The vertical distribution and habitat of the ascidians in Borgenfjorden, North-Tröndelag, Norway

Abstract

Six ascidian species were sampled from 4, 8, 12, and 16 m depth along seven line transects. Styela conacea and Styela rustica were most specific as to depth requirements. S. coriacea had the highest densities just below the algal belt and S. rustica preferred the deepest stations. Ciona intestinalis, Dendrodoa grossularia, Corella parallelogramma, and Molgula siphonalis seemed to be less particular about depth, and other factors like substrate, nutrition, and current may be more important for the distribution.