Toxigenic effects of sponges and benthic diatoms on marine invertebrates and their possible biotechnological applications.

Secondary metabolites play important physiological roles being bioactive as defences against other organisms, or attractive signals used for various purposes, including reproduction. Their production and the emission in the environment may be viewed as an adaptive feature subjected to evolutionary selection. They were demonstrated to be useful for applications in various biotechnological fields, such as pharmaceutical, nutraceutical and cosmeceutical. Sponges and microalgae, including diatoms, are the most promising sources of bioactive compounds from the sea. We aimed at detecting the ecotoxicological effects of crude extracts and fractions obtained from three marine sponges, Geodia cydonium, Haliclona (Halichoclona) vansoesti and Agelas oroides and two benthic diatoms, Nanofrustulum shiloi and Cylindrotheca closterium on model marine organisms. We tested their effects on the Mediterranean purple sea urchin, Paracentrotus lividus, and on two diatoms, Phaeodactylum tricornutum and Cylindrotheca closterium, chosen because they are considered standard indicators for assessment of ecological impacts. Our results showed that extracts and fractions from both sponges and diatoms may be harmful for model invertebrates. However, eggs appeared "protected" from sponge allelochemicals when still unfertilized. The majority of sponge fractions exhibited noticeable impacts during the post-fertilization treatments. In contrast, fractions from diatoms notably increased the rate of malformations compared to the control, both in pre- and post-fertilization treatments.