Modular growth of a gorgonian coral can generate predictable patterns of colony growth

Abstract

The modular construction of colonial organisms can generate complex growth patterns that incorporate both growth and partial mortality. These patterns often confound simple age based descriptions of growth but, in some cases, modularity can generate predictable patterns of colony growth that are amenable to modeling approaches more commonly used in unitary organisms. Colonies of the Caribbean gorgonian Pseudopterogorgia elisabethae from a 20 m deep population in the Bahamas exhibit such characteristics. Mass was highly predictable from colony height, following a power function with an exponent of 2.1. Age, as determined from counts of annual growth rings was a good predictor of height and mass. The relationship between age and height was modeled using a Von Bertalanffy growth curve. Growth models from both the age:height relationship and from extrapolations of colony growth rates from another Bahamian population yielded similar but more variable results. Based on those data and previously published observations of spawning and survivorship, colonies reach sexual maturity at 5–7 y and can live to over 40 y. Using the Von Bertalanffy function to estimate ages from height facilitates interpretation of size frequency distributions and suggested enhanced recruitment on San Salvador Island following the passage of Hurricane Andrew in 1992. Although simple growth models do not characterize the variance inherent in modular growth, these models can provide useful tools for the interpretation of population data.