Marine Pollution Bulletin 81 (2014) 242–247
Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Baseline
Influence of proximity to an urban center in the pattern of contamination by marine debris A.S. Leite, L.L. Santos, Y. Costa, V. Hatje ⇑ Instituto de Química, Universidade Federal da Bahia, Bahia 40170-290, Brazil
a r t i c l e
i n f o
Keywords: Solid waste Contamination Salvador Regression analyses Bahia
a b s t r a c t In order to test the relationship between the occurrence of marine debris and the distance from urban areas, nine beaches in the metropolitan area of Salvador, Bahia, Brazil and the adjacent northern coast were studied. Marine debris were collected, sorted in several categories and weighed. It was observed that plastics were numerically the most abundant component of the collected debris. As expected, the beaches closest to Salvador presented the largest density of debris, with the exception of the Porto da Barra beach, which has an efficient public cleaning system and does not have any vegetation, making it difficult to accumulate solid waste. Linear regression analyses showed significant relationships between the distance from the urban center (Salvador) and the number of marine debris per m2, the total number of debris per beach (abundance), and the diversity of debris types (richness). The results showed that proximity to urban regions was a key factor in the marine debris distribution along the coast. Ó 2014 Elsevier Ltd. All rights reserved.
Marine debris represent one of the most important environmental pollutants of the XXIst century and can be considered a serious threat to sustainable use of marine and coastal resources (e.g., Goldberg, 1995; Ivar do Sul and Costa, 2007). Among marine debris, plastics deserve special attention. The versatility of these materials has led to a great increase in their use in a wide range of products over the past decades, and consequently has led to an increase in plastic marine debris. Along with plastics, the large majority of marine debris found in the environment is composed of nylon, rubber, polystyrene and foam (Spengler and Costa, 2008). These materials share important characteristics such as lightweight, durability, and buoyancy, which facilitate their transport and dispersion (de Araújo and Costa, 2006; Ivar do Sul and Costa, 2007; Ivar do Sul et al., 2011; Moore et al., 2011). Numerous studies report the negative impacts caused by marine debris, among which are deleterious effects on wildlife and habitat quality, the economy, aesthetics and even human health and safety (e.g. Derraik, 2002; Ivar do Sul and Costa, 2007). More recently Ivar do Sul and Costa (2014) critically analyzed the recent literature regarding specifically microplastics contamination and their effects on the marine biota. Although pollution by marine debris can impact remote areas, there is a high concentration and accumulation of debris in the coastal zones. Following global
⇑ Corresponding author. Current address: Dept. of Ocean Sciences, University of California Santa Cruz, Santa Cruz, USA. Tel.: +1 8314594736. E-mail address: [email protected] (V. Hatje). http://dx.doi.org/10.1016/j.marpolbul.2014.01.032 0025-326X/Ó 2014 Elsevier Ltd. All rights reserved.
trends, marine debris pollution is ubiquitous in the coast of Brazil (Hatje et al., 2013). The lack of urban planning to support high human density along the coast is primarily responsible for the improper disposal of domestic, industrial and even hospital solid and liquid waste in these areas (Buenrostro and Bocco, 2003; Sharholy et al., 2007). A review by Ivar do Sul and Costa (2007) showed that there are only a small number of studies regarding the problem of marine debris in the extensive coast of Bahia (1180 km) (Fig. 1), which represents one of the main leisure and tourism areas of Brazil. Salvador, the capital of the State, is the third biggest metropolitan area in the country, with more than 2.7 million inhabitants. Several studies showed that the urbanization and the industrial developments in the Salvador metropolitan area, including the largest petrochemical complex in the Southern hemisphere and two important ports, has resulted in the contamination of estuaries, beaches and the mangroves of the Todos os Santos Bay by metals and organic contaminants (e.g. Eça et al., 2013; Hatje and Barros, 2012; Hatje et al., 2009, 2010). Studies on marine debris, however, remain sparse for the coast of Bahia, which makes it difficult to provide conclusive arguments for policy and management action. Santos et al. (2005) realized the first semi-quantitative analyses of marine debris in the non-urbanized northern beaches of Bahia. Later, it was reported that the total number of items presented in developed and undeveloped beaches in this region was not significantly different from each other (Ivar do Sul et al., 2011). Santos et al. (2009) examined composition, quantities and distributions of marine debris along 150 km of relatively undeveloped beaches
A.S. Leite et al. / Marine Pollution Bulletin 81 (2014) 242–247
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Fig. 1. Location of studied beaches in Bahia, northeastern Brazil. PB = Porto da Barra; OND = Ondina; JA = Jardim de Alá; ART = Praia dos Artistas; JAG = Jaguaribe; ALE = Aleluia; GEN = Genipabu; ITA = Itacimirim and PF = Praia do Forte.
located South of Bahia. The latter showed that marine debris in this area were threefold higher than the amounts observed in relatively well preserved beaches located at least 60 km north of Salvador (Santos et al., 2005). It was suggested that the main source of debris was the rivers draining from populous areas and the alongshore current that flows southward along the coast (Santos et al., 2005). This is the first study that evaluated the marine debris occurrence in the exposed sandy beaches of Salvador. This study aimed to test the hypothesis that there is a negative relationship between the distance from the urban center Salvador (i.e. area with high density of buildings, resident populations and urbanized landscapes) with the abundance (absolute number of items on a beach), richness (number of categories of debris) and mass of marine debris found on beaches. The approach employed here is pioneer, and highlight the importance of this study. Nine beaches located in Salvador and in the adjacent northern shore (Fig. 1) were chosen to assess whether there is a significant difference in the quantity and type of marine debris. To choose the beaches two factors were considered, the degree of visitation and also the distance from Salvador. The beaches Porto da Barra (closest to downtown), Ondina, Jardim de Alá, Praia dos Artistas, Jaguaribe and Aleluia are located in urbanized areas of Salvador, whereas Genipabu, Itacimirim and Praia do Forte are located on the adjacent coast around 60 and 80 km North from downtown. Beaches in Salvador are intermediate to reflective (de Carvalho, 2002), whereas beaches at the northern shore are dissipative, with extensive areas of surfing, flat topography and fine-grained sand (Ivar do Sul et al., 2011). From all studied beaches, Porto da Barra is the only one protected, once it is located inside Todos os Santos Bay. The backshore of all studied beaches is occupied at least in
some degree, whereas the beaches localized close to Salvador (Porto da Barra, Ondina, Jardim de Alá, Praia dos Artistas, Jaguaribe and Aleluia) presents retaining walls. Beach selection was performed using satellite imagery to delineate transects parallel to the coastline with a length of 300 m. This transect was divided in thirty 10 m wide subtransects perpendicular the coast. Sampling was conducted in 3 transects randomly selected for each beach. The sampling dates were chosen to combine the time of the low tide with the time of the highest visitation. Sampling on the beaches was limited to the zones stretching from the low tide mark to the berm on each beach. Cables and poles were used to delimit each transect from the low-water line to its upper limit. Samples were collected during two weekends, during spring tides. All debris (>1 cm) inside each transect were collected, manually with the aid of gloves, packed in 50 L plastic bags, labeled and stored. In the laboratory, the material was separated into categories (Table 1). The classified material was counted and weighed and the richness and abundance of items were calculated according to their type. The items in the ‘‘construction materials’’ category, usually made of heavy items such as cement blocks and wood boards, had their weight estimated in the field to the nearest kg. Items made of more the one type of material (e.g., nylon line with hook), were classified as the type with the slowest decomposition rate (Araújo and Costa, 2004). Vegetation debris (i.e., seeds, roots and algae) were not collected or considered marine debris due to their natural origin. Concentration of debris was expressed as number of debris (abundance), number of debris per m2, weight of items per m2, and richness (number of categories of debris). To assess whether the distribution of these variables followed a significant gradient along the distance from downtown, linear
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Table 1 Classification of marine debris. Category
Subcategories
Plastic
Bucket, shaver, floaters, rubber, toys, DVD’s cover, pens, straws, carpet, cigarettes, dispenser, strings, tapes, bandages, packaging, toothbrush, foams, unidentifiable hard fragments, unidentifiable soft fragments, bottles, styrofoam, lighter, cable tie, tarpaulins, makeup, sticks, swab sticks, wax, cups/plates/cutlery, pegs, hair clipper, condoms, containers, cables, nylon lines, labels, stickers, bags, electronic waste, various plastic supports, caps, tubes, button Bottles, fragments Hooks, pins, chains, packaging, wires, seals, cans, foils, fragments, nails, caps Boards, pencil, fragments, toothpicks, lolly pop and ice cream sticks Packaging, tags, labels, sheets of craft paper, notebooks, napkins, newspaper, flyers, cardboard, fragments Peanuts, coal, coconut, eggs, fruits residues Fragments, rope, moistened tissues Screw anchor, pipes, concrete, spacer for grout, plaster, gardening gear, ceramics, bricks
Glass Metal Wood Paper Organic material Fabrics Construction materials
regression analysis were performed using the software STATISTIC version 8. The characteristics of the studied beaches are presented in Table 2. Jaguaribe is one of the beaches with intensive use, and it is also the one with the largest sampled area. In contrast, Praia do Forte is the beach with the smallest length and hence the smallest sampled area. A total of 7858 items were collected for a combined weight of 16 kg from a total of 9758 m2 of beaches. These numbers clearly indicate that the large majority of marine debris was very light, which facilitate the transport and dispersion of debris. Contamination levels ranged from 0.3 to 2 items m2 at Itacimirim and Ondina, respectively (Fig. 2a). In terms of debris weight, contamination levels ranged from 0.6 to 3.6 kg m2 at Itacimirim and Jardim de Alá (Fig. 2b). Plastics were numerically the most important items of the collected debris and represented 87% of all items collected (Table 3). The second largest category of solid waste was organic debris (3.8%), followed by metal (3.6%) and paper (2.4%). Packaging were numerically dominant on the plastic category (19%), followed by hard (18%) and soft fragments (9%), cigarette butts (8%), straws (7%), bottle caps (7%), sticks (6%), seals/cable ties (5%) and disposables cups, cutlery and plates (4%). There was a large incidence of plastic items related to food, which can be explained by the traditional consumption of different food types at the beach. All the visited beaches had food vendors walking around the beach and some of them have small food stalls. Additionally, small plastic items, such as cigarette butts, are not effectively removed from beaches by cleaning services, resulting in their accumulation and probably dispersion to adjacent areas (Ivar do Sul and Costa, 2007; Santos et al., 2009). The impacts of this contamination can be illustrated by the presence of small plastic debris, especially related to fisheries activities, but also cigarette butts, straws, and fragments found on the digestive tracts of Chelonia mydas and Eretmochelys imbricate collected along the Northern coast
of Bahia (Macedo et al., 2011). This problem can have serious impacts once this region represents an important feeding ground for the Chelonia mydas and nesting area for Eretmochelys imbricata (Marcovaldi and Marcovaldi, 1999). The composition of the plastic debris collected varied among the beaches (Fig. 3). The highest contamination by plastic debris occurred in Jaguaribe, Praia dos Artistas, Jardim de Alá and Ondina: four urbanized, intensely used beaches. On the contrary, Porto da Barra, one of the most famous beach in Salvador, and heavily visited by both tourists and locals alike, presented a relatively small amount of plastic and other debris (Table 3; Fig. 3). This result could be due to the efficiency of the public cleaning services of this beach, which operates twice daily, as opposed to other beaches that have a lesser cleaning frequency (Table 2). As a consequence, in Porto da Barra, the accumulation of plastics and the amount of marine debris in general is significantly smaller (p < 0.05) than in the other highly urbanized beaches (Table 3; Fig. 2a). It was observed that a number of drinks were consumed in the studied beaches. Nevertheless, aluminum cans were almost absent in marine debris with the exception of the Jardim de Alá beach that had 18 cans among the collected debris. This observation could be due to the efficient collection of aluminum cans for recycling by the local population. Brazil has a promising market for aluminum recycling, the collection step of which is traditionally exploited by the poorest people (Araújo and Costa, 2004). Fig. 2a–c shows that there is a general tendency toward decreased contamination with increased distance from downtown (i.e., from Porto da Barra towards Praia do Forte). This suggests a correlation between urbanized areas and increased marine debris contamination, as initially hypothesized. In terms of debris densities (total number of items per m2), the Porto da Barra beach was an exception to this trend. As noted earlier, this beach is cleaned twice daily, hence the time interval to accumulate marine debris is not long enough to allow the solid waste to buildup to the levels ob-
Table 2 Characteristics of sampled beaches.
Porto da Barra Ondina Jardim de Alá Praia dos Artistas Jaguaribe Aleluia Genipabu Itacimirim Praia do Forte a b c
Beach length (m)
Sampled area (m2)
Intensity of beach visitation
Public cleaning services
19 22 46 51 61 34 28 49 16
570 660 1370 1533 1820 1005 850 1470 480
Very high Very high High High High High Low Low Low
Yesa,b Yesc Yesa,c Yesc Yesa,c Yesa,c No No No
Beach cleaning employs the use of tractors. Beach cleaned twice daily. The frequency of beach cleaning is variable and does not occur daily.
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Fig. 2. Abundance, weight and richness of marine debris. Where: PB = Porto da Barra; OND = Ondina; JÁ = Jardim de Alá; ART = Praia dos Artistas; JAG = Jaguaribe; ALE = Aleluia; GEN = Genipabu; ITA = Itacimirim and PF = Praia do Forte.
Table 3 Abundance of debris in number of items collected per each studied beach. Plastic
Glass
Metal
Wood
Paper
Organic material
Construction items
Total no. of items
Porto da Barra Ondina Jardim de Alá Praia dos Artistas Jaguaribe Aleluia Genipabu Itacimirim Praia do Forte
216 1249 1771 1694 445 230 592 382 269
0 2 14 13 26 0 1 0 2
16 4 79 137 31 7 2 2 1
6 16 62 24 11 4 4 4 4
40 4 50 32 47 9 3 2 0
94 25 30 34 101 9 0 1 8
1 9 25 1 1 1 5 6 0
373 1309 2031 1935 662 260 607 397 284
Total (%)
87.1
0.7
3.6
1.7
2.4
3.8
0.6
served in other highly urbanized beaches. Moreover, this beach has no vegetation, making it more difficult to accumulate solid debris. The contamination level measured by debris densities in Ondina was almost four fold the levels observed in Porto da Barra, and it was in agreement with the expected results of the highest contamination being associated to the closeness to downtown. However, the results obtained for the debris weight (kg) and the debris weight per m2 for Ondina were substantially smaller than was expected for such a very urbanized, highly visited beach. Marine debris in Ondina were composed mainly of plastics (>95%). Small hard fragments, packaging, seals and small plastic beverage bottles caps represented more than 70% of the categories of plastic items collected. The large majority of these materials was very light; as such, the weight was not the most appropriate tool to measure the level of contamination by debris. Nevertheless, the weight of marine debris is an important variable for the management of marine debris in beaches all around the world due to the potential costs associated with cleaning public services which are usually priced in terms of ton per m2 per day. Genipabu presented relatively high weight and weight per m2. This anomalously high weight for a less-visited beach was due to the occurrence of heavy
construction materials, which represented 8% of the total items collected in this beach. The richness of the marine debris indicated that the debris across different beaches were very heterogeneous. Praia dos Artistas and Jaguaribe had almost three times the richness of Praia to Forte. In general, the higher the contamination by marine debris was (taking the density of debris into account), the higher the richness of the beach. Porto da Barra was an exception: this beach had a relatively high richness despite the relatively low level of marine debris. Apparently whereas the beach cleaning in this area has been efficient in maintaining a relatively small abundance of debris, the littering by beach users between cleaning of the beach was sufficient to keep the richness of the debris relatively high. When all the beaches were considered in the analysis, the linear regression did not show a significant correlation (p > 0.05) between proximity to an urban center and the number of debris, the number of debris per m2, the weight of items per m2, or for richness. The absence of a significant relationship between distance from downtown and debris might be the result of the influence of Porto da Barra, the closest beach to downtown, which presented an anomalous behavior compared to other urbanized beaches.
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Fig. 3. Composition of different categories of plastic debris collected in PB = Porto da Barra; OND = Ondina; JA = Jardim de Alá; ART = Praia dos Artistas; JAG = Jaguaribe; ALE = Aleluia; GEN = Genipabu; ITA = Itacimirim; and PF = Praia do Forte.
Regression analyses excluding the Porto da Barra beach indicated a significant (p < 0.05) relationship between distance from downtown and the number of debris, the number of debris per m2, and richness. The regression coefficients between the distance from downtown and the number of debris per m2 (R2 = 0.644; p < 0.05), the number of debris (R2 = 0.628; p < 0.05) and richness (R2 = 0.828; p < 0.05), showed that distance can explain the decrease in marine debris along the coast away from Salvador. However, the regression analysis indicated that the correlation between the weight of items per m2 and the distance to an urban center was not significant (p < 0.05). Two factors could have influenced this re-
sult. Firstly, due to the lightweight of most of the items, the variable weight per m2 may not have been a good proxy for the contamination by marine debris. Secondly, the Genipabu beach presented a significantly higher weight of marine debris than the other less impacted beaches, caused by the presence of a few heavy construction materials items, and so this location could have thrown off the correlation. In summary, there is a predominance of plastics among marine debris in Salvador and adjacent beaches, reflecting the wide use of plastics in the human society. The results presented here corroborated with the initial hypothesis (i.e., there is a negative relationship
A.S. Leite et al. / Marine Pollution Bulletin 81 (2014) 242–247
between the distance from the urban center Salvador with the abundance of marine debris). Regression analyses showed that there is a significant relationship between the proximity to an urban center and the contamination of the studied beaches. Public cleaning services have been efficiently keeping the level of contamination by marine debris in the Porto da Barra beach relatively low. The results observed for Port da Barra, compared to the other urbanized beaches, clearly indicated that is necessary for public administrators to deal with cleaning services in different scales and manners along a coastal region. Moreover, it would still be necessary to assess the present cleaning effort in several beaches along the coastline of Bahia to design the appropriate dimension and cost/ benefits of the cleaning services. Littering the beaches and illegally dumping domestic waste in the waters of Todos os Santos Bay and the Atlantic Ocean is still occurring, particularly at islands inside the bay that do not have an adequate public garbage collection system. Marine debris, in most cases, were lightweight, and as a result they may be transported and redistributed in different locations. Therefore, the problem of beach debris should ideally be addressed at a regional level (Debrot et al., 2013) by a marine debris action plan, which should include not only a public beach cleaning service, an adequate public garbage system collection and appropriate disposal, but also an educational program for beach users to promote the reduction of marine debris over time. The 2014 will be a benchmark in solid waste treatment in Brazil once the National Policy of Solid Residues (PNRS, 12.305/2010) will be implemented. The PNRS requires that Brazilian cities end up with their dumps until August 2014. For this it will be necessary to organize selective collection, install recycling plants and depositing the organic material in landfills. Hopefully these measures, which include sources control of solid wastes, together with an education program will improve the aesthetic quality of the Brazilian beaches and reduce marine debris contamination along the coastline of the country. Acknowledgments We would like to thank all the students that helped in the field work and in the classification of the marine debris. We also would like to thank Francisco Barros, Claire Parker and the anonymous reviewers for their comments on the draft of this manuscript. V. Hatje was supported by CNPq (239977/2012-2). References Araújo, M.C.B., Costa, M.F., 2004. Quali-quantitative analysis of the solid wastes at Tamandare Bay, Pernambuco. Brazil. Trop. Oceanogr. 32, 159–170.
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Buenrostro, O., Bocco, G., 2003. Solid waste management in municipalities in Mexico: goals and perspectives. Resour. Conserv. Recycl. 39, 251–263. de Araújo, M.C.B., Costa, M.F., 2006. Municipal Services on Tourist Beaches: Costs and Benefits of Solid Waste Collection. J. Coast. Res. 225, 1070–1075. de Carvalho, M.P., 2002. Fatores meteorológicos, oceanográficos, geológicos e urbanos relacionados à incidência de afogamentos nas praias da Costa Atlântica de Salvador. Universidade Federal da Bahia. Debrot, A.O., van Rijn, J., Bron, P.S., de León, R., 2013. A baseline assessment of beach debris and tar contamination in Bonaire, Southeastern Caribbean. Mar. Pollut. Bull. 71, 325–329. Derraik, J.G.B., 2002. The pollution of the marine environment by plastic debris: a review. Mar. Pollut. Bull. 44, 842–852. Eça, G.F., Pedreira, R.M.A., Hatje, V., 2013. Trace and major elements distribution and transfer within a benthic system: Polychaete Chaetopterus variopedatus, commensal crab Polyonyx gibbesi, worm tube, and sediments. Mar. Pollut. Bull. 74, 32–41. Goldberg, E.D., 1995. Emerging problems in the coastal zone for the twenty-first century. Mar. Pollut. Bull. 31, 152–158. Hatje, V., Barros, F., 2012. Overview of the 20th century impact of trace metal contamination in the estuaries of Todos os Santos Bay: Past, present and future scenarios. Mar. Pollut. Bull. 64, 2603–2614. Hatje, V., Bícego, M.C., de Carvalho, G.C., de Andrade, J.B., 2009. Contaminação Química. In: Hatje, V., de Andrade, J.B. (Eds.), Baía de Todos Os Santos: Aspectos Oceanográficos. EDUFBA, Salvador, pp. 244–297. Hatje, V., Costa, M.F., Cunha, L.C., 2013. Oceanografia e química: unindo conhecimentos em prol dos oceanos e da sociedade. Quim. Nova 36, 1497– 1508. Hatje, V., Macedo, S.M., de Jesus, R.M., Cotrim, G., Garcia, K.S., de Queiroz, A.F., Ferreira, S.L.C., 2010. Inorganic As speciation and bioavailability in estuarine sediments of Todos os Santos Bay, BA. Brazil. Mar. Pollut. Bull. 60, 2225–2232. Ivar do Sul, J.A., Costa, M.F., 2007. Marine debris review for Latin America and the wider Caribbean region: from the 1970s until now, and where do we go from here? Mar. Pollut. Bull. 54, 1087–1104. Ivar do Sul, J.A., Santos, I.R., Friedrich, A.C., Matthiensen, A., Fillmann, G., 2011. Plastic pollution at a sea turtle conservation area in NE Brazil: contrasting developed and undeveloped beaches. Estuaries Coasts 34, 814–823. Ivar do Sul, J.A., Costa, M.F., 2014. The present and future of microplastic pollution in the marine environment. Environmental Pollution 185, 352–364. Macedo, G.R., Pires, T.T., Rostan, G., Golderberg, D.W., Leal, C.D., Américo, F.G.N., Franke, C.R., 2011. Ingestão de resíduos antropogênicos por tartarugas marinhas no litoral norte do estado da Bahia, Brasil Anthropogenic debris ingestion by sea turtles in the northern coast of Bahia, Brazil. Ciência Rural 41, 1938–1943. Marcovaldi, M.A., Marcovaldi, G.G., 1999. Marine turtles of Brazil: the history and structure of projeto TAMAR-IBAMA. Biological Conservation 93, 35–41. Moore, C.J., Lattin, G.L., Zellers, A.F., 2011. Quantity and type of plastic debris flowing from two urban rivers to coastal waters and beaches of Southern California. Rev. Gestão Costeira Integr. 11, 65–73. Santos, I.R., Friedrich, A.C., Barreto, F.P., 2005. Overseas garbage pollution on beaches of northeast Brazil. Mar. Pollut. Bull. 50, 782–786. Santos, I.R., Friedrich, A.C., Ivar do Sul, J.A., 2009. Marine debris contamination along undeveloped tropical beaches from northeast Brazil. Environ. Monit. Assess. 148, 455–462. Sharholy, M., Ahmad, K., Vaishya, R.C., Gupta, R.D., 2007. Municipal solid waste characteristics and management in Allahabad, India. Waste Manag. 27, 490– 496. Spengler, A., Costa, M.F., 2008. Methods applied in studies of benthic marine debris. Mar. Pollut. Bull. 56, 226–230.
Contents lists available at ScienceDirect
Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul
Baseline
Influence of proximity to an urban center in the pattern of contamination by marine debris A.S. Leite, L.L. Santos, Y. Costa, V. Hatje ⇑ Instituto de Química, Universidade Federal da Bahia, Bahia 40170-290, Brazil
a r t i c l e
i n f o
Keywords: Solid waste Contamination Salvador Regression analyses Bahia
a b s t r a c t In order to test the relationship between the occurrence of marine debris and the distance from urban areas, nine beaches in the metropolitan area of Salvador, Bahia, Brazil and the adjacent northern coast were studied. Marine debris were collected, sorted in several categories and weighed. It was observed that plastics were numerically the most abundant component of the collected debris. As expected, the beaches closest to Salvador presented the largest density of debris, with the exception of the Porto da Barra beach, which has an efficient public cleaning system and does not have any vegetation, making it difficult to accumulate solid waste. Linear regression analyses showed significant relationships between the distance from the urban center (Salvador) and the number of marine debris per m2, the total number of debris per beach (abundance), and the diversity of debris types (richness). The results showed that proximity to urban regions was a key factor in the marine debris distribution along the coast. Ó 2014 Elsevier Ltd. All rights reserved.
Marine debris represent one of the most important environmental pollutants of the XXIst century and can be considered a serious threat to sustainable use of marine and coastal resources (e.g., Goldberg, 1995; Ivar do Sul and Costa, 2007). Among marine debris, plastics deserve special attention. The versatility of these materials has led to a great increase in their use in a wide range of products over the past decades, and consequently has led to an increase in plastic marine debris. Along with plastics, the large majority of marine debris found in the environment is composed of nylon, rubber, polystyrene and foam (Spengler and Costa, 2008). These materials share important characteristics such as lightweight, durability, and buoyancy, which facilitate their transport and dispersion (de Araújo and Costa, 2006; Ivar do Sul and Costa, 2007; Ivar do Sul et al., 2011; Moore et al., 2011). Numerous studies report the negative impacts caused by marine debris, among which are deleterious effects on wildlife and habitat quality, the economy, aesthetics and even human health and safety (e.g. Derraik, 2002; Ivar do Sul and Costa, 2007). More recently Ivar do Sul and Costa (2014) critically analyzed the recent literature regarding specifically microplastics contamination and their effects on the marine biota. Although pollution by marine debris can impact remote areas, there is a high concentration and accumulation of debris in the coastal zones. Following global
⇑ Corresponding author. Current address: Dept. of Ocean Sciences, University of California Santa Cruz, Santa Cruz, USA. Tel.: +1 8314594736. E-mail address: [email protected] (V. Hatje). http://dx.doi.org/10.1016/j.marpolbul.2014.01.032 0025-326X/Ó 2014 Elsevier Ltd. All rights reserved.
trends, marine debris pollution is ubiquitous in the coast of Brazil (Hatje et al., 2013). The lack of urban planning to support high human density along the coast is primarily responsible for the improper disposal of domestic, industrial and even hospital solid and liquid waste in these areas (Buenrostro and Bocco, 2003; Sharholy et al., 2007). A review by Ivar do Sul and Costa (2007) showed that there are only a small number of studies regarding the problem of marine debris in the extensive coast of Bahia (1180 km) (Fig. 1), which represents one of the main leisure and tourism areas of Brazil. Salvador, the capital of the State, is the third biggest metropolitan area in the country, with more than 2.7 million inhabitants. Several studies showed that the urbanization and the industrial developments in the Salvador metropolitan area, including the largest petrochemical complex in the Southern hemisphere and two important ports, has resulted in the contamination of estuaries, beaches and the mangroves of the Todos os Santos Bay by metals and organic contaminants (e.g. Eça et al., 2013; Hatje and Barros, 2012; Hatje et al., 2009, 2010). Studies on marine debris, however, remain sparse for the coast of Bahia, which makes it difficult to provide conclusive arguments for policy and management action. Santos et al. (2005) realized the first semi-quantitative analyses of marine debris in the non-urbanized northern beaches of Bahia. Later, it was reported that the total number of items presented in developed and undeveloped beaches in this region was not significantly different from each other (Ivar do Sul et al., 2011). Santos et al. (2009) examined composition, quantities and distributions of marine debris along 150 km of relatively undeveloped beaches
A.S. Leite et al. / Marine Pollution Bulletin 81 (2014) 242–247
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Fig. 1. Location of studied beaches in Bahia, northeastern Brazil. PB = Porto da Barra; OND = Ondina; JA = Jardim de Alá; ART = Praia dos Artistas; JAG = Jaguaribe; ALE = Aleluia; GEN = Genipabu; ITA = Itacimirim and PF = Praia do Forte.
located South of Bahia. The latter showed that marine debris in this area were threefold higher than the amounts observed in relatively well preserved beaches located at least 60 km north of Salvador (Santos et al., 2005). It was suggested that the main source of debris was the rivers draining from populous areas and the alongshore current that flows southward along the coast (Santos et al., 2005). This is the first study that evaluated the marine debris occurrence in the exposed sandy beaches of Salvador. This study aimed to test the hypothesis that there is a negative relationship between the distance from the urban center Salvador (i.e. area with high density of buildings, resident populations and urbanized landscapes) with the abundance (absolute number of items on a beach), richness (number of categories of debris) and mass of marine debris found on beaches. The approach employed here is pioneer, and highlight the importance of this study. Nine beaches located in Salvador and in the adjacent northern shore (Fig. 1) were chosen to assess whether there is a significant difference in the quantity and type of marine debris. To choose the beaches two factors were considered, the degree of visitation and also the distance from Salvador. The beaches Porto da Barra (closest to downtown), Ondina, Jardim de Alá, Praia dos Artistas, Jaguaribe and Aleluia are located in urbanized areas of Salvador, whereas Genipabu, Itacimirim and Praia do Forte are located on the adjacent coast around 60 and 80 km North from downtown. Beaches in Salvador are intermediate to reflective (de Carvalho, 2002), whereas beaches at the northern shore are dissipative, with extensive areas of surfing, flat topography and fine-grained sand (Ivar do Sul et al., 2011). From all studied beaches, Porto da Barra is the only one protected, once it is located inside Todos os Santos Bay. The backshore of all studied beaches is occupied at least in
some degree, whereas the beaches localized close to Salvador (Porto da Barra, Ondina, Jardim de Alá, Praia dos Artistas, Jaguaribe and Aleluia) presents retaining walls. Beach selection was performed using satellite imagery to delineate transects parallel to the coastline with a length of 300 m. This transect was divided in thirty 10 m wide subtransects perpendicular the coast. Sampling was conducted in 3 transects randomly selected for each beach. The sampling dates were chosen to combine the time of the low tide with the time of the highest visitation. Sampling on the beaches was limited to the zones stretching from the low tide mark to the berm on each beach. Cables and poles were used to delimit each transect from the low-water line to its upper limit. Samples were collected during two weekends, during spring tides. All debris (>1 cm) inside each transect were collected, manually with the aid of gloves, packed in 50 L plastic bags, labeled and stored. In the laboratory, the material was separated into categories (Table 1). The classified material was counted and weighed and the richness and abundance of items were calculated according to their type. The items in the ‘‘construction materials’’ category, usually made of heavy items such as cement blocks and wood boards, had their weight estimated in the field to the nearest kg. Items made of more the one type of material (e.g., nylon line with hook), were classified as the type with the slowest decomposition rate (Araújo and Costa, 2004). Vegetation debris (i.e., seeds, roots and algae) were not collected or considered marine debris due to their natural origin. Concentration of debris was expressed as number of debris (abundance), number of debris per m2, weight of items per m2, and richness (number of categories of debris). To assess whether the distribution of these variables followed a significant gradient along the distance from downtown, linear
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Table 1 Classification of marine debris. Category
Subcategories
Plastic
Bucket, shaver, floaters, rubber, toys, DVD’s cover, pens, straws, carpet, cigarettes, dispenser, strings, tapes, bandages, packaging, toothbrush, foams, unidentifiable hard fragments, unidentifiable soft fragments, bottles, styrofoam, lighter, cable tie, tarpaulins, makeup, sticks, swab sticks, wax, cups/plates/cutlery, pegs, hair clipper, condoms, containers, cables, nylon lines, labels, stickers, bags, electronic waste, various plastic supports, caps, tubes, button Bottles, fragments Hooks, pins, chains, packaging, wires, seals, cans, foils, fragments, nails, caps Boards, pencil, fragments, toothpicks, lolly pop and ice cream sticks Packaging, tags, labels, sheets of craft paper, notebooks, napkins, newspaper, flyers, cardboard, fragments Peanuts, coal, coconut, eggs, fruits residues Fragments, rope, moistened tissues Screw anchor, pipes, concrete, spacer for grout, plaster, gardening gear, ceramics, bricks
Glass Metal Wood Paper Organic material Fabrics Construction materials
regression analysis were performed using the software STATISTIC version 8. The characteristics of the studied beaches are presented in Table 2. Jaguaribe is one of the beaches with intensive use, and it is also the one with the largest sampled area. In contrast, Praia do Forte is the beach with the smallest length and hence the smallest sampled area. A total of 7858 items were collected for a combined weight of 16 kg from a total of 9758 m2 of beaches. These numbers clearly indicate that the large majority of marine debris was very light, which facilitate the transport and dispersion of debris. Contamination levels ranged from 0.3 to 2 items m2 at Itacimirim and Ondina, respectively (Fig. 2a). In terms of debris weight, contamination levels ranged from 0.6 to 3.6 kg m2 at Itacimirim and Jardim de Alá (Fig. 2b). Plastics were numerically the most important items of the collected debris and represented 87% of all items collected (Table 3). The second largest category of solid waste was organic debris (3.8%), followed by metal (3.6%) and paper (2.4%). Packaging were numerically dominant on the plastic category (19%), followed by hard (18%) and soft fragments (9%), cigarette butts (8%), straws (7%), bottle caps (7%), sticks (6%), seals/cable ties (5%) and disposables cups, cutlery and plates (4%). There was a large incidence of plastic items related to food, which can be explained by the traditional consumption of different food types at the beach. All the visited beaches had food vendors walking around the beach and some of them have small food stalls. Additionally, small plastic items, such as cigarette butts, are not effectively removed from beaches by cleaning services, resulting in their accumulation and probably dispersion to adjacent areas (Ivar do Sul and Costa, 2007; Santos et al., 2009). The impacts of this contamination can be illustrated by the presence of small plastic debris, especially related to fisheries activities, but also cigarette butts, straws, and fragments found on the digestive tracts of Chelonia mydas and Eretmochelys imbricate collected along the Northern coast
of Bahia (Macedo et al., 2011). This problem can have serious impacts once this region represents an important feeding ground for the Chelonia mydas and nesting area for Eretmochelys imbricata (Marcovaldi and Marcovaldi, 1999). The composition of the plastic debris collected varied among the beaches (Fig. 3). The highest contamination by plastic debris occurred in Jaguaribe, Praia dos Artistas, Jardim de Alá and Ondina: four urbanized, intensely used beaches. On the contrary, Porto da Barra, one of the most famous beach in Salvador, and heavily visited by both tourists and locals alike, presented a relatively small amount of plastic and other debris (Table 3; Fig. 3). This result could be due to the efficiency of the public cleaning services of this beach, which operates twice daily, as opposed to other beaches that have a lesser cleaning frequency (Table 2). As a consequence, in Porto da Barra, the accumulation of plastics and the amount of marine debris in general is significantly smaller (p < 0.05) than in the other highly urbanized beaches (Table 3; Fig. 2a). It was observed that a number of drinks were consumed in the studied beaches. Nevertheless, aluminum cans were almost absent in marine debris with the exception of the Jardim de Alá beach that had 18 cans among the collected debris. This observation could be due to the efficient collection of aluminum cans for recycling by the local population. Brazil has a promising market for aluminum recycling, the collection step of which is traditionally exploited by the poorest people (Araújo and Costa, 2004). Fig. 2a–c shows that there is a general tendency toward decreased contamination with increased distance from downtown (i.e., from Porto da Barra towards Praia do Forte). This suggests a correlation between urbanized areas and increased marine debris contamination, as initially hypothesized. In terms of debris densities (total number of items per m2), the Porto da Barra beach was an exception to this trend. As noted earlier, this beach is cleaned twice daily, hence the time interval to accumulate marine debris is not long enough to allow the solid waste to buildup to the levels ob-
Table 2 Characteristics of sampled beaches.
Porto da Barra Ondina Jardim de Alá Praia dos Artistas Jaguaribe Aleluia Genipabu Itacimirim Praia do Forte a b c
Beach length (m)
Sampled area (m2)
Intensity of beach visitation
Public cleaning services
19 22 46 51 61 34 28 49 16
570 660 1370 1533 1820 1005 850 1470 480
Very high Very high High High High High Low Low Low
Yesa,b Yesc Yesa,c Yesc Yesa,c Yesa,c No No No
Beach cleaning employs the use of tractors. Beach cleaned twice daily. The frequency of beach cleaning is variable and does not occur daily.
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Fig. 2. Abundance, weight and richness of marine debris. Where: PB = Porto da Barra; OND = Ondina; JÁ = Jardim de Alá; ART = Praia dos Artistas; JAG = Jaguaribe; ALE = Aleluia; GEN = Genipabu; ITA = Itacimirim and PF = Praia do Forte.
Table 3 Abundance of debris in number of items collected per each studied beach. Plastic
Glass
Metal
Wood
Paper
Organic material
Construction items
Total no. of items
Porto da Barra Ondina Jardim de Alá Praia dos Artistas Jaguaribe Aleluia Genipabu Itacimirim Praia do Forte
216 1249 1771 1694 445 230 592 382 269
0 2 14 13 26 0 1 0 2
16 4 79 137 31 7 2 2 1
6 16 62 24 11 4 4 4 4
40 4 50 32 47 9 3 2 0
94 25 30 34 101 9 0 1 8
1 9 25 1 1 1 5 6 0
373 1309 2031 1935 662 260 607 397 284
Total (%)
87.1
0.7
3.6
1.7
2.4
3.8
0.6
served in other highly urbanized beaches. Moreover, this beach has no vegetation, making it more difficult to accumulate solid debris. The contamination level measured by debris densities in Ondina was almost four fold the levels observed in Porto da Barra, and it was in agreement with the expected results of the highest contamination being associated to the closeness to downtown. However, the results obtained for the debris weight (kg) and the debris weight per m2 for Ondina were substantially smaller than was expected for such a very urbanized, highly visited beach. Marine debris in Ondina were composed mainly of plastics (>95%). Small hard fragments, packaging, seals and small plastic beverage bottles caps represented more than 70% of the categories of plastic items collected. The large majority of these materials was very light; as such, the weight was not the most appropriate tool to measure the level of contamination by debris. Nevertheless, the weight of marine debris is an important variable for the management of marine debris in beaches all around the world due to the potential costs associated with cleaning public services which are usually priced in terms of ton per m2 per day. Genipabu presented relatively high weight and weight per m2. This anomalously high weight for a less-visited beach was due to the occurrence of heavy
construction materials, which represented 8% of the total items collected in this beach. The richness of the marine debris indicated that the debris across different beaches were very heterogeneous. Praia dos Artistas and Jaguaribe had almost three times the richness of Praia to Forte. In general, the higher the contamination by marine debris was (taking the density of debris into account), the higher the richness of the beach. Porto da Barra was an exception: this beach had a relatively high richness despite the relatively low level of marine debris. Apparently whereas the beach cleaning in this area has been efficient in maintaining a relatively small abundance of debris, the littering by beach users between cleaning of the beach was sufficient to keep the richness of the debris relatively high. When all the beaches were considered in the analysis, the linear regression did not show a significant correlation (p > 0.05) between proximity to an urban center and the number of debris, the number of debris per m2, the weight of items per m2, or for richness. The absence of a significant relationship between distance from downtown and debris might be the result of the influence of Porto da Barra, the closest beach to downtown, which presented an anomalous behavior compared to other urbanized beaches.
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Fig. 3. Composition of different categories of plastic debris collected in PB = Porto da Barra; OND = Ondina; JA = Jardim de Alá; ART = Praia dos Artistas; JAG = Jaguaribe; ALE = Aleluia; GEN = Genipabu; ITA = Itacimirim; and PF = Praia do Forte.
Regression analyses excluding the Porto da Barra beach indicated a significant (p < 0.05) relationship between distance from downtown and the number of debris, the number of debris per m2, and richness. The regression coefficients between the distance from downtown and the number of debris per m2 (R2 = 0.644; p < 0.05), the number of debris (R2 = 0.628; p < 0.05) and richness (R2 = 0.828; p < 0.05), showed that distance can explain the decrease in marine debris along the coast away from Salvador. However, the regression analysis indicated that the correlation between the weight of items per m2 and the distance to an urban center was not significant (p < 0.05). Two factors could have influenced this re-
sult. Firstly, due to the lightweight of most of the items, the variable weight per m2 may not have been a good proxy for the contamination by marine debris. Secondly, the Genipabu beach presented a significantly higher weight of marine debris than the other less impacted beaches, caused by the presence of a few heavy construction materials items, and so this location could have thrown off the correlation. In summary, there is a predominance of plastics among marine debris in Salvador and adjacent beaches, reflecting the wide use of plastics in the human society. The results presented here corroborated with the initial hypothesis (i.e., there is a negative relationship
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between the distance from the urban center Salvador with the abundance of marine debris). Regression analyses showed that there is a significant relationship between the proximity to an urban center and the contamination of the studied beaches. Public cleaning services have been efficiently keeping the level of contamination by marine debris in the Porto da Barra beach relatively low. The results observed for Port da Barra, compared to the other urbanized beaches, clearly indicated that is necessary for public administrators to deal with cleaning services in different scales and manners along a coastal region. Moreover, it would still be necessary to assess the present cleaning effort in several beaches along the coastline of Bahia to design the appropriate dimension and cost/ benefits of the cleaning services. Littering the beaches and illegally dumping domestic waste in the waters of Todos os Santos Bay and the Atlantic Ocean is still occurring, particularly at islands inside the bay that do not have an adequate public garbage collection system. Marine debris, in most cases, were lightweight, and as a result they may be transported and redistributed in different locations. Therefore, the problem of beach debris should ideally be addressed at a regional level (Debrot et al., 2013) by a marine debris action plan, which should include not only a public beach cleaning service, an adequate public garbage system collection and appropriate disposal, but also an educational program for beach users to promote the reduction of marine debris over time. The 2014 will be a benchmark in solid waste treatment in Brazil once the National Policy of Solid Residues (PNRS, 12.305/2010) will be implemented. The PNRS requires that Brazilian cities end up with their dumps until August 2014. For this it will be necessary to organize selective collection, install recycling plants and depositing the organic material in landfills. Hopefully these measures, which include sources control of solid wastes, together with an education program will improve the aesthetic quality of the Brazilian beaches and reduce marine debris contamination along the coastline of the country. Acknowledgments We would like to thank all the students that helped in the field work and in the classification of the marine debris. We also would like to thank Francisco Barros, Claire Parker and the anonymous reviewers for their comments on the draft of this manuscript. V. Hatje was supported by CNPq (239977/2012-2). References Araújo, M.C.B., Costa, M.F., 2004. Quali-quantitative analysis of the solid wastes at Tamandare Bay, Pernambuco. Brazil. Trop. Oceanogr. 32, 159–170.
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