. Elements of ecology. Ecology. 290 Nutrients manures have been supplied to fish ponds in the Old World for cen- turies, but in the 1930s the use of chemical fertilizers was begun on an expanding scale in the United States. By broadcasting fertilizer, such as "6-9-2" to "12-9-2," over the pond from the shore (Fig. ), or from a boat, the concentration of nutrients is maintained continu- ously at such a level that phytoplankton can flourish through the warm. Fig. Broadcasting commercial chemical fertilizer over a pond in Belmont, Mass., to supply nutrients to the phyt
. Elements of ecology. Ecology. 290 Nutrients manures have been supplied to fish ponds in the Old World for cen- turies, but in the 1930s the use of chemical fertilizers was begun on an expanding scale in the United States. By broadcasting fertilizer, such as "6-9-2" to "12-9-2," over the pond from the shore (Fig. ), or from a boat, the concentration of nutrients is maintained continu- ously at such a level that phytoplankton can flourish through the warm. Fig. Broadcasting commercial chemical fertilizer over a pond in Belmont, Mass., to supply nutrients to the phytoplankton at the beginning of the food chain. season of the year. The thick growth of planktonic plants provides abundant food for copepods, cladocerans, and other types of zoo- plankton and for the bottom fauna, among which chironomids are particularly prominent. The resulting increase in the abundance of these invertebrates stimulates the growth of fish such as the blue- gill sunfish that feed upon them, and the enlarged population of these "forage" fish furnishes a rich food supply for predatory species such as the bass. In this way the production of pan fish or sport fish in the pond is significantly improved (Edminster, 1947; Meehean, 1952 and succeeding articles in the Symposium on Farm Fish Ponds and Management). Similar augmentation in the growth of marine fish by the use of commercial fertilizer to stimulate the development of phytoplankton and subsequent links in the food chain has been demonstrated in Scottish sea-lochs (Gross, 1947; Raymont, 1950).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Clarke, George L. (George Leonard), 1905-. New York, Wiley
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