Sandy mud beach Food web

Shown above is a very complex diagram of the interrelationships between various food items and their predators.  To understand the diagram use the Great Blue Heron (look up the animal) as an example.  Follow the arrows backward from the Heron to it’s prey and then from the prey to it’s prey. 

So we find from the diagram that the heron feeds on the Penpoint Gunnel and the Pacific Staghorn Sculpin.  The Penpoint Gunnel in turn feeds on Mysids who in turn feed on Detritus (bits and pieces of plant and animal material).  The Pacific Staghorn Sculpin however feeds on Gammarid Amphipods while the Gammarid Amphipods also feed on Detritus.  So Detritus is a major base of the food web.

This diagram is from a report  by Si Simenstad, et al. 1979. Food web relationships of northern Puget Sound and the Strait of Juan de Fuca; a synthesis of available knowledge, EPA Report #EPA-600/7-79-259.