Partaking of A rchaea to biogeochemical cycling in oxygen‐deficient zones of meromictic saline L ake F aro ( M essina, I taly)

Abstract

Summary We used a combination of molecular and microbiological approaches to determine the activity, abundance and diversity of archaeal populations inhabiting meromictic saline L ake F aro ( M essina, I taly). Analysis of archaeal 16 S rRNA , amoA , accA and hbd genes and transcripts revealed that sub‐ and anoxic layers of L ake F aro are primarily inhabited by the organisms related to the clusters of M arine G roup I .1a of T haumarchaeota frequently recovered from oxygen‐depleted marine ecosystems. These organisms dominated the metabolically active archaea down to the bottom of the lake, indicating their adaptation to recurrent changes in the levels of water column hypoxia. The upper microaerobic layer of L ake F aro redoxcline has the maximal rates of dark primary production much lower than those of other previously studied pelagic redoxclines, but comparable to the values of meso‐ and bathypelagic areas of M editerranean S ea. Application of bacterial inhibitors, especially azide, significantly declined the CO 2 fixation rates in the low interface and monimolimnion, whereas archaea‐specific inhibitor had effect only in upper part of the redoxcline. Based on these findings, we hypothesize that dark bicarbonate fixation in suboxic zone of L ake F aro results mainly from archaeal activity which is affected by the predicted lack in oxygen in lower layers.

Bibliographic Information