Wednesday, May 31, 2017

On the rocks

It started a few weeks ago. I was sitting around my kitchen table with friends, sipping wine and chatting after dinner.

Wood Neck Beach
"Hey Kirstin," my friend and fellow postdoc, Cassidy, called from across the table, "Can you recommend a good field guide for the New England intertidal? I need to get familiar with the local organisms this summer."

To my left, my boyfriend almost snorted. "Cassidy," he informed her, "Kirstin is a field guide to the intertidal. Just take her with you!"

So she did.

Yesterday after work, Cassidy and I headed out to Wood Neck Beach, just north of Woods Hole. Unlike most beaches on the Cape, Wood Neck is covered in rocks of all sizes - gravel, cobbles, boulders. We went at low tide so we could see the organisms when they were exposed.

Semibalanus and Littorina on a rock on Wood Neck Beach 
The main organism we saw was the northern rock barnacle, Semibalanus balanoides. Barnacles are especially common in the high intertidal because they are outcompeted by other organisms at lower tidal levels. They are also well-adapted to survive in the high intertidal, an area exposed to air for long periods each day. Their shells can shut tightly, sealing water inside and helping the barnacle avoid dessication. Semibalanus was all over the rocks on the beach. We also saw a number of black snails, Littorina littorea, known as the common periwinkle. Littorina is a common herbivore with a smooth spiral shell.

A boulder with barnacles, oysters, and mussels
On some of the larger boulders, we could see eastern oyster shells (Crassostrea virginica) and blue mussels (Mytilus edulis). Whenever we did find blue mussels, they were on the underside of a large boulder. Mussels prefer to be lower down in the intertidal zone so they don't dry out. They're also pretty good competitors, so they can hold their ground in preferable habitats. If you look on the boulder here at right, you'll see Semibalanus all over the face of the boulder. The two large white spots are Crassostrea oysters, and then on the bottom, you see dark lumps. Those are Mytilus, blue mussels.

I absolutely love tide-pooling, and if you've been following this blog for a while, you have read about my intertidal excursions in Oregon before. Tidepooling became almost a hobby for me. I haven't gone nearly as often since moving east, though, because intertidal communities in New England are much less diverse than on the west coast. Still, it was great to get outside with a friend and explore some of the local biodiversity!

Cassidy and I on Wood Neck Beach

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