Responses of Lyngbya magnifica Gardner to an algaecide exposure in the laboratory and field

Predicting responses of organisms exposed to toxic materials in the field from results produced in laboratory studies and confirming those predictions has been a central question in aquatic toxicology since its inception. A field treatment of a cyanobacterium and laboratory measurements of responses to algaecide exposures provided an opportunity to address that question. This research involved predicting the response of Lyngbya magnifica to an algaecide exposure (Phycomycin® SCP) in the laboratory and evaluating that prediction with a comparable exposure in the field. Based on the results from initial laboratory experiments, an effective algaecide and concentration (i.e. 92 mg Phycomycin® SCP/g algae) were selected for field application in a farm pond. L. magnifica chlorophyll a and biomass were measured initially and 1, 4, 7, 10, and 21 days after treatment (DAT) for both laboratory and field exposures. Measurements of chlorophyll a decreases in the field treatment at 7, 10, and 21 days after treatment were significantly greater than responses obtained in similar laboratory exposures of Phycomycin® SCP. Biomass was significantly decreased in the field at 21 DAT compared to laboratory measurements. This approach can be effective for site specific predictions and can provide valuable information for informed decisions regarding water resource management and should be included in a management plan for increased product efficiency and ecological safety.

► Comparable exposures (mass of algaecide/mass algae) elicit similar responses.
► Laboratory results can be effectively scaled to the field.
► Predicting responses of algae in the field is required for efficient management.