RESUMO
Wastewater release in an urban wetland in Mexico City entails discharging complex mixtures of hundreds of chemical substances into the aquatic system. Therefore, in order to identify the most important contaminants, a GC-MS screening method coupled with deconvolution software was used. LC50 values from ECOSAR and Toxic Units were obtained to identify the organic pollutants-of-concern and to pinpoint the most ecotoxic sites. The results showed that, even though the area has intensive farming, agrochemicals are not of concern. Industrial and domestic groups make up from about 30%-66% of the pollutants for all sites. Of the 189 identified substances, 17 were detected 44% of the time and the Toxic Unit showed that terbutol, coprostanol, and hexadecane were capable of generating considerable adverse effects on the aquatic ecosystem. Total Toxic Units for each site exhibited a decreasing trend as they distanced from the urban and agricultural area.
Assuntos
Águas Residuárias , Poluentes Químicos da Água , Ecossistema , Monitoramento Ambiental , Águas Residuárias/análise , Poluentes Químicos da Água/análise , Áreas AlagadasRESUMO
The rough scad, Trachurus lathami Nichols, 1920, is a small pelagic species distributed along the West Atlantic coast. It is most abundant in the Southern Brazil (28°30-34°S) and in the Southeastern Brazilian Bight (SEBB, 22°-28°30S). The rough scad is fished by purse seines, which main target is the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879). Age and growth are vital to understand the life cycle of a species, to fishery management and ecosystem modeling. This study aimed to assess the age and growth of T. lathami, to identify its age structure in the SEBB, and to evaluate what causes the wide differences among Trachurus species in terms of body size and growth parameters. Data available on T. lathami was attained between 2008 and 2010 from surveys at SEBB. A total of 278 whole otoliths of T. lathami, total length between 27 mm and 208 mm, were analyzed and compared with the only other source of otolith data, from 1975. Three blind readings were performed and assessed using traditional methods to study fish age and growth. Zero up to eight rings were found, each ring corresponding to one year in the life of an individual of this species. The von Bertalanffy growth model parameters were L∞ = 211.90 mm and K = 0.319 year-1. The results of the analyses have shown similarities between 1975 and 2008-2010, indicating that the otolith development, the growth pattern and the age structure remained stable. T. lathami is the smallest species of Trachurus and it has the highest growth rates among them. This is probably related to the different temperatures where larvae/juvenile and adult grow, to the absence of a strong fishing pressure and to decadal population variability.(AU)
Assuntos
Animais , Perciformes/crescimento & desenvolvimento , Distribuição por Idade , Oceano Atlântico , Costa , BrasilRESUMO
The rough scad, Trachurus lathami Nichols, 1920, is a small pelagic species distributed along the West Atlantic coast. It is most abundant in the Southern Brazil (28°30-34°S) and in the Southeastern Brazilian Bight (SEBB, 22°-28°30S). The rough scad is fished by purse seines, which main target is the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879). Age and growth are vital to understand the life cycle of a species, to fishery management and ecosystem modeling. This study aimed to assess the age and growth of T. lathami, to identify its age structure in the SEBB, and to evaluate what causes the wide differences among Trachurus species in terms of body size and growth parameters. Data available on T. lathami was attained between 2008 and 2010 from surveys at SEBB. A total of 278 whole otoliths of T. lathami, total length between 27 mm and 208 mm, were analyzed and compared with the only other source of otolith data, from 1975. Three blind readings were performed and assessed using traditional methods to study fish age and growth. Zero up to eight rings were found, each ring corresponding to one year in the life of an individual of this species. The von Bertalanffy growth model parameters were L∞ = 211.90 mm and K = 0.319 year-1. The results of the analyses have shown similarities between 1975 and 2008-2010, indicating that the otolith development, the growth pattern and the age structure remained stable. T. lathami is the smallest species of Trachurus and it has the highest growth rates among them. This is probably related to the different temperatures where larvae/juvenile and adult grow, to the absence of a strong fishing pressure and to decadal population variability.