We sampled 27 tundra lakes and ponds during July and August of 2002, 2003 and 2004. Five of the water bodies were located in coastal subarctic northern Quebec (in the vicinity of Whapmagoostui-Kuujjuarapik), 9 in subarctic Alaska, 4 in the subarctic Mackenzie River Delta, 5 on Cornwallis Island and 5 on Ellesmere Island in the Canadian High Arctic. Samples of the dominant crustacean zooplankton species (12 different zooplankton species representing 31 populations of adults) were obtained by horizontal trawls using a 250 μm mesh sized net attached to a long pole. Phytoplankton samples of subsurface water were taken with acid-washed, 1L Nalgene bottles and water was filtered onto GF/F fliters. Mat cores were gently taken with a 6 or 10 mm diameter sediment corer (a syringe with the end cut off) and the top 1 mm of the core was sectioned with a blade. Chlorophylls, carotenoids and scytonemin of all samples were analysed by HPLC. UV-absorbing substances with properties similar to MAAs from phytoplankton (on filters), algal mats (cores) and zooplankton were quantified in a Cary-Varian spectrophotometer within the waveband from 220 to 400 nm. Melanin was quantified in zooplankton samples.