Sampling strategies for measuring macroalgal biomass in the shallow waters of the Venice lagoon.

Abstract A number of procedures were tested to set up a reliable method for determining macroalgal standing crops in the shallow waters of the Venice Lagoon, populated by macroalgae with different densities and variously distributed over the bottom. Accurate and precise measures of biomass were obtained using a box of 1m2 and a grid sampling scheme. Three areas (15 × 15 m2) characterized by high (5–20 kg m‐2), low (0.1–1.0 kg m‐2) and intermediate (1–10 kg m‐2) biomass densities were studied. Twenty sub‐samples were taken in each area and the results obtained were considered as the best estimate of the true mean of the population in the area. The difference between the best estimate of the total macroalgal population mean (BEM) and the mean of different sets of sub‐samples (SM) divided by the best estimate of the mean: | BEM‐SM |/BEM was proved the most efficient parameter to attain a value which differs by a given percentage ‐at 95% probability‐from the true macroalgal biomass, considering all the possib...

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