Spatial distribution of marine debris on the seafloor of Moroccan waters.

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Contents lists available at ScienceDirect

Marine Pollution Bulletin

journal homepage:www.elsevier.com/locate/marpolbul

Spatial distribution of marine debris on the sea ﬂ oor of Moroccan waters

S. Loulad

^a,*

, R. Houssa

^b

, H. Rhinane

^a

, A. Boumaaz

^b

, A. Benazzouz

^c

a Laboratory of Geosciences, Department of Geology, Faculty of Sciences, University Hassan II, Casablanca, Morocco

b National Institute ofﬁsheries Research, Casablanca, Morocco

c Higher Institute of Maritime Studies, Casablanca, Morocco

A R T I C L E I N F O

Keywords:

Marine debris Seaﬂoor GIS Pollution Plastic

A B S T R A C T

Marine debris pollution is considered as a worldwide problem and a direct threat to the environment, economy and human health. In this paper, we provide thefirst quantitative assessment of debris on the seafloor of the southern part of the economic exclusive waters of Morocco. The data were collected in a scientific trawl survey carried out from 5 to 25 October 2014 between (26N) to (21N) covering different stratums of depths (from 10 to 266 m) and following a sampling network of 100 stations distributed randomly in the study area. A total of 603 kg of debris was collected and sorted intofive main categories: plastic, metal, rubber, textiles and glass. Over 50% of collected items was made by plastic, 94% of them are the plasticfishing gear used to capture theOctopus vulgaris. The analysis of the distribution shows that anthropogenic debris is present in the majority of the prospected area (∼47,541 km²) with different densities ranging from 0 to 1768 ( ± 298,15) kg/km². The spatial autocorrelation approach using GIS shows that the concentration of this debris is correlated very well with a set of factors such as the proximity tofishing activity sites. Moreover, the mechanism of transportation and dispersion was influenced by the hydrodynamic properties of the region.

1. Introduction

Marine debris is considered as a pervasive worldwide pollution problem and a direct threat to wildlife, from smallest species of the marine trophic chain to human health and safety (UNEP, 2005, 2009, 2015; Sheavly and Register, 2007; Pham et al., 2014).

The United Nations Environment Program (UNEP) de

ﬁ

nes the marine debris as any persistent, manufactured or processed solid ma- terial discarded, disposed or abandoned into the marine and coastal environment. This includes

ﬁ

ve main categories; plastic, metal, textile, glass and rubber, where plastic materials represent the major con- stituents of this debris due to resistance of plastic to degradation (Corbin and Singh, 1993; Galgani and Andral, 1998; Ferentinos et al., 1999; Galgani et al., 2000; Derraik, 2002; UNEP, 2005; Barnes et al., 2009; Ryan et al., 2009; Browne et al., 2011; Cole et al., 2011).

The threat of anthropogenic debris to the marine environment has been neglected for a long time, until 1960, when the international lit- erature highlighted the problems, and discussed their impacts and im- plications (Ryan, 2015; Bergmann et al., 2015). Several surveys were launched to ensure complete coverage of oceans and seas. The UNEP (2009) evaluated globally the amount of debris entering the oceans every year at 6.4 million tons [5.8 million metric tons (MT)].

Depending on winds, currents and marine hydrodynamic (Barnes

et al., 2009), the debris composition and density changes greatly be- tween locations. From the pole to the equator, all the sites are aﬀected by this kind of pollution that has no borders (Thompson et al., 2009;

Browne et al., 2011; Bergmann et al., 2015). They can be

ﬂ

oating on the sea surface, on the seaﬂoor or on the shorelines (Barnes et al., 2009;

Ryan et al., 2009; Goldstein et al., 2013; Pham et al., 2014; Bergmann et al., 2015).

Most of the studies of marine debris were conducted on beaches using item counts along transects due to the easy accessibility of the data. The sea surface was surveyed using the ship-based observation technique to quantify and locate the

ﬂoating debris. However, the deep-

sea

ﬂoor is much less widely investigated, due to some sampling diﬃ-

culties, us inaccessibility, and the high cost of sampling in deeper wa- ters. Until now, The results of deep sea monitoring show that marine litter is widely spread in deep waters, their abundance know strong spatial variations between areas (Pham et al., 2014), and their mean densities were ranging from 0 to more than 100,000 items/km

²

(Galgani et al., 2000; Barnes et al., 2009; Keller et al., 2010; Miyake et al., 2011;

Ramirez-Llodra et al., 2013; Schlining et al., 2013; Pham and Gomes- Pereira, 2013; Fabri et al., 2014; Debrot et al., 2014; Fischer et al., 2015; Bergmann et al., 2015; Zhou et al., 2016).

The impacts of marine debris have been described extensively and the consequences are alarming and occur in various forms. The marine

http://dx.doi.org/10.1016/j.marpolbul.2017.07.022

Received 22 February 2017; Received in revised form 9 July 2017; Accepted 10 July 2017

*Corresponding author.

E-mail addresses:[email protected],[email protected](S. Loulad).

Marine Pollution Bulletin xxx (xxxx) xxx–xxx

Please cite this article as: loulad, s., Marine Pollution Bulletin (2017), http://dx.doi.org/10.1016/j.marpolbul.2017.07.022

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debris can cause serious ecological, aesthetic and human health damage (Corbin and Singh, 1993; MaLiTT, 2002; Islam and Tanaka, 2004;

Sheavly and Register, 2007; Gregory, 2009; GESAMP, 2010; Vegter et al., 2014; Di Beneditto and Awabdi, 2014; Gall and Thompson, 2015).

Even though this phenomenon is a worldwide problem, it has not been studied extensively in the Eastern Atlantic Ocean, and particularly in Moroccan waters. Knowing that Morocco has a coastline that stret- ches more than 3000 km with double maritime frontages; the Atlantic Ocean and the Mediterranean Sea, and

ﬁ

shing potential close to 1.5 million tons

“renewable every year”

(FAO, 2001). However, in the end, the marine environment is the main receptacle of pollutants. It receives directly 98% of liquid discharges from industrial and agricultural sec- tors and 52% of urban domestic wastes from coastal towns (Nakhli, 2010).

The present paper details the results of the

ﬁ

rst assessment of sea

ﬂoor marine debris in Southern Atlantic Ocean of Morocco using data

collected during a scientiﬁc trawling survey. Our objectives were to examine the abundance and composition of these marine debris, study their spatial distribution and concentration, deﬁne the relationship with the socio-economic activities and environmental characteristics, iden- tify the potential geographic origins of this debris, and

ﬁ

nally study the mechanism of transportation of marine debris in this area.

2. Materials and methods

2.1. Study area

Southern Atlantic Ocean of Morocco extends from Cap Boujdor 26N to Cap Blanc 21N. It is considered as a transition zone between northern subtropical Atlantic water (temperate) and tropical Atlantic southern water (Fig. 1).

Geomorphologically, the continental shelf is large and hetero- geneous; the underwater formations are more extended to the north than the south. In the forefront Level (24N), the extent of the con- tinental shelf is at the maximum and reaches about 100 nautical miles, while it is minimal (20 miles) at Cap Barbas in the south (22N), and at Cap Boujdor in the north (26N). A 94% of the total surfaces are adapted to the trawling activities (INRH, 1990).

The area climate is a

ﬀ

ected by the wind from the north and northeast, which is likely to generate when combined with a canary current. The winds run essentially parallel to the coast and limit terri- genous contributions to the oﬀshore. The intensities are relatively large with signi

ﬁ

cant occurrences conditions of strong winds, sometimes exceeding 12 m/s (INRH, 2013).

Hydrodynamically, the Moroccan Atlantic coast is directly under the in

ﬂ

uence of the anticyclone of the Azores and the zone of the inter- tropical convergence (ITCZ). The combination of the Canaries current and drift eﬀects the surface water by the trade winds that cause a coastal continuous deep cold water rich in nutrients (nitrates and phosphates) called upwelling (Barton, 1998; Pelegr et al., 2005;

Benazzouz et al., 2014b). It leads to the high productivity of the zone and aﬀects the abundance and availability of

ﬁshery resources (INRH,

2015).

The

ﬁsheries activities in the studied area are organized into three

segments of

fishing (deep-sea fishing, coastal fishing and artisanal fi

shing) (INRH, 2014). It reaches up 60% of all of the activity of the national

ﬁshing. A wide variety of species with a high demand in for-

eign markets exists in this area. The pelagic

ﬁshery is very important

with a strong dominance of sardines (Sardina pilchardus) and Cephalo- pods are the main exploited demersal species (FAO, 2001; INRH, 2002).

Several

ﬁshing techniques were then used to catch this species. The

trawl bottoms and the nets are the most used by deep sea and coastal segments of

ﬁshing, while the“jig”

and the

Octopus vulgaris

pots, were used by the artisanal segment in this Area (INRH, 2014).

2.2. Methods

2.2.1. Sampling methods

Relating to the marine monitoring program and the control of

ﬁsheries Resources, the National Institute of Fisheries Research of

Morocco (INRH) conducts every year a prospection scienti

ﬁ

c survey to cover the Moroccan exclusive economic zone EEZ. A scientiﬁc trawling survey by Charif AL IDRISSI vessel research sampled the continental shelf from 8 to 27 October 2014. It covered an area that extends be- tween cap Boujdor (26N) and Cap Blanc (21N) from 10 to 266 m depth (∼ 47,541 km

²

). The aim was to assess the stock of cephalopods in the region and speci

ﬁ

cally that of

Octopus vulgaris, and provide all in-

formation about every phenomenon a

ﬀ

ecting the Southern Moroccan marine ecosystem. In parallel, we collected marine debris, following the same sampling network of this prospecting survey. A number of 100 stations were chosen randomly in the total surface of prospected area, according to the search time available and the distance traveled by the vessel to explore all of the potential geographical coverage. The area surveyed was subdivided into four depth strata (Strate1: less than 50 m deep, Strate2: between 50 and 100 m, Strate3: between 100 and 150 m and Strate4: greater than 150 m), while the majority of prospected station was chosen between 0 to 100 m depth (Table 1).

The trawling

ﬁ

shing gear used was a Spanish trawl net with an opening diameter of 21 m and Morger Steel Panels weighs 450 kg, the trawling time was

ﬁ

xed in 30 min and the trawling speed was 3 knots on average.

At every station, multitude parameters have been identiﬁed: the geographical position, the time of trawling, the depth, the distance to the coast, the seabed nature (which varies between sandy and muddy), the total quantity and nature of each type of marine debris.

2.2.2. Classiﬁcation of debris

For each sampling event, a detailed analysis was carried out on the contents of the trawl to separate debris from marine species; knowing that some species use marine debris as arti

ﬁ

cial shelter. A wide di- versity of anthropogenic debris were found (gloves, fabric, plastic shoes and bottles, aluminum cans of soda, glass bottle, plastic chip bag, metal paint and

ﬁ

shing equipment). They were counted, sorted and weighed to define their total quantity. Then they were classified according to the methodology of separation defined by (Keller et al., 2010), where they are divided into

ﬁ

ve main categories: plastic, glass, metal, textiles (fabric or

ﬁber), and rubber.

2.2.3. Statistical analysis

According to Zhou et al. (2016) the density of debris lying on the seaﬂoor for the trawl net sampling method, was calculated using the equation:

=

D n

A

where density (D) is the amount of marine debris (kg/km

²

) per station.

n

is the number of debris collected per haul for a given category and

A

is area swept per (km

²

). Then swept area in each station by a

ﬁshing gear

during a unit of eﬀort is calculated by:

= A t s h x. . . ²

where

s

= the speed of trawling,

h

= length of the trawl rope,

t

= trawl time,

x²

= fraction expressing the width of the surface trawled divided by the length of the back rope (FAO, 1985).

Then the relative abundance of marine debris was calculated by:

=∑ Relative Abundance D

D. 100

2.2.4. Spatial analysis

In analyzing the data, we followed a process consisting of three

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steps. First, the graphic mapping using ArcGIS (ESRI, ArcGIS Desktop:

Release 10.2.1. Redlands, CA: Environmental Systems Research Institute) to visualize the spatial distribution of points and to study the di

ﬀ

erent relationships between all recorded parameters to under- standing their environmental signiﬁcance. Second, the kernel density tool was used to show the occurrence of the total quantity of debris and determine the hotspot zones.

Third, the calculation of the spatial autocorrelation index (Moran I) to the debris point pattern (x,y) and the data of debris weights was a necessary step to determine the state of distribution (Getis, 2008; Zhang and Lin, 2007; Waldhor, 1996) of debris, and to deduce the factors that manage there distribution. The analyzed data can be distributed ran- domly (negative autocorrelation) or clustered (positive autocorrelation) (Fig. 2).

To analyze the spatial distribution of sea-ﬂoor debris, we used two parameters: the distance to the coast and the depth of each trawling position. To explain the result, we used on a one hand, the zoning plan derived from the management plan elaborated by the Moroccan gov- ernment in 2004, to manage cephalopod

ﬁsheries; and on the other

hand we used wind and hydrodynamic parameters extracted from Marine Observation Satellites.

Remote Sensing Used Data. A various types of remote sensing data were

used to study the in

ﬂ

uence of hydrodynamic process in the distribution of marine debris;

Firstly, the ocean surface winds at 10 m of the sea surface are provided by NOAA/NESDIS (NOAA National Environmental Satellite, Data and Information Service) utilizing measurements from ASCAT aboard the EUMETSAT METOP satellite. Secondly, the satellite alti- metry is taken from the Archiving, Validation and Interpretation of Satellite Oceanographic Data (AVISO) (https://www.aviso.altimetry.fr/

en/data/products/sea-surface-height-products.html). Finally, a number altimetry indices were extracted:

□

The surface oceanic currents are derived from a monthly clima- tology of Sea Surface Height (SSH) AVISO merged products. Fig. 3 displays the mean seasonal state of the surface circulation pattern superimposed on the SSH.

□

The geostrophic

ﬂow considered as the balance between Coriolis

force, Eddy kinetic energy (EKE), and the pressure gradient force was derived as follows:

= − ∂

∂ = ∂

Ū g ∂ f

ADT y V g

f ADT

. . x .

= +

EKE 1 U V

2. ( ² ²).

where

Ū

and V are respectively the zonal and meridional geostrophic velocity components,

f

is the Coriolis parameter and

g

is the gravity acceleration.

Fig. 1. Location of the study area between cap Boujdor and cap Blanc with the sampling network used by the Charif Al Idrissi vessel in October 2014.

Table 1

The operations of trawling in diﬀerent depth strata from 0 to 266 m.

Depths strata (m) 0–50 50–100 100–150 150–266

Number of surveyed stations 41 54 4 1

Period of trawling (min) 1230 1620 120 30

S. Loulad et al. Marine Pollution Bulletin xxx (xxxx) xxx–xxx

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Fig. 2. The distribution models of the spatial autocorrelation index (Moran I).

Fig. 3. The seasonal climatology of the SSH superimposed on the geostrophic currents 2014. (a): Winter, (b): Spring, (c): Summer, and (d): Autumn.

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3. Results

3.1. Marine debris composition

The analysis of the database collected during the trawling survey in October 2014 showed the presence of marine debris in 61 stations among the 100 stations surveyed corresponding to 61% of the surveyed points. A 602,676 kg (293 pieces) of debris was collected across the prospected area (Fig. 4), their mean density per station was ranging from 0 to 1768 ( ± 298,15) kg/km

²

. They are distributed in diﬀerent strata depths from 10 to 266 m, and especially between 0 and 100 m depth because the number of stations chosen in these strata exceeds 95% of the total prospected stations (Table 2).

The classiﬁcation of these collected debris gave as a result,

ﬁve main

categories: plastic, metal, rubber, glass, and textile.

The comparison between these categories shows that the majority of seaﬂoor debris is made of plastic found in 54% of the trawling opera- tions, generally composed of plastic bags, bottles, boots, gloves, and pots used to catch octopus, distributed in all distances from 5 to 54 nautical miles away from the coastline, and in diﬀerent depths

exceeding 200 m. They account for 34.4% of the total debris weight, and 83.62% of the total number of debris items, and represent a density ranging from 0 to 1044 kg/km

²

(0 to 1045 item/km

²

).

Metallic material was found in 18% of the trawls content. It re- presents 29.16% in terms of weight and 7.51% in terms of the number of debris items, with a density varies between 0 to 1607 kg/km

²

(0 to 32 item/km

²

). This debris is generally composed of protecting trawl funds, some cans of soda and a small percentage of metallic pots. They are speci

ﬁ

cally concentrated between 10 to 43 nautical miles away from the line of the coast, in all the depth levels between 50 to 100 m.

Textile materials, composed of

ﬁ

bers derived from the remains of gear and fabrics, were found in 20% of trawling stations. In terms of weight, they exceeded 29,16% and represent 7,17% of items with a density varies between 0 to 1607 kg/km

²

(0 to 48 item/km

²

). Their highest concentration exists from 5 to 54 nautical miles away to the coastline, and between 50 to 100 m strata depth.

For rubber, the composition was found to be 4% of the trawling stations in the surveyed area. It represents more than 0.79% of the total weight and 1.37% of the collected items, with a density varies between 0 to 33 kg/km

²

(0 to 16 items/km

²

). This type of debris was generally concentrated between 11 and 33 nautical miles to the coastline, and between 50 to 100 m strata depth.

Finally, glass materials are rarely found and among the 100 trawling stations surveyed, they are represented in the form of a bottle. They are found in a single station located 32 nautical miles from the coast. The glass debris represents 0.12% of the total weight and 0.34% of the total eﬀective number.

3.2. Spatial distribution

The spatial projection of the total quantity of debris per station indicates that the majority of them are concentrated in the northern part of the study area between Cap Boujdor (26N) and Cap Falcon

Fig. 4. Examples of marine debris collected in the sampling area: (a)ﬁshing rod, (b) a large rope knotted, (c) trawl metal protects, (d) gloves, (e) trawl rubber protect, (f) fabric, (g) plastic shoes, (h) plastic bottles, (i) aluminum can of soda, (j) glass soda bottle, (k) pots ofOctopus vulgaris, (l) trawl bottom, (m) lostﬁshing rope, (n) plastic chip bag, (o) metal paint bucket, and (p) yoghurt pot.

Table 2

The mean density (kg/km²) of each category of debris collected in diﬀerent strata depths from 0 to 266 m.

Depths strata (m) > 50 50–100 100–150 < 266

Number of surveyed stations 41 54 4 1

Number of stations contained marine debris

26 33 1 1

Mean density of plastic debris (kg/km²) 71,99 6,19 8,03 16 Mean density of metal debris (kg/km²) 0,07 52,36 0 0 Mean tensity of textile debris (kg/km²) 39,76 33,58 0 0 Mean density of rubber debris (kg/km²) 0 1,39 0 0

Mean density of glass debris (kg/km²) 0 0,2 0 0

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(23N) (Fig. 5). Then, the analysis of the distribution of each type of them shows that the plastic debris is present throughout the whole study area. However, the other kinds of debris are mainly concentrated in the North of Dakhla bay, at the level of the stratum between 50 m and 100 m depth (Fig. 6).

The application of the index of spatial autocorrelation for all marine debris categories demonstrates that all distribution relationships are randomly dispersed in the space except for the plastic, which represent a well-structured distribution, in well-deﬁned areas and close to each other (Table 3).

Fig. 5. (a): The spatial distribution of the total quantity of marine debris in the study area. (b): The prediction map of distribution of debris using kernel density tool. The selected cell size was 0.01(1 km²) and the search radius was kept at 1 (100 km) due to the dispersion.

Fig. 6. The spatial distribution of diﬀerent categories of marine debris with the zone of concentration of each one of them.

Table 3

The application of the Moran index of spatial autocorrelation to all categories of collected debris in the surveyed area. Moran I parameters are based on the Euclidean Distance Method between points.

Inputﬁeld Moran value (z-score) Interpretation

Plastic debris 1,835038 Probability of less than 10% of this cluster model could be the result of random distribution.

Metal debris −0,154201 Model does not seem to be very diﬀerent than random.

Textile debris −0,46899 Model does not seem to be very diﬀerent than random.

Rubber debris −0,2345 Model does not seem to be very diﬀerent than random.

Glass debris −0,55677 Model does not seem to be very diﬀerent than random.

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The plastic materials collected are composed of 94% of the octopus pots and 4% (bottles, bags,

ﬂoats, gloves, and boots). The mean dis-

tribution was logically in

ﬂ

uenced by the lost

ﬁ

shing gear used to catch octopus by artisanal

ﬁshing boats that carry their activities between 3

and 8 nautical miles according to the development plan in this zone (Fig. 7).

4. Discussion

The distribution of sea

ﬂ

oor debris has been studied using various methods, including diving (Donohue et al., 2001), submersibles, re- motely operated vehicles (Galgani et al., 2000), and by trawling (Galil et al., 1995; Galgani et al., 2000). The recorded mean densities of collecting debris in di

ﬀ

erent sampling areas in the world were ranged

Fig. 7. : The spatial distribution of diﬀerent kinds of plastic debris in the Southern Atlantic Ocean of Morocco between Cap Boujdor and Cap Blanc.

Fig. 8. The analysis of relative abundance of marine debris in relation to the depth and the distance to the coastline.

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from 0 to 100,000 items/km

²

, where The Mediterranean Sea in parti- cular shows the highest densities of debris on the sea

ﬂ

oor. The majority of collected items was formed by plastic typically comprise

≥

70% of seabed of all seas and oceans (Galil et al., 1995; Galgani et al., 2000;

Barnes et al., 2009). The marine debris were mainly coming from six major origins; coastal tourism, industrial discharges, port activities, public discharges,

ﬁ

shing activities, and maritime tra

ﬃ

c (IFREMER, 2010). As a result, all the international literature classiﬁes the marine debris into two main sources: terrestrial and marine sources, depending on the place where they enter the water. An average of 70% to 80% of marine debris found in the sea and on the coast are from land based activities (OSPAR, 2009) and the rest comes from maritime activities as the maritime tra

ﬃ

c of the vessels and the

ﬁ

shing activities. The present study was conducted in an area known by a higher

ﬁ

shing activity (trawling area). The density of marine debris was considered as a low- to medium-density comparing to another area in the world, it varies between 0 to 4400 item /km

²

, while 83% of these collected items were formed by plastic. The Debris was scattered in the majority of the study area, and most highly concentrated in the north part between 26N to 23N from 0 to 100 m depth and in di

ﬀ

erent distance to the coast (Fig. 8). The analysis of the marine debris nature and their spatial distribution compared to the socio-economical aspect of the study area led to well determination all the origins of debris in the southern Atlantic of Morocco.

Fig. 9. The structure of a row of pots used for the octopusﬁshery in the southern Atlantic of Morocco.

Fig. 10. The spatial distribution of octopus pots superimposed on the three sub management units deﬁned by the management plan of cephalopods.

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4.1. Sources of marine debris

The southern Atlantic of Morocco has been a

ﬀ

ected by a perceptible socio-economic increase in several sectors. It has become a real me- tropolis with an urbanization of 84.7% (The census General population and housing, 2004), but the rate of coastal urbanization is still quietly low (0.7 inhabitants per km) compared to the national density (42 in- habitants per km) (Monography, 2013). The water resources are very scarce, the hydrographic network is relatively small, and the average annual rainfall in the last 18 years does not exceed 67.5 mm. In addi- tion, the area is characterized by the inexistence of terrigenous addi- tions from the rivers (a desert region) (INRH, 1990). The tourism ac- tivity remains relatively low and limited; it usually focuses in the lagoon of Dakhla. The industrial sector is less developed, and generally recognized by

ﬁshing sector, which consists of national vessels and

foreign vessels (European Union and Russia) operating under

ﬁ

sheries agreements, then the national vessels are composed of three segments:

deep-sea

fishing, coastalfishing and artisanalfishing(INRH, 2014). The

analysis of the socio-economic characteristics of the study area and the nature of marine debris found in its maritime zone allows us to con- clude that almost all of this marine debris originates from the

ﬁshing

activity in this zone.

Indeed: octopus pots that represent more than 75% of all debris items come from artisanal

ﬁshing activity, while the rest (other plastic,

glass, gear nets, etc.) can come from coastal and oﬀshore

ﬁshing vessels

that stay at sea between 1 day and few months. The pots are the most

ﬁshing gear used by (artisanal/working) ﬁshermen to catch octopus.

Composed of 1 kg of plastic with 2 kg of cement to

ﬁx it in the depth Fig. 11. The spatial distribution of octopus pots superimposed on the circulation pattern in the study area between Cap Boujdor and Cap Blanc.

Fig. 12. The mean annual (2014) wind rose of the southern Atlantic area.

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(Fig. 9), this instrument is considered as a selective

ﬁshing gear, easy to

use with a low-cost of manufacturing.

The cephalopods

ﬁ

shery in the southern area was managed by a management plan MP based on limiting the total allowable catch using several factors to delimit the exploitation of this resource. It relies on two management measures. Firstly, the limitation of number of pots using by artisanal

ﬁshing 300 pots per boat. In addition, dividing the

area into 3 sub management units, and authorized the artisanal

ﬁshery

to

ﬁ

sh in the second sub-unit in the coastal band between 3 to 8 miles (INRH, 2013). Spatially, the lost pots (detached from their line) are now very common on the entire continental shelf; in the coastal area where they were originally installed between 3 to 8 miles and even away from this area (Fig. 10). The existence of those derelict pots is generally be due to a range of factors, such as vandalism, and bad weather which causes the pot lines to be cut. They then move due to the ocean cur- rents.

4.2. Transportation mechanism

From 30 stations where we collect octopus pots in the survey area, 13 of them are distributed in the licensed area deﬁned by the MP of Cephalopods (131 kg of plastic). However, outside the licensed area 17 hauls contained plastic pots, some of them in sub-unit 2 but beyond 8 miles, exceeding the boundary of the authorized zone, and the re- maining is distributed to the south of the sub-unit 3 to the Mauritanian border where there is no

ﬁ

shing activity, which means that the pots are moved in both directions south and west.

AVISO SSHs indicate that with the onset of the upwelling process, a drop in height is observed along the Moroccan southern coast asso- ciated with the presence of the cool upwelled waters also with cyclonic eddies. This drop in height sets up a horizontal pressure gradient and results in a compensating along-shore

ﬂ

owing geostrophic current. The geostrophic adjustment associated with this oﬀshore pressure gradient establishes the southward and eastward (oﬀshore)

ﬂowing coastal

current during the upwelling activity. As it's shown in the

ﬁ

gures (Fig. 3), the geostrophic currents along the Moroccan southern Atlantic coast are mostly persistent around year explaining one part of the connection between the coastal area and the open ocean water. The energetic mesoscale structures as seen from altimetry satellite ob- servations and as computed with the EKE can provide insight into dominant transport pathways controlling the horizontal exchange from the coastal area to the ocean interior penetrating up 300

’

s of kilometers oﬀshore and transporting important lost pots far into the ocean interior (Fig. 11). Another interesting hydrodynamic aspect is the upwelling jet, which consists of a geostrophically

ﬂ

ow advection process that connect the northern part of the studied area (24N) to the southern part (21N) leading to the interaction of the cyclonic and anticyclonic eddies (Benazzouz et al., 2014a) transporting southward the lost pots. This process operates to lower the sea level by about 5–10 cm until a dy- namical equilibrium is reached. This drop in sea level is suﬃcient to create a shoreward pressure gradient force driving a swift geostrophic upwelling jet.

Finally, the interpretation of the wind displacement

ﬁelds between

21N and 26N also shows that, the direction was mainly from the Northeast area to the south west of a region which facilitates the movement of plastic pots due to their low weight from the authorized area for artisanal

ﬁshing toward the southwestern end of the EEZ and

even outside (Fig. 12).

The modeling of marine debris displacement and their future ac- cumulation area requires a multi-temporal analysis of the zone.

5. Conclusions

The distribution of sea

ﬂ

oor debris at the southern Moroccan Atlantic area is generally a phenomenon that has never been studied due to the exploration costs of maritime area. The use of the same

sampling network of trawling prospecting surveys gives us an oppor- tunity to collect more information on the state of the marine environ- ment. The result shows that the Moroccan southern Atlantic Ocean like any other part of the ocean was aﬀected by the pollution caused by marine debris. This phenomenon is typically related to the

ﬁshing ac-

tivity conducted by three segments of

ﬁ

sheries that operated in the area. Most debris founded were plastics materials and especially the

ﬁshing gear used to capture theOctopus vulgaris, then the debris have

been transported to other areas outside the

ﬁ

shing zone due to the hydrodynamic e

ﬀ

ects.

A future study will be dedicated to the impact of accumulation of debris materials on the marine environment.

Acknowledgments

We are grateful to all people who provided many constructive comments that helped to improve this manuscript. Special thanks to all the staﬀ of the National Fisheries Research Institute in Casablanca, and we also wish to thank Mr. Hamzaoui for his help in proofreading this paper.

References

Barnes, D.K.A.D.K.A., Galgani, F.F., Thompson, R.C.R.C., Barlaz, M.M., 2009.

Accumulation and fragmentation of plastic debris in global environments. Philos.

Trans. Biol. Sci. 364.http://dx.doi.org/10.1098/rstb.2008.0205.

Barton, E.E., 1998. Eastern boundary of the north atlantic: Northwest Africa and Iberia.

Coastal segment (18, e). In: Robinson, A.R.A.R., Brink, K.H.K.H. (Eds.), The Sea: The Global Coastal Ocean. vol. 11. Wiley, pp. 633–657.

Benazzouz, A.A., Pelegr, J.J., Demarcq, H.H., Machn, F.F., Mason, E.E., Orbi, A.A., Pea- Izquierdo, J.J., Mordane, S.S., 2014a. On the temporal memory of coastal upwelling oﬀNW Africa. J. Geophys. Res. 119.http://dx.doi.org/10.1002/2013JC009559.

Benazzouz, S.S., Mordane, Assa a, Orbi, A.A., Chagdali, M.M., Hilmi, K.K., Atillah, A.A., Llus Pelegr, J.J., Herv, D.D., 2014, 06. An improved coastal upwelling index from sea surface temperature using satellite-based approach the case of the canary current upwelling system. Cont. Shelf Res. 81.http://dx.doi.org/10.1016/j.csr.2014.03.012.

Bergmann, M.M., Gutow, L.L., Klages, M.M., 2015. Marine Anthropogenic Litter—Global Distribution, Composition and Abundance of Marine Litter. vol. 10.1007/978-3-319- 16510-3http://dx.doi.org/10.1007/978-3-319-16510-3_2.

Browne, M.A.M.A., Crump, P.P., Niven, S.J.S.J., Teuten, E.E., Tonkin, A.A., Galloway, T.T., Thompson, R.R., 2011. Accumulation of microplastic on shorelines worldwide:

sources and sinks. Environ. Sci. Tech. 45.http://dx.doi.org/10.1021/es201811s.

Cole, M.M., Lindeque, P.P., Halsband, C.C., Galloway, T.T., 2011. Microplastics as con- taminants in the marine environment: a review. Mar. Pollut. Bull. 62.http://dx.doi.

org/10.1016/j.marpolbul.2011.09.025.

Corbin, C.C., Singh, J.J., 1993. Marine debris contamination of beaches in St. Lucia and Dominica. Mar. Pollut. Bull. 26.http://dx.doi.org/10.1016/0025-326x(93)90575-5.

Debrot, A.A., Vinke, E.E., van der Wende, G.G., Hylkema, A.A., Reed, J.J., 2014.

Deepwater marine litter densities and composition from submersible video-transects around the ABC-islands, Dutch Caribbean. Mar. Pollut. Bull. 88.http://dx.doi.org/

10.1016/j.marpolbul.2014.08.016.

Derraik, J.G.J.G., 2002. The pollution of the marine environment by plastic debris: a review. Mar. Pollut. Bull. 44.http://dx.doi.org/10.1016/s0025-326x(02)00220-5.

Di Beneditto, A.P.M.A.P.M., Awabdi, D.R.D.R., 2014. How marine debris ingestion diﬀers among megafauna species in a tropical coastal area. Mar. Pollut. Bull. 88.http://dx.

doi.org/10.1016/j.marpolbul.2014.09.020.

Donohue, M.M., Boland, R.C.R.C., Sramek, C.M.C.M., Antonelis, G.A.G.A., 2001. Derelict ﬁshing gear in the northwestern Hawaiian islands: diving surveys and debris removal in 1999 conﬁrm threat to coral reef ecosystems. Mar. Pollut. Bull. 42.http://dx.doi.

org/10.1016/s0025-326x(01)00139-4.

Fabri, M.-C.M.-C., Pedel, L.L., Beuck, L.L., Galgani, F.F., Hebbeln, D.D., Freiwald, A.A., 2014. Megafauna of vulnerable marine ecosystems in French mediterranean sub- marine canyons: spatial distribution and anthropogenic impacts. Deep-Sea Res. II Top. Stud. Oceanogr. 104.http://dx.doi.org/10.1016/j.dsr2.2013.06.016.

FAO, 1985. Some Simple Methods for Estimating Tropical Fish Stocks. Technical Report FAO.

FAO, 2001. Report and Documentation of the Refugee Workshop on Fisheries Capacity Management in West Africa. Technical Report FAO.

Ferentinos, G.S.A.G.S.A., Charalampakis, M.M., G. P., 1999. Marine debris on the seaﬂoor of the Mediterranean sea: examples from two enclosed gulfs in Western Greece. Mar.

Pollut. Bull. 38.http://dx.doi.org/10.1016/s0025-326x(98)00141-6.

Fischer, V.V., Elsner, N.O.N.O., Brenke, N.N., Schwabe, E.E., Brandt, A.A., 2015, 01.

Plastic pollution of the Kurilkamchatka trench area (NW Paciﬁc). Deep-Sea Res. II Top. Stud. Oceanogr. 111.http://dx.doi.org/10.1016/j.dsr2.2014.08.012.

Galgani, F.F., Andral, B.B., 1998. [IEEE IEEE oceanic engineering society. oceans'98.

Conference proceedings - nice, France (28 sept.-1 oct. 1998)] IEEE oceanic engineering society. oceans'98. Conference proceedings (cat. no.98CH36259) - methods for evaluating debris on the deep seaﬂoor. In: 3http://dx.doi.org/10.1109/oceans.

1998.726324.

(11)

Galgani, F.F., Leaute, J.J., Moguedet, P.P., Souplet, A.A., Verin, Y.Y., Carpentier, A.A., Goraguer, H.H., Latrouite, D.D., Andral, B.B., Cadiou, Y.Y., Mahe, J.J., Poulard, J.J., Nerisson, P.P., 2000. Litter on the seaﬂoor along European coasts. Mar. Pollut. Bull.

40.http://dx.doi.org/10.1016/s0025-326x(99)00234-9.

Galil, B.B., Golik, A.A., Trkay, M.M., 1995. Litter at the bottom of the sea: a sea bed survey in the eastern Mediterranean. Mar. Pollut. Bull. 30.http://dx.doi.org/10.

1016/0025-326x(94)00103-g.

Gall, S.C.S.C., Thompson, R.R., 2015. The impact of debris on marine life. Mar. Pollut.

Bull. 92.http://dx.doi.org/10.1016/j.marpolbul.2014.12.041.

GESAMP, 2010. Proceedings of the GESAMP International Workshop on Plastic Particles as a Vector in Transporting Persistent. Bio-accumulating and Toxic Substances in the Oceans. In GESAMP Reports and Studies.Proceedings of the GESAMP International Workshop on Plastic Particles as a Vector in Transporting Persistent. Bio-accumulating and Toxic Substances in the Oceans. In GESAMP Reports and Studies.

Getis, A.A., 2008. A history of the concept of spatial autocorrelation: a geographer's perspective. Geogr. Anal. 40.http://dx.doi.org/10.1111/j.1538-4632.2008.00727.x.

Goldstein, M.C.M.C., Titmus, A.J.A.J., Ford, M.M., 2013. Scales of spatial heterogeneity of plastic marine debris in the northeast Paciﬁc Ocean. PLOS ONE 8 (11), 1–11.http://

dx.doi.org/10.1371/journal.pone.0080020.

Gregory, M.R.M.R., 2009, 07. Environmental implications of plastic debris in marine settings-entanglement, ingestion, smothering, hangers-on, hitch-hiking and alien in- vasions. Philos. Trans.: Biol. Sci. 364.http://dx.doi.org/10.1098/rstb.2008.0265.

IFREMER, 2010. Direction foresight and scientiﬁc strategy Maryvonne HENRY - RST.DOP/LER-PAC/10-09. Technical Report IFREMER.

INRH, 1990. Documents and works. Technical Report INRH.

INRH, 2002. Fishery resources. Technical Report INRH.

INRH, 2013. State of stock. Technical Report INRH.

INRH, 2014. Oceanographic synthese. Technical Report INRH.

INRH, 2015. Fishing newsletter. Technical Report INRH.

Islam, M.S.M.S., Tanaka, M.M., 2004. Impacts of pollution on coastal and marine ecosystems including coastal and marineﬁsheries and approach for management: a review and synthesis. Mar. Pollut. Bull. 48.http://dx.doi.org/10.1016/j.marpolbul.

2003.12.004.

Keller, A.A.A.A., Fruh, E.L.E.L., Johnson, M.M.M.M., Simon, V.V., McGourty, C.C., 2010.

Distribution and abundance of anthropogenic marine debris along the shelf and slope of the US west coast. Mar. Pollut. Bull. 60.http://dx.doi.org/10.1016/j.marpolbul.

2009.12.006.

MaLiTT, 2002. The impacts of marine litter, marine pollution monitoring management group. Technical Report MaLiTT.

Miyake, H., Shibata, H., Furushima, Y., 2011. Deep-sea litter study using deep-sea observation tools. In: Omori, K., Guo, X., Yoshie, N., Fujii, N., Handoh, I.C., Isobe, A., Tanabe, S. (Eds.), Interdisciplinary studies on environmental Chemistry. J. Mar.

Environ. Analpp. 261–269.

Monography, 2013. Monography of the Region Laayoune Boujdour Sakia El Hamra.

Technical Report.

Nakhli, S.S., 2010. Environmental pressures and new management strategies on the Moroccan coast. Ph.D. thesis Center for Studies and Research in Urban Development and Planning.

OSPAR, 2009. Marine litter, preventing a sea plastic. Technical Report OSPAR Booklets. . http://www.ospar.org/html_documents/ospar/html/marine_litter_unep_ospar.pdf.

Pelegr, J.J., Arstegui, J.J., Cana, L.L., Gonzlez-Dvila, M.M., Hernndez-Guerra, A.A.,

Hernndez-Len, S.S., Marrero-Daz, A.A., Montero, M.M., Sangr, P.P., Santana-Casiano, M.M., 2005. Coupling between the open ocean and the coastal upwelling region oﬀ northwest Africa: water recirculation and oﬀshore pumping of organic matter. J. Mar.

Syst. 54.http://dx.doi.org/10.1016/j.jmarsys.2004.07.003.

Pham, C.C., Ramirez-llodra, E.E., Alt, C.C., Amaro, T.T., Bergmann, M.M., Canals, M.M., Tyler, P.P., 2014. Marine litter distribution and density in European seas from the shelves to deep basins. PLoS ONE 9(4).http://dx.doi.org/10.1371/journal.pone.

0095839.

Pham, J.I.E.S.R.M.T.J.I.E.S.R.M.T., Gomes-Pereira, C.K.C.K., 2013. Abundance of litter on condor seamount (Azores, Portugal, northeast Atlantic). Deep-Sea Res. II Top. Stud.

Oceanogr. 98.http://dx.doi.org/10.1016/j.dsr2.2013.01.011.

Ramirez-Llodra, E.E., De Mol, B.B., Company, J.B.J.B., Coll, M.M., Sard, F.F., 2013.

Eﬀects of natural and anthropogenic processes in the distribution of marine litter in the deep Mediterranean Sea. Prog. Oceanogr. 118.http://dx.doi.org/10.1016/j.

pocean.2013.07.027.

Ryan, P.P., 2015. Marine Anthropogenic Litter, A Brief History of Marine Litter Research.

vol. 10.1007/978-3-319-16510-3http://dx.doi.org/10.1007/978-3-319-16510-3_1.

Ryan, P.G.P.G., Moore, C.J.C.J., van Franeker, J.A.J.A., Moloney, C.L.C.L., 2009.

Monitoring the abundance of plastic debris in the marine environment. Philos. Trans.:

Biol. Sci. 364.http://dx.doi.org/10.1098/rstb.2008.0207.

Schlining, K.K., von Thun, S.S., Kuhnz, L.L., Schlining, B.B., Lundsten, L.L., Jacobsen Stout, N.N., Chaney, L.L., Connor, J.J., 2013. Debris in the deep: using a 22-year video annotation database to survey marine litter in Monterey Canyon, Central California, USA. Deep-Sea Res. I Oceanogr. Res. Pap. 79.http://dx.doi.org/10.1016/

j.dsr.2013.05.006.

Sheavly, S.S., Register, K.K., 2007. Marine debris and plastics, environmental concerns, sources, impacts and solutions. J. Polym. Environ. 15.http://dx.doi.org/10.1007/

s10924-007-0074-3.

Thompson, R.C.R.C., Moore, C.J.C.J., vom Saal, F.S.F.S., Swan, S.H.S.H., 2009. Plastics, the environment and human health: current consensus and future trends. Philos.

Trans. Biol. Sci. 364.http://dx.doi.org/10.1098/rstb.2009.0053.

UNEP, 2005. Marine litter: an analytical overview. Technical Report. Intergovernmental Oceanographic Commission of the United Nations Educational, Scientiﬁc and Cultural Organisation.

UNEP, 2009. Marine litter: a global challenge. Technical Report. United Nations Environment Program.

UNEP, 2015. Evaluation des dchets marins en mditerrane. Technical Report. United Nations Environment Program.

Vegter, A.C.A.C., Barletta, M.M., Beck, C.C., Borrero, J.J., Burton, H.H., Hamann, M.L.C.M.M.L.C.M., 2014. Global research priorities to mitigate plastic pollution impacts on marine wildlife. Endang Species Res. 25.http://dx.doi.org/10.3354/

esr00623.

Waldhor, T.T., 1996. The spatial autocorrelation coeﬃcient Moran's i under hetero- scedasticity. Stat. Med. 15.http://dx.doi.org/10.1002/(sici)1097-0258(19960415) 15:7/9<887::aid-sim257>3.0.co;2-e.

Zhang, T.T., Lin, G.G., 2007. A decomposition of Moran's i for clustering detection.

Comput. Stat. Data Anal. 51.http://dx.doi.org/10.1016/j.csda.2006.12.032.

Zhou, C.C., Liu, X.X., Wang, Z.Z., Yang, T.T., Shi, L.L., Wang, L.L., You, S.S., Li, M.M., Zhang, C.C., 2016. Assessment of marine debris in beaches or seawaters around the China seas and coastal provinces. Waste Manag. 48.http://dx.doi.org/10.1016/j.

wasman.2015.11.010.