Abstract. 1 Introduction

Transcription

1 Have efforts to clean up the marine environment been successful? - German beached bird surveys provide an index for oil pollution levels in the southern North Sea D. M. Fleet^ & B. Reineking^ * National Park Office Schleswig-Holstein Wadden Sea, Tonning, Germany. "Common Wadden Sea Secretariat, Wilhelmshaven, Germany. Abstract Oil from shipping has been polluting the North Sea since it was introduced as fuel at the beginning of this century. The expansion in the use of heavy fuel oil and the subsequent disposal of oil residues at sea led to a drastic increase in marine oil pollution in the southern North Sea in the early 1980s. In March 1998, a Research and Development Project investigating the oil input into the North Sea and effects on this of free oil disposal facilities in German North Sea harbours was initiated in Germany. On the basis of the results of beached bird surveys, aerial surveillance, the amount of oil received by oil disposal facilities in German harbours and other evidence, the effectiveness of legislation and other measures regarding oil input from shipping is being assessed. Beached bird surveys have been carried out on a regular basis on German North Sea coasts since The data from these surveys give a valuable and reliable indication of the level of oil pollution in the southern North Sea. An assessment of this data and that of similar surveys that have been carried out in other North Sea states form the basis of the results presented. 1 Introduction Oil pollution from shipping at sea can be assigned to two broad categories. Pollution as a result of major shipping accidents, such as the "Pallas" incident in Schleswig-Holstein, Germany in 1998, where oil is released at one site and chronic oil pollution as a result of operational discharges.

2 118 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control The chronic oil pollution of the North Sea increased drastically in the early 1980s. It remains one of the most important forms of marine pollution and the most noticeable. Today the main cause of chronic oil pollution on German North Sea coasts is still the illegal disposal of fuel oil residues at sea as the analysis of oil samples taken from bird feathers has shown [1,2]. In the 1950s and the decades that followed a number of measures were implemented with the aim of reducing the input of oil into the sea from shipping to a level that does not damage the environment. 1958:OILPOL 1973: MARPOL 1983: MARPOL Annex 1 ratified : Provision of free reception facilities in German harbours 1993: Tightening of limits for legal disposal of oil according to MARPOL 1999: North Sea was designated as a special area according to MARPOL, Annex 1. 2 Beached bird surveys at the German North Sea coast In March 1998 a Research and Development Project "Identification, quantification and evaluation of the oil input into the North Sea" was initiated in Germany by the Federal Environmental Agency in co-operation with the federal states of Niedersachsen, Hamburg and Schleswig-Holstein. This three-year study is a follow up of two previous studies on the marine oil-pollution/bird complex which supply us with an unbroken record of the effects of oil pollution on the avian part of the marine ecosystem since the middle of the 1980s [3, 4, 5, 6, 7, 8]. The main question to be approached by the present project is: have the measures implemented to reduce the illegal input of oil from shipping in the North Sea taken effect? The effectiveness of legislation and other measures regarding oil input from shipping is to be assessed on the basis of the results of "Beached Bird Surveys" (counts of the numbers of dead birds washed ashore and assessment of the proportion of these birds that are oiled), aerial and other surveillance activities, the amount of oil received by oil disposal facilities in German harbours and other evidence. Beached bird surveys have been carried out on a regular basis on German North Sea coasts since The survey sites are distributed at the German North Sea coast (see Fig. 1) with a total length of the sites covers about 100 km. In general, the sites are surveyed twice a month in line with the agreed guidelines at the OSPAP/JAMP level [9]. The data from these surveys give a valuable and reliable indication of the level of oil pollution in the southern North Sea [10]. A number of factors can effect the numbers of birds wintering in the North Sea and the numbers of birds washed up on North sea coasts. In the presented studies we do not therefore look at the number of oiled birds found on the beaches as this is more susceptible to the effects of factors other than the amount of oil pollution. As the "index" of the effects of oil on birds the proportion of all

3 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control 119 birds found on beaches that are oiled - the so-called oil-rate is used, which is now standard for beached bird studies throughout Europe [9]. 3 Findings of the beached bird surveys Although over 60 bird species have been recorded as oiled on the beaches of the German North Sea coast, the Guillemot Uria aalge is by far the most common, accounting for just less than half of all records. Therefore the Guillemot is often used as reliable biological indicator for oil pollution in this area. Two species of sea duck, the Eider Somateria mollissima and the Common Scoter Melanitta nigra account together for a further 25% of all records. /Hartingen _/* THE NETHERLANDS Niedersachsen Figure 1: The German North Sea coast on which the beached bird survey sites are located (TSS= Traffic Separation Scheme). The Guillemot is distributed throughout the North Sea in winter. Feeding on fish, it spends most of its time on the water surface or diving for prey. It is one of a number of pelagic species that are very susceptible to oil pollution. The two duck species, which also spend much of their time on the water surface or diving for food, are more coastal in distribution, wintering in the Wadden Sea (the Eider Duck) or just seaward of the Wadden Sea islands.

4 120 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control 1/85 85/86 86/87 87/88 88/89 89/9O 9O/91 91/92 92/93 93/94 i/97 97/98 98/99 Figure 2: Oil-rates of the Guillemot Una aalge on the North Sea coast of Germany in winter in the period 1984/85 to 1998/99. Looking at the oil-rate of the Guillemot over the last 15 a reduction in the oil-rate in the first years of the 1990s can be observed (Fig. 2). This is also apparent in the curves for other species. 4 Discussion of the findings As, however, the oil-rate can also in some circumstances be affected by factors other than the amount of oil in the sea. The first question to be asked is: have such factors greatly effected the oil-rate during the study period and how? 4.1 Influencing factor others than oil The main factors that would be expected to influence oil-rate resulting from chronic pollution are the prevailing weather conditions, natural mortality ("bird wrecks") and larger oil incidents Weather conditions With the exception of the extremely cold winter 1995/96 (Fig. 3) no correlation has been found to exist between weather conditions and the oil-rates of birds found on German North Sea coasts. The extremely cold winter of 1995/96 led to a reduction in the oil-rates of two auk species, the Guillemot and the Razorbill Alca torda (Figs. 2 and 4). This was most likely caused by an increased natural mortality, perhaps caused by a weather induced reduction in the availability of prey species. Figure 3: Average temperature (C ) on Helgoland, Germany in winter in the period 1990/91 to 1998/99 (Source: German Weather Office).

5 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control 121 Figure 4: Oil-rates of the Razorbill Alca torda on the German North Sea coast in winter in the period 1993/94 to 1998/99. Our data from the other pelagic species, such as the Kittiwake Larus tridactylus and the Fulmar Fulmarus glacialis, support this idea. Only very few Kittiwake corpses were recorded on German coasts in this winter, indicating that this species left the southern North Sea for other feeding grounds. The oil-rate of the Fulmar was very low in that winter (Fig. 5). 94/95 95/9<5 96/97 97/98 98/99 Figure 5: Oil-rates of the Fulmar Fulmarus glacialis on the German North Sea coast and numbers of dead Fulmars recorded on selected sample plots in winter in the period 1992/93 to 1998/ OO Figure 6: Number of oiled and unoiled Guillemots Uria aalge found on selected sample plots on German North Sea coasts in winter in the period 1992/93 to 1998/99.

6 122 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control Although natural mortality of the Guillemot, Razorbill and the Fulmar must have been high in 1995/96 an increase in the number of birds washed ashore, as would be expected when mortality increases, did not occur. This apparent contradiction can be explained by the fact that the cold weather on the North Sea coasts in that winter was associated with a high proportion of north-easterly winds which led to less corpses being washed ashore. It can be speculated also that some or many Guillemots and Fulmars left the area to feed elsewhere, as apparently did the Kitti wakes Mass natural mortality Mass natural mortality of seabirds certainly does effect the oil-rate. It increases the number of "clean", non-oiled birds washed ashore and reduces dramatically the proportion of oiled birds recorded on beaches. Such a mass mortality occurred in February 1999 when large numbers of especially Guillemots but also Fulmars, Gannets Sula bassana and Kittiwakes were washed ashore on southern North Sea coasts (Figs. 5 and 6) [8, 11]. The effect of these mass deaths can be seen in the oil-rates for the Guillemot, where the lowest ever value was recorded in 1999 (Fig. 1). It is interesting to note, however, that oil-rates for this species in autumn 1998 were higher than ever. A higher than normal natural mortality of Fulmars also must have occurred in the winter 1997/98 (Fig. 5) Oil incidents Oil incidents, such as the "Pallas" also effect the oil-rates, however, at a more local level [8]. This is especially noticeable in the coastal species such as the Eider Duck. The peaks in the oil-rate of the Eider Duck can be attributed to larger oil incidents on or near to German North Sea coasts (Fig 7). in$ ^% ^m# C3il sn in r. c'iz i* '" \_ CJ5 i i Po rti ieiit *- <G< %4 ti A B «nt ## n i stein a N Vai-i SH ients ring i icident n SH rh : L: / m lil! rr q ^W 5553 m mm # ##r 1994/ / /97 97/ /99 ^ Figure 7: Oil-rates of Eider Duck Somateria mollissima in Niedersachsen and Schleswig-Holstein (SH), Germany in the period 1992/93 to 1998/ Discussion of the influencing factors Factors other than oil pollution have effected the oil-rate, however, they have done so in a predictable way. The effects of extreme weather conditions in 1995/96, the mass mortality in 1999 and "local" oil incidents can be filtered from

7 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control 123 the data so that the data can be used as an index for chronic oil pollution in the southern North Sea. Different bird species supply indexes for the intensity of the oil pollution of different regions. The corpses of pelagic species such as the Guillemot, Fulmar, Gannet and Razorbill, which show the highest oil-rates on German North Sea beaches, originate from populations wintering in the southern North Sea, in the region of the Traffic Separation Scheme (TSS). The analysis of oil samples taken from these birds show that they are almost exclusively polluted with heavy fuel oil residues. Birds polluted with oil from the North Sea oil platforms and/or with crude oil residues from ships only occur occasionally on the German North Sea coast [1,2]. The oil-rates of birds wintering just seaward of the islands, such as the Common Scoter, are also high (57%) whereas the Eider Duck, that winters more in coastal waters has lower oil-rates (14%). The oil-rates of this species and of the also generally coastal Common Scoter are to a greater extent effected by local oil incidents. 4.2 Correlation of oil-rates and other information There is an extremely good correlation between changes in the oil-rate of the Guillemot and the annual number of oil pollution incidents recorded in the Traffic Separation Scheme area by the central information centre in Cuxhaven (Fig. 8). This supports our hypothesis that we are measuring the pollution levels in the southern North Sea. Trends in the oil-rate of Guillemot can be shown more clearly if expressed as a 5-year running mean which eliminates the short term fluctuations between years (Fig. 9). On German North Sea coasts the oil-rate of the Guillemot dropped from 77% at the end of the eighties (1984/ /89) to 52% at the beginning of the nineties (1989/ /94) and rose again to 62% at the end of that decade (1993/ /98). 1985/86 -*s \ s3 "^ I: c^ r, C^il uit,.u=,,l.-, i ia,t~ ^x^ ^X^^/ 1 990/9 1 -Tj O r- ~^N n ^ s^ 1 99 \» 7/98. r ^^ Figure 8: Number of oil incidents recorded by the central recording office in Cuxhaven (ZMK) in the area of the shipping Traffic Separation Scheme (TSS), German Bight and winter oil-rates of the Guillemot Uria aalge on the German North Sea coast for the period 1985/86 to 1997/98.

8 124 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control Figure 9: Oil-rates of Guillemot Una aalge on the German North Sea coast expressed as a 5-year running mean. The amount of oil disposed of in German harbour facilities increased steadily after the start of the free reception facilities pilot project in Germany, it reached a peak in 1993 and decreased from 1994 onwards when Hamburg began to set limits on the extent of free disposal and when Bremen opted out of the free disposal system in 1996 (Fig. 10). Looking again at the oil-rate of the Guillemot, expressed as a 5-year mean the reduction in the oil-rate during the free reception facilities project becomes apparent (Fig. 9). It appears that the reduction in oil-rates of bird species measured on the German North Sea coast in the beginning of the 90s does represent a real reduction in the amount of oil pollution in the south eastern part of the North Sea at that time, that is connected to the provision of free oil disposal facilities in German harbours during the pilot project. Furthermore the general decrease in the oil-rate from the end of the eighties to the end of the nineties indicates that pollution levels in the southern North Sea have generally declined over the last 15 years. Figure 10: The amount of oil (nf) disposed of in reception facilities in German North Sea harbours in the period to Comparison with other studies Similar studies in the period 1976/77 to 1996/97 on the neighbouring North Sea coast of the Netherlands Camphuysen [12] registered steady declines in oil-rates in all species groups except the scoter. These oil-rates are, however, still considerably higher than those recorded on the German coast. At the Danish

9 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control 125 Wadden Sea coast a significant decrease in the oil-rates of Eider, Kittiwake, Guillemot and Auks in general was recorded for the period 1984 to 1994, followed by a sharp increase from 1994 to 1995 [13]. For all species on the north western coast of Jutland, Denmark however, the proportion of oiled birds remained unchanged at a high level throughout the period According to the authors of the Danish study the Danish Wadden Sea reflects the German situation and the high pollution levels on the Danish North Sea coasts are the result of illegal discharges of ships leaving the Baltic Sea, which is a special area according to MARPOL, Annex 1. The above mentioned authors generally consider the reduction in the pollution of the North Sea as measured by beached bird surveys to be the positive effect of the MARPOL agreement and aerial surveillance measures. Data for the German North Sea coast confirms the data from neighbouring North Sea countries. However, the German data indicates that free reception facilities in the harbours are an effective way of reducing oil pollution even further. It remains to be seen whether the designation of the North Sea as a special area according to MARPOL Annex 1 in August 1999 will also help to reduce chronic oil pollution in the marine environment of the North Sea. References [1] Dahlmann, G., Timm, D., Averbeck, C., Camphuysen, C., Skov, H. & Durink, J. Oiled Seabirds-Comparative Investigations on Oiled Seabirds and Oiled Beaches in the Netherlands, Denmark and Germany ( ). Marine Pollution Bulletin 28(5), pp , [2] Dahlmann, G. & Sechehaye, A. Verolte Seevogel an der detuschen Nordseekiiste 1998/ Ergebnisse der Olanalysen. Seevogel 21(1), pp ,2000. [3] Vauk, G., Dahlmann, D., Hartwig, E., Ranger, v J. C., Reineking, B., Schrey, E. & Vauk-Henzelt, E. Olopfererfassung an der deutschen Nordseekiiste und Ergebnisse der Olanalysen sowie Untersuchungen zur Belastung der Deutschen Bucht durch Schiffsmull. Umweltbundesamt, Wasser Forschungsbericht , Norddeutsche Naturschutzakademie: Scheverdingen, [4] Vauk, G., Hartwig, E., Schrey, E., Vauk-Henzelt, E. & Korsch, M. Seevogelverluste durch Ol und Mull an der deutschen Nordseekuste von August 1983 bis April 1988, Umweltbundesamt, Wasser Forschungsbericht : Berlin, [5] Averbeck, C., Korsch, M.,. Vauk, G. & Wilke, J. Seevogel als Olopfer, Umweltbundesamt, Wasser Forschungsbericht , Norddeutsche Naturschutzakademie: Schneverdingen, 1993.

10 126 Oil and Hydrocarbon Spills II: Modelling, Analysis and Control [6] Fleet D. M, Gaus, S., Hartwig, E., Potel, P. & Schulze Dieckhoff, M. Olopfer in der Deutschen Bucht im Zeitraum 1. Oktober 1992 bis 31. Dezember Seevogel 16(4), pp , [7] Fleet D. M., Gaus, S., Hartwig, E., Potel, P., Reineking, B. & Schulze Dieckhoff, M. Olopfer in der Deutschen Bucht im Zeitraum 1. Juli 1994 bis 30. Juni Seevogel 20(2), pp. 43^8, 1999a. [8] Fleet D. M., Gaus, S., Hartwig, E., Potel, P., Reineking, B. & Schulze Dieckhoff, M. PALLAS-Havarie und Seevogelsterben dominieren Spulsaumkontrollen im Winter 1998/99. Seevogel 20(3), pp , 1999b. [9] OSPAR / JAMP Guidelines on Standard Methodology for the Use of (Oiled) Beached Birds as Indicators of Marine Oil Pollution [10] Camphuysen, C. J. & Franeker, J. A. The value of beached bird surveys in monitoring marine oil pollution, Technisch rapport Vogelbeschermning 10: Nederland, Zeist, [11] Fleet, D. M. & Reineking, B. Zum Seevogelsterben an der deutschen und niederlandischen Wattenmeerkuste im Februar/Marz Seevogel 20(2), pp. 63, [12] Camphuysen, C. J. Oil pollution and oiled seabirds in the Netherlands, : Signals of a cleaner sea. Sula, 11(2), special issue, pp , [13] Skov, H., Christensen, K. D. & Durinck, J. Trends in marine oil pollution in Denmark , An analysis of beached bird surveys, Miljostyrelsen Working report No. 75, 1996.