Knowing something about the bathymetry of Glacier Bay allows us to more easily understand how marine habitat parameters (temperature, salinity, nutrients, phytoplankton, zooplankton, etc.) influence the distribution of seabird and marine mammal species in the bay. As the name suggests, the bathymetry of Glacier Bay was largely shaped by retreating glaciers at the end of the last ice age. Physical evidence of this glacial retreat can be seen in several areas.  Most notably is the terminal moraine at the mouth of Icy Strait (#1 on the map shown below). This moraine creates a shallow area in Glacier Bay (indicated on the map by the pale blue color). Shallow marine areas tend to concentrate zooplankton, fish, other prey species closer to the surface of the water, making them more available to foraging seabirds and marine mammals. (To view a slide show of seabird, forage fish, and marine mammal distributions in Glacier Bay, click here and choose the HTML version or PDF version.) Notice that the fjords in the northern reaches of Glacier Bay are narrow and deep (as illustrated by the darker shades of blue) but the coastal waters quickly become shallow. This rapid decrease in depth from the fjord's center to its coastline results in shallow water that is well mixed, cooler, and more saline. Again, these shallow waters concentrate prey and increase foraging opportunites for seabirds and marine mammals. Click on a Glacier Bay slide show link (HTML version or PDF version.) to see how seabirds and marine mammals concentrate along the coast in these fjords.