'algae-supporting' is a Modern English compound formed from 'algae' + 'supporting'. 'algae' comes from Neo-Latin 'algae' (plural of 'alga') meaning 'seaweed', and 'supporting' derives from Latin 'supportare' ('sub-' + 'portare') meaning 'to carry from below or sustain'.

'algae' entered scientific English from Medieval/Neo-Latin 'alga' (meaning 'seaweed'), while 'support' came into English via Old French from Latin 'supportare'; the compound 'algae-supporting' is a recent descriptive formation in modern ecological and environmental usage.

Originally, 'alga' referred specifically to seaweed and 'support' to carrying or sustaining; over time the components combined in Modern English to mean 'providing conditions for algal growth' rather than physical carrying.