Distribution and Seasonal Occurrence of Aquatic Saprolegniaceae in Northwest Iowa

ABSTRACT

Nine aquatic sites in northwest Iowa were sampled at three week intervals from April through November in 1977 and 1978 for members of the Saprolegniaceae. Saprolegnia diclina was associated predominantly with the lentic, sand/gravel-bottomed sites, and Aphanomyces laevis with lentic, mud-bottomed sites. Saprolegnia ferax was slightly more common in lotic sites than lentic sites. The dominant Saprolegnia and Aphanomyces species did not seem to be affected by leaching, but the dominant Achlya and Dictyuchus species were isolated more frequently when there was some leaching from adjacent soil. Species with centric or subcentric oospores occurred most frequently in the cool waters of the spring and fall. Species with eccentric oospores tended to be more abundant in the summer. Individual species did not necessarily follow the general pattern indicated by oospore type.

Key Words:

• Saprolegniaceae
• water molds
• seasonal periodicity