the Tsesis , another tanker carrying 35,000 tons of oil grounded some 

 100 km to the northeast, also releasing substantial quantities oi oil. 

 This oil did not reach the area investigated in this report. 



The spill site was located on the Swedish coast of the northern 

 Baltic, roughly 65 km south of Stockholm. The archipelago here is 

 relatively narrow and open to the Baltic, with a number of small barren 

 skerries. Depths in the area are variable with a mean of 25-30 meters. 

 The surface salinity is quite stable at 6-6.5 /oo S, and increases by 

 1 /oo at 40 m depth. Surface temperatures vary from below C in 

 winter to a maximum of about 21-22 C in hot summers. This area is 

 therefore representative of mean Baltic conditions and fairly typical of 

 coastal areas with respect to hydrography, hydrology, and topography. 



It should be recognized, therefore, that not only are the Tsesis 

 results significant for understanding or predicting the effects of 

 spills in the Baltic, but also the methods and capabilities refined 

 during the study may be directly applicable to future Baltic spill 

 studies. The need for performing holistic ecological studies on the 

 effects of oil spills in the Baltic has been explained in section 1.6. 

 The Baltic environment is unique, so that the environmental risks must 

 be studied before significant widespread damage becomes a fact. If this 

 is not accomplished before a "catastrophic" incident, or its equivalent 

 in accumulated smaller ones, it will then be too late to benefit from 

 many of the lessons. 



The Tsesis incident was the second largest spill in the Baltic Sea 

 to date. Since the spill occurred in an archipelago characterized by 

 thousands of islands, inlets, rocks, and shoals, a significant length of 

 shoreline was impacted, while topography and hydrography contained the 

 spill in a relatively small, shallow area. In areas such as this (typi- 

 cal of the Baltic) low exchange rates, low energy wave conditions, and 

 near zero tidal energy mean that the removal and degradation of oil is 

 very slow. Low temperatures especially in the bottom layers, makes 

 evaporation of the acutely toxic, volatile aromatic hydrocarbons very 

 slow. Furthermore, there are indications that the low salinity may play 

 a part in prolonging the residence time of the lighter aromatic compounds 



31 



