22 - Natural marine products with antifouling activities

Abstract

Marine organisms have usually been viewed as sources of compounds with interesting and useful biological activities, in particular with the ability to inhibit attachment, settlement, or growth of various marine organisms, i.e. with antifouling (AF) activity. Over hundreds of millions of years, marine organisms evolved in an environment where strong competition for space and epibiosis pressure selected for the presence of AF mechanisms, of which one that seems to be particularly widespread is the use of natural marine products with AF activity. In this chapter, we pursue the objective of reviewing, although not exhaustively, the recent (last ten years) research on marine natural AF products. We preferred rather to focus on interesting cases that would then allow the reader to understand the main trends that emerge from this field, and indicate future and promising directions of research. Among all marine organisms, sponges seem to constitute the most prolific source of novel antifoulants, most likely due to their association with single-cell symbionts. Marine macroalgae are also prominent producers of antifoulants, and within this group, red seaweeds seem particularly active. Although the tropical marine organisms are usually seen as better defended than their extra-tropical counterparts, current data does not support a latitudinal pattern in AF defences. However, the production of AF compounds has been demonstrated to vary spatially (i.e., geographically) and temporally (i.e., seasonally), in the limited number of cases that have been investigated. Similarly, only a few studies have assessed the activity spectrum of natural antifoulants in field experiments. The means to produce natural marine products at a large scale appears possible in a number of cases, either by mass cultivation or by laboratory synthesis. Nevertheless, there are significant regulatory hurdles that must be overcome before any new antifoulant reaches the market.