Not only decaying vegetation, but also large rooted plants are removed from the area in meticulous fashion by these intelligent fish. Other nest builders assume a more positive relationship with aquatic plants. These relatives of the seahorses carefully select and dislodge the appropriate plants and weave them into a cylindrical nest in which spawning and early rearing of the fry occurs. The family of Anabantids or labyrinth fishes also use bits and pieces of plants to weave into a thick mat of bubbles that the male forms at the surface of the water. The balance between the two is delicate and the addition of excessive nutrients to the system favors the overpopulation of the phytoplankton.
Algal blooms occur and have definite adverse affects on fish populations and their reproduction.
The dense mats that are formed by the blooms shade the bottom and eliminate the slower growing rooted vegetation. Aside from the eradication of floral spawning sites, direct effects on the adults, eggs, and juveniles occur. Thick blankets of filamentous may also form. Pithophora, Rhizonium, and Hydrodictyon may form blankets that entirely cover large bodies of water. The table at the end of this paper shows the data supporting this, Potomageton foliosus and P. nodosus were the plants involved in this case.