Biogeochemical processes in permeable estuarine sediments following benthic community change: implications for system dynamics & Lyngbya majuscula blooms in Deception Bay, Queensland

Hanington, Peter (2015). Biogeochemical processes in permeable estuarine sediments following benthic community change: implications for system dynamics & Lyngbya majuscula blooms in Deception Bay, Queensland PhD Thesis, School of Geography, Planning and Environmental Management, The University of Queensland. doi:10.14264/uql.2015.779

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Author Hanington, Peter
Thesis Title Biogeochemical processes in permeable estuarine sediments following benthic community change: implications for system dynamics & Lyngbya majuscula blooms in Deception Bay, Queensland
Formatted title
Biogeochemical processes in permeable estuarine sediments following benthic community change: implications for system dynamics & Lyngbya majuscula blooms in Deception Bay, Queensland
School, Centre or Institute School of Geography, Planning and Environmental Management
Institution The University of Queensland
DOI 10.14264/uql.2015.779
Publication date 2015-07-17
Thesis type PhD Thesis
Supervisor Ron Johnstone
Tony Chiffings
Total pages 121
Language eng
Subjects 039901 Environmental Chemistry (incl. Atmospheric Chemistry)
050102 Ecosystem Function
060701 Phycology (incl. Marine Grasses)
Formatted abstract
Estuaries are productive and dynamic ecosystems that provide a wide range of environmental services to human society, many of which contribute to people’s livelihoods and wellbeing. However, many of these coastal ecosystems have become degraded by the impacts of human activity. Such degradation is often manifested in changes to an ecosystem’s structure and function. Such changes impact on the resilience of these ecosystems to recover from natural disasters and maintain essential services that human and ecological communities rely upon.

In shallow-water estuarine ecosystems, sediment-based processes often play a significant role in ecosystem function, such as the biogeochemical cycling of carbon and nutrients. This thesis examines the importance of benthic community composition on key biogeochemical processes that underpin local phenomena such as blooms of the toxic cyanobacterium Lyngbya majuscula and materials cycling at ecosystem-wide scales.

The research presented here shows that changes in benthic community composition have implications for system-wide functions such as biogeochemical cycling. In Deception Bay, 100 % of the seagrass community dominated by Syringodium isoetifolium was lost after a major flood event in January 2011. The loss of S. isoetifolium from Deception Bay was shown to fundamentally change the structure and function of the seagrass meadow from a net heterotrophic seagrass dominated benthic community to a net autotrophic seagrass-microphytobenthic community. Such a change in function has implications for system-wide biogeochemical budgets.

This study has quantified a benthic release of Fe(II) from sediments sampled from northern Deception Bay. To our knowledge, this study represents the first documented benthic release of Fe(II) from permeable sandy sediments of a shallow subtropical embayment. The results suggest that sandy sediments that are relatively low in organic carbon are capable of supplying bioavailable Fe at levels significant for the growth of benthic organisms. The results of this research show that the post-flood sediments of northern Deception Bay are capable of supplying >1700 % of the daily Fe demands and up to 10.6 % of daily P requirements for the growth of L. majuscula blooms. This result suggests that the growth of L. majuscula blooms in Deception Bay is likely to be P limited and that future management actions that are targeted towards reducing L. majuscula blooms in Moreton Bay need to include a strategy for reducing P loads to the Bay.
Keyword Benthic processes
Lyngbya majuscula
Biogeochemistry
Iron and phosphorus fluxes
Seagrass
Estuarine sediments
Deception Bay

Document type: Thesis
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Created: Wed, 15 Jul 2015, 13:43:33 EST by Peter Hanington on behalf of School of Geography, Planning & Env Management