PARENT SESSION

2B - Natural Stressors and Toxicants
Poster Hall
8:30 AM - Tuesday, 29 April 2003
Chair: Duquesne, S.¹, ¹

(TUP/77) Resilience of microbial sediment communities to high nutrient load and Copper Pyrithione.

Petersen, Dorthe^{1, 2}, Dahllöf, Ingela¹, Sundbäck, Kristina², ¹ National Environmental Research Institute, Roskilde, Denmark, Denmark² Göteborg University, Göteborg, Sweden, Sweden

ABSTRACT- Resilience describes the ability of a community to withstand stressors, which means that a perturbation only causes a temporary change in community function and structure and subsequently no lasting effect can be detected when compared to the control community. Resilience is often measured as resilience time, which describes the period from the initial disturbance to the point where the disturbed community is comparable to the control community again with respect to the endpoints measured. A mesocosmos experiment with whole sediment cores from shallow waters was performed to analyse the resilience time of sediment communities after introduction of increased nutrient levels and the antifouling component, Copper Pyrithione (CPT). This scenario describes a situation where sediment in shallow waters has increased nutrient- and CPT levels due to human activities. Resilience time was analysed using both functional and structural endpoints. The structural parameters included analysis of bacterial diversity by molecular fingerprinting (PCR-DGGE) and total DNA concentration. The functional parameters included measurement of bacterial protein synthesis ([¹⁴C]-leucine incorporation) and analysis of fluxes of nutrients (NO₃^-, NH₄⁺, P, Si). Preliminary results show that sediments with added CPT (4 nmol/g dry sediment) and control levels of nutrients have a decreased bacterial protein synthesis compared to control sediments. This effect is, however, only found for a short period of time (1 week). The bacterial protein synthesis from sediments with both increased nutrient and CPT levels also decrease during the first week followed by an increase in protein synthesis, which lasted for one month. These results suggest that the resilience time based on measurements of bacterial protein synthesis is longer for sediments with increased nutrient and CPT level compared to sediments where addition of CPT is the only perturbation. Resilience time based on analysis on fluxes of nutrients and fingerprinting analysis bacterial diversity will also be presented.

Key words: sediments, resilience, bacteria, mesocosmos