Stable isotope analysis reveals relative influences of seasonal hydrologic variation and impoundment on assimilation of primary production sources by fish in the Upper Yesilırmak River, Turkey

Abstract

This study analyzed variation in stable isotope ratios of aquatic and terrestrial primary producers and two common cyprinid fishes (Capoeta banarescui and Squalius cephalus) at seven sites in the upper Yeşilırmak River Basin, Turkey, to estimate relative contributions of basal production sources to fish biomass. We hypothesized that seasonal and spatial variation in fish assimilation of basal production sources would be affected by hydrological variation, with results for a reach downstream from a reservoir differing from those from upstream sites. Carbon and nitrogen isotopic ratios of primary producers and S. cephalus and d 15 N of C. banarescui revealed significant spatial variation. d 13 C of primary producers, d 15 N of S. cephalus, and both d 13 C and d 15 N of C. banarescui revealed significant seasonal variation. C. banarescui biomass in the river channel was mostly derived from terrestrial herbaceous plants, and its biomass in the reservoir derived mostly from aquatic plants. Estimated proportional contributions of herbaceous plants to both species were greatest at the downstream site during spring, and declined during summer in the case C. banarescui. Overall, the influence of the dam was small relative to effects from watershed characteristics and seasonal changes in temperature and hydrology.

Stable Isotope Analysis Reveals the Importance of Riparian Resources as Carbon Subsidies for Fish Species in the Daning River, a Tributary of the Three Gorges Reservoir, China

“…Given that the seston in the limnetic zone comprised mainly of planktonic algae, it is reasonable to conclude that autochthonous food sources (aquatic algae) in the Daning River serve as certain unneglectable and vital supports to fish production. This finding is consolidated by studies of other reservoirs [8,16] and rivers [39][40][41] where algal carbon of either suspended or benthic origin is considered to be of much importance.…”

“…The perceptible difference in carbon pathway patterns in the Daning River relates to divergent landscape-scale hydrologic characteristics in the different reaches as described in many other riverine studies [8,13,16]. Due to the impoundment of the TGR, the lacustrine environment has been shaped in the downstream with water velocity sharply halted and water depth gradually deepening along the tributary.…”

Looking to the past to ensure the future of the world's oldest living vertebrate: Isotopic evidence for multi‐decadal shifts in trophic ecology of the Australian lungfish

“…Third, studies have shown that enhanced autotrophic production in large reservoirs can lead to considerable quantities of additional planktonic primary production and organic matter (seston) being exported downstream via releases or spilling events (Marty, Smokorowski, & Power, ; Smokorowski et al, ). Living and detrital phytoplankton and zooplankton production from impoundments may represent a carbon source to downstream food webs that was previously unavailable and typically exhibit a characteristic δ 13 C signature that is more depleted than terrestrial primary production and benthic primary production (de Junet et al, ; Solomon et al, ), and these signatures can be detected in downstream food webs (e.g., Chen & Jia, ; Kaymak et al, ; Smokorowski et al, ). Taken together, our results for the Brisbane and Burnett Rivers suggest that reduced autochthonous carbon contributions below dams, coupled with increased availability of reservoir‐derived autochthonous carbon sources released from dams, may have caused lungfish to increasingly rely upon pelagic‐dominated from benthic‐dominated food sources over time.…”

“…Living and detrital phytoplankton and zooplankton production from impoundments may represent a carbon source to downstream food webs that was previously unavailable and typically exhibit a characteristic δ 13 C signature that is more depleted than terrestrial primary production and benthic primary production (de Junet et al, 2009;Solomon et al, 2011), and these signatures can be detected in downstream food webs (e.g., Chen & Jia, 2009;Kaymak et al, 2015;Smokorowski et al, 2011). Although subtle, it is interesting to note that δ 13 C of lungfish showed some evidence of a step decrease in the mid-1990s, when values consistently fell below −20‰ and then declined further to between −24‰ and −26‰ in present-day.…”

Volume 13 Issue 10 Complete Issue

“…The research of this project has become the focus of world attention, and has provided an important theoretical reference for other countries to apply modern network technology in education (Kaymak, Winemiller, Akin, et al 2015). Mr. Mery, Pamela M took San Francisco Institute as the studied object, and carried out research on the integration of modern network technology and student service system and how to correctly apply modern network technology.…”