What is an Atlantic ribbed mussel?

Atlantic Ribbed Mussel (Geukensia demissa) is a bivalve that grows up to 4 inches long. They often form dense aggregations on the seaward margin of many salt marshes along the Jersey Shore.

Ribbed mussels are related to blue mussels, but are largely not fit to eat by people due to being rich in organic bacteria. Ribbed mussels also differ from blue mussels in appearance. The shell of a ribbed mussel is shaped like a long rounded triangle with corrugated ribs along the length (similar to corduroy pants).

Unlike blue mussels that usually attaches to pilings, rocks, or a dock, ribbed mussels are a true estuarine mussel and is usually found partially buried in the sediment and mud in tidal wetlands. Ribbed mussels do not burrow completely into the muddy bottom but remain partially exposed. They anchor themselves with byssal threads, which are mucous strands attached from the mussel to asubstrate.

Why are Ribbed Mussels Important?

Ribbed mussels play a critical role in the health of a salt marsh and are considered to be "ecosystem engineers" because they modify a wetland, making it more suitable for themselves and other organisms.

One of the most valuable functions performed by ribbed mussels is capturing organic matter from the water column when they feed. According to the EPA, one adult ribbed mussel can filter over a gallon of estuarine water an hour or up to 15 gallons of water per day.

The gills of a ribbed mussel are lined with cilia, which trap plankton and organic nutrients. Particles of organic nutrients are processed into inorganic matter by the ribbed mussel. A ribbed mussel uses this organic matter to build body and shell, and excreting excess organic material to the sediment making it available for other invertebrates and fish to consume; and providing essential nourishment that enhance plant life within a wetland and contributes to salt marsh growth. Mussel beds also help establish habitat within the root structures of marsh grasses.

During this feeding process, the mussels "clean" the water they live in by removing phytoplankton and the bacteria and fungi that are attached to the non living organic particles they have removed from the water column. Other undesirable particles and chemicals are bound in the mussels' pseudo feces and deposited to the bottom of the water column.

The mussel's shells provide an important substrate for algae and insect larvae to attach to. When mussels are present in large numbers, they may become underwater gardens that in turn attract fish to feed, including their host fish.

Mussels are also an important food source for several different kinds of terrestrial and aquatic animals, including raccoons, blue-claw crabs (Callinectes sapidus), and mud crabs (Panoperous herbstii), as well several species of fish and birds, including clapper rails (Rallus longirostris).

Are ribbed mussels in decline?

Ribbed mussels are tough and hardy species and mussel beds are still common in many intertidal habitats along the Jersey Shore. Ribbed mussels have adapted to constantly changing situations within an estuary. They can also close their shells to avoid short term exposure to toxins or other unfavorable environmental conditions.

Unfortunately, quite a few ribbed mussel bed populations along the northern Jersey Shore in Raritan Bay and Sandy Hook Bay, have disappeared or are slowly diminishing in number due to erosion, sea level rise, and increasing urban development that are eating away at the fringes of tidal wetlands. Erosion is increasing along seaward margins of tidal wetlands due to sea level rise and increasing intense storms from global climate change.

Studies have shown that size, growth rate, and settlement rates of mussels decrease with increasing tidal height from increasing intense storms from global climate change. High winds and winter ice can dislodge mussels from the substratum, resulting in mortality over all size classes, whereas crab predation results in the mortality of smaller mussels. TIn addition, recent studies suggest that ribbed mussels are ingesting microplastics in New Jersey tidal waters. This is having a marked reductions in growth and/or health.

Why Expand Ribbed Mussel Populations?

Extended ribbed mussel populations can help improve water quality in local tidal waters. The shellfish acts as a natural filter. Ribbed mussels constantly suck in and expel water as they consume plankton and plant particles through their gills. But mussels can also remove bacteria such as E. coli, while trapping sediment that can cloud up an estuary to suppress the growth of aquatic plant life.

Ribbed mussels are doing what a filtration plant or a wastewater plant would do for water. They are helping to purify the water.

A study in the Bronx River found that ribbed mussels removed high amounts of nitrogen from local waters. An estimated 138 pounds of nitrogen was removed from the river when the animals were harvested. “The researchers estimate that a fully populated 20 x 20 foot mussel raft similar to the one used in this study would clean an average of three million gallons of water and remove about 350 pounds of particulate matter, like dust and soot, daily. When harvested, the animals could be used for fertilizer or as feed for some animals, recycling nutrients back into the land.”

By removing suspended sediment from the water column, ribbed mussels help to improve water clarity which enhances conditions for submerged aquatic vegetation (SAV) which in turn provides habitat for a variety of other invertebrates, and fishes. Even the dead mussels are very beneficial, their shells provide tiny habitats for other bottom dwelling invertebrates, fish and a substrate for algae and aquatic vegetation. By restoring mussel populations, we are helping to improve water quality and enhance the aquatic ecosystems of our estuarine waters.  

How Can Volunteers Help?

We need volunteers to:

1) help start a small pilot program to see if ribbed mussels can be raised in local waters and

2) to survey existing populations of ribbed mussels beds for decline.

RESTORATION:

An organic frayed rope will be used to collect juvenile mussels. In late spring, mussels will begin spawning as water temperatures rise. To catch the mussel larvae, long ropes will be put in the water held afloat by buoys. The mussels float in the water until they settle down on the rope’s surface.

By fall, the mussels have grown to about half the length of a person’s thumb, and are ready to be collected for a mussel sock, or a long mesh tube that the mussels will placed inside, somewhat akin to a sock.

The mussels are roughly sorted into similar sizes before being placed in the socks. This helps maintain uniform shell sizes because the smaller mussels aren’t competing against their larger brothers. Then the mussels are stuffed into the sock. Though the mussels are on the inside of the sock now, over the next few months, they will gradually move to the outside of the sock in their continuing quest for food and nutrients. As the mussels move outwards, the sock will collapse into a thin rope in the center of the mussel column.

The mussel socks can be placed in areas where ribbed mussel beds are in decline or are nonexistent.

RIBBED MUSSEL POPULATION ESTIMATION

AREA TO BE MAPPED: Raritan Bay, Sandy Hook Bay, Navesink River & Shrewsbury River, Swimming River.

Volunteers will travel to different sites within the survey area to count the amount of ribbed mussel beds or individual ribbed mussels if the bed is small in size to do so. The bed should be measured, location to be mapped and pictures taken of each individual mussel bed.