Trophic state changes can affect the importance of methane-derived carbon in aquatic food webs

Abstract

Methane-derived carbon, incorporated by methane-oxidizing bacteria, has been identified as a significant source of carbon in food webs of many lakes. By measuring the stable carbon isotopic composition (δC values) of particulate organic matter, Chironomidae and spp. and their resting eggs (ephippia), we show that methane-derived carbon presently plays a relevant role in the food web of hypertrophic Lake De Waay, The Netherlands. Sediment geochemistry, diatom analyses and δC measurements of chironomid and remains in the lake sediments indicate that oligotrophication and re-eutrophication of the lake during the twentieth century had a strong impact on in-lake oxygen availability. This, in turn, influenced the relevance of methane-derived carbon in the diet of aquatic invertebrates. Our results show that, contrary to expectations, methane-derived relative to photosynthetically produced organic carbon became more relevant for at least some invertebrates during periods with higher nutrient availability for algal growth, indicating a proportionally higher use of methane-derived carbon in the lake's food web during peak eutrophication phases. Contributions of methane-derived carbon to the diet of the investigated invertebrates are estimated to have ranged from 0-11% during the phase with the lowest nutrient availability to 13-20% during the peak eutrophication phase.

Glacier dynamics influenced carbon flows through lake food webs: evidence from a chironomid δ13C-based reconstruction in the Nepalese Himalayas

“…''edf'' refers to the effective degrees of freedom known that a substrate competition (for the light isotope, 12 C) can occur when the aquatic primary productivity is high and DIC concentrations are very low (Smyntek et al, 2012), leading to the decrease in the trophic fractionation. Similar observations were previously suggested from sediment records in temperate lakes (Belle et al, 2017b;Schilder et al, 2017).…”

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

“…First, the attenuation of high flows below dams can influence patterns of autochthonous primary production by modifying the exchange of organisms, nutrients, and detritus between floodplain and river (Cross et al, ; Kennedy et al, ). Second, considerable recycling of both carbon and nitrogen occur within the anoxic stratified layers of impoundments, resulting in the fractionation of stable isotopes producing depleted δ 13 C (Schilder et al, ) and enriched δ 15 N (Burford et al, ) values. Recent measurements from impoundments within the study region demonstrate they produce considerable quantities of methane and NH 4 + , from the anoxic sediments and hypolimnion (Musenze, Werner, Grinham, Udy, & Yuan, ), confirming the potential for carbon depletion and nitrogen enrichment processes to influence stable isotope values of food webs in these systems.…”

“…First, the attenuation of high flows below dams can influence patterns of autochthonous primary production by modifying the exchange of organisms, nutrients, and detritus between floodplain and river (Cross et al, 2011;Kennedy et al, 2016). Second, considerable recycling of both carbon and nitrogen occur within the anoxic stratified layers of impoundments, resulting in the fractionation of stable isotopes producing depleted δ 13 C (Schilder et al, 2017) (Musenze, Werner, Grinham, Udy, & Yuan, 2014), confirming the potential for carbon depletion and nitrogen enrichment processes to influence stable isotope values of food webs in these systems. 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, 2009;Smokorowski et al, 2011).…”

Abrupt rise in the contribution of CH4‐derived carbon to benthic secondary production of a shallow hemiboreal/boreal lake

“…In modern times, human activities (agricultural practices, sewage water, etc.) have been one of the main drivers of temporal changes in carbon sources sustaining aquatic consumers (Frossard et al ., ; Belle et al ., ; Rinta et al ., ; Schilder et al ., ). The mechanisms by which human activities impact lake carbon cycling often consist of changes in availability of nutrients for aquatic primary production (i.e.…”