SETTLEMENT AND SURVIVAL OF <em>POLYSIPHONIA LANOSA</em> (CERAMIALES) SPORES ON <em>ASCOPHYLLUM NODOSUM</em> AND <em>FUCUS VESICULOSUS</em> (FUCALES).

The settlement patterns of spores of Polysiphonia lanosa (L.) tandy on Ascophyllum nodosum (L.) Le Jolis and Focus vesiculosus L. were studied using a flow tank. Settlement sites were defined as &quot;sheltered&quot; or &#39;exposed&#39;. Surface area calculations revealed non-random settlement on A. nodosum, with higher than expected spore frequencies on the thallus and lateral pits and lowere than expected frequencies on the vesicles. Settlement on F. vesiculosus was random and significantly lowere than on A. nodosum. On the shore, survival of sporelings from September (post-sporulation) to May (pre-sporulation) was highly non-random on both basiphytes. On A, nodosum, lateral pits (&#39;sheltered&#39;) showed the highest survival frequency. Here the proportion of surviving sporelings increased over the study period, whereas the proportion on open thallus area (&#39;exposed&#39;) decreased. On F. vesiculosus also, preferential survival accurred on &#39;sheltered&#39; sites such as vesicle/thallus interfaces and wounds. Between September and May, all P. lanosa sporelings were lost from &#39;exposed&#39; areas (thallus surface and vesicles). Overall, frequencies of surviving sporelings were much greater on A, nodosum than on F. vesiculous. These results are discussed with reference to basiphyte morphology, epiphyte removal mechanisms and the survival strategy of P. lanosa. [ABSTRACT FROM AUTHOR]