Size: 230 ha
Zone: Marine National Park (Green) Zone
GBRMPA Management Area: Cairns
Plan of Management Area: Cairns
Location: Sensitive (Low use).
- HIGH ANCHORAGE VALUE
- HIGH REEF WALKING VALUE
- HIGH REEF WALKING USE
- HIGH SHELL COLLECTING VALUE
- MODERATE DIVE VALUE
- HEAVY DIVE USE
- LIGHT RESEARCH USE
- RESEARCH MONITORED
- CORAL TROUT SURVEY
- COTS SURVEY
- CORAL BLEACHING
- TOURIST FACILITIES
- NAVIGATION AID
ANCHORAGEThere is shelter for boats on the NW side of the reef. Anchorage may be obtained in 11-15m over mud, NW of the lighthouse, with good holding ground (Australia Pilot). Lucas (1984) considered this a superb anchorage experiencing only minimal swell during heavy weather.
BLEACHINGYonge (1930) lists a number of instances of coral mortality observed during the 1928 Expedition. "Even during the poor day low tides in February the reef flat was covered with the whitened skeletons of dead corals".
COTSAccording to Woodhead (1971), this reef was undamaged by Crown-of-Thorns up to 1970. Pearson & Endean (1969) found 10-20 on the front of the reef in 1966. Ayling (1983) reported only 1 in 1983 and estimated coral cover to be very poor with extensive soft coral development. No Acanthaster were found during the 1985 survey (Bradbury, et al., Vol. 6, 1987).
CORAL TROUTSurveyed 2/83. Very low mean density - .2/.1 ha for Plectropomus leopardus & .3/.1 ha for P. maculatus (Ayling & Ayling, 1986). Ayling (1983) noted that it was possible that the low numbers of coral trout on the reef at this time were the result of high fishing levels.
FAUNA40 spp. of coral have been recorded (GBRC, 1977). Yonge (1930) noted that the blue coral, Heliopora, was common in the anchorage and that beche-de-mer were abundant. Gibbs (1978) studied the macrofauna of the intertidal sand flats. This paper discusses differences in the results of the various fauna surveys that have taken place since 1928. About 2/3 of the total sand flat fauna found on 6 low wooded islands in the area is found on this reef. About 1/5 of all species were taken only on this reef. Gibbs said this illustrated the scientific importance of Low Isles. The feeding and distribution of predatory gastropods here was studied by Reichelt & Kohn (1985).
MONITORINGUsed between June, 1977 and July, 1982 as a CSIRO coastal water quality monitoring station for measuring temperature, salinity, nitrate, & silicate. Samples were collected 1-2 times/month in 0-10 m of water (Castles, 1992). Bradbury, et al. (Vol. 6, 1987) established transects down the reef slope at one site on the reef front and one site on the back reef.
NAVIGATION AIDThe lighthouse is an 18 m white round tower with a red cupola. Two beacons stand close SE of the tower (Aust. Pilot).
REEF DESCRIPTIONThe reef on which Low & Woody islets lie is steep-to on all sides, except the NW (Australia Pilot). Roughly oval in shape with the long axis running SE to NW. The NW end was somewhat flattened and contained a central concavity. The SE end was sharply defined, the reef forming a submarine cliff which descended in a series of deep steps to the muddy bottom 13 fathoms below. On the NW, the slope was much more gradual. The mangrove swamp (Woody Island) extended along the E margin of the reef, while the sand cay (Low Isle) occupied the NE point, being separated by the shallow anchorage from a long shingle spit which ran almost due N. "Great flats of staghorn grew in the moat" (Yonge, 1930). An example of a platform reef in an intermediate stage of mangrove development (Flood & Orme, 1977). Flood & Frankel (1982) presented a recent description of morphological zonation of the reef. In addition to the cay, the surface features include shingle ramparts heaped up at the outer edge of the reef top, a boulder tract located toward the NW extremity of the reef flat, and the reef flat. The reef flat is subdivided into 4 units - sand flat, Thalamita flat, mangrove area, and moats. Large area dries (Cairns Shell Club 1982 Zoning Plan submission). Ayling (1983) recorded <5% hard coral cover and 50-90% soft coral cover and commented that the area examined was characterized by beds of soft coral. Classed an an inner-shelf reef. Nash (1985) noted that the reef emerged at low tide, particularly on the W & SW end, and that the coral rubble pavement in this area was of the type of habitat occupied by juvenile trochus. He surveyed the entire perimeter of the shallow intertidal zone and found "medium cover" by hard and soft corals. Sediment levels were described as "generally high everywhere" and substrate which was not covered by hard or soft corals mostly was carpeted with an encrusting zoanthid. In some areas this zoanthid covered nearly 100% of the substrate not occupied by corals. Zoanthid cover was low or absent only in those areas exposed at low tide. The most common corals were branching and tabular Acropora , small massive Porites, Goniastrea, other favids and Goniopora. Bradbury, et al, (Vol. 6, 1987) surveyed the reef perimeter on Nov. 27, 1985 and found high live coral cover (30-75%) along the E front of the reef, which decreased westwards to 10-30%. The gentle back slopes had little live coral (1-10%) which occurred only as small outcrops on the sandy slopes. Massive corals <1m in diameter were common on the S slopes, particularly the SE corner. Dead coral remained low on the front slopes (1-10%) and was absent or in patches of 1-10% on the back of the reef.
REMARKSThere is a radiotelephone at the lighthouse (Australia Pilot). Moorhouse (1933b) reported on water temperature in the anchorage and Brandon (1970) reported on average monthly sea surface temperatures for this reef. Yonge (1930) noted that the bottom immediately around Low Isles consisted of a thick, very fine grained black mud that "was found to contain hardly a single living beast".
REEF HISTORY1928-29 - Site of the base camp for the Great Barrier Reef Expedition. 1980 - Craik & Fallows (1980) found that 9% of a sample of 35 small boats leaving Port Douglas fished at Low Isles Reef. 1982 - The reef was said to provide very good diving. It also was said to be heavily used by reef walkers and underwater observers, and moderately used by researchers. On average 75 tourists/day were visiting the reef on the "Martin Cash" (E. Hegerl, notes from meeting of user groups, Oct., 1982).
SHELL COLLECTINGYonge (1930) noted the tiger cowrie was commoner on reefs which had been less "picked over" than Low Isles. The reef was highly valued as a shell collecting site prior to Zoning as it provided an "abundance of varied reef/cay species" (Cairns Shell Club 1982 Zoning Plan submission). In 1982 the reef was said to be moderately used by shell collectors. It was claimed that a valuable species of volute, Cymbiolacea wisemani, had been over-collected at this reef (Cairns Shell Club, pers. comm., Oct., 1982).
TROCHUSNash (1985) surveyed the reef in 1984. Trochus were not present in commercial densities.
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