EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmospheric Atmospheric Chemistry Chemistry and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Biogeosciences, 10, 4009–4036, 2013 Open Access www.biogeosciences.net/10/4009/2013/ Biogeosciences doi:10.5194/bg-10-4009-2013 Biogeosciences Discussions © Author(s) 2013. CC Attribution 3.0 License. Open Access Open Access Climate Climate of the Past of the Past Discussions Diversity, distribution and spatial structure of the cold-water coral Open Access Open Access fauna of the Azores (NE Atlantic) Earth System Earth System Dynamics 1 1 1 1 ´ 1 2Dynamics 1 A. Braga-Henriques , F. M. Porteiro , P. A. Ribeiro , V. de Matos , I. Sampaio , O. Ocana˜ , and R. S. Santos Discussions 1Centre of IMAR of the University of the Azores, Department of Oceanography and Fisheries (DOP) and LARSyS Associated Laboratory, Rua Prof. Dr. Frederico Machado 4, 9901-862 Horta, Portugal Open Access Open Access 2Fundacion´ Museo del Mar, Autoridad Portuaria de Ceuta, Muelle Canonero,˜ 51001 Ceuta (NorthGeoscientific Africa), Spain Geoscientific Instrumentation Instrumentation Correspondence to: A. Braga-Henriques ([email protected]) Methods and Methods and Received: 29 November 2012 – Published in Biogeosciences Discuss.: 9 January 2013 Data Systems Data Systems Revised: 9 April 2013 – Accepted: 8 May 2013 – Published: 19 June 2013 Discussions Open Access Open Access Geoscientific Geoscientific Abstract. Cold-water corals are widely considered as impor- may instead reflect assemblage variability among features. Model Development tant structural components of benthic habitats, potentially en- Stronger changesModel in species Development composition were found along Discussions hancing local abundance in a variety of fish and invertebrate the bathymetric gradient. Notwithstanding the mix of par- species. Yet, current knowledge of the taxonomic diversity tially overlapping steno- and eurybathic species that charac- Open Access and distribution patterns of these vulnerable, slow-growing terize the vertical distribution of corals, thereOpen Access is a distinct organisms is scarce and fragmented, limiting the effective- transition from shallowHydrology (100–600 m) to and intermediate (600– Hydrology and ness of spatial management and conservation measures. We 1000 m) depths. The analysisEarth presented System here constitutes a Earth System have conducted an exhaustive compilation of records of al- valuable contribution for efficient conservation policies of cyonaceans, antipatharians, scleractinians and stylasterids coral-associated vulnerable marineSciences ecosystems and their sus- Sciences available through present day to assess the diversity, distribu- tainable use as fishing areas. Discussions Open Access tion and spatial structure of coral assemblages in the Azores Open Access exclusive economic zone (EEZ). The resulting database com- Ocean Science prises 2501 entries concerning historical oceanographic ex- Ocean Science Discussions peditions and other published sources, as well as unpublished 1 Introduction data from bottom longline by-catch. Our taxonomic inven- tory appears to be fairly complete for the explored habitats, Cold-water corals are currently recognized as vulnerable and Open Access Open Access accounting for 164 species (79 alcyonaceans, 58 scleractini- worth conserving due to their slow growth (e.g. Sherwood ans, 18 antipatharians and 9 stylasterids), nine of which were and Edinger, 2009; Roark et al., 2009; Carreiro-Silva et al., Solid Earth 2013) and their important roleSolid as structural Earth elements that documented for the first time. The Azores EEZ harbours a Discussions mixed coral fauna with several zoogeographic origins, show- enhance habitat complexity and heterogeneity (FAO, 2009; ing the closest affinity with the Lusitanian–Mediterranean re- Buhl-Mortensen et al., 2010; OSPAR, 2010; Auster et al., 2011). Widely distributed throughout the world’s oceans, gion. Very few apparent endemics were found (14 %), and Open Access Open Access only in part supported by consistent sampling. Coral diver- they can be found on continental shelves and margins, edges sity is particularly high between 300 and 900 m depths, in and slopes of oceanic islands, seamounts, canyons and ridges The Cryosphere (e.g. Cairns, 2007; WarehamThe Cryosphere and Edinger, 2007; Molodtsova areas recognized as traditional fishing grounds or exploitable Discussions fish habitat within the 100-mile limit of the EEZ. The com- et al., 2008; Mortensen et al., 2008; Reveillaud et al., 2008; position of coral assemblages shows significant geographi- Baker et al., 2012), especially in areas of high currents and/or cal structure among longitudinal sections of the study area enhanced suspended or re-suspended organic matter (Davies at comparable depths (100–1500 m). There is no evidence et al., 2009; Guinan et al., 2009). 2 of a possible role of the Mid-Atlantic Ridge or latitudi- Occupying an area of almost one million km in the north- nal effects underlying this pattern, which suggests that it east Atlantic, the exclusive economic zone (EEZ) of the Azores archipelago comprises a rich submarine topography Published by Copernicus Publications on behalf of the European Geosciences Union. 4010 A. Braga-Henriques et al.: Cold-water corals of the Azores reaching 5000 m depths. Calculations based on bathymetry 2 Material and methods data identified the presence of 63 large and 398 small seamount-like features in the area (Morato et al., 2008), thus 2.1 Study area making it suitable for corals. Major oceanographic expeditions during the late nine- The Azores EEZ is located in the NE Atlantic near the triple teenth century and throughout the 1900s (e.g. Josephine, junction of the North American, Eurasian and African plates Challenger, Talisman, campaigns of the Prince Albert I of between 33◦460 N–42◦570 N, 35◦450 W–21◦050 W (Fig. 1). It Monaco – PAM, Biac¸ores and Bartlett) were a rich source comprises nine volcanic islands of recent origin (Azevedo of coral records. Until recently, this information had been et al., 1991) with narrow shelves and steep slopes, spread scattered throughout numerous reports and taxonomic publi- along a NW–SE-trending strip 600 km long, with the Mid- cations lacking a common taxonomic nomenclature and of- Atlantic Ridge (MAR) separating the islands of Flores and ten difficult to access. Hall-Spencer et al. (2007) launched Corvo, to the west, from the remaining island groups. Nu- an online database comprising part of the historical records merous seamounts of very different size, shape and depth are from PAM and Biac¸ores campaigns regarding scleractinian, scattered throughout the study area (Morato et al., 2008). antipatharian and gorgonian taxa (exclusive of five families Ocean circulation patterns in the Azores are complex (San- from the order Alcyonacea) found at depths > 200 m. For the tos et al., 1995; Alves and Verdiere,` 1999; Johnson and Azores, only 46 taxa were included in the database. A syn- Stevenson, 2000). Large-scale circulation is dominated by thesis of all prior key campaigns and other available infor- two eastward-flowing branches of the Gulf Stream: the cold mation on past coral records, covering a broader taxonomic North Atlantic Current (NAC) in the north, crossing the range, is still lacking for the Azores. This step is essential MAR between 45–48◦ N (Bower et al., 2002), and the warm to build a database that will enable investigating patterns of Azores Current (AzC) in the south, which crosses the MAR species distributions on a regional scale. between 34–36◦ N (Alves and Verdiere,` 1999). One addi- Ongoing efforts to map, describe and catalogue benthic tional eastward flow can be traced between the NAC and the communities of the Azores using video surveys are contribut- AzC around 39–42◦ N (Reverdin et al., 2003). Mesoscale ed- ing to the discovery of coral gardens (Braga-Henriques et al., dies also occur on both sides of the AzC (Alves and Verdiere,` 2012; Tempera et al., 2012), providing inputs to the EUNIS 1999). The Azores is a transitional region between subtropi- European hierarchical biotope classification system (Galpar- cal and temperate climates. Sea temperature is characterized soro et al., 2012) and to the OSPAR Convention for the Pro- by horizontal gradients enhanced by the NAC and the AzC tection of the Marine Environment of the North-East Atlantic flows (Bashmashnikov et al., 2004). (OSPAR, 2010). However, this information is spatially re- stricted due to logistical constraints and the high costs asso- 2.2 Review and compilation of coral data ciated with deep sampling. In comparison, the combination of historical records with data from fisheries’ by-catch and Historical and new coral records included specimens of from occasional surveys can provide a more insightful pic- the anthozoan orders Alcyonacea, Antipatharia and Scler- ture of the diversity and distribution of corals in this region. actinia, and of the hydrozoan family Stylasteridae, which The main goal of this study is to assess the diversity, dis- are the most commonly recorded taxonomic groups in the tribution and biogeographical patterns of corals belonging Azores showing habitat-forming