Vertical Fine Structure of Particulate Matter and Nutrients in Sea Ice of the High Arctic

The vertical fine structure of particulate matter and inorganic nutrients through the bottom layers of sea ice was determined at a site in the Canadian high arctic. Intense vertical gradients of chlorophyll a, nitrate, ammonium, nitrite, phosphate, and silicate developed in the lower 6 cm of the ice as ice algae attained standing crops of 250 mg∙m−2 (up to 60 mg∙L−1) of chlorophyll a. Pigment and inorganic nutrient concentrations were closely correlated, and pools of inorganic nutrient were shown to exist in the particulate matter, suggesting that the extremely high dissolved nutrient concentrations in the bottom ice (e.g. up to 400 μmol∙L−1 nitrate) were derived at least in part from leakage of algal intracellular pools. Nitrogen and phosphorus were present in excess of algal needs, but silicon may not have been. The ratios of particulate organic carbon to chlorophyll a and to particulate organic nitrogen increased from the ice–water interface upwards, consistent with a physiological response of the ice ...