The Study of Heavy Metal accumulation (Zn, Cu, Pb and Cd ) in muscle of Great White Heron (Egretta alba) in Hara Biosphere Reserve

 
Introduction
Environmental pollution specially sea  pollution is one of the complex and minatory problems‚ human faced with these days. Many of human activities have irrecoverable outcomes and effects on marine environment in a way that destruction of marine zones becomes a threat.
Sea was one of the important sources with special advantages for mankind in all the times and still is, so protect of its environment and animal live in it has a significant role in mankind process of life.
Heavy metals are the most important material that enter to the sea through rivers and shore zones and aggregate in aquatic body through food chain. Heavy metals can cause serious effects on ecosystem stability. In assessment of an ecosystem changes, research about the all elements and relation is impossible,so using monitoring species can provide trustful information for evaluating environment quality. Biological monitoring of seashore zones with use of sea animals is a substantial method to study pollution cause to waste water discharge and human wastes. Bird in comparsion with other animals are too sensitive to environment pollution. They may distribute chemicals like heavy metals through direct connection or using polluted water or food. In other way, because of their indirect connection to polluted sources, they can determine the level of toxic element concentration in marine ecosystem feed chain. So the bird pollution for heavy metals can anticipate of pollution in food chains.
In this study the Great White Heron (Egretta alba) selected for evaluating the heavy metals concentration. Among different tissues, soft ones are more used for monitoring activities so we use muscle of Great White Heron in this study.
Materials and Methods
Hara Biosphere Reserve is located in south of Iran in the Straits of Khuran between Queshm Island and the Persian Gulf. Its latitude and longitude coordinates are 36°40' to 37° Nand 55°21' to 55°52' E, respectively. Situated in Mehran River delta, it hosts the largest seabirds along the Persian Gulf shoreline and, therefore, represents a center of biodiversity in Iran. The variety of biosphere reserve with its unique mangrove trees provides a diverse habitat for birds like egrets, herons, pelicans, and plovers. In a way, that in 2010, the host had been 36 species and 13,000 water birds and wader birds. It also serves as a breeding and spawning habitat for fish, shrimp, and other crustaceans. On the other hand, this region is one of the protected areas in Iran and this region was introduced as one of the important bird areas by international organization of bird life.
After primary studies about the studying areas we collected 20 Great White Heron in November and Desember 2012 from Hara Biosphere Resesve. After that‚ they transferred to laboratory. In laboratory birds were dissected, and one tissue sample of  muscle were taken from each bird with a steel scalpel and placed in oven in 105°C for 24 hours. After that we weight samples by scale for 1 gram parts. In digestion phase add with nitric acid (65%) and perchloric acid (60%) in ration of 4 :1 to each samples ( one gram of weighted samples with 8 mil liter nitric acid and 2 mil liter perchloric acid) and in Hot Block Digester, first in 40°C for one hour and then in 140°C for 3 hours digested. Later samples screen by whatman screen paper and the volume of the solution reached to 25 ml by distilled water. Each samples then kept in refrigrator in polyethylene jars in order to later evalute heavy metals. In this study measurement of heavy metals concentration took place by atomic absorption machine contrAA 700 model. For confidence from digestion process accuracy and effectiveness of consume materials on heavy metal concentration, in each digestion round, there were a control sample to achieve the sizable results from concentration got from the metal in diffrent samples. Mann Whitney U test were used for comparing the concentration of heavy metals in male and female and adult and juvenile birds.
Discussion of Results
In this study the result showed that maximum average concentration belongs to zinc and the minimum to cadmium. Also the results showed that there was no significant difference about heavy metal concentration between male and female except for lead. Also‚ there was no significant difference in heavy metal concentration between adult and juvenile birds.
The average of zinc concentration in Great White Heron muscle in this study is 96.53 µg/g that in compare  of Karimi᾽s studies on Phalacrocorax carbo in Anzali pond in Iran is much more than.
The average of copper concentration in our study is 11.78 µg/g that in compare  of Karimi᾽s studies on Phalacrocorax carbo in Anzali pond in Iran is too low.
Essential metals like zinc and copper are neccessary for body metabolism‚ but if their concentration in animal body increased‚ it will have bad effects on animal health. Essential metals are necessary in all tissues. This metals play an basic role in growing chicks and their bone growth. Painting and scrubing of ships in shipbuilding factories and their wastes full of zinc in Bandar Abbas is the most important factor in increasing the concentration of zinc and copper in this bird.
The average of lead concentration in our study is 0.72 µg/g that in compare of Lucia᾽s studies on grey plover in France is much more than Lead (Pb), which often is present in relation to hunting activities, impairs the growth and survival of nes‌‌tlings; causes haemolytic anaemia in wild Pb-poisoned birds; has adverse effects on reproduction, such as decreased plasma calcium and egg production; and causes behavioral problems.Human activity and development of oil refinery and petrochemical industry‚ zinc and lead factories in Qeshm Island and ship transportation in South of Iran may play the most important role in absorption of this metal in muscle tissue of this bird.
The average of cadmium concentration in our study is 0.049 µg/g that in compare  of Tsipoura᾽s studies on Canada geese in New Jersey is much more than. Cadmium has been described as one of the most dangerous trace elements in food and environ‌‌ment, not only for its high toxicity but also for its persistence. Atmospheric cadmium deposited on the earth's crust can be absorbed or retained by soil particles and become part of biological structures. Dissolved cadmium is readily absorbed by plants and leaches rapidly into the subsoil, contaminating deep and surface waters The transfer of cadmium from soils to the edible portions of agricultural crops is significantly greater than that of other elements.
The most important factor in increasing cadmium in Hara region is due to oil pollutions‚ because cadmium is one of the elements of oil. Either‚ if the oil pollution don’t occure by accidents or sudden events‚ it causes by exit of ship᾽s ballast water that this problem happen in Bahonar‚ Folad and Rajaei᾽s waterfront.
We compared the mean concentrations of heavy metal with standards. The results showed that the average concentration of zinc is much higher than standards but the levels of lead‚ copper and cadmium in muscle was below toxicity level. Nevertheless, high concentration of these elements in some samples showing the exposure of these birds to heavy metals. Generally human activities and development and stablishment of various industries around Hara region can be the basic sources of pollution and the effective cause of increasing these metals.
 Conclusions
The results showed that there was no significant difference about heavy metal concentration between male and female except for lead. Also‚ there was no significant difference in heavy metal concentration between adult and juvenile birds. The concentration of heavy metals in birds affected by lifeplace‚ rate of atmosphere pollution and their diet.
Also‚the results showed that the levels of lead‚ copper and cadmium in muscle was below toxicity level except zinc‚ but the high concentration of heavy metal in some samples indicates that birds are potentially pose at the risk of heavy metal in their habitate.