Cockles' role in food webs

Educational value

• Cockles are a type of bivalve mollusc that live in shallow waters, buried in the soft mud or fine sand of sand flats, eelgrass beds and estuaries. Cockles are filter feeders that sieve microscopic plankton from the water in which they float. As a filter feeder, cockles may accumulate toxins from the environment, which can provide evidence of marine pollution.
• The New Zealand cockle ('Austrovenus stutchburyi'), also known by its Māori names, tuaki or tuangi, is found only in coastal areas of New Zealand. It has a thick heavy shell that protects it from predators and from drying out. Cockles in Doubtful Sound, New Zealand, have been affected by changes in salinity in an area where fresh water is being pumped from a hydroelectric power plant.
• Cockles play an important role in marine food webs and their removal from an area can have significant effects all the way up through the food web. Cockles feed upon, and therefore obtain their energy from, plankton, a primary producer. Cockles are in turn eaten by a range of marine animals including lobsters and birds; however, if the number of cockles declines, the flow of energy through the food web can be significantly altered.
• Associate professor Stephen Wing is a lecturer and researcher at the University of Otago, New Zealand. He is a marine biologist with a special interest in food webs and conservation biology of marine ecosystems. Much of his research is undertaken in southern New Zealand including the remote and pristine Fiordland region.

Topics Bioindicators Food webs Energy flow (Ecosystems) Human impact Clams Marine biologists