PDF《northern Germany)》

2008 microbial breakdown of humic substances. In addition to a degradative role, peroxidases are also involved in the polymerisation of aromatic compounds, e.g. humic substances (Saccomandi et al. 1998, Piccolo et al. 2000, Cozzolino &

Piccolo 2002), phenols and anilines (Dec &

Bollag 1994, Colosi et al. 2007). The objective of the present study was to determine whether extracellular peroxidases occur in Lake Gro?e Fuchskuhle (northern Germany), and if so, whether they are involved in degradation of humic substances. Lake Gro?e Fuchskuhle was subdivided in

1989 into

4 compartments, which resulted in a divergence of phys- ical and chemical parameters (Koschel 1995, Sachse et al. 2001, Burkert et al. 2004), microbial activities (Bittl &

Babenzien 1996, Casper et al. 2003, Burkert et al. 2003), abundance and structure of phytoplankton com- munities (Hehmann &

Krienitz 1996, Hehmann et al. 2001), and structure of the microbial food web (2imek et al. 1998). These characteristics are also reflected in differences in the composition and concentration of dissolved organic carbon (DOC), with considerable divergence in concentrations of humic substances (Bittl 1999, Sachse et al. 2001). Due to the high concen- tration of humic substances, and due to the divergence in DOC quality, we proposed at the outset that extra- cellular peroxidase activity would differ between the compartments of Lake Gro?e Fuchskuhle. ........