The macrophytes play an important role in the regulation of biological and chemical processes in aquatic ecosystems, particularly in shallow lakes. They also play an important role in storage and nutrient cycling, serving as a source of organic matter to native environments. The aim of this study was to describe the kinetic aspects of the nutrients released during the anaerobic decomposition process of Egeria densa Planch and Chara braunii Gmnel macrophytes in waters with different trophic states. The study was conducted in vitro and under anaerobic conditions for determination of both particulate and dissolved fractions of nitrogenous, phosphorus and carbon, in predetermined days in oligotrophic and eutrophic water. Mathematical models were applied to describe the macrophytes decomposition process. Both species showed the same biphasic decay pattern of organic matter and carbon mineralization. The phosphorus, nitrogen and carbon released were high for both species, regardless of the trophic water state. The loss of mass was similar for both species and the nutrients concentration in the dam water did not represent a limiting factor for the mathematical model.

The use of irrigation water containing cyanobacterial toxins can cause significant impacts in agricultural and consequently environmental health. The purpose of this study is to evaluate the effects of cyanotoxins (microcystin-LR and saxitoxin) on germination, growth and micronuclei formation in lettuce (Lettuce sativa) and coriander (Coriandrum sativum). Seeds of lettuce and coriander were exposed during 7-9 days to environmentally relevant concentrations of microcystin-LR (MC-LR1= 0.4 µg/L; MC-LR2= 1.0 µg/L; MC-LR3= 5.0 µg/L) and saxitoxin (SX1= 0.02 µg/L; SX2= 0.1 µg/L; SX3= 0.4 µg/L). In germination test, differential responses were observed being lettuce the most affected in the presence of saxitoxin, and coriander to microcystin-LR treatments. Cyanotoxins inhibit seedlings development to both plants species and promote formation of micronuclei in root cells. Cyanotoxins inhibit seed germination, growth and cause DNA damages, but the intensity depends on both the nature of the toxin and plant species.