Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 14, issue 19
Biogeosciences, 14, 4423–4433, 2017
https://doi.org/10.5194/bg-14-4423-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 4423–4433, 2017
https://doi.org/10.5194/bg-14-4423-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 06 Oct 2017

Research article | 06 Oct 2017

Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

Yafei Zhu1,2, Andrew McCowan2, and Perran L. M. Cook1 Yafei Zhu et al.
  • 1Water Studies Centre, Monash University, Clayton 3800, Australia
  • 2Water Technology Pty Ltd, 15 Business Park Drive, Notting Hill 3168, Australia

Abstract. The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes) were investigated using a 3-D coupled hydrodynamic biogeochemical water quality model. The study showed that primary production was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment were the main drivers for the hypoxia and subsequent sediment phosphorus release in Lake King. High primary production stimulated by large nitrogen loading brought on by a winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads), which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria). Therefore, the current study highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.

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We used a 3-D coupled hydrodynamic–biogeochemical water quality model to investigate the effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system. The results highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.
We used a 3-D coupled hydrodynamic–biogeochemical water quality model to investigate the effects...
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