Figure 1.
A conceptual model of the whale pump.
In the common concept of the biological pump, zooplankton feed in the euphotic zone and export nutrients via sinking fecal pellets, and vertical migration. Fish typically release nutrients at the same depth at which they feed. Excretion for marine mammals, tethered to the surface for respiration, is expected to be shallower in the water column than where they feed.
Figure 2.
Shipboard incubation time-course experiments on Humpback whale samples collected on Stellwagen Bank, Gulf of Maine.
(a) Net NH4+ production vs. fecal PON concentration in time course incubations of material collected in whale fecal plumes. Samples 1 and 2 had the highest initial NH4+ concentrations, yet their rates of NH4+ production ranged from the second lowest to the highest in the entire data set. (b) NH4+ concentration vs. incubation time.
Figure 3.
The flux of nitrogen in the Gulf of Maine (a) at present and (b) before commercial hunting.
Point-source pollution, industrial emissions of nitrogen, and allochthonous sources from Townsend [18]. The range of historical estimates are adapted from Lotze [66]. Sources that are not expected to be influenced by anthropogenic change, such as offshore transport from Scotian Shelf water, are not included in this graph.
Table 1.
Effect of common and historically important marine mammals on the nitrogen cycle in the Gulf of Maine ecosystem.
Table 2.
Contemporary nitrogen flux in the Gulf of Maine.
Figure 4.
The role of cetaceans in the nitrogen cycle by season.
Seasonal estimates based on the percentage of total consumption in the Gulf of Maine [24].
Table 3.
Body mass and consumption rates for cetaceans and seals in the Gulf of Maine.