SCIENTIA M ARINA 82(1) March 2018, 55-66, Barcelona (Spain) ISSN-L: 0214-8358 https://doi.org/10.3989/scimar.04675.07A Overview on the distribution of gorgonian species in Tunisian marine coastal waters (central Mediterranean) Raouia Ghanem 1 , Emna Soufi Kechaou 2 , Jamila Ben Souissi 1,2 , Joaquim Garrabou 3 1 Université de Tunis El Manar, Faculté des Sciences de Tunis, Laboratoire de Biodiversité, Biotechnologie et Changement Climatique LR11ES09, 1002 Tunis, Tunisie. (RG) E-mail: [email protected] . ORCID-iD: https://orcid.org/0000-0001-6947-582X (JBS) (Corresponding autor) E-mail: [email protected] . ORCID-iD: https://orcid.org/0000-0003-1761-4204 2 Université de Carthage, Institut National Agronomique de Tunisie (INAT), 1082 Tunis, Tunisie. (ESK) E-mail: [email protected] . ORCID-iD: https://orcid.org/0000-0003-2852-2727 3 Institut de Ciències del Mar, CSIC, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain. (JG) E-mail: [email protected] . ORCID-iD: https://orcid.org/0000-0001-9900-7277 Summary: Gorgonian species play an important ecological role in the structure and function of marine communities. Human activities are negatively affecting the conservation status of gorgonian populations in the Mediterranean. Acquiring knowl - edge of gorgonian distribution is therefore a key step required to promote efficient management and conservation actions. However, information on the distribution of gorgonian species is lacking in many Mediterranean areas. This study aimed to provide an overview of the geographic and bathymetric distributions of gorgonians in the coastal waters of the Tunisian coast (1136 km). The sampling design encompassed three sectors, 27 localities and 87 sites. Information was collected from scuba diving (26 sites) and local ecological knowledge surveys of fishermen and divers (132 interviews), as well as from a litera - ture review. Overall, the occurrence of eight gorgonians was confirmed at 54 out of the 87 sites surveyed in Tunisian coastal waters (7-120 m depth). The species that were found were Eunicella singularis, Eunicella cavolini, Paramuricea clavata, Paramuricea macrospina, Leptogorgia sarmentosa, Eunicella verrucosa, Corallium rubrum and Ellisella paraplexauroides . The highest gorgonian species richness and abundance was recorded in northern, followed by eastern Tunisian waters. In the southern areas only one species was recorded. This pattern was related to the rocky substrate that characterizes the northern and eastern coasts of Tunisia. This study is the first to report the occurrence of E. singularis, E. cavolini, E. verrucosa and Leptogorgia sarmentosa in northern and eastern Tunisian waters. The results are discussed in the hope of guiding future conservation and management actions for gorgonian assemblages in Tunisia. Keywords: sea fans; coralligenous; octocorals; scientific diving; Tunisia; local ecological knowledge; conservation. Distribución de las especies de gorgonias en las aguas costeras marinas de Túnez (Mediterráneo Central) Resumen: Las especies de gorgonias juegan un papel ecológico importante en la estructura y función de las comunidades marinas. Las perturbaciones asociadas a las actividades humanas están afectando negativamente el estado de conservación de las poblaciones de gorgonias en el Mediterráneo. Conocer la distribución de las especies de gorgonias es una etapa clave para promover planes de gestión y acciones de conservación eficaces. Sin embargo, en muchas áreas del Mediterráneo no disponemos de información sobre la distribución de las especies de gorgonias. Este estudio tiene como objetivo proporcionar una visión general de la distribución geográfica y batimétrica de las especies de gorgonias en las costas de Túnez (1136 km). El diseño del muestreo abarcó 3 sectores, 27 localidades y 87 estaciones de muestreo. Se recolectó información a través de muestreos con escafandra autónoma (26 estaciones), entrevistas a pescadores y buceadores (132 entrevistas) aplicando las técnicas de Local Ecological Knowledge (LEK), así como de una revisión de la literatura disponible. En general, la presen - cia de ocho gorgonias se confirmó en 54 de las 87 estaciones de muestreo en la costa de Túnez (7-120 m de profundidad). Las especies encontradas fueron Eunicella singularis, Eunicella cavolini, Paramuricea clavata, Paramuricea macrospina, Leptogorgia sarmentosa, Eunicella verrucosa, Corallium rubrum y Ellisella paraplexauroides . La riqueza y abundancia de especies de gorgonias fueron más elevadas en la costa del Norte de Túnez seguida por la costa Este. En la costa del Sur solo se encontró una única especie de gorgonia. Este resultado se ha relacionado con la mayor proporción de sustrato rocoso presente a las costas del norte y este de Túnez. Este estudio permitió citar la presencia por primera vez de las especies de gorgonias Eunicella singularis, E. cavolini, E. verrucosa y Leptogorgia sarmentosa en la costa del norte y este de Túnez. Los resultados obtenidos pretenden contribuir a la adopción de acciones de gestión y conservación de las poblaciones de gorgonias en Túnez. Palabras clave: gorgonias; coralígeno; octocorales; buceo científico; Túnez; conocimiento ecológico local; conservación. Citation/Como citar este artículo : Ghanem R., Soufi Kechaou E., Ben Souissi J., Garrabou J. 2018. Overview on the dis - tribution of gorgonian species in Tunisian marine coastal waters (central Mediterranean). Sci. Mar. 82(1): 55-66. https://doi. org/10.3989/scimar.04675.07A 56 • R. Ghanem et al. Editor: M.J. Uriz. Received: June 12, 2017. Accepted: December 22, 2017. Published: February 14, 2018. Copyright : © 2018 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License. INTRODUCTION diving surveys. The study was intended to cover all gorgonian species. However, since the analysis Mediterranean gorgonian species play an impor - of the available data revealed that the information tant ecological role in the structure and function of available for deep gorgonians (>200 m depth) could marine benthic communities (Ballesteros 2006, Kip - not be updated, we decided to focus in gorgonian son et al. 2014, Ponti et al. 2014). In general, they species dwelling in coastal waters (0-120 m depth). are long-lived species that display slow population The ultimate goal of this study is to guide the design dynamics, making them vulnerable to strong distur - of management and conservation strategies for gor - bance events (Garrabou and Harmelin 2002, Cerrano gonian species and the habitat that they characterize et al. 2013, Teixido et al. 2013). Indeed, gorgonian in Tunisian waters. forests are especially vulnerable to the combined ef - fects of multiple stressors associated with human ac - MATERIALS AND METHODS tivities such as direct and indirect fishing activities, pollution, habitat destruction and, more recently, Study sites and sampling effort climate warming (Bavestrello et al. 1997, Cerrano and Bavestrello 2008, Cerrano et al. 2013). Dramatic The study was carried out along Tunisian coasts decreases in the abundance of gorgonian populations including the main islands. To present the information have been reported in many areas of the Mediter - on the distribution of gorgonian species along Tunisian ranean Sea (Garrabou et al. 2009, Bo et al. 2014, coasts, three sectors were considered on the basis of Garrabou et al. 2017). For instance, mass mortalities the hydrographic and geomorphological features of the associated with temperature anomalies have affected bottoms (Fig. 1). In addition, to compile the informa - populations of several species in different Mediterra - tion on the distribution, in each sector we screened nean areas over the last several decades (Garrabou et the presence of gorgonian species in different locali - al. 2009, Rivetti et al. 2014, Marbà et al. 2015). The ties, in which several sites were surveyed by different observed decline supported the inclusion of several methods. Thus, the information encompassed different gorgonian species in different conservation frame - spatial scales: sector (10 2 km), locality (10 km) and works at national and international levels (Otero et site (1 km). A total of 27 localities and 87 sites were al. 2017). In addition to measures at the species level, investigated (Table 1). the Action Plan for coralligenous assemblages by the Sector 1 stretches from the Algerian border to Kéli - Barcelona Convention has been adopted and includes bia, which covers 393 km of coastline and is part of some gorgonian species that are key species of these the western basin of the Mediterranean Sea (WMED). high-diversity Mediterranean assemblages with high In sector 1, data from 11 localities and 49 sites were ecological, socio-economic and heritage values (UN obtained (Table 1). Environment/MAP 2017, Linares et al. 2008, Bouafif Sector 2 comprises the area between Kélibia and et al. 2014). Ras Kapudia ( 261 km of coastline). In sector 2, data Mapping the gorgonian populations is a basic from 9 localities and 21 sites were obtained (Table 1). step required to implement effective management Sector 3 extends from Ras Kapudia to the Libyan and conservation measures. In general, there is a border, including the Gulf of Gabès ( 482 km coast - knowledge gap in the geographic and bathymetric line). In sector 3, data from 7 localities and 17 sites distribution of gorgonian species in the Mediterra - were obtained (Table 1). nean. However, information on the