Page 84 - 76_02

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

populations. The experiment of colonization of Nunclon wells-dish
plates painted with antifouling demonstrates validity of this
hypothesis.

Long-distances navigation is a characteristic of human civili-
zations. A lot of microalgae stowaways invade the underwater body
of our ships to disperse worldwide. Since microalgal toxins are
among the most important emerging health risk due to shellfish
consumption (51-53) introduced toxic microalgal species are an
important menace.

5. CONCLUSION

1. Marine ecosystems are specially affected by toxin-producing
introduced species of microalgae with devastating impacts
on aquaculture, fishery, tourism and public health (economic
cost estimated in $ billions). Although ships ballast water has
been considered the major vector in dispersion of microalgae,
numerous species of microalgae travel great distances
forming the biofouling attached the underwater body of ships.

2. In spite of toxic antifouling paints recovering the bottom of
ships microalgal species are resistant to these antifouling.

3. Antifouling paint-resistant microalgae arose by rare mutation,
which occurs spontaneously in natural populations prior to
antifouling paint exposure. The balance between the recurrent
appearance of antifouling-resistant mutants and their
elimination by natural selection controls the presence of
antifouling-resistant cells in the natural populations. An
equilibrium frequency estimated in around 3 antifouling
resistant mutants per each 10–4 sensitive cells should assure a
rapid microalgal colonization of the underwater body of ships.

6. AKNOWLEDGEMENTS

Special thanks are given to Carmen Romero by micrographs and
Lara de Miguel by technical support. Supported by Grants CTM2008-
05680-C02-02 and CGL2008-00652/BOS (Ministerio de Ciencia e
Innovación, Spain).

204