Phytoplankton production in a central Texas reservoir.

Phytoplankton production and other environmental variables were measured from June to November, 1968 to determine factors affecting production and trophic status of the producer community in a shallow, polymictic, central Texas reservoir. The reservoir was highly productive and eutrophic. Net phytoplankton production estimates, derived from data, averaged 390 mg C m“3 day“^, 857 mg C m“2 day”^, and 300 g C m"^ yr~for the impoundment. Light extinction by organic and inorganic turbidity limited phytoplankton production by decreasing the photic depth. Nutrient limitation was of minor importance, although greater production occurred near points of nutrient inflow than in other reservoir areas. Wind-mixing of the reservoir is believed to accelerate its eutrophication by promoting rapid nutrient recirculation, and thus maintaining nutrient availability for primary production. The impoundment is expected to age more rapidly with time as its basin shallows and phytoplankters spend an increasingly larger fraction of their lives in the productive zone.