Recent benthic foraminiferal distribution and related environmental factors in Ezcurra Inlet, King George Island, Antarctica

This investigation attempts to determine which environmental parameters of the bottom water and sediment control recent foraminifera fauna at Ezcurra Inlet (King George Island, Antarctica), using data collected during four summers (2002/03, 2003/04, 2004/05 and 2006/07). The study revealed that Ezcurra Inlet contain typical Antarctic foraminifera fauna with three distinct assemblages and few differences in environmental parameters. The species Bolivina pseudopunctata, Fursenkoina fusiformis, Portatrochammina antarctica, and Adercotryma glomerata were abundant in the samples. An elevated abundance, richness and diversity were common at the entrance of the inlet at depths greater than 55 m, where the inlet was characterized by low temperatures and muddy sand. In the inner part of the inlet (depth 30-55 m), richness and diversity were low and the most significant species were Cassidulinoides parkerianus, C. porrectus, and Psammosphaera fusca. Shallow waters showed low values of richness and abundance and high temperatures coupled with coarser sediment. In areas with high suspended matter concentrations and pH values associated with low salinity the most representative species were Hippocrepinella hirudinea and Hemisphaerammina bradyi.

HYDRODYNAMICS AND SUSPENDED SEDIMENT TRANSPORT IN THE CAMBORIU ESTUARY - BRAZIL: PRE JETTY CONDITIONS

Estuarine hydrodynamics is a key factor in the definition of the filtering capacity of an estuary and results from the interaction of the processes that control the inlet morphodynamics and those that are acting in the mixing of the water in the estuary. The hydrodynamics and suspended sediment transport in the Cambori estuary were assessed by two field campaigns conducted in 1998 that covered both neap and spring tide conditions. The period measured represents the estuarine hydrodynamics and sediment transport prior to the construction of the jetty in 2003 and provides important background information for the Cambori estuary. Each field campaign covered two complete tidal cycles with hourly measurements of currents, salinity, suspended sediment concentration and water level. Results show that the Cambori estuary is partially mixed with the vertical structure varying as a function of the tidal range and tidal phase. The dynamic estuarine structure can be balanced between the stabilizing effects generated by the vertical density gradient, which produces buoyancy and stratification flows, and the turbulent effects generated by the vertical velocity gradient that generates vertical mixing. The main sediment source for the water column are the bottom sediments, periodically resuspended by the tidal currents. The advective salt and suspended sediment transport was different between neap and spring tides, being more complex at spring tide. The river discharge term was important under both tidal conditions. The tidal correlation term was also important, being dominant in the suspended sediment transport during the spring tide. The gravitational circulation and Stokes drift played a secondary role in the estuarine transport processes.

EROSION LOSSES FROM RUNOFF: INTERACTION OF SOIL COVER AND EROSION CONTROL PRACTICE

The flow of sediment from cropped land is the main pollutant of water sources in rural areas. Due to this fact, it is necessary to develop and implement technologies that will reduce water and sediment discharges. Accordingly, an experiment was conducted in the Department of Biosystems Engineering - ESALQ / USP, Piracicaba - SP with the objective to evaluate the effect of different soil cover (bean, grass and bare ground) and erosion control practices (wide base terraces and infiltration furrows in slopes (no practices to control erosion)) while measuring water losses in runoff. The statistical design adopted was randomized blocks in a 3x3 factorial scheme resulting in 9 treatments with 3 replicates (blocks). The period of rainfall data collection was December 6, 2007 to April 11, 2008. A 21.1 cm diameter rain gauge was installed in the experimental area. Terraces were the most efficient practices for reducing erosion losses in the treatments with infiltration furrows being better than the control treatment. Bean was more effective than grass in reducing erosion. Bare ground was the least efficient.

A large Cervidae Holocene accumulation in Eastern Brazil: an example of extreme taphonomical control in a cave environment

A remarkable cervid bone accumulation occurs at a single passage (named Cervid Passage; CP) at Lapa Nova, a maze cave in eastern Brazil. CP lies away from cave entrances, is a typical pitfall passage and contains bone remains of at least 121 cervids, besides few bats, peccaries and rodents remains. There is no evidence of water (or sediment) flow at the site and in general bones lack post depositional alterations and display anatomical proximity, suggesting that the majority of the remains found inside CP (mainly cervids) are due to animals that after entering the cave got trapped in the site. Observations suggest that two entrances could have provided access to cervids (and the few other animals, besides bats), either by falling inside the cave or by entering by their own free will. Once inside the cave, the maze pattern would make route finding difficult, and of all passage intersections, only the one leading to CP would result in a non-return situation, starving the animal to death. Radiocarbon dates suggest that animal entrapment occurred during at least 5 thousand years, during the Holocene. The reasons why mainly cervids were found are unknown but they are probably related to the biology of this group coupled with the fact that caves provide several specific taphonomic processes that may account for a strong bias in bone accumulation. Indeed, the frequent occurrence of Cervidae in both the fossil and sub-fossil record in Brazilian caves may be related to an overall high faunal abundance or may suggest that these animals were especially prone to enter caves, perhaps in search of nutrients (as cave saltpetre) or water.

Calcium nitrate addition to control the internal load of phosphorus from sediments of a tropical eutrophic reservoir: Microcosm experiments

The main objective of this study was to perform laboratory experiments on calcium nitrate addition to sediments of a tropical eutrophic urban reservoir (Ibirite reservoir, SE Brazil) to immobilize the reactive soluble phosphorus (RSP) and to evaluate possible geochemical changes and toxic effects caused by this treatment. Reductions of 75 and 89% in the concentration of RSP were observed in the water column and interstitial water, respectively, after 145 days of nitrate addition. The nitrate application increased the rate of autotrophic denitrification, causing a consumption of 98% of the added nitrate and oxidation of 99% of the acid volatile sulfide. As a consequence, there were increases in the sulfate and iron (II) concentrations in the sediment interstitial water and water column, as well as changes in the copper speciation in the sediments. Toxicity tests initially indicated that the high concentrations of nitrate and nitrite in the sediment interstitial water (up to 2300 mg L-1 and 260 mg L-1, respectively) were the major cause of mortality of Ceriodaphnia silvestrii and Chironomus xanthus. However, at the end of the experiment, the sediment toxicity was completely removed and a reduction in the 48 h-EC50 of the water was also observed. Based on these results we can say that calcium nitrate treatment proved to be a valuable tool in remediation of eutrophic aquatic ecosystems leading to conditions that can support a great diversity of organisms after a restoration period. (C) 2012 Elsevier Ltd. All rights reserved.