Macronutrient supply, uptake and recycling in the coastal ocean of the west Antarctic Peninsula

Henley, S. F., Tuerena, R. E., Annett, A. L., Fallick, A. E., Meredith, M. P., Venables, H. J., Clarke, A. and Ganeshram, R. S. (2017) Macronutrient supply, uptake and recycling in the coastal ocean of the west Antarctic Peninsula. Deep-Sea Research Part II: Topical Studies in Oceanography, 139, pp. 58-76. (doi: 10.1016/j.dsr2.2016.10.003)

Abstract

Nutrient supply, uptake and cycling underpin high primary productivity over the continental shelf of the west Antarctic Peninsula (WAP). Here we use a suite of biogeochemical and isotopic data collected over five years in northern Marguerite Bay to examine these macronutrient dynamics and their controlling biological and physical processes in the WAP coastal ocean. We show pronounced nutrient drawdown over the summer months by primary production which drives a net seasonal nitrate uptake of 1.83 mol N m-2 yr-1, equivalent to net carbon uptake of 146 g C m-2 yr-1. High primary production fuelled primarily by deep-sourced macronutrients is diatom-dominated, but non-siliceous phytoplankton also play a role. Strong nutrient drawdown in the uppermost surface ocean has the potential to cause transient nitrogen limitation before nutrient resupply and/or regeneration. Interannual variability in nutrient utilisation corresponds to winter sea ice duration and the degree of upper ocean mixing, implying susceptibility to physical climate change. The nitrogen isotope composition of nitrate (δ15NNO3) shows a utilisation signal during the growing seasons with a community-level net isotope effect of 4.19 ± 0.29‰. We also observe significant deviation of our data from modelled and observed utilisation trends, and argue that this is driven primarily by water column nitrification and meltwater dilution of surface nitrate. This study is important because it provides a detailed description of the nutrient biogeochemistry underlying high primary productivity at the WAP, and shows that surface ocean nutrient inventories in the Antarctic sea ice zone can be affected by intense recycling in the water column, meltwater dilution and sea ice processes, in addition to utilisation in the upper ocean.

• Item Type: Articles
• Additional Information: This work was funded by the UK Natural Environment Research Council (NERC) via Standard Grant NE/ F004524/1, a Ph.D Studentship for S.F.H. and the Antarctic Funding Initiative and Collaborative Gearing Schemes of the British Antarctic Survey (CGS 10/50, CGS 11/56)
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Fallick, Professor Anthony
• Authors: Henley, S. F., Tuerena, R. E., Annett, A. L., Fallick, A. E., Meredith, M. P., Venables, H. J., Clarke, A., and Ganeshram, R. S.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Deep-Sea Research Part II: Topical Studies in Oceanography
• Publisher: Elsevier
• ISSN: 0967-0645
• ISSN (Online): 1879-0100
• Published Online: 13 October 2016
• Copyright Holders: Copyright © 2016 The Authors
• First Published: First published in Deep-Sea Research Part II: Topical Studies in Oceanography 139:58-76
• Publisher Policy: Reproduced under a Creative Commons License