Photoautotrophic microorganisms as a carbon source for temperate soil invertebrates

Abstract

We tested experimentally if photoautotrophic microorganisms are a carbon source for invertebrates in temperate soils. We exposed forest or arable soils to a 13 CO 2 -enriched atmosphere and quantified 13C assimilation by three common animal groups: earthworms (Oligochaeta), springtails (Hexapoda) and slugs (Gastropoda). Endogeic earthworms (Allolobophora chlorotica) and hemiedaphic springtails (Ceratophysella denticulata) were highly 13 C enriched when incubated under light, deriving up to 3.0 and 17.0%, respectively, of their body carbon from the microbial source in 7 days. Earthworms assimilated more 13 C in undisturbed soil than when the microbial material was mixed into the soil, presumably reflecting selective surface grazing. By contrast, neither adult nor newly hatched terrestrial slugs (Deroceras reticulatum) grazed on algal mats. Non-photosynthetic 13 CO 2 fixation in the dark was negligible. We conclude from these preliminary laboratory experiments that, in addition to litter and root-derived carbon from vascular plants, photoautotrophic soil surface microorganisms (cyanobacteria, algae) may be an ecologically important carbon input route for temperate soil animals that are traditionally assigned to the decomposer channel in soil food web models and carbon cycling studies.

Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition

“…), may feed on non‐vascular plants, i.e. algae and lichens, suggesting that the importance of non‐vascular plants as a basal resource of soil food webs has been underestimated (Schmidt et al ., ; Potapov et al ., ; Potapov et al ., ). Supporting the importance of non‐vascular plants in soil food webs, a recent DNA‐based study showed that algivory is widespread among soil protists (Seppey et al ., ).…”

“…However, recent laboratory studies did not find Δ 15 N values to vary with food quality (Heethoff & Scheu, ). Another explanation might be the assimilation of resources depleted in 15 N. For instance, algae and lichens incorporate 15 N‐depleted atmospheric N deposits (Tozer et al ., ) and may channel this nitrogen to animal consumers in the soil (Schmidt, Dyckmans & Schrader, ; Potapov, Korotkevich & Tiunov, ).…”

Conversion of rainforest to oil palm and rubber plantations alters energy channels in soil food webs

“…Figure prepared using the R package bipartite feed on algae, with on average algal biomarker FAs comprising 6% of total NLFAs in Collembola and 4% in Oribatida. Photoautotrophic algae and bacteria may represent a considerable portion of the diet of Collembola in various habitats (Potapov, Korotkevich, & Tiunov, 2018;Schmidt, Dyckmans, & Schrader, 2016). A high palatability of algae for Collembola and Oribatida was demonstrated in laboratory experiments (Brückner, Schuster, Smit, & Heethof, 2018;Buse, Ruess, & Filser, 2013Scheu & Folger, 2004) and field stable isotope-based studies from temperate forest ecosystems suggested that algae serve as food resource for certain species of Collembola and Oribatida (Schneider et al, 2004;Maraun et al, 2011;Potapov, Semenina, Korotkevich, Kuznetsova, & Tiunov, 2016).…”

“…However, Ngosong, Raupp, Scheu, and Ruess (2009) F I G U R E 4 Channeling of energy from basal resources into consumers in rainforest, rubber and oil palm plantations as indicated by fatty acid analysis. Photoautotrophic algae and bacteria may represent a considerable portion of the diet of Collembola in various habitats (Potapov, Korotkevich, & Tiunov, 2018;Schmidt, Dyckmans, & Schrader, 2016). The width of boxes/pictures of basal resources reflects the relative importance of these resources across land-use systems; note that it ignores potential differences in production and assimilation rate of different NLFAs among producer and consumer groups.…”

Suitability of Contact-Free Oxygen Optical Microsensors for Measuring Respiration and Photosynthesis in Green Algae

“…The increased interest in the role of green algae in terrestrial ecology (Buse et al, 2013;Schmidt et al, 2016) and ecotoxicology has emphasized the need for simple and objective methods of measuring their growth. Counting algae cells is the most popular method to estimate algae growth (Nyholm, 1990;Nyholm and Damgaard, 1990;Grote et al, 2005;Matzke et al, 2008), using either a counting chamber under the microscope or an automatic cell counter.…”