Experiments were conducted by collecting raw seawater, filtering it through 200µm mesh sieves into 20L carboys, and then dispensing it into experimental jars. Triplicates bottles were used for each treatment. Treatments included whole seawater (control), whole seawater plus copepods (Zooplankton), and the same treatments plus PUA additions (Heptadienal, Octadienal, Decadienal, and Mixed PUA). PUA were dissolved in methanol and added to experimental bottles for a final concentration of 21 nM; for the mixed PUA treatment this was 7nM of each type of PUA.

Initial samples were collected from the carboy for microzooplankton as described below. Final samples were collected from each treatment and control bottle as described below.

Microzooplankton samples were collected by gently decanting 100ml of each treatment bottle into a sample bottle and preserved with 2% acid Lugol’s solution (final concentration). Identification and sorting of microzooplankton was done by settling 10-25 ml of sample in Utermöhl chambers and counting with an Olympus IX-70 inverted microscope equipped with differential interference contrast (DIC), epifluorescence, and a digital camera. Microzooplankton biovolumes were calculated from their dimensions and approximate shapes (Sun and Liu 2003), and converted to carbon using published empirical relationships (Menden-Deuer and Lessard 2000). Tintinnid volumes were calculated based on their cell dimensions.

All data were processed in Microsoft Excel.