Carbon Pathways Through the Food Web of a Microbial Mat From Byers Peninsula, Antarctica

Abstract

Microbial mats are complex communities that represent a large biomass fraction in non-marine Antarctic ecosystems. They confer structure to soils and constitute, by themselves, intricate microecosystems, where a great variety of microorganisms and microfauna contributes to the ecosystem functions. Although in recent years Antarctic microbial mats have been thoroughly investigated, trophic relationships within the communities remain unresolved. We therefore conducted a study of the trophic relationships of a microbial mat from Byers Peninsula, Antarctica, using DNA analysis and stable isotopes as trophic tracers. Our results suggested, based on a Bayesian mixing model, that at least four trophic levels are present within this microecosystem: primary producers (cyanobacteria and diatoms), primary consumers (rotifers and tardigrades), secondary consumers (nematodes) and decomposers (fungi). Nematodes would play a key role as top consumers of the community, connecting the two carbon inputs described into the system, as omnivores at the secondary trophic level. In addition, carbon pathways from primary trophic level to consumers take place quickly during the first 24 h after its incorporation in the primary producers, dispersing across all the trophic levels and reaching secondary consumers in less than 11 days. This suggests that, given the changing physical conditions and presumably short periods of activity, there is a fine temporal coupling among the organisms in the community, minimizing the redundancy in function performance among trophic levels.

Stable isotopic composition of top consumers in Arctic cryoconite holes: revealing different position in supraglacial trophic network

“…Generally, the δ 13 C values of tardigrades and rotifers in our study were lower than δ 13 C values in decarbonized 270 cryoconite. This difference is similar as described by Almela et al (2019) and Velázquez et al (2017) in Antarctic microbial mats. Nevertheless, it contrasts with the fundamental literature (Peterson and Fry, 1987;Wada, 2009) as well as with the study of Shaw et al (2018) focusing on Antarctic soil microbial mats, which presented δ 13 C values of tardigrades and rotifers similar or slightly higher than δ 13 C values of their potential diet.…”

“…Considering the close δ 13 C isotopic values of consumers from Ebbabreen and Nordenskiöldbreen, the observed 305 pattern could signify an overlap in food preferences of both consumers (Almela et al, 2019;DeNiro and Epstein, 1978;Mialet et al, 2013;Ricci, 1984;Velázquez et al, 2017). The non-strict division of consumed food between https://doi.org/10.5194/bg-2020-46 Preprint.…”

“…tardigrades and rotifers was apparent in various feeding experiments (Mialet et al, 2013;Ricci, 1984;Střítecká and Devetter, 2015) even though Almela et al (2019) demonstrated that tardigrades were related to larger particles (e.g. algae) and rotifers mostly to smaller ones (e.g.…”

Limnology and Aquatic Microbial Ecology of Byers Peninsula: A Main Freshwater Biodiversity Hotspot in Maritime Antarctica

“…commune) are also abundant in nutrient-starved mats, as well as in those showing high dehydration [19,68]. Actually, recent studies performed using molecular techniques in these mats demonstrate the dominance of the family Nostocaceae, comprising nearly half of the Cyanobacterial abundance compared to Oscillatoriaceae and Chroococcaceae [69]. Coccoid chlorophytes (green algae) may also occur in the mats [68], whereas Ulothrix sp.…”

“…The estimates of the photosynthetic rates in the mats attained in some of the former studies, all based on the use of NaH 13 CO 3 as a tracer, range up to an order of magnitude from 0.74 to 4.2 mg C cm −2 h −1 , being the differences directly related to the environmental conditions for the studied communities. Bayesian mixing models built for these microbial mats [69] indicate the occurrence of four trophic levels, namely, primary producers (cyanobacteria and diatoms), primary consumers (rotifers and tardigrades), secondary consumers (nematodes) and decomposers (fungi and heterotrophic bacteria). Interestingly, this study [69] suggests that there is a great coupling among the different microbial guilds, in such way that they are minimizing functional redundancies and optimizing its development for the short growth periods.…”