Growth rates ofLithophyllum incrustans(Corallinales, Rhodophyta) from South West Wales

Growth rates of Lithophyllum incrustans, a rock-encrusting coralline red alga, have been studied at three sites on the coast of Pembroke, south-west Wales. Horizontal and vertical growth rates and calcium carbonate deposition rates were determined. There are some significant differences between sites, especially in vertical growth rates which include the formation of reproductive tissue. The data indicates that L. incrustans is, on average, 2·25 years old before reproduction is initiated. Growth rates of this alga were found to be similar to other arctic and temperate encrusting red algae, but an order of magnitude less than those in the tropics.