Abstract
Crustaceans associated with Ecklonia radiata holdfast have long been used as the indicators of environmental change and habitat suitability. Despite this important ecological role, no work has been done to document the spatial variation patterns of crustaceans in the Wild Coast of South Africa. This study examined the site and habitat effects on holdfast-associated crustacean community composition and documented physical factors underlying observed patterns. Eighty-four kelp holdfasts produced a total of 1379 individuals among 32 distinct species. Significant positive correlations between total abundance and species richness were prominent in rock pools compared to gullies in most sites. There was a significant interaction effect of site and habitat on species richness. Dwesa gullies had a significantly higher number of species compared to their adjacent rock pools and Xhorha gullies. The total abundance and Shannon diversity differed within Dwesa (gullies vs. rock pools). The composition of crustaceans per holdfast differed significantly between habitats and across sites. Seven clusters were identified, each defined by distinct species. Most gullies were primarily inhabited by barnacles Amphibalanus venustus, while isopod Cymodocella pustulata dominated the rock pools. Rock pool species were mainly associated with high temperatures and enhanced sodium levels, while the gully species were positively associated with microhabitat characteristics and nitrate. Our findings show that Dwesa gullies had pronounced effects on crustacean biodiversity metrics. Crustaceans in the gullies were mainly driven by nitrate, holdfast, and sediment weight, while rock pool dwellers were characterized by enhanced temperature and sodium.