Drought altered trophic dynamics of an important natural saline lake: A stable isotope approach

Could an event of extreme drought (2019-2020) affect the feeding ecology of Bubo magellanicus (Gmelin 1788) (Strigiformes: Strigidae) in a Mediterranean region of Chile?

“…But our study was performed in the central of Chile, a region considered as one of the 25 diversity hotspots on Earth ( Myers et al, 2000 ) sustaining over 50% of Chile’s vertebrate species, 50% of Chilean endemic species, and 50% of the endangered species ( Simonetti, 1999 ). Therefore, the low presence of small mammals in the study area due to isolation was discarded as a possibility, and instead could be suggested to be related to a climatic scenario of extreme drought that has developed more than a decade in the Mediterranean region of Chile ( Garreaud et al., 2020 ), affecting the hydroclimate and vegetation plus causing complex changes in composition and productivity ( Garreaud et al, 2017 ), that generates trophic cascades’ modifications due down-top control ( Elmhagen & Rushton, 2007 ; Lesser et al, 2020 ) that in turn transforms the structure and composition of the community, promoting long-term persistence of rare species by stressing dominant species throughout the food web ( Prugh et al, 2018 ; De Necker et al., 2022 ). The trophic ecology of owls is also affected by the alteration of energy transfer flux through the different links that end up affecting the strong trophic interactions present in the food web ( McCann, Hastings & Huxel, 1998 ; Prugh et al, 2018 ).…”

“…According to the predictions of global climate change, there will be an increase in frequency, severity and duration of this natural hazards ( Dai, 2013 ; Satoh et al, 2022 ), with more serious damages for anthropogenic activities and severe alteration in the environment (Wilhite & Buchanan-Smith 2005), with the latter probably being more important than the socioeconomic impacts ( van Dijk et al, 2013 ; Felbermayr et al., 2022 ). However, determining the impact of a drought in environmental and ecological terms is complex, as affected species can be influenced by multiple ecological pathways including their interactions, such as competition, growth or survival rates ( Chesson & Huntly, 1997 ); and alterations or absences of trophic levels of food webs ( Prugh et al, 2018 ; De Necker et al., 2022 ). Other studies have shown that droughts strongly alter the dynamics of animal populations ( Cruz-McDonnell & Wolf, 2016 ; Lister & García, 2018 ), affecting the survival and reproductive success of a wide variety of organisms, including mammals ( Bourne et al, 2020a ), reptiles ( Sperry & Weatherhead, 2008 ; Martín et al., 2022 ) and birds ( Bourne et al, 2020b ), with important consequences in the community structure ( Ledger et al, 2013 ) and severe effects on top predators due to the shift and removal of hug species ( Prugh et al, 2018 ), with alterations in their diet and trophic niche ( Henschel & Skinner, 1990 ; Van Horne, Schooley & Sharpe, 1998 ; McDowell & Medlin, 2009 ).…”

A stable isotope analysis of the dietary patterns of the aquatic apex predator, the African tigerfish (Hydrocynus vittatus)

“…Quality control was done by analyzing replicate measurements of laboratory standard (L-alanine; SI Science Co., Ltd.). Standards were run for every seven samples with measurement precision of ±0.02‰ for both C and N stable isotope ratios (de Necker et al, 2020(de Necker et al, , 2022.…”

“…To ascertain the potential food sources and their contributions to the diet of small and large H. vittatus the sources were pooled into biologically meaningful groups and the different analyses follow those of de Necker et al (2020Necker et al ( , 2022. The pooling of multiple sources improves the discriminatory power of Bayesian mixing models and is a recommended method for the improved discrimination between sources and in providing a better constrained solution to such models (Manfrin et al, 2018;Phillips et al, 2005Phillips et al, , 2014Stock et al, 2018).…”

“…The determination of ontogenetic dietary shifts in fishes using SIA is increasing, and the use of δ 15 N as an indicator of trophic position and size-related dietary shifts is commonplace (Davis et al, 2012;Galván et al, 2010;Herlevi et al, 2018). Most dietary shifts in fishes have been demonstrated from simple food webs where pronounced isotopic shifts were anticipated (Jensen et al, 2012;Post, 2002Post, , 2003, such as lentic systems (de Necker et al, 2020(de Necker et al, , 2022Thompson et al, 2012). However, river food webs have a more complex trophic structure with a more diverse array of production sources.…”