At low tide on Brighton Beach, you might notice clusters of dark-shelled creatures clinging stubbornly to the groynes, pier supports, or even scattered rocks. These are blue mussels (Mytilus edulis), nature’s little ocean purifiers and master survivalists. They begin life as microscopic larvae, drifting aimlessly in the currents after being released into the water during spawning. Males and females release sperm and eggs into the water, and fertilisation occurs externally, forming a free-swimming larva called a trochophore.
For the next two to four weeks, these larvae progress into veligers - tiny, shelled planktonic creatures that continue to drift with ocean currents, feeding on microscopic algae. After several weeks, they reach the pediveliger stage, developing a small foot and searching for a suitable hard surface to settle on, such as rocks, pier pilings, or even other mussels. Once they find a home, they attach using sticky byssal threads and undergo metamorphosis into juvenile mussels.
Juveniles grow rapidly in nutrient-rich waters, reaching full size (5-10 cm) in about two to three years. In favourable conditions, blue mussels can live up to 15 years. They often crowd in dense colonies, forming mussel beds that can contain thousands to millions of individuals. These beds can stretch across large areas of rocky shorelines, pier supports, and other hard surfaces. The tightly packed arrangement helps protect them from predators and harsh wave action.
Mussels may seem passive, but they are essential to the marine ecosystem. A single mussel can filter up to 10 litres of seawater an hour, sifting out microscopic plankton and removing pollutants. In some places, mussel beds are even used to help purify water naturally. Their resilience is remarkable. At low tide, they clamp their shells shut to avoid drying out, sometimes surviving for days without water. They can also change sex depending on environmental conditions, optimising their chances of reproduction. And, if they ever need a change of scenery, some mussels can detach and ‘walk’ using their foot to seek a better home. Much more information is available at Wikipedia and the Marine Life Information Network.While Brighton’s blue mussels are fascinating, other species of mussels have their own quirky traits.
The Deep-Sea Giants: The Bathymodiolus genus of mussels, found near hydrothermal vents, can grow up to 30 cm long - dwarfing their shallow-water relatives!
The Oldest Mussels: Freshwater pearl mussels (Margaritifera margaritifera) can live over 100 years, with some recorded at nearly 250 years old!
The Strongest Glue: The Mytilus californianus (California mussel) produces an adhesive so powerful that scientists are studying it to create waterproof medical glue.
The Fastest Growers: Green-lipped mussels (Perna canaliculus) from New Zealand can reach full size in just one year - much faster than blue mussels.
Mussels That Save Lives: Some mussel species are used in water filtration projects to clean up polluted waterways, acting as natural biofilters.