PARENT SESSION
Poster Session 4: Marine Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Abundance distribution of benthic intertidal species: an analysis using spatial scale relations.

Cabrera, Lina^*,1, Ardisson, Pedro^*,1, Pech, Daniel^*,2, ¹ CINVESTAV-IPN, Merida, Yucatan, Mexico² Québec-Océan, Québec, Québec, Canada

ABSTRACT- Scale relations based on quantitative comparisons of grain and extent constitute an advantageous approach to assess the variability in the biological attributes of populations and communities. Here, the utility of this approach is illustrated examining the abundance distribution of intertidal benthic invertebrate species from a tropical zone, as a continuous function of spatial scale. The barnacle Chtamalus angustiterum and the bivalve Brachidontes exustus were used with this purpose. Abundance data were collected on contiguous 5 x 10 cm quadrats along three 100-m transects. Firstly, the appropriate scale of observation for each species (the one explaining the highest proportion of variance) was detected using semivariance analysis. Lately, comparisons between scales were made using the following spatial grain and extent relations: hierarchical, intersecting hierarchical, nonintersecting hierarchical, adjacent hierarchical, nested extent, and nested grain. Preliminary results showed that the proportion of the explained variance was species specific and was higher (80 to 90%) at scales smaller than 4 m. Results also showed a nested extent relation between abundance of species. This study provides a straightforward demonstration of how dependent the scale perception is on the particular combination of grain and extent considered in field sampling designs.

Key words: scale, variance, Chtamalus angustiterum, Brachidontes exustus