Application of dual stable isotopes in investigating the utilization of two wild dominant filamentous algae as food sources for Daphnia magna

Hong Fu,Jun Xu,Enrong Xiao,Feng He,Peng Xu,Qiaohong Zhou,Zhenbin Wu

doi:10.1080/02705060.2017.1298537

Abstract

ABSTRACTIn this study, we evaluated the effects of two dominant microfilamentous algae (i.e. Melosira granulata and Oscillatoria sp.), collected from the West Lake, on growth and metabolism of Daphnia magna. Our experiment utilized 13C and 15N dual labeling to calculate the carbon and nitrogen isotopic turnover rates and half-life times in D. magna. The two labeled types of filaments were offered to D. magna as sole food sources or as paired mixtures with the unlabeled Scenedesmus obliquus. Labeled S. obliquus served as the control. Combined results showed that D. magna had a higher grazing rate on Oscillatoria sp. than on M. granulate and a small percentage of unlabeled S. obliquus addition could improve the grazing rate in both filamentous algae, especially for Oscillatoria sp., which had the highest carbon and nitrogen isotopic turnover rates and the lowest half times, even superior to the sole S. obliquus treatment. Our study revealed that D. magna could utilize the two dominant filamentous algae as a food source for their growth and metabolism, and a small percentage addition of S. obliquus could ameliorate the negative impact of these two filamentous algae on D. magna.

Highlights

Cladocerans, especially Daphnia, form a key link in energy and nutrient mobilization between primary producers and higher trophic levels in most aquatic ecosystems (Gliwicz & Lamper 1990; Sterner & Hessen 1994; Jansson et al 2007; Lampert 2011; Sanni et al 2013; Bednarska et al 2014). Burns et al (1989) provided evidence that Daphnia carinata was able to collect trichomes of Anabaena minutissima var. attenuate with average length 77–180 mm
D. magna that were fed with Oscillatoria sp. (O1 and O2) had much lower survival rates (50% § 7.6% and 66.7% § 6.1%, p < 0.01)
This research demonstrated that D. magna does have a certain feeding rate on filamentous algae such as M. granulata and Oscillatoria sp., supporting the view that daphnids can grow and reproduce on a diet dominated by filamentous cyanobacteria (Repka 1998)

Summary

Introduction

Cladocerans, especially Daphnia, form a key link in energy and nutrient mobilization between primary producers and higher trophic levels in most aquatic ecosystems (Gliwicz & Lamper 1990; Sterner & Hessen 1994; Jansson et al 2007; Lampert 2011; Sanni et al 2013; Bednarska et al 2014). Burns et al (1989) provided evidence that Daphnia carinata was able to collect trichomes of Anabaena minutissima var. attenuate with average length 77–180 mm. Cladocerans, especially Daphnia, form a key link in energy and nutrient mobilization between primary producers and higher trophic levels in most aquatic ecosystems (Gliwicz & Lamper 1990; Sterner & Hessen 1994; Jansson et al 2007; Lampert 2011; Sanni et al 2013; Bednarska et al 2014). Burns et al (1989) provided evidence that Daphnia carinata was able to collect trichomes of Anabaena minutissima var. Meijer (2000) summarized the results of 18 case studies in the Netherlands and found that Daphnia was able to limit phytoplankton biomass in spring but not in summer. Because of the significant role of cladocerans in the aquatic food webs, studies on cladoceran–filament interaction could provide important information for a better understanding of

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