Ecology of artificial reefs in the subtropics.

The application of artificial reefs (ARs) has a long history, and there is a wealth of information related to the design and performance of ARs in coastal and ocean waters worldwide. However, relatively fewer studies in the literature are focused on the response of benthic communities within the reef areas than those on fish attraction and fish production and on the settlement and colonization of epibiota on the AR structures, especially in the subtropics where seasonal differences and environmental conditions can be large. Recent advances in the understanding of the ecology of ARs in the subtropics are highlighted, with a focus on fish attraction versus fish production, development of epibiota on AR systems and responses of in situ benthic communities in the reef areas. Data are also presented on studies of trophic relationships in subtropical AR systems, and further research areas using analyses of biological traits, stable isotope signatures and fatty acid profiles in investigating the ecology of ARs are proposed.

Fatty acid profiles of benthic environment associated with artificial reefs in subtropical Hong Kong.

Artificial reefs can enhance habitat heterogeneity, especially in seabed degraded by bottom-dredging and trawling. However, the trophodynamics of such reef systems are not well understood. This study provided baseline data on trophic relationships in the benthic environment associated with artificial reefs in late spring and mid summer of subtropical Hong Kong, using fatty acid profiles as an indicator. Data from sediments collected at the reef base, materials from sediment traps deployed on top and bottom of the reefs, total particulate matter from the water column and oyster tissues from reef surface were subjected to principal component analysis. Results showed variations of fatty acid profiles in the total particulate matter, upper sediment trap and oyster tissue samples collected in the two samplings, indicating seasonal, trophodynamic changes within the reef system. The wastes produced by fish aggregating at the reefs can also contribute a source of biodeposits to the nearby benthic environment.

A study of the partitioning behavior of Irgarol-1051 and its transformation products.

Partitioning behavior of the antifouling booster biocide, Irgarol-1051 (2-methythio-4-tert-butylamino-6-cyclopropylamino-s-triazine), its production by-product, M3, and its environmental transformation products, M1 and M2, were studied. Octanol-water partition coefficients, log K(OW), and organic matter-water partition coefficients, log K(OC), of these s-triazines were measured by reversed-phase HPLC and a triphasic SPME equilibrium model, respectively. The average log K(OW) (+/-SD) of the four s-triazine species were: 4.39+/-0.07 (M3); 3.38+/-0.12 (Irgarol-1051); 2.92+/-0.12 (M2) and 2.54+/-0.11 (M1), while mean log K(OC) (+/-SD) of these species were: 2.47+/-0.03 (M3); 2.16+/-0.03 (Irgarol-1051); 1.97+/-0.03 (M2) and 1.79+/-0.04 (M1). These results were compared to reported physicochemical parameters of Irgarol-1051 in the literature. Partitioning behavior of these s-triazine species in the coastal environment revealed by their K(OW) and K(OC) were also discussed.

Identification of a new Irgarol-1051 related s-triazine species in coastal waters.

A previously unknown s-triazine species present in commercially available Irgarol-1051, a booster biocide additive in copper-based antifouling paints for the replacement of organotin-based antifoulants, has been identified in the coastal aquatic environment. After careful isolation, purification and characterization by high resolution MS-MS and (1)H NMR, the molecular structure of that unknown species is found to be N,N'-di-tert-butyl-6-methylthiol-s-triazine-2,4-diamine (designated as M3). Levels of Irgarol-1051, its major degradation product (M1) and the newly identified M3 in the coastal waters of Hong Kong, one of the world's busiest ports located in the southern coast of China, were monitored by SPME-GC-MS and SPME-GC-FID. Water samples from five locations within Hong Kong waters were analysed and the levels of Irgarol-1051, M1 and M3 were found to be 0.1-1.6 microg l(-1), 36.8-259.0 microg l(-1) and 0.03-0.39 microg l(-1), respectively. Our results indicate that M3 is relatively stable against photo- and bio-degradation and may pose considerable risk to primary producer communities in the coastal marine environment.