# Review of alien marine macrophytes in Tunisia.

Y.R. Sghaier, R. Zakhama-Sraieb, S. Mouelhi, M. Vazquez, C. Valle, A.A. Ramos-Espla, J.M. Astier, Marc Verlaque

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## To cite this version:

Y.R. Sghaier, R. Zakhama-Sraieb, S. Mouelhi, M. Vazquez, C. Valle, et al., Review of alien marine macrophytes in Tunisia., Mediterranean Marine Science, 2015, 17 (1), pp.109-123. hal-01436537

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Mediterranean Marine Science

Vol. 17, 2016

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Review of alien marine macrophytes in Tunisia

SGHAIER Y. Regional Activity Centre for Specially Protected Areas (RAC/SPA)

ZAKHAMA-SRAIEB R. Université de Tunis El Manar, Faculté des Sciences de Tunis, UR 11ES11 Bio-Ecologie et Systématique Evolutive, 2092 Tunis

MOUELHI S. Université de Tunis El Manar, Faculté des Sciences de Tunis, UR 11ES11 Bio-Ecologie et Systématique Evolutive, 2092 Tunis

VAZQUEZ M. Instituto Español de Oceanografía, Centro Oceanográfico de Baleares, Muelle de Poniente s/n, 07015 Palma de Mallorca

VALLE C. Universidad de Alicante, Departamento de Ciencias del Mar y Biología Aplicada, 03080 Alicante

RAMOS-ESPLA A.A. Universidad de Alicante, Departamento de Ciencias del Mar y Biología Aplicada, 03080 Alicante

ASTIER J.M. 79 Bvd St Hélène, Le Mourillon, Toulon

VERLAQUE M. Aix-Marseille University and Toulon University, Mediterranean Institute of Oceanography (MIO), CNRS, IRD, UM 110, F-13288 Marseille Cedex 09

CHARFI-CHEIKHROUHA F. Université de Tunis El Manar, Faculté des Sciences de Tunis, UR 11ES11 Bio-Ecologie et Systématique Evolutive, 2092 Tunis

https://doi.org/10.12681/mms.1366
To cite this article:

SGHAIER, Y., ZAKHAMA-SRAIEB, R., MOUELHI, S., VAZQUEZ, M., VALLE, C., RAMOS-ESPLA, A.A., ASTIER, J.M., VERLAQUE, M., & CHARFI-CHEIKHROUHA, F. (2015). Review of alien marine macrophytes in Tunisia. *Mediterranean Marine Science*, 17(1), 109-123. doi:https://doi.org/10.12681/mms.1366
# Review of alien marine macrophytes in Tunisia

Y. R. SGHAIER<fnref n="1" />,<fnref n="2" />, R. ZAKHAMA-SRAIEB<fnref n="2" />, S. MOUELHI<fnref n="2" />, M. VAZQUEZ<fnref n="3" />, C. VALLE<fnref n="4" />, A.A. RAMOS-ESPLA<fnref n="4" />, J.M. ASTIER<fnref n="5" />, M., VERLAQUE<fnref n="6" /> and F. CHARFI-CHEIKHROUHA<fnref n="2" />

Corresponding author: yassineramzi.sghaier@rac-spa.org

Handling Editor: Konstantinos Tsiamis

Received: 3 July 2015; Accepted: 27 July 2015; Published on line: 21 January 2016

## Abstract

In the present study, the list of alien marine macrophytes introduced into Tunisia was updated in light of available data and new observations. A total of 27 alien marine macrophytes has been recorded so far from Tunisia: 18 Rhodophyta, 3 Ochrophyta, 5 Chlorophyta and 1 Magnoliophyta. For each species, the locality (-ies), the year (or) period and the source of the first observation in Tunisia are given. The distribution and the status (casual, cryptogenic, established or questionable) of species in Tunisia were evaluated and, where appropriate, discussed. Among them, *Hypnea cornuta* is reported for the first time from Tunisia. Fourteen alien marine macrophytes are established, whereas seven cryptogenic and two casual species require further investigation. Eleven species are considered as invasive or potentially invasive in the Mediterranean Sea: *Acrothamnion preissii*, *Asparagopsis armata*, *A. taxiformis* Indo-Pacific lineage, *Hypnea cornuta*, *Lophocladia lallemandii*, *Womersleyella setacea*, *Caulerpa chemnitzia*, *C. cylindracea*, *C. taxifolia*, *Codium fragile* subsp. *fragile* and *Halophila stipulacea*. Finally, the case of four questionable species is also discussed.

**Keywords:** Alien, invasive species, marine macrophytes, *Hypnea cornuta*, Tunisia, Mediterranean.

## Introduction

Biological invasions are now recognized as a major agent of global change, following the spectacular increase in invasions by alien marine and estuarine species in various regions of the world (Occhipinti-Ambrogio, 2007). The Mediterranean Sea is one of the regions worldwide which is most severely affected by alien marine invasions, fostered by the opening of the Suez Canal, fouling and ballast transportation along shipping lines, aquaculture, the aquarium trade and global climate change (Zenetos et al., 2010, 2012). The number of alien marine species reported so far from the Mediterranean Sea has almost reached 1,000 (approximately 6% of the total flora and fauna; Hoffman, 2014). The vast majority of alien species (775) occur in the eastern Mediterranean basin, whereas a lower number of species are known for the western Mediterranean (308) and the central Mediterranean (249) and, to an even lesser degree, for the Adriatic Sea (190) (Zenetos et al., 2010, 2012). The origin of these species is mainly the Red Sea, followed by the Indo-Pacific and the Atlantic oceans (Zenetos et al., 2012).

As far as marine macrophytes are concerned, a total of 133 species have been listed as possible aliens; of these 23 belong to the Chlorophyta, 79 to the Rhodophyta, 30 to the Ochrophyta, and one is a seagrass species (Magnoliophyta) (Verlaque et al., 2015).

With more than 1,400 km of coastline, and located at the crossroads between the different Mediterranean basins, Tunisia occupies a key position in the context of the Mediterranean Sea. The Tuniso-Sicilian strait is the passageway from south to north and from east to west, and is crucial in the analysis of the spread of alien species introduced into the Mediterranean Sea.

During the last decade, the monitoring of marine aliens in the Mediterranean Sea has attracted strong interest from the scientific community, international organizations, and has been the focus of environmental programs (Marine Strategy Framework Directive, the European Strategy for Marine and Maritime Research, the Marine Spatial Planning and the Ecosystem Approach within the Barcelona Convention by UNEP/MAP, as well as many initiatives of the UNEP RAC/SPA). However, records of alien marine species from Tunisia are sparse and scat-

<footnote n="1">¹ Regional Activity Centre for Specially Protected Areas (RAC/SPA), Boulevard du Leader Yasser Arafat, BP 337, 1080 Tunis cedex, Tunisia</footnote>

<footnote n="2">² Université de Tunis El Manar, Faculté des Sciences de Tunis, UR 11ES11 Bio-Ecologie et Systématique Evolutive, 2092 Tunis, Tunisia</footnote>

<footnote n="3">³ Instituto Español de Oceanografía, Centro Oceanográfico de Baleares, Muelle de Poniente s/n, 07015 Palma de Mallorca, Spain</footnote>

<footnote n="4">⁴ Universidad de Alicante, Departamento de Ciencias del Mar y Biología Aplicada, 03080 Alicante, Spain</footnote>

<footnote n="5">⁵ 79 Blvd St Hélène, Le Mourillon, Toulon, France</footnote>

<footnote n="6">⁶ Aix-Marseille University and Toulon University, Mediterranean Institute of Oceanography (MIO), CNRS, IRD, UM 110, F-13288 Marseille Cedex 09, France</footnote>
tered. Because of the large stretch of coastline and lack
of research programs focusing on the subject, there are
many gaps in the knowledge of alien marine species.

The aim of this paper is to provide a robust baseline
for the monitoring of alien marine macrophytes (hereaf-
ter AMM) of Tunisia through a critical compilation of all
the available historical data. In parallel, several dedicated
field surveys were conducted along the coast to search for
AMM and to establish their current distributions. Results
will be presented online on the Marine Mediterranean In-
vasive Alien Species (MAMIAS) database (UNEP-MAP
RAC/SPA, 2015), and questionable records are discussed.

**Materials and Methods**

Compilation of the available historical data

The list of AMM reported from Tunisia was critically
established on the basis of a compilation of existing infor-
mation/observations (scientific and grey literature, news-
papers, online databases, internet forums and unpub-
lished data from regional experts). Native range, locality
(-ies) and date (year or period) of first sighting (or of the
first publication in few cases) in Tunisia, and the status
of the alien (casual, cryptogenic, established or question-
able) according to Zenetos et al. (2010) were evaluated
for each species. Casual species are those having been
recorded only once. Cryptogenic species are species with
no definite evidence of their native or introduced status.
Established species are species known from more than
two Tunisian localities or records. Finally, questionable
species are species with insufficient information. The
species considered as invasive are species that can have
an obvious ecological and/or economic impact.

Field studies

Sixty-seven sampling sites distributed along the
whole of the Tunisian coastline were investigated, from
July 2009 to April 2014 (Fig. 1, Table 1). At each site,
a standardized one-hour transect was surveyed by snor-
keling or/and SCUBA diving in the depth range 0 to 30 m
depth. All the AMM present were listed and, if necessary,
collected for confirmation in the laboratory.

The following voucher specimens were deposited
in the Verlaque Herbarium (HCOM), Marseille, France,
with references: *Hypnea cornuta* (Kützing) J. Agardh,
H8272, dried and wet specimens preserved in 4% buff-
ered formalin/seawater, Sidi Jmour, Jerba, Tunisia,
13/8/2014, coll. J.M. Astier. *Acanthophora nayadiformis*
(Delile) Papenfuss, H8273, dried specimen, Sidi Jmour,
Jerba, Tunisia, 13/8/2014, coll. J.M. Astier.

Mapping

The updated range expansion in Tunisia was estab-
lished for each alien species, taking into account both al-
ready available data and new records. In the distribution

maps, when there was a series of sightings (> 5) with a
maximum distance between consecutive sightings of less
than 50 km, it was assumed that the species was present
along the entire coastline and its distribution was depict-
ed by a continuous line. In all the other cases, sightings
of species were depicted by symbols.

Results

During our survey along the 1400 km of the Tunisian
coast, ten AMM were encountered at 70.1% of sampling
sites: *Acanthophora nayadiformis*, *Asparagopsis armata*,
*A. taxiformis*, *Hypnea cornuta*, *Lophocladia lallemandii*,
*Caulerpa chemnitzia*, *C. cylindracea*, *C. taxifolia*, *Codium
fragile* subsp. *fragile* and *Halophila stipulacea* (Table 1).

*Hypnea cornuta* is reported for the first time from Tu-
nisia. Our specimens are well characterized by their habit
and the presence of stellate vegetative propagules on the
axes (Fig. 2). Sexual reproductive structures were not ob-
served. The species was only found in Jerba in 2014.

On the basis of the available literature and field sur-
veys, a total of 27 AMM is listed for Tunisia: 18 Rhodo-
phyta, 3 Ochrophyta, 5 Chlorophyta and 1 Magnoliophy-
ta (Table 2). For four species, *Bonnemaisonia hamifera*
in 1909, *Gracilaria arcuata* in 1934, *Caulerpa chem-
nitzia* in 1926 and *Caulerpa cylindracea* in 1985, their
discovery in Tunisia constitutes the first reports of each
species in the Mediterranean Sea.

The main putative donor regions are the Red Sea and the Indo-Pacific province (Table 2). Only two species, *Chondria coerulescens* and *Polysiphonia fucoides*, have a distribution restricted to the Atlantic Ocean and the Mediterranean Sea. The other Atlantic species are also present in the Indo-Pacific Ocean. Among these 27 species, we found two casual, seven cryptogenic, 14 established and four questionable species (Table 2).

The first casual species is *Hypnea cornuta*, hith-
ero only known from Jerba, and the second is the Red
Sea Rhodophyta *Gracilaria arcuata* that was originally
described from the Red Sea (Gulf of Aqaba; Zanardini,
1858). Seven species, *Acanthophora nayadiformis*, *Anot-
richium okamurae*, *Chondria coerulescens*, *Colaconema
codicola*, *Polysiphonia atlantica*, *P. fucoides* and *Pylaiella
littoralis*, are regarded as cryptogenic species. *Acantho-
phora nayadiformis* was found for the first time at Jerba.

The status of the Atlantic species *Griffithsia coralli-
noides*, which was collected in the Bizerte Lagoon, was
not considered as cryptogenic but established because an
introduction via oyster transfers is highly probable as in
the case of the French lagoon of Thau (Verlaque, 2001).

The distribution of AMM (casual, cryptogenic and established) differs according to the different areas in Tunisia (Figs 3 & 4). The northern zone has received the highest number of AMM (18 species of which 14 are Rhodophyta and four are Chlorophyta) compared to the
<figure><img src="image_6.png" /><figcaption>Fig. 1: Location of sampling sites in Tunisia. The characteristics of site numbers are given in the Table 1.</figcaption></figure>

central zone (10 species of which five Rhodophyta, four Chlorophyta and one Magnoliophyta), and the southern zone (11 species: seven Rhodophyta, one Ochrophyta, two Chlorophyta and one Magnoliophyta).

On the basis of certain characteristics, such as fast dynamics in areas of introduction, development of dense populations, intense vegetative multiplication, production of repellent metabolites, broad ecological niches and obvious ecological and/or economic impact, 11 species are considered as invasive or potentially invasive in the Mediterranean Sea: *Acrothamnion preissii*, *Asparagopsis armata*, *A. taxiformis*, *Hypnea cornuta*, *Lophocladia lallemandii*, *Womersleyella setacea*, *Caulerpa chemnitzia*, *C. cylindracea*, *C. taxifolia*, *Codium fragile* subsp. *fragile* and *Halophila stipulacea* (Table 2). All of these are widely distributed along the Tunisian coasts except for *A. preissii*, *H. cornuta* and *W. setacea* (Fig. 2).

*Asparagopsis armata* was found at El Kantaoui at 1m depth on rocks. The gametophytic phase of *A. taxiformis* was recorded at eight sampling sites out of 67 (11.9 %).

*Lophocladia lallemandii* was found at 12 sampling sites out of 67 (17.9%). It was well established in the Gulf of Gabes (Kerkennah Islands, 1-13 m depth; eastern Jerba, 4-25m depth) where it was very abundant in July 2009 and 2010 on disturbed and dead *Posidonia oceanica* (Linnaeus) Delile meadows and *Cymodocea nodosa* (Ucria) Ascherson meadows. *Caulerpa chemnitzia* was found at Monastir. Given the features common to all species of *Caulerpa* (mainly: vegetative multiplication, holocarpy, repellent secondary metabolites, permanent and dense meadows), this species is considered as potentially invasive for Tunisia. *Caulerpa cylindracea* was the most frequent AMM, with an occurrence at 34 sampling sites out of the 67 (50.7%). Locally abundant, it grew on soft substrates, dead *Posidonia oceanica* meadows, and in small patches (ca. 2 m²) on rocky substrates. In the Gulf of Gabes, *C. cylindracea* was very common between 0 and 15 m depth on disturbed *P. oceanica* meadows and *C. nodosa* meadows, especially in the south and west of Kerkennah, whereas it was rare at Jerba between
<table><caption>**Table 1.** Sampling sites in Tunisia: GPS coordinates, date, depth, substrate and alien marine macrophytes (AMM) observed. (An: *Acanthophora nayadiformis*; Aa : *Asparagopsis armata*; At : *Asparagopsis taxiformis*; He : *Hypnea cornuta*; Ll : *Lophocladia lallemandii*; Cch : *Caulerpa chemnitzia*; Ccy : *Caulerpa cylindracea*; Ct : *Caulerpa taxifolia*; Cf: *Codium fragile* subsp. *fragile* and Hs : *Halophila stipulacea*).</caption><thead><tr><th>Locality<br>(north to south Tunisia)</th><th>Coordinates<br>(Lat. N - Long. E)</th><th>Date</th><th>Depth<br>(m)</th><th>Substrate</th><th>Alien marine<br>macrophytes</th></tr></thead><tbody><tr><td>1 Malloula</td><td>36.9628-08.7139</td><td>July 2010</td><td>0-5</td><td>Sand/Rock</td><td></td></tr><tr><td>2 TabarkaBay</td><td>36.9708-08.7400</td><td>June 2010</td><td>0-8</td><td>Sand</td><td></td></tr><tr><td>3 TabrakaCap</td><td>36.9603-08.7556</td><td>June 2010</td><td>0-15</td><td>Sand/Rock</td><td></td></tr><tr><td>4 Tabarka Fort</td><td>36.9631-08.7628</td><td>June 2010</td><td>0-10</td><td>Sand/Rock</td><td></td></tr><tr><td>5 Sounine</td><td>37.2114-10.1811</td><td>July 2010</td><td>0-5</td><td>Sand</td><td></td></tr><tr><td>6 Rafraf - Ras Blat</td><td>37.1969-10.2089</td><td>July 2010</td><td>0-5</td><td>Sand/Rock</td><td>Ccy, At</td></tr><tr><td>7 Rafraf - Ras Ettarf</td><td>37.1822-10.2653</td><td>July 2010</td><td>0-5</td><td>Sand</td><td>At</td></tr><tr><td>8 Ghar El Melh lagoon</td><td>37.1625-10.2147</td><td>July 2010</td><td>0-2</td><td>Sand/Mud</td><td>Ccy</td></tr><tr><td>9 La Marsa</td><td>36.8956-10.3219</td><td>May 2011</td><td>0-5</td><td>Sand/Rock</td><td>Ccy</td></tr><tr><td>10 Sidi Bou Saïd</td><td>36.8661-10.3519</td><td>April 2014</td><td>0-1</td><td>Rock</td><td></td></tr><tr><td>11 Salammbo Port punique</td><td>36.8447-10.3272</td><td>April 2014</td><td>0-2</td><td>Rock</td><td></td></tr><tr><td>12 Le Kram</td><td>36.8294-10.3181</td><td>April 2014</td><td>0-3</td><td>Rock</td><td></td></tr><tr><td>13 La Goulette</td><td>36.8172-10.3081</td><td>April 2014</td><td>0-4</td><td>Rock</td><td></td></tr><tr><td>14 Sidi Rais</td><td>36.7703-10.5483</td><td>July 2010</td><td>0-6</td><td>Sand</td><td>Ccy</td></tr><tr><td>15 Hammamet</td><td>36.3956-10.5819</td><td>July 2010</td><td>0-7</td><td>Sand</td><td>Ccy</td></tr><tr><td>16 Hergla City</td><td>36.0353-10.5053</td><td>June 2010</td><td>0-5</td><td>Sand</td><td>Ccy</td></tr><tr><td>17 Hergla - Falaise</td><td>36.0017-10.5231</td><td>June 2010</td><td>0-5</td><td>Sand/Rock</td><td></td></tr><tr><td>18 Chott-Mariem Aquaculture</td><td>35.9650-10.5403</td><td>July 2012</td><td>0-5</td><td>Sand/Rock</td><td>Ct, Cf</td></tr><tr><td>19 Chott-Mariem</td><td>35.9394-10.5603</td><td>July 2010</td><td>0-7</td><td>Sand</td><td>Ccy, Ct, At, Cf</td></tr><tr><td>20 Tantana</td><td>35.9283-10.5728</td><td>July 2013</td><td>0-7</td><td>Sand</td><td>At, Ct</td></tr><tr><td>21 El Kantaoui</td><td>35.9033-10.5914</td><td>March to Dec. 2012</td><td>0-8</td><td>Dead matt/Sand</td><td>Ccy</td></tr><tr><td>22 El Kantaoui</td><td>35.8983-10.5961</td><td>March to Dec. 2012</td><td>0-8</td><td>Dead matt/Sand</td><td>At</td></tr><tr><td>23 El Kantaoui</td><td>35.8919-10.6006</td><td>March to Dec. 2012</td><td>0-8</td><td>Dead matt/Sand/Rock</td><td>At, Ct, Ccy, Cf, Aa</td></tr><tr><td>24 El Kantaoui</td><td>35.8772-10.6053</td><td>March to Dec. 2012</td><td>0-8</td><td>Sand</td><td>Ccy</td></tr><tr><td>25 Monastir Dkhila</td><td>35.7772-10.7736</td><td>July 2010</td><td>0-5</td><td>Sand</td><td>Ct, Ccy</td></tr><tr><td>26 Monastir Marina Cap</td><td>35.7789-10.8353</td><td>May 2011</td><td>0.5-2</td><td>Sand/Muddy sand</td><td>Ccy, Hs, At</td></tr><tr><td>27 Monastir Climant</td><td>35.7900-10.8383</td><td>August 2013</td><td>20-25</td><td>Rock/Muddy sand</td><td></td></tr><tr><td>28 Monastir - Karraïa</td><td>35.7739-10.8378</td><td>May 2011</td><td>0-5</td><td>Sand</td><td>At, Cch</td></tr><tr><td>29 Kuriat Island</td><td>35.7650-11.0075</td><td>July 2010</td><td>0-1</td><td>Sand</td><td>Ccy</td></tr><tr><td>30 Kuriat Island</td><td>35.7661-11.0142</td><td>July 2010</td><td>0-5</td><td>Sand</td><td>Ccy</td></tr><tr><td>31 Kuriat Island</td><td>35.7978-11.0233</td><td>July 2010</td><td>0-3</td><td>Sand</td><td>Ccy</td></tr><tr><td>32 Kuriat Island</td><td>35.8033-11.0286</td><td>July 2010</td><td>0-3</td><td>Sand/Rock</td><td>At</td></tr><tr><td>33 Bekalta</td><td>35.6333-11.0400</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>34 Kerkennah Islands - Abbassya</td><td>34.7097-11.2408</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>35 Kerkennah Islands - Ouled Yaneg</td><td>34.6725-11.1458</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>36 Kerkennah Islands - Ouled<br>Ezzedine</td><td>34.6447-11.0903</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>37 Kerkennah Islands - Allama</td><td>34.6128-11.0478</td><td>July 2010</td><td>0-1</td><td>Sand</td><td>Hs, Ccy</td></tr><tr><td>38 SE Kerkennah Islands</td><td>34.6650-11.2769</td><td>July 2009</td><td>1.0</td><td>Muddy sand/C. nodosa meadow</td><td>Ccy</td></tr><tr><td>39 SE Kerkennah Islands</td><td>34.6872-11.3894</td><td>July 2009</td><td>1.3</td><td>Muddy sand/C. nodosa meadow</td><td>Ccy, Ll</td></tr><tr><td>40 SE Kerkennah Islands</td><td>34.6414-11.2797</td><td>July 2009</td><td>11.9</td><td>Dead P. oceanica meadow/Sand</td><td>Ccy</td></tr><tr><td>41 SW Kerkennah Islands</td><td>34.4383-11.0917</td><td>July 2009</td><td>30.4</td><td>Muddy-Sand</td><td>Ccy</td></tr><tr><td>42 Kerkennah Islands Al Attaya</td><td>34.6869-11.3906</td><td>July 2010</td><td>1.5</td><td>P. oceanica meadow</td><td>Ccy, Hs</td></tr><tr><td>43 SE Kerkennah Islands</td><td>34.6517-11.2717</td><td>July 2010</td><td>6.6</td><td>P. oceanica meadow</td><td>Ccy, Ll</td></tr><tr><td>44 SW Kerkennah Islands</td><td>34.5044-11.0164</td><td>July 2010</td><td>12.4m</td><td>P. oceanica meadow</td><td>Ccy, Ll</td></tr><tr><td>45 SW Kerkennah Islands</td><td>34.5944-11.2756</td><td>July 2010</td><td>20.4m</td><td>Muddy sand</td><td>Ccy</td></tr><tr><td>46 Kneiss Islands</td><td>34.3719-10.3183</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>47 Kneiss Islands Jaboussa</td><td>34.3472-10.2094</td><td>July 2010</td><td>1.0</td><td>Muddy sand</td><td>Hs</td></tr><tr><td>48 W-Jerba</td><td>33.7831-10.7231</td><td>July 2009; 2014 (for Hc)</td><td>8.2</td><td>Rock/sand/C. nodosa meadow</td><td>An, Hc, Ccy</td></tr><tr><td>49 W-Jerba</td><td>33.9475-10.6381</td><td>July 2009</td><td>15.2</td><td>Dead P. oceanica meadow/Sand</td><td>Ll</td></tr><tr><td>50 W-Jerba</td><td>33.9550-10.6928</td><td>July 2010</td><td>13.5</td><td>Dead P. oceanica meadow</td><td>Ccy</td></tr><tr><td>51 E-Jerba</td><td>33.7494-11.0139</td><td>July 2009</td><td>4.2</td><td>C. nodosa & P. oceanica patches</td><td>Ll</td></tr><tr><td>52 E-Jerba</td><td>33.8086-11.0631</td><td>July 2009</td><td>6.9</td><td>C. nodosa & P. oceanica patches</td><td>Ll</td></tr><tr><td>53 E-Jerba</td><td>33.7161-11.1358</td><td>July 2009</td><td>20.4</td><td>Dead P. oceanica meadow</td><td>Ccy, Ll</td></tr><tr><td>54 E-Jerba</td><td>33.8936-11.1256</td><td>July 2009</td><td>25.0</td><td>Dead P. oceanica meadow</td><td>Ccy, Ll</td></tr><tr><td>55 E-Jerba</td><td>33.7492-11.0139</td><td>July 2009</td><td>4.2</td><td>C. nodosa meadow/Coarse sand</td><td>Ll</td></tr></tbody></table>

(continued)
<table><caption>Table 1. (continued)</caption><thead><tr><th>Locality<br>(north to south Tunisia)</th><th>Coordinates<br>(Lat. N - Long. E)</th><th>Date</th><th>Depth<br>(m)</th><th>Substrate</th><th>Alien marine<br>macrophytes</th></tr></thead><tbody><tr><td>56 E-Jerba</td><td>33.8931-11.0947</td><td>July 2009</td><td>19.6</td><td>Dead <i>P. oceanica</i> meadow</td><td>Ccy</td></tr><tr><td>57 E-Jerba</td><td>33.7261-11.1753</td><td>July 2009</td><td>25.8</td><td>Dead <i>P. oceanica</i> meadow</td><td>Ccy</td></tr><tr><td>58 E-Jerba</td><td>33.7814-11.0658</td><td>July 2010</td><td>4.4</td><td>Rock/<i>P. oceanica</i> meadow</td><td>Ccy, Ll</td></tr><tr><td>59 E-Jerba</td><td>33.8119-11.0922</td><td>July 2010</td><td>8.8</td><td>Dense <i>P. oceanica</i> meadow</td><td>Ll</td></tr><tr><td>60 E-Jerba</td><td>33.8136-11.1086</td><td>July 2010</td><td>14.6</td><td>Sparse <i>P. oceanica</i> meadow</td><td>Ll</td></tr><tr><td>61 E-Jerba</td><td>33.7572-11.1097</td><td>July 2010</td><td>17.1</td><td>Dead <i>P. oceanica</i> meadow</td><td>Ccy</td></tr><tr><td>62 Jerba Island - Ajim</td><td>33.7417-10.7342</td><td>July 2010</td><td>0-1</td><td>Sand</td><td>Ccy</td></tr><tr><td>63 Jerba Island - Borj Jeliz</td><td>33.8889-10.7467</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>64 Bou Ghrara Lagoon</td><td>33.6914-10.7428</td><td>July 2009</td><td>2.0</td><td><i>Caulerpa prolifera</i> meadow</td><td>Ccy</td></tr><tr><td>65 Bou Ghrara Lagoon</td><td>33.6222-10.9303</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>66 El Bibane Lagoon - Jedeiria</td><td>33.2869-11.2667</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr><tr><td>67 El Bibane Lagoon - Ben Guerdane</td><td>33.1950-11.3006</td><td>July 2010</td><td>0-1</td><td>Sand</td><td></td></tr></tbody></table>

<figure><img src="image_7.png" /><figcaption>Fig. 2: *Hypnea cornuta* (Kützing) J. Agardh, specimens H8272. A. Dried specimen. B. Axis with young branches. C. Stellate vegetative propagules on the axis. D. Three detached stellate vegetative propagules. Scale bars: A = 1 cm; B-D = 500 µm.</figcaption></figure>
<caption>**Table 2.** Alien marine macrophytes introduced in Tunisia with the native range, the locality and the date of first sighting, with references. Abbreviations: Atl = Atlantic Ocean; Cos = Cos-mopolite; Ind = Indian Ocean; Pac = Pacific Ocean; Pan = Pantropical; Ques = Questionable; RS = Red Sea; Cas = Casual; Cry = Cryptogenic; Est = established. *; Species potentially invasive for Tunisia.</caption>

note ¹: Athanasiadis (1996) separated two other introduced species, *A. boergesenii* (Cormaci & Furnari) Athanasiadis and *A. sublitoralis* (Setchell & Gardner) Athanasiadis, from *A. elegans*. It is not possible to say if other members of this species complex have been introduced in Tunisia.

<table><thead><tr><th rowspan="2">Species</th><th rowspan="2">Native range</th><th rowspan="2">First sighting</th><th rowspan="2">North Tunisia (Western Mediterranean) Status</th><th rowspan="2">References</th><th colspan="2">Central-South Tunisia (Central Mediterranean) References</th></tr><tr><th>First sighting</th><th>Status</th></tr></thead><tbody><tr><td><strong>Rhodophyta</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Acanthophora nayadiformis</em> (Delile)</td><td>RS - Pan</td><td>Carthage, 1931</td><td>Cry</td><td>Feldmann, 1937; Meñez & Mathieson, 1981; Ben<br>Maiz et al., 1987; Ben Maiz, 1995</td><td>Jerba, 2009</td><td>Cry</td><td>Present study</td></tr><tr><td><em>Acrohamnion preissii</em> (Sonder)</td><td>Ind - Pac</td><td>Bizerte, Cap<br>Zebib, Raf-Raf,<br>2005-2006</td><td>Est</td><td>Zerzeri et al., 2010</td><td></td><td></td><td></td></tr><tr><td><em>Anotrichium okamurae</em> Baldock as<br><em>Neomonospora furcellata</em>; Feldmann-<br>Mazoyer and Meslin</td><td>Pac</td><td>Bizerte, 1926</td><td>Cry</td><td>Herbier J. Feldmann, somneratphoto.mnhn.fr; 1938;<br>Ben Maiz et al., 1987</td><td></td><td></td><td></td></tr><tr><td><em>Antihamnionella elegans</em><br>(Berthold) J.H.Price & D.M. John =<br><em>Antihamnion elegans</em> Berthold¹</td><td>Pac</td><td>Zembra, 1969</td><td>Est</td><td>Boudouresque, 1970; Ben Maiz et al., 1987; Ben<br>Maiz, 1995; Djellouli et al., 2000; Boudouresque et<br>al., 2006</td><td></td><td></td><td></td></tr><tr><td><em>Asparagopsis armata</em> Harvey *</td><td>Ind - Pac</td><td>Cap Serrat,<br>1973-1975</td><td>Est</td><td>Meñez & Mathieson, 1981; Ben Maiz<br>& Boudouresque, 1986; Ben Maiz,<br>1995; Boudouresque et al., 2006; Shiili et al., 2010;<br>Zerzeri et al., 2010; present study</td><td>Hammamet,<br>1985</td><td>Est</td><td>Ben Maiz et al., 1987</td></tr><tr><td><em>Asparagopsis taxiformis</em> (Delile)</td><td>Ind-Pac</td><td>North coast,<br>2009</td><td>Est</td><td>Shili et al., 2010; present study</td><td></td><td></td><td></td></tr><tr><td><em>Trevisan de Saint-Léon</em> *</td><td>Pac</td><td>La Galite, 1909</td><td>Est</td><td>Petersen, 1918; Feldmann, 1931; Meñez &<br>Mathieson, 1981; Ben Maiz & Boudouresque,<br>1986; Ben Maiz et al., 1987; Ben Maiz, 1995;<br>Boudouresque et al., 2006</td><td>Mahdia, 2003</td><td>Est</td><td>Andreakis et al., 2004, 2007, 2009; present<br>study</td></tr><tr><td><em>Bonnemaisonia hamifera</em> Hariot =<br><em>Tralliella intricata</em> Batters</td><td>Pac</td><td>Raouad, Sidi<br>Bou Said, La<br>Mursa, 1973-<br>1975</td><td>Cry</td><td>Meñez & Mathieson, 1981; Ben Maiz et al., 1987;<br>Ben Maiz, 1995; Zerzeri et al., 2010</td><td></td><td></td><td></td></tr><tr><td><em>Chondria coeruleoscens</em> (J.Agardh)</td><td>Atl</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Colaconema codicola</em> (Bergesen) H.<br>Stegenga, J.J. Bolton & R.J. Anderson<br>= <em>Acrochaetium codicola</em> Borgesen</td><td>Cos</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><em>Gracilaria arcuata</em> Zanardini</td><td>RS - Ind-Pac</td><td>Carthage, 1931</td><td>Cas/Requires<br>confirmation</td><td>Feldmann, 1931; Meñez & Mathieson, 1981; Ben<br>Maiz et al., 1987; Ben Maiz, 1995</td><td>Sousse, 1973-<br>1975</td><td>Cry</td><td>Meñez & Mathieson, 1981, misspelled<br><em>Acrochaetium codiculum</em>; Ben Maiz et al.,<br>1987</td></tr><tr><td><em>Griffithsia corallinoides</em> (Limnaeus)</td><td>Atl - Pac</td><td>Tabarka, Russ El<br>Fartass, 1969;<br>Bizerte, 1989</td><td>Est</td><td>Boudouresque, 1970; with doubts; Ben Maiz et al.,<br>1987; Ben Maiz, 1995; Djellouli et al., 2000</td><td></td><td></td><td></td></tr><tr><td><em>Hypnea cornuta</em> (Kützing) J. Agardh*</td><td>RS - Pan</td><td></td><td></td><td>Ben Maiz & Boudouresque, 1986; Ben Maiz, 1995;<br>Boudouresque et al., 2006; Zerzeri et al., 2010</td><td>Jerba, 2014</td><td>Cas</td><td>Present study</td></tr><tr><td><em>Hypnea spinella</em> (C. Agardh) Kützing<br>= <em>H. cervicornis</em> J. Agardh</td><td>RS - Pan</td><td>Zembra, 1986</td><td>Est</td><td></td><td>Kerkennah,<br>1995</td><td>Est</td><td>Ben Maiz, 1995</td></tr><tr><td><em>Lophocladia lallemandii</em> (Montagne)<br>F. Schmitz *</td><td>RS- Ind-Pac</td><td></td><td></td><td></td><td>Gabes, 1938</td><td>Est</td><td>Feldmann & Feldmann, 1939; Ben Maiz et al.,<br>1987; Ben Maiz, 1995; present study</td></tr></tbody></table>

(continued)
<table><caption>Table 2. (continued)</caption><thead><tr><th rowspan="2">Species</th><th rowspan="2">Native range</th><th rowspan="2">First sighting</th><th rowspan="2">North Tunisia (Western Mediterranean) Status</th><th rowspan="2">References</th><th colspan="2">Central-South Tunisia (Central Mediterranean) References</th></tr><tr><th>First sighting</th><th>Status</th></tr></thead><tbody><tr><td><i>Polysiphonia atlantica</i> Kaprauand<br/>J.N. Norris = <i>P. macrocarpa</i> Harvey</td><td>Atl - Pac</td><td>Raouad, 1973-1975</td><td>Cry</td><td>Mehez & Mathieson, 1981; Ben Maïz et al., 1987; Ben Maïz, 1995</td><td>Jerba, 1973-1975</td><td>Cry<br/>Mehez & Mathieson, 1981; Ben Maïz et al., 1987; Ben Maïz, 1995</td></tr><tr><td><i>Polysiphonia ficoides</i> (Hudson)<br/>Greville ex Harvey</td><td>Atl</td><td>Carthage, 1969</td><td>Cry</td><td>Ben Alaya, 1972; Mehez & Mathieson, 1981; Ben Maïz et al., 1987; Ben Maïz, 1995</td><td>Nabeul and Jerba, 1973-1975</td><td>Cry<br/>Mehez & Mathieson, 1981; Ben Maïz et al., 1987; Ben Maïz, 1995</td></tr><tr><td><i>Womersleyella setacea</i> (Hollenberg)<br/>R.E. Norris*</td><td>Pan</td><td>Cap Bon, 1996-1997</td><td>Est</td><td>Piazi et al., 2001; 2002</td><td></td><td></td></tr><tr><td><i>Neosiphonia sphaerocarpa</i><br/>(Borgesen) M.S. Kim & I.K. Lee</td><td>Cos</td><td>Golf of Tunis, 1970</td><td>Ques</td><td>Ben Alaya, 1970</td><td></td><td></td></tr><tr><td><strong>Ochrophyta</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><i>Pylaiella littoralis</i> (Linnaeus)</td><td>Atl</td><td></td><td></td><td></td><td>Sfax, 1924</td><td>Cry<br/>Schiffner, 1926, Ben Maïz et al., 1987</td></tr><tr><td><i>Kjellman</i><br/>Leathesia marina (Lyngbye) Decaisne<br/>= Leathesia differmis Areschoug</td><td>Atl</td><td>Tunisia, 1992</td><td>Ques</td><td>Ribera et al., 1992</td><td></td><td></td></tr><tr><td><i>Padina boryana</i> Thivy = <i>P. tenuis</i><br/>Bory</td><td>Pac</td><td>Bay of Tunis, Tabarka and Ain Oktor, 1991</td><td>Ques</td><td>Nizamuddin, 1981</td><td>Gulf of Gabes, 1991</td><td>Ques<br/>Nizamuddin, 1981</td></tr><tr><td><strong>Chlorophyta</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><i>Caulerpa chemnitzia</i> (Esper)<br/>J.V.Lamouroux* = C. racemosa var.<br/>chemnitzia (Esper) Weber-Van Bosse<br/>= C. racemosa var. turbinata (J.<br/>Agardh) Eubank</td><td>RS - Pan</td><td>Cani Island and Bizerte harbour, 1997</td><td>Est</td><td>Verlaque et al., 2000, 2003; Djellouli et al., 2006</td><td>Sousse, 1926</td><td>Est<br/>Hamel, 1926; Ben Alaya, 1971; Ben Maïz, 1985; 1995; Ben Maïz et al., 1987; Ben Mustapha & Hattour, 1992; Bradai & Jribi, 1997; Belkhira, 1999; Verlaque et al., 2000, 2003; Ben Mustapha et al., 2002, 2004; Langar et al., 2002, 2007; Ben Mustapha & Aflï, 2007; Mezgui et al., 2007; Shili et al., 2010; Zerzeri et al., 2010; present study</td></tr><tr><td><i>Caulerpa cylindracea</i> Sonder * = C. racemosa var. cylindracea (Sonder)<br/>Verlaque, Huissman & Boudouresque</td><td>Ind-Pac</td><td>North coast, 1996</td><td>Est</td><td>Djellouli, 2000; Ben Mustapha et al., 2002; 2004; Langar et al., 2006; 2007; Piazi et al., 2005; Djellouli et al., 2006; Ben Mustapha & Aflï, 2007; Mezgui et al., 2007; 2010a, b; 2014; Shili et al., 2010; Zerzeri et al., 2010; present study</td><td>Mellita, 1985</td><td>Est<br/>Hamza et al., 1995; Djellouli, 2000; Ben Mustapha & Hattour, 1992; Ben Mustapha et al., 2002, 2006, 2007; Piazi et al., 2005; Djellouli et al., 2006; Ben Mustapha & Aflï, 2007; Ben Mustapha & Aflï, 2007; Zaoali & Ben Charrada, 2010; Shili et al., 2014; present study</td></tr><tr><td><i>Caulerpa taxifolia</i> (Vahl) C. Agardh *<br/>Codium fragile subsp. fragile<br/>(Suringar) Hariot *</td><td>Pac</td><td>Sidi Daoud, 2001</td><td>Est</td><td>Langar et al., 2006, 2007, 2010; Ben Mustapha et al., 2004; Ben Salem et al., 2004; Ben Mustapha & Aflï, 2007; Ben Salem & Gaamour, 2007</td><td>Sousse, 2000</td><td>Est<br/>Chot-Mariem, 2010<br/>Present study</td></tr><tr><td><i>Ulva lactuca</i> Linnaeus</td><td>Cos</td><td>Bizerte, 1985</td><td>Est</td><td>Djellouli, 1987; Ben Maïz, 1995; Shili et al., 2010, 2014; Zerzeri et al., 2010</td><td></td><td></td></tr><tr><td><strong>Magnoliophyta</strong></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td><i>Halophila stipulacea</i> (Forsskål)<br/>Ascherson *</td><td>RS - Ind</td><td>North Coast, Bay of Tunis, 1987</td><td>Ques</td><td>Ben Maïz et al., 1987</td><td>Hammamet Golf, 1987</td><td>Ques<br/>Ben Maïz et al., 1987</td></tr></tbody></table>
<figure><img src="image_8.png" /><figcaption>**Fig. 3:** Records of alien marine macrophytes (established, casuals, cryptogenic) by species in Tunisia until 2014. Black symbols and yellow lines: available historical data; red symbols: new records.</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>Fig. 4: Number of alien marine macrophytes (established, casuals, cryptogenic) recorded in Tunisia until 2014.</figcaption></figure>

9 and 24 m depth. *Caulerpa taxifolia* was found at five sampling sites out of 67 (7.5%). *Codium fragile* subsp. *fragile* was uncommon in Tunisia, with occurrences at only three sampling sites out of the 67 (4.5 %). It grew between 1 and 5 m depth on hard substrates.

Like *Asparagopsis taxiformis*, *Halophila stipulacea* is a recent invader in Tunisia with a first sighting in 2003 at Sfax (Missaoui *et al.*, 2003). During field studies, the species was observed at the Cap Monastir and the Kerkennah Islands (4.5% of sampling sites).

### Questionable species

*Neosiphonia sphaerocarpa* (Børgesen) M.S. Kim & I.K. Lee (Rhodophyta)

Cormaci *et al.* (2004) considered *N. sphaerocarpa* to be introduced in the Mediterranean Sea where the species was first recorded in 1970 from Tunisia (Ben Alaya, 1970, misspelled *P. sphaerocaspa*). However, the species is distributed worldwide and molecular data are needed to locate its place of origin. Moreover, its identification is not easy, so the absence of *N. sphaerocarpa* in the Mediterranean prior to 1970 could simply mean that it was overlooked or mistaken for another species. Pending further investigations, Tsiamis *et al.* (2010) provisionally consider this species as native in the Mediterranean Sea.

*Leathesia marina* (Lyngbye) Decaisne (Ochrophyta)

Described from Scandinavia (Lyngbye, 1819, as *Chaetophora marina*), *L. marina* was introduced along the French Mediterranean coasts (Verlaque, 2001). Ribera *et al.* (1992) reported the species (as *L. difformis*)

from Tunisia, referring to Ben Maiz *et al.* (1987), but these authors cited only the native species *L. mucosa* J. Feldmann. The occurrence of *L. marina* in Tunisia is possible since it was recorded from Sicily (Marino *et al.*, 1998), but as for other Atlantic species, its status in the southern Mediterranean Sea is cryptogenic.

*Padina boryana* Thivy (Ochrophyta)

The species was reported from Tunisia (Bay of Tunis, Gulf of Gabes, Tabarka and Ain Oktor) (Nizamuddin, 1981, as *P. tenuis* Bory) but Verlaque *et al.* (2015) considered these records as doubtful.

*Ulva lactuca* Linnaeus (Chlorophyta)

This species has frequently been reported from Tunisia (see Ben Maiz *et al.*, 1987). However, all the records of *U. lactuca* over the past 200 years refer to another species (Butler, 2007; F. Mineur, pers. comm.) and should be cited as *U. lactuca auctores*. The genuine *U. lactuca* is a warm water species long misspelled as *U. fasciata*. Delile, a later heterotypic synonym taxon described from Alexandria (Egypt) (Delile, 1813, 1826) and distributed worldwide. Its introduction, probably from Japan, was identified with certainty in France (Verlaque, 2001; Verlaque *et al.*, 2015). Along the North Africa coasts, the species was reported as *U. fasciata* from Algeria, Egypt, Libya and Morocco (Bazairi *et al.*, 2013; Verlaque *et al.*, 2015), so its presence in Tunisia is highly probable. The introduced status of *U. lactuca* in the southern Mediterranean Sea is cryptogenic.

### Discussion

A total of 27 alien marine macrophytes were recorded from Tunisia, which is low compared to the 129 AMM listed for the Mediterranean Sea (Verlaque *et al.*, 2015). However, compared to nearby Mediterranean regions, this number is close to that reported in the Straits of Sicily (18) (Occhipinti-Ambrogi *et al.*, 2011) and Algeria (17) (Verlaque *et al.*, 2015), and higher than those recorded in Malta (12) (Sciberras & Schembri, 2007; Evans *et al.*, 2015a,b; Schembri *et al.*, 2015), and Libya (14) (Bazairi *et al.*, 2013). This number has greatly increased since the late 20th century, with sixteen new AMM reported after 1960. *Hypnea cornuta* is reported for the first time from Tunisia. This pantropical species was recorded first in the Mediterranean Sea in 1894 from Rhodes Island, Greece (Reinbold, 1898, as *H. valentiae* (Turner) Montagne), and was successively recorded in Israel (Nemlich & Danin, 1964; Hoffman & Dubinsky, 2010), Syria (Mayhoub, 1976, as *H. hamulosa* (Esper) J.V. Lamouroux), Egypt: Alexandria (Aleem, 1993), Lebanon (Lakkis & Novel-Lakkis, 2000, as *H. hamulosa*), Italy: Mar Piccolo di Taranto (Cecere *et al.*, 2004) and Sicily: Cape Peloro Lagoon (Manghisi *et al.*, 2011), and Saronikos Gulf, Greece (Tsiamis *et al.*, 2010). Although *H. cornuta* was only found at Jerba, its
casual status needs to be confirmed. The species could be
more widely distributed in Tunisia since, in the absence
of the characteristic propagules, the species can be easily
confused with *H. spinella*.

*Gracilaria arcuata*, the second casual species, was
first reported in the Mediterranean Sea from Carthage
(Feldmann, 1931), before being successively recorded
from Egypt (Alexandria; Aleem, 1993) and Turkey (Sea of
Marmara; Taşkin *et al.*, 2008). A report without description
from France (Corsica; De Casabianca *et al.*, 1972-1973, as
*G. cf. arcuata*) is considered as a misidentification (Ver-
laque *et al.*, 2015). According to Gargiulo *et al*. (1992),
all the Mediterranean records of *G. arcuata* are doubtful.
Consequently, its introduction into the Mediterranean Sea
and its occurrence in Tunisia require confirmation.

Of the 27 alien marine macrophytes of Tunisia, 14
species (51.9% of total number of species) are classified
as established and seven as cryptogenic (25.9%). Most
of AMM are widely distributed and the apparently re-
stricted distribution of the others may be an artifact due
to insufficient investigation.

As far as the cryptogenic species are concerned,
*Acanthophora nayadiformis*, a species described from
both the Red Sea (Suez, Egypt) and the Mediterranean
Sea (Alexandria, Egypt) (Delile, 1813, 1826, as *Fucus
nayadiformis*), was successively reported throughout the
Mediterranean basin. Although Cormaci *et al*. (2004) did
not consider the species as introduced into the Mediter-
ranean Sea, the oldest Mediterranean records are after the
opening of the Suez Canal. Jerba constitutes its southern-
most locality for the Tunisia.

Under the name *Anotrichium okamurae*, two cryptic
taxa have been confused in the Atlantic Ocean and the
Mediterranean Sea: *A. furcellatum* (J. Agardh) Baldock,
a Mediterranean species described from Naples (Agardh,
1842, as *Griffithsia furcellata*), and *A. okamurae*, an intro-
duced species described from Japan (Okamura, 1934, as
*Monospora tenuis*) exhibiting an invasive behaviour pat-
tern. Cormaci *et al*. (2004) did not consider *A. okamurae*
as a putative introduced species. However, in the absence
of molecular studies, we consider that it is preferable to
maintain *A. okamurae* and *A. furcellatum* as distinct spe-
cies. The identity and the introduced or native status of the
Tunisian populations need further investigation.

The introduction of *Chondria coeruleoscens*, *Co-
laconema codicola*, *Polysiphonia atlantica*, *P. fucoides*
and *Pylaiella littoralis*, five species described from the
north-eastern Atlantic Ocean (Linnaeus, 1753; Hudson,
1762; Agardh, 1863; Børgesen, 1927; Kapraun & Nor-
ris, 1982), were identified with certainty along the French
Mediterranean coasts (Ben Maiz, 1986; Verlaque & Ri-
oual, 1989; Verlaque, 2001; Verlaque *et al*., 2015). How-
ever, these species are widely distributed in the Medi-
terranean Sea and the co-occurrence of introduced and
native populations cannot be excluded, especially along
the North African coasts where the native flora pos-

sesses many Atlantic-Mediterranean species. Moreover,
although the introduction of *C. codicola* in Tunisia is
highly probable since its privileged host *Codium fragile*
is established, this requires confirmation because the sin-
gle Tunisian record was epiphytic on *Cymodocea nodosa*
(Meñez & Mathieson, 1981). Consequently, the confir-
mation of the introduced status for each of these species
in Tunisia calls for further studies.

Some localities such as Bizerte, El Kantaoui, Cap
Monastir and Tunis displayed a high number of recorded
aliens compared to the average, confirming that hotspots
for marine species introduction are coastal lagoons and
harbours where human activities such as shipping and
fishing activities, recreational marinas and aquaculture
affect the health of ecosystems and facilitate the introduc-
tion and the secondary dispersal of alien species (Cohen
& Carlton, 1998; Verlaque, 2001; Occhipinti-Ambrogi
& Savini, 2003; Rilov & Crooks, 2009; Hoffman et al.,
2011; Occhipinti-Ambrogi et al., 2011).

Most of the AMM in Tunisia show warm-water affin-
ities since only five North Atlantic AMM can be consid-
ered as cold-water species. As expected, the main donor
regions are the Red Sea and the Indo-Pacific province.
The identity and abundance of AMM in Tunisian waters
could be explained by its southern geographical position
located at the crossroads between the eastern and western
basins of the Mediterranean Sea.

On the 21 invasive or potentially invasive AMM
listed by Zenetos et al. (2010), nine have been identified
in Tunisia: *Acrothamnion preissii*, *Asparagopsis armata*,
*A. taxiformis*, *Lophocladia lallemandii*, *Womersleyella
setacea*, *Caulerpa cylindracea*, *C. taxifolia*, *Codium
fragile* subsp. *fragile* and *Halophila stipulacea*. To this
list, we have added *Caulerpa chemnitzia* and *Hypnea
cornuta* that are spreading in the Mediterranean Sea. In
Tunisia, all of them were already widely distributed in
2014 except for *A. preissii*, *H. cornuta* and *W. setacea*,
whose apparent scarcity could be merely an artefact due
to problems of identification in the field.

*Asparagopsis armata* was first recorded in Tunisia (Cap Serrat) in the 1970s (Meñez & Mathieson, 1981). By 2010, it was reported on the north-east coast of Tunisia (Bizerte, Cap-Zebib and Raf-Raf) (Zerzeri *et al.*, 2010). Our new record was approximately 300 km south of its previously documented distribution in Tunisia.

*Asparagopsis taxiformis* was only recently recorded
from Tunisia (Andreakis *et al.*, 2004). Since 2003, it has
been observed, from 0 to 10 m depth, on rocky substrates
and dead *Posidonia oceanica* meadows. On the four *As-
paragopsis taxiformis* lineages hitherto identified in the
world, two occur in the Mediterranean Sea: the non-in-
vasive lineage 3 of putative Atlantic origin and the inva-
sive lineage 2 originate from the Indo-Pacific region. The
invasive lineage 2 was identified at Mahdia (Andreakis
*et al.*, 2004, 2007, 2009). The identification of lineage(s)
occurring in the other Tunisian localities requires further
investigation; however, the recent spread observed in the central zone of Tunisia is in good agreement with the invasive behaviour of lineage 2.

Caulerpa chemnitzia was first reported from the Mediterranean Sea in 1926 in Tunisia (Sousse Harbour; Hamel, 1926). Hereafter, it remained restricted to the eastern basin (Cyprus, Egypt, Israel, Lebanon and Syria) for a long time. Since the early 21st century, the species has been spreading in the Mediterranean Sea. It was recently discovered in Algeria (Verlaque et al., 2015) and the number of populations is increasing in Tunisia.

Until 2010, *Caulerpa taxifolia* was locally very abundant in Tunisia, forming dense extensive meadows on soft substrates and dead *Podisonia oceanica* meadows. However, in late 2011 and early 2012, the abundance of *C. taxifolia* declined significantly (up to 90%) in the central zone of Tunisia (pers. obs.).

The record of *Codium fragile* at El Kantaoui was approximately 300 km south of the previously documented range of distribution in Tunisia.

The most harmful alien marine macrophytes in Tunisia is probably *Caulerpa cylindracea*. Its rapid spread in the Mediterranean Sea has profoundly altered benthic communities and reduced seaweed diversity (Piazzi *et al.*, 2005; Klein & Verlaque, 2008). It is worth noting that, contrary to the generally accepted opinion, the first observation of the species in the Mediterranean Sea was not in Libya in 1990 (Nizzamudin, 1991), but five years earlier in 1985 in Tunisia, at Mellita (see Hamza *et al.*, 1995). This point, which has hitherto gone unnoticed, is important because it dates the introduction of the two invasive *Caulerpa* species, *C. cylindracea* and *C. taxifolia*, into the Mediterranean Sea during the same period (1984-1985) (see Meinesz & Hesse, 1991, for *C. taxifolia*).

As far as the other potentially invasive AMM in Tunisia are concerned, the literature reports a conspicuous ecological impact in the invaded regions for *Acrothamnion preissii*, *Lophocladia lallemandii*, *Womersleyella setacea*, *Caulerpa taxifolia*, *Codium fragile* and *Halophila stipulacea* (Verlaque & Fritayre, 1994; Villèle & Verlaque, 1995; Piazzi *et al.*, 2001, 2002, 2012; Provan *et al.*, 2005; Ballesteros *et al.*, 2007; Willette & Ambrose 2009, 2012).

In conclusion, the high number of potentially invasive alien marine macrophytes already introduced in the country and its geographical position between the eastern and the western Mediterranean basins, on the westward migration route of Lessepsian species, make the monitoring of alien marine species in Tunisia a scientific priority.

## Acknowledgements

The authors would like to thank Mrs. Michèle Ret-Boudouresque for bibliographic help and Michael Paul for revising the English text. The project "Management of Port areas in the MEDiterranean Sea Basin

(MAPMED)” has been funded by ENPI CBC MED Cross-Border Cooperation. This publication has been produced with the financial assistance of the European Union under the ENPI CBC Mediterranean Sea Basin Programme. The contents of this document are the sole responsibility of the Faculty of Sciences of Tunis and can under no circumstances be regarded as reflecting the position of the European Union or of the Programme's management structures.

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