Benthic resources are the key to Daphnia middendorffiana survival in a high arctic pond

Abstract

Summary 1. Shallow arctic lakes and ponds have simple and short food webs, but large uncertainties remain about benthic–pelagic links in these systems. We tested whether organic matter of benthic origin supports zooplankton biomass in a pond in NE Greenland, using stable isotope analysis of carbon and nitrogen in the pond itself and in a 13C‐enrichment enclosure experiment. In the latter, we manipulated the carbon isotope signature of benthic algae to enhance its isotopic discrimination from other potential food sources for zooplankton. 2. The cladoceran Daphnia middendorffiana responded to the 13C‐enrichment of benthic mats with progressively increasing δ13C values, suggesting benthic feeding. Stable isotope analysis also pointed towards a negligible contribution of terrestrial carbon to the diet of D. middendorffiana. This agreed with the apparent dominance of autochthonous dissolved organic matter in the pond revealed by analysis of coloured dissolved organic matter. 3. Daily net production by phytoplankton in the pond (18 mg C m−2 day−1) could satisfy only up to half of the calculated minimum energy requirements of D. middendorffiana (35 mg C m−2 day−1), whereas benthic primary production alone (145 mg C m−2 day−1) was more than sufficient. 4. Our findings highlight benthic primary production as a major dietary source for D. middendorffiana in this system and suggest that benthic organic matter may play a key role in sustaining pelagic secondary production in such nutrient‐limited high arctic ponds.

Biotic responses to multiple aquatic and terrestrial gradients in shallow subarctic lakes (Old Crow Flats, Yukon, Canada)

“…Shallow northern lakes tend to have food webs dominated by benthic biota, which are often responsive to changes in environmental processes (Sierszen et al 2003;Rautio and Vincent 2007;Cazzanelli et al 2012). Diatoms, a group of mainly single-celled algae with siliceous cell walls (Chromista: Bacillariophyta), and chironomids, non-biting midges with chitinous exoskeletons (Insecta: Diptera: Chironomidae), are well represented in lake sediments (Birks 1998;Douglas and Smol 1999;Brodersen and Quinlan 2006) because taxonomically diagnostic components are relatively resistant to post-depositional degradation processes (Battarbee 2000;Axford et al 2009).…”

Effects of nutrient loading, temperature regime and grazing pressure on nutrient limitation of periphyton in experimental ponds

“…However, phytoplankton and periphyton differ in their uptake of nutrients. This may result in decreased energetic (or C) growth efficiency of herbivores due to limitation of their growth by low N or P in the diet (Sterner & Elser, 2002), unless grazers take up these nutrients from the sediment or other nutrient hotspots in the water (Schatz & McCauley, 2007;Cazzanelli et al, 2012). Furthermore, periphyton and phytoplankton from the same lake may differ in the extent to which they are influenced by light and grazing (Hill, Boston & Steinman, 1992;Steinman, 1996;Elser & Urabe, 1999;Hillebrand & Kahlert, 2001;Hillebrand, 2005).…”

Influences of fish on food web structure and function in mountain lakes

“…A strong contribution of phytoplankton and terrestrial material to aggregate zooplankton samples and individual taxa is consistent with the literature (Grey et al., ; Weidel et al., ). Contribution of periphyton is more highly variable and dependent on taxa because although it is often low (Syväranta et al., ; Weidel et al., ), it can be high for some taxa in unique cases where resources are limited (Cazzanelli, Forsström, Rautio, Michelsen, & Christoffersen, ).…”