Stable isotope analyses revealed high seasonal dynamics in the food web structure of a peatbog

Abstract

Stable isotope analysis has become a powerful tool for the study of food web structures in aquatic communities. However, there has been little recognition of the spatial and temporal variabilities of isotopes in food webs in peatbogs. Here, we investigated the structure of food web in peatbog dominated by Sphagnum mosses by analyzing: (i) density and biomass of different components of food webs; (ii) the digestive vacuole contents of Hyalosphenia papilio—the most abundant species of amoebae occurring in peatbog; (iii) the seasonal changes in the carbon and nitrogen stable isotope signatures of particular components of food web. The study was performed in the Moszne peatbog located in the western part of Polesie Lubelskie (eastern Poland). Fieldwork was done on a monthly basis from April to November 2013. The largest total biomass of microorganisms in all of the seasons was noted in testate amoebae. Algae and cyanobacteria were the second largest group of microorganisms. The feeding behaviour of H. papilio varied throughout season. Among the identified prey, the highest frequency was noted in algae, cyanobacteria and ciliates. In spring and summer, prey was dominated by phycoflora, while during the autumn period the main prey consisted of cyanobacteria and ciliates. The results of the study indicate significant seasonal variation in the level of stable isotopes in individual components (bacteria, fungi, protozoa and metazoa) of the food web of peatbog, and thus also considerable dynamics of changes between trophic levels.

Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands

“…Hence, higher mixotroph densities can either increase C uptake or C release in peatlands, depending on the relative contribution of phototrophy and heterotrophy in their feeding behaviour. As supported by stable isotope analyses (Jassey et al, 2013b;Mieczan et al, 2015a), mixotrophic testate amoebae mainly acquire their total C through photosynthesis. Consequently, a decrease of the dominance of mixotrophic testate amoebae means that less C is stored by the system and more space is available for strict bacterivores and/or fungivores in the community, as observed in Clara bog with the high abundances of Phryganella sps.…”

Effects of Sphagnum Leachate on Competitive Sphagnum Microbiome Depend on Species and Time

“…This is especially the case in ombrotrophic peatlands, where cryptogams such as Sphagnum mosses can dominate the ecosystem (Yu et al, 2011). Sphagnum mosses form expansive carpets that provide a habitat for a large diversity of microbial communities (Gilbert et al, 1998; Jassey et al, 2013, 2015; Bragina et al, 2014; Mieczan et al, 2015a, b). The Sphagnum microbiome is structured in a microbial food web constituted by bacteria, fungi (decomposers), protists (producers, predators, top-predators), and small-sized metazoan (predators, top-predators).…”

Greening of the boreal peatland food web: Periphyton supports secondary production in northern peatlands

“…Specifically, we found that periphyton contributed more to invertebrate diet over the growing season (71-76% in rich, 78-81% in moderate, and 20-65% in poor) compared to all other possible sources of carbon combined (e.g., bryophytes, vascular plants, or detritus), which contribute less than 17% in the poor fen and less than 9% in moderate and rich fens. These findings add to a growing body of literature challenging the notion that primary production by algae is of minor importance to peatland energy flow (van Duinen et al 2013;Mieczan et al 2015;Vesterinen et al 2016;DeColibus et al 2017). It is also noteworthy that some herbivores had lower δ 13 C than periphyton, which could reflect the inclusion of highly 13 C-depleted heterotrophic bacteria (e.g., methane-oxidizing bacteria) as another source of dietary carbon (van Duinen et al 2013).…”

“…The presence of planktonic consumers in a peatland food web is noteworthy given that zooplankton are traditionally studied in limnetic food webs whereas the aquatic phase of boreal peatlands has largely been ignored. The dynamic environmental conditions that characterize the aquatic phase of boreal peatlands favor animal populations with short life histories, such as zooplankton, that can take advantage of high-quality food sources available during the short summer growing season (Rautio et al 2011;Mariash et al 2014;Mieczan et al 2015). The shallow nature of peatland pools with a well-lit photic zone and an abundance of submerged substrata (e.g., erect plant stems) facilitates periphyton development throughout the entire water column, enabling access for both benthic and planktonic consumers.…”