A large marine algal bloom is observed, predominantly composed of organisms with chlorophyll a, c, and fucoxanthin, storing food as laminarin and mannitol. These algae are also known for their significant role in producing alginates. Based on these characteristics, this bloom is most likely composed of members from:
Correct: B
The combination of specific pigments (chlorophyll a, c, and fucoxanthin), storage products (laminarin and mannitol), and the production of alginates are all characteristic features of Phaeophyceae, also known as brown algae. Chlorophyceae (green algae) have chlorophyll a, b and store starch. Rhodophyceae (red algae) have chlorophyll a, d, phycoerythrin, and store floridean starch. Cyanophyceae (blue-green algae) are prokaryotic and have chlorophyll a and phycobilins, storing glycogen.