Comparative benthic plant ecology by SCUBA-monitored quadrats

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The feasibility of permanent benthic quadrats checked by SCUBA divers was tested. Stations were set up on the bottom of six representative aquatic habitats, both marine and inland, including oligotrophic and eutrophic ponds, river, coastal lagoon, estuary, and open marine coast. Data include physical-chemical factors, species composition, number and height of shoots, and general observations. From volume/length constants, the standing crops per quadrat were calculated. Seasonal changes in environmental factors and plant standing crop are parallel-plotted for the six habitats, thus providing comparative information on stations. Benthic diel periodicity and light intensity periodicity at various depths were investigated also. In all habitats, maximum standing crop occurred in July and August, but species composition varied considerably. Length of time the water temperature exceeded 15C did not correlate with standing crop. Dissolved oxygen was never deficient, even under ice; and diurnal changes were slight. Light was diminished under ice, but 4-60 ft-c were recorded in midwinter. Lenght of day is about 2 hours shorter at 20 ft than at 6 ft. Onset of vernal benthic growth seems correlated more closely with increase in light intensity than with temperature. The permanent quadrats monitored by divers proved feasible in all habitats tested, and directly comparable data were obtained. © 1969 Dr. W. Junk Publishers.

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