Tyler James Butts , Robert A Johnson, Michael Weber, Grace Marie Wilkinson 

The frequency and intensity of ecosystem disturbances is increasing due to climate change. However, the structure of trophic interactions within food webs may mediate the resistance and resilience of ecosystems to disturbance events. In aquatic ecosystems, high connectivity between benthic and pelagic food chains (i.e., benthic-pelagic coupling) is theorized to generate more pathways for nutrients and energy to flow as well as strengthen top-down control. As such, we predicted that greater benthic-pelagic coupling would increase the resistance (longer response time) and resilience (shorter recovery time) of aquatic primary production to pulse disturbances and reduce the chance of a critical transition. To test this prediction, we simulated two storm-induced pulse disturbances by adding N and P (~3% and ~5% increase in ambient concentrations) to three experimental ponds with food webs containing low, intermediate, and high benthic-pelagic coupling. Another set of ponds with matching food web structures served as reference ecosystems. We evaluated the primary production response time (resistance) and recovery time (resilience) following each nutrient pulse using a response detection algorithm and quantified the occurrence of a critical transition in algal biomass. The high coupling pond never exceeded the response threshold. Following our prediction, chlorophyll-a concentrations exceeded the response threshold after 18 and 24 days in the intermediate and low coupling ponds, respectively. There was also evidence of a critical transition in the low coupling pond following the first pulse. After the second nutrient pulse, chlorophyll-a exceeded the response threshold again in both low and intermediate ponds, but the response was much faster in the low coupling pond (8 days) compared to the intermediate coupling pond (20 days), though again there was no response in the high coupling pond. Recovery time increased substantially after the second pulse in the low coupling pond increasing from 8 to 22 days and did not occur following the second pulse in the intermediate pond. Together, these results support our prediction that greater benthic-pelagic coupling confers greater resistance and resilience to repeated pulses of nutrient loading, demonstrating that food web structure can mediate ecosystem responses to disturbance.