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Phytoplankton Studies in Lower Narragansett Bay

Theodore J. Smayda
Limnology and Oceanography
Vol. 2, No. 4 (Oct., 1957), pp. 342-359
Stable URL: http://www.jstor.org/stable/2832835
Page Count: 18
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Phytoplankton Studies in Lower Narragansett Bay
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Abstract

A total of 82 surface samples were collected at three stations in lower Narragansett Bay from June 1954 through February 1955. Measurements of temperature, salinity, transparency, phosphate, iron, and oxygen were made, and 75 production and nutrient metabolism experiments were conducted. Maximum phytoplankton populations were encountered in September and January, the mean standing crop being considerably in excess of that recorded in adjacent areas. Two hurricanes evoked a vigorous response in the phytoplankton. Skeletonema costatum accounted for 81.2 per cent of the total population. Subsidence of the late winter flowering coincided with minimal phosphate concentrations. The development of the September maximum may reflect a decreased grazing rate. The role of stability and the degree of enclosure in the development of phytoplankton populations in protected areas are discussed. An "atypical" phosphate cycle was encountered in which a summer maximum and a winter minimum occurred. It is postulated that the periods of phytoplankton activity with their accompanying rates of assimilation and regeneration govern this. Three fractions of iron were characterized by marked variations in concentrations. A mean phosphate assimilation rate of $0.087\mu g-at\dot/L/day$ was obtained; regeneration rates were consistently negative. Iron assimilation had to be expressed as trends. On the average, diatoms increased by 53 per cent per day in the light bottle but decreased by 1.2 per cent day in the dark one. The effect of this on measurements of respiration and gross production were discussed. Average rates of gross production and respiration were 0.43 and $0.32 ml O_2/L/day$, respectively. The annual surface production was calculated to be $84 g C/m^3$ whereas it was $64 g C/m^3$ during the period of investigation.

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