Oral Presentation Freshwater Sciences 2023

Resistance and resilience of stream ecosystems to climate extremes: lessons from tropical mountain streams (#535)

Pablo E. Gutiérrez-Fonseca 1 , Alonso Ramirez 2 , Cathy M Pringle 3 , Jesus Gomez 4 5 , Pedro J Torres 6 , Alan Covich 3 , Todd Crowl 5 , Bill McDowell 7 , Omar Perez 4
  1. University of Vermont, Burlington, VERMONT, United States
  2. Department Applied Ecology, North Carolina State University, Raleigh, North Carolina , USA
  3. Odum School of Ecology, University of Georgia, Athens, GA, USA
  4. Department of Environmental Sciences, University of Puerto Rico-Río Piedras, San Juan, Puerto Rico, USA
  5. Department of Biological Sciences, Florida International University, Miami, Florida, USA
  6. Biology Department, Holy Cross College, Worcester, MA, USA
  7. Department of Natural Resources and the Environment, University of New Hampshire, Durham, New Hampshire, USA

Extreme climatic events are recognized as major regulators of ecosystem dynamics, driving changes in ecosystem structure and function. However, the unpredictability of naturally occurring climate extremes limits our assessment of their ecological impacts. In order to capture these events in real-time, we have been monitoring multiple ecosystem variables in tropical mountain streams for a few decades.  Our ongoing research project has allowed us to capture stream ecosystem responses to two extreme climate events; the 2015 drought (the most severe drought in the last 5 decades) and the 2017 hurricanes (hurricanes Irma and Maria, two major hurricanes).  Comparatively, we observed that both events created a peak in leaf litterfall input of ~7 fold compared to the long-term average (1g/m2/d), but the chemical composition of the leaf litter differs substantially.  Highly mobile decapods increased in abundance during the drought, while we observed a delayed response during hurricanes, possibly due to the recovery time after flooding and consequent wash-out.  Primary producers were negatively affected by the drought, while they did not respond to the increase in solar radiation due to massive defoliation by the hurricanes.  Macroinvertebrate responses to both events varied according to their functional traits. Despite the particular signatures of each event and differences in their duration, intensities and antecedent conditions, this study highlights and contrasts the dramatic effects that hurricanes and droughts can have on tropical streams. If extreme climatic events continue increasing in frequency and severity due to climate change, long-term data such as ours could prove essential for understanding ecosystem responses and potential management alternatives in the face of continued change.