MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 232:239-246 (2002) - doi:10.3354/meps232239 Fish-seaweed association on temperate reefs: do small-scale experiments predict large-scale patterns? Phillip S. Levin1,*, Mark E. Hay2 1Northwest Fisheries Science Center, National Marine Fisheries Service, 2725 Montlake Boulevard E, Seattle, Washington 98118, USA 2School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332-0230, USA *E-mail: phil.levin@noaa.gov ABSTRACT: Processes affecting reef fish populations are likely to vary with spatial scale, but there have been few attempts to determine whether predictions generated by small-scale experiments are manifested at larger spatial scales. Our goal in this study was to determine if patterns of microhabitat use measured in small-scale experimental manipulations scaled-up and allowed predictions of among-reef patterns of abundance across larger spatial scales. Manipulations of algal biomass in artificially created 1.5 m2 plots indicated that patches of Sargassum filipendula supported greater numbers of slippery dick Halichoeres bivittatus than those with an equal biomass of Zonaria tournefortii, or than patches with an equal mix of S. filipendula and Z. tournefortii. Scaling up and manipulating S. filipendula and Z. tournefortii abundance in 100 m2 sections of reef produced results qualitatively similar to the small-scale experiments; fish densities varied as a function of S. filipendula mass. Larger scale surveys of fish densities and algal biomass on large reefs separated by 1 to 30 km showed positive associations between fish density and S. filipendula biomass. For the reefs that we studied, our small-scale experiments scaled up and predicted large-scale patterns of abundance on reefs in the South Atlantic Bight. KEY WORDS: Reef fish · Temperate reef · Habitat structure · Macroalgae · Scale · Recruitment Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 232. Online publication date: May 03, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.
Because seaweeds uncontrolled by herbivores can overgrow and kill corals, competition can exclude corals from temperate latitudes where herbivores generally fail to control seaweed biomass. In this study, we show that the coral Oculina arbuscula persists on reefs in temperate North Carolina where seaweeds are common by harboring the omnivorous crab Mithrax forceps, which removes seaweeds and invertebrates growing on or near the coral. In the field, corals from which crabs are experimentally removed develop a dense cover of epibionts, exhibiting reduced growth and increased mortality relative to corals with crabs, which remain epibiont-free. This crab is unusual in that it readily consumes all local seaweeds in laboratory choice assays and is not deterred by chemical defenses that suppress feeding by local fishes, sea urchins, and other crabs. This allows Mithrax to defend corals from overgrowth by chemically noxious seaweeds like Dictyota and Sargassum that are avoided by most local herbivores. However, further field manipulations under reduced light conditions demonstrate that the outcome of the crab-coral interaction is context-dependent: crabs only benefit corals in well-lit areas where seaweeds are abundant. Field observations and tethering experiments show that, by living in association with Oculina, Mithrax gains a refuge from predation. Additionally, crabs grow faster when associated with live corals than with structurally equivalent dead corals, apparently because they are able to consume lipid-rich coral mucus. This mucus provides a dietary supplement that may help corals attract and retain low-mobility symbionts such as Mithrax, securing for the coral long-term and predictable protection against competitors. Structurally complex but competitively inferior organisms, like some corals and coralline algae, provide the biogenic habitat complexity upon which many other species depend. Because these sessile organisms may be dependent on symbionts to remove superior competitors, mutualisms can play an important, but currently underappreciated, role in structuring marine communities where biotic interactions are intense. In this study, the mutualism between Oculina and Mithrax promotes the persistence of both species in habitats from which they might otherwise be excluded by competition and predation.
A table and reference list for studies used in the analyses.
Marine Protected Areas (MPAs) are often established to mitigate the effects of overfishing and other human disturbances. In Fiji these are locally managed and, where enforced, have significantly higher coral cover, higher fish biomass, and lower seaweed cover than in the adjacent, unprotected reefs (non-MPAs). We investigated how the isotopic signatures of a common, mid-level consumer, <i>Epinephelus merra</i>, differed among three small (0.5- 0.8km<sup>2</sup>) MPAs versus adjacent, unprotected reefs. Isotopic ratios suggested that the fish in the MPAs fed higher in the food chain than those in the adjacent non-MPAs, despite being slightly smaller in size. Calculations using a brown alga as representative of the basal level of the food chain estimate this difference to be about half a trophic level. Thus, the isotopic ratio of a mid-level consumer can be noticeably altered over scales of only a few hundred meters. This may result from more complete food webs and hence greater prey choice and availability in the MPAs and implies that MPAs affect not only species' abundance and diversity, but also diet composition and trophic biology of member individuals. Our findings suggest <i>E. merra</i> exhibits considerable site fidelity in its feeding biology and thus provides a localized isotopic signal of its reef of residence. If the isotopic signal of this mid-level carnivore is reflective of the composition of the food web beneath it, the signal might provide an easily obtained indication of reef conditions in that area.
