title: The use of (14)C tracer technique to assess the functional response of zooplankton community grazing to toxic impact.
abstract: The use of functional endpoints in risk assessment of pollutants for marine pelagic communities is scarce, especially for the function of zooplankton communities. This work presents a rapid, inexpensive and ecologically relevant technique to assess the effect of toxic compounds on the grazing rates of zooplankton communities. The combination of a (14)C-tracer labelling technique with a fast (< 3 h) and representative sub-sampling and handling makes it possible to measure changes in food uptake of freshly collected natural zooplankton communities in a short-term assay. The methodology is described and its validity is determined by a full account of the fate of isotope tracers (up to 15% taken up by zooplankton). Egg production of Acartia tonsa cultures exposed to DCOI yielded EC(50) values of 118+/-33 nM DCOI after three days, where EC(50) values from grazing of natural zooplankton communities was 136+/-29 nM DCOI, indicating that grazing was the more sensitive variable. Finally the method was tested in a mesocosm experiment designed to evaluate the toxicity of the antifouling compound zinc pyrithion (ZPT) with an EC(50) value of 17 nM ZPT (SD=3.3 nM, n=3). The method was found to be reproducible both at the community (CV=8-39%) and individual level (CV=23-53%), and could detect small changes in response to a toxicant in a natural pelagic system. The use of natural communities in combination with the fast and cost-effective procedure makes this technique a powerful tool in risk assessment, where lack of ecological relevance or reproducible results often results in unwanted high uncertainties.
authors.affiliation: Department of Marine Ecology, National Environmental Research Institute, Frederiksborgvej 399, DK-4000 Roskilde, Denmark. moh@dmu.dk
authors.forename: Morten
authors.initials: M
authors.lastname: Hjorth
authors.forename: Rune
authors.initials: R
authors.lastname: Haller
authors.forename: Ingela
authors.initials: I
authors.lastname: Dahllöf
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes; D033342:Copepoda / Q000187:drug effects* / Q000502:physiology; D044785:Cryptophyta / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004784:Environmental Monitoring / Q000379:methods*; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D009942:Organometallic Compounds / Q000633:toxicity*; D010063:Ovum / Q000187:drug effects; D010865:Pilot Projects; D011725:Pyridines / Q000633:toxicity*; D018570:Risk Assessment / Q000379:methods; D013844:Thiazoles / Q000633:toxicity*; D015048:Zooplankton / Q000187:drug effects* / Q000502:physiology
chemical_list: D002250:Carbon Radioisotopes; D009942:Organometallic Compounds; D011725:Pyridines; D013844:Thiazoles; C080469:Kathon 930; C010423:pyrithione zinc