In a typical run of the 1-D model, the large phytoplankton bloom first, followed by a larger bloom of the small phytoplankton fraction. The larger phytoplankton species grow at lower temperatures, but are very sensitive to nutrient depletion, whereas small phytoplankton species prefer warmer temperatures and are less sensitive to lower nutrient concentrations. Nutrients become depleted in the surface waters following the large bloom of small phytoplankton, as is seen in data from the Shelikof Strait region (Napp et al., 1996). Heterotrophic dinoflagellates show higher densities than tintinnids due to their ability to eat both large and small phytoplankton, however tintinnids begin to comprise a larger fraction of the microzooplankton after the small phytoplankton begin to grow, perhaps accounting for the second bloom of tintinnids in June, after the May bloom of small phytoplankton. Neocalanus, spp. increase until they begin to be removed from the upper water column by diapause in early to mid-summer. Euphausiid concentrations increase gradually over time until the late summer when their density begins to decrease. No vertical migration is included for Neocalanus, spp. or euphausiids.

Timeseries of vertically integrated variables:

NPZ variables in Depth and Time:

In water columns which were well mixed from surface to bottom, nutrients were depleted in the entire water column by late June. Several blooms were seen, with large phytoplankton blooming first, followed by repeated blooms of small phytoplankton. Microzooplankton and small copepods responded to each bloom in a cyclic manner, as nutrients were resupplied from deep waters, causing a bloom, which was then brought under control by grazers.

When levels of mixing were low throughout the water column, nutrients gradually became depleted in the upper layer, but remained abundant at depth. Only small, early blooms were seen, and consequently densities in the upper trophic levels remained low. With high wind mixing and low tidal mixing, nutrients also became depleted in the upper layers due to reduced resupply from deep waters. Several blooms were seen, including a late deep bloom of large phytoplankton. Microzooplankton responded to the early blooms of small phytoplankton, but not to the late deep bloom, whereas small copepods responded to all blooms. Euphausiids declined in the upper layers, but high concentrations continued at depth.

The parameter relating light absorption to phytoplankton density was the input variable which affected the most output variables. Variables which significantly affected more than 30% of the output variables examinated include the doubling rate of small phytoplankton, predation mortality on euphausiids, assimilation efficiency of heterotrophic dinoflagellates, the density independent mortality of small copepods, the critical nutrient concentration below which mortality for small phytoplankton is nutrient dependent, and the metabolized fraction for euphausiids.

The output variables sensitive to the most input parameters were the concentrations of nitrates at different times during the modeled period. Other sensitive variables include euphausiid densities in mid-summer, early small copepod densities and early euphausiid densities.