IMIS

Dataset collating sublittoral kelp occurrences (presences and absences) of Laminaria ochroleuca and Phylariopsis brevipes subsp. brevipes from surveys conducted across the Azores archipelago (NE Atlantic). The surveys targeted 735 points in rocky and mixed seabed areas between 35m and 85 m depth, which generally corresponds to the depth range of these species in the archipelago. They were performed between 2004 and 2018 using: (i) two small remote operated vehicles (a VideoRay Explorer micro-ROV and a SeaBotix LBV300S-6 mini-ROV); (ii) two custom-made drop-down cameras (DDCs) built from Tritech MD4000, GoPro Hero3+ and GitUp Git 2 cameras; and (iii) SCUBA diving using conventional open-circuit systems for dives shallower than 40 m and rebreathers (RB80 Passive Semi-Closed, JJ Closed-Circuit and Sidewinder sidemount rebreathers) for deeper dives. A few specimens by-caught in the course of the ARQDAÇO fisheries surveys organized by IMAR/DOP-University of the Azores were also included in our record list. ROV deployments were essentially point dives conducted while the boat was at anchor and observations could be approximately positioned using a surface GPS. The observations conducted at each station were generally restricted to a 10-meter radius around a drop-weight used to minimize current-induced drifts and dampen swell movements. DDC deployments generally consisted of transects ranging between 5 and 40 minutes or, when current drift was insufficient to provide a fast enough drift over the seabed, multiple point drops done parallel to the depth gradient. SCUBA diving was used both to collect specimens in locations of attested kelp occurrence and, in the case of dives with rebreathers, to collect seafloor video in depths between 42 and 80m. ROV and DDC deployments were conducted mostly during daytime apart from a few exploratory night-time deployments aimed at investigating the occurrence of particular nocturnal fauna. Overall, the imagery compilation used in this study comprises 36 hours 48 min of video footage and 59 still photos of kelp habitat.

Acknowledgements: To the Portuguese Foundation for Science and Technology for grants awarded to Fernando Tempera (refs: SFRH/BD/12885/2003, SFRH/BPD/79801/2011). To EC project MARFOR (BIODIVERSA/004/2015) for David Milla-Figueras contract and fieldwork funding. To the Azores Regional Government for (i) the Estagiar L grant awarded to Ana Luísa Sinde-Mano and (ii) the surveys funded via the BALA and MoniZec-ARP (DRAM) monitoring programmes. To project PLATMAR (FCT PTDC/GEO-GEO/0051/2014) for funding fieldwork in 2018. To the Oceano Azul Foundation and the Waitt Foundation for funding the Blue Azores 2018 expedition. To Pedro Afonso (IMAR-DOP/Uaz) for organising several surveys. To Gonçalo Graça, Diya Das and the crews of the vessels Águas Vivas, Arquipélago and Nossa Senhora dos Milagres for executing several surveys. To Renato Martins (IMAR-DOP/Uaz) for the mini-ROV SP operation and troubleshooting. To Dr. Richard Bates (Univ. St. Andrews) for providing the micro-ROV and the camera used in the 2004 and 2005 surveys. To Todd Kincaid (GUE), Joana Boavida (Ualg) and Pedro Ribeiro (Okeanos-Uaz) for sharing imagery collected during the Azores 2014 leg of project Baseline/Global Underwater Explorers. To Ricardo Serrão Santos and Frederico Cardigos for their general support and organisation of the early BANCOS expeditions promoted by IMAR/DOP-Uaç. To Estibaliz Berecibar and Ester Serrão (Ualg) for taxonomic guidance.