## 3 Results  
### Litter Pollution in Harbors--Concentrations  
The marinas in Rostock differ in location and framework conditions. The Alter Strom in Rostock, Warnemunde, is a former fishing harbor in the center of the seaside resort of Warnemunde. The Alter Stadthafen is the oldest harbor basin in Rostock city center, and the Ludewigsbecken is an old but recently restored harbor area. In principle, all harbors have already existed for over 500 years and are nowadays used for leisure boats. All of them are affected by major harbor events, namely the Warnemunde Week and the Hanse Sail. While the Alter Stadthafen and the Alter Strom show a pollution of 0.12-0.14 litter particles/m\({}^{2}\), the Ludewigsbecken shows a higher pollution (1.75 particles/m\({}^{2}\)). The Baltic Sea marina in Hohe Dune, opened in 2005, shows a lower pollution of 0.02 particles/m\({}^{2}\) (Table 1).  
Similar to Rostock, the city harbor in Kiel has existed for over 500 years. The traditions of the leisure-boat harbors Dusterbrook and Seeburg, near the city center, go back to the Olympic Games of 1936. Similar to the city harbors of Rostock, both show a pollution of 0.07-0.18 litter particles/m\({}^{2}\). Both harbors are principally affected by the Kiel Week. In contrast, the Baltic Sea marinas in the surroundings of Kiel show a pollution of less than 0.1 litter particles/m\({}^{2}\). Overall, the average pollution in German marinas is 0.28 particles/m\({}^{2}\) resp. 0.1 particles/m\({}^{2}\), if the total investigated area is divided by the total number of particles.  
In Egypt and Tunisia, the harbors are old and still partly host traditional fishing activities and are located close to the city centers. The only exception is Yasmine Hammamet, which represents a new sport-boat harbor built in the late 1990s as a tourism center. The pollution in Montazah (Alexandria, Egypt) and Bizerte (Tunesia) exceeds 3 particles/m\({}^{2}\) (Table 1). The average pollution in African marinas is about 1.6 particles/m\({}^{2}\) resp. 0.7 particles/m\({}^{2}\), if the total investigated area is divided by the total number of items. The pollution is about seven times higher than in German harbors. The extrapolation of the data to the entire harbor area visualizes the dimension of the pollution problem. In the large African harbors, the total number of particles is above 100,000. However, these extrapolations are associated with very high uncertainties because, apart from the Alter Strom in Germany, less than 1% of the total harbor areas were investigated.  
\begin{table}
\begin{tabular}{l l r r r r r r r r r} \hline  & \multicolumn{1}{c}{**Marina**} & \multicolumn{1}{c}{**Analyzed**} & \multicolumn{1}{c}{**Harbore**} & \multicolumn{1}{c}{**Analyzed**} & \multicolumn{1}{c}{**Number**} & \multicolumn{1}{c}{**Items**} & \multicolumn{1}{c}{**Items**} & \multicolumn{1}{c}{**Water**} & \multicolumn{1}{c}{**Secchi**} & \multicolumn{1}{c}{**Camera**} \\  & & \multicolumn{1}{c}{**Area (m2)**} & \multicolumn{1}{c}{**Area (m2)**} & \multicolumn{1}{c}{**Area (m2)**} & \multicolumn{1}{c}{**Area (5)**} & \multicolumn{1}{c}{**of items**} & \multicolumn{1}{c}{**per m2**} & \multicolumn{1}{c}{**per m2**} & \multicolumn{1}{c}{**Per Harbor**} & \multicolumn{1}{c}{**Depth (m)**} & \multicolumn{1}{c}{**Depth (m)**} & \multicolumn{1}{c}{**Depth (m)**} & \multicolumn{1}{c}{**Distance (m)**} \\ \hline \multirow{6}{*}{**C**.} & Alter Strom & 765 & 38,00 & 201 & 105 & 0.14 & 5,216 & 2.40 & 2.40 & 0.78 \\  & Alter Stadthafen & 82 & 10,000 & 0.82 & 10 & 0.12 & 1,220 & 3.10 & 0.80 & 0.63 \\  & Ludewigsbecken & 8 & 11,000 & 0.07 & 14 & 1.75 & 19,250 & 1.40 & 0.60 & 0.25 \\  & Hohe Dune & 340 & 250,000 & 0.14 & 6 & 0.02 & 4,412 & 3.90 & 3.30 & 1.43 \\  & Disterbrook & 286 & 30,000 & 0.95 & 21 & 0.07 & 2,203 & 2.40 & 2.40 & 0.95 \\  &