Drivers of Change to Seagrass Distributions and Communities on the Great Barrier Reef: literature review and gaps analysis

Collier, Catherine, and Waycott, Michelle (2009) Drivers of Change to Seagrass Distributions and Communities on the Great Barrier Reef: literature review and gaps analysis. Report. Reef and Rainforest Research Centre, Cairns, QLD, Australia.

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Seagrass meadows are important for a number of reasons: they act as the foundation of a diverse community with numerous ecological roles; primary production; habitat and food for herbivores (including turtles and dugongs); sediment stabilization; biochemical modification of the local environments; nutrient cycling and hydrodynamic modifiers. Seagrasses are known to be under threat from numerous impacts and also play a role as indicators of coastal ecosystem health (Orth et al. 2006). Recent analysis of Great Barrier Reef Ecosystem Health (Great Barrier Reef Marine Monitoring Program Workshop, September 2007) supports this in the GBR region.

The Great Barrier Reef (GBR) supports a high diversity of seagrass species across a broad range of habitat types. Seagrasses are not a taxonomically unified group but are an ecological group, which through pressures imposed by the marine environment have converged in general morphology, i.e. they have photosynthetic leaves and roots and rhizomes to anchor in the sediment and to grow via rhizome extension (Waycott et al. 2007). The high seagrass diversity in the GBR is associated with a broad range of seagrass forms and functions (Walker et al. 1999). These species respond to environmental drivers in different ways and with different thresholds for tolerance to disturbances. While there are some generalisations that can be drawn across this broad grouping, for many aspects being considered in relation to drivers of change, seagrass species differ. Every effort is made in this review to consider this diversity where there is enough available information to do so.

Seagrass monitoring and research has a rich history in the GBR region and yet there are many key areas of system understanding that are poorly understood. In this review we summarise the understanding of drivers in seagrass meadows. In a recent report (Coles et al. 2007), the status and trends of seagrass distribution in the GBR is described. The review here-in describes drivers of change in seagrass meadows and how these influence seagrass distributions, natural cycles in distribution and growth and drivers of disturbances to seagrass meadows. We seek to identify key processes that explain the distribution, variability and limitations to growth, enhancing our ability to recognise ecosystems under stress and when management actions may be required. The overall aim of this review is to highlight significant knowledge gaps that, if fulfilled, will improve our ability to manage seagrasses of the GBR.

To fully describe the processes limiting seagrass growth, an understanding of the manner in which seagrasses grow and survive throughout their life is useful (Figure 1). The life of a seagrass plant is typically dominated by the life-history stage of growth and meadow expansion following seed recruitment. During this stage of plant growth, individuals (from germination of a single seed) may persist for a very long time, forming large, clonal meadows. For all GBR seagrasses the extent of longevity and scale of individual growth remains unknown and requires future studies using genetic and ecological tools. Flowering and seed set provide propagules for seagrass habitats recovery following disturbance. Germination and establishment are rate limiting to habitat recovery and potentially influence the resilience of coastal marine communities. The causes of habitat loss are multitude and are form the basis of this review.

Item ID: 8275
Item Type: Report (Report)
ISBN: 978-1-921359-24-8
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Research Report No. 25

Date Deposited: 17 Feb 2010 04:27
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050205 Environmental Management @ 30%
06 BIOLOGICAL SCIENCES > 0607 Plant Biology > 060701 Phycology (incl Marine Grasses) @ 70%
SEO Codes: 96 ENVIRONMENT > 9603 Climate and Climate Change > 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts) @ 30%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960502 Ecosystem Assessment and Management of Antarctic and Sub-Antarctic Environments @ 35%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960506 Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments @ 35%
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