Pacific Science Volume 27, Numbers 2, 1973

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Pacific Science is a quarterly publication devoted to the biological and physical sciences of the Pacific Region.

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    Tides and Circulation in a Series of Saline Lakes at Christmas Island
    (University of Hawaii Press, 1973-04) Gallagher, Brent
    Hydrographic conditions are presented for a series of seven saline lakes which open off of the main lagoon at Christmas Island, and which are being considered as a potential aquaculture site for brine shrimp. The first five ponds have typical tidal ranges of 1 foot and residence times of about 11 days. The two ponds farthest inland are penetrated only by spring tides and have residence times in the order of 15 months. The tides themselves, as well as mean water-level and tidal phase differences, present several possibilities for producing a controlled flow through the ponds. Circulation and structure in one of the innermost ponds show that no significant nutrient traps exist, and that flow patterns would serve to help collect floating brine shrimp eggs.
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    Primary Productivity in a Nutrient-Limited Tropical Estuary
    (University of Hawaii Press, 1973-04) Krasnick, George ; Caperon, John
    The results of a survey of phytoplankton productivity, chlorophyll a and nutrient concentrations in Pala Lagoon, American Samoa, are shown to be interpretable in terms of two regimes: an ocean-dominated region where productivity is controlled by fixed nitrogen concentrations, and a land-runoff-dominated regime where productivity is unrelated to major nutrient concentration. A quantitative relationship between nutrient concentrations in the lagoon and phytoplankton growth rates is presented. This relationship is used as the basis for predicting the effects of a proposed dredging operation within the lagoon as well as for predicting the effects of increased waste discharge into the local marine environment.
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    Three New Tanaids (Crustacea, Tanaidacea) from Southern Queensland
    (University of Hawaii Press, 1973-04) Boesch, Donald F.
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    Growth of a Sea Urchin, Allocentrotus fragilis, off the Oregon Coast
    (University of Hawaii Press, 1973-04) Sumich, James L. ; McCauley, James E.
    Allocentrotus fragilis (Jackson) was obtained from six stations at depths of 100 to 1,260 m on the continental shelf and upper slope off Newport, Oregon. Ages and growth rates of A. fragilis were determined by two methods: (1) from size-frequency distributions of trawl collections from 200 m, and (2) from growth zones on skeletal test plates. Collections from other depths were not adequate for size-frequency analyses. Gonad indices of A. fragilis from 200 m were used to determine spawning periodicity and frequency. A semiannual frequency was suggested, with spawning occurring in early spring and early autumn. No individuals collected below 400 m were reproductively mature. A procedure was developed to make growth zones of the skeletal test plates visible. Dark growth zones are thought to correspond to semiannual periods of growth, one-half the number of dark growth zones indicating the urchin's age. The growth curve of A. fragilis from 200 m, which was plotted from the mean test diameter of age groups defined by test plate growth zones, shows a good least-squares fit to von Bertalanffy's growth equation. Growth rates determined from plate growth zones appeared to be similar for A.fragilis from 100 to 600 m, but decreased for specimens from 800 to 1,260 m. The asymptotic size decreased with increasing depth below 200 m.
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