Nature Notes: Mussel Beach

There was a brownish wrack line marking the reach of an extra high tide stretching in both directions for more than a mile
Found along the wrack line on the beach between Bridgehampton and Sagaponack were untold numbers of blue mussels and tiny blue mussels, at most an eighth of an inch in size. Jean Held

On Monday afternoon I went down to the ocean beach and walked between Bridgehampton and Sagaponack. There was the usual bunch of beachgoers enjoying the sun, but what I was there for was to examine the wrack line left by recent high tides and storms, such as the tropical cyclone Chris that brushed our shore last weekend. 

I also went there because my wife, Julie, and a friend, Jean Held, had visited the same stretch of beach and came back with blue mussels and other lifeless critters on which were copious tiny blue mussels, no bigger than an eighth of an inch in size.

The ocean beach there is very wide all the way to Water Mill, thanks to a coastal taxing plan initiated by the Town of Southampton several years ago. There was a brownish wrack line marking the reach of an extra high tide stretching in both directions for more than a mile. I examined that line: Everything was dead, including the seaweed called knotted wrack, or Ascophyllum nodosum, which is a common brown alga that attaches to rocks and grows in the lower intertidal zone. For every foot of wrack line there were more than a thousand tiny mussels, new offspring of the year, apparently doing well until big waves washed them, and the shells and seaweed to which they were attached, away.

I presume they had washed west from Montauk, where the rocks start and where blue mussels do well in an average year. Along with the tiny bivalves were an assortment of other marine creatures, skimmer shells, skate egg cases, tiny crabs (perhaps Japanese shore crabs, which have established along Montauk’s rocky shores in the last 20 years), conch egg cases, moon snails, sand crabs, and many more, hardly identifiable. I walked to the east about two-quarters of a mile along the wrack line until I came to a least tern colony.

At 1,000 or so per foot, there could have been as many as two or three million dead blue mussels. 

No part of the wrack line was alive, except for three six-inch-high sea rockets with five or six fleshy green leaves each. It used to be the practice to rake beaches with mechanized equipment to make them more attractive to the people using them. It has been found, however, that sea wrack lines are often the starting point for new beach plant growth that accumulates sand and builds up the height of the beach. Raked beaches, on the other hand, lose sand with each large sea tide accompanied with surf. This wrack line was almost a week old and had not been left alone.

We wonder, though, if the rocky intertidal blue mussel population will suffer as a result of lower recruitment. Blue mussel beds can form the way oyster beds form. Just as larval oyster fry settle out on live oyster or empty shells, blue mussels similarly recruit free-swimming mussel larvae to add to the overall size of a bed. Blue mussels, Mytilus edulis, are as marketable as oysters and a favorite in restaurants that feature seafood. So, empty mussel shells should be left in situ, just as we are now saving our oyster shells and returning them to the shallow coastal waters.

The knotted wrack is enjoying a bumper crop year, just as a closely related brown alga, sargassum weed, is in Caribbean Sea waters and those of the Gulf of Mexico. It has been written that when Columbus came to the Caribbean in the late 1400s, there was very little of it around. It could be that the increased flux of nitrogen products into our seas from septics and fertilizers, as well as from the local vertebrate fauna, is favoring the growth of these seaweed species. 

In fact, just as local groups and institutions are increasing oyster stocks artificially to chow down on noxious marine plankton that are not only choking waterways but can be poisonous when ingested, the Cornell Cooperative Extension and other entities are starting underwater kelp farms. Kelp not only removes nutrients from the water column but also is an important food item in different human subcultures.

What would be better than kelp, however, for serving as a habitat for bay scallops and certain fish species, including winter flounder, is eelgrass, Zostera marina, which once grew so thick in local waters such as Accabonac Harbor that it would foul outboard motor props. But those days are gone. With global warming heating up our estuaries, we are not likely to see a return in the next few decades.

I like the water and the sand, and I’ve been a clammer, crabber, eeler, and fisher, but never a beachcomber. One can learn a lot by walking the shoreline periodically. One time it’s hundreds of washed up skimmers, another time it’s the small brownish shell of molted horseshoe crabs, then again, several types of kelp can be found, as well as swarming insects, sand crabs, bunker, and, even in the early fall, monarch butterflies and dragonflies. 

Think of it. The beach is an ecotone between the sea and the land, and it occurs all over the world in one form or another, but always with a dominant substrate of sand. What was odd on Monday afternoon was that I was the only one of 75 or so people parked at the end of Ocean Road walking the beach. A few were on the water, most were on the sand, lying on blankets or towels or sitting in portable deck chairs.

Larry Penny can be reached via email at