SEAGRASSES SURVEY IN NORTHERN REEFS
Mapping of seagrass distribution in the Reef's far northern section
is the first major project of CRC Seagrass Systems of the GBR (1.4.2)
being undertaken by the Department of Primary Industries, Northern Fisheries
Research Centre. Cairns-based CRC researcher, Len McKenzie reports:
Seagrass mapping surveys have been conducted to identify species composition,
estimate above ground biomass and algal cover, and record sediment types
and other benthic animals.
The first survey of deep water seagrasses growing below 15 meters was
conducted last November. Our team sampled 151 exposed sites, far from
reefs or mainland, 120 proximal sites, close to reefs, and 59 random spot
sites. A video record was made at each site with divers inspecting the
deeper areas to verify video recordings. Another survey was conducted
from Cape Tribulation to Cape Weymouth in December to record reef top
seagrass habitats. More than 70 reef platforms were surveyed using manta
tows and some spot site diving.
Results to date indicate extensive deep water seagrass meadows found
south of Princess Charlotte Bay, with only small meadows north to Cape
Weymouth. Seagrasses were uncommon on reef platforms along the outer barrier
but were present on most inshore and mid shelf reef platforms.
Data from both surveys are being entered onto a database and analysed.
A simple probability model will be developed to estimate the area of different
deep water seagrass habitat types and the likelihood of seagrass habitats
on reef platforms in the northern region.
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