Biomonitoring Of Environmental Pollutants From River Basin Using Bivalve Mollusc (UNIONIDAE) As A Bioindicator

One of the most serious environmental problems is the water pollution.Thousands of chemicals with unpredictable effects fall into the aquatic basin every year.Concentrations of toxic heavy metals（such as cadmium,mercury,lead,chromium）,pesticides,nitrates and phosphates,petroleum products,surfactants,detergents and so on can be detected in the water.All this has harms human health,aquatic organisms and the ecosystem as a whole.Commonly the water quality can be described in terms of physical,chemical and biological characteristics.And in recent years there has been increasing interest namely in biomonitoring.It is important to understand clearly what reactions occur in living organisms at the time of the receipt of pollutants to their environment.Therefore,research in the field of biomonitoring helps to cope with these objectives.The tasks of biomonitoring include regular assessment of the quality of the environment with the help of specially selected for this purpose living objects.It is known that biological indicators of water quality,give a broader perspective of its quality,and not only at the time of research.The objects of biomonitoring are primarily species that respond to changes in the state of the environment（physical and chemical parameters）—indicator species.Bivalves are one of the most promising objects for biological monitoring.These animals are the most suitable for assessing the ecological state of river basins.And the new methodological approach is based on a comparative assessment of the functional state of molluscs.The assessment of the functional state of molluscs is carried out by non-invasive measurement of the characteristics of their cardiac activity.These bioindicators reflect the integral response of the whole organism to changes in the environment and provide information on the state（ecological status）of the habitat of aquatic organisms.The recovery time of animal heart rate and cardiac rhythm variability were proposed as new physiological biomarkers by the authors of this technique.In our study was a detailed analysis of the original non-invasive（relating to a technique that does not involve puncturing the skin or entering a body cavity of a living organism）optical fiber method and its practical application was carried out.This technology and method proved to be very contemporary for assessing the state of aquatic ecosystems under different anthropogenic loads.Testing and evaluation can be carried out in two modes:in the field and the laboratory conditions.The method is based on measuring heart rate and analyzing the physiological state of bivalve molluscs under functional load.One of the first places where the development and testing of this original non-invasive optical fiber method has been carried out was St.Petersburg.The application of the bioelectronic system and the methodological approach in this region already allowed to get results that have provided much useful information on the assessment of the effects of anthropogenic pollution.Measuring the behavioral responses of bivalves complements cardio activity very well.The informative results in the studies prompted the continuation of the study and improvement of this approach.Was conducted a series of studies on the effect of heavy metals and detergents on the cardiac activity of molluscs to assess the health status of aquatic animals after their treatment.The main time of exposure of metals to molluscs was 3-4 days（for toxicological experiments）.It has already been established that between animals there are individual differences in responses to stimuli and this can be 40-50%in cardiac activity.There were many different factors:various concentrations of metals（including）,detergent concentrations,mollusc sizes,mollusc species,their habitat,exposure time,etc.The results showed a significant effect of pollutants on animal health.The concentration of heavy metals was chosen according to the standards for maximum permissible concentrations of pollutants for surface water.We have tested animals over the maximum permissible concentration;thus,we were able to predict the situation and have been able to evaluate the effects there of.The process of accumulation and removal of heavy metals from the body of bivalves were investigated.The greatest interest was in the study of metals such as copper and cadmium,which were used in concentrations from 50 to 500μg/L,respectively.This study as in several others,it was showed that the greatest accumulation occurs in the digestive gland and gills,and the smallest in the leg of the animal.Known fact that the water reservoir has the ability of self-cleaning,and the molluscs also have the ability to remove heavy metals from the body.But as the results showed,a lot depends on the level of pollution and the health of the animal.This study is important since some animal species are used by humans as food and this may not be safe for human health.Additionally,a study was carried out on the features of the antioxidant defense system in the soft tissues of molluscs,since ADS is a biochemical system of molluscs that provides the physiological basis for adaptation to the effects of environmental factors.The main function of ADS is the neutralization of reactive oxygen species.Active forms of oxygen are chemically very active and can cause chain reactions of oxidation of organic molecules,leading to damage to proteins,lipids,nucleic acids and carbohydrates.In the future,this leads to a violation of the metabolism and physiological functions of the body.In the final part of the study,we conducted a study with a multibiomarker approach to the assessment of ecological states of Songhua River.The results showed that concentrations of eight metals（Cd,Cr,Cu,Fe,Mn,Ni,Pb and Zn）in the water were in the range of 0.001–0.59 mg/L for Tongjiang and 0.001–0.51 mg/L for Harbin,while that in sediments were in the range of 0.67–1575.37 mg/kg for Tongjiang and 0.07–5617.13 mg/kg for Harbin,respectively.Bivalves from tested sites exposed to environmental pollution exhibited significantly different physiological states.The recovery time(T_rec)in mussels from Harbin was recorded in the range of 151 to 234 min,while that from Tongjiang was only 115 min.The metal pollution index（MPI）and bioconcentration factor（BCF）in the molluscs were calculated for each metal.BCF in the mussels from the Tongjiang area was lower than that from the Harbin area.Physiological testing,as well as the concentration of HM in water,and sediment,and also the bioaccumulation of HM in tissue showed that the ecological state of the Tongjiang area was better than that of Harbin.This approach allows considering in more detail the problem of the effect of pollutants on the health of mollusсs and the ecosystem.