Influence of aquaculture effluents on the growth of Salvinia molesta

Abstract

Objective: Aquaculture generates social and economic benefits, but also causes impacts on the environment. One of the major impacts is the release of untreated effluents into rivers, reservoirs, and lakes, which can affect aquatic populations and communities. In this study, we tested the hypothesis that effluent from aquaculture favors the growth of the floating aquatic macrophyte Salvinia molesta; Methods: The study was carried out in a non-impacted reservoir (NIR) and in another reservoir (IR) that is impacted by discharges of aquaculture effluents, and lasted for nine months. In each of the reservoirs, we installed four experimental units containing 10 ramets of S. molesta. Monthly, we measured limnological variables of the water and the biomass of S. molesta in both reservoirs; Results: The temperature, turbidity, electrical conductivity, alkalinity, chlorophyll-a, total Kjeldahl nitrogen, and total phosphorus were higher in the IR in all the collection months. At the end of the experiment, the concentrations of total nitrogen and phosphorus in the biomass of S. molesta from the IR were higher than those in plants from the NIR. The estimated support capacity (K) for S. molesta in the NIR was 3.0 ± 0.7 g DM.m-2 and in the IR was 37.4 ± 2.4 g DM.m-2 ; Conclusions: It was concluded that the discharge of aquaculture effluent modifies the limnological characteristics of the water of the receiving reservoir, and that the growth of Salvinia molesta is favored by the aquaculture effluent, because of the increases in the concentrations of nitrogen and phosphorus in the water.

Estimating nitrogen and phosphorus saturation point for Eichhornia crassipes (Mart.) Solms and Salvinia molesta Mitchell in mesocosms used to treating aquaculture effluent

“…Even considering the small number of replicates (n = 3) and the large standard deviations we observe that the growth curves of the two species in higher and lower nutrient concentrations were similar. However, high nutrient concentrations allow the plants to grow faster and reach high biomass (Thomaz et al, 2007;Pistori et al, 2010). In a reservoir impacted by aquaculture effluent, Pistori et al (2010) reported that S. molesta reached carrying capacity of 36.4 g DM.m -2 after 100 days of experiment, whereas in a non-impacted reservoir the value was 3.0 g DM.m -2 after 200 days.…”

“…However, high nutrient concentrations allow the plants to grow faster and reach high biomass (Thomaz et al, 2007;Pistori et al, 2010). In a reservoir impacted by aquaculture effluent, Pistori et al (2010) reported that S. molesta reached carrying capacity of 36.4 g DM.m -2 after 100 days of experiment, whereas in a non-impacted reservoir the value was 3.0 g DM.m -2 after 200 days. Other authors demonstrated that the growth rates of many species of aquatic macrophytes increase as nutrients availability also increases, but the increase of nutrients concentrations favor the growth of plants up to a certain concentration.…”

“…There are several examples of proliferation of some macrophytes species in aquatic environments impacted and non-impacted by organic pollution (Pieterse and Murphy, 1990;Thomaz et al, 2005;Camargo et al, 2006;Pitelli et al, 2008). A recent study showed that the growth of Salvinia molesta Mitchell was approximately 12 times higher in a reservoir impacted by aquaculture effluent (high concentration of nitrogen and phosphorus) than in a non-impacted reservoir (Pistori et al, 2010).…”

Treatment efficiency of effluent prawn culture by wetland with floating aquatic macrophytes arranged in series

“…For example, an increase of 400% in phytoplankton biomass and substantial dinoflagellates and chrysophyceae blooms were observed in lake regions close to a trout farm in Canada (Findlay et al, 2009). A recent study revealed that the floating aquatic macrophyte Salvinia molesta biomass (37.4 g dry matter m -2 ) was 12.5 times higher in a reservoir that received aquaculture effluent than the biomass (3.0 g dry matter m -2 ) in the reservoir that was not impacted by the aquaculture activity (Pistori et al, 2010).…”

Changes in the structure of the phytoplankton community in a Nile tilapia fishpond

“…We recorded high phytoplankton biovolumes in the inflow water during the first 28 days of the tilapia grow-out period. These high values might be related to the water source, since the inflow water comes from two dams that are oligo-mesotrophic and hypereutrophic and receives effluents from the sectors of fish and frog farming of CAUNESP (Pistori et al, 2010). Furthermore, this period coincided with harvesting in these sectors, when water is rich in nutrients and organic materials are released into the dam.…”