The Blue Planet - Tidal Seas

This episode deals with marine life that is structured around the rising and falling tides. These are caused by the gravitational pull of the orbiting moon, but in some locations, this can also combine with the power of the sun to create a tidal bore. The world’s largest tides are to be found in the Bay of Fundy in Nova Scotia and therefore it is a rich feeding ground. A school of finback whales is closely shadowed by a flock of Cory’s shearwaters. However, they only have a limited time to feed before low tide, when they must retreat and other creatures appear. Elsewhere, some of the latter include sand bubbler crabs, bears (which feed on shellfish) and a snail species that can ’surf’. The extreme spring tides allow opportunists to forage further, and racoons are shown tackling a red rock crab. Some larger fish that hunt on the seabed, such as nurse sharks and stingrays, are forced to sit and wait until there is sufficient water in which to swim. A giant horse conch is shown devouring a tulip snail, and hermit crabs battle over its vacant shell. The varying water levels are no obstacle to tarpon: they can breathe air. This enables them to inhabit stagnant areas and hunt in them. The autumn equinox combines with a hurricane off the Bahamas to create a much higher tide than is usual, flooding large parts of the coast. When the sea recedes, it leaves behind salt: food for brine shrimps and the perfect habitat in which flamingos can breed.