Individual study: Use of an anti-fouling paint reduces fouling organism growth within coral-rearing nurseries off Eilat, Israel
Shafir S., Abady S. & Rinkevich B. (2008) Improved sustainable maintenance for mid-water coral nursery by the application of an anti-fouling agent. Journal Experimental Marine Biology and Ecology, 368, 124-128
Small coral fragments that would die if directly transplanted during reef rehabilitation can be nursery-reared to a size suitable for transplanting. At Eilat (Red Sea Coast, Israel) some coral nurseries are located adjacent to fish farms, where although the nutrient-enriched water promoted coral growth, fouling was a problem, thus incurring increased labour costs. Unwanted organisms colonising the plastic pins on which the corals grew and the nursery frame and nets, had to be regularly removed; maintenance time for 100 coral colonies was around 1 h/month, increasing during spring algal blooms to 4 h/month. Corals and their pins also had to be cleaned before transplantation (c. 20 colonies/h). An antifouling paint was applied in an attempt to reduce fouling organisms during the crucial phase of coral development from nubbins and small fragments to sizes suitable for transplanting.
An antifouling paint employed by the fish farming industry to reduce fouling on nets (Steen-Hansen, Aqua-guard M250; active ingredient cuprous oxide) was trialled. Two coats of paint were applied by dipping the plastic coral-rearing nursery frames and/or pins into the paint. Four treatments were tested:
A - painting frames and pins before attaching the coral fragments to the pins (coral in contact with paint);
B - as for 'A', but scraping the paint off the pinheads (coral < 2 cm distant from paint);
C - painting frames only (coral > 2 cm distant from the paint);
D - controls (no paint applied).
Fragments of cluster coral Stylophora pistillata were glued to the pins and placed into PVC- framed plastic nets, 60 fragments per frame. Experimental trays were left uncleaned during the experiment but were subject to natural cleaning by fish and invertebrates. Each coral fragment on a pin was monitored and recorded as detached, dead, or partly damaged (bleached) at day 0, 31, 73, 106 and 126. At day 126 cleaning was undertaken.
After four months (126 days) the following responses were recorded:
Treatment A - 58% of coral colonies detached, 31% dead, 11% alive;
Treatment B - 8% of colonies detached, 29% dead, 62% alive;
Treatments C and D - responses were similar; 13% and 14% detachment, 4% and 1% mortality and 83% and 85% survivorship, respectively.
In terms of the final cleaning, corals under treatments 'A' and 'B' needed no cleaning other than quickly washing the trays of debris (shortening cleaning procedures by 90%). The pin tips for those under treatment 'C' needed cleaning (10 tips cleaned in about 2 min); the trays again quickly washed. The controls took about 5 min to clean 10 tips and about 15 min to remove fouling organisms from the tray.
The experiment showed that paint application by Treatment C reduced coral and nursery structure fouling to a point where maintenance was minimal and cleaning time of coral before transplanting was much reduced, whilst incurring very low (inisignificant compared to controls) coral detachment and mortality.
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