Mercenaria mercenaria, commonly known as the hard clam or quahog, inhabits the sandy and muddy substrates of the Atlantic coast of North America. It is a bivalve mollusk with a thick, rounded shell and is known for its filter-feeding behavior, playing a vital role in water purification and ecosystem balance.

Mercenaria mercenaria, commonly known as the hard clam or quahog, is native to the eastern coast of North America. Its geographical distribution extends from the Gulf of St. Lawrence in Canada down to the Gulf of Mexico in the United States. It is most commonly found along the Atlantic coast, particularly abundant in the northeastern United States.

The hard clam typically inhabits coastal and estuarine environments. It prefers sandy or muddy substrates where it can burrow and remain partially buried. The species thrives in saline to brackish waters, with salinity levels ranging from 18 to 35 parts per thousand. Optimal water temperatures for Mercenaria mercenaria are between 10°C and 25°C, aligning with temperate climates.

Mercenaria mercenaria plays a significant role in the coastal ecosystem as a filter feeder. It contributes to water filtration and clarity by feeding on plankton and organic particles. The species is often found in shallow waters, typically at depths of up to 15 meters, where it can efficiently access food resources. Its ability to adapt to various salinity levels allows it to occupy diverse estuarine habitats.