Low Isles Quiksilver-Port Douglas Latitude: 14.533.76 E Longitude: 16.22.99 S Date: 3-4-4 SITE DESCRIPTION Low Isles is a mostly sheltered coral cay situated 15 kilometers north-east of Port Douglas. The mangrove island nearby provides a buffer from storms, and it is protected within the Great Barrier Reef Marine Park as a Marine National Park zone. The tourist industry, including boating, diving, and snorkelling, is the main source of impact. Low Isles reef flat is dominated by 15 species of soft corals. The visibility at Low Isles is greatly determined by the weather and the water is often full of sediment. Although 2 surveys were done here they have not been combined because one was in the lagoon and the habitats differed. An invertebrate and impact survey has only been done for site 1.
SUBSTRATE SURVEY Site 1: The substrate consists mainly of soft corals (4%), followed by several hard coral forms (figure 1). Soft corals can better tolerate less than ideal conditions, and site 1, inside the lagoon, is dominated by them. Rock constitutes 14.4% of the substrate and there was also silt (SI) found, in a relatively great abundance (11% of the substrate reported). Percent cover + - SE 45 4 35 3 25 2 15 1 5 Percent Cover of Substrate for Low Isles, 4m depth, site 1, 3-4-4 HC SC RKC NIA SP RC RB SD SI OT OT SI SD RB RCCA RCTA RC SPE SP NIA RKCTA RKCNIA RKC SCB SCZ SCL SC HCB HCP HCE HCM HCF HCBR HC Figure 1: Soft corals are the principal substrate leathery (SCL) forms comprising almost half of all soft coral present
Site 2: In addition to Site 1, a second site was selected that was located on the north-west side of Low Isles. The substrate here was dominated by hard corals and silt, with relatively small amounts of soft corals observed (figure 2). Site 2 differs greatly from Site 1, and is included here to demonstrate the dissimilarity between sites, and for reference in future surveys at Low Isles. Percent cover + - SE 5 45 4 35 3 25 2 15 1 5 Percent Cover of Substrate for Low Isles 5m depth, site 2, 4-4-4 HC SC RKC NIA SP RC RB SD SI OT OT SI SD RB RCCA RCTA RC SPE SP NIA RKCTA RKCNIA RKC SCB SCZ SCL SC HCB HCP HCE HCM HCF HCBR HC Figure 2: 45% of the substrate was composed of hard corals and 1% of soft corals. There is 28% of silt
Substrate monitoring 22-24: Low Isles was surveyed once in 22, and again in 24, but not in 23. The differences observed between 22 and 24 are mainly due to the absence of nutrient indicator algae. The more permanent substrates underneath were exposed, increasing the number of both hard and soft corals, and rock, recorded. The incidence of silt also increased, more than doubling over the two years (figure 2). Mean percent cover of benthic communities at Low Isles, for 22 and 24 Percent cover +/- SE 45 4 35 3 25 2 15 1 5 21-4-2 4-4-4 HC SC RKC NIA SP RC RB SD SI OT Substrate type Figure 2: The differences observed between 22 and 24 are due to absence of nutrient indicator algae (NIA), although a higher amount of silt (SI) was recorded.
INVERTEBRATES SURVEY The invertebrates recorded consisted entirely of Giant Clams with a mean abundance of 1 per 1m 2. There were also observations of Drupella (figure 3). A turtle was sighted. 1.2 Mean Abundance of Invertebrates at Low Isles 4m depth, site 1, 4-4-4 Mean Abundance +-SE 1.8.6.4.2 Banded coral shrimp Diadema Pencil urchin T. ananas S. chloronotus H. nobilis H. fuscopunctata S. variegatus Crown of Thorns Giant clam Tripneustes Triton shell Lobster Trochus Drupella Figure 3: There were mainly Giant Clams and a few Drupella sp. at Low Isles
IMPACTS SURVEY SOverall impacts on Low Isles were minimal. The majority of impacts observed were general scarring (figure 4). There was no bleaching observed at the site. One Drupella sp. scar was recorded, affecting a small piece of branching, hard coral (HCBR). Mean Abundance per 1 m2 1.6 1.4 1.2 1.8.6.4.2 Boat/Anchor damage Mean Abundance of Impacts at Low Isles 4m depth, site 1, 3-4-4 Dynamite damage Other damage Trash: Fish nets Trash: General Drupella scars Crown of Thorns scars Other scars Figure 4: The main impacts reported are caused by minimal scarring from unknown origin.