Acute toxicity assay using mysid as an alternative test organism in the assessment of the aqueous fraction of sediment.

The evaluation of sediment quality through biological testing of the aqueous fraction can be applied in dredging situations and is associated with a small number of confounding factors. The use of test organisms that are relatively resistant to contaminants is recommended when working with complex mixtures such as sediments. In this study, the sensitivity of the mysid Mysidopsis juniae to ammonia (NH3) and metals was investigated in acute toxicity laboratory tests and the results were compared to those obtained in the traditional test with sea urchin embryos and larvae. The ability of the toxicity identification and evaluation (TIE) technique, with the use of EDTA and sodium thiosulfate, to indicate the factors responsible for adverse effects was determined. The results indicate that mysids are almost 5 times more resistant than the sea urchin to ammonia (NH3), more sensitive to Cd2+ and Ni2+ and more resistant to Zn2+ and Pb2+. With the TIE technique and with the use of EDTA as a complexing agent, a greater resolution was observed in the diagnosis of the presence of the metals Cd2+ and Ni2+, which could be applied to the aqueous fraction of the sediment.

Evaluation of effectiveness of EDTA and sodium thiosulfate in removing metal toxicity toward sea urchin embryo-larval applying the TIE.

Since the development of the TIE (Toxicity Identification and Evaluation) in 1988 it has been assumed that the capacity of EDTA and sodium thiosulfate to complex some metals, and thus remove their toxicity, can be applied to both freshwater and seawater ecotoxicological tests and the results subsequently interpreted. However, it is now known that there is a wide variability in the extent of this complexation. In this context, the removal of toxicity caused by the presence of Hg(2+), Cd(2+), Cu(2+), Cr(6+), Zn(2+), Ni(2+), Pb(2+), Ag(1+) and Se(2+), through metal complexation by EDTA and sodium thiosulfate, in relation to the performance of embryo-larval tests with the sea urchin Arbacia lixula was investigated. It was observed that EDTA was capable of removing the toxicity of Pb(2+), Zn(2+) and Cu(2+) while sodium thiosulfate only reduced the toxicity of Ag(1+). Compared to the complexation observed in freshwater ecotoxicological tests, the complexing agents used in this study (EDTA and sodium thiosulfate) have a lower capacity to complex metals in the marine ecotoxicological test with A. lixula.

Physiological energetics of the brown mussel Perna perna (L.) transplanted in the Itajaí-Açu river mouth, Southern Brazil.

Groups of the mussel Perna perna were transplanted to two points and at three different depths in the coastal region close to the Itajaí-Açu River mouth, an impacted river in the south of Brazil. With the objective of evaluating the physiology changes in the organisms in relation to the control area (origin of the organisms), the clearance, respiration and excretion rates, absorption efficiency and growth were estimated. The levels of metals in the organism tissue were determined in an attempt to explain the physiological changes occurring in the study area. Organisms from Point 2 placed near the bottom showed physiological changes in comparison to the control and the transplanted organisms from Point 1. Point 2 showed greater sediment resuspension and availability of trace metals to the organisms closer to the bed. The increase in Cr concentration in the tissues of the organisms (up to 0.21 mg kg(-1) ww) was not sufficient to explain the decrease in the inhibition of clearance (28.8%) and in the absorption efficiency (15.7%), or the increased excretion rate (282.5%), which led to the organisms having a reduced scope for growth (48.6%). This indicates the possible presence of other contaminants, which were not measured, and which probably had synergistic action with the trace metals investigated.

Physiological rates in different classes of sizes of Perna perna (Linnaeus, 1758) submitted to experimental laboratory conditions.

Physiological studies of the mussel Perna perna in Brazil are almost 30 years behind those of other, more exhaustively investigated species, such as Mytilus edulis. Little is known about the variations in physiological rates due to size and the consequences of maintaining P. perna in laboratory conditions. This work investigated the variations in respiration, clearance, excretion and absorption efficiency rates of P. perna, classified by size and acclimatized in a laboratory, monitoring the mussels respiration rates and biometry over a period of 30 days, in laboratory conditions. The respiration, clearance and excretion rates presented an allometric relation with the dry weight of the organisms, with b values of 0.66, 0.48 and 0.91 respectively. On the other hand, these same rates, when considered by weight (specific rates) showed a relationship that was inverse to the size of the organisms. Only the absorption efficiency was independent of the weight of the mussel. In terms of acclimatization, it was observed that it takes 10 days for the respiration rate of the mussel P. perna to stabilize in laboratory conditions, after which it follows a routine metabolism.