Environmental Impact on Coastal Waters off Rio De Janeiro Due to Sewage Discharge via Submarine Outfall

A survey was made in an area of 28 km² around the outlest of Ipanema's submarine outfall in order to evaluate the impact of the raw domestic sewage effluent on coastal waters. Nutrient concentrations, dissolved oxygen, particulate matter and other physico-chemical parameters were measured monthly for 15 months. Copper and lead concentrations were also determined for two of the samplings.

The outfall has been in operation for 18 years, and the parameters measured within the observation area appear to be in steady state. From the observed radial concentration gradients within the survey area, a real extension of the steady state distribution of particulate matter and of sewage-derived nitrogen was estimated. the stationary cloud of particulate organic matter was about 150 km². From its total inventory and the discharge rate, a mean residence time of the particles in the sea of 56 days is estimated, prior to their being decomposed by bacterial action or settling to the bottom. for sewage derived N (as ammonia or nitrate), the steady state amount (above background) covers an area of about 60 km² and leads to a mean residence time of 5 ± 1 days in the ocean. Phosphorus is readily absorbed by the phytoplankton.

The presence of temperature gradients established by cold upwelling waters controls the dispersion of the sewage material and the rising of the sewage plume to the surface waters.     

The Impact of Increased Environmental Stochasticity Due to Climate Change on the Dynamics of Asiatic Wild Ass

Abstract:  Theory proposes that increased environmental stochasticity negatively impacts population viability. Thus, in addition to the directional changes predicted for weather parameters under global climate change (GCC), the increase in variance of these parameters may also have a negative effect on biodiversity. As a case study, we assessed the impact of interannual variance in precipitation on the viability of an Asiatic wild ass ( Equus hemionus ) population reintroduced in Makhtesh Ramon Nature Reserve, Israel. We monitored the population from 1985 to 1999 to determine what environmental factors affect reproductive success. Annual precipitation during the year before conception, drought conditions during gestation, and population size determined reproductive success. We used the parameters derived from this model to assess population performance under various scenarios in a Leslie matrix type model with demographic and environmental stochasticity. Specifically, we used a change in the precipitation regime in our study area to formulate a GCC scenario and compared the simulated dynamics of the population with a no-change scenario. The coefficient of variation in population size under the global change scenario was 30% higher than under the no-change scenario. Minor die-offs (≥15%) following droughts increased extinction probability nearly 10-fold. Our results support the idea that an increase in environmental stochasticity due to GCC may, in itself, pose a significant threat to biodiversity.