The effects of floating mats of Azolla filiculoides Lam and Lemna minuta Kunth on the growth of submerged macrophytes

In laboratory experiments, the growth characteristics of the submerged species Elodea nuttallii (Planch.) St. John and Potamogeton crispus L. were assessed in the presence and absence of floating mats of Azolla filiculoides Lam. and Lemna minuta Kunth. Light penetration and the development of pH and dissolved oxygen differences were monitored. The growth of P. crispus was suppressed much more than that of E. nuttallii and the effects of A. filiculoides were more severe than those of L. minuta. Findings are related to possible field responses of submerged plants under floating mats, especially their abilities to compensate for the potential suppressive effects of floating mats under natural conditions.