Dissolved aluminum (Al) and manganese (Mn) and total dissolvable Al and Mn from subsurface water samples collected during three cruises in 2010 in the northern Gulf of Alaska

Water samples were collected along a transect during three cruises in 2010 (7-9 April, 5-7 May, and 27-29 July) in the northern Gulf of Alaska, from the mouth of the Copper River to about 50 kilometers past the shelf break. Vertical profiles were collected using Teflon-lined Niskin bottles attached to a Spectra™ (Dyneema) line and triggered using Teflon-lined messengers. Additionally, profiles of salinity, temperature, fluorescence, and turbidity were measured with a Seabird SBE16 CTD, deployed at the same time as the collection of the subsurface water samples. Water samples were processed in the shipboard clean lab within three hours of collection. Dissolved samples were filtered using acid-washed 0.45-micrometer Pall-Supor filters. All samples were acidified to pH 1.8 using Seastar grade HCl within 3 days and stored for 5 years before analysis.

Filtered samples were analyzed for dissolved aluminum (Al) and unfiltered samples were analyzed for total dissolvable Al using Flow Injection Analysis (Resing and Measures 1994) using fluorescent detection of lumogallion. Filtered samples were analyzed for dissolved manganese (Mn) and unfiltered samples were analyzed for total dissolvable Mn according to the method of Resing and Mottl (1992), which uses spectroscopic detection of leuchomalachite green.