ABSTRACT
On the Spermonde Shelf, SW Sulawesi (Indonesia) four parallel running zones can be distinguished which differ in their distance to the mainland. In seaward direction, terrigenous influences (river inflow) decrease whereas oceanic influences (wave energy, upwelling) increase. Densities of regular sea urchins were measured at different reef zones in 9 transects with the help of 25×2 m2 belt quadrats. Three parameters were important with respect to species abundance: (1) distance offshore, (2) orientation of the reef site with respect to the predominant wind direction and (3) depth. Species numbers increase in offshore direction until the third shelf zone. Some species have highest densities in the third shelf zone whereas others occur most abundantly in the fourth zone. This suggests that distance of the reefs to the mainland and the open sea plays a role in echinoid species distributions and abundances.
