1. May-June 2002
Akutan Pass 1 and Unimak Pass 1 are the first visit to the passes in May, Akutan Pass 2 and Unimak Pass 2 are the second visits to the passes (June 2002). Note the distinct differences in salinity and temperature between the passes to the east and west of Samalga Pass. Samalga Pass seems to be the boundary between shelf water to the east and oceanic water to the west. UpperMixedSal is the mean salinity in the upper mixed layer. LowerMixedSal is the mean salinity below the pycnocline to 100 m depth. MeanSal is the mean water column salinity above 100 m depth. The error bars are 95% confidence intervals for mean salinity and temperature in the respective passes.

2. May – June 2002
This slide shows both seasonal influences and water mass influences on zooplankton species composition. The declines in abundance of Neocalanus plumchrus and N. flemingeri at Akutan2 and Unimak2 (red line, upper plot) are due to their annual life cycle. They leave the surface waters and migrate down to depths over 300 m in May and June. Elevated abundances of Calanus marshallae and Acartia spp. (blue and black lines, upper plot) at Umnak, Akutan and Unimak Passes are due to their preference for warmer neretic conditions. Lower plot shows two species of euphausiid. The black line shows abundance Thysanoessa inermis, which prefers neretic water of Akutan, Unimak and Samalga Passes, the red line show abundance of Euphausia pacifica, which prefers more oceanic conditions of the passes west of Samalga Pass. Pass Names: Um1 = Unimak (May), Ak1 = Akutan (May), Tng = Tananga (June), Sgm = Seguam (June), Smg = Samalga (June), Un2 = Unimak (June), Ak2 = Akutan (June). The error bars are 95% confidence intervals for power transformed mean abundance in the respective passes. The broad error bars are due to the very patchy distribution of these organisms, especially in the passes where tidally generated eddies can physically concentrate or disperse zooplankton.