Effects of physical phenomena on the distribution of nutrients and phytoplankton productivity in a coastal lagoon |
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| Authors: | Roberto Millan-Nuñez Saul Alvarez-Borrego David M Nelson |
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| Institution: | 1. School of Oceanography, Oregon State University, Corvallis, Oregon 97331, U.S.A.;2. Centro de Investigation Cientifica y Education, Superior de Ensenada, Espinoza 843, Ensenada, Baja California, Mexico |
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| Abstract: | Sea level, salinity, temperature, nitrate, nitrite, phosphate, silicate, chlorophylls a, b and c and their phaeophytins, phytoplankton abundance and phytoplankton productivity time series were generated for the mouth and three interior locations of Bahia San Quintin, Baja California, Mexico, for 10 days during summer of 1979. The samples were taken once every 2 h. This was done to describe space and time variability of these ecological properties and to elucidate the main factors that cause this variability. Upwelling events bring nutrient reach waters near the bay mouth and tidal currents propagate those waters throughout the bay. Nutrient remineralization at the sediments and the effect of turbulence induced by tidal currents and winds increase nutrient concentrations in the interiors of the bay. In comparison with available information on nutrients limited growth of planktonic algae, nutrients seemed not to be limiting to phytoplankton growth during the sampling period. Phytoplankton cell abundances at the extremes of the lagoon are an order of magnitude lower than at the mouth due to greater turbidity. Chlorophyll concentrations at the extremes are about one-third of those of the mouth. Primary productivity decreases from the mouth to the interiors in the same manner as chlorophyll does. There is not a significant difference in cell size between phytoplankton at the bay mouth and those at the extremes of the bay. Primary productivity in the bay is comparable to the productivity maxima of other upwelling areas. There is no clear permanent dominance of diatoms over dinoflagellates, or vice versa, at any location in the bay. The alternation of upwelling and non-upwelling played an important role, together with that of the spring-neap tide cycle, in producing low frequency (< 0.01 cycles h?1) temporal variability of ecological properties throughout the bay. |
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| Keywords: | time series spectral analysis nutrients productivity upwelling coastal lagoons Baja California coast |
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