Macroinvertebrate vulnerability to drought and hurricanes in forested streams in Puerto Rico

Climate change models predict an increase in the frequency of droughts and the intensity of hurricanes for the Caribbean. The objective of this study was to evaluate and contrast the macroinvertebrate assemblage response of a forested stream to drought and hurricane disturbances. Puerto Rico experienced a drought event in 2015 and two major category hurricanes in September of 2017 (hurricanes Irma and María; Categories 5 and 4, respectively). We evaluated macroinvertebrate richness and abundance of two headwater streams (Quebrada Prieta A and B) located in the El Yunque National Forest, Puerto Rico. Monthly macroinvertebrate sampling was carried out using corers in pool habitats from October 2016 – August 2019 in QPA and from February 2014 – August 2019 in QPB. Analysis of similarity (ANOSIM) was performed to compare macroinvertebrate assemblage structure among pre-drought, post-drought, pre-hurricane, post-hurricane, and short-term post-hurricane periods. Drought conditions resulted in an increase for both richness and abundance compared to the pre-drought and post-drought periods. Immediate hurricane impacts (September 2017) resulted in a decrease in both richness and abundance compared to other hurricane periods. The new environmental conditions created by the drought did not result in significant differences between the compared periods, while those created by the hurricanes did result in significant differences between the macroinvertebrate assemblage structures of the compared periods. Evaluating the biotic response of benthic communities to these disturbances is critical to understand how future climate change conditions will impact the fauna of protected tropical zones.