Macroalgae parts

Owing to the costs of defenses, natural selection will optimize defenses. There are various aspects in this optimization, including defense allocation with respect to temporal variation in grazing pressure and within-plant defense allocation with respect to grazing risk and the value of different plant parts (reviewed in Stamp 2003). Here we will focus on both the induced defenses and within-plant allocation of defenses, because these aspects have been widely studied in macroalgae. 

The criteria for inclusion of studies in this summary have been as follows (1) use of marine macroalgae as model organisms, and (2) explicit tests of any of the described defense theories (ODM, CNBM, or GDBM) either through observations or through manipulative experiments. We have not included studies that only measure variation in secondary metabolites in different seaweed parts or after different treatments, unless they have specifically mentioned any of the models or hypotheses derived from the models in the introductory part of the paper. Therefore, the summary presented here does not represent an exhaustive review of all data from algal studies that are relevant for defense theories and algal chemical defenses. 

MAAs can have an inhibitory effect on macroalgae. MAAs added to culture medium retard the growth of Porphyra yezoensis.19 The response is additive the higher the concentration of MAAs, the greater the inhibition of growth. The decline in growth is attributed in part to MAA interference with chloroplast metabolism. Whether this is a direct inhibitory effect or interference with feedback regulatory mechanisms is not yet known. 

The eastern Baltic Proper coast consists mainly of highly mobile sandy substrates. Hard bottom, suitable for macroalgae colonization, is very rare in its southern parts. Further north, off the coast of Latvia and Estonia, hard bottom becomes available again and macrophytes thrive there. 

Novel metabolites of mixed biogenesis are more likely to contain novel carbon skeletons than are the better-explored isoprenoid secondary metabolites. Therefore, hybrid metabolites from macroalgae seem to become front-runners for exciting natural product discovery. Uncovering novel skeletons for new scaffolds remains an integral part of drug discovery. 

The detoxifying effect of different seaweeds in a Wistar rat model indicates that the presence of sulfated polysaccharides is crucial in the liver protecting effect of macroalgae (Costa et ah, 2010). Other studies have evidenced the protective effect of seaweeds against liver toxicity induced by galactosamine in a rat model, concluding that this protecting effect is partly mediated by fucoidan, a sulfated polysaccharide from the brown seaweed Laminaria (Kawano et ah, 2007). 

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