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Marine Pollution Bulletin 58 (2009) 341–350
Contents lists available at ScienceDirect
Marine Pollution Bulletin
journal homepage: www.elsevier.com/locate/marpolbul
Floating marine debris in fjords, gulfs and channels of southern Chile
Iván A. Hinojosa a, Martin Thiel a,b,*
a
b
Universidad Católica del Norte, Biologia Marina, Larrondo 1281, Coquimbo, Chile
Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Coquimbo, Chile
a r t i c l e
i n f o
Keywords:
Floating marine debris
Waste
Litter
Plastics
Styrofoam
Sea-based
Aquaculture
Chile
a b s t r a c t
Floating marine debris (FMD) is reported from all oceans. The bulk of FMD are plastics, which due to their
longevity cause multiple negative impacts on wildlife and environment. Identifying the origins of FMD
(land- or sea-based) is important to take the necessary steps to diminish their abundance. Using ship surveys we examined the abundance, composition and distribution of FMD during the years 2002–2005 in
the fjords, gulfs and channels of southern Chile. Abundances of FMD were relatively high compared with
other studies, ranging from 1 to 250 items km2. The majority (80%) of FMD was composed of styrofoam (expanded polystyrene), plastic bags and plastic fragments. Styrofoam, which is intensively used
as floatation device by mussel farms, was very abundant in the northern region but rarely occurred in
the southern region of the study area. Food sacks from salmon farms were also most common in the
northern region, where 85% of the total Chilean mussel and salmon harvest is produced. Plastic bags,
which could be from land- or sea-based sources, were found throughout the entire study area. Our results
indicate that sea-based activities (mussel farming and salmon aquaculture) are responsible for most FMD
in the study area. In order to reduce FMDs in the environment, in addition to stronger legislation and
identification of potential sources, we suggest environmental education programs and we encourage
public participation (e.g. in beach surveys and clean-ups).
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
Any manufactured or processed solid waste material that enters
the marine environment from any source is defined as marine debris (Coe and Rogers, 1997). Marine debris can be classified according to their origin, as either coming from land sources (e.g. coastal
users or through rivers) or from oceanic sources (e.g. from ships or
offshore installations) (Williams et al., 2005). Some debris sink
immediately to the sea floor while others might remain afloat for
extended periods (weeks to several months). There is a wealth of
studies on floating marine debris (FMD), and its composition and
abundance on sandy beaches has been intensively studied (e.g.
Edyvane et al., 2004). However, before stranding on a beach,
FMD is at the mercy of surface currents and winds, complicating
inferences about their origins. Commonly, indirect evidence is used
to trace FMD back to their potential sources. Specific characteristics of floating debris, such as e.g. fisheries articles, brand names,
or material types provide hints of their origin (Ribic, 1998; Sheavly
and Register, 2007).
FMD is found in all oceans and coastal waters (Gregory and
Andrady, 2003; Ivar do Sul and Costa, 2007). Higher abundances
of FMD are often reported from principal shipping routes and
* Corresponding author. Address: Universidad Católica del Norte, Biologia
Marina, Larrondo 1281, Coquimbo, Chile. Tel.: +56 51 209939; fax: +56 51 209812.
E-mail address: [email protected] (M. Thiel).
0025-326X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.marpolbul.2008.10.020
coastal waters adjacent to major urban regions (Matsumura and
Nasu, 1997; Thiel et al., 2003) and/or are related to the principal
ocean current systems (Kubota, 1994; Shiomoto and Kameda,
2005). The principal component of FMD is plastics (Pruter, 1987;
Derraik, 2002). For example, plastic pieces comprise 80% of floating debris in the Mediterranean Sea (Morris, 1980), and in the SE
Pacific off the Chilean coast (Thiel et al., 2003). Yamashita and Tanimura (2007), using a neuston surface net, found that >55% of the
stations surveyed presented fragments of plastic products and
plastic sheets in the Kuroshio Current in NW Pacific Ocean.
The impact of FMD on marine wildlife and invertebrate fauna
has been well documented and can be classified in three categories: (i) entanglement (e.g. Boren et al., 2006), (ii) ingestion (e.g.
Ryan, 2008), and (iii) transport of associated fauna (e.g. Barnes
and Milner, 2005). In the same way, FMD can have negative effects
on human activities (e.g. entanglement of lines or fishing nets in
ship propellers, Williams et al., 2005). During the 1970s and 80s
an accelerated increase of the amounts of FMD was reported in
the world oceans (see Pruter, 1987), and growing environmental
concerns led to improved legislation, e.g. The International Convention for the Prevention of Pollution from Ships (MARPOL) or
other international conventions (see e.g. Bean, 1987). Possibly as
a result of these regulations and better infrastructure of waste disposal in some areas of the world’s oceans a stabilization and/or
reduction in the amounts of FMD has been suggested (Johnson,
1994; Vlietstra and Parga, 2002; Edyvane et al., 2004) as well as
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changes in the composition (Ryan, 2008). For example, a recent
study showed that the total amount of plastics in seabird stomachs
did not change during the past 30 years, but the proportion of
industrial plastics decreased (Vlietstra and Parga, 2002; Ryan,
2008). This led Ryan (2008) to suggest that industry initiatives
have been effective in reducing losses of small plastic debris.
Several studies have shown that a large proportion of FMD has
land-based sources, but sea-based (e.g. fishery) activities also contribute FMD in some regions (Gregory, 2004). During the past two
decades the numbers of sea-based installations such as aquaculture, wind parks, oil/gas platforms or marinas in coastal waters
have increased, and this tendency is expected to continue. These
installations might be responsible for additional deposition of marine debris in the future. For example, oil/gas platforms produce
similar amounts of domestic waste as land-based activities (Pruter,
1987), and parts of this might be lost during regular platform
operations.
In recent decades, in southern Chile (Internal Sea of Chiloé and
Chonos Archipelago), an explosive development of salmon and
mussel aquaculture has occurred contributing 99% of the national
production (occupying the 2nd and 4th place of world salmon
and mussel production, respectively, FAO, 2007; SERNAPESCA,
2007). In parallel, concerns about possible environmental impacts
of these sea-based activities on marine ecosystems have been
growing (e.g. Soto and Norambuena, 2004; Buschmann et al.,
2006). Potential impacts of aquaculture are caused by increased
nutrient supply (for salmons see e.g. Carroll et al., 2003; for bivalves see e.g. Dowd, 2005), introduction of chemical substances
(Miranda and Zemelman, 2002) and escape and invasion of exotic
species (Correa and Gross, 2008). In addition, aquaculture installations use many floating items to maintain their structures at the
sea surface and therefore might also occasionally release FMD into
the environment.
In the present study we evaluated the abundance, spatial distribution and composition of FMD throughout four years in the Internal Sea of Chiloé and Chonos Archipelago in order to identify their
dynamics and possible origins. Based on our results we offer recommendations to reduce the amounts of FMD in the study area.
2. Materials and methods
We surveyed floating marine debris (FMD) during seven oceanographic cruises that were carried out in the Internal Sea of Chiloé
and Los Chonos Archipelago (southern Chile) during the years
2002–2005 (Fig. 1). The cruises were part of the research program
CIMAR-Fiordo (Cruceros de Investigacion Marina en Áreas Remotas). Each year, two research cruises took place, one during austral
winter (July/August) and the other during late austral spring
(November). Each cruise lasted 25 days covering a large area in
southern Chile (Fig. 1) with predetermined oceanographic stations.
The southern study region (Los Chonos Archipelago) was covered
during the years 2002 and 2003, while the northern region (Internal Sea of Chiloé) was covered in 2004 and 2005 (Fig. 1). The central zone ‘‘Boca del Guafo” was covered during all years.
During daytime navigation, a skilled observer surveyed the sea
surface from the bridge of the research vessel (4 m above sea level, ship velocity 10 knots.). Using a handheld GPS and binoculars, the observer recorded all FMD on one side of the ship,
taking notes of their position and distance to the vessel. The distance of FMD to the vessel was estimated using known distances
(e.g. width or length of vessel). In order to estimate the abundance
of FMD, we used the strip transect method, which is based on the
Fig. 1. Study area in southern Chile and surveyed transects. Map on the left shows urban localities with >1000 inhabitants (INE, 2005).
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I.A. Hinojosa, M. Thiel / Marine Pollution Bulletin 58 (2009) 341–350
number of items seen and the width and transect length. Abundance of FMD was calculated using the following equation:
D ¼ N=ððW=1000Þ LÞ
where N is the number of items of FMD, W the distance perpendicular to the transect (in meters, see below for details), and L the total
length (in km) of the transect. Since a preliminary examination of
343
the data set showed that the number of observed items decreased
substantially at distances >20 m from the vessel, we herein used a
conservative measure and only considered a transect width W of
20 m from the vessel. Applying this conservative measure we ensured that the abundance of floating items is not underestimated
due to overlooked items. The transect length corresponds to the
typical distance between CIMAR stations (10–40 km). Seven catego-
Fig. 2. Average abundance ± SD (items km2) of floating marine debris in the different sectors of the study area. Gray areas in the left figures indicate time periods when the
respective sectors were not surveyed. Areas were subdivided into sectors according to salinity and bathymetry. The Boca del Guafo (BG) is dominated by Subantarctic water,
the gulfs and islands in the Internal Sea of Chiloé and the channels in the Chonos Archilepelago are characterized by the Modified Subantarctic water, and the inner fjords by
Estuarine water (Silva and Guzmán, 2006) (for further details of names of the sectors see Table 2).
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I.A. Hinojosa, M. Thiel / Marine Pollution Bulletin 58 (2009) 341–350
ries of FMD were distinguished: styrofoam (expanded polystyrene,
particles of 2–60 cm diameter); plastic fragments (fragments of various non-identified hard and soft plastic items >2 cm); plastic bags
(typical plastic grocery bags), lines (principally polypropylene
ropes), food sacks (food sacks commonly used in salmon aquaculture), wood tables (wood boards used for construction or transport
crates), and others (glass and plastic bottles, tetra pack, plastic cup,
cigarette boxes, etc.).
In order to compare the spatio-temporal distribution of FMD,
each study region was subdivided into smaller geographic units
(sectors, see right side of Fig. 2). Geographic subdivision was based
on predominant salinities and bathymetry (Silva and Palma, 2006).
The inner fjords were dominated by Estuarine waters, the sectors
of the gulfs and islands in the northern region and the channels
in the southern region are characterized by the Modified Subantarctic water, and the Boca del Guafo by Subantarctic water (Silva
and Guzmán, 2006). Individual 2-way or 3-way ANOVAs were used
to examine whether total abundance of FMD in the study area depended on year, season or sectors (see below). Since factorial ANOVA requires equal replication (Zar, 1999), we pooled adjacent
transects or we subdivided the longest transects in a sector in order to have five replicate transects per sector.
In the Internal Sea of Chiloé we ran a 3-way ANOVA, with the
factors year (2004 and 2005), season (winter and spring) and sector. For the sector Boca del Guafo we had data from all survey
years, which permitted us to run a 2-way ANOVA with the factors
year and season, including all winter and spring surveys for the
years 2003–2005. For Los Chonos Archipelago, we conducted a 2way ANOVA with the factors season (spring 2002, winter and
spring 2003) and sector (year was not included as a factor because
winter surveys were only available for one year). In general, normality was tested using Kolmogorov-Smirnov and homogeneity
of variances using Levene tests (Snedecor and Cochran, 1989). In
order to achieve equal variances all data were transformed using
Log (x + 1), but in some cases the normality test failed. In all
analyses we used the criterium suggested by Conover (1980),
applying ANOVAs to both the parametric and rank-transformed
data, and we presented the former when results were consistent.
Tukey tests were used to test for specific differences within a significant source of variation (Zar, 1999).
3. Results
Floating marine debris (FMD) was found throughout the entire study area (Fig. 2). Abundances of FMD were substantially
higher in the northern region of the study area (Internal Sea of
Chiloé) than in the southern region (Los Chonos Archipelago).
The highest abundances were found in Northern Fjordland Zone
(NFZ), Golfo de Ancud (GA), and Islas Desertores (ID), with abundances typically ranging from 10 to 50 items km2. The maximum abundance (with 240 items km2) was found in Islas
Desertores in winter 2005. Abundances in Golfo del Corcovado
(GC) were intermediate, ranging from 5 to 30 items km2. Relatively low abundances of FMD were present in the sector Boca
del Guafo (BG), never exceeding 10 items km2 (Fig. 2). In Los
Chonos Archipelago, abundances were even lower, and in 68%
of the transects we observed no FMD. Throughout the southern
channel zones (MZ, KCZ, DCZ) the average abundances were relatively low (<6 items km2). Slightly higher abundances were
found in the Southern Fjordland Zone (SFZ) with 10 items km2
(Fig. 2).
The Factorial ANOVAs on the abundance of FMD indicated that
significant differences in the Internal Sea of Chiloé were due to year
(higher abundances during 2005) and sectors (Table 1). In general,
the abundance of FMDs showed no clear seasonal pattern. Abundances were highest throughout the year in Islas Desertores (ID)
and Golfo de Acud (GA) (Fig. 2). In the sector Boca del Guafo, year
and season had a significant effect, with an increasing abundance
of FMD during the years 2004 and 2005, mainly during spring
(Table 1). In Los Chonos Archipelago no significant differences
between surveys and sectors were found.
Diverse types of FMD occurred throughout the entire study
area (Table 2, Fig. 3). More than 80% of the FMD was made up
of styrofoam (expanded polystyrene), plastic bags and plastic
fragments. In the Internal Sea of Chiloé, styrofoam was the most
abundant item (Fig. 3), exceeding abundances of >10 items km2
during several surveys in all sectors (NFZ, GA, ID), occasionally
even >50 items km2 in Golfo de Ancud and Islas Desertores
(Table 2). The highest styrofoam abundance with >200 items
km2 was observed in the sector Islas Desertores. In the Internal
Sea of Chiloé, plastic fragments and plastic bags reached abundances of about 1–5 items km2 (Table 2). Here, food sacks were
also observed in relatively high proportions (Fig. 3), principally
during spring 2004. A diverse assemblage of FMD was found in
the sector Golfo de Corcovado, where only styrofoam reached
comparatively high values of >20 items km2 during one survey
(Table 2). All categories of FMD were occasionally found in Boca
del Guafo, but never in very high abundances. Interestingly, in
this sector plastic bags and food sacks showed a tendency to be
more frequent and abundant during the years 2004 and 2005
Table 1
ANOVA result for effects of survey year, season and sector on the abundance of floating marine debris (FMD) in the (a) Internal Sea of Chiloé, (b) Boca del Guafo, and (c) Los Chonos
Archipelago.
General area
Factors
DF
MS
F
P
(a)
Internal Sea of Chiloé
Year
Season
Sector
Year* season
Year* sector
Season* sector
Year* season* sector
Error
1
1
4
1
4
4
4
80
1.805
0.158
2.554
0.688
0.257
0.841
0.687
0.345
5.225
0.458
7.392
1.991
0.744
2.434
1.989
0.025
0.5
<0.000
0.162
0.565
0.054
0.104
(b)
Boca del Guafo
Year
Season
Year*, season
Error
2
1
2
24
0.519
0.581
0.387
0.135
3.85
4.307
2.87
0.035
0.049
0.076
(c)
Los Chonos Archipelago
Season
Sector
Season*, sector
Error
2
4
8
60
0.041
0.167
0.151
0.155
0.269
1.081
0.98
0.765
0.374
0.46
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Table 2
Full name, alphabetic code of the survey sectors and abundance (items km2) of principal floating marine debris (FMD) in the study area throughout the years and season. Empty
cell indicates that no surveys are available. Number of transects per sector where the respective FMD was present in parentheses; n = 5 transects per sector.
Code
Full name sector
FMD
2002
2003
Spring
Winter
2004
Winter
Spring
Winter
Spring
NFZ
Northern Fjordland Zone
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
19.4 (4)
2.1 (3)
2.1 (4)
0.1 (1)
0.4 (1)
0.4 (2)
3.4 (4)
12.2 (4)
4.5 (3)
3.4 (4)
0.4 (1)
8.6 (1)
1.1 (2)
3.3 (2)
24.3 (3)
3.0 (4)
5.2 (3)
0.9 (2)
0.3 (1)
0
2.0 (4)
6.3
5.3
3.4
1.0
0.2
0.3
2.3
GA
Golfo de Ancud
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
0.9
2.5
2.0
0.3
0
0.8
0.5
0.4
7.3
1.3
0
0.5
0
0.2
14.3 (2)
0
2.3 (2)
2.3 (2)
0.5 (1)
0
1.9 (1)
72.5 (5)
6.6 (4)
3.3 (3)
0.9 (2)
0
0
3.1 (4)
Spring
(2)
(1)
(1)
(1)
(2)
(1)
2005
(1)
(2)
(3)
(2)
(1)
(5)
(2)
(3)
(3)
(1)
(1)
(3)
ID
Islas Desertores
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
15.7 (2)
0
0.8 (1)
0
1.7 (1)
0
1.3 (1)
17.2 (2)
13.1 (3)
0.2 (1)
1.2 (3)
0.5 (1)
0
0.5 (1)
232.0 (5)
2.1 (2)
9.8 (4)
4.4 (3)
0.6 (1)
0.3 (1)
6.7 (4)
13.6 (2)
2.6 (3)
0.7 (2)
0.9 (1)
0.3 (1)
0
2.2 (2)
GC
Golfo del Corcovado
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
0.3
1.5
1.8
1.3
0
0.7
0.9
0.4 (2)
3.2 (2)
0.6 (1)
0.2 (1)
0.4(2)
0
0.2 (1)
3.7
2.9
2.9
3.3
1.2
0
0
26.3 (2)
1.4 (3)
4.0 (4)
1.0 (2)
0
0.4 (1)
1.3 (3)
1.9
0.8
3.3
0
0.5
0.5
0.5
0
0
1.4 (2)
1.4 (2)
0.5 (1)
0
0
BG
Boca del Guafo
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
0
0.4 (1)
0.4 (1)
0.8 (2)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MZ
Melinka Zone
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
0
0
0
0
0
0
0.9 (1)
0
0
0
0
0
0
0
0
0
0
0
0
0
0.9 (1)
KCZ
King channel Zone
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
0.2 (1)
0.2 (1)
0.1 (1)
0
0
0
0
0.4 (1)
0.8 (1)
4.8 (2)
0
0
0
0
0
0
0.3 (1)
0
0
0
0
DCZ
Darwin channel Zone
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
0
0
0.4 (1)
0
0
0
0
0
0.4 (1)
0.9 (2)
0
0
0
0
0.6
0.9
1.1
0.2
0
0
0
SFZ
Southern Fjordland Zone
Styrofoam
Plastic fragments
Plastic bags
Lines
Sacks
Wood boards
Others
0
0
10.1 (1)
0
0
0
0
0.4
0.9
4.5
0
0
0.4
0
0.3 (1)
0
0.9 (1)
0
0
0
0
than in the years 2002 and 2003 (Table 2). The principal category
of FMD in Los Chonos Archipelago was plastic bags, where they
reached similar abundances of 1–5 items km2 as in the Internal
(1)
(1)
(2)
(1)
(1)
(1)
(4)
(2)
(2)
(1)
(2)
(2)
(4)
(1)
(1)
(1)
(2)
(2)
(2)
(3)
(2)
0
0
1.5 (1)
0
2.7 (3)
0
0
(2)
(1)
(3)
(1)
Sea of Chiloé (Table 2). Styrofoam did not exceed 1 item km2
and food sacks were never found in the southern part of the study
area (Table 2).
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Fig. 3. Abundance and composition of items km2 of floating marine debris throughout the entire study area. Winter 2002 was not surveyed.
4. Discussion
4.1. Abundance and composition of floating marine debris (FMD)
FMD has been reported from all major oceans and coastal zones
throughout the world (Coe and Rogers, 1997; Gregory and Andrady, 2003). Generally, abundances of FMD (macrolitter) are highest
in coastal waters at mid and low latitudes (from 50°N to 40°S).
Extreme values of >2000 items km2 have been reported for
enclosed seas such as the Mediterranean Sea or sheltered bays in
Indonesia (Morris, 1980; Uneputty and Evans, 1997). Typical abundances for open coastal waters range from 0.01 to 25 items km2
(Thiel and Gutow, 2005). For example, for coastal waters of the
NE Pacific and around Japan FMD abundances of <5 items km2
have been reported (Matsumura and Nasu, 1997; Shiomoto and
Kameda, 2005, respectively). For the S Atlantic, Ryan (1988) found
abundances of 20 items km2 in coastal waters off S Africa. In a
previous study along the outer Chilean coast (20°S–40°S), we found
maximum abundances up to 40 items km2 in coastal waters close
to the principal port cities (Thiel et al., 2003). The values observed
in the present study ranged from 1 to 250 items km2 (see Fig. 2),
i.e. substantially higher than those reported for open coastal
waters and close to values reported for semi-enclosed bays in
highly populated regions. This is surprising since the population
density in our study area is relatively low (Fig. 1), compared to
other coastal zones in the world.
The composition of FMD in our study area was very particular
and similar to that reported for the East China Sea and Hiroshima
bay (Japan). In general, in our study FMD was dominated by styro-
foam (polystyrene), reaching 80% of the total during winter 2005.
In the East China Sea, using ship surveys Matsumura and Nasu
(1997) found 70% of FMD to be styrofoam. Fujieda and Sasaki
(2005) reported that styrofoam comprised 99% of stranded marine debris along the shores of Hiroshima bay. In contrast, most reports on floating or beached debris in other areas of the world
mentioned a predominance of other plastics (Derraik, 2002; Ivar
do Sul and Costa, 2007). In samples obtained with plankton nets
in the Kuroshio Current (NW Pacific), styrofoam made up 21% of
the total plastics (Yamashita and Tanimura, 2007). Using the same
methodology, Moore et al. (2001) found only 1% styrofoam in the
NE Pacific. Beach surveys reported similar proportions of styrofoam, which could be totally absent or reach up to 31% of the total
marine debris collected on local beaches (Panama – Garrity and
Levings, 1993; Mediterranean Sea – Martinez-Ribes et al., 2007).
In general, in most studies, styrofoam was less common than other
plastics. The congruence between our results and those from the
East China Sea and Hiroshima bay suggests similar sources.
4.2. Possible origins of FMD in coastal waters of southern Chile
Inferences about the sources of FMD can be obtained from different lines of evidence: (i) the proportional composition of different
types of FMD, (ii) particular types of FMD, or (iii) specific labels that
reveal the source of an item. Herein we distinguished seven types of
FMD, but we found a very particular composition of FMD, especially
in those sectors with high abundances, where styrofoam dominated. Matsumura and Nasu (1997) suggested land-based sources
to be responsible for the high proportions of floating styrofoam in
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the East China Sea. In contrast, sea-based sources had been suggested as potential sources of styrofoam on local shores in the Gulf
of Aqaba (Abu-Hilal and Al-Najjar, 2004). More specifically, Cho
(2005) suggested that the huge quantity of styrofoam on S Korean
beaches is generated by aquaculture activities in coastal waters.
The extraordinarily high abundances and proportions of styrofoam
on the coast of Hiroshima bay (Japan) were related to oyster farming (Fujieda and Sasaki, 2005). These authors also pointed out that
many oyster farms used styrofoam buoys in an inappropriate manner, namely without mesh cover. In southern Chile styrofoam buoys
are extensively used in mussel farming activities (Fig. 4), and the
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Internal Sea of Chiloé concentrates 99% of the total mussel productions of Chile (130,000 tons during 2006, SERNAPESCA, 2006). In
an unpublished study, Plaza et al. (2005) indicated that the principal zones in the Internal Sea of Chiloé producing 80% of the total
mussel harvest in 2003 were Castro (55%) and Calfuco (25%), i.e.
localities in sectors where floating styrofoam dominated in our
surveys (Isla Desertores and Golfo Ancud, respectively).
In addition to the proportional composition, we found one item
that clearly indicated its potential source, namely food sacks that
originally contained food pellets used in salmon aquaculture
(Fig. 5). These sacks were repeatedly found in the Internal Sea of
Fig. 4. Photographs of typical styrofoam floats utilised by mussel farming activities and their final fate on local beaches in the Internal Sea of Chiloé. (A) Mussel farm with
styrofoam floats. (B) Buoy with net protection. (C) Buoy without protection stranded on a local beach near Castro (sector Isla Desertores). (D) Typical beach in the vicinity of
Castro (sector Isla Desertores) with large amounts of small styrofoam particles (white ‘‘snow” in the foreground).
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Fig. 5. Photographs of floating marine debris impacts in the Internal Sea of Chiloé and Los Chonos Archipelago. (A) Plastic bottle of chlorine, (B) typical cobble beach close to
Castro on Chiloé Island, (C) sack of food pellets for salmon farming, (D) plastic bottle with attached marine invertebrates (sea urchins and sea anemone) and (E) entangled
Kelp gull (Larus dominicanus) with plastic bag.
Chiloé, where 80% of the salmon production from Chile is concentrated (500,000 tons during 2006; SERNAPESCA, 2006). Thus,
there is relatively strong evidence that most of the FMD found
in southern Chile have their origin in sea-based aquaculture
activities.
The other types of FMD found in the study area are difficult to
trace back to particular sources. Plastic bags and lines might come
from both land-based as well as sea-based activities. Possibly, the
relatively high abundances of plastic bags in the southern part of
the study area come from local fishermen, who work throughout
the entire area and often stay at sea for several days, bringing their
food provisions in typical plastic grocery bags. These kinds of plastic bags are also ubiquitous in coastal waters of the outer Chilean
coast (Thiel et al., 2003), and in other parts of Latin America (Ivar
do Sul and Costa, 2007).
4.3. Temporal variability and dynamics in the occurrence of FMD
No clear seasonal and annual differences in the abundances of
FMD are recognizable. However, there was a tendency of increasing
abundances during the last survey year in the Internal Sea of Chiloé
(Table 1, Fig. 2). This is paralleled by the tendencies in the sector
Boca del Guafo where abundances of FMD were <1 item km2 during the first two years but higher during the last two years. This increase in FMD could be related to the steady growth of aquaculture
activities in the region (e.g. Buschmann et al., 2006).
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I.A. Hinojosa, M. Thiel / Marine Pollution Bulletin 58 (2009) 341–350
The study area is characterized by estuarine circulation with
outward flow in the surface layers (Sievers and Silva, 2006).
According to this general flow pattern, one should expect FMD to
be transported out of the interior gulfs and channels and either
to exit the study area or to accumulate close to the estuarine front
or convergence zones as had been observed in other regions (Acha
et al., 2003; Pichel et al., 2007). However, in general we observed
highest abundances of FMD in the interior parts of the study area,
i.e. close to the putative sources. This suggests relatively short
floating times of FMD in the study area. A large proportion of the
FMD found in this study has a very high buoyancy (e.g. styrofoam),
and consequently is strongly exposed to the predominant winds in
the study area. Since the interior parts of the study area are semienclosed waters with many interspersed islands, it is very likely
that most FMD will quickly end up on local shores. This general
idea is also supported by large amounts of marine debris on the
shores in the sectors with high intensity of sea-based aquaculture
activities (Figs. 4 and 5).
4.4. Conclusions and recommendations
Here we found high abundances of FMD similar to those reported from densely populated coastal zones. The most common
item was styrofoam, which is intensively used as floatation device
in local mussel farms. Other marine debris (food sacks) was directly related to marine salmon farms. Thus, the distribution and
composition of FMD strongly suggests that sea-based aquaculture
activities are responsible for a large proportion of the FMD in the
study area. The impacts of FMD on the natural environment are
well known, as well as contamination of waters associated with
styrofoam spherules (Carpenter et al., 1972; Teuten et al., 2007).
Efforts to avoid or reduce the introductions of FMDs in the environment are needed. Recently (January of 2008) the Chilean government through the Supreme Decree (D.S. 86) modified the
actual legislation forcing aquaculture centers to use flotation systems that avoid release of styrofoam fragments and maintaining
the coastal border free of debris generated by aquaculture activities. In addition to stronger legislation, environmental education
and utilization of environmentally friendly technologies (biodegradable materials) needs to be improved. Moreover, standardized
surveys (as the ones used in this study) are necessary to identify
potential sources of FMD, but photographic documentation and
public participation (e.g. in beach surveys of FMD) will help raise
awareness and create support for measures that are aimed at
avoiding the problem at its source (Earll et al. 2000).
Acknowledgements
We thank the crews and colleagues who accompanied us during
the research cruises on board RV ‘‘AGOR Vidal Gormáz”. Photograph C and D of the Fig. 4 were contributed by Roberto Vasquez
Elos. Financial support through the research programs CIMAR Fiordo 8–11 of the Comité Oceanografico Nacional (CONA).
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