The benthic macro invertebrate community in Caribbean Costa Rican streams and the effect of two sampling methods

Abstract

The benthic macroinvertebrate community of streams draining the south-Caribbean coasl of Costa Rica. was studied to deternine community structure and composition through time (September 1995- May 1996), the effect of vegetation cover on drainage area (forest vs. disturbed sites) and to compare two sampling methods; Surber and kitchen sieve. Five sites, predominantly with a forest cover drainage area, show abundances (mean= 157.60 in­divs./m²) and taxa richness (mean><9.65 spp./m²) significantly higher than those found in the disturbed drainage a­ reas (means--82.08 and 4.62 respectively). All sites have high community heterogeneity indices (> 0.80) which. to­gether with the low similarity indices « 0.40) between sampling times indicate a macroinvenebrate community subject to frequent disturbance eventS that diminish species permanence in the aquatic system. The kitchen sieve sampling method with ten replicates (4 000 em²) is significantly more effective in sampling the community in terms of abundance (mean=165.10) than the traditional Surber sampler (mean=83.03) using three replicates (3 333 cm²). Both are equally effective in the number of taxa collected, although each device captures different tan. The species similarity between the Surber and the sieve method ranges between 0.1379 to 0.7619 when combining all sampling times.