Surveys
of sessile benthic communities
using the video technique
Standard
operational procedure 2
SAMPLING
DESIGN
Reef benthos
communities are surveyed annually within six sectors of the
Great Barrier Reef (Cooktown/Lizard Island, Cairns,
Townsville, Whitsunday, Swain and Capricorn Bunker sectors).
In each of these sectors (with the exception of the Capricorn
Bunker sector) three shelf positions (inner, mid and outer)
have been identified. Three reefs are nested within each of
these shelf position/sector combinations.
In the Capricorn
Bunker sector, only outer shelf reefs are represented, with
four reefs being surveyed. Shelf position is determined by the
position of the reef relative to the coast and continental
slope, with inner shelf reefs closest to the coast.A single
habitat is surveyed on each reef, typically situated on the
north-east flank of the reef. It is defined as the first
stretch of continuous reef with a slope less than vertical,
going in a clockwise direction from the back reef zone towards
the reef front.
The selection of a
common habitat allows comparisons to be made between reefs,
both within and between sectors. Within this habitat three
sites are selected, each containing five, permanently marked,
50 metre long transects, lying roughly parallel to the reef
crest. Further details of the design can be found in Oliver et
al. (1995).
Transects are
set-up along the reef slope (at a depth between 6 and 9 metres).
Each transect is marked at the beginning and at the end with a
star-picket and at 10 metre intervals with steel
reinforcing rods (10 mm diameter.). A tape stretched between
the star-pickets and rods marks the centre line of each
transect. Each star-picket is labelled with an aluminium tag
(identifying the transects as belonging to AIMS project 221).
The GPS position of the star-picket at the beginning of the
first transect of each site is recorded in a database. This
star-picket is also marked with a subsurface buoy to aid in
locating the site.
Fish abundance
surveys and benthic surveys are conducted along each transect.
The benthic surveys are conducted approximately 50 cm from the
tape, horizontal to the substrate on the upper slope side. The
video camera is kept a consistent distance from the substrate
(25 cm). The resulting belt transect to be analysed is
approximately 25 cm by 50 m.
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