Bay Experience
Underwater Critters in your Backyard Bay
Objectives:
• Understand the concepts of diversity and adaptation
• Become familiar with both native and invasive species of Narragansett Bay
Background Information:
Narragansett Bay is home to many different marine creatures including fish, crabs,
shellfish, and even seals. We will focus on critter habitats, food webs, and
adaptations.
Activity:
We will explore the concepts of diversity, adaptations, food webs and habitats
through the use of live animals. We will discuss each animal, showing how each
part of the animal is important to its survival. You will also learn how to
differentiate between genders and discover how important adaptations and
diversity of species are to animals that live in Narragansett Bay and to the food
web.
Blue mussels (Mytilus edulis)They moor themselves with
tough Bissell threads, usually in
dense masses, and compete
with barnacles to cover
intertidal rocks and pilings. In
prime locations, full growth
occurs in approximately one
year, but in other locations it
can take up to three. Like all
bivalves, they are filter feeders.
These are the kinds of mussels
that are eaten in restaurants.
They are also eaten by sea
stars.
Ribbed mussels (Geukensia
demissaGeukensia
demissaGeukensia demissa)Usually found in salt marshes,
buried in the mucky peat among
the roots of salt marsh grasses.
Very rugged; can handle high
temperatures and salinity
double that of sea water. These
are inedible.
Periwinkles (Littorina spp.)- The
most abundant snails in New
England. These are abundant
inter-tidally, and will attach to
anything solid. They can
withstand long periods of being
out of the water. They are
herbivores, and eat mostly algae
attached to rocks. They are
widely eaten in Europe; steamed
or quick boiled in salt water, then
eaten with butter.
Oyster drills (Urosalpinx cinerea)They are found in the intertidal to
sub-tidal zone, down to about 50
feet (15 m). Although they like
brackish water, they will not
willingly go to places with salinity
less than 15 ppt. These snails drill
a small hole with their radula, and
suck out the soft parts of the
shellfish as food. As the name
would imply, oysters are their
favorite food. Shell-fishermen
have, in certain areas, moved
their oyster farms closer to fresh
water inputs to avoid these
predators from eating their stocks
Channeled whelks (Busycon
canaliculatum)- Channeled
whelks like to remain in water
all the time, living in the
subtidal zone down to about 60
feet (18 m). Their egg capsules
grow in long strings and can
often be found washed up on
the beach. They often eat other
gastropods by using their hard
shells to chip away at other
gastropod casings. They are the
largest sea snails on the
Northwest Atlantic coast, and
are eaten in the Italian dish
Scungili despite their rubbery
texture. They are also called
“conch” shells.
Hermit Crabs (Pagurus spp.)Smaller species are found residing
in periwinkle or oyster drill shells.
Larger species are found in moon
snail or whelk shells. Hermit crabs
only come out of their shells when
they find a suitable replacement as
they outgrow their shell, or if they
are extremely stressed. Hermit
crabs should never be pulled out of
their shells as they will quickly
become prey.
Spider crabs (Libinia
emarginata)- These are also
called decorator crabs or
gardener crabs, because they
plant algae all over their bodies.
They have extremely long legs
for their body size, and are
pretty docile despite their scary
looks. You can tell if a crab is
male or female by flipping it
over so the carapace is facing
the ground, and seeing whether
the bottom of the crab is a big
circular shape (female, good for
holding eggs) or a narrower
lighthouse shape (male).
Lobsters (Homarus
americanus)- Lobsters have
two claws; a pincher claw
and a crushers claw. They
are scavengers but will also
eat shellfish and crabs using
their claws. Males are rigid,
and females are softer and
feathery. They can
regenerate claws, legs, and
antennae. They can swim
using the large muscle in
their tail, which propels
them in a backward motion,
and is also the part of the
lobster most people like to
eat the most. People also
eat their claws and their
livers, called tomalley.
Sea stars (Asterias spp.)- All are
predators. They eat bivalves,
especially oysters, by grabbing onto
them with their tube feet, or podia,
prying them open, and everting their
stomachs into the bivalve where it is
digested. In turn, bottom feeding
fishes eat them. They can regenerate
their legs, and have 5 eyes, one at the
tip of each leg, which see mainly just
shadows. The orange dot in the
center of the disc is the madroporite.
This is where the sea star lets water
in and out, which it uses to receive
oxygen and structure in its body.
They can tolerate brackish water to
salinities of 15-20 ppt.
Purple Sea Urchins (Arbacia
punctulata)- They are
protected from predators by
the many spines that cover
their bodies, which is also
how they move. They are
omnivores, eating seaweed as
well as sedentary
invertebrates and scavenging
upon dead organisms. Their
mouth is on their underside,
and the internal area where it
sits is called “Aristotle’s
lantern”.
What types of DIVERSE critters will we find?
Are these critters NATIVE or INVASIVE?
What might this tell us about the Bay?
How do these critters ADAPT to this
ENVIRONMENT?
What FOOD WEBS will we see in
Narragansett Bay?
Background Information:
A Rocky Shore is an area where the wave action is so
strong that sand and mud can not settle; leaving a
coastline of exposed rock. As one might expect, a rock
pounded by crashing waves is a difficult place to live for
many animals and plants. Organisms must be able to
withstand changes in tides, pounding waves, extremes of
temperature and salinity and aerial assault by gulls.
Temperature extremes are mainly due to shallow waters,
which are much easier to warm by the sun or cool by the
wind. Salinity extremes are primarily due to evaporation
of water in tide pools, which causes some tide pools to
reach salinities much higher than ocean water.
As a result to these extreme conditions only organisms
specifically adapted to the rocky shore are able to live there.
Adaptations are features of an organism’s body that allow it to
live comfortably in its habitat. For example, the shells of
mussels, periwinkles, dog whelks, oyster drills, hermit crabs and
the exoskeletons of green and Asian shore crabs protect those
animals from the crashing waves. Rock-weed, kelp, and Irish
moss are seaweeds that have holdfasts to anchor them to the
rocks. These holdfasts are not roots, but instead serve to
anchor the plant in place in the face of the power of waves and
tides. Sea stars use their tube feet for the same purpose, to
keep them attached to rocks. Green and Asian shore crabs use
their coloring to camouflage themselves into the rocks and
seaweed in which they hide. Mussels, barnacles, periwinkles,
and slipper shells all open or come out of their shells to eat
when the tide is in, but are able to close their bodies completely
inside their shell to conserve water when the tide is out. These
are just a few of the many adaptations of the most common
rocky shore animals.
Sub-tidal InterHigh tide Splash
zone
tidal zone zone
zone
Always
Covered by
covered by
water part of
water, even at the day.
low tide.
Only covered
during high
tide.
Sometimes
splashed by
sea water, but
never
submerged.
Activity:
You will collect plants and animals ~
at least 10 things that are alive or
once were alive. After the collection
period you will use field guides to
identify your organisms. Each group
will present one organism to the
whole group.
Questions to Consider
•What are the differences between upper inter-tidal and
lower inter-tidal pools? Why did you find these
differences?
•What generalizations can you make about tide pools
closer to the water versus tide pools further away?
•What plants and animals are common on the rocky shore?
Where do they generally live?
•What adaptations do these plants and animals have to
help them live in such a harsh environment?
Biodiversity trawl
“What organisms can be found at the bottom of the bay?”
Activity:
You will research this question by studying field guides and then
create a hypothesis about the abundance and diversity these
organisms.
To test your hypothesis, you will conduct a trawl aboard the Save
the Bay vessel Alletta Morris.
After, you will analyze the data collected.
Objectives: At the end of this program learners will be able to:
* Use field guides to identify organisms
* Collect data and analyze data
* Calculate the percentages for each organism collected on
during the trawl.
BEFORE THE TRAWL…
QUESTION: “What organisms can be
found at the bottom of the bay?”
YOUR HYPOTHESIS:
What do you think?
WHILE COLLECTING PLANTS AND
ANIMALS…
RECORD DATA:
Type of organism Number/
Size found
Description or
drawing of
organism
Other notes
AFTER COLLECTING PLANTS AND ANIMALS…
ANALYZE DATA:
Which types of organisms did you mostly find today?
DRAW A CONCLUSION:
What does the presence of these animals tell us about the
health of the Bay?
Additional Observations: