MEPS 540:43-55 (2015)  -  DOI: https://doi.org/10.3354/meps11483

ABSTRACT: Much present knowledge about the role of physical factors in structuring reef communities is based on correlative data and small-scale experiments. The construction of a 9 ha artificial reef off southern California allowed a novel opportunity to experimentally examine at a realistic scale how the physical attributes of a reef (i.e. the amount, type, orientation, and physical location of hard substrate) are correlated with the colonization and subsequent development of sessile biota in a giant kelp Macrocystis pyrifera forest. The percent cover and slope of hard substrate were significantly related to the abundance and species richness of both understory algae and sessile invertebrates. The abundance and richness of colonizing algae were significantly related to location (i.e. proximity to the nearest natural reef), while that of sessile invertebrates was not. The type of hard substrate (quarry rock vs. concrete rubble) was unrelated to the abundance and diversity of either algae or invertebrates at any time during the 5 yr study. Physical attributes collectively explained between 16 and 40% of the variation in the abundance and diversity of the benthic community, depending on the taxon and time period examined. Variations explained by physical factors were greater in the first year during initial colonization than after 5 yr, when giant kelp was fully established. The construction of the artificial reef was akin to a large disturbance that created free space. Our findings suggest that physical attributes of reef structure may play a key role in structuring reef communities following a disturbance, but their importance diminishes over time as ecological interactions involving established reef organisms become increasingly important.

KEY WORDS: Artificial reef · Colonization · Competition · Disturbance · Dispersal · Kelp forest · Understory algae · Sessile invertebrates