This study aimed to evaluate the demand for oxygen through the photosynthetic production of macroalgae Ulva lactuca, shrimp cultivated in the effluent, submitted directly to the intensity of natural light in a photoperiod of 14/10 for the latitude of 27 ºS in December, and show the potential for cultivation of this kind of integrated systems, the recirculation in marine shrimp farms. Specimens were collected in Lagoa da Conceição, Florianopolis (Brazil), and transported to the laboratory for selection of the stems. These were washed with fresh water running and then extracted several discs with a diameter of 5cm, which were dry on paper towel and weighed on electronic scales. We used 30 of 500mL Erlenmeyer flasks, previously washed with distilled water with 10% hydrochloric acid. Each received 500mL bottle of water from the canal despesca a marine shrimp farm, containing 32 of salinity and approximately 40 and 5μM ammonia and orthophosphate, respectively. The experiment included four treatments with seaweed and algae without one, as well as their respective controls, all composed of three replications. Controls were involved with laminated paper. The treatments received the following material algal densities of 1 = 1 L-1, 2 = 2 L-1, 3 = 3 L-1 and 4 = 4 L-1. The bottles were covered with paper control rods. On a plastic tank with 1000L of water, the treatments were distributed randomly on a table submerged, allowing 90% of the volume of bottles were submerged. The experiment was kept under constant renewal of water, keeping the temperature uniform, around 26, all in containers. Each time, temperature, light and dissolved oxygen were measured in all bottles, in a period of 27 hours. The photosynthetic production began from 6:30 pm, where they saw an initial increase of the oxygen concentrations in treatments with algae, while all controls remained low until the end of the experiment. There was a first photosynthetic peak around 12:30 pm, where the maximum light intensity was 1,424 lux, and a photoinhibition of algae to UV exposure of between 12:30 and 15:30 h. It was a possible excretion of UV-B at densities of 3 and 4 L-1 arising from the excess of solar irradiation. A second peak production of O2, between 18:30 and 20:30 in the four treatments with algae, resulting in higher rates to 564% of supersaturation, 490% on its photorrespiration and 150% on supersaturation of phitoplancotn showing its potential for cultivation integrated with marine shrimp in a closed system of recycling.