Posts Tagged ‘algae’

European Invaders: Periwinkles

Saturday, October 18th, 2008

As we explore the intertidal zone, that area between low and high tide where land and sea are locked in eternal battle, where life must confront pounding surf one moment alternating with barren exposure to rasping winds the next, where creatures are attacked by water predators half the time and land predators the rest of the day, where everything is drowned in brine at high tide and then soaked in rain at low, a harsh clime of extreme contrasts that change as quickly as New England’s weather; as we search this region we find one of its more common residents, the languid and familiar periwinkle (Littorina littorea).  Some scientist sure wanted us to remember where this critter came from with both genus and species derived from the Latin littoralis (or litoralis) meaning “of the shore.”

Periwinkles and Barnacles

My earliest memories of Cape Cod sealife are of periwinkles dotting the rocky sidewalls of the canal where my mom and dad brought me each Sunday to fish.  Back then fishing was less commercial, yet not purely recreational, either.  Yes, it was a break from the intense six-day, back-straining work week, but no excurision was successful unless you brought home food that would supplement household resources, especially for meatless Fridays.  And while fish were plentiful and Sunday after Sunday yielded flounder or cod or tautog or bass for the family table, there were days when the fish just “weren’t biting” and we had to look elsewhere on the food chain to meet our needs.

Blue Mussels

Next down our list were blue mussels that grew in large colonies on the old mud flats near the railroad bridge.  Back in those days few people ate mussels.  So, it’s amusing five decades later that you can’t read a seafood menu without mussels marinara or mussels something.  But if the tide was too high and our access to the flats was cut off, there was always one last food source to exploit: periwinkles.  They may have been small, but they were plentiful, very plentiful.  And no one, no one ate or even thought of eating periwinkles.  Yet, mom sauteed them in butter and garlic, then tossed them into her fresh spaghetti sauce for flavoring instead of pork or beef on meatless Fridays.  Many years later when I visited my parents and brought them out to dinner at a fancy Boston restaurant, I suggested to mom that she try the escargot, sauteed in garlic and butter, as an appetizer.  She looked at me as though she had raised a barbarian.  “Snails!  You want me to eat snails!”  I smiled, apologized and suggested the mussels marinara.

Periwinkle (Littorina littorea)

While an extremely common critter along our rocky shores, jetties, dock pilings and tidal pools, periwinkles are not native to North America.  They are an invasive species introduced into the Northeast perhaps sometime in the 19th century.  First documented in Nova Scotia in the mid-1800s, periwinkles can now be found in plentiful numbers up and down the Eastern Seaboard.  Whether they were brought to our shores deliberately as a favorite food of European settlers or they hitchhiked across from Europe in ballast water or clinging to creases in ship plankings, the method of their arrival is clouded in history.  They are consumed extensively in Europe today and are increasingly being harvested from New England shorelines.

The main body of this small, shell-covered snail is comprised of a large foot, head and mantle, covered with a protective operculum (see image above).  The operculum, a tough, horny “door” snaps the snail’s soft, vulnerable body into the shell during dry spells such as low tides. 


Periwinkle Anatomy


Two antennae (chemosensory organs) peek out from a fleshy foot.  In the image above you can see one eye near the stem of the higher antenna and the snout between the two antennae.  The sole of the foot is the curved white surface behind (below) the operculum.  The muscular, mucus laden foot enables the periwinkle to move along rocky boulders and transverse rocky and sandy shores in search of food.  Periwinkles are herbivores.  They graze copious amounts of algae such as the the macro algae sea lettuce (Ulva lactuca) and much smaller diatoms (phytoplankton).



Periwinkle in Action


Factoid:  Periwinkles have a serrated, rasping, knife-like tongue called the radula.  The radula scrapes algae from rocks.  (In other snail species, the radula bores through hard shells like quahogs, oysters, et cetera.)  For periwinkles, the algae is mixed with mucus and then passed into the digestive track.

Predators include crabs, seastars, birds and now a voracious worldwide human population.

Saving a Critically Endangered Sea Turtle

Friday, September 5th, 2008

Nature’s Classroom Teachers Find Endangered Sea Turtle

In keeping with the theme of this web site, “Saving the World One Turtle at a Time,” opportunity came knocking across the ether at 11:30 this morning.  Five teachers from Nature’s Classroom ( had traveled to Chapin Beach in Dennis for field orientation on the last day before school resumes next week.  They spotted an apparently lethargic “sea turtle” in a shallow tidal pool.  While most folks would have walked on by figuring that the incoming tide would handle the situation, or while someone else might have made the absolutely wrong choice of tossing the turtle into the sea to fend for itself, the Nature’s Classroom teachers took action.  They called the sea turtle stranding center at Mass Audubon’s Wellfleet Bay Wildlife Sanctuary (508-349-2615) to report the sighting.  The sanctuary called us and the game was afoot. 

Speaking over cell phone with the teachers, we learned that they had a fairly good handle on what constituted a sea turtle, but they were unsure of its species.  We asked that they remain with the animal while we sped to their location … about a 45 minute drive.  As we reached Chapin Beach, the tide was flooding across the tidal flats with a vengeance.  Two teachers were “escorting” the sea turtle in the shallows between sandbars.  A brief look was enough to identify the animal as a Kemp’s ridley, one of the rarest and most critically endangered sea turtles in the world.  By size we could estimate its age at two to two and a half years old.  In other words, this animal was the typical juvenile sea turtle that we find cold-stunned on Cape Cod beaches from late October to December.  But the cold-stunning season is still six or seven weeks in the future.
Don Lewis Holds Rescued Juvenile Kemp’s Ridley Sea Turtle
En route to the beach, we had alerted the New England Aquarium that we were responding to this potential sea turtle stranding.  Now we called them back with the species identification and our assessment of the animal’s condition.  There were early indications, beyond its lethargic behavior when first observed by the teachers, of the potential for future cold-stunning.  The right rear quadrant of its carapace was covered with brown algae; algae was also beginning to form on the rear of the turtle’s plastron.  There was a coating of algae on the top of the animal’s head and some algae buildup on the trailing edge of both front flippers.  There were a few dings on the keel as though it had been wave-tossed against a rock groin or breakwater.  When we observe turtles of this size during the outset of the cold-stunning season, we see the same, but much more extensive, indicators.  At least by the time we arrived on the scene, this sea turtle had become quite strong and active.

Rescued Kemp’s Ridley Sea Turtle (Story in Video)

In conversations with the aquarium and by proxy with NOAA, we weighed three options: immediate release on site, medical examination at New England Aquarium, or immediate release on the southern side of Cape Cod into Nantucket Sound … so that it wouldn’t get trapped by cold waters within the bay and become hypothermic and cold-stun a month of so hence.  Based on our field assessment, the decision was made for us to release the animal into Nantucket Sound from a southern Cape Cod beach. 

We crated the sea turtle for transport in our Element.  (Thank the gods of science that field researchers always come equipped for field emergencies!)  We began the trek across the Cape with a short stop to visit with our friend & colleague Kara Dodge, currently a PhD candidate at UNH and formerly a NOAA sea turtle coordinator.  She had flipper and PIT tags to append and to insert, and it gave us a nice quiet space to acquire the morphometric information we always document for sea turtles found in Cape Cod Bay.
Don Lewis Reads Caliper and Kara Dodge Records Data
Next we rendezvoused at the beach with a photographer from the Cape Cod Times whom we had alerted while driving from Dennis.  With sea turtle stranding season only a few weeks in the future, we didn’t want to miss this opportunity to use a photo-op to make people aware of what’s coming and what they should do and who they should contact.  By 3:15 in the afternoon we had released this fully charged sea turtle into the sound.  When we let it go into the oncoming surf, the turtle exploded forward like a hotrod leaving salt spray rather than rubber as it accelerated from zero to sixty faster than you could say, “Kemp’s ridley.”
Release of Rescued Kemp’s Ridley into Nantucket Sound
Finding a Kemp’s ridley sea turtle in Cape Cod Bay other than on the beach during the cold-stunning season is an extremely rare event.  There has only been one other such happening several years ago of which I am personally aware.  In that case the decision was made to tag it and release it back into Cape Cod Bay with an extremely unsatisfactory outcome a month or so later.  This time we maximized the odds that one of the most critically endangered species would have one more juvenile turtle to grow into adulthood and help restore its population.  We hope to see this turtle’s flipper tags or detect its PIT tag on a nesting beach in Rancho Nuevo, Mexico in another 15 or 20 years.  Or at least we hope that our successors in turtle conservation will see the fruit of today’s adventure in a couple of decades.  (ASIDE:  We’ve always considered it a bit unfair that sea turtles outlive sea turtle researchers.)
A hearty bravo to Nature’s Classroom without whose intelligent action this morning, nothing good would have come of today’s event.  And thanks also to a team of dedicated volunteers and professionals from Mass Audubon, the New England Aquarium, UNH and NOAA who responded to the challenge, made the best decision for the animal’s survival and flawless executed its impromptu rescue and release.  And that’s how we intend to save the world:  one turtle at a time.
Don Lewis Releases Endangered Kemp’s Ridley Sea Turtle