Feeding Relationships

All animals need to be able to have access to food. If animals do not eat, they die. In an intertidal environment, food is not available to all creatures all of the time.

When the tide is low, most high- and mid-shore animals uncovered by the receding water, must either hide themselves away, close their operculums across their shell opening, secrete a mucous ring around the edges of their shell, to protect themselves from the desiccating rays of the hot sun.

Most intertidal animals can only feed when the tide is in. The larger filter feeders, such as the sponges, large barnacles such as the Giant Rock Barnacle, Balanus nigrescens, and large bivalves, Edible Mussel, Mytilus edulus planulatus, occur on the lower shore so that they are submerged for long periods of time.

Smaller filter feeders, such as the Honeycomb Barnacle, Chamaesipho tasmanica, and the Six-plated Barnacle, Chthamalus antennatus, can occur quite high on the shore, only covered by the tide for a few hours each day.

There are a number of feeding strategies that algae and animals of the rocky ocean shore have adopted. Some of these are:

• Nutrient absorbers: these are the energy and nutrient absorbing algae. These are the Primary Producers.
• Grazers and Browsers: these are the molluscs which eat micro- and macroalgae. These are the Herbivores, or should they be called Algavores.
• Suspension feeders: These are the Plankton feeders.
• Deposit Feeders: These are the Detritus feeders.
• Carnivores: These are the meat-eating hunters. First-level Carnivores eat Herbivores. Second-level Carnivores eat First-level Carnivores. Carnivores includes Parasitism.
• Omnivores: Eat a range of food types, but mostly carrion and debris.

References:

Bennett, I. (1987) W. J. Dakin's classic study: Australian Seashores. Angus & Robertson, Sydney.

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia. New Holland, Sydney.

Edgar, G. J. (1997) Australian Marine Life: the plants and animals of temperate waters. Reed Books, Kew.

Quinn, G. P., Wescott, G. C. & Synnot, R. N. (1992) Life on the Rocky Shores of South-eastern Australia: an illustrated field guide. Victorian National Parks Association, Melbourne.

Marine Research Group of Victoria (1984) Coastal Invertebrates of Victoria: an atlas of selected species. Museum of Victoria, Melbourne.

Shepherd, S. A. & Thomas, I. M. (1982) Marine Invertebrates of Victoria, Pt. 1. South Australian Government Printer, Adelaide.

Underwood, A. J. & Chapman, M. G. (1993) Seashores: a beachcomber's guide. New South Wales University Press, Sydney.