As the afternoon cooled down and the tides retreated, exposing the rocky shore and all its hidden treasures, we rolled up our sleeves and headed down to the beach carrying small buckets to search for little marine snails called nerites that adorn the reef substrate like sprinkles on cake. Golhaa nagan dhiun or gleaning — an age-old practice of harvesting marine invertebrates from shallow coastal waters during low tide — was what introduced me to the wonders of the intertidal zone.
Everyone wanted to pick out the largest nerite. It was especially gratifying to find one that was particularly better at hiding, blending between the rocks and crevices. After gathering a bucketful, we brought them home to be boiled, cleaned, cooked in spices, and eaten with roshi.
I remember how similar-looking nerites only had slight variations in the shell patterns; how the darker-shelled ones held on maybe a tad more tightly, their tentacles perhaps more conspicuous than the rest. The spiral-shelled ones were harder to clean even after removing the operculum, a calcareous trapdoor-like structure guarding the only opening in their small bodies. Until the shell is removed, not much is visible to the naked eye aside from the sticky, muscular foot covered in slime along with its head and sensory organs.
The smooth, lighter-shelled nerites were a favorite — we harvested these more than the others, which caused their population to temporarily collapse after our many visits to the reef. I cannot remember what I made of all these observations then, but I know that it has stayed with me for over 20 years. Core memories in the form of field biology notes.
In true Maldivian fashion, I spent a good part of my youth pondering marine fauna. Although their name (golhaa) finding its way into political slang was a misfortune the nerites had to bear, their closest relatives luckily escaped such a fate.
Take, for example, the Sa’ndhara legend: a folktale from the South about a turbinid sea snail gifted to the Queen of the Moon by a triggerfish to defeat a demon. The intertidal zone and its critters have always intrigued us coral-island folk. Many continue to explore the exposed coastal areas simply for a stroll, to harvest annelids and worms for fish bait, and to gather edible mollusks for a delicious dinner. Though often overlooked as fishery, gleaning remains an important food source for island communities with women and children at this tradition’s epicenter.
The intertidal zone, also called the littoral zone, is the area of the foreshore and seabed that is exposed to air at low tide and submerged at high tide. This shoreward fringe between the lowest and highest tides harbor some of the most resilient organisms that are constantly exposed to changing salinity, temperature, turbidity, and moisture. The organisms that inhabit this harsh environment have special characteristics to survive in these conditions — during low tide, some are easily spotted on seawalls, reef flats, and crests and some are better camouflaged.
As an ecotone — or transitional — area between two biological communities, the littoral environment is complex and rich in biodiversity. Among the notable critters found in our backyard tide pools are octopuses, giant clams, several different crustacean species (like crabs and shrimps), gastropod sea snails, annelid worms, sea-stars and of course, corals and fish. It is always interesting to see how their sightings vary from the shore to the reef crest and forereef beyond, providing important clues on how they have adapted to different zones in the intertidal area.
One behavioral adaptation used by some organisms in the littoral zone to avoid thermal extremes is being active only during the low tides in the evening or at night, sticking to scars on the rocks for homing when the organism is inactive. This behavior is observed in the famously harvested Sa’ndhara snails like Turbo petholatus which are only gleaned after sundown when they are active. Some organisms exposed to air — like nerites, barnacles, and clams — evolved physiological adaptations such as protective coverings like shells to defend themselves against desiccation in addition to defending against predators.
Sessile animals like barnacles that need to withstand the crashing waves by sticking to substrates have interestingly developed protruding reproductive organs that they can alter to suit wave action to seek out mates while still anchored to their rocks.
Some intertidal crabs persevere through fluctuating moisture changes by keeping their gills moist using articulating plates that block dry air entering the gills; while crabs like the superabundant thin-shelled rock crabs Grapsus Tenuicrustatus — commonly seen in islands’ breakwaters and reef crests — have adapted to the supralittoral zone by evolving to breathe air in addition to having few gills to withstand short immersion periods. Many intertidal invertebrates — particularly detritus-feeding animals such as hermit crabs — are camouflage masters; they also utilize the continual replenishment of food brought about by the sea.
The intertidal zone is undoubtedly an exciting place both ecologically and culturally. It grants you easy access to explore diverse life forms, making for a convenient adventure any Maldivian can enjoy. However, with the ever-increasing coastal modifications and decreasing accessibility to reefs across the country, the Anthropocene in Maldives is not only chipping away a traditional sustenance source; but also, a golden opportunity for wonder, curiosity, and stewardship towards natural resources.
In the meantime, I hope we become a generation that pays attention to the natural world. These reefs hold so much history, but also much more to discover.
As homage to the Maldivian saying, it’s time we went to the reef without our mothers telling us to.
Enas Mohamed Riyaz (Tonti) is an ecologist with a special interest in field biology and taxonomy, primarily working with protected species conservation in Maldives. Aside from her work in environmental research, regulation, and enforcement at the EPA, she is passionate about science communication and celebrating the natural history of Maldives.