SYDNEY -- Scientists on board a Spanish research ship of the Malaspina Expedition, will look in the central Pacific Ocean for traces of radioactivity from Japan's crippled Fukushima nuclear plant in, said a renowned Spanish oceans researcher on Thursday.

Professor Carlos Duarte, who is leading the expedition, told reporters aboard the research ship Hesperides in Sydney that searching for radioactivity was not part of the original plan for the seven-month trip.

"We are going to add an element of research to the south and north track along the Pacific that was obviously not planned when we departed," Duarte said.

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"We will monitor and assess the extent of contamination by radioisotopes in the central Pacific Ocean."

The Malaspina Expedition is one of the world's largest collaborative scientific undertakings, involving some 400 scientists/researchers and two ships circumnavigating the world as part of a research program to investigate the health of the world' s oceans.  The expedition has completed half of a world tour to assess the impact of "global change" on the ocean's ecosystem.

The Fukushima nuclear reactors in northern Japan were damaged by the earthquake and tsunami which hit the country on March 11.

Radioactivity of seawater near the Fukushima nuclear power plant reportedly reached 7.5 million times the legal limit recently.

"Nobody is (currently) looking at the central Pacific (for radioactivity) and this type of expedition is very cumbersome logistically to plan," Duarte said.

"The fact that we are at sea just now provides an opportunity to do this and share the results with our colleagues."

The Hesperides will leave Sydney on Friday and sail first to Auckland.