Macro-Consumer Roles in Benthic Organic Matter Processing in a Tropical Stream

A common characteristic recorded in tropical streams is a “paucity” of shredding insects. The importance of shredders in breaking down course benthic organic matter (CBOM) in temperate streams is well understood, but few studies have tested hypotheses addressing how that role is fulfilled in tropical streams. This problem is compounded by the heterogeneous nature of tropical streams. Research in island or old world tropical streams may not be applicable to neotropical streams or each other, however, previous research has indicated that macroinvertebrate shredding species increase with altitude, while microbial activity breaks down CBOM in lowland streams. I placed electrical exclusion equipment in the Java river located at Las Cruces Biological Station in Costa Rica, at an elevation 1100m to discern the impact of macro-consumers such as fish and decapods on leaf decomposition rates and invertebrate community structure. Results indicated that neither macro-consumers, nor insects were significantly involved in the breakdown of leaf litter in the Rio Java.