The relationship between dissolved oxygen concentration and maximum size in deep-sea turrid gastropods: an application of quantile regression

Bathymetric gradients in body size are the most well-known patterns of geog raphic variation in deep-sea organisms. The causes of size-depth relationsh ips remain uncertain, but most have been attributed to rates of nutrient in put. Chapelle and Peck (1999, Nature 399:114-115) recently hypothesized tha t body size in marine invertebrates is a function of dissolved oxygen conce ntration. We tested this hypothesis by using quantile regression techniques to assess the relationship of dissolved oxygen levels to maximum size in d eep-sea turrid gastropods collected from the North Atlantic. Relationships were examined for a group of nine turrid species and within the abundant lo wer bathyal species Benthomangelia antonia (Dall, 1881). We controlled the analysis for depth because size in deep-sea gastropods varies bathymetrical ly. When the effects of depth are accounted for statistically, maximum size in B. antonia increases with increasing levels of dissolved oxygen. In tur rids as a group, both depth and oxygen appear to explain significant propor tions of the variance in maximum size. These findings suggest that a suite of factors, including dissolved oxygen concentration, may influence maximum size in deep-sea organisms.