Lake Pavin History, geology, biogeochemistry, and sedimentology of a deep meromictic maar lake

© Springer International Publishing Switzerland 2016 223
T. Sime-Ngando et al. (eds.), Lake Pavin, DOI 10.1007/978-3-319-39961-4_13

The Significance of Transparent

Exopolymeric Particles (TEP)

for Microorganisms in Lake Pavin

Jean-François Carrias , Christian Amblard ,

and Télesphore Sime-Ngando

Abstract

Transparent exopolymeric particles (TEP) consist of a matrix of colloidal fi brils and are

produced from dissolved carbohydrate polymers exuded by phytoplankton and bacteria.

These particles are involved in the formation of lake snow aggregates and are colonized by

diverse microorganisms. Abundance, distribution, size spectra and bacterial colonization of

TEP in Lake Pavin were studied and compared with data from other freshwater and marine

systems. Abundance of TEP ranged from 10^5 to 10^6 particles L −1 and the majority of these

particles contained attached bacteria. Bacterial density within TEP was related to tempera-

ture and decreased with particle size. TEP-associated bacteria were more important in the

oligomesotrophic Lake Pavin than in the near-by eutrophic Lake Aydat, indicating that TEP

are particularly important in environments with low nutrient loading. The community com-

position of particle-associated bacteria was different from that of free-living bacteria. In

addition, we found that bacteria associated with TEP exhibit higher enzymatic activities

than free-living cells in the surrounding water. Finally, the densities of heterotrophic nano-

fl agellates in Lake Pavin were more signifi cantly related to the densities of TEP than to the

densities of bacteria and the bacterial density within TEP. Based on comparisons with other

freshwater and marine systems, we conclude that TEP are involved in the phytoplankton –

primarily diatom – sedimentation processes and in the dynamics of bacteria and protozoa in

the pelagic zone of aquatic ecosystems.

Keywords

Transparent exopolymeric particles • Bacterial colonization • Bacteria • Heterotrophic

nanofl agellates • Freshwater • Lake Pavin

13.1 Introduction

Transparent exopolymeric particles (TEP) are colloidal
fi brils produced from dissolved carbohydrate polymers
secreted by phytoplankton and bacteria (Passow and
Alldredge 1994 ; Passow 2000 ) and are easily detected by
microscopy using an acidic solution of Alcian Blue. These
particles are able to attach to each other and to other particles

including bacteria, phytoplankton and detritus and then they

promote the formation of large organic aggregates or lake

snow (Simon et al. 2002 ). High TEP concentrations in lakes

are generally associated with phytoplankton bloom indicat-

ing that most of these particles derived from dissolved

organic carbon released by phytoplankton. TEP-associated

bacteria (Fig. 13.1 ) generally comprised 1–20 % of the total

bacteria. Attached bacteria can account for a large proportion

of the bacterial production in lakes. TEP are considered as

hotspot microenvironments, and the activity of attached bac-

teria may stimulate the growth rates of the free-living micro-

organisms in the vicinity of the particle (Simon et al. 2002 ).

In addition, protozoa and metazooplankton can consume

J.-F. Carrias (*) • C. Amblard • T. Sime-Ngando
LMGE, Laboratoire Microorganismes: Génome et Environnement ,
UMR CNRS 6023 , Université Clermont-Auvergne, Université
Blaise Pascal, BP 80026 , 63171 Aubière Cedex , France
e-mail: [email protected]

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