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Nitrogen uptake dynamics of a persistent cyanobacterium Cyanothece sp. bloom in Lake St Lucia, South Africa

Nitrogen uptake dynamics of a persistent cyanobacterium Cyanothece sp. bloom in Lake St Lucia,... Worldwide, persistent cyanobacterial blooms are becoming more frequent and are often associated with effects of global climate change. In June 2009, a widespread bloom of the unicellular cyanobacterium, Cyanothece sp., appeared in North Lake and False Bay of Lake St Lucia – a large (360 km2) estuarine lake system in KwaZulu-Natal, South Africa – and persisted for 18 months. It remains unclear how the bloom status was maintained for so long. This study investigates aspects of the nutrient uptake dynamics of Cyanothece sp. and how this process may relate to maintaining a persistent bloom state during hypersaline conditions. 15N nutrient uptake experiments were performed to evaluate the effect of the most important environmental variables on the nutrient uptake rate of Cyanothece sp. Highest 15N uptake rates were during salinities of 35 and temperatures of 30 °C for both N sources (43.9 [SE 18.3] and 85.5 [SE 42.9] µg atom N l–1 h–1 for and respectively). In contrast, at high salinities of 160 and low temperatures of 10 °C, and uptake rates were low (3.76 [SE 0.23] and 14.5 [SE 6.40] µg atom N l–1 h–1 respectively). Hence nutrient uptake was significantly influenced by environmental variables, particularly salinity, which suppressed uptake rates, and temperature, which facilitated them. The long-term bloom maintenance appears to be attributed to efficient nutrient uptake rates, absence of grazers during the hypersaline phase, and the ability of Cyanothece sp. to outcompete other microalgae at temperatures >25 °C. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png African Journal of Marine Science Taylor & Francis

Nitrogen uptake dynamics of a persistent cyanobacterium Cyanothece sp. bloom in Lake St Lucia, South Africa

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Nitrogen uptake dynamics of a persistent cyanobacterium Cyanothece sp. bloom in Lake St Lucia, South Africa

Abstract

Worldwide, persistent cyanobacterial blooms are becoming more frequent and are often associated with effects of global climate change. In June 2009, a widespread bloom of the unicellular cyanobacterium, Cyanothece sp., appeared in North Lake and False Bay of Lake St Lucia – a large (360 km2) estuarine lake system in KwaZulu-Natal, South Africa – and persisted for 18 months. It remains unclear how the bloom status was maintained for so long. This study investigates aspects of the...
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Publisher
Taylor & Francis
Copyright
Copyright © NISC (Pty) Ltd
ISSN
1814-2338
eISSN
1814-232X
DOI
10.2989/1814232X.2014.922124
Publisher site
See Article on Publisher Site

Abstract

Worldwide, persistent cyanobacterial blooms are becoming more frequent and are often associated with effects of global climate change. In June 2009, a widespread bloom of the unicellular cyanobacterium, Cyanothece sp., appeared in North Lake and False Bay of Lake St Lucia – a large (360 km2) estuarine lake system in KwaZulu-Natal, South Africa – and persisted for 18 months. It remains unclear how the bloom status was maintained for so long. This study investigates aspects of the nutrient uptake dynamics of Cyanothece sp. and how this process may relate to maintaining a persistent bloom state during hypersaline conditions. 15N nutrient uptake experiments were performed to evaluate the effect of the most important environmental variables on the nutrient uptake rate of Cyanothece sp. Highest 15N uptake rates were during salinities of 35 and temperatures of 30 °C for both N sources (43.9 [SE 18.3] and 85.5 [SE 42.9] µg atom N l–1 h–1 for and respectively). In contrast, at high salinities of 160 and low temperatures of 10 °C, and uptake rates were low (3.76 [SE 0.23] and 14.5 [SE 6.40] µg atom N l–1 h–1 respectively). Hence nutrient uptake was significantly influenced by environmental variables, particularly salinity, which suppressed uptake rates, and temperature, which facilitated them. The long-term bloom maintenance appears to be attributed to efficient nutrient uptake rates, absence of grazers during the hypersaline phase, and the ability of Cyanothece sp. to outcompete other microalgae at temperatures >25 °C.

Journal

African Journal of Marine Science – Taylor & Francis

Published: Apr 3, 2014

Keywords: 15 N isotope pairing technique; cyanobacteria; estuarine lake; hypersalinity; iSimangaliso; unicellular

References

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