of Mya arenaria were taken at different depths at each
site. Samples were analyzed for grain size and organic/inorganic matter. The
investigation determined that the values at various depths provided a significant
difference in organic and inorganic matter, but not for grain size. Greenbackville
consistently displayed the highest organic content ideal for sediment dwelling filter
feeders, while Queens Sound showed the highest amount of silt/clay. Queens Sound
and Greenbackville have opposing environments that enable Mya arenaria to
survive in, indicating that an inversely proportionate ratio of silt/clay to % organic
matter may be a preferred environment. Habitats of Mya arenaria vary widely from
sandy to rich in silt/clay and organic matter. More important than sediment
characteristics are the increasing seawater temperatures along the southernmost
distribution limit that will potentially inhibit reseeding efforts.

2. 1. Introduction
The soft-shell clam, Mya arenaria is native to North America, it has been a
reliable source of income for local fisherman; however, since the 1980’s the
annual harvest has drastically declined in New England and the Chesapeake
Bay Area. This has led to a decline in seasonal and full-time jobs. Harvesting
efforts for these clams are often made through environmentally detrimental
methods such as escalator dredges. Mya arenaria is a burrowing soft-shell
clam that is found in mainly brackish waters, estuaries, and marine habitats.
Generally, in the environments, it can be found in the upper intertidal to
lower intertidal, subtidal, and even deep waters up to 190m beneath the
seawater surface. It can be found as deep as 30cm below the sediment
surface and as shallow as 20cm. A sand-mud mixture of sediment is
preferred because anything too rough may limit its ability burrow and lead to
damage of its thin shell. Several characteristics of the habitat of Mya arenaria
were measured to allow us to understand the feasibility of survival of a cold-
water clam that is challenged by increasing seawater temperatures. This
understanding will be important for location and timing of future reseeding
efforts in Virginia.
2. Materials and methods
To determine seawater temperatures, the use of The National Oceanographic
and Atmospheric Association (noaa) was implemented. NOAA makes data
available from individual buoys along the southeast region that was

3. concentrated on. Specifically, Northeast buoys WELM1 (Wells, Maine) and
44013(BOSTON 16 NM East of Boston, MA) were compared to Southeast
buoys KPTV (Kiptopeke, VA) and WAHV2 (Wachapreague, VA). Seawater
temperatures were collected from 2005-2015 for a total of ten years of data.
Each temperature set was averaged per month. Other characteristics such as
grain and organic content of sediment, dissolved oxygen content, salinity and
pH of seawater were measured at six different sites along the coast of
Virginia (Greenbackville, Queens Sound, Wishart Pt, Old Boat Launch, Guard
Shore and Saxis beach). The sediment samples collected at these sites were
sampled at three different depths of 0-10cm, 10-20cm, and 20-30cm. In
order to preserve samples, they were frozen, and then thawed out in
preparation to be dried. To determine sediment contents, sediment samples
were dried for 76 hours at 70°C followed by ashing in a muffle furnace at
600°C for 4 hour. Sediments were weighed before and after each treatment
and the results calculated. To determine grain sizes, after drying, sediment
samples were sieved in filters as big as 60 then, 80, 100, 150, 200, 325, and as
small as 400.

4. 3. Results
Figure 1. New England buoys
Figure 2. Eastern Shore buoys
In figures 1 and figure 2, NOAA buoys indicated that seawater temperatures
in New England (buoys WELM1and 44013) were significantly lower (p<0.01)
between May and October compared to temperatures along the Eastern
Shore (buoys KPTV and WAHV2). Average seawater temperatures at all
locations have increased by 0.8 °C since 2005. Specifically, in the months of
0
10
20
30
J F M A M J J A S O N D
0
10
20
30
J F M A M J J A S O N D
AverageSeawaterTemperatures(°C)
AverageSeawaterTemperatures(°C)

5. May through October, temperatures in eastern shore all reached well above
the living temperature range for Mya arenaria.
Figure 3. Organic sediment along the Delmarva Peninsula at 0-10cm
Figure 4. Organic sediment along the Delmarva Peninsula at 10-20cm
Figure 5. Organic sediment along the Delmarva Peninsula at 20-30cm
0
7
14
sep oct nov dec jan mar
0-10cm
0
7
14
nov dec jan mar
10-20cm
0
7
14
nov dec jan mar
20-30cm
Guard shore
Saxis
Greenbackville
Old boat
Queens sound
Wishart pt

6. In figure 3-5, Greenbackville showed an increase in organic matter as depth
increased in November and December. Figure 3 shows an increase in organic
matter for Wishart Part at 0-10cm, but as the depths increased, Wishart Pt.
showed a reduction in organic content that was uniform throughout the
months.
Figure 6. Sediment sizes along the Delmarva Peninsula
Figure 7. Sediment sizes along the Delmarva Peninsula
Figure 6 and 7 show that the winter months showed a significant increase in
silt/clay sediment most likely due to deposition easily moved silt particles
during the more intense winter tides.
0
10
20
sep oct nov dec jan mar
Guard shore
Saxis
Greenbackville
Old boat
Queens sound
Wishart pt
Silt/clayinsediment(%)
70
85
100
sep oct nov dec jan mar
%sand or larger
Sandorlargerinsediment(%)

7. 4. Discussion
The cause and affect of increasing seawater temperatures still remain to be
accurately described and factors involved identified. It is concluded; however, that
the increase in seawater temperatures is forcing Mya arenaria to redistribute
further up north from their southernmost distribution. As for sediment
characterization, Queens Sound and Greenbackville have opposing environments
that both enable Mya arenaria to survive in, indicating that an inversely
proportionate ratio of silt/clay to % organic matter may be a preferred environment
of animal success. In addition, the current study also showed that during the winter
months, the sediment composition changed drastically at sites such as Guard Shore,
Saxis Beach and Queens Sound. This range of habitat characterization from
sandy/pebble environments to silt/clay demonstrates the range of habitats Mya
arenaria is able to survive in. For future reseeding efforts, it is important to
determine the most feasible environment in order to achieve the most success of
these future animal deployments. Overall, this experiment further expanded the
knowledge of the type of habitat that will provide most success for these animals as
well as provided further evidence that seawater temperatures are on the rise over
the past 10 years. These results should be taken into further consideration to more
distinctly develop and understand the effects of seawater temperatures and habitats
on the success of Mya arenaria.

8. Works Cited
Abraham, B., & Dillon, P. (1986). Species Profiles: Life Histories and
Environmental Requirements of Coastal Fishes and Invertebrates
(Mid-Atlantic).