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Quantifying the response of stream ecosystems to a punctuated cold-stress disturbance across a semi-arid to sub-humid gradient

Stream Cold Semi-arid Sub-humid


Titre : RAPID : Quantifying the response of stream ecosystems to a punctuated cold-stress disturbance across a semi-arid to sub-humid gradient

Organismes NSF : DEB Division Of Environmental Biology

Durée : May 15, 2021 — April 30, 2022 (Estimated)

Climate change is expected to result in increased global mean temperatures that will lead to movement of tropical and sub-tropical species toward the poles, a process known as “Changes in precipitation patterns are predicted to be spatially variable, with some regions becoming drier and others wetter. The ecology and health of stream ecosystems are particularly susceptible to changes in rainfall and temperature. Simultaneously, the frequency and intensity of extreme weather events are expected to increase, and it is unknown how these extreme events will interact with gradual changes in temperature and precipitation to affect stream ecosystems. This research evaluates how a recent extreme event, the February 2021 “polar vortex” in Texas, interacts with changing mean climate conditions to predict how climate change will impact the structure and function of U.S. stream ecosystems in the coming decades. The research leverages a steep, natural rainfall gradient that features an abrupt shift in stream community composition and ecosystem functioning between semi-arid and mesic ecosystems. Repeated field measurements are being made for one year after the polar vortex and these data compared to prior data collected from these streams over the last 4 years. This work greatly increases our understanding of how climate change will affect sub-tropical stream ecosystems and their biota. Training of undergraduates (including minority) and graduate students along with community outreach via an established K–12 program contribute to the project’s broader impacts for society.

The goals of this research are to characterize the direct and indirect impacts of an extreme cold event (ECE) on stream ecosystem structure and function and to examine the role of organism traits and local environmental features that drive these effects. Punctuated low temperatures below an organism’s thermal limits can result in physiological, behavioral, and fitness consequences. These events are particularly important in the context of understanding tropicalization. Warm-adapted species are expanding poleward but lack adaptations for cold conditions, and thus may be more vulnerable to ECEs, driving mass mortality events. The impact of mass mortality events on ecosystem functioning may last for months to years and result in population declines, changes to community composition, and the contribution of dead individuals to the organic matter pool. The following hypotheses are being tested : 1) mesic streams will have greater thermal buffering capacity than semi-arid sites due to their greater discharge per unit watershed and greater tree canopy that creates a microclimate above the water surface ; 2) taxa in semi-arid streams will have greater cold tolerance because many of them have adaptations to cope with harsh conditions ; 3) taxa with neotropical ancestry will have lower cold tolerance due to a lack of adaptions for cold stress ; 4) fish and invertebrate mortality will indirectly affect the abundance of algae and benthic organic matter, impacting stream metabolism. Because ECEs may become more common in the future, studying this historically rare event may help us understand how ECEs may interact with “tropicalization”. Furthermore, the utilization of a steep rainfall gradient provides an exceptional opportunity to study the interaction between extreme disturbance and long-term climate conditions.

Partenaire (s) : James Hogan (Principal Investigator)

Bureau de recherche parrainé  : Texas A&M University Corpus Christi 6300 Ocean Dr. Corpus Christi

Financement : 141 389,00 ¤

National Science Foundation

Page publiée le 26 novembre 2021