Antarctic pack ice comprises about 90% of the sea ice in the southern hemisphere and plays an important structuring role in Antarctic marine ecosystems, yet measurements of ice algal primary production and nitrogen uptake rates remain scarce. During the early austral spring of 2012, measurements for primary production rates and uptake of two nitrogen substrates (nitrate and ammonium) were conducted at 5 stations in the East Antarctic pack ice (63–66°S, 115–125°E). Carbon uptake was low (3.52 mg C m−2 d−1) but a trend of increased production was observed towards the end of the voyage suggesting pre-bloom conditions. Significant snow covers reaching, up to 0.8 m, induced strong light limitation. Two different regimes were observed in the ice with primarily nitrate based ‘new’ production (f-ratio: 0.80–0.95) at the bottom of the ice cover, due to nutrient-replete conditions at the ice–water interface, and common for pre-bloom conditions. In the sea-ice interior, POC:PN ratios (20–70) and higher POC:Chl a ratios suggested the presence of large amounts of detrital material trapped in the ice and here ammonium was the prevailing nitrogen substrate. This suggests that most primary production in the sea-ice interior was regenerated and supported by a microbial food web, recycling detritus.
History
Publication title
Deep-Sea Research. Part II
Volume
131
Pagination
140-149
ISSN
0967-0645
Department/School
Institute for Marine and Antarctic Studies
Publisher
Pergamon-Elsevier Science Ltd
Place of publication
The Boulevard, Langford Lane, Kidlington, Oxford, England, Ox5 1Gb
Rights statement
Copyright 2015 Elsevier Ltd
Repository Status
Restricted
Socio-economic Objectives
Other environmental management not elsewhere classified