نبذة مختصرة : Tropical rivers are exposed to the pressures exerted by the rapid growth of urban areas, increasing the discharge of organic nutrients; added to the effects of climate change, such as extreme temperature events, rainfall or hurricanes. As a result of climate change, extreme events are projected to be more intense, potentially generating drastic changes in ecosystems. For example, in the Caribbean, one of the most prolonged droughts was recorded in 2015. Likewise, Hurricane María was the most intense hurricane in 2017, with severe effects mainly in Dominica and Puerto Rico. The objective of this work was to determine and contrast the impact of drought and hurricane on the assembly of aquatic macroinvertebrates in a tropical urban river to understand their vulnerability to climate change. We carried out the study in the Río Piedras, a basin that drains the San Juan metropolitan area, where the most extensive urbanization in Puerto Rico is concentrated. We carried out periodic samplings between 2014 and 2018, physicochemical and hydrological variables were recorded, and macroinvertebrates were sampled. The results show that drought has a more significant effect on the assembly of macroinvertebrates compared to the hurricane. After drought events, the abundance of macroinvertebrates decreased, and their composition differed significantly from previous samples. On the contrary, the abundance and composition of macroinvertebrates recorded after Hurricane Maria were similar to that reported in previous samplings. Although hurricanes cause flooding, macroinvertebrates appear to be adapted to these disturbances; while drought causes unusual conditions, causing changes in the macroinvertebrate assembly. Given the predictions of climate change for the Caribbean, the increase in drought events is expected to have more drastic impacts on urban river ecosystems.
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