Both are integral to nature’s cyclical life
Driving in downtown Charleston among construction, I glanced up to the top of a crane. Just above the crane, a gibbous moon peered down from the early morning sky. This quick glance of the two objects made me think about the crane’s newness and the moon’s oldness. Our moon stands as an inert and ever-present eyewitness to most that’s occurred on earth.
Yesterday’s negative tide uncovered a vast mudflat at the upper reaches of the Stono River tidal basin. Mean sea level (msl) occurs at approximately mid-tide. Builders and map makers use mean sea level as their datum, or elevation reference. Tides are referenced to a different datum, known as mean lower low water (mllw). Mean lower low water, the average of the lower low water height of each tidal day observed over the National Tidal Datum Epoch (approximately 20 years), becomes this tidal datum. During new and full moon phases, the sun and moon’s gravity work together to expand tidal ranges. When low tide dips below mean lower low water, we refer to this as a negative tide.
Within the tidal flat, the Arctic migrators have arrived. Two whimbrels, dressed in henna brown breeding plumage, forage near the water’s edge. A black-bellied plover scurries about in the distance. Red knots and dunlins probe the pluffmud in a sewing machine fashion. At high tide, flocks of these migrators, mostly segregated by species, sit together resting on the upper beach face.
The ocean’s water temperature rises rapidly in the spring. The marsh responds. Last week, crab pots appeared in numbers throughout the tidal creeks. This is peeler season, when blue crabs shed last year’s shell and grow a new one. These crabs slowly and methodically back their way out of last year’s armor, claws last. Temporarily immobilized, soft-shelled crabs become the target of predators, including other blue crabs.
In the springtime, swirls appear on the water’s surface where tiny translucent fish, known as silversides, swim in schools. In the upper part of the tidal basin, the creek water salinity approaches brackish, which suits this species well. Silversides hide in the marsh grass at high tide, but lay exposed to predators at low water.
Through these gravity-driven tides, the moon exerts extreme influence on life in the salt marsh. Within this common rhythm, life and livelihood negotiate this influence. Through Earth’s history, as now, the moon has influenced tides, thus life. Despite its influence, the moon remains a silent witness. Like a stoic clay soldier, the moon observes the earth and reveals not the slightest expression.
Anton Dumars owns and operates Tideline Tours located at 103 East Cooper on Folly Beach. Come by for a visit or sign up for a Tideline Adventure! Visit http://tidelinetours.com or email Anton at saltmarshadventure@gmail.com or call 843-813-5009
