Stable isotopic analysis of fossil chironomids as an approach to environmental reconstruction: state of development and future challenges

Abstract

. 2012. Stable isotopic analysis of fossil chironomids as an approach to environmental reconstruction: state of development and future challenges. Fauna norvegica 31: 7-18.Remains of chironomid larvae, especially their strongly sclerotized head capsules, can be found abundantly and well preserved in most lake sediment records. These remains mainly consist of chitin and proteins and, since their chemical composition does not seem to be strongly affected by decompositional processes, they can be used to develop palaeoenvironmental reconstructions based on their stable isotopic composition. Here we review available stable isotope studies based on fossil chironomids and indicate future research necessary to further develop this still relatively new research approach. Efforts to produce stable isotope records based on fossil chironomids have mainly examined the elements H, N, C, and O. They have focussed on (1) developing the methodology for preparing samples for isotopic analysis, (2) laboratory studies cultivating chironomid larvae under controlled conditions to determine the factors affecting their stable isotopic composition, (3) ecosystem-scale studies relating stable isotopic measurements of fossil chironomid assemblages to environmental conditions, and (4) developing first down-core records describing past changes in the stable isotopic composition of chironomid assemblages. These studies have shown that chemical sample pretreatment may affect the isotopic composition for some elements. Laboratory runs suggest that the diet of the larvae influences their stable isotopic composition for H, N, C and O, whereas stable isotopes in the ambient water also strongly influence their oxygen and to a lesser extent hydrogen isotopic composition. These experiments also indicate only minor offsets between the nitrogen and carbon isotopic composition of chironomid soft tissue and the fossilizing head capsules, whereas for hydrogen and oxygen this offset remains to be explored. Though few datasets have been published, the available ecosystem studies and developed down-core sediment records indicate that stable isotopes in chironomid remains have the potential to provide reconstructions of past climatic change (H, O) and insights into past food web structure, methane production and pollution of lake ecosystems (N, C). Future efforts will be necessary to develop these approaches including more detailed analyses of the effects of sample pretreatment on stable isotope measurements on chitinous fossils, more extensive laboratory studies constraining the effects of external factors (e.g., isotopic composition of food and ambient water, temperature) on stable isotopes in chironomid larvae, and surveys exploring seasonal changes in the isotopic composition of chironomid larvae and assessing how this seasonality influences fossil assemblages. Finally, multi-site field studies relating chironomid δD, δ 15 N, δ 13 C and δ 18 O to parameters such as δ 18 O of precipitation, air and water temperatures, and nutrient and greenhouse gas conc...

The stable isotopic composition of <i>Daphnia</i> ephippia reflects changes in δ<sup>13</sup>C and δ<sup>18</sup>O values of food and water

“…Approaches are continuing to be developed that apply stable isotope ratio analysis to chitinous remains of aquatic invertebrates preserved in lake sediments (Heiri et al, 2012;Leng and Henderson, 2013). For example, the δ 13 C values of the fossil head capsules of benthic larvae of non-biting midges (Chironomidae) and δ 13 C values of the remains of water fleas of the genus Daphnia (Cladocera) have been used to investigate past changes in carbon cycling and energy pathways in lake food webs (Perga, 2011;Wooller et al, 2012;van Hardenbroek et al, 2013;Belle et al, 2014;Frossard et al, 2014).…”

“…The chitinous ephippia are found abundantly in a wide range of lake sediment types and remain well preserved in sediments hundreds to thousands of years old (Szeroczyńska and Samarja-Korjonen, 2007). Since the chemical composition of chitinous invertebrate remains stays largely unchanged even in fossils more than 10 000 years old (Miller et al, 1993;Verbruggen et al, 2010a), they are believed to retain their isotopic composition after deposition (Heiri et al, 2012). Therefore, ephippia may provide material for reconstructing the past stable isotopic composition of Daphnia in lakes and, consequently, for investigating past conditions in aquatic food webs (e.g., Wooller et al, 2012;van Hardenbroek et al, 2013van Hardenbroek et al, , 2014Schilder et al, 2015).…”

“…There is a need for more controlled laboratory studies investigating 13 C and 15 N (Martínez del Rio et al, 2009) as well as the relationships between the δ 18 O values of organisms and those of environmental water (Rubenstein and Hobson, 2004). 13 C, which is generally assumed to be between 0 and +1 ‰ for a range of animals, including invertebrates (DeNiro and Epstein, 1978;McCutchan et al, 2003), has been studied for chironomids under controlled laboratory conditions (Goedkoop et al, 2006;Wang et al, 2009;Heiri et al, 2012;Frossard et al, 2013) and ranges from −0.8 to +1.2 ‰. For Daphnia magna, 13 C values range from +1.7 to +3.1 ‰ (Power et al, 2003).…”

“…For Daphnia magna, 13 C values range from +1.7 to +3.1 ‰ (Power et al, 2003). 15 N, which is usually assumed to be between +3 and +4 ‰ (DeNiro and Epstein, 1981;Minagawa and Wada, 1984) ranges from −1.5 to +3.4 ‰ for chironomids (Goedkoop et al, 2006;Wang et al, 2009;Heiri et al, 2012) and from +1 to +6 ‰ for Daphnia (Adams and Sterner, 2000;Power et al, 2003;Matthews and Mazumder, 2008). In terms of oxygen, the δ 18 O values of lacustrine invertebrates are strongly and positively related to the δ 18 O values of local precipitation and the water in which the invertebrates live (Wang et al, 2009;Nielson and Bowen, 2010;Verbruggen et al 2011;van Hardenbroek et al, 2012;Soto et al, 2013), although laboratory studies have shown that the oxygen isotopic composition of the diet can also affect invertebrate δ 18 O values (Wang et al, 2009;Nielson and Bowen, 2010).…”

Taxon-specific δ13C analysis of chitinous invertebrate remains in sediments from Strandsjön, Sweden

“…These authors also demonstrated that head capsule d 13 C is influenced by the chironomid diet and that methanogenic carbon can influence the carbon isotopic signature of chironomid exoskeletons. Heiri et al (2012) and Frossard et al (2013) demonstrated that d 13 C values of chironomid head capsules are closely related to the carbon isotopic composition of the larval body and the food ingested by chironomid larvae.…”