ABSTRACT: The hypothesis that passive processes control larval settlement of benthic marine invertebrates on 3-D structures was tested for several groups at both meso (3 cm) and small (mm, µm) scales. Flume experiments were carried out with inert polyvinylchloride microparticles and 5 different types of silicone-coated 3-D arborescent plastic structures with 5 distal branch diameters. Microparticle attachment as a function of the distal branch diameter and the proportion of particles attached to the nodal section of each branch were used to predict the initial contact site by living marine benthic invertebrates larvae in field experiments using the same 3-D structures immersed for 2 mo. The flume experiment showed that distal branch diameter had a significant effect on the density of attached particles. The proportion of particles observed in the nodal sections (8%) was much lower than the proportion of the total surface area occupied by the nodes (20%) on each branch. Field experiments examining recruit density (6 sessile species belonging to 4 classes of marine invertebrates) on the same 3-D structures showed the same significant effect of the distal branch diameter observed in the flume. However, individuals were found in the nodal sections much more frequently (35 to 80%) than would be expected based on the results of the flume experiment (8%). Comparison of results of laboratory and field experiments suggests that passive settlement processes are sufficient to explain early recruitment patterns of the species examined on scales ca 3 cm. However, at smaller scales (ca mm) the hypothesis of active larval exploration of the substratum could not be rejected. The likelihood of post-settlement mortality processes potentially explaining the patterns observed is discussed.

KEY WORDS: Larval settlement · Recruitment · Benthic invertebrates · Field experiment · Flume experiment · Passive and active processes

Published in MEPS Vol. 153 (1997) on July 10
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997