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This dataset contains annual and seasonal values of the benthic light (bPAR index) for water quality on the Great Barrier
Reef as calculated for each NRM Region (Cape York, Wet Tropics, Dry Tropics, Fitzroy and Mary-Burnett) and waterbody (Closed
Coastal, Open Coastal, Midshelf and Offshore) for each water year between 2003 and 2019, as reported in NESP TWQ Project
5.3. Code used to produce these values is also available through eAtlas, as is the daily bPAR data.
The amount of light available for photosynthesis (photosynthetically active radiation, or PAR) is an important determinant
of ecosystem health. PAR reaching the bottom of the water column is known as benthic PAR (bPAR). Where there is sufficient
light reaching the bottom, seagrasses and corals may thrive. bPAR varies seasonally as a function of surface PAR, but also
varies function of both water depth and water quality.
This dataset contains the annual and seasonal values of the bPAR index developed through NESP TWQ Project 5.3.
Methods:
Daily benthic photosynthetically active radiation (bPAR) derived from remote sensing ocean colour observations is used to
derive an index for water quality in the Great Barrier Reef (GBR). Daily bPAR observations at a nominal 1km2 resolution
are used to calculate a cumulative seasonal and annual light stress experienced by benthic photosynthesising organisms at
each pixel. This light stress is aggregated over each NRM region and waterbody of the GBR and scaled to produce an index
with a value between 0 (no light penetration to benthic habitats) and 1 (excellent light penetration to benthic habitats).
Boundaries of NRM Regions and water bodies as used here are available as part of the “code” dataset also associated with
NESP TWQ Project 5.3 in eAtlas. Spatial information (geographic outlines of GBR NRM regions and waterbodies) is provided
as a SpatialPolygons variable “Polys” in the R data file Polys.rda
The full method used to calculate the index is described in a manuscript pending review:
Canto, M.M., Fabricius, K.E., Logan, M., Lewis, S., McKinna, L.I., and Robson, B.J. (submitted). A benthic light index
of water quality in the Great Barrier Reef, Australia.
Format:
This dataset consists of a comma separated variable (CSV) file containing the annual and seasonal values of the bPAR index
for each water year from 2003 through 2019. Columns contain:
A) Water Year. Each water year is defined as the period from 1 October in the preceding calendar year through to 30 September
of the year in question, so for example the 2003 water year runs from 1 October 2002 through to 30 September 2003, inclusive.
B) NRM Region. Name of NRM management region (Cape York, Wet Tropics, Dry Tropics, Fitzroy or Burnett-Mary).
C) Water Body. Name of water body (Closed Coastal, Open Coastal, Midshelf, or Offshore).
D) Annual bPAR index. Value of the bPAR index calculated over a full water year for the NRM region and waterbody in question.
Values range between 0 (very poor light penetration to benthic habitats) to 1 (excellent light penetration to benthic habitats).
E) Wet season bPAR index. Value of the bPAR index calculated over the wet season of the water year in question (i.e. 1
October of the preceding calendar year to 30 April).
F) Dry season bPAR index. Value of the bPAR index calculated over the dry season of the water year in question (i.e. 1
May to 30 September).
References:
Canto, M.M., Fabricius, K.E., Logan, M., Lewis, S., McKinna, L.I., and Robson, B.J. (submitted). A benthic light index
of water quality in the Great Barrier Reef, Australia.
Data Location:
This dataset is filed in the eAtlas enduring data repository at: data\nesp5\5.3_Benthic-light
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