Lopez Bravo Impact Of Mass Tourism Case Study Majorca Island

 

Abstract

Tourism can have positive as well as negative effects on a region. It depends on thekind of tourism developed in the tourist area. In the case of this dissertation, the aimis to link the new phenomenon of tourist colonization with the growth of masstourism. For this assignment the research will take place on the island of Majorca,which, like other areas of the Mediterranean, has suffered the consequences of anuncontrolled development of tourism: cultural and environmental damages.Theories about mass tourism and its economic, physical and cultural effects, neo-colonialism and new environmental policies will be examined and linked to the caseof Majorca.The most important point of this dissertation is the study of sociocultural impacts.Among a variety of tourism effects, the research pays attention to those in relation tothe local community because the impact of mass tourism on local populations isalways significant. To collect all the information for this particular research, twodifferent questionnaires were made, one addressed to tourists and another one toresidents.The results prove that tourism development in Majorca contributed to improvingquality of life and increasing intercultural exchange, but that it also led to theconstitution of ghettos and to a relative loss of the island’s identity. These differentfactors enable to assimilate tourism to a kind of neo-colonialism.

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Long-term records of trace metal content of western Mediterranean seagrass (Posidonia oceanica) meadows: Natural and anthropogenic contributions

Authors

  • Antonio Tovar-Sánchez,

    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, Esporles, Spain
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  • Juan Serón,

    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, Esporles, Spain
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  • Núria Marbà,

    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, Esporles, Spain
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  • Jesús M. Arrieta,

    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, Esporles, Spain
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  • Carlos M. Duarte

    1. Department of Global Change Research, Instituto Mediterráneo de Estudios Avanzados, Esporles, Spain
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Abstract

[1] We discuss Al, Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents in seagrass Posidonia oceanica rhizomes from the Balearic Archipelago for the last 3 decades. Time series of metal concentration in P. oceanica were measured by dating rhizomes using retrospective procedures. The highest concentrations of Al (174.73 μg g−1), Cd (3.56 μg g−1), Cr (1.34 μg g−1), Cu (32.15 μg g−1), Pb (8.51 μg g−1), and Zn (107.14 μg g−1) were measured in meadows located around the largest and most densely populated island (Mallorca Island). There was a general tendency for Ag concentration to decrease with time (up to 80% from 1990 to 2005 in sample from Mallorca Island), which could be attributed to a reduction of the anthropogenic sources. Nickel and Zn concentrations were the unique elements that showed a consistent temporal trend in all samples, increasing their concentrations since year 1996 at all studied stations; this trend matched with the time series of UV-absorbing aerosols particles in the air (i.e., aerosols index) over the Mediterranean region (r2: 0.78, p < 0.001 for Cabrera Island), suggesting that P. oceanica could be an efficient recorder of dust events. A comparison of enrichment factors in rhizomes relative to average crustal material indicates that suspended aerosol is also the most likely source for Cr and Fe to P. oceanica.

1. Introduction

[2] Trace metals occur naturally in the ocean, mostly as colloids or absorbed onto organic and inorganic suspended particles, and tend to accumulate in living organisms and bottom sediments. While some trace metals, such as Cd, Co, Cu, Fe, Mn, Ni and Zn play a key biological role in the sea, regulating biochemical function in marine organism, they may be present in excess and, along with other metals (e.g., As, Pb), can negatively affect ecosystem health [Fraústo da Silva and Williams, 1991; Morel and Price, 2003]. Identification of the contribution of natural and/or anthropogenic main sources and pathways of trace metals entering the sea, are crucial for understanding the biogeochemical processes occurring in the coastal waters, and to effectively design and implement polices to improve the health of coastal systems.

[3] The coastal zone of the Mediterranean Sea is subject to the input of trace metal mobilized by human activities such as urbanization, tourism, agriculture, aquaculture, industries, marine traffic, etc. For example, while some metals discharged to water in the Mediterranean could be from industrial origin, such as leather and leather products (Cr, Cu, Pb and Ni), chemical and allied products (Zn), electronic and electric equipment (Pb, Cd), maritime paints and shipyard activities (Cu, Zn), sewage (Ag), etc. [Sañudo-Wilhelmy and Flegal, 1992; Patterson et al., 1998; Howe and Dobson, 2002; Wang et al., 2003; Tovar-Sánchez et al., 2004], other metals like Al, Co, Fe or Mn have mainly a lithogenic origin [Peris et al., 2008]. Atmospheric transport represents the dominant pathway for large-scale transport of trace metals (i.e., Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) to the Mediterranean Sea [Guieu et al., 1997; Migon, 2005; Guerzoni and Molinaroli, 2005], as riverine inputs are relatively low at the basin scale [Migon, 1993; Migon et al., 2002; Guerzoni and Molinaroli, 2005]. The episodic inputs of Saharan dust have been recognized as particularly important for the transport and deposition of materials to the Mediterranean Sea [Ridame and Guieu, 2002]. Over the last 20 years dust-rain events, from Saharan origin, have increased remarkably in the western Mediterranean region as a consequence of the intensification of meteorological processes (convective and advective synoptic situations) that promote the transport of aerosols from Africa toward the western Mediterranean [Quereda-Sala et al., 1996]. An increased deposition of Saharan dust to the Mediterranean may result in an increase in the input of metals of which Sahara dust is rich and may also become further enriched by scavenging during atmospheric transport (e.g., Al, Cr, Fe, Mn [Guieu et al., 1997, 2002]). Any increase in metal inputs to the Mediterranean Sea should be reflected in an increase in metal concentrations in living organisms. Sessile organisms like plants (e.g., macroalgae [Olgunoglu and Polat, 2008] and seagrasses [Roméo et al., 1995]), should therefore become excellent biological tracers of metal concentrations in the environment.

[4] Posidonia oceanica is a long-lived seagrass species with shoots living for several decades [Marbà et al., 2002], that forms meadows at depths ranging from 1 to 40 m that extend over a total estimated area of 50,000 km2 in the Mediterranean Sea [Bethoux and Copin-Móntegut, 1986]. It has been well established that P. oceanica sequester trace metals from the marine environment and that metal concentrations in their perennial tissues, which remain for decades, can be used as a proxy to trace ambient metal and radionuclide concentrations over long periods of time [Roméo et al., 1995; Pergent-Martini, 1998; Calmet et al., 1988; Baroli et al., 2001; Ancora et al., 2004; Tranchina et al., 2005a, 2005b; Lafabrie et al., 2009]. The growth of P. oceanica is highly organized, a regular number of leaves and rhizome internodes being produced at a ratio 1:1 annually at the apical rhizome meristems. Therefore, the age of different rhizomes can be estimated [Duarte et al., 1994]. These findings have highlighted the potential of this seagrass species as a biological indicator of both contamination and environmental variability. Retrospective examination of the long-term variability of elemental composition of plant tissues across regional scales can provide information about the temporal and spatial dynamics of trace metal inputs in the coastal ocean and help discriminate between local and large-scale (e.g., atmospheric) sources.

[5] While several studies have investigated trace metal concentrations in P. oceanica over the Mediterranean [e.g., Baroli et al., 2001; Ancora et al., 2004; Tranchina et al., 2005a], information on metal levels in the Balearic Archipelago is very limited. While previous works were very localized and focused to assess the degree of metal pollution in the area, our study was designed to elucidate local and regional processes affecting plant metal concentration. The goal of this study is to examine the changes of trace metal composition in rhizomes of P. oceanica along coastal waters of the Balearic Islands, western Mediterranean, over the past 3 decades to identify and evaluate the spatial and temporal trends of metal inputs. Then, we evaluate and discuss the possible link between aeolian input and seagrass chemical composition. Because industrial activity in, and nearby, the Balearic Islands is minimal, any enrichment and/or long-term trend in trace metal concentration in P. oceanica rhizomes in this region may derive from local point sources or long-distance transport, particularly atmospheric supply. We, therefore, compared metal enrichment and trends in P. oceanica rhizomes with metal concentrations in direct measurements of atmospherically suspended aerosols and long-term dynamics of atmospheric aerosols in the region.

2. Methods

[6] The Balearic archipelago (Spain) is located in the western Mediterranean Sea, and it is composed of four major (Mallorca, Menorca, Ibiza and Formentera) and other minor islands (Cabrera and islets) (Figure 1). The Balearic Islands lack significant industrial and riverine inputs and the main human pressure on the coastal water comes from urban activities. Much of the coastal zone is protected (e.g., Minorca Island was declared a Biosphere Reserve in 1993, while Cabrera and small surrounded islets were declared a Spanish national park in 1991). These coastal waters support very extensive P. oceanica meadows, growing above iron-poor biogenic carbonate sediments.

[7] Posidonia oceanica was sampled during August 2005 to September 2005 and August 2006 to October 2006 in 51 meadows at 3–18 m depth along the coast of the Balearic Islands (Figure 1). At each station, SCUBA divers collected up to three old orthotropic (vertically growing) rhizomes holding standing leaves. Samples were thoroughly rinsed in ambient seawater, stored in polyethylene bags and frozen. In the laboratory leaves, leaf sheaths and epiphytes were removed from rhizomes. After rinsing with ultrapure water to remove fine sediments particles, rhizomes were carefully cut (using a ceramic knife) in segments of 1 cm of length, corresponding to 1 lepidochronological year period of growth [Marbà and Duarte, 1997]. Previous studies indicated that average vertical rhizome growth of P. oceanica along the Balearic Islands was 8.2 ± 0.14 mm yr−1 (N. Marbà and C. M. Duarte, unpublished manuscript, 2010). Each rhizome segment, previously dried at 60°C for 24 h and weighted, was digested in high-pressure Teflon vessels using a mixture of high-purity acids (suprapur, Merck) HNO3 (67%) + HCl (13%) + ultrapure water (20%) [Duarte et al., 1995]. Digested samples were transferred into acid cleaned polypropylene tubes and diluted 1:4 (v/v) with ultrapure water. Metal concentrations (Al, Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined by ICP-AES (Perkin Elmer ICP-AES Optima 5300 DV). Procedural blanks were obtained from acid medium as described above for rhizomes. Detection limits, calculated as three times the standard deviation of the blanks values, were in ng g−1: Ag = 0.09, Al = 0.31, Cd = 0.16, Co = 0.15, Cr = 0.19, Cu = 2.96, Fe = 0.50, Mn = 0.01, Ni = 0.54, Pb = 0.15 and Zn = 1.63. The accuracy of the analytical procedure was checked using a standard reference material (sea lettuce Ulva lactuca, CRM 279; Community Bureau of Reference) with recoveries ranging from 93% for Pb to 104% for Ni of certified and indicative values. The trace metal composition during the life span of P. oceanica rhizomes (up to 3 decades) was examined for each lepidochronological year (i.e., approximately October to October) in samples from stations 1 to 25. In other cases (from station 26 to station 51), duplicated or triplicate rhizomes were analyzed in two fractions, one corresponding to the 3 youngest lepidochronological years and the other to the rest of rhizome.

[8] Sampling of aerosol was carried out during a cruise on board the R/V García del CID in June–July 2006 across the Mediterranean Sea. Samples of coarse (>20 μm) suspended aerosols were collected at six stations (latitude N–longitude E; station 1: 38.9033–4.8025; station 2: 38.3086–8.0950; station 3: 37.8845–10.6443; station 4: 37.7626–7.3435; station 5: 38.1211–4.5328; Figure 1) onto an acid-washed cellulose filter (Whatman 41) in a high-volume collector (MCV: CAV-A/HF). A microwave acid digestion procedure [Pekney and Davidson, 2005] followed by ICP-AES was used to measure total trace metal levels in those aerosol filters (Al, Cr, Fe, Mn, Ni, Pb, Cu, and Zn).

[9] The total annual index of atmospheric aerosols was estimated by remote sensing over the Balearic Islands (http://toms.gsfc.nasa.gov/aerosols/aerosols_v8.html). According to the NASA, the Total Ozone Mapping Spectrometer (TOMS) aerosol index is defined as: “a measure of how much the wavelength dependence of backscattered UV radiation from an atmosphere containing aerosols (Mie scattering, Rayleigh scattering, and absorption) differs from that of a pure molecular atmosphere (pure Rayleigh scattering)” (http://toms.gsfc.nasa.gov/aerosols/aerosols_v8.html). This index is related to aerosol optical depth, and indicates the amount of aerosols (e.g., dust, volcanic ash, and smoke) that absorb ultraviolet (UV) radiation in the atmosphere. The aerosol index is calculated daily by using a retrieval algorithm [Torres et al., 1998, 2002] based on the absorbance measurements (331–360 nm) done by the Earth Probe TOM (Total Ozone Mapping Spectrometer) instrument onboard the Aura satellite system. Because TOMs have been experiencing instrument problems, the aerosol index from 2001 onward should be considered only approximate. Air mass origins for the cruise samples were established using the NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory Model (HYSPLIT) [Draxler and Rolph, 2003].

[10] Because metal concentrations along rhizomes exhibited wide temporal fluctuations, we used median values to characterize the metal composition of each station. Differences in P. oceanica metal concentration across islands were statistically tested using Analysis of Variance, and differences between paired islands identified with Tukey-Kramer test. The magnitude of temporal fluctuations in P. oceanica metal concentrations was quantified using the coefficient of variation (CV). Significant temporal shifts in P. oceanica metal (e.g., Ag) concentration among islands were tested using t test. We used cross correlation analysis to demonstrate the coupling between average temporal trends in Zn and Ni for each island and atmospheric aerosol index despite the existence of time lags in seagrass response. Metal concentrations were calculated with respect to dry weight.

3. Results

[11] The length of orthotropic rhizomes studied ranged from 4.5 to 32 cm, which represent between 4 (station 11) and 29 (station 22) years old. Hence metal contents were analyzed in a total of 292 rhizomes sections, the oldest formed in 1976. Median, minimum and maximum metal (Al, Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) concentrations in rhizomes collected in 51 meadows around the Balearic Islands (Figure 1) are shown in Table S1 (available as auxiliary material). The lowest median metal contents characterized Formentera (Al: 1.32 μg g−1, Cd: 0.41 μg g−1, Cu: 4.31 μg g−1, Fe: 15.85 μg g−1, Mn: 1.30 μg g−1 and Pb: 0.05 μg g−1) and Ibiza (Cr: 0.01 μg g−1, Ni: 0.97 μg g−1 and Zn: 4.02 μg g−1) meadows. Although the lowest concentrations of Ag and Co were found, occasionally, in rhizomes from stations 17 (1.24 μg g−1, Mallorca) and 42 (0.02 μg g−1, Menorca), respectively, very low concentrations were also measured in samples from Formentera (e.g., St 7: 2.43 μg g−1 Ag and St 28: 0.04 μg g−1 Co). The highest concentrations of Al (174.73 μg g−1), Cd (3.56 μg g−1), Cr (1.34 μg g−1), Cu (32.15 μg g−1), Pb (8.51 μg g−1) and Zn (107.14 μg g−1) were measured in meadows located around the Mallorca Island. On the other hand, the highest median concentrations of Ag (27.58 μg g−1), Fe (624.09 μg g−1) and Mn (31.66 μg g−1) were measured at the north of Menorca Island (station 43).

[12] Except for Al, concentrations of all metals in P. oceanica varied significantly among islands (ANOVA with comparisons for all pairs using Tukey-Kramer test; Table S2). Concentrations of Cu, Ag and Mn showed the highest spatial variations (ANOVA and Tukey-Kramer test, p < 0.001; Table S2).

[13] Interannual fluctuations of metal concentrations in P. oceanica rhizomes were broadly variable, CV: Al (19–129%), Cd (18–69%), Co (27–140%), Cr (16–231%), Cu (12–96%), Fe (26–102%), Mn (6–71%), Pb (40–258%) (Figures 2–4 and Figures S1–S3). After excluding values at station 14 in Mallorca Island, where concentrations were generally higher for almost all analyzed elements, probably due to a local source, the lowest temporal variations in metal concentrations were found around the smallest and less impacted islands, Cabrera (CV: 57, 31, 65 and 55%, for Al, Cd, Fe and Mn, respectively) and Formentera (CV: 53, 51% for Co and Cu, respectively). Only Cr (CV: 85%) and Pb (CV: 69%) showed the lowest variations at Ibiza and Mallorca, respectively. No temporal trends of these metals concentrations were observed in the studied meadows.

[14] Ag, Ni and Zn concentrations also showed interannual changes along the rhizomes and variations among different meadows, thus the highest variations of Ag (CV: 97%) were shown at Cabrera, while Ni (CV: 165%) and Zn (CV: 113%) varied greatly at Ibiza Island. A temporal sustained decreasing trend of Ag concentration was observed in most rhizomes from Mallorca and Ibiza islands since year 1995 (Figures 2 and S1). A t test indicated that Ag contents in the rhizome were significantly lower (p < 0.0001) after 1995 (5.44 ± 0.30 versus 9.75 ± 0.55 and 6.66 ± 0.37 versus 10.80 ± 0.49 at Mallorca and Ibiza, respectively). Conversely, Nickel and Zn concentrations in all P. oceanica rhizomes increased since year 1996 at all studied stations (Figures 4 and S3), although the largest increase was detected since 2000–2002.

4. Discussion

4.1. P. oceanica Trace Metal Characterization in the Balearic Archipelago

[15] Chemical composition of P. oceanica over the Balearic archipelago shows the lowest metal contents in plants from Formentera and Cabrera islands. These islands are the smallest and less inhabited islands of the archipelago and consequently those supporting the least anthropogenic pressure on their coastal system. In contrast, the highest concentrations were measured in meadows located around Mallorca and Menorca islands, the largest and most densely populated islands of the archipelago. The metal enrichment in rhizomes from station 43 (Menorca) cannot easily be attributed to anthropogenic causes since this meadow is located in a marine reserve where no sewage or submarine outfalls were identified.

[16] Mean values of metal concentrations in rhizomes collected in the Balearic Archipelago are in agreement with ranges reported for other areas in the Mediterranean Sea, except for Co whose concentrations (0.22–0.86 μg g−1) were 1 order of magnitude lower than reported for other Mediterranean areas (1.7–12.1 μg g−1) (Table 1). Iron concentrations were often observed to be below the threshold (100 μg g−1 Fe) for iron sufficiency in angiosperms, as expected for carbonate sediments away from anthropogenic Fe inputs [Duarte et al., 1995], thus suggesting that Fe supply may often limit the growth of P. oceanica in the Balearic Islands [Holmer et al., 2005; Marbà et al., 2007]. The finding of low Fe concentration in rhizomes agrees with previous observations relative to leaves of P. oceanica from the same region [Fourqurean et al., 2007]. To our knowledge this is the first study that measures Ag and Al concentrations in P. oceanica, therefore comparison with other Mediterranean regions is not possible.

1Mallorca, Spain8.28 ± 5.8440.79 ± 92.41.11 ± 0.770.44 ± 0.670.51 ± 0.6613.62 ± 7.98161.90 ± 281.237.53 ± 10.2510.21 ± 11.794.26 ± 4.3535.61 ± 32.89
 Menorca, Spain16.08 ± 10.5343.25 ± 92.41.13 ± 0.450.22 ± 0.250.31 ± 0.2915.22 ± 5.15190.92 ± 199.359.25 ± 11.817.05 ± 13.830.65 ± 1.1549.32 ± 25.60
 Ibiza, Spain9.05 ± 4.2752.42 ± 46.391.03 ± 0.480.29 ± 0.280.36 ± 0.3211.51 ± 5.98184.76 ± 144.929.61 ± 6.827.11 ± 10.42.65 ± 3.0228.00 ± 28.58
 Formentera, Spain4.66 ± 2.2919.28 ± 15.290.96 ± 0.330.37 ± 0.250.24 ± 0.25

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