It’s a gray January day, the warmth of the summer sun now a distant memory. As I throttle up the engine and push the R/V Chamberlain out of the boat slip, we are met by a brisk northeast wind and whitecaps breaking over the windshield. We are out collecting oyster samples to bring back to the lab for analysis – a wet and muddy chore, but a worthwhile one. A sentinel species, these lowly creatures are a valuable indicator of the health of a marine ecosystem. As filter-feeding organisms, they help control pollution; a single oyster can filter around fifty gallons of water in a day, improving water quality for other species.
As we leave the harbor and nudge up a tidal creek to our first collection site, the smell of the marsh greets us – that glorious low-tide smell, a blend of seaweed, salt, and mud that few but a marine scientist can truly love. The smell of life.
Estuaries – where a long arm of the sea reaches inland to meet the mouth of a river – are among the most ecologically rich places on earth. Since they offer both abundant food and protection from the harshness of the open ocean, they provide a habitat for a vast variety of marine animals. As “nurseries of the sea,” they are a haven where many species of fish and marine invertebrates produce their offspring; here the young can mature in relative safety before returning to the deep water. Meanwhile the salt marshes and oyster beds that fringe the estuaries act as giant filtration systems, sequestering nutrients and degrading pollutants. They also protect shorelines from erosion by wind and waves.
Human civilization was born on estuaries for similar reasons: safe harbors for boats and bounteous water and food. The earliest known urban development began around the Euphrates River estuary in the city of Ur, in what is now Iraq. Similarly, early Egyptians depended on the Nile River estuary for trade, agriculture, and fish.