Poster Presentation Society for Freshwater Science 2025 Annual Meeting

The effects of road-stream crossings on the aquatic macroinvertebrate assemblage structure. (117952)

Ismael Orengo Sanchez 1
  1. Universidad Ana G. Mendez & Estacion Experimental Agricola UPRM, Trujillo Alto, PUERTO RICO, Puerto Rico

Road-stream crossings, also known as bridges and culverts, alter the aquatic habitats and the macroinvertebrate assemblages by replacing natural substrates with concrete surfaces at streams. Studies performed at temperate streams demonstrated that the macroinvertebrate response towards the presence of road crossings consist of a change on the macroinvertebrate assemblage structure and a reduction on the abundance and richness values.  Unlike temperate streams the response of tropical streams towards the presence of road crossings has received little attention. Therefore, the aim of this study is to compare the macroinvertebrate assemblage structure and the abundance between stream sections (upstream, bridge and downstream) at four tropical streams representing three types of road crossing designs (Circular Concrete Culvert, Concrete Box Culvert, Concrete Slab Bridge). An analysis of similarities (ANOSIM) was used to compare the composition of the macroinvertebrate assemblages between stream sections. In addition, a Wilcoxon Rank Sum test was performed to compare the abundance between sections. The results of the ANOSIM test demonstrated that the macroinvertebrate assemblage structure was similar in structure and composition among stream sections during dry and wet seasons. On the other hand, the Wilcoxon test showed that the abundance from the bridged and culverted sections does not differ to the abundance of natural reaches (upstream and downstream) during the wet season. However, a different result was obtained during dry season since the statistical analysis demonstrated that the abundance from the bridged section differed to the abundance from the natural sections.