Open AccessCommunity composition of lacustrine small eukaryotes in hyper‐eutrophic conditions in relation to top‐down and bottom‐up factors
Author(s) -
Lepère Cécile,
Domaizon Isabelle,
Debroas Didier
Publication year - 2007
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.2007.00359.x
Subject(s) - biology , mesocosm , terminal restriction fragment length polymorphism , nutrient , eutrophication , trophic level , ecology , chlorophyta , community structure , algae , restriction fragment length polymorphism , genetics , polymerase chain reaction , gene
Small eukaryotes (0.2–5 μm) in hyper‐eutrophic conditions were described using terminal restriction fragment length polymorphism and cloning–sequencing, and were related to environmental variables both by an experimental approach and by a temporal field study. In situ analysis showed marked temporal variations in the dominant terminal restriction fragments (T‐RFs), which were related to environmental variables such as nutrient concentrations and metazooplankton composition. To monitor the responses of the small‐eukaryote community to top‐down (absence or presence of planktivorous fish) and bottom‐up (low or high nitrogen and phosphorus addition) effects, a cross‐classified design mesocosm experiment was used. Depending on the type of treatment, we recorded changes in the diversity of T‐RFs, as well as modifications in phylogenetic composition. Centroheliozoa and Cryptophyta were found in all types of treatment, whereas Chlorophyta were specific to enclosures receiving high nutrient loadings, and were associated either with LKM11 and ‘environmental sequences’. Cercozoa and Fungi were not detected in enclosures receiving high nutrient loadings and fishes. Our results showed that resources and top‐down factors are both clearly involved in shaping the structure of small eukaryotes, not only autotrophs but also heterotrophs, via complex interactions and trophic cascades within a microbial loop, notably in response to nutrient loading.