Manuela Zadravec: Presence of toxic metals as indicators of pollution of the marine ecosystem in tissue of toothed whale (Odontoceti) from the Adriatic sea. Dissertation. Faculty of Food Technology and Biotechnology. University of Zagreb, Zagreb. 2015.



Cetaceans are the mammals most completely adapted to life in the water. Whales (Cetaceans) are listed as endangered and threatened species. For many years, a significant drop in the number of individuals in a population of almost all species of this order was determined. An example of this is the Adriatic Sea in which today appears to be present only one species of whales, bottlenose dolphin (Tursiops truncates), whose number is estimated at around 220 individuals. In the Adriatic Sea occasionally stay and some other whale species that regularly inhabit the Mediterranean Sea, which are usually striped dolphin (Stenella coeruleoalba) and Risso's dolphin (Grampus griseus).

The industrial revolution is the starting point for the coming anthropogenic immobilization of toxic metals from the earth's crust (geosphere) in the global environment (hydrosphere, atmosphere and biosphere). During the past 200 years a gradual increase in human activities such as fossil fuel, metal industry, melting, application of fertilizers, the burning of municipal waste, enabled the emergence of toxic metals sources in the global environment.

Growing human populations, urbanization, rapid economic development and bad planning of coastal areas have placed increasing pressure on marine and coastal ecosystems, causing several environmental impacts, such as the release of alarming levels of trace elements into the environment. Some natural sources contribute to the concentrations of these elements in the aquatic environment, but the great majority comes from anthropogenic activities that increase their mobilization, circulation and release into the environment.

In tissues of toothed whales from the Adriatic Sea (muscle, liver, kidney, lun g, spleen, adipose tissue and skin) the concentrations of arsenic, cadmium, lead, mercury and selenium were analyzed. A total of 186 dolphins were processed, 25 of which are striped, 6 Risso's and 155 bottlenose dolphins. Concentrations of cadmium, lead, arsenic and selenium (in case that the selenium concentrations are less than 25 mg/kg) were measured by graphite furnace atomic absorption spectrometer. Concentrations of mercury was determined by flow injection mercury system. When concentrations of selenium in samples were higher than 25 mg/kg, selenium was detected with inductively coupled plasma optical emission spectroscopy.

The accumulation of cadmium, arsenic, selenium and mercury during the lifetime was confirmed. None of the dolphins analyzed in this study was not exposed to concentrations of cadmium in the liver higher than 20 mg/kg wet weight, which can cause renal failure in marine mammals. Most of the cadmium, 50% of the total amount in the body is located in liver and kidneys. Using benchmarks relevant to marine mammals this study indicated that 15.3% individuals of bottlenose dolphin, 66.6% Risso's dolphin and one striped dolphin exceed the maximum 400 mg/kg Hg threshold for hepatic damage.

Since many species of marine mammals share the coastal environment with humans and consume the same seafood (fish and cephalopods), they can serve as effective indicators of public health issues. This approach provides a new way for better understanding of the relationship between ecosystems and human health