Composition of Phytoplankton

The Hudson River contains a diverse array of phytoplankton, but diatoms (Baciliariophycea) are the numerical and biomass dominants and account for the majority of the species identified from the river (Marshall, 1988; Smith et al., 1998). Working in the tidal-freshwater river, Marshall (1988) identified 137 species of phytoplankton of which 43 percent were diatoms, 27 percent were Cholorophyceae, and 15.3 percent were Cyanobacteria. Other major groups (Cryptophyceae, Chrysophyceae,

Figure 9.2. Twelve years of nutrient concentrations near Kingston, New York (river km 144). Shown are the means, by month (with SD for that month among years) for weekly to bi-weekly data for 14 years 19862000. The upper panel shows inorganic N; open circles are NH4; x's are NO3. The lower panel shows PO4. These data are a summary of nutrient analysis from more than 500 individual dates sampled.

Figure 9.2. Twelve years of nutrient concentrations near Kingston, New York (river km 144). Shown are the means, by month (with SD for that month among years) for weekly to bi-weekly data for 14 years 19862000. The upper panel shows inorganic N; open circles are NH4; x's are NO3. The lower panel shows PO4. These data are a summary of nutrient analysis from more than 500 individual dates sampled.

and Pyrrhophyceae) are represented in the river but with fewer species and much less biomass (Smith et al., 1998). Earlier work on the taxonomic structure of Hudson River phytoplankton reveals broadly similar conclusions, a dominance of diatoms and the presence of many other groups (Frederick et al., 1976; Sirois and Frederick, 1978; Howells and Weaver, 1969). Chapter 19 by Strayer reviews some of the factors that may regulate the difference in phytoplankton community structure in the Hudson (Caraco et al., 1997; Smith et al., 1998). We have not seen picoplankton (cells <3 | M) in the samples we have counted in the tidal-freshwater portion of the river and know of no published data suggesting that picoplank-ton are an important component of the Hudson River phytoplankton. Picoplankton have been reported as an important component of other coastal rivers (Kobayashi, Williams, and Kotlash, 2000).

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