Abstract
The objective of this work was to estimate the changes in abundance and composition of phytoplankton in a coastal lagoon in Baja California, México during neap-spring tide conditions. Sampling was conducted from the 7th to the 16th of October 2004. Surface water was collected at 18 stations distributed across the bay during day time at high tide. Also, a time series was collected at a fixed station; surface water was collected every two hours from 8:00 to 18:00. High temperatures, low salinities and low nutrient concentrations at the oceanic end indicated weak or non upwelling conditions during this period. The phytoplankton community was characterized using an inverted microscope and the chemical taxonomy program CHEMTAX, based on pigment concentration estimated by high performance liquid chromatography (HPLC). The phytoplankton concentration was two times lower during this period than during periods of upwelling in the same year. Cryptophytes and diatoms were the most abundant groups estimated by CHEMTAX. Statistical analyses of the effect of tidal conditions on phytoplankton composition indicate that Zone A is strongly affected by tides, and that tidal effects are lessened at the inner zones. Differences in phytoplankton abundance between zones and between tidal conditions indicate that phytoplankton distribution is patchy in the lagoon.
Highlights
Among other reasons, the distribution and abundance of phytoplankton in coastal lagoons have been studied to determine their usefulness for the growth of organisms in culture, as in the case of San Quintin Bay (SQB), a tidally dominated coastal lagoon with oyster cultures
Mackey et al [9] proposed the Chemical Taxonomy (CHEMTAX) program to estimate the composition of the phytoplankton community using the concentration of chlorophyll a (Chla) and accessory pigments derived from high performance liquid chromatography (HPLC) analysis
Phytoplankton abundance has mostly been evaluated by microscopy [1] [2] [4], and only one published study of phytoplankton abundance and composition has been based on HPLC pigments [3]
Summary
The distribution and abundance of phytoplankton in coastal lagoons have been studied to determine their usefulness for the growth of organisms in culture, as in the case of San Quintin Bay (SQB), a tidally dominated coastal lagoon with oyster cultures. Studies of phytoplankton abundance in SQB at spatial and temporal scales have been sporadic and mostly during spring and summer seasons [1]-[5]. These studies allowed describing changes in the abundance and composition of phytoplankton that occur within the lagoon. The advantage of the microscopy method is the capability of identifying species, revealing morphological characteristics of each species, such as individual cell size, shape, the presence of colonies, spore formation, and association with other species [8] This method is time consuming and requires taxonomy expertise. Considering the strong physical dynamics of SQB and the lack of data during autumn, the objective of this work was to estimate the effect of tidal conditions (neap, transition and spring) on the distribution, abundance and composition of phytoplankton in SQB
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