225plotted against the arithmetic average length (l) (Carrias
et al. 2002 ). The parameters k and β are estimated by regres-
sion after logarithmic transformation. Such analyses of the
TEP size spectra revealed that the particles followed a non-
steady- state distribution during the spring period. The β val-
ues were always lower than 4 and close to the values reported
by Mari and Kiørboe ( 1996 ) in marine waters.
13.4 Bacterial Within TEP
Double-staining procedure with DAPI and Alcian Blue (Fig.
13.1 ) indicates that > 97 % of TEP contained attached bacte-
ria. The number of attached bacteria per particle increased
with the size of the particle. However, expressed per unit
area of particle, the density decreased with the size of the
particle (Table 13.1 ). The bacterial density within TEP can
be expressed by the power law n = a d b (Mari and Kiørboe
1996 ) where n is the number of attached bacteria per particle,
d is the equivalent spherical diameter of the particle, and a
and b are constants for a given sample. These constants were
obtained from log-log plots of n versus d. The density of
TEP-associated bacteria, expressed by the constant a (the
slope of the regression lines between the number of bacteria
per particle and the equivalent spherical diameter of the
particles), was slightly higher in Lake Pavin than in the
eutrophic Lake Aydat (Carrias et al. 2002 ) suggesting that
TEP are more suitable substrates for bacteria in the oligome-
sotrophic environment. We also found that the constant a
tends to decrease with depth in relation with decreasing tem-
perature values (Arnous et al. 2010 ). TEP-associated bacte-
ria represented 0.3–8.9 % of total DAPI-stained bacteria
corresponding to about 10^7 –10^8 bacteria L −1 associated with
polysacharidic particles.Fig. 13.2 Vertical
distribution of the abundance
of TEP in April 3 ( white
histogram ) and May 4 ( Grey
histogram ) during spring
2005 in Lake Pavin
13 The Signifi cance of Transparent Exopolymeric Particles (TEP) for Microorganisms in Lake Pavin