Black rocks are slippery and demand respect. Dreaded barnacles may be near. For the uninitiated, advice helps: Tread slowly. Crouch low. No flip flops. Maintain 3 or 4 points of contact. Walk like a crab. The rocks feel sticky, maybe dry. Caution: things change quickly if you’re wet.

Still, people fall. Hard.  I have witnessed spectacular slides down cliffs, torn and stained swimwear, bruised backs, skin scraped raw and red, stubbed and bloody toes, one gashed head, and a fractured wrist.

I have a copy of The Sea is All About Us in a guest room for family and friends. I can’t say that it will ward off all evil falls, but it’s helped. The granite galvanizing, seaweed section quoted below is one of the oft read passages I share. What a teacher! She lived in Gloucester and wrote about it.

If you read it once, I guarantee that it will change how you see the colors of our rocky coast, and sea all about us.

From 1973 The Sea is All about Us by Sarah Fraser Robbins and Clarice Yentsch. Back cover: Yentsch and Robbins (first author-holding horseshoe crab)

The Rocky Shore 

The Black Zone

Plant and animal life on the rocky shore can be separated into six general zones, beginning with the Black Zone, which marks the average high point that the sea reaches upon the land. The Black Zone is covered by microscopic blue-green algae, which are so dense that they make a black line of varying widths along the rocks. These blue green algae exist at high-tide level all around the world wherever the sea meets the land on the rocks. 

Just below the Black Zone lie

The Periwinkle Zone and The Barnacle Zone.

named after the dominant animals. There is no definite territorial line for these animals, and indeed the zones often intermingle with each other. Barnacles and periwinkles can be found penetrating the Rockweed Zone (the next zone seaward) and sometimes into the edge of the Irish Moss Zone. Both periwinkles and barnacles are equipped to withstand desiccation (drying out), and can live very successfully in an area that is dry up to 70 percent of the time.

The Rockweed Zone

lies in the middle intertidal area, and is characterized by the brown seaweeds that live there, such as the sea wrack, Fucus, and the knotted wrack, Ascophyllum, which are long, brown seaweeds with conspicuous float bladders that are firmly attached to most of the rocks. They hang limply when the tide is out and float upwards as the tide rises until they are completely erect at high tide. They sway back and forth, dampening the effect of wave action, and providing a sheltered environment for many intertidal plants and animals.

The Irish Moss Zone

is down lower from the high tide line and is exposed only during the very low tides which occur twice a month. The short, dark red tufts of Irish moss, Chondrus Crispus, cover the lower rocks like a carpet, in sharp contrast with the brown Rockweed Zone, the white Barnacle Zone, the Periwinkle Zone and the Black Zone above. 

The Laminarian or Kelp Zone 

is exposed only at the very lowest tides, which occurs four times a year. This zone extends down as far as light usable for photosynthesis can penetrate–about 30 meters in Folly Cove, and 200 meters in very clear tropical water. The Kelp Zone is the dwelling place of many animals that can survive only continually submerged in water; sponges, hydroids, anemones, certain mollusks, echinoderms, arthropods, tunicates, and fish. Many of these animals may be found higher in intertidal zones, but only in pools that never dry up.

On tide pools- “AT TIMES IN AUGUST THEY ARE REDUCED TO A CRUST OF SALT CRYSTALS”

Tide pools occur in all zones. The upper pools in the splash area or Periwinkle Zone are sporadically replenished with sea water, and consequently are subject to variations caused by land temperatures. They may freeze long before the ocean does. They evaporate in hot sun and strong winds, and thereby concentrate their salinity, that is, become saltier than the sea. At times during August, they are reduced to a crust of salt crystals. After heavy rains and floods they become much less salty. Some tide pools in the middle zones will contain animals and plants characteristic of a deeper zone because the conditions present are similar to those in the zone below. Tide pools in the Irish Moss Zone often contain kelp and associated animals. Tide pools are always a good place to explore. 

The edge of the tide is a fragile environment which in its delicate natural balance can easily be destroyed by interference. The building of piers, jetties, and sewage outfalls, and the dumping of trash or industrial wastes into the ocean can be devastating. Overcollecting can be destructive. In the intertidal areas, look and touch only. Examine plants and animals carefully. Overturn stones to see what is clinging to them or living underneath, but always turn that stone back. To leave it overturned alters the environment completely and needlessly kills many organisms. Take photographs or make careful drawings for your notebook, but collect only dead material. Use unbreakable plastic containers from which to observe the organism and then return them to the tidal pool.