title: Effects of agricultural practices on organic matter degradation in ditches.
abstract: Agricultural practices can result in differences in organic matter (OM) and agricultural chemical inputs in adjacent ditches, but its indirect effects on OM composition and its inherent consequences for ecosystem functioning remain uncertain. This study determined the effect of agricultural practices (dairy farm grasslands and hyacinth bulb fields) on OM degradation by microorganisms and invertebrates with a consumption and food preference experiment in the field and in the laboratory using natural OM collected from the field. Freshly cut grass and hyacinths were also offered to control for OM composition and large- and small mesh-sizes were used to distinguish microbial decomposition and invertebrate consumption. Results show that OM decomposition by microorganisms and consumption by invertebrates was similar throughout the study area, but that OM collected from ditches adjacent grasslands and freshly cut grass and hyacinths were preferred over OM collected from ditches adjacent to a hyacinth bulb field. In the case of OM collected from ditches adjacent hyacinth bulb fields, both microbial decomposition and invertebrate consumption were strongly retarded, likely resulting from sorption and accumulation of pesticides. This outcome illustrates that differences in agricultural practices can, in addition to direct detrimental effects on aquatic organisms, indirectly alter the functioning of adjacent aquatic ecosystems.
authors.affiliation: Institute of Environmental Sciences (CML), Leiden University, Leiden, The Netherlands.
authors.forename: Ellard R
authors.initials: ER
authors.lastname: Hunting
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics (IBED-AEE), University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: J Arie
authors.initials: JA
authors.lastname: Vonk
authors.affiliation: Institute of Environmental Sciences (CML), Leiden University, Leiden, The Netherlands.
authors.forename: C J M
authors.initials: CJM
authors.lastname: Musters
authors.affiliation: Institute for Biodiversity and Ecosystem Dynamics (IBED-AEE), University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Michiel H S
authors.initials: MHS
authors.lastname: Kraak
authors.affiliation: Institute of Environmental Sciences (CML), Leiden University, Leiden, The Netherlands.
authors.forename: Martina G
authors.initials: MG
authors.lastname: Vijver