What are bivalves? What do they look like?

Clams, oysters, and mussels are a part of the bivalves class, a group of invertebrates found in aquatic habitats. They are soft-bodied animals that have two hard outer shells covering their bodies that open and close like a door. They have darker blue or black shells and are usually wedge-shaped or pear-shaped. Clams can't breathe in an air environment, but when they are out of the water the two halves of their shell will seal up tightly to prevent dehydration, they can survive like this for months to years. Mongolian mussels are around 10-30 cm long and 200-1000 g in weight, adapted to live in the sand of lakes and rivers. They can move slowly with the help of their muscular feet. It is said that they can feel water, light, and darkness but are incapable of forming thoughts or feelings as they have no brain. When they are ready to reproduce in the summer, the male and female mussels release their gametes (eggs and sperm) into the water, where the two mix and produce a fertilized egg.

Where are they found?

Bivalves can be found in fresh waters and salt waters. They spend most of their life living in oxygen-rich bottoms of small areas in lakes or stream beds such as soft-flowing rivers and lake bays with silt and sandy sediments. In Mongolia's Buir Lake, we can find Dahurinaia Dahurica and Cristaria Plicata, which are included in the Red Book of Mongolia. Also, the Mongolian oyster (Middendorffinaia mongolica) is found in the Onon, Balj, Khalkh, and Nymrog river basins.

Types of Bivalves?

• элт танан хясаа (Cristaria plicata)-red
• сувдан хясаа (Dahurinaia dahurica )-red
• Монгол танан хясаа (Middendorffinaia mongolica)

Why are Bivalves important?

Bivalves are ecosystem engineers, they help purify the aquatic system making it more suitable for themselves and other organisms. It is said that 1 mature oyster cleans approximately 190 liters of water in 5 hours. They bring three environmentally beneficial services to the ecosystem- water filtration, nitrogen removal, and carbon storage.

1 Water filtration

A single littleneck-sized clam can filter 4.5 gallons of seawater per day.

As clams feed, they move water in and out of the animal with a current. Tiny moving cilia, pump water through the clam, drawing it in. The gills capture particles and move them to the mouth for ingestion. The cleared water is then excreted. By feeding, clams filter phytoplankton (microscopic algae or plants), and microorganisms. They improve water by removing excess nutrients from water. Clearer water allows more sunlight to enter, which helps the growth of important seagrasses and increases oxygen.

2 Remove nitrogen

A single littleneck-sized clam can remove 0.09 grams of nitrogen from the water.

Clams play an important role in reducing nitrogen. They do not directly absorb nitrogen from the water but feed on the phytoplankton (microscopic algae or plants that dissolve inorganic nitrogen to grow). It is said that they take in nitrogen into their tissues and shells allowing nitrogen levels to reduce. In addition, clams also play an important role in the cycling of nutrients. For example, some of the nitrogen filtered from the water can be excreted as feces, this cycling of nutrients allows another organism to use it.

3 Remove carbon

A single littleneck-sized clam can store 2.76 grams of atmospheric carbon

Clams convert carbon into calcium carbonate shells. Carbonates are obtained from the atmospheric carbon dioxide that are usually dissolved in water. Therefore, they absorb more carbon from the atmosphere than they release. Not only do they store carbon they also produce carbon dioxide as a waste product like other animals. When they excrete carbon as feces it is consumed by a variety of organisms for cycling of nutrients.

Endangerment-threat
40% of the species being near threatened, threatened or extinct