The pioneer species in primary succession in water is :

The correct answer is Option (1) → Phytoplanktons

Option (1) Phytoplanktons — Correct. Phytoplankton are the first organisms to invade a bare water body, so they are the pioneer species of primary succession in water. Lichens (option 3) are the pioneers on bare rock instead.

Note 1: A similar question was also asked in CUET (UG) 2023 on 11-06-2023 (Slot 3).

Note 2: This question is from the topic “Succession of Plants” in Chapter 14, Ecosystem, of the pre-rationalised NCERT book. This portion is not in the present NCERT book, where the chapter is now Chapter 12, Ecosystem. The extract below is from the pre-rationalised edition.

NCERT Extract (Pre-rationalised edition, Chapter 14, Ecosystem):
Succession of Plants – “… In primary succession in water, the pioneers are the small phytoplanktons, which are replaced with time by rooted-submerged plants, rooted-floating angiosperms followed by free-floating plants, then reedswamp, marsh-meadow, scrub and finally the trees. The climax again would be a forest.”