Which Is a More Reliable Bioindicator—Mussels or Seagrass? A Case Study of the Toxic Metal Pollution in the Seawater of Boka Kotorska Bay, Adriatic Sea

In the last decades, human and industrial activities in the coastal areas have increased and that resulted in different types of contamination, including trace elements. Therefore, investigations of the southeastern Adriatic marine environment quality are intensified following seawater, biota, and sediment quality related to metals pollution. Since standard chemical analysis methods cannot provide accurate information about concentrations of trace elements in seawater, the seagrass Posidoniaoceanica (L.) Delile and the mussel Mytilusgalloprovincialis Lamarck, 1819, were used as water pollution bioindicators for identifying, especially, toxic trace elements in the Mediterranean. Surface sediment, seawater, seagrass (P. oceanica), and mussel (M. galloprovincialis) samples were collected in different seasons from the coastal area of Boka Kotorska Bay in the last 10 years (2006–2016), and analyzed in order to determine the seawater quality mainly related to Fe, Mn, Zn, Ni, Cu, Co, Cd, As, Pb, and Hg. Based on the analysis of the metal pollution index values (MPIs) in both species the highest metal concentrations were measured in winters for most of the studied trace elements. The Hg accumulation in both investigated organisms was the lowest and almost the same.