Page 80 - 76_02

VICTORIA LÓPEZ-RODAS Y COLS. AN. R. ACAD. NAC. FARM.

division. The Malthusian parameter of fitness of TBT-resistant
mutants and wild type sensitive cells (0.085 and 0.24 respectively)
were used to estimate the coefficient of selection of TBT-resistant
mutants (s). By using the values of m and s, the frequency (q) of
resistant alleles was estimated in circa 3 TBT-resistant mutants per
10–4 wild type sensitive cells.

3.4. Growth of TBT-sensitive and TBT-resistant cells
3.4. on antifouling paint

When wild type sensitive Dc1M cells were grown during 15 days
on antifouling paint in Nunclon wells-dish plates a massive
destruction of cells was observed. Antifouling paint totally inhibited
the cell growth and most of the cells were destroyed (initial no. =
5.0 × 105 cells ml–1; final no. = 1.6 × 105 cells ml–1). In contrast TBT-
resistant mutants were able to grow directly on antifouling paint
(initial no. = 5.0 × 105 cells ml–1; final no. = 1,5 × 106 cells ml–1).

4. DISCUSSION

Numerous microalgae were found in the biofouling recovering
the underwater body of ships. As expected pennate diatom species,
which can easily be attached to surfaces by mucilage secretions (25)
are very numerous. Also benthic dinoflagellates are abundant in
the ships biofouling. Obviously, early stages of macroalgae easily
colonize biofouling.

A lot of resting stages of phytoplankton (cysts and spores) were
found in the biofouling. These resting phases seems to be especially
well adapted to survive in the biofouling. Since most phytoplanktonic
organisms has spores and resting cysts that serve as a perennation
function (25), i.e. they allow phytoplankton to survive periods that
are not suitable for growth and afterwards germinate when
conditions improve, biofouling is a potential source for microalgae
dispersion.

Apparently, several species detected on ships biofouling could be
exotic species. Taken in account that different families of clones

200