Drought may alter the flux of essential omega-3 fatty acids from streams to terrestrial ecosystems

Résumé fourni par la source

Stream and riparian food webs are connected via cross-ecosystem subsidies, including essential nutrients like omega-3 fatty acids that originate in the aquatic environment (microalgae) but support terrestrial consumers. Although global change stressors could be disrupting these linkages, most research to date has focused on subsidy quantity rather than quality. Here, we reviewed the literature on omega-3 long-chain polyunsaturated fatty acids (ω3 LC-PUFA) in streams (and other freshwaters), and we examined how drought-related stress may influence their production, accumulation, and trophic transfer from streams. Although direct evidence linking drought conditions to changes in ω3 LC-PUFA dynamics in streams is limited, existing studies indicate that warming and drying-induced shifts in basal resource composition and primary production, altered consumer community composition and emergence phenology, and reduced capacity for ω3 LC-PUFA bioconversion are poised to disrupt ω3 LC-PUFA fluxes from the aquatic to the terrestrial environment. Accumulation of ω3 LC-PUFA in organisms is mainly driven by the individual species, but can also be influenced by life-history traits, including drought adaptations (e.g., resistance and resilience strategies), temporal integration of diet, and feeding ecology. We confirmed and illustrated these mechanisms via a case study on intermittent stream invertebrates at Pinnacles National Park, California. Finally, we identified key challenges and recommendations for advancing ω3 LC-PUFA research. These include (i) explicitly considering organismal life histories; (ii) improving sampling design to strengthen inference; (iii) considering underground ecological processes; (iv) advancing research on consumer fitness responses to ω3 LC-PUFA limitation and on ‘upgrading’; (v) measuring rates and fluxes; and (vi) scaling up and forecasting fatty acid flux under increasingly dry futures by integrating models of hydrology, organismal biology, and community dynamics. We contend that the disruption of cross-ecosystem linkages, not just in resource magnitude but also in quality, is a “blind spot” of global change ecology that demands immediate attention.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.