Oysters

Oysters are a group of edible bivalve mollusks in the family Ostreidae. They inhabit marine and brackish waters and are valued for their meat and, in some regions, for pearls. The most commonly cultured and consumed species include the Pacific oyster (Crassostrea gigas) and the Eastern oyster (Crassostrea virginica).

Biology and life cycle: Oysters have two hinged shells that enclose a soft body. They are filter feeders, extracting plankton and organic particles from the water. Many oysters attach themselves to hard substrates by secreting a cement-like substance, forming dense aggregations or reefs. Most oysters are hermaphroditic or sequentially hermaphroditic, and they typically reproduce by releasing sperm and eggs into the water column (broadcast spawning). The fertilized eggs develop into free-swimming larvae (trochophore and veliger stages) before settling as juvenile oysters that grow into adults.

Habitat and ecological role: Oysters are common in coastal and estuarine zones with hard substrates. Oyster reefs provide habitat for other species and contribute to water quality through filtration, which can enhance clarity and nutrient cycling. They are also sensitive to environmental changes, including salinity and temperature shifts.

Human use, production, and nutrition: Oysters are widely harvested commercially and also farmed through aquaculture. They are consumed raw or cooked and are a source of high-quality protein, minerals such as zinc, and vitamins. Handling raw oysters requires care due to potential bacterial risks; cooking reduces associated hazards.

Threats and conservation: Oyster populations face overharvesting, habitat destruction, pollution, and climate-related stressors such as ocean acidification. Diseases and invasive species can also impact wild and farmed stocks. Restoration efforts, including reef reconstruction and improved water quality, aim to support oyster populations and their ecological services.