Healthy waters are a staple of healthy island life. While visiting the Island, a lot of visitors will ask about the quality of our water.  They see its brown or green coloration and think it must not be very clean.  There’s a natural inclination to see something murky as unhealthy.   Not only is our water healthy, but its some of the cleanest sea water you’ll find on a coastline! The murkiness you see comes from two things; how much life is in the water and what attracts that life into the water; our mud.

From dirty pluff mud comes clean water

Pluff mud is a goopy mixture of soil, dead animal and plant matter. The majority of that dead plant matter is the spartina grass that lines our salt marsh. Pluff mud packs down densely, and doesn’t allow oxygen to permeate below a few inches of the surface.  Any type of bacteria that survives in the mud has to create its own oxygen and you can actually smell this chemical reaction at work. As the bacteria create oxygen, they emit a by-product into the air, hydrogen sulfide, giving it a distinct aroma. Many people are convinced its smells like rotten eggs. 

The pluff mud lines the bottom of our tidal creeks and its top layer is constantly moving with the strong currents we have here around the island. This primordial soup of nutrients is continually being kicked up and swirled about, never quite getting a chance to settle. As the current moves at its maximum speed churning up the mud, our waters turn a very ruddy brown coloration. This is the predominate color over winter as cool temperatures control the growth of microorganisms.

The Phytoplankton Cometh

Inside the pluff mud is a large amount of decayed animal and plant matter.  This organic material is called detritus. Detritus breaks down in the salt water and allows microscopic algae known as phytoplankton to feed.  These guys are tiny.  We’re talking a fraction of a millimeter in length.  As the phytoplankton eat the detritus, they release oxygen into the water. Warm temperatures and increased sunlight contribute to their growth. During the hot summer months the amount of phytoplankton increases and, while you can’t see them individually, you can see the effects of the colony. A large phytoplankton bloom will turn the water a greenish color.

Clean Water via the Food Web

Is all this algae bad?  While some areas of the country face environmental catastrophes due to algae blooms, we don’t have that problem here.  There’s a delicate balance to maintain and the salt marsh does an amazing job of regulating this by creating a food web. The algae that feeds off the detritus in turn becomes food for our oyster beds.  Oysters are constantly filtering the waters here, collecting phytoplankton, other algae and bacteria and pushing out clean sea water.

Other organisms that eat phytoplankton, include zooplankton.  Grass shrimp larva, cannonball jellyfish and sea roaches are common examples. They are voracious eaters, taking in as much phytoplankton as they can. In turn, bait fish, shrimp, crabs, and mobula rays make their way here and feed off zooplankton.  These animals will continue the food web, as larger fish, sharks and dolphins will eat the smaller creatures.  The fecal waste of all the animals go back into the water, becoming detritus, feeds the phytoplankton, and the cycle repeats itself over and over.

Keeping a balance for clean water

It’s important to have a balance within our water column.  Any loss of one organism can have profound and devastating effects on the entire ecology. Loss of oyster habitat, overfishing or taking undersized fish out of the food chain all contribute to the decline to our water quality. Fishing restrictions include time, size and quantity give a species a chance to grow and repopulate without human interference.  On land, building restrictions are in place to limit the amount of harmful pollutants entering our creeks and rivers.  Without these regulations, we run the risk of becoming another environmental catastrophe.

While the waters here may not be crystal clear, you can be assured that they are healthy and clean .  The next time you’re out on a dolphin tour exploring the waterways, you can be thankful that our murky waters bring so much life to our island.