We examine evidence for links between seafloor spreading rate and properties of vent habitat most likely to influence species diversity and other ecosystem properties. Abundance of vent habitat along spreading centres appears positively related to spreading rate while habitat stability shows an opposite relationship. Habitat heterogeneity is lowest at faster spreading ridges. Limited data indicate an increasing species diversity with spreading rate, complicated by historical factors. Ecosystem productivity and efficiency of resource utilisation may also reflect diversity differences.

Introduction

In explaining organism distribution or in quantifying flows of energy and materials, ecologists are confronted with changing communities whose component populations shift as do interactions with the environment. Fitting patterns to observed changes and formulating predictive models are important elements of contemporary ecology. How we examine a novel system, like that of deep-sea hydrothermal vents, depends partly on our a priori beliefs on what the important controls will be. Explanations of community composition and structure include three fundamental view-points: (1) control through biological interactions such as competition and predation; (2) control through environmental limitations such as energy supply or growing conditions; and (3) influence of historical events (see Real & Brown 1991). Their relative importance seems to vary depending upon the system under study, as well as the spatial and temporal scales being examined.

The hydrothermal vent ecosystem requires the chemical energy present in discharging fluids. Distribution of vent communities is thus controlled by the mantle and crustal processes that determine the nature and distribution of hydrothermalism.