Arsenic is very toxic element and great pollutants in the environment. In this work we determine the content of arsenic in sea water from different sampling points of Montenegrin coast (mouth of river Bojana, Valdanos, Bar port, earlier Bar, Platamuni, Tivat bay) in winter and spring period. The content of arsenic was determined by using hydride AAS technique (Perkin Elmer, model 3300). The results were compared with the literature data and standard reference materials (Sea water CASS-1 National Research Council Canada-NRCC).

Influence of eutrophication to the phytoplankton community were studied in the inner part of Boka Kotorska Bay (Kotor Bay and Risan Bay) from September 2003 to August 2004. Kotor Bay and Risan Bay is very interesting area because the influence of natural and anthropogenic eutrophication are mixed very often. Microphytoplankton density is high (greater than 10**6 cells/cubic dm) what is characteristic eutrophic area, to the highest eutrophic area (greater than 10**7 cells/cubic dm). These values we stated in the surface, because in this layer were the best conditions. In same time we stated very high values: SiO2, oxygen saturation and chlorophyll a. The conclusion is: Boka Kotorska Bay and especially Kotor Bay (as a part of Boka Kotorska) has to be protected of dangerous consequences such as blooming. It is needed to regulate wastewater, their purification and permanent control physico-chemical and biological parameters, and especially phytoplankton component.

Sea urchin, Paracentrotus lividus belongs to Echinoderms and has wide distribution as well in Meditarranean Sea as in the Adriatic Sea. It is very appreciated as object for testing negative impact of pollution, so can be used as bio indicator of sea water and sediments quality. Identification of the presence of this animal is done at 11 locations inside the Bay of Boka Kotorska (Montenegro), during 2005/2006. Obtained results show that the sea-urchin inhabit only outer part of Boka Kotorska Bay, where is open sea impact very strong, while inner part of the Bay is characterized by absence of Paracentrotus lividus, what can be caused by potential low quality of the sea water in the Bay.

There are just a few data about species and quantities of phytobenthos for the Montenegrin coast, so that us one of the difficulties for the monitoring of changes caused by human impact. With the aim to contribute to the better knowledge of phytobenthos in this area we described distribution of Cystoseira barbata in the inner part of the Boka Kotorska bay and state of the environment in this aquatory.