PS 51-187 - Response of freshwater shrimps to natural and anthropogenic disturbances

Background/Question/Methods

Riverine connectivity loss is a major threat for aquatic migratory species since lack of connectivity impedes them to complete its life cycle. The Anthropocene is characterized by profound human influence in the structure of all biomes including, organism community’s assembly, nutrient cycling, and rapid changes in prevailing climate at a global scale, including an increase in frequency and severity of droughts in the tropics. This geological epoch is marked by the introduction of novel disturbances never experienced before by natural communities like dams. The primary goal of this study is to understand how dams and drought disturbances influenced freshwater migratory species in Puerto Rico and other tropical countries. We focused primarily on Puerto Rico native taxa since both freshwater shrimps and fish have migratory life history. Also, shrimp become the dominant consumers on mountainous streams devoid of fish and play a critical role in nutrient cycling. a) To understand the effects of dams on freshwater shrimps and fish we did a literature review focused on Puerto Rico and other tropical countries. b) To determine the effects of tropical droughts on shrimps we analyzed weekly rainfall and shrimp data from the Luquillo LTER at Quebrada Prieta (EYNF) from 1993 to 2016.

Results/Conclusions

Dams severely affected migratory species of both shrimp and fishes by disrupting stream connectivity and producing a “bottleneck” effect. Dams without spillways inhibit aquatic fauna migration resulting in population declines or absence above or below dams depending on the species. In streams devoid of fish and shrimp abundance was strongly associated with pool size. Literature review showed that droughts can have strong effects on aquatic communities particularly in the upper parts of the drainage basin driven by habitat fragmentation and hydrological connectivity loss. But droughts did not have lasting effects on amphidromous shrimp abundance at pools studied at 400m above the sea level in EYNF since there abundance bounced back couple weeks after a drought ended. Result shows that as long riverine connectivity is maintained or quickly re-establish after a drought migratory species can bounce back and continue to thrive, thus our effort should focus in re-establish habitat connectivity that facilitate native species migration at the dam’s location.