Winkler Titration Samples are preserved in 60-ml BOD bottles and stored at room temperature for no more than 24 hours in the dark. SA720 pH meter with a Ross combination electrode. Total , Inorganic, and Organic Phosphate Total P is determined by ashing sediments or samples on filters at 550C followed by extraction with HCl. The HCl extract is then measured by the method of Murphy and Riley, 1962. Inorganic P is determined by the same process without the initial ashing step.
Organic P is determined by difference.
Filters are folded over on themselves, wrapped in Al foil, and stored frozen. Sediment cores to be analyzed for pigments are sectioned by 1 cm increments to 5cm. Each section is placed in a separate centrifuge tube and stored frozen. Potentials are corrected for the potential of the reference electrode. Samples for 15N and 13C are analyzed using an automated elemental analyzer with a cryogenic purification system coupled to a Finnigan Delta S isotope mass spectrometer.