Comparison of the effectiveness of four organic chemoattractants towards zoospores of Ulva pertusa and macrofouling.

Algal spores respond to many environmental variables, especially to chemical "cues". This chemotactic response can be utilized to attract spores, thereby colonization of a new substrata is possible to be influenced. In this attempt, four chemoattractant candidates were screened against spores of Ulva pertusa to reveal their efficiencies. Attachment and subsequent germination of Ulva spores were effectively influenced by these chemoattractant candidates. In particular 100 microg cm2 of D-glucose coating was found to enhance spore attachment by > 150%. Furthermore, field investigations carried out with test panels, clearly indicate the chemoattractive properties of test coatings. In recent years, various anthropogenic activities and natural hazards cause detrimental impacts on the benthic algae and other fishery resources. Artificial reefs have been laid on many coastal regions to increase or restore marine resources. Chemoattractant coatings can be applied on artificial surfaces to increase the colonization of benthic forms. It also can be used in the mariculture devices. Influence of chemoattractants on Ulva spores and fouling biomass estimated on test panels are discussed.

Evaluation of antifouling activity of eight commercially available organic chemicals against the early foulers marine bacteria and Ulva spores.

Environmental impacts caused by tin and copper based commercial antifouling (AF) paints were proved to be detrimental to aquatic ecosystems. Therefore, a search of environmental friendly AF compounds to be used in marine paint to protect the surface of maritime developmental structures from the unwanted biofouling is a burning issue of the present time. Commercially available eight organic chemicals--allyl isothiocyanate, beta-myrecene, cis-3-hexenyl acetate, citral, ethyl heptanoate, eugenol, methyl caproate, and octyl alcohol were evaluated forAF activities using both laboratory and field assays. The test chemicals were found to repel the target motile marine bacteria--Alteromonas marina, Bacillus atrophaeus, Roseobactergallaeciensis and Shewanella oneidensis and motile spores of the green alga, Ulva pertusa. The bacterial and Ulva spore repulsion activities of the test chemicals were measured by chemotaxis and agar diffusion methods respectively interestingly these test chemicals were less toxic to the test fouling species. The toxicity of the test chemicals was measured by using antibiotic assay disks against the bacteria and motility test against Ulva spores. Moreover, in field assay, all test chemicals showed a perfect performance ofAF activity showing no fouling during the experimental period of one year Such results and commercial as well as technical feasibility of the test chemicals firmly showed the possibility of using as alternatives of the existing toxic AF agents.

Biofouling attractants from a brown marine alga Ecklonia cava.

In recent years, industrial pollutants and the mountain forest fire ashes released into seawater cause damage to the marine environment, mainly it reduces the algal productivity in the inter tidal region. To get recover from the stress due to pollutants and to increase the growth and development of biofouling algae (benthic organisms), Ecklonia cava extract was investigated for its biofouling attracting efficiency. Bioactive guided fractions of E. cava extract derived from column chromatography were tested against spore attachment of a fouling alga, Ulva pertusa. Fraction B showed increased spore attachment rate with a maximum of 92 +/- 5%. This fraction was further analysed on HPLC, GC-Mass and NMR, deduced as pentadecanoic acid.

Influence of five organic antifouling candidates on spore attachment and germination of a fouling alga Ulva pertusa.

Screening of test chemicals or formulations for antifouling (AF) activity is important to get first hand information on their nontoxic repelling activities. Especially spores of a fouling alga, Ulva pertusa were used in this study to test the AF efficiency of five organic chemicals. Coatings made with 100 microg cm2 of citral and eugenol significantly inhibited the spore attachment. A low concentration (1 microg cm2) of solanesol exhibited effective AF activity against spore attachment. Spore germination was sensitive to different AF candidates screened in this study. Based on the attachment and germination response of Ulva pertusa spores, AF efficiency of five organic AF candidates is discussed.

Fouling coverage of a green tide alga, Ulva pertusa on some antifouling test surfaces exposed to Ayagin harbor waters, east coast of South Korea.

Toxic antifouling chemicals released into the seawaters leads to marine environmental degradation. In order to identify a nontoxic antifoulant, an assessment of antifouling (AF) efficacy of some AF candidates was made at Ayagin harbor, east coast of South Korea. In this static panel study conducted during October 2000-March 2001, some commercial antifoulants, seaweed and seagrass extracts were screened. On panel surfaces coated with a seaweed extract, Ishige okamurae exhibited effective AF activity. Ulva pertusa was encountered as a 'monospecific' fouler with fairly high fouling coverage on many of the test panel surfaces. In recent years the increased influx of inorganic pollutants in the coastal waters causes exorbitant growth of fouling marine algae found all along the Korean peninsula. Especially, a cosmopolitan ship fouling alga U. pertusa occur with high abundance. It was largely suggested that the proposed international ban on the toxic antifoulant tributyltin (TBT) had significant effect on the 'green tide' phenomenon occurring in different parts of the world. However, it appears that Korean scenario of 'green tide' is a localized. Antifouling efficacy of some AF coatings and fouling coverage of a green tide alga, U. pertusa are discussed.