A Radionuclide Tracer Study of Arthropod Food Chains in a Spartina Salt Marsh Ecosystem

The arthropods of the Spartina marsh obtain their energy either by grazing on the marsh grass or by eating the microbial—rich organic detritus that is largely derived from the dead Spartina. The two energy sources were labeled with P 3 2 in separate quadrats and the subsequent buildup of radioactivity followed in the arthropod populations. Four species of insects were dominant grazing organisms (one Orthoptera, two Hemiptera and one Homoptera) while two families of Diptera, (Dolichopodidae and Ephydridae) included the important insects associated with the detritus complex. The spiders were the important carnivores and obtained their energy from both the detritus and grazing food chains.