Studies on prevention of fouling by barnacles

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1. Reproductive condition for Balanus amphitrite.It became possible to get hatched nauplii every day under the following rearing conditions : Salinity is about 27, water temperature between 21 to 25 C, and natural light condition. Exchange of seawater is needed once a week at least. It is essential to dry up of brood adults for several hours a day. More than eight hundred of hatched Artemia should be given for a barnacle in a day.2. Methods of bioassay using B. amphitrite cyprids.Hatched barnacle nauplii could be metamorphosed to cyprids by Chaetoceros calcitrans as food in 22 to 25 C. The cyprids for bioassay are those kept in 5 C for 2 to 10 days after the metamorphose. Assay vessel is used polystyrene or glass petri dishes. Inside the vessels of test lot are coated with solubilized test substance, and let solvent volatilize. Twenty cyprids and 5 ml seawater are introduced to the vessel. The seawater is that the salinity is above 20, filtered with glass filter (GF/C) and UV radiated. The vessels are incubated for 3 to 4 days under continuous dark and 25 C. Number of attached cyprid and juvenile are counted at the end of incubation.3. Screening of various substances as antifoulants(1) Prevention of fouling by applying antifoulant to the substratum.Among the various substances tested, fatty acid from porcine liver (FAPL) and calcium alginate were noticed to have high antifouling activity without killing the larvae. Since the latter inhibited settlement of cyprids more than 80 %, the antifouling activity in the sea is now testing in Mutsu Bay.(2) Prevention of fouling by dissolving antifoulant to the sea.Carbonic acid was tested instead of chlorine used as dissolving antifoulant before. By aerating carbonic acid gas into seawater, pH of the seawater during test period decreased below 6.6, as a result, settlement of cyprids was perfectly inhibited for at least four days.