Wordnet 3.0
ADJECTIVE (1)
1. 
 of or relating to alga; 
The Collaborative International Dictionary of English v.0.48:
Algal \Al"gal\, a., (Bot.)
   Pertaining to, or like, alg[ae].
   [1913 Webster]
WordNet (r) 3.0 (2006):
algal
    adj 1: of or relating to alga