Biophysical Survey of Mafia Island Marine Reserves

area, the most extensive continuous reef site identified at NIMR. The north-west tip of
the reef consists of extensive Thalassodendron cilatum seagrass beds but changes into a
soft coral dominated reef approximately 300m along the reef edge to the east. The rocky
reef section extends down to a depth of 10m. Sand substrates are found at the bottom of
the reef edge, which then very gradually slopes downwards reaching a maximum depth of
about 20m. The site is frequently subject to strong currents and high turbidity. In places,
the shallow crest and reef flat areas support branching Acropora communities, however,
at other locations, such as site 3, the shallow areas are dominated by macroalgae and
seagrass.
This section of reef is formed of coral rock overlaid by loose sand and rubble
substrates. It supports a diverse and extensive soft coral community (27.78% +/- SE
4.67), as well as sponge (7.33% +/-SE 1.04) and scleractinian coral species (7.17% +/-
SE 2.22) (Figure 6). The scleractinian coral consists primarily of massive growth forms
(6.17% +/- SE 2.30) with low levels of encrusting and branching forms (Figure 7).
Average percent cover (+/- SE)
35
30
25
20
15
10
5
0
All hard coral
Dead Coral
Bleached Coral
Soft Coral
Sponge
Other Benthic Organisms
Seagrass
Macroalgae
Turf algae on rubble
Turf algae on coral rock
Crustose Coralline Algae
Nutrient Indicator Algae
Rock
Figure 6. Average percent cover (+/- SE) by benthic type across all transects completed at site 3, NIMR.
Rubble
Sand
Silt
Other