approximately one gram of superficial lake sediment, and recorded 20 active
ciliate species at the time of sampling. In response to experimental treatments
(e.g. addition of a variety of microbial food sources, establishment of redox
gradients, and changes in light and temperature regimes) over a period of
three months, the species total rose to 137, at which time it was still increasing
(Fig. 9.5).
More specific evidence that the ‘habitat selects’ is provided by the discovery of
typical marine ciliate morphospecies living in inland evaporation salt pans in
Central Spain at 300km from the nearest coastal marine environment
(Esteban & Finlay, 2004 ). These salt pans are fed from saline underground
water originating in Triassic marine sediments. Water flows to the surface and
into permanent evaporation pools, where the salt concentration varies from
brackish to characteristic seawater, and up to hypersaline. Conversely, when
samples from a hypersaline coastal lagoon in Southern Spain were progressively
diluted with freshwater, a large number of typically freshwater proto-
zoan species appeared (Esteban & Finlay,2003). It is surprising that simple
Figure 9.5The ubiquitous ‘seedbank’. A small sample of sediment from a freshwater lake
was ‘manipulated’ (see text and Finlayet al., 1996a; Fenchelet al., 1997) to produce a wide
variety of niches for ciliate species – e.g. a range of microbial food sources, redox
gradients, changes in light and temperature. About 20 ‘trophic’ species were identified at
the beginning of the experiment, and this number increased to more than 130 species
over a period of three months.
BODY SIZE AND BIOGEOGRAPHY 173