Evaluation of tropical water sources and mollusks in southern Brazil using microbiological, biochemical, and chemical parameters

Florianopolis, a city located in the Santa Catarina State in southern Brazil, is the national leading producer of bivalve mollusks. The quality of bivalve mollusks is closely related to the sanitary conditions of surrounding waters where they are cultivated. Presently, cultivation areas receive large amounts of effluents derived mainly from treated and non-treated domestic, rural, and urban sewage. This contributes to the contamination of mollusks with trace metals, pesticides, other organic compounds, and human pathogens such as viruses, bacteria, and protozoan. The aim of this study was to perform a thorough diagnosis of the shellfish growing areas in Florianopolis, on the coast of Santa Catarina. The contamination levels of seawater, sediments, and oysters were evaluated for their microbiological, biochemical, and chemical parameters at five sea sites in Florianopolis, namely three regular oyster cultivation areas (Sites 1, 2, and oyster supplier), a polluted site (Site 3), and a heavily polluted site (Site 4). Samples were evaluated at day zero and after 14 days. Seawater and sediment samples were collected just once, at the end of the experiment. Antioxidant defenses, which may occur in contaminated environments in response to the increased production of reactive oxygen species (ROS) by organisms, were analyzed in oysters, as well as organic compounds (in oysters and sediment samples) and microbiological contamination (in oysters and seawater samples). The results showed the presence of the following contaminants: fecal coliforms in seawater samples (four sites), human adenovirus (all sites), human noroviruses GI and GII (two sites), Hepatitis A viruses (one site), JC Polyomavirus in an oyster sample from the oyster supplier, Giardia duodenalis cysts, and Cryptosporidium sp oocysts (one site). Among organochlorine pesticides, only DDT (dichlorodiphenyltrichloroethane) and HCH (hexachlorocyclohexane) were detected in some sediment and oysters samples in very low levels; site 4 had the highest concentrations of total aliphatic hydrocarbons. PAHs, and linear alkylbenzenes (LABs) found either in oysters or in sediment samples. The major concentration of fecal sterol coprostanol was found at site 4, followed by site 3. After 14 days of allocation in the four selected sites, there was a significant difference in the enzymes analyzed at the monitored spots. The detection of different contaminants in oysters, seawater, and sediment samples in the present study shows the impact untreated or inadequately treated effluents have on coastal areas. These results highlight the need for public investment in adequate wastewater treatment and adequate treatment of oysters, ensuring safe areas for shellfish production as well as healthier bivalve mollusks for consumption.

Hybrid heuristic-waterfilling game theory approach in MC-CDMA resource allocation

This paper discusses the power allocation with fixed rate constraint problem in multi-carrier code division multiple access (MC-CDMA) networks, that has been solved through game theoretic perspective by the use of an iterative water-filling algorithm (IWFA). The problem is analyzed under various interference density configurations, and its reliability is studied in terms of solution existence and uniqueness. Moreover, numerical results reveal the approach shortcoming, thus a new method combining swarm intelligence and IWFA is proposed to make practicable the use of game theoretic approaches in realistic MC-CDMA systems scenarios. The contribution of this paper is twofold: (i) provide a complete analysis for the existence and uniqueness of the game solution, from simple to more realist and complex interference scenarios; (ii) propose a hybrid power allocation optimization method combining swarm intelligence, game theory and IWFA. To corroborate the effectiveness of the proposed method, an outage probability analysis in realistic interference scenarios, and a complexity comparison with the classical IWFA are presented. (C) 2011 Elsevier B.V. All rights reserved.

Do changes in carbon allocation account for the growth response to potassium and sodium applications in tropical Eucalyptus plantations?

Understanding the underlying mechanisms that account for the impact of potassium (K) fertilization and its replacement by sodium (Na) on tree growth is key to improving the management of forest plantations that are expanding over weathered tropical soils with low amounts of exchangeable bases. A complete randomized block design was planted with Eucalyptus grandis (W. Hill ex Maiden) to quantify growth, carbon uptake and carbon partitioning using a carbon budget approach. A combination of approaches including the establishment of allometric relationships over the whole rotation and measurements of soil CO2 efflux and aboveground litterfall at the end of the rotation were used to estimate aboveground net production (ANPP), total belowground carbon flux and gross primary production (GPP). The stable carbon isotope (delta C-13) of stem wood alpha-cellulose produced every year was used as a proxy for stomatal limitation of photosynthesis. Potassium fertilization increased GPP and decreased the fraction of carbon allocated belowground. Aboveground net production was strongly enhanced, and because leaf lifespan increased, leaf biomass was enhanced without any change in leaf production, and wood production (P-W) was dramatically increased. Sodium application decreased the fraction of carbon allocated belowground in a similar way, and enhanced GPP, ANPP and P-W, but to a lesser extent compared with K fertilization. Neither K nor Na affected delta C-13 of stem wood alpha-cellulose, suggesting that water-use efficiency was the same among the treatments and that the inferred increase in leaf photosynthesis was not only related to a higher stomatal conductance. We concluded that the response to K fertilization and Na addition on P-W resulted from drastic changes in carbon allocation.