Longshore patterns of distribution of macroinfauna in an Uruguayan sandy beach: an analysis at different spatial scales and their potential causes


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lgimenez [ at ] awi-bremerhaven.de

Abstract

Spatial distribution of macrofaunaalong the longshore axis was studied on an exposed (Uruguayan) sandybeach in order to assess (1) its dependence on beach topography,and (2) the validity to extrapolate local distribution patterns to largerspatial scales (i.e. km). The distribution of the isopods Excirolanaarmata and Excirolana braziliensis, the sand crab Emeritabrasiliensis and several species of insects was analyzed at 3spatial scales. A grid sampling was used at small scale(intersample distance: 4 m; extension sampled: 30 to 40 m), atransect design at meso scale (intersample distance 4 to 20 m;extension sampled: 100 to 120 m), and random sampling at largescale (intersample distance: 100 m; extension sampled: 3000 m).Spatial distribution at small and meso scales were describedusing autocorrelation functions, and tested for effects oftopography at meso and large scales using ANOVA and pairedt-tests. We found that at small and meso scales the distribution ofE. armata and E. brasiliensis was patchy and affected by cusptopography. At large scales, the effect of cusp topography wasrestricted to E. armata. E. armata and E. brasiliensis showedlarge-scale aggregations, and E. braziliensis and insects showedlarge-scale patchiness associated with longshore variability insediment water content and dune characteristics. We conclude thatcusp topography affects longshore distribution patterns, and that itis not valid to extrapolate local longshore distribution to largerscales for every species. We suggest that different processesaffecting spatial distribution must be operating at different scales.At small scales, patterns of distribution may be affected by swashtransport of food and/or organisms, involving factors such as beachtopography, swash and animal movements. At larger scales, inaddition to larval and food supply, sediment transport by the windwould play an important role. Spatial patterns of sand transport bythe wind may be affected by longshore changes in vegetationcover on the dune field. We further suggest that there may be a linkbetween the beach and the dune habitats operating at large spatialscales.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
5933
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Giménez, L. and Yannicelli, B. (2000): Longshore patterns of distribution of macroinfauna in an Uruguayan sandy beach: an analysis at different spatial scales and their potential causes , Marine Ecology-Progress Series, 199 , pp. 111-125 .


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