Which of the following characters for algae are incorrect from given characters?

(i) At least a half of the total carbon dioxide fixation on earth is carried out by algae through photosynthesis.

(ii) Being photosynthetic they decrease the level of dissolved oxygen in their immediate environment.

(iii) Many species of Porphyra, Laminaria and Sargassum are used by space travellers as food.

(iv) Certain freshwater brown and red algae produce large amounts of hydrocolloids.

(v) Agar obtained from Gelidium and Gracilaria.