Marine litter abundance and distribution on beaches on the Isle of ...

MPB-08245; No of Pages 10 Marine Pollution Bulletin xxx (2016) xxx–xxx

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Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul

Marine litter abundance and distribution on beaches on the Isle of Rügen considering the influence of exposition, morphology and recreational activities Elena Hengstmann a, Dennis Gräwe b, Matthias Tamminga a, Elke Kerstin Fischer a,⁎ a b

Center for Earth System Research and Sustainability (CEN), University of Hamburg, Bundesstraße 55, 20146 Hamburg, Germany State Agency for Environment, Nature Conservation and Geology, Mecklenburg-Vorpommern (LUNG), Goldberger Straße 12, 18273 Güstrow, Germany

a r t i c l e

i n f o

Article history: Received 12 October 2016 Received in revised form 9 December 2016 Accepted 10 December 2016 Available online xxxx Keywords: Marine debris Beaches Plastics Baltic Sea

a b s t r a c t The abundance, weight and composition of marine debris were determined at the northwest coast of the Isle of Rügen in 2015. A total number of 1115 macrolitter items were registered, resulting in an abundance of 304 ± 88.96 items per 100 m of beach length and therefore being greater than the abundances found for other beaches at the Baltic Sea. Macrolitter items were predominantly composed of plastic, on average 83%. The four beaches under investigation have different exposition as well as touristic levels. The differing influence of wind and water currents as well as recreational activities on the macrolitter at these beaches was detectable. The distribution of items within a beach segment was analyzed by implementing D-GPS and drone aerial photography. The results of this analysis suggested that the identity of the substrate as well as the presence of vegetation are both major influencing factors in the macrolitter distribution. © 2016 Elsevier Ltd. All rights reserved.

1. Introduction The quantification of marine debris received increasing attention in recent studies due to the high accumulation rates of anthropogenic items in this ecosystem. According to UNEP (2005) “Marine litter is any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment”. Hereby, special emphasis was laid on plastic items because of their predominance caused by low degradation rates in contrast to other materials (Andrady, 2015). Additionally, the plastic production is increasing: Between 2004 and 2014 plastic production worldwide rose from 225 to 311 million tons per year (PlasticsEurope, 2015). Marine contaminants are not only introduced via the land (e.g. by river run-off and drainage networks), but also by sea-based sources (e.g. fishing and shipping) (Pruter, 1987; GESAMP, 1991). Plastic litter poses a threat towards marine life when present in marine habitats. Entanglement of organisms within debris (especially fishing gear) and the ingestion of smaller particles are the major direct influences on marine biota (Laist, 1987, 1996; Thompson et al., 2004; UNEP, 2005). The ingestion of small particles of microplastics compounded with the uptake and release of absorbed chemicals can have impacts on the metabolism of organisms (Andrady, 2011; Cole et al., 2011; Galloway, 2015; Lusher et al., 2015; Rochman, 2015). Macrolitter is apparent within different compartments in the marine environment, it occurs floating on the sea surface (e.g. Eriksen et al., ⁎ Corresponding author. E-mail address: elke.fi[email protected] (E.K. Fischer).

2013, 2014; Cozar et al., 2014) as well as on sea floors (e.g. Stefatos et al., 1999; Galgani et al., 2000; Watters et al., 2010). Furthermore, several local studies on marine debris at beaches have already been conducted, mostly concentrating on sandy beaches and aiming for the quantification of beached debris (Ryan et al., 2009, Browne et al., 2015). The locations of investigated beaches differ, ranging from the Balearic Islands, where 3.3 kg of marine debris per 100 m of beach length or rather 456 items per 100 m of beach length were detected (Martinez-Ribes et al., 2007), to the Oman (2.7 kg or 17.9 items per 100 m of beach length; Claereboudt, 2004) and Iran (456 items per 100 m of beach length; Sarafraz et al., 2016), to Indonesia (100 kg or 1736.5 items per 100 m beach length; Willoughby et al., 1997) and windward beaches on Curaçao (450 kg or 7556 items per 100 m of beach length; Debrot et al., 1999) and reaching even remote areas in the Antarctic (Bravo Rebolledo and Van Franeker, 2015). The list of studies presented here is not complete since the number of studies on macrolitter on beaches increased rapidly in the last decade. Further studies and their results, however, will be presented in the Discussion section. Moreover, several beach cleaning programs collect data on coastal marine debris, like the ICC (International Coastal Clean-up) and the “Marine Litter Watch” in Europe organized by the European Environmental Agency (EEA). OSPAR (Convention for the protection of the Marine Environment of the North-East Atlantic) developed a guideline to provide a uniform monitoring approach improving the comparison between different regions (OSPAR, 2010). At the Baltic Sea the Baltic Marine Litter Project (MARLIN) was established, gathering data of 23 beaches in Sweden, Finland, Estonia and Latvia (MARLIN, 2014). Beside these transnational initiatives, national programs have been developed

http://dx.doi.org/10.1016/j.marpolbul.2016.12.026 0025-326X/© 2016 Elsevier Ltd. All rights reserved.

Please cite this article as: Hengstmann, E., et al., Marine litter abundance and distribution on beaches on the Isle of Rügen considering the influence of exposition, morphology and ..., Marine Pollution Bulletin (2016), http://dx.doi.org/10.1016/j.marpolbul.2016.12.026

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E. Hengstmann et al. / Marine Pollution Bulletin xxx (2016) xxx–xxx

as well. Most North and Baltic Sea neighboring countries conduct programs on beach litter monitoring, for example, the UK (Marine Conservation Society, 2016), Sweden, Latvia and Denmark (Keep Sweden Tidy, FEE Latvia, Save the North Sea - Denmark; MARLIN, 2014; Strand et al., 2015). Germany's coastlines are almost equally distributed along the North and the Baltic Sea. Thus, Germany is an active partner both within the OSPAR and the HELCOM (Baltic Marine Environment Protection Commission - Helsinki Commission) community. In the state of Mecklenburg-Vorpommern (MV) in Germany a beach monitoring program based on OSPAR guidelines was established by the State Agency for Environment, Nature Conservation and Geology, MecklenburgVorpommern (LUNG) starting in 2011. At 29 beach segments marine debris is registered four times a year (LUNG, 2015a). In order to further analyze marine debris at the Baltic coast of MV a case study was conducted at four beaches on the northwest coast of Rügen (Germany) in July 2015. The aim was not only the quantification and analysis of distribution patterns of macrolitter, but also the comparison of beaches with different orientations as well as compositions and various levels of tourism.

2. Materials and methods 2.1. Study area The study area is located in northern Germany at the coastline of the state Mecklenburg-Vorpommern. The case study was performed on the Isle of Rügen, in the Baltic Sea. The sample sites are shown in Fig. 1.

Four beaches were selected due to their different exposition and accessibility and according to certain criteria of the OSPAR beach monitoring program which states that the beach should: -

“be composed of sand or gravel and exposed to the open sea; […] be a minimum length of 100 m and if possible over 1 km in length; be free of ‘buildings’ all year round; ideally not be subject to any other litter collection activities.” (OSPAR, 2010)

Two different beaches were studied close to the village Varnkevitz. These face to the north and are therefore called “North beach 1” (N1) and “North beach 2” (N2). The first northern beach unit belongs to the beach monitoring program of MV (beach ID: VARNKEVZ_HL_01) and is cleaned manually every quarter by the Windland-Schule in Altenkirchen, Rügen, since 2012 (LUNG, 2015a). The third beach is situated close to the village Vitt. A road leads to the beach, which is located on a small fishery port. The beach is east-facing and is therefore referred to as “East beach” (E). Furthermore, a few small food stands are situated close to the eastern beach as well as the Kap Arkona (a headland with a cliff consisting of chalk and till) which is located in a northern direction. The beach close to Dranske will be called “West beach” (W), due to its exposition in the western direction. Since new vacation homes are built directly behind the beach, tourism is likely to increase in the next years. However, this site is only accessible for pedestrians and no food or drink outlets are found close to it. Signs of bonfires were visible the day the samples were taken.

Fig. 1. The study sites at the northwestern coast of the Isle of Rügen (Baltic Sea) as well as the prevailing wind situation (frequencies of observed wind speeds) seven days prior to sampling (Arcona, Rügen). Coordinate System: ETRS_1989_UTM_Zone_33N, Projection: Transverse Mercator, Wind Data: DWD, 2016, Visualization of Wind Data: R Core Team (2016), RStudio Team (2015), and Carslaw and Ropkins (2012).



The detailed characteristics of the investigation sites are summarized in Table 1. The major differences between the three selected beaches are their exposition and accessibility and thus, the public frequentation. 2.2. Sampling At each beach investigated in the case study, a 50 or 100 m section was defined for the sampling process. This segment was selected according to certain criteria: (i) free from plants, (ii) at least a width of 5 m and (iii) at least 40% sand. The beach segment was measured and ranging poles were positioned at the four corners, as well as in the middle of the section. The macrolitter sampling followed the OSPAR beach monitoring guidelines (OSPAR, 2010) which do not only account for plastics but for other kinds of litter material, like textiles, rubber and metal, as well. In the following, the term macroplastic refers to the items of the category “artificial polymers” while macrolitter includes all categories considered in the guidelines. For the purpose of macrolitter monitoring, the 100 m beach segments were split into two parts. The first sub-segment of 30 m was investigated in detail to provide a more exact recording of marine debris items. At the western beach this sub-segment was only 20 m. Within these sub-segments, every litter item was located and categorized according to the OSPAR classification. In addition, geographic coordinates were gathered for every item using a D-GPS device (Trimble Geo 7×). To our knowledge, this is the first study incorporating the exact coordinates of litter items. Aerial images via drone (DJI Phantom II) were taken of each beach unit to later recover the macrolitter items. Photographs of the 100 m beach segment as well as of the sub-segments were taken, respectively. The ranging poles were needed in combination with additional pole signs in order to perform georeferencing. The remaining part of the beach segment (70 m/30 m) was also examined for macrolitter following the OSPAR guidelines in classifying and collecting items. Here no coordinates were registered, though. 2.3. Laboratory analysis and data evaluation Macrolitter was air-dried, separated according to the different OSPAR beach monitoring categories and weighed. In addition, the check lists were transferred to an electronic version (Excel 2010, ©Microsoft) to calculate statistical parameters and the portions of

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macroplastic items and weight percentages on all items registered as a whole and for each beach individually; Top-ten lists were compiled. According to OSPAR (2007) marine litter can be classified into five different groups revealing information on the sources and activities generating this waste: (i) fishing, including aquaculture, (ii) galley waste (non-operational waste from shipping, fisheries and offshore activities), (iii) sanitary waste/sewage-related waste, (iv) shipping, including offshore activities (operational waste), and (v) tourism and recreational activities. OSPAR (2007) also indicates marker items for these groups. Based on this classification, sources for marine debris on the four beaches on Rügen were estimated. Furthermore, the geographic coordinates, gathered for every litter item, for each beach segment were individually corrected and converted to a shapefile to visualize the findings in a Geographic Information System (GIS). The aerial photographs of the sub-segments were georeferenced using the reference points of the ranging poles in ArcGIS (©ESRI; Version 10.1) and overlaid by the macrolitter shapefiles. A first order polynomial (affine) transformation was used for the georeferencing of the aerial images of each beach, respectively. For the visualization of results diagrams and maps were prepared using again Excel 2010 and AcrGIS. 3. Results In total, 1115 items were collected at the beaches investigated in July 2015, resulting in 10.28 kg of macrolitter. The number of items per 100 m of beach length ranged from 202 to 404 with a mean of 304 ± 88.96 items per 100 m of beach length. Most litter items were found at the northern beach unit N1 close to Varnkevitz (404 items per 100 m of beach length) followed by the second northern beach N2 (380 items per 100 m of beach length). The eastern beach featured a lower number of items with 230 items per 100 m of beach length. At the beach close to Dranske (W), the smallest number of items was found (202 items per 100 m of beach length) (see Fig. 2). In terms of weight, macrolitter along the beaches varied between 0.59 and 5.75 kg per 100 m with a mean of 3.05 ± 1.93 kg. Again, the highest value was registered at the northern beach unit N1 (5.75 kg per 100 m) followed in this case by the western beach close to Dranske (3.80 kg per 100 m). The eastern beach represents the lowest level in terms of weight, with 0.59 kg per 100 m. Plastic items were most abundant on every beach sampled representing 62 to 88% (on average: 82.69%) of all litter collected (see Fig. 2). Each other material group comprised b4% of all items. Glass

Table 1 Description of the beaches sampled on the Isle of Rügen. N1 - Varnkevitz

N2 - Varnkevitz

E - Vitt

W - Dranske

Exposition Length Width Back of the beach Coordinates (Gauß-Krüger) Development behind beach Closest village

North 100 m 7.2–10.2 m Cliff and forest 6062233 N 4588517 E Nature reserve

North 100 m 11–22 m Cliff with low vegetation 6062068 N 4588028 E Nature reserve

East 100 m 14.3 m Forest 6060629 N 4592520 E Agriculture; vacation homes

West 50 m 5.3 m Cliff 6059175 N 4580456 E Village

Varnkevitz (0.5 km/ca. 20 inhab.)

Vitt (0.1 km/ca. 100 inhab.)

Accessibility

Difficult (small trail; steep terrain)

Dranske (3.5 km/ca. 1000 inhab.) Limited (small trail)

Touristic level Date of sampling Prevailing currents Prevailing winds Type of material

Low 14.07.2015 W W 40% sand, 56% pebbles, 3% bigger stones, 1% algae 1) Swimming/sunbathing 2) Local people 3) Sailing

Varnkevitz (0.5 km/ca. 20 inhab.) Difficult (small trail; steep terrain) Low 14.07.2015 W W 90% sand, 10% pebbles

Major beach using

1) Swimming/sunbathing 2) Local people 3) Sailing

Easy (entrance at village) High 15.07.2015 NW NW 57% pebbles, 40% sand, 3% big stones 1) Tourists 2) Sailing 3) Fishing

Medium 15.07.2015 NW NE 60% sand, 40% pebbles 1) Swimming/sunbathing 2) Sailing 3) Local people


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and ceramic items were equally present as paper and cardboard objects with 3.7% and 3.6% of all items, respectively. In contrast, plastic items are less frequently presented in terms of weight; 30.55% of items registered were made out of plastic (range: 2.94 to 37.66%). Glass and ceramic items were the second most common objects (mean: 28.15%) and the groups “cloth/textile” as well as “processed/worked wood” amounted for 12%. Rubber items represented one-tenth of all litter by weight. A top-ten ranking of macrolitter items found on the four beaches was compiled (Fig. 3). These top-ten items represented 69% of all objects registered. The most frequently found objects were plastic pieces between 2.5 and 50 cm which made up for 17% and were closely followed by the category “cigarette butts/filters” (15%). Local variations between the beaches under investigation become apparent when looking at the different rankings. Plastic pieces (2.5–50 cm) are within the top-five items at every beach, similar to the cigarette butts and filters, which can be found within six most frequent items at every beach. The top-ten lists of the two northern beaches show great similarity to each other. Many of these items are included within the most common items for the eastern beach as well; however, some items are only apparent at this beach, like paper fragments, foil and food wrappers. The beach with western orientation differs greatly. Here, other wood items made up for 16% and rubber pieces as well as bottles were registered frequently, which did not occur within the top-ten lists of any other beach studied. The assessment of source groups of collected marine litter items is visualized in Fig. 4. At the first northern beach unit N1 most items can be associated with fishing activities (39 items) as well as public littering (39 items). Eleven items are probably originating from shipping activities. Similarly, these three groups are also the major sources at beach N2, although public littering (54 items) represents a greater source than fishing activities (19 items) here. The western beach unit shows a similar distribution of marker items. In contrast, fishing activities play a minor role for the “East beach” investigated in this study. Here, only public littering could be identified as a considerable source. However, it must be considered that the major part of items could not be assigned any source. For only 24% and 21% of all items at the two northern beaches a source could be identified, respectively. At the eastern (12%) and western (13%) beach this number was even smaller.

A specific distribution of macrolitter along the beach becomes obvious when using the coordinates of registered items within the 30 m sub-segment and the aerial photographs (see Fig. 5). Objects accumulate in the back of the beach, where the substrate becomes coarser and dune and bush vegetation occurs. This is especially true for the two northern beaches and, but less distinctly, for the eastern beach. However, items were also registered within the fine sediment of the barrier beach (circa 40%) at the eastern beach. Similarly, around one third of all items were found in front of the vegetated area at beach N2 while at the beachN1 nearly 90% of all objects are located in the back of the beach with coarse material and patches of vegetation. The scattering over the width of the beach is different at the eastern beach compared to the two northern beaches, though. Here, macrolitter items are more evenly distributed across the whole width of the beach. Additionally, rocks were found at this beach where marine debris was increasingly accumulated. The western beach close to Dranske differs from the other beaches. Here, no consistent distribution over the whole segment is apparent but most macrolitter items are found where natural debris was piled up by waves in front of the cliff as well. 4. Discussion With an average of 2.94 kg macrolitter per 100 m the value of this study is below several international studies on macrodebris at beaches. For example, at the Belgian coast Van Cauwenberghe et al. (2013) registered 9.27 kg per 100 m. While the studies indicating the weight of macrodebris found on beaches are, as mentioned before, rare there are several studies on beached debris reporting the number of items per length of the beach. With a mean of 318 items per 100 m of beach length the beaches on Rügen seem to be more polluted by macrolitter than other beaches along the Baltic Sea. Strand et al. (2016) investigated two beaches at the Baltic Sea in Denmark and registered 35–204 items per 100 m of beach length (mean: 136). These findings are not only comparable to the results described in this study due to a similar location but the monitoring by Strand et al. (2016) was equally based on the OSPAR beach monitoring protocol. The MARLIN project resulted in an average of 130 macrolitter objects per 100 m at beaches in the Baltic region (MARLIN, 2014), again a lower value than the findings of this

Fig. 2. Abundance of macrolitter and percentage of macroplastics on the four beaches on Rügen.



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Fig. 3. Classification of macrolitter items including the top-ten items collected on the four beaches on Rügen.

Fig. 4. Sources of marine litter items found on the four beaches on Rügen per 100 m of beach length; Diagram in the upper right corner shows the mean over all four beaches. Coordinate System: ETRS:1989_UTM_Zone_33N, projection: Transverse Mercator, Background Map: OSM World Topographic Map.


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Fig. 5. Distribution of macrolitter items (GPS coordinates) within the different beach segments of Rügen (aerial images via drone). Coordinate System: ETRS:1989_UTM_Zone_33N, projection: Transverse Mercator.

study. MARLIN does not use the OSPAR beach monitoring protocol, but the one introduced by UNEP. The classes used for the categorization of macrolitter items are similar, though and also the criteria for beach selection do overlap. A great dataset concerning macrolitter monitoring (via the OSPAR protocol) at the German Baltic coast was provided by the State Agency for Environment, Nature Conservation and Geology MecklenburgVorpommern (LUNG). The LUNG, in cooperation with other actors, comprising environmental associations, large-scale nature reserves and schools, gathered data on marine debris at 29 beaches along the Baltic coast of MV between 2011 and 2015. Compared to this beach monitoring data, the mean for the northwest coast of Rügen is increased as well. The mean of collected macrodebris at the coastline of MV amounts to 68 ± 101.76 items per 100 m of beach length (Lung, 2015b) whereby considerable regional variations are apparent (see Fig. 6). Minimum quantities with on average seven macrolitter items per 100 m of beach length (found at the beach ZINGST_KIR_01) are far below the average of the study on Rügen. The beach close to the village Mukran is the only beach where more items (404 per 100 m of beach length) were registered than were presented in this case study. In general, beaches with high numbers of macrolitter items are concentrated in the east of MV. The increased pollution with marine debris in parts of Rügen is

also reflected by the results presented for the four beaches in this case study. The northern beach close to Varnkevitz is regularly sampled by the Windland-Schule of Altenkirchen and shows an average of only 70 items per 100 m of beach length over a three-year period. A difference of N300 items exists due to a more detailed survey in July 2015. While the vegetated back of the beach is not considered for the regular beach monitoring in Varnkevitz as a consequence of its lack of accessibility, the marine debris accumulated over a longer period in this area was registered in this study. Even the lower results for the eastern and western beach examined on Rügen are above most of the monitored values for beaches along the coastline of MV, except for the beach close to Mukran (MUKRAN_FH_01). Mukran is highly influenced by the port (transshipment of 1,088,000 tons in 2015; Statistical Office of MecklenburgVorpommern, 2016) and tourism in Sassnitz (70,000 tourists per year; Statistical Office of Mecklenburg-Vorpommern, 2016) compared to the four beaches at the northwest coast of Rügen; however, they are still close to major shipping routes in the Baltic Sea in the north of the Isle of Rügen. Conversely, beaches with a very low number of macrolitter items are increasingly situated within national parks or remote areas within the



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Fig. 6. Number of items per 100 m of beach length and material composition of macrolitter items at the coast of Mecklenburg-Vorpommern; Diagram in the upper left corner shows the mean over all 29 beaches. Data Source: LUNG, 2015b; Coordinate System: ETRS:1989_UTM_Zone_33N, projection: Transverse Mercator, Base Map: ESRI World Ocean Base.

coastline of MV. The four beaches under investigation in this study are more frequently visited and therefore, show a much higher pollution of marine debris. Comparing the findings of macrolitter abundances on Rügen to results gathered in the North Sea region, numbers of items are similar or lower (Table 2). For the Skagerrak much higher quantities were recorded. Strand et al. (2016) investigated one beach at the North Sea coast of Denmark and one beach in the Skagerrak region where 265 and 3102 macrolitter objects were registered per 100 m, respectively. Again, the study on beaches along the Belgian coast shows an augmented value with a mean of 6429 items per 100 m of beach length (Van Cauwenberghe et al., 2013). At the beaches investigated on Rügen the percentage of plastic objects was on average 82.7%. A similar value is reported in other international studies on macroplastic. Worldwide, marine debris is predominantly composed of plastic (Derraik, 2002). Jambeck and Johnsen (2015) also registered plastic items far more often than other materials on beaches (85% of all items collected were made out of plastic). Compared to the plastic portion on the four beaches sampled on Rügen, the one for the coastline of MV is lower (mean: 69%) (LUNG, 2015a). Again, regional differences are apparent for the coastline of MV: Especially the beaches monitored on Rügen show a high percentage of plastic within a 100 m of beach length (Fig. 6). Furthermore, the category paper/cardboard is a major material on the coastline of MV with on average 12% of all macrolitter items (LUNG, 2015a) which is less represented on the beaches studied in 2015. Strand et al., 2016 reported 60% plastic on Danish beaches at the Baltic coast, whereas the amount was higher for the North Sea coast and Skaggerak (71%).

Plastic and polystyrene pieces between 0 and 50 cm represent most items along the coast of MV (Plastic/polystyrene pieces (2.5–50 cm): 19%; Plastic pieces (0–2.5 cm): 11%) followed by cigarette butts (9%) (LUNG, 2015a). This is similar to the findings in this study where plastic and polystyrene pieces as well as cigarette butts were frequently found on all four beaches investigated. Furthermore, the top-ten list for the northwest coast of Rügen is similar to the top-ten list of MV as a whole. While the top-one item for Belgian North Sea coast were resin pellets (Van Cauwenberghe et al., 2013) these were not at all found at the beaches on Rügen. Here, plastic pieces (b50 cm) were the top-one item. Furthermore, foam sponge and shotgun cartridges were often found on the northwest coast of Rügen which were absent at the Table 2 Mean number of macrolitter items found on beaches in Europe.

Country

Region

Items/100 m of beach length

Germany Germany Denmark Scandinavia Germany Denmark Belgium

Rügen Mecklenburg-Vorpommern Baltic Sea coast Baltic Sea coast Wadden Sea Skaggerak North Sea coast

318 68 80 130 236 3102 6429

UK

North Sea/Channel/Irish Sea

330

Spain

Balearic Islands

3567

References This study LUNG (2015a) Strand et al. (2016) Marlin (2014) Fleet et al. (2009) Strand et al. (2016) Van Cauwenberghe et al. (2013) Marine Conservation Society (2016) Martinez-Ribes et al. (2007)


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North Sea coast. On the other hand, Strand et al. (2016) reported these items not only for the Baltic Sea but also for the Skaggerak region. In comparison to their top-ten lists the only striking difference is the occurrence of plastic caps and lids in this study that are not listed within the top items published by Strand et al. (2016) for beaches along the Baltic Sea. Comparing the weight and the number of macrolitter items at the four beaches sampled in this study, they are differently ranked. The western beach has the least items per 100 m of beach length but has the second highest amount of marine debris concerning the weight. This results from a few heavy items found at this beach (e.g. bigger wood pieces and a shoe) whereas the items at the beach facing to the east for example were lighter items, predominately small plastic pieces and cigarette butts. Despite the fact that the northern beaches are more difficult to access, most litter per 100 m of beach length was found here. One explanation is associated with the ocean surface currents, flowing predominately from west or northwest within one week prior to sampling (BSH, 2016) and delivering marine debris to this beach. In addition, the northern beaches are more exposed to wind, coming predominately from west or northwest in this area seven days as well as four weeks prior to sampling (DWD, 2016). Furthermore, these beaches are closer to major shipping routes in the Baltic Sea. Although the littoral states of the Baltic Sea have agreed on a convention concerning the enhancement of port facilities and waste management of ship-generated litter (HELCOM, 2009) the seaside source of marine debris remains important at the beach since the Baltic Sea has very dense ship traffic (HELCOM, 2009). The higher percentages of items belonging to the source group ‘shipping’ further underline the importance of this origin at the two beaches facing a northern direction. In 1994 Tuomisto conducted a study on beach litter in Finland and stated that the sea-side source of marine debris is especially litter discarded by ships (cruise liners) (HELCOM, 2009). A higher influence of input from the sea on the two northern beaches compared to the eastern beach is underlined, as mentioned before, by the distribution of source items. The percentage of items being introduced by fishing and shipping is increased compared to the beach close to Vitt (E) indicating that more litter is washed and blown ashore by currents and wind. Wind-blown items were probably less accumulated at the eastern beach due to the above described wind direction. Ocean surface currents were also coming predominately from west leading to less marine debris introduced from the sea side at the eastfacing beach. Also, the top-ten list for the eastern beach predominately consists of items being left by people underlining the major influence of public littering compared to the sea-side source. Moreover, the influence of wind and currents interacts with the effect of tourism. The two northern beaches are less influenced by tourism than the beach close to Kap Arkona, a very touristic beach and a recreational area. Even though no cleaning activities are provided at the eastern beach by the local authorities the awareness and self-control of beach users might be higher to keep the beach clean so that the total number of items within the 100 m beach segment is smaller compared to the two northern beaches. Slavin et al. (2012) found out that beach visitors in Tasmania coming from Tasmania did litter more than tourists. The same might be true for Rügen where the very touristic eastern beach is less polluted than the less known northern beach units. Selfcontrol is higher for the “East beach” where several tourists can supervise each other. On the contrary, visitors at the northern beaches are rarely controlled by other beach visitors. The prevailing winds and currents prior to sampling would suggest that a higher number of items are found at the western beach, although the number of items per 100 m of beach length is the lowest compared to the other beaches under investigation. A smaller width and the cliff indicating that waves periodically reach the back of the beach lead to remobilization of macrolitter items which were previously washed onto the coast. Smith and Markic (2013) stated that tidal inundation can

not only transport macrolitter onto the beach but can also remove it. However, the sea still represents the major pathway of macrolitter to the beach. Compared to the second northern beach as well as to the beach facing eastwards the count of items classified as being fishing items is higher in the west. Moreover, wood objects were the top-one item at this beach indicating the sea as a source of macrodebris since it was visibly worked by water. There is only little influence of tourism at this beach, expressed in the lower proportion of source items belonging to the group of public littering. Van Cauwenberghe et al. (2013) stated that different levels of tourism are not sufficiently significant to explain differences between marine litter amounts on various beaches. In contrast, sea surface currents as well as the predominant wind direction have a major influence on where marine debris is accumulated. However, the touristic gradient seems to have a higher impact on beaches on Rügen, regarding the number of items registered and the relevance of public littering items on the different beaches. The interaction with other factors, like the wind direction and ocean surface currents, is important as well, though. This is especially true for items originating from fishing and shipping activities. In addition, the source location of macrolitter items plays a significant role on where they will be washed ashore (Van Cauwenberghe et al., 2013; Critchell and Lambrechts, 2016). The distribution of litter items within the beach profiles reveals that objects are easily retained by vegetation and coarser material on the beaches. On all beaches with coarser sediment and vegetation in the back of the beach, marine debris accumulated in these regions while at the front of the beach fewer items were found. This area is constantly or occasionally influenced by wave activities. Waves and currents can deliver litter onto the beach as well as remove items (Smith and Markic, 2013). Local depressions as well as agglomeration of rocks can prevent the dispersion of marine litter along a beach by wind (Topçu et al., 2013) and are therefore spots where items will accumulate. North beach N1 has agglomerations of rocks in the back of the beach. In the case of the eastern beach we also find coarser material as well as rock ridges further to the back. In contrast, north beach N2 comprises a depression which is partly flooded. The aerial images clearly show that marine debris is accumulated in this depression as well as in the back of the beaches with accumulations of stones. 5. Conclusion Considerably higher amounts of macrolitter were registered for the four beaches in the northwest of Rügen in July 2015 compared to other beaches in Mecklenburg-Vorpommern and other studies at beaches along the Baltic Sea coast. Differences were evident between the beaches with different expositions and levels of tourism concerning the quantity of beached debris as well as its composition and sources. The east-facing beach with the highest level of touristic influence has a noticeable percentage of public littering items in regard to the source. In contrast, the western beach seems to be much more influenced by ocean currents and wind with more items being introduced by fishing and shipping. However, most litter items could not be assigned any source. In general, marine litter was dominated by plastic items on all beaches under investigation with 83%. This percentage is comparable to other international studies on macrolitter on beaches. Other materials only play a minor role within marine debris on the northwest coast of Rügen. Assessing the distribution of marine debris within beach segments via aerial images revealed that objects are increasingly accumulated where coarser material and vegetation is present as well as on rocky conglomerations and in depressions. Beach litter monitoring in MV needs further data collection to allow deeper insights in spatial and temporal distribution of marine debris. Due to singular sampling in this study no temporal distribution of



macrolitter could be analyzed. Regular sampling at these beaches may determine variations within the course of the year. The data set provided by the LUNG already includes up to five years; however, long-term data is necessary to reveal significant trends over time. Acknowledgements The authors thank the participants of the study project “Ostsee Küsten- u. Meeresver-schmutzung durch Mikroplastik” for their support within the field as well as Rolf Schernus, teacher at the Windland-Schule Altenkirchen, Rügen. Special thanks for collecting the beach litter monitoring data in Mecklenburg-Vorpommern to EUCC - The Coastal Union Germany, Citizen of the Ocean network, Nature and Biodiversity Conservation Union Germany (NABU), SouthEast Rügen Biosphere Reserve, Regional School “Windland” Altenkirchen, Vorpommern Boddenlandschaft National Park, Jasmund National Park, Usedom Nature Park, Jordsand Association. We are grateful to Maria Nero who kindly revised the language of the final manuscript. 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