Six incubation experiments were carried out to investigate the phytoplankton biomass response to seabird guano-enrichment under different nutrient regimes. Study locations included Antarctic waters of the Ross Sea and sub-Antarctic waters offshore of the Otago Peninsula, both being characterized by iron limitation of phytoplankton productivity in summer, the Sub-Tropical Frontal Zone offshore of the Snares Islands,which is generally micronutrient-replete, and the island wakewaters of the Snares Islands,which have a high nutrient supply from land. In all of the experiments the increase of phytoplankton biomass was higher in the treatments with guano addition compared to the controls. Guano additions were compared to Fe and macronutrients treatments (both added in quantities similar to those in the guano treatment) to shed light on which constituent(s) of guano are responsible for the observed increases in phytoplankton biomass. Macronutrients increased the phytoplankton biomass in the Sub-Tropical Frontal Zone, however, the response was less prominent than in the Guano treatment, suggesting synergetic effects of nutrients in seabird guano on phytoplankton production. It was also found that the pattern of response varied between the water masses with 6–10 days lag phase in the Sub-Antarcticwater mass and no lag phase in Sub-Tropical Frontal Zone. The calculations presented here suggest that micro- and macronutrients delivered from seabird colonies on some of the sub-Antarctic islands may provide a significant amount of limiting nutrients to the nutrient budget of the surrounding coastal waters, potentially sufficient to sustain a local phytoplankton bloom. Findings of the present study indicate that biological recycling of nutrients by seabirds likely supports marine primary production and enhances productivity of associated food webs in the vicinity of islands.

Item Type:	Refereed Article
Keywords:	seabird guano, iron, Subantarctic, Antarctic
Research Division:	Biological Sciences
Research Group:	Ecology
Research Field:	Marine and Estuarine Ecology (incl. Marine Ichthyology)
Objective Division:	Environment
Objective Group:	Climate and Climate Change
Objective Field:	Ecosystem Adaptation to Climate Change
Author:	Gault-Ringold, M (Dr Melanie East)
ID Code:	113759
Year Published:	2016
Web of Science® Times Cited:	5
Deposited By:	CRC-Antarctic Climate & Ecosystems
Deposited On:	2017-01-19
Last Modified:	2017-11-01
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