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Floating megalitter in the eastern Mediterranean
Volume 19/Number 1/January 1988 gestions for an Improved Method Based on Measurement of Individual Components. Bull. Environm. Contain. Toxicol. 25, 956964. Duinker, J. C., Shultz, D. E. & Petrick, G. (Submitted) Multidimensional gas chromatography with electron capture detection of toxic congeners in PCB mixtures. Anal. Chem. Jensen, S. & Sundstrrm, G. (1974). Structures and levels of most chlorobiphenyls in two technical PCB products and in human adipose tissue. A m b i o 3, 70-76. Leece, B., Denomme, M. A., Towner, R., Li, S. M. A. & Safe, S. (1985). Polychlorinated Biphenyls: Correlation between in Vivo and in Vitro Quantitative Structure-Activity Relationships (QSARs). J. Toxicology and Environmental Health, 16,379-388. Mullin. M. D., Pochini, C. M., MeCrindle, S., Romkes, M., Safe, S. H. & Safe, L. M. (1984). High-Resolution PCB Analysis: Synthesis and Chromatographic Properties of all 209 PCB Congeners. Environ. Sci. Technol. 1 8 , 4 6 8 - 4 7 6 .
Safe, S., Bandiera, S., Sawyer, T., Robertson, L., Safe, L., Parkinson, A., Thomas, P. E., Ryan, D. E., Reik, L. M., Levin, W., Denomme, M. A.
& Fujita, T. (1985). PCBs: Structure-Function Relationships and Mechanism of Action. Environmental Health Perspectives 60, 47-56.
Schomburg, G., Weeke, E, MiiUer, E & Oreans, M. (1982). Multidimensional gas-chromatography(MDC) in capillary columns using double oven instruments and a newly designed coupling piece for monitor detectionafter pre-separation. Chromatographia 16, 87-91. Schomburg, G., Husman, H. & Hiibinger, E. (1985). Multidimensional separation of isomeric species of chlorinated hydrocarbonssuch as PCB, PCDD and PCDE J. High Res. Chrom. and Chrom. comm. 8, 395-400. Schulte, E. & Acker, L. (1974). Identifizierung und Metabolisierbarkeit von polychlorierten Biphenylen. Naturwissenschaften 61, 79-80. Sissons, D. & Welti, D. J. (1971). Structural identification of PCBs in commercial mixtures by GLC, NMR and MS. J. Chromatog~ 60, 15-32. Twinstra, L. G. M. T., Traag, W. A. & Keukens, H. J. (1980). Quantitative determination of individual chlorinated biphenyls in milk fat by splitless glass capillary gas chromatography. Z Assoc. Off Anal, Chem. 63,952-958.
MarinePollutionBulletin,Volume19, No. l, pp. 25-28, 1988.
0025-326X/88$3.00+0.00 © 1988PergamonJournalsLtd.
PrintedinGreatBritain.
Floating Megalitter in the Eastern Mediterranean FLOYD W. McCOY Lamont-Doherty Geological Observatory of Columbia University Palisades, N. Y 10964; and Associated Scientists at Woods Hole, Woods Hole, Mass. 02543, USA
Concentrations of floating megalitter--floating debris that is large enough for sighting by eye or with binoculars--were measured from a ship in a small area (8.3 km 2) of the eastern Mediterranean Sea over a 22 day period. Suggested concentrations are on the order of 0.012 g m -2, based upon a limited data base, but are close to values determined elsewhere in the Mediterranean. If these values are representative of regional concentrations, then as many as 3.6 × 106 objects may be afloat per day as megalitter in the Mediterranean Sea. Most of the observed megalitter was plastic debris; all of the litter was man-made.
Few quantitative data are available on the amounts of floating debris in the ocean, especially synoptic data on large-sized macroscopic material. Debris that is large enough to be discernible to the eye or through binoculars, thus with dimensions measured in decimetres or metres, is here defined as megalitter. Megalitter may originate from both natural and man-made sources, thus tree stumps, logs, large tar balls and aggregates, steel barrels, plastic cartons, all floating at the sea surface, would be considered megalitter. Reports of floating megalitter have been made from all major oceans and seas, suggesting that megalitter may form a significant component of oceanic pollutants both on the sea surface and at depth. Few quantitative data on floating megalitter concentrations are available, however. Most reports of floating debris are based
upon qualitative or reconnaissance observations collected along transects between ports or oceanographic stations. Noticeable accumulations of megalitter have been described from the Atlantic Ocean (Davies, 1987; van Dolah et al., 1980; Morris, 1980a,b; Colton et al., 1974; Heyerdahl, 1971). Pacific Ocean (Shaw & Mapes, 1979; Wong et al. 1976), Bering Sea (Feder et al., 1978), Caribbean Sea (Sea Education Assoc., 1983), Mediterranean Sea (Saydam et al. 1985; Oren, 1970), as well as the Indian Ocean and South China Sea (Price & Nelson-Smith, 1986; U N E E 1982). Megalitter is concentrated along shipping routes (Horsman, 1982; Oren, 1970), in fishing areas (Merrel, 1980, 1984), offshore areas popular for recreational activities (Cundell, 1973), off sewage plants (Hays & Cormons, 1974), offshore and downcurrent from major industrial areas (Shiber, 1982; Gregory, 1977), even near areas of political unrest and civil war (Shiber, 1979). The source of this debris is often obvious; its dispersal and longevity as megalitter is not known. Synoptic data are lacking, measurements made in defined survey areas over a period of days or weeks, to assess the temporal variability and concentration levels of megalitter. Such measurements are needed particularly in mid-ocean areas remote from known input sources--it is essential to forming good baseline criteria for understanding dispersal, longevity and regional concentrations of floating megalitter. During the summer of 1986, the Italian research vessel Bannock conducted marine geological studies in a small area of the eastern Mediterranean Sea (Fig. 1). 25
Marine
40°N
38 °
Mediterranean
36 °
i~;:~ STUDYAREA 34 °
Se~z
32 °
16°E
18"
20 °
22 °
24 °
26 °
30 °
F i g . I . l n d e × m a p l o c a t i n g s t u d y area.
Data on floating megalitter were gathered because 1. the ship would remain here for three weeks, thus allowing synoptic measurements over an extended period of time; 2. the area was remote from major shipping lanes, thus remote from sources of man-made debris for a better evaluation of regional concentrations of floating megalitter; and 3. previous expeditions in this area had always encountered floating debris.
Study Area and Survey Operations The study area was located between about 34°04 ' to 34*22' N and 19"43' to 20*06' E, an area of approximately 1419 km 2 (414 square nautical miles) (Fig. 1). Twenty-two days were spent in this area, divided into two segments: a first segment of 7 days, followed by a 4 day transit in and out of Catania, Sicily, then a second segment of 15 days. Observations were made at 22 stations and twice while underway. Surface currents in this part of the Mediterranean during the summer flow to the east with velocities on the order of 0.2-0.5 m s -~ (Lacombe & Tchernia, 1972). Wind speeds and directions, and estimated seastate during observation periods are listed in Table 1. The dominant wind direction was from the north, typical for this part of the Mediterranean during July and August. Wind velocity, measured with on-board anemometers, averaged between 3 and 5 m s -I, with a maximum of 12 m s -1. Sea-state, estimated using visual criteria, was usually between 1 and 2-3. Navigation used Loran C with periodic fixes by satellite. While underway, Loran C fixes were obtained every 5 rain; while on station, a minimum of two Loran C fixes were made, although more usually were obtained. Ship's drift while on-station varied from negligible to 2 knots in strong winds. Ship's speed was 10 knots while underway, and 2 knots while manoeuvring.
Observation Techniques Observations were made in mid-afternoon during the
first 7-day segment of the cruise, then as close to local noon (+1 GMT) as possible for the 15-day, second 26
Pollution
Bulletin
segment of the cruise. At least one, usually two, searches were made by slowly sweeping around the ship in a full circle both by eye and by using binoculars (7×50) from the ship's bridge (approximately 10 m above sea-level). To test the representativeness of concentration levels calculated from one observation period with concentrations at other times during daylight, additional searches were made twice in the morning and twice in the afternoon during two stations. There was little variability of concentration levels between these five observation periods, and it is assumed that the concentrations derived from the single observation period are indicative of a 24 h period. The effective range for observations was estimated to be about a 180 m radius away from the ship. No counts of megalitter were made within the 60 m radius closest to the ship; anything floating here was presumed to be of local derivation (a regrettable, but common, circumstance on too many research vessels). Accordingly, the area searched daily for floating megalitter was defined by a 120 m radius that is 60 m away from the ship, in a 60 m long (one ship's-length) by 360 ° sweep from the ship; the total area for visual observations is estimated at about 8.3 km 2. Estimates at sea for these distances were made by comparison to one ship's length. Three categories for particle sizes of megalitter were established: small with dimensions equal to or less than 0.5 m (A' in Table 1), large with a dimension of 1 m or more ('C' in Table 1), and a size intermediate between these two ('B' in Table 1). Drift of debris derived from the ship, and the sector it occupied, was carefully noticed prior to making observations. Any floating debris in this sector, extending out through the complete search area, was not counted. There is a bias to noticing and identifying such debris. Objects like plastics have a high centre of buoyancy resulting in a high freeboard: because they float higher in the water, they are more easily seen. White and light-coloured objects, or metallic objects, contast with the sea-surface and have increased visibility: they reflect the sun and are more easily seen. Floating junk was most visible during flat calm (sea state= 1) conditions or with a broad swell which would lift debris into sight. Sea states of 3 or greater were difficult because of white caps. Only a few ships were sighted each day, usually small freighters on local trade routes rather than large tankers and bulk carriers. No ships were sighted during the 2 h preceding and following the observation periods.
Results and Conclusions The dominant type of floating megalitter noted were small plastic containers less than 0.5 m in size, or with a volume of about 1 I. (Table 1). Larger plastic objects of up to 1 m in size, such as large-volume containers and sheets (tarps), were less common. Wood was sighted as crates and as milled planks. The single metal object sighted appeared to be a large (1 gal. or 4.5 1.) can. One large wad of paper was identified. Higher concentra-
Volume 19/Number 1/January 1988
TABLE 1 C o n c e n t r a t i o n s of F l o a t i n g Megalitter in the E a s t e r n M e d i t e r r a n e a n Sea. Station
Position lat.=N long=E
Date
BA-2
3 4 17.(/ 2 0 01.0
u/w
Comments"
Timer
Sea-state
Wind:[: ms-'
No. a n d T y p e of F l o a t i n g Debris{} A B
7/17
1500
1-2
- -+
P
-
3 4 16.0 2 0 01.0
7/18
1500
2-3
10 N
PP
-
BA-7
34 17.9 20 00.7
7/19
1500
2
4 NNW
P
X
BA-I1
3 4 17.5 20 00.6
7/20
1500
2-3
8 SE
-
-
u/w
35 5 0 . 0 17 4 0 . 0
7/21
1500
.
2
34 22.0 20 02.9
7/26
1200
3
12 N
-
-
-
5
3 4 20.5 20 01.0
7/27
1200
2
4NE
P
-
-.
8
3 4 19.0 2 0 01.5
7/28
1200
1
<1N
M
-
-
11
3 4 19.3 2O 01.5
7/29
1230
1
0
X
-
-
14
3 4 22.1 20 05.8
7/30
1200
2
2 NNE
-
-
-
17
3 4 14.6 19 55.0
7/31
1200
1
1-2N
-
W
-
18
3 4 16.2 20 04.O
8/1
1300
2-3
7 NE
-
-
-
white-caps
21
3 4 15.8 19 4 7 . 0
8/2
1200
3
12 N
X/P?
-
-
white-caps
23
3 4 14.2 19 4 2 . 2
8/3
1300
4
- - N
p?
.
25
3 4 I5.6 19 5 6 . 7
8/4
1200
2
2 NNW
PPP
-
-
27
34 0 5 . 8 19 53.6
8/5
0800
1-2
1 NW
-
-
-
27
34 05.8 19 53.6
8/5
1030
1-2
1NW
-
W
-
28
34 05.2 19 5 3 . 0
8/5
1230
1-2
2 NW
P
-
29
34 05.1 19 5 2 . 7
8/5
1500
1-2
2NW
P
-
29
3 4 05.1 19 5 2 . 7
8/5
1730
1-2
2 NW
-
-
31
34 05.4 19 5 2 . 6
8/6
1230
2
5 NNW
-
-
35
3 4 04.1 t9 50.4
8/7
1200
1-2
2N
P
37
3 4 15.8 19 57.5
8/8
0900
0-I
0
P
38
3 4 16.6 20 00.2
8/8
1130
0-1
0
P
-
38
34 16.6 20 00.2
8/8
1300
0-1
0
P
-
39
3 4 21.8 20 03.9
8/8
1430
0-1
0
-
-
39
3 4 21.8 20 03.9
8/8
1730
0-1
0
-
41
3 4 13.9 19 4 2 . 3
8/9
1200
1
1 N
-
mo day t
.
.
manoeuvfing
in transit
.
.
.
white-caps
white-caps
.
2 0 s e c t o r not visible
-
-
P
*u/w=underway. t T i m e is local time ( G M T + 1). :[:Wind d i r e c t i o n (N, etc.) is the d i r e c t i o n the w i n d is b l o w i n g from, o r the u p w i n d a z i m u t h . +Two d a s h e s ( n o data). §Size o f o b j e c t s < 7 2 m = A , '/2-1 m = B , > 1 m = C ; M = m e t a l , P = p l a s t i c , W = w o o d , X = o t h e r ( p a p e r , cloth, etc.) o r unidentified; a single s y m b o l = o n e o b j e c t sighted, a d o u b l e s y m b o l = t w o o b j e c t s sighted, etc.; o n e d a s h i n d i c a t e s n o t h i n g o b s e r v e d . " T h e n o t a t i o n ' w h i t e - c a p s ' i n d i c a t e s s e a s u r f a c e r o u g h n e s s p r e v e n t e d careful o b s e r v a t i o n s . 27
Marine Pollution Bulletin
tions were noticed after strong winds from the north. In general an average of one floating object was sighted each day in this small sector of the eastern Mediterranean Sea. Statistical treatment of such a small database is not feasible. But if this is at all typical, considering the Mediterranean Sea has an area of 2.97 x 106 km 2 (Emelyanov & Shimkus, 1986) and that daily observations from the Bannock encompassed an area of 8.3 k m 2, then perhaps 3.6 x 10 6 objects may be afloat per day as megalitter in the entire Mediterranean Sea. This is clearly a broad extrapolation whose accuracy remains to be tested, and is applicable only to the summer of 1986 when these observations were made. Assuming a bulk density for floating megalitter of 0.8 gm ml -t an average particle-size with dimensions equal to or less than 0.5 m (size range A' in Table 1), then a sea-surface area concentration of floating debris of lX 105 g 8.3 km -2, or 0.012 g m -2, is inferred. The question remains whether such a concentration could be considered an average for the entire sea. Because the survey area where these observations were made is well away from expected sources of debris such as major shipping lanes or large cities, and the area is not within a pronounced gyre of surface-water circulation where megalitter would be concentrated, this calculated concentration may be a realistic approximation. For comparison, this concentration value is close to values determined off Turkey by Saydam et al., (1985) for floating megalitter composed of nylon-net fragments, 0.012-0.003 g m -2 (maximum values for coastal and offshore areas, respectively), and composed of fragments of plastic, wood and cigarette butts, 0.001-0.0007 g m -2 (maximum values for coastal and offshore areas, respectively). Benzhitsky & Polikarpov (1976) reported concentration values for large (up to 13 cm; size category A', Table 1) oil aggregates in surface waters of the Ionian Sea of 0.01 g m -z, and off the African coast of 0.007 g m -2. The source of debris reported upon in this study could not be determined. Higher numbers of floating materials noticed following strong northerly winds suggests a derivation from the north. Surface currents would bring debris from the Straits of Sicily, from the west. In both cases, this is also the direction of both the nearest major shipping lanes and the industrial areas of the Mediterranean borderlands. Clearly the extrapolation of this small dataset to such a large sea is tenuous. More observations are needed, observations that are quantitative, that are repeated on some systematic basis, and that are made in areas where physical factors affecting floating pollutant concentrations and transport are understood.
28
Observations during the first segment of the cruise were by G. Bearzi and B. Cavallom of the Universita di Padova; their help, in addition to the cooperation extended by D. Bregant of the lstituto Talassografico Trieste, is appreciated. Assistance from colleagues at the Universita di Milano, in par'acular M. B. Cita, as well as the cooperation from the officers and crev, of the R / V Bannock remains the essential ingredient in a long and successful research programme in the Mediterranean Sea. Review by W. R_ Wright was helpful.
Benzhitsky, A. G. & Polikarpov, G. G. (1976). Distribution of oil aggregates in the surface layer of the Mediterranean Sea in AprilJune 1974. Okeanologiya 16, 87-90. Colton, J. B.. 1,CTapp, F. D. & Burns, B. R. (1974). Plastic particles in surface waters: of the northwestern Atlantic. Science 185,491-497. Cundell, A. M. ~1973). Plastic materials accumulating in Narragansett Bay. Mar. Pc;;:a. Bull. 4, 187-188. Davies, G. (19,,i-). Abysmal litter. Mar. Pollut. Bull. 18, 59-60. Emelyanov, E M. & Shimkus, K. M. (1986). Geochemistry and Sedimentolo~- of the Mediterranean Sea. D. Reidel, Dordrecht. Feder, H. M., Jev, ett, S. C. & Hilsinger, J. R. (1978). Man-made debris on the Berin~ Sea floor. Mar. Pollut. Bull. 9, 52-53. Gregory, M. R. 119771. Plastic pellets on New Zealand beaches. Mar. Pollut. Bull. 8.82-84. Hays, H. and Cormons, G. (1974). Plastic particles found in Tern pellets, on coastal beaches and at factory sites. Mar. Pollut. Bull. 5, 44-46. Heyerdahl, H. ¢:971). Atlantic Ocean pollution and biota observed by the U(Ra)expeditions. Biol. Conservation 3, 164-167. Horsman, P. \] (1982). The amount of garbage pollution from merchant sl'::-s. Mar. Polha. Bull. 13, 167-169. Lacombe, H. & Tchernia, P. (19721. Caracteres hydrologiques et circulation d ~ eaux in Mediterranee. In The Mediterranean Sea (D. J. Stanley, ed.~. pp. 25-36. Dowden, Hutchinson and Ross, Stroudsburg. Merrell, T. R. ~!980). Accumulation of plastic litter on beaches of Amchitka Is~znd, Alaska. Mar. Envi~ Res. 3, 171-184. Merrell, T. R. (1984). A decade of change in nets and plastic litter from fisheries offAiaska. Mar. Pollut. Bull. 15,378-384. Morris, R. J. 1"980a). Floating plastic debris in the Mediterranean. Mar. Pollut. Bull. 11,125. Morris, R. J. (igS0b). Plastic debris in the surface waters of the South Atlantic. Mc,~ Pollut. Bull. 11,164-166. Oren, O. H. (19-01. Tar pollution of the Levant basin. Mar. Pollut. Bull. 1,149-150. Price, A. R. G. & Nelson-Smith, A. (1986). Observations on surface pollution in :he Indian Ocean and South China Sea during the Sinbad voyage (I980-811. Mar. Pollut. Bull. 17, 60-62. Saydam, C., S~'._~oglu, I., Sakarya, M. & Yilmas, A. (1985). Dissolved/ dispersed pe:roleum hydrocarbons, suspended sediment, plastic, pelagic tar mad other litter in the north-eastern Mediterranean. 7th Workshop cz Pollution of the Mediterranean, Lucerne, Intl. Comm. Sci. Explora~on Med. Sea, Monaco, 509-518. Sea Education Assoc. (1983). Cruise Report W-67, Scientific activities undertaken z'c'oard R/V Westward. Shaw, D. G. & Mapes, G. A. (19791. Surface circulation and the distribution cf pelagic tar and plastic. Mar. Polha. Bull. 10, 160-162. Shiber, J. B. ( l ~-9). Plastic pellets on the coast of Lebanon. Ma~ Pollut. Bull. 10, 2S-3~1. Shiber, J. G. I;9<2). Plastic pellets on Spain's "Costa del Sol' beaches. Mar. Pollut. 3"dl. 13,409-412. UNEP (19821. Oi1 pollution control in the east African region. UNEP Regional Se~ Reports and Studies No. 10. van Dolah, R. F_ Burrell, V. G. & West, S. B. (1980). The distribution of pelagic tars ~'ad plastics in the south Atlantic bight. Mar. Pollut. Bull. 11,352-356. Wong, C. 8.. Green, W. R. & Cremey, W. J. (1976). Distribution and source of tar .zn the Pacific Ocean. Mar. Pollut. Bull. 7,102-105.
Safe, S., Bandiera, S., Sawyer, T., Robertson, L., Safe, L., Parkinson, A., Thomas, P. E., Ryan, D. E., Reik, L. M., Levin, W., Denomme, M. A.
& Fujita, T. (1985). PCBs: Structure-Function Relationships and Mechanism of Action. Environmental Health Perspectives 60, 47-56.
Schomburg, G., Weeke, E, MiiUer, E & Oreans, M. (1982). Multidimensional gas-chromatography(MDC) in capillary columns using double oven instruments and a newly designed coupling piece for monitor detectionafter pre-separation. Chromatographia 16, 87-91. Schomburg, G., Husman, H. & Hiibinger, E. (1985). Multidimensional separation of isomeric species of chlorinated hydrocarbonssuch as PCB, PCDD and PCDE J. High Res. Chrom. and Chrom. comm. 8, 395-400. Schulte, E. & Acker, L. (1974). Identifizierung und Metabolisierbarkeit von polychlorierten Biphenylen. Naturwissenschaften 61, 79-80. Sissons, D. & Welti, D. J. (1971). Structural identification of PCBs in commercial mixtures by GLC, NMR and MS. J. Chromatog~ 60, 15-32. Twinstra, L. G. M. T., Traag, W. A. & Keukens, H. J. (1980). Quantitative determination of individual chlorinated biphenyls in milk fat by splitless glass capillary gas chromatography. Z Assoc. Off Anal, Chem. 63,952-958.
MarinePollutionBulletin,Volume19, No. l, pp. 25-28, 1988.
0025-326X/88$3.00+0.00 © 1988PergamonJournalsLtd.
PrintedinGreatBritain.
Floating Megalitter in the Eastern Mediterranean FLOYD W. McCOY Lamont-Doherty Geological Observatory of Columbia University Palisades, N. Y 10964; and Associated Scientists at Woods Hole, Woods Hole, Mass. 02543, USA
Concentrations of floating megalitter--floating debris that is large enough for sighting by eye or with binoculars--were measured from a ship in a small area (8.3 km 2) of the eastern Mediterranean Sea over a 22 day period. Suggested concentrations are on the order of 0.012 g m -2, based upon a limited data base, but are close to values determined elsewhere in the Mediterranean. If these values are representative of regional concentrations, then as many as 3.6 × 106 objects may be afloat per day as megalitter in the Mediterranean Sea. Most of the observed megalitter was plastic debris; all of the litter was man-made.
Few quantitative data are available on the amounts of floating debris in the ocean, especially synoptic data on large-sized macroscopic material. Debris that is large enough to be discernible to the eye or through binoculars, thus with dimensions measured in decimetres or metres, is here defined as megalitter. Megalitter may originate from both natural and man-made sources, thus tree stumps, logs, large tar balls and aggregates, steel barrels, plastic cartons, all floating at the sea surface, would be considered megalitter. Reports of floating megalitter have been made from all major oceans and seas, suggesting that megalitter may form a significant component of oceanic pollutants both on the sea surface and at depth. Few quantitative data on floating megalitter concentrations are available, however. Most reports of floating debris are based
upon qualitative or reconnaissance observations collected along transects between ports or oceanographic stations. Noticeable accumulations of megalitter have been described from the Atlantic Ocean (Davies, 1987; van Dolah et al., 1980; Morris, 1980a,b; Colton et al., 1974; Heyerdahl, 1971). Pacific Ocean (Shaw & Mapes, 1979; Wong et al. 1976), Bering Sea (Feder et al., 1978), Caribbean Sea (Sea Education Assoc., 1983), Mediterranean Sea (Saydam et al. 1985; Oren, 1970), as well as the Indian Ocean and South China Sea (Price & Nelson-Smith, 1986; U N E E 1982). Megalitter is concentrated along shipping routes (Horsman, 1982; Oren, 1970), in fishing areas (Merrel, 1980, 1984), offshore areas popular for recreational activities (Cundell, 1973), off sewage plants (Hays & Cormons, 1974), offshore and downcurrent from major industrial areas (Shiber, 1982; Gregory, 1977), even near areas of political unrest and civil war (Shiber, 1979). The source of this debris is often obvious; its dispersal and longevity as megalitter is not known. Synoptic data are lacking, measurements made in defined survey areas over a period of days or weeks, to assess the temporal variability and concentration levels of megalitter. Such measurements are needed particularly in mid-ocean areas remote from known input sources--it is essential to forming good baseline criteria for understanding dispersal, longevity and regional concentrations of floating megalitter. During the summer of 1986, the Italian research vessel Bannock conducted marine geological studies in a small area of the eastern Mediterranean Sea (Fig. 1). 25
Marine
40°N
38 °
Mediterranean
36 °
i~;:~ STUDYAREA 34 °
Se~z
32 °
16°E
18"
20 °
22 °
24 °
26 °
30 °
F i g . I . l n d e × m a p l o c a t i n g s t u d y area.
Data on floating megalitter were gathered because 1. the ship would remain here for three weeks, thus allowing synoptic measurements over an extended period of time; 2. the area was remote from major shipping lanes, thus remote from sources of man-made debris for a better evaluation of regional concentrations of floating megalitter; and 3. previous expeditions in this area had always encountered floating debris.
Study Area and Survey Operations The study area was located between about 34°04 ' to 34*22' N and 19"43' to 20*06' E, an area of approximately 1419 km 2 (414 square nautical miles) (Fig. 1). Twenty-two days were spent in this area, divided into two segments: a first segment of 7 days, followed by a 4 day transit in and out of Catania, Sicily, then a second segment of 15 days. Observations were made at 22 stations and twice while underway. Surface currents in this part of the Mediterranean during the summer flow to the east with velocities on the order of 0.2-0.5 m s -~ (Lacombe & Tchernia, 1972). Wind speeds and directions, and estimated seastate during observation periods are listed in Table 1. The dominant wind direction was from the north, typical for this part of the Mediterranean during July and August. Wind velocity, measured with on-board anemometers, averaged between 3 and 5 m s -I, with a maximum of 12 m s -1. Sea-state, estimated using visual criteria, was usually between 1 and 2-3. Navigation used Loran C with periodic fixes by satellite. While underway, Loran C fixes were obtained every 5 rain; while on station, a minimum of two Loran C fixes were made, although more usually were obtained. Ship's drift while on-station varied from negligible to 2 knots in strong winds. Ship's speed was 10 knots while underway, and 2 knots while manoeuvring.
Observation Techniques Observations were made in mid-afternoon during the
first 7-day segment of the cruise, then as close to local noon (+1 GMT) as possible for the 15-day, second 26
Pollution
Bulletin
segment of the cruise. At least one, usually two, searches were made by slowly sweeping around the ship in a full circle both by eye and by using binoculars (7×50) from the ship's bridge (approximately 10 m above sea-level). To test the representativeness of concentration levels calculated from one observation period with concentrations at other times during daylight, additional searches were made twice in the morning and twice in the afternoon during two stations. There was little variability of concentration levels between these five observation periods, and it is assumed that the concentrations derived from the single observation period are indicative of a 24 h period. The effective range for observations was estimated to be about a 180 m radius away from the ship. No counts of megalitter were made within the 60 m radius closest to the ship; anything floating here was presumed to be of local derivation (a regrettable, but common, circumstance on too many research vessels). Accordingly, the area searched daily for floating megalitter was defined by a 120 m radius that is 60 m away from the ship, in a 60 m long (one ship's-length) by 360 ° sweep from the ship; the total area for visual observations is estimated at about 8.3 km 2. Estimates at sea for these distances were made by comparison to one ship's length. Three categories for particle sizes of megalitter were established: small with dimensions equal to or less than 0.5 m (A' in Table 1), large with a dimension of 1 m or more ('C' in Table 1), and a size intermediate between these two ('B' in Table 1). Drift of debris derived from the ship, and the sector it occupied, was carefully noticed prior to making observations. Any floating debris in this sector, extending out through the complete search area, was not counted. There is a bias to noticing and identifying such debris. Objects like plastics have a high centre of buoyancy resulting in a high freeboard: because they float higher in the water, they are more easily seen. White and light-coloured objects, or metallic objects, contast with the sea-surface and have increased visibility: they reflect the sun and are more easily seen. Floating junk was most visible during flat calm (sea state= 1) conditions or with a broad swell which would lift debris into sight. Sea states of 3 or greater were difficult because of white caps. Only a few ships were sighted each day, usually small freighters on local trade routes rather than large tankers and bulk carriers. No ships were sighted during the 2 h preceding and following the observation periods.
Results and Conclusions The dominant type of floating megalitter noted were small plastic containers less than 0.5 m in size, or with a volume of about 1 I. (Table 1). Larger plastic objects of up to 1 m in size, such as large-volume containers and sheets (tarps), were less common. Wood was sighted as crates and as milled planks. The single metal object sighted appeared to be a large (1 gal. or 4.5 1.) can. One large wad of paper was identified. Higher concentra-
Volume 19/Number 1/January 1988
TABLE 1 C o n c e n t r a t i o n s of F l o a t i n g Megalitter in the E a s t e r n M e d i t e r r a n e a n Sea. Station
Position lat.=N long=E
Date
BA-2
3 4 17.(/ 2 0 01.0
u/w
Comments"
Timer
Sea-state
Wind:[: ms-'
No. a n d T y p e of F l o a t i n g Debris{} A B
7/17
1500
1-2
- -+
P
-
3 4 16.0 2 0 01.0
7/18
1500
2-3
10 N
PP
-
BA-7
34 17.9 20 00.7
7/19
1500
2
4 NNW
P
X
BA-I1
3 4 17.5 20 00.6
7/20
1500
2-3
8 SE
-
-
u/w
35 5 0 . 0 17 4 0 . 0
7/21
1500
.
2
34 22.0 20 02.9
7/26
1200
3
12 N
-
-
-
5
3 4 20.5 20 01.0
7/27
1200
2
4NE
P
-
-.
8
3 4 19.0 2 0 01.5
7/28
1200
1
<1N
M
-
-
11
3 4 19.3 2O 01.5
7/29
1230
1
0
X
-
-
14
3 4 22.1 20 05.8
7/30
1200
2
2 NNE
-
-
-
17
3 4 14.6 19 55.0
7/31
1200
1
1-2N
-
W
-
18
3 4 16.2 20 04.O
8/1
1300
2-3
7 NE
-
-
-
white-caps
21
3 4 15.8 19 4 7 . 0
8/2
1200
3
12 N
X/P?
-
-
white-caps
23
3 4 14.2 19 4 2 . 2
8/3
1300
4
- - N
p?
.
25
3 4 I5.6 19 5 6 . 7
8/4
1200
2
2 NNW
PPP
-
-
27
34 0 5 . 8 19 53.6
8/5
0800
1-2
1 NW
-
-
-
27
34 05.8 19 53.6
8/5
1030
1-2
1NW
-
W
-
28
34 05.2 19 5 3 . 0
8/5
1230
1-2
2 NW
P
-
29
34 05.1 19 5 2 . 7
8/5
1500
1-2
2NW
P
-
29
3 4 05.1 19 5 2 . 7
8/5
1730
1-2
2 NW
-
-
31
34 05.4 19 5 2 . 6
8/6
1230
2
5 NNW
-
-
35
3 4 04.1 t9 50.4
8/7
1200
1-2
2N
P
37
3 4 15.8 19 57.5
8/8
0900
0-I
0
P
38
3 4 16.6 20 00.2
8/8
1130
0-1
0
P
-
38
34 16.6 20 00.2
8/8
1300
0-1
0
P
-
39
3 4 21.8 20 03.9
8/8
1430
0-1
0
-
-
39
3 4 21.8 20 03.9
8/8
1730
0-1
0
-
41
3 4 13.9 19 4 2 . 3
8/9
1200
1
1 N
-
mo day t
.
.
manoeuvfing
in transit
.
.
.
white-caps
white-caps
.
2 0 s e c t o r not visible
-
-
P
*u/w=underway. t T i m e is local time ( G M T + 1). :[:Wind d i r e c t i o n (N, etc.) is the d i r e c t i o n the w i n d is b l o w i n g from, o r the u p w i n d a z i m u t h . +Two d a s h e s ( n o data). §Size o f o b j e c t s < 7 2 m = A , '/2-1 m = B , > 1 m = C ; M = m e t a l , P = p l a s t i c , W = w o o d , X = o t h e r ( p a p e r , cloth, etc.) o r unidentified; a single s y m b o l = o n e o b j e c t sighted, a d o u b l e s y m b o l = t w o o b j e c t s sighted, etc.; o n e d a s h i n d i c a t e s n o t h i n g o b s e r v e d . " T h e n o t a t i o n ' w h i t e - c a p s ' i n d i c a t e s s e a s u r f a c e r o u g h n e s s p r e v e n t e d careful o b s e r v a t i o n s . 27
Marine Pollution Bulletin
tions were noticed after strong winds from the north. In general an average of one floating object was sighted each day in this small sector of the eastern Mediterranean Sea. Statistical treatment of such a small database is not feasible. But if this is at all typical, considering the Mediterranean Sea has an area of 2.97 x 106 km 2 (Emelyanov & Shimkus, 1986) and that daily observations from the Bannock encompassed an area of 8.3 k m 2, then perhaps 3.6 x 10 6 objects may be afloat per day as megalitter in the entire Mediterranean Sea. This is clearly a broad extrapolation whose accuracy remains to be tested, and is applicable only to the summer of 1986 when these observations were made. Assuming a bulk density for floating megalitter of 0.8 gm ml -t an average particle-size with dimensions equal to or less than 0.5 m (size range A' in Table 1), then a sea-surface area concentration of floating debris of lX 105 g 8.3 km -2, or 0.012 g m -2, is inferred. The question remains whether such a concentration could be considered an average for the entire sea. Because the survey area where these observations were made is well away from expected sources of debris such as major shipping lanes or large cities, and the area is not within a pronounced gyre of surface-water circulation where megalitter would be concentrated, this calculated concentration may be a realistic approximation. For comparison, this concentration value is close to values determined off Turkey by Saydam et al., (1985) for floating megalitter composed of nylon-net fragments, 0.012-0.003 g m -2 (maximum values for coastal and offshore areas, respectively), and composed of fragments of plastic, wood and cigarette butts, 0.001-0.0007 g m -2 (maximum values for coastal and offshore areas, respectively). Benzhitsky & Polikarpov (1976) reported concentration values for large (up to 13 cm; size category A', Table 1) oil aggregates in surface waters of the Ionian Sea of 0.01 g m -z, and off the African coast of 0.007 g m -2. The source of debris reported upon in this study could not be determined. Higher numbers of floating materials noticed following strong northerly winds suggests a derivation from the north. Surface currents would bring debris from the Straits of Sicily, from the west. In both cases, this is also the direction of both the nearest major shipping lanes and the industrial areas of the Mediterranean borderlands. Clearly the extrapolation of this small dataset to such a large sea is tenuous. More observations are needed, observations that are quantitative, that are repeated on some systematic basis, and that are made in areas where physical factors affecting floating pollutant concentrations and transport are understood.
28
Observations during the first segment of the cruise were by G. Bearzi and B. Cavallom of the Universita di Padova; their help, in addition to the cooperation extended by D. Bregant of the lstituto Talassografico Trieste, is appreciated. Assistance from colleagues at the Universita di Milano, in par'acular M. B. Cita, as well as the cooperation from the officers and crev, of the R / V Bannock remains the essential ingredient in a long and successful research programme in the Mediterranean Sea. Review by W. R_ Wright was helpful.
Benzhitsky, A. G. & Polikarpov, G. G. (1976). Distribution of oil aggregates in the surface layer of the Mediterranean Sea in AprilJune 1974. Okeanologiya 16, 87-90. Colton, J. B.. 1,CTapp, F. D. & Burns, B. R. (1974). Plastic particles in surface waters: of the northwestern Atlantic. Science 185,491-497. Cundell, A. M. ~1973). Plastic materials accumulating in Narragansett Bay. Mar. Pc;;:a. Bull. 4, 187-188. Davies, G. (19,,i-). Abysmal litter. Mar. Pollut. Bull. 18, 59-60. Emelyanov, E M. & Shimkus, K. M. (1986). Geochemistry and Sedimentolo~- of the Mediterranean Sea. D. Reidel, Dordrecht. Feder, H. M., Jev, ett, S. C. & Hilsinger, J. R. (1978). Man-made debris on the Berin~ Sea floor. Mar. Pollut. Bull. 9, 52-53. Gregory, M. R. 119771. Plastic pellets on New Zealand beaches. Mar. Pollut. Bull. 8.82-84. Hays, H. and Cormons, G. (1974). Plastic particles found in Tern pellets, on coastal beaches and at factory sites. Mar. Pollut. Bull. 5, 44-46. Heyerdahl, H. ¢:971). Atlantic Ocean pollution and biota observed by the U(Ra)expeditions. Biol. Conservation 3, 164-167. Horsman, P. \] (1982). The amount of garbage pollution from merchant sl'::-s. Mar. Polha. Bull. 13, 167-169. Lacombe, H. & Tchernia, P. (19721. Caracteres hydrologiques et circulation d ~ eaux in Mediterranee. In The Mediterranean Sea (D. J. Stanley, ed.~. pp. 25-36. Dowden, Hutchinson and Ross, Stroudsburg. Merrell, T. R. ~!980). Accumulation of plastic litter on beaches of Amchitka Is~znd, Alaska. Mar. Envi~ Res. 3, 171-184. Merrell, T. R. (1984). A decade of change in nets and plastic litter from fisheries offAiaska. Mar. Pollut. Bull. 15,378-384. Morris, R. J. 1"980a). Floating plastic debris in the Mediterranean. Mar. Pollut. Bull. 11,125. Morris, R. J. (igS0b). Plastic debris in the surface waters of the South Atlantic. Mc,~ Pollut. Bull. 11,164-166. Oren, O. H. (19-01. Tar pollution of the Levant basin. Mar. Pollut. Bull. 1,149-150. Price, A. R. G. & Nelson-Smith, A. (1986). Observations on surface pollution in :he Indian Ocean and South China Sea during the Sinbad voyage (I980-811. Mar. Pollut. Bull. 17, 60-62. Saydam, C., S~'._~oglu, I., Sakarya, M. & Yilmas, A. (1985). Dissolved/ dispersed pe:roleum hydrocarbons, suspended sediment, plastic, pelagic tar mad other litter in the north-eastern Mediterranean. 7th Workshop cz Pollution of the Mediterranean, Lucerne, Intl. Comm. Sci. Explora~on Med. Sea, Monaco, 509-518. Sea Education Assoc. (1983). Cruise Report W-67, Scientific activities undertaken z'c'oard R/V Westward. Shaw, D. G. & Mapes, G. A. (19791. Surface circulation and the distribution cf pelagic tar and plastic. Mar. Polha. Bull. 10, 160-162. Shiber, J. B. ( l ~-9). Plastic pellets on the coast of Lebanon. Ma~ Pollut. Bull. 10, 2S-3~1. Shiber, J. G. I;9<2). Plastic pellets on Spain's "Costa del Sol' beaches. Mar. Pollut. 3"dl. 13,409-412. UNEP (19821. Oi1 pollution control in the east African region. UNEP Regional Se~ Reports and Studies No. 10. van Dolah, R. F_ Burrell, V. G. & West, S. B. (1980). The distribution of pelagic tars ~'ad plastics in the south Atlantic bight. Mar. Pollut. Bull. 11,352-356. Wong, C. 8.. Green, W. R. & Cremey, W. J. (1976). Distribution and source of tar .zn the Pacific Ocean. Mar. Pollut. Bull. 7,102-105.