We may love walks on the beach and the sound of waves crashing on the shore, but the sea also offers other hidden joys. All along the 7,500-km-long coastline of India, the rise and fall of the tide supports ecosystems that are rarely noticed.
When the water recedes, and human activity abates, a part of the shore only visible at low tide — the intertidal zone — becomes exposed. Due to the continuous ebb and flow of salty water, and exposure to harsh sunlight, the intertidal zone is a good place to explore marine biodiversity. At low tide, the wilderness on our shores is revealed, making this a nature trail like no other. Here are some of the most common creatures you’ll find in a tide pool on the shore, to get you exploring on your next seaside stroll.
Some rocky shores look like gardens, with sea sponge ‘growing’ on the rocks. Interestingly, these animals were the inspiration behind the protagonist of the animated show, Spongebob Squarepants. If you see them, go closer and look at their skin. These primitive animals belong to a phylum called Porifera, which literally means ‘pore-bearing organisms’. Pores filter food in the form of bacteria, plankton, and other organic matter from the sea.
These crabs are extremely entertaining to watch. Fiddlers get their name from the behaviour of the male of the species. Fiddler males have one very large claw, which they wave, to mark territory or to attract mates. This action resembles a person playing a fiddle. Usually found in mudflats and among mangroves, but also on other shores, this crab is the easiest to spot and identify for a shore beginner. In Japan, they are called shiomaneki, which loosely translates to ‘the one that beckons the tide’.
Named after the anemone flower due its obvious resemblance, it’s easy to mistake a sea anemone for a plant. It has a flower-like organism on the surface (tentacles and an oral disc) and a trunk-like column that’s buried under the sand or attached to a surface (like a root). But this animal is classified under the phylum Cnidaria, which also includes jellyfish and corals. They’re found in the deep sea as well; remember the home Nemo lived in with this father in the animated film?
These creatures are colonial soft corals found predominantly in warm waters and around reefs both in the intertidal zone and in the deep. The tiny animals are called sea fans because of their resemblance to old hand-held fans. The fan-like body branches out, giving the impression of a tiny tree growing. They are found in glorious colours on Mumbai’s coasts.
This little creature sits clamped on rocky surfaces in tide pools and it is easy to miss them if you’re looking for larger or more colourful creatures. But the limpet, which will probably be feeding when you find it, has interesting capabilities. Its scientific name (scutus unguis) comes from its shell, which looks like a shield — called ‘scutum’ — used by ancient Roman armies. It scrapes algae off rocks with a radula, a bristly tongue with rows of tiny teeth made of the mineral goethite set in a chitin matrix, resulting in one of the strongest biological materials known to humans.
Sea stars or starfish aren’t actually fish, but marine invertebrates. These are delightful creatures to come across on busy beaches because of how much pop culture has already endeared them to us. They’re usually found towards the edge of the intertidal zone, close to the water, clamped on rocks, moving slowly with their tube feet. These animals possess the power of regeneration, and some species can grow back even from one severed healthy limb.
When open at high tide, these startling green creatures look like a bouquet of flowers scattered over rocky surfaces. These are also Cnidarians, and come under the same class as anemones, which is Anthozoa. Unlike anemones, zoanthids live in colonies, and are more like coral in that sense. When the tide rolls out, they retract their tentacles and close off, resembling a small jelly-like object. Some zoanthids can be extremely dangerous as they carry minute quantities of a marine toxin called palytoxin, which can paralyze or kill a human if it enters the body.