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MEPS prepress abstract   -  DOI:

Microhabitats can be recruitment refuges and sinks

Paul E. Carnell*, Michael A. Sams, Michael J. Keough

*Corresponding author:

ABSTRACT: Recruitment is an important demographic bottleneck in the life history of many plant and animal species. Microhabitats provided by surfaces or other plants or animals can reduce mortality during this critical life-history period. We investigated how microhabitats influence post-settlement processes on a range of ascidians, bryozoans and barnacles. We compared post-settlement mortality and growth on surfaces that were flat, or were covered by artificial barnacle mimics or live adult barnacle microhabitats. We also tested whether the effects of surface type changed under different levels of environmental stress by manipulating the orientation of treatments. Orientation had the strongest influence on survival, growth and recruitment, with individuals on downwards facing surfaces performing the best, and those on upwards facing surface with significantly higher mortality. The bryozoan Watersipora had higher survival in microhabitats but was not influenced by surface orientation. In contrast, barnacles had increased mortality in microhabitats on upwards facing panels, but with no effect on the other orientations. The presence of adult barnacles caused decreased growth of barnacle recruits, but had no effect on Watersipora. In comparison, the ascidians (Botryllus and Diplosoma) were mostly not influenced by microhabitats. The high rates of sedimentation on upwards facing surfaces provide the most plausible answer for the strong influences of surface orientation on survival and growth. While microhabitats can act as refuges for some species, the same microhabitat type can lead to higher mortality in other species. The response of each species to microhabitats ultimately depends on the source of mortality at each site.