2.2. Measuring C:N:P of Sargassum tissue
As a test of the neritic nutrient enrichment hypothesis, we collected
samples of S. natans and S. fluitans fromthe nine neritic and nine oceanic
locations during research cruises in 1986 and 1987 (Fig. 2) for tissue
C:N:P analysis. Freshly collected composite samples (6–10 apical thalli
per species) of S. natans and S. fluitans were cleaned of macroscopic
epizoa and epiphytes, rinsed briefly (3–5 s) in deionized water, dried
in a laboratory oven at 70 °C for 48 h, and powdered with a mortar
and pestle (Lapointe et al., 1992). Total C and N were determined
(n = 2 per species for each location) on a Carlo-Erba CHN Analyzer
and total P was determined by persulfate digestion followed by analysis
for soluble reactive phosphorus (Menzel and Corwin, 1965). The
resulting tissue % C, N and P data were used to calculate molar C:N:P
ratios to allow comparison with other published data formacroalgae
as well as the Redfield Ratio (106:16:1; Redfield, 1934). Calculated
molar C:N:P ratios of S. fluitans and S. natans in neritic and oceanic
waters were analyzed using a two-way ANOVA.