The effect of ambient solar ultraviolet radiation (UVR) was assessed on a shallow water tropical fouling community during the succession of macrobenthic species on artificial substrates. The communities developing under three radiation treatments (PAR+UV-A+UV-B = 280 - 700 nm; PAR+UV-A = 320 - 700 nm and PAR = 400 – 700 nm) were monitored over a period of 14 weeks. Seven species of algae and 8 species of invertebrates colonized the experimental tiles. During the first 8 weeks of experiments there were no differences among treatments in diversity, percentage of cover of species and biomass of colonizers. After 56 days however, communities exposed to UVR had lower species richness than communities exposed to PAR. Treatments differed significantly (ANOVA, P<0.05) in species diversity (after 79 days) and in biomass of community (after 56 and 79 days), but the total percentage of species cover was not significantly different through the experiment. Adults and juveniles of the polychaete Hydroides elegans and the barnacle Balanus amphitrite, juveniles of the clams Perna viridis and Modiolus comptus, the algae Enteromorpha sp., Ectocarpus sp. and Cladophora sp. were responsible for the dissimilarity between communities developed at different UVR treatments. Algae had more high percentage of cover under the full sunlight spectrum, whereas the polychaete, the barnacle and clams were dominant in the no UVR treatment. An out-door experiment revealed that UVR inhibited the settlement and decreased post-settlement survival of H. elegans. We conclude that UVR affects the composition of shallow water biofouling communities in tropical waters as well as settlement and mortality of single species. More information about the project
Some marine algae and animals have natural defence against micro- and macroepibionts. It is known that this chemical defence is based on excudation of metabolites which act as toxic substances and biocides. Until recently no naturally produced repellents that act as natural antifouling agents were known. Our studies permit to state that some macroalgae and animals use repellents to defend themselves against epibionts. However, this defence is probably species-specific. Another part of our studies is to search for universal natural and artificial means to protect man-made structures against biofouling. Our experimental studies have allowed us to find some synthetic repellents and antiadhesives which suppressed the settlement and attachment both micro- and macroorganisms and simultaneously were non-toxic for these and other marine organisms. Thus, these substances have a good perspective for industrial ecologically safe defence against biofouling. The co-operation in studies mentioned above is proposed.
Antilarval and antimicrobial
activity of waterborne metabolites of the sponge Callyspongia (Euplacella)
The results of laboratory experiments of antifouling activity of the sponge Callyspongia (Euplacella) pulvinata are linked to field study. In the laboratory, conditioned seawater (CSW) of the sponge strongly inhibited the growth of the benthic diatom Nitzschia paleaceae and the settlement of the tubeworm Hydroides elegans, but had no effect on the growth of 9 bacterial strains isolated from natural biofilms. CSW diluted 5x still exhibited antilarval and antidiatom activities. In field experiments, sponge specimens were placed within 13 and 50 cm of Petri dishes that were serving as attachment substrates for micro- and macrofouling organisms. After 7 d, diatom attachment on dishes placed in close vicinity to the sponge was inhibited. Bacterial densities on the experimental dishes did not differ significantly from the control dishes. Microfouling communities, which developed on experimental and control dishes in the field had similar effects on the settlement of H. elegans under laboratory conditions. A community of 5 species of green algae, 2 species of brown algae, 2 species of red algae and 5 species of invertebrates became established after 28 d. We found strong negative effects of the presence of sponges and the position of the plate on the total percentage of cover, Shannon-Wiener diversity, as well as on the species richness of the macrofouling communities. In the experimental dishes, the percentage of coverage of macroalgae (Ulva sp., Enteromorpha sp., Ectocarpus sp., unidentified brown algae) and invertebrates (Hydroides elegans, Obelia sp.) decreased. ANOSIM and SIMPER analysis demonstrated that the composition of macrofoulers on the dishes were positively affected both by the presence of a sponge and with decreasing distance from it. Our results suggest that waterborne compounds of the sponge inhibit settlement of micro- and macrofoulers not only on its own surface but also on non-living surfaces nearby.
The recovery of microbial communities removed from hard substrates was studied in the laboratory on microepiphyton in the White Sea, in St.Petersburg, and in Karelia. The removal of these communities from hard substrates destroyed their spatial structure. Recovery was allowed to proceed from the suspension on a horizontal substrate in stagnant water at low temperature. The sequence of colonization in the lab was the same as that in the field. Laboratory recovery was complete in 12-24 h and did not depend on the age of the natural community. From the comparison between lab and field data on such mechanical distubance, a pattern of recovery, termed "self-assembly", is proposed.