Why can red algae grow at deeper depths of water than green algae?

Answer to q. 1

Green algae have chlorophyll a and b, which do not absorb green light (they reflect, hence the algae
looks green). Conversely, red algae have phycobilins that can absorb green light. As green light can
penetrate to great depths, red algae can perform photosynthesis and live at greater depths.

Answer to q. 2

Indirectly, yes we are. Dinoflagellates will, under specific conditions, experience algal blooms -
explosive growths in population. One of the primary factors contributing to this is the availability of
nutrients which can be greatly increased by agricultural runoff (human input). When the
dinoflagellates are present in great numbers, filter-feeding shellfish consume them in great quantity
and absorb their toxins. These toxins then cause neurotoxic shellfish poisoning in human consumers.