O n e t o u c h o f n a t u re m a k e s t h e whole world kin. ~ Wi l l i a m S h a k e s p e a re
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The Critters That Call The
SALT MARSH HOME By Danielle Meeker of The Wetlands Institute
Photo Credit: Danielle Meeker
Hard clam and ribbed mussel actively filter feeding.
Atlantic needlefish swimming just at the surface of the water.
D
riving down the causeway to Seven Mile Beach, you can’t help but notice the expanse of salt marsh outside your window. As summer approaches, those watching get the privilege of seeing the marsh turn from a dull brown backdrop to a lush landscape teeming with life. Maybe they roll down their windows and breathe in the salty air mixed with a little low-tide mud smell. It is easy to drive by with eyes on sandy beaches and an endless ocean horizon, but there is so much to love and appreciate in the salt marsh. The salt marsh is a wetland ecosystem that develops between upland habitat such as forests and low-energy intertidal zones. The dominant factor
that influences this habitat is tides. Every day the salt marsh experiences two high tides and two low tides. High tides flood the area and all the surrounding plants and animals with salty water. About six hours after a high tide, the water has receded, leaving all of those same organisms exposed to the elements. Plants and animals that live in this habitat must be able to withstand constant changes to their environment. One type of animal uses the power of tides to its advantage when feeding. Bivalves, a type of mollusk that has two shells, do what is called filter feeding. By ever so slightly cracking open their shells, bivalves use their siphon, which acts as a straw, to suck in water and filter out any plankton or organic material that is in it.
At each high tide, bivalves are flooded with food and nutrients that sustain them. There are many types of bivalves in our salt marsh, but some of the most commonly seen are ribbed mussels, eastern oysters, and hard clams. All three make their home in a salt marsh but prefer different locations within it. Ribbed mussels (Geukensia demissa) are found firmly attached to the base of salt marsh grass, or Spartina alterniflora. They use strong byssal threads to anchor themselves in place, where they will live out the rest of their lives. Oppositely, hard clams (Mercenaria mercenaria) prefer to call mud flats home. In the soft mud, hard clams are able to use their foot to orient themselves and
move when submerged in water. But at low tide, they bury themselves to avoid predators and exposure to the elements. Lastly, eastern oysters (Crassostrea virginica) require a hard surface to grow on. As juveniles, oysters float as plankton until they hopefully land on a hard substrate and begin to grow into their adult form. They can often be seen growing on other bivalves such as other oysters or mussels and off of rocks and pilings. Despite their differences, all three of these bivalves help to maintain this ecosystem by filtering the water and creating habitat for numerous other organisms. When looking out across the green expanse of the salt marsh, it can be surprising to learn that salt marshes are some of the most productive and diverse continued on page 46
Seven Mile Times
Memorial Day 2021
s e ve nm ile t im e s .c o m