Become a Horseshoe Crab Sea Sleuth

Horseshoe crabs are an amazing species. They've been around for over 450 million years. (Yes, that's 450 million!) They hark back to the very beginning of life on earth--before people, before dinosaurs, even before flowering plants.

Not crabs at all (like crabs, they are arthropods, but they are more closely related to scorpions, ticks and spiders), these strange-looking creatHorseshoe Crabures are very important to the biomedical industry where they play a vital role protecting us from exposure to dangerous bacteria.

An extract from the blood of the horseshoe crab is used to test all of our medicines, vaccines, and intravenous medical devices for bacterial contamination. No other test works as easily or reliably to ensure that medicines are safe.

Horseshoe crabs have been seen in the area, but they are in decline. Your assignment, should you agree to accept it, is to look for horseshoe crabs and report any sightings to Salem Sound Coastwatch.

What about that algae that has plagued the Nahant Bay beaches?

Pilayella Littoralis

by Mary Franklin

The algae, Pilayella Littorallis, is a free living planktonic form of a common algae that is usually found attached to rocks. It has mutated in Nahant Bay and appears as a thickly gelatinous brown crud/slop techically known as casts. The casts are several centimeters deep on the shore and a gruel-like mass on the water surface. When it undergoes anaerobic decomposition on the beach, the strong hydrogen sulfide (rotten-egg) odor is usually repulsive.

P. Littoralis has been around since the turn of the century. When the Lynn-Nahant tombolo (sand-spit) was made a causeway, the circulation patterns that permitted natural cleansing of the beaches iwth the tides were permantently altered. Flooding now occurs with extreme storm events. Seubsequent buildup of nutrients in the sound from numerous sources is likely to impact its overall population growth and many attempts have been made to improve the situation. Efforts to suck it up from the water, poison it, or rake it off the beaches have been tried with little or no success.

The best solution may be to install pipes under the causeway to allow the sea to flow freely between the two bays. This project is being contemplated, along with a change to the roadway to allow for more walkers and bikers.

Nature Notes: Flora, Fauna, Geology, Astronomy and Human Impact


Flora and Fauna

Around 2000, biologist Juditha Burchsted who has observed and documented the flora and fauna at Preston Beach for many years, noticed that the fairly common Lady crab and the rarer Blue crab in the area, perhaps because of the slight warming of the waters along the coast, allowing these species to extend their ranges further north. Other foreign species, such as the European oyster, Japanese crab, and a sponge known as deadman’s or mermaid’s fingers are also invading the coastal waters from the Boston Harbor to the Gulf of Maine. For more information about the Lady Crabs, see below.

Birds that frequent Preston Beach: migratory brant geese with dark heads and white around their necks (back after a long hiatus due to eel grass disappearance) ; buffleheads, which look like “little toy ducks”; plovers, a protected species on Plum Island; black cormorants; herring gulls; black bat gulls; Bonaparte gulls in spring and fall.

Spotted on or near Preston Beach: snowy owls; grebes, a diving bird related to loons and bank swallows.

Ocean Animals: seals; starfish; Ctenophore or jellyfish; several species of crabs.

Tidal pool population: Segmented worms (mate once a year in May or June).

Occasionally wash ashore: silvery-blue sand lancets; male lumpfish; skate

Finding buried lady crabs.(Field Notes)

Burchsted, Fred. Underwater Naturalist. The American Littoral Society June 2005.

Many years ago we heard the great animal behaviorist Niko Tinbergen talk about how crabs hide by burying themselves in the sand and how the seaside crows find them. We visited our own favorite beach, Phillips Beach in Swampscott, Massachusetts, (the north end called Preston Beach in Marblehead) to find buried crabs.
We have watched a population of lady crabs, Ovalipes ocellatus, here. The field guides and most distributional studies give the range as Georgia to the southern shore of Cape Cod and out onto Georges Bank with an isolated population in the southern Gulf of St. Lawrence. This northern population, along with those of many molluscs, echinoderms and algae, is apparently a relict from the Hypsithermal era (9500-3000 years before present) when temperatures were up to 2.5 C. higher (at the Climatic Optimum, 7500 b.p.) than today, and these creatures had continuous ranges from the U.S. mid-Atlantic coast to the Gulf of St. Lawrence. Most populations in the Gulf of Maine and on the Nova Scotia coast have since gone extinct. (See E. L. Bousfield and M. L. H. Thomas' Postglacial changes in distribution of littoral marine invertebrates in the Canadian Atlantic region--(Proceedings of the Nova Scotia Institute of Science, volume 27, supplement 3, (1975), pp. 47-60 for more information). There are scattered Gulf of Maine populations, either Hypsithermal relicts or recent range extensions, which are largely unnoticed in the literature. Stephen Berrick in his Crabs of Cape Cod (Cape Cod Museum of Natural History, Brewster, MA, 1986) says that he commonly finds lady crabs on Cape Cod Bay sand flats. Our population is apparently unique in the Gulf of Maine in occurring on an ocean beach.
We found our buried crabs. On flat parts of the beach just above low tide line, they are betrayed by slight bumps in the sand, best seen when the sun is low on an early morning or late afternoon low tide. The lady crabs are buried completely, unlike blue crabs which bury horizontally just under the surface with their antennae sticking out. The lady crabs are slanted under the sand with the front nearest the surface only about 6 mm. and the rear about 14 mm. beneath the surface.
Many crabs can briefly reverse their normal respiratory current for cleaning purposes and take water into their branchial chambers near the mouth and expel it through openings at the bases of the legs. But lady crabs are capable of prolonged reversal of their respiratory currents. This keeps them from getting clogged when buried with their posteriors deep in the sand. When buried in shallow water you can see the two spots where the sand is roiled by the excurrent water. The relatively deep burial allowed by their reversed respiratory flow gives them a distinct advantage over blue crabs in avoiding predation by larger crabs (D. E. Barshaw and K. W. Able's Deep burial as a refuge for lady crabs Ovalipes ocellatus: comparisons with blue crabs Callinectes

When we release them in shallow water, they bury themselves by digging with their last pereiopods (walking legs) which are flattened for swimming as in blue crabs. It has been speculated that the flattened pereiopod tips evolved originally for digging rather than swimming. Meanwhile they slam their bodies against the sand, stirring it up so that it settles back down on top of them.
We hope someday to see the fish crows find them.
J. C. A. Burchsted and Fred Burchsted are doing a long-term study of the fauna of Preston-Phillips Beach. J. C. A. Burchsted is in the Biology Dept. at Salem State College. Fred Burchsted is in the Research Services Dept. of the Widener Library at Harvard University. for J. C. A. Burchsted for Fred Burchsted.


Flirtation Rock, also known as Pig’s Rock on Preston Beach, is composed of basalt. Basalt is an igneous rock, a common volcanic rock. Basalt that has not weathered is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet.

Most basalt magmas have formed by decompression melting of the Earth’s mantle. The Flirtation Rock basalt also called diabase or gabbro.

The mineral content of basalt mostly includes calcic plagioclase feldspar, pyroxene and sometimes olivine (also called peridot).  Other minerals present in minor amounts include iron oxides and iron-titanium oxides, such as magnetite, ulvospinel, and ilmenite. Because of the oxide minerals, basalt can acquire strong magnetic signatures as it cools.


by Jim Keating, Marblehead High School Astronomy Teacher

Each of us faces the ultimate question that has intrigued humans since the beginning of awareness. Great minds like Plato, Beethoven and Hemingway have tried to give their
personal answers, but it continues to perplex every one of us. The ultimate question is simply, “What are we?”

Certainly part of the answer goes beyond the physical universe to include philosophical and cultural issues. We define ourselves by what we create, what we worship, what we admire and what we demand of each other. But a major part of the answer is embedded in the physical universe and for this we turn to astronomy. No other science speaks so clearly about our place in the universe. We cannot hope to understand what we are until we understand where we are in a universe filled with worlds, stars and galaxies.

Beach Bluff Park with the addition of its “Stonehenge” sculpture, hopefully will help all those who visit it, get a better understanding of where they are in the universe.

Human Impact

Boat pollution
is banned in the waters of Swampscott, Lynn, Nahant, Saugus and Revere!
The Federal Register of March 18, 2009 published a determination establishing the Lower North Shore No Discharge Area (NDA). This means that boats are no longer allowed to pump their waste into local waters. Coming as it does just as Spring arrives, the new NDA will be in effect for the coming boating season.