Algal pigments in fast ice and under-ice water in an Arctic fjord

Samples of the bottom layer (4 cm) of fast ice and under-ice water were collected in May 1997 from the Adventfjorden (Spitsbergen). Concentrations of particulate organic matter (POM) in the bottom layer of the fast ice and under-ice water were similar (about 5.5 mg 1(-1)). However, the content of POM in total particulate matter (TPM) was significantly higher (p < 0.001) in ice (25%) than in water (16%). Algal biomass expressed as chlorophyll a within ice was 2.97 mug 1(-1) melt ice in comparison with 1.33 mug 1(-1) in under-ice water. Based on algal pigment determination we found that algal communities in the bottom of the fast ice were composed of the following taxonomic groups: diatoms (68.1%), chlorophytes (20.1%), prasinophytes (10.4%) and cryptophytes (1.4%), whereas under-ice water was dominated by diatoms (56.6%), chlorophytes (31.1%) and prasinophytes (12.3%). The ratio of diatoms and chlorophytes to chlorophyll a signal differed significantly between the two environments. Chlorophyllide a was the most abundant degradation product of chlorophyll a.