1. The loss of marine foundation species, in particular kelps at temperate latitudes, has been linked to climatic drivers and co-occurring human perturbations. Ocean temperature and nutrients typically covary over local and regional scales and play a crucial role on kelp dynamics. Examining their independent and interactive effects on kelp physiological performance is essential to understand and predict patterns of kelp distribution, particularly under scenarios of global change. 2. Crossed combinations of ocean temperatures and availability of nutrients were experimentally tested on juveniles of the 'golden kelp', Laminaria ochroleuca, from the northwestern Iberian Peninsula. Eco-physiological responses included: survival, growth and total N content. Results were embedded into a Species Distribution Model (SDM), which relates presence records and climatic and non-climatic data to forecast distribution patterns of L. ochroleuca under different climate change scenarios. 3. Temperatures above 24.6°C were lethal irrespective of nutrients. Optimal growth of juvenile sporophytes occurred between 12 and 18°C and no nutrient limitation.The SDM, where ocean temperature was the main predictor of kelp distribution in line with temperature thresholds given by eco-physiological responses, suggests a future expansion towards northern latitudes and a retreat from the southern limit/ boundary of the current distribution. Synthesis.Range-shifting of the golden kelp can have severe ecological impacts at regional and local scales. The expansion or retraction of the species along the European coast seems to be modulated mainly by temperature, but nutrient availability would be a key to maintain optimal physiological performance. Our work highlights that the combination of empirical and modelling approaches is accessible to researchers and crucial to building more robust predictions of ecological and biogeographic responses of habitat-forming species to forecasted environmental change.
Aim To describe distribution patterns and species richness of cetaceans along a wide geographical range using occurrence data coupled with survey effort, from poorly studied oceanic areas. Specific objectives were to compare species richness and relative abundances among sub‐regions and to describe the distribution of each species. Location Eastern North Atlantic. Time period 2012–2017. Major taxa studied Cetacea. Methods Cetacean monitoring was performed by dedicated observers from cargo ships, used as platforms of opportunity, along routes between Iberian Peninsula, Macaronesia and north‐western Africa. We mapped relative abundance (encounter rates), survey effort and species richness. We examined the dependence of the number of sightings and species richness on survey effort. The area was divided into sub‐regions (according to the Exclusive Economic Zones and international waters), and relative abundances of the eight most frequently sighted species, as well as species richness, were compared among them. In addition, we describe the distribution of each species in relation to sea depth, distance to coast, latitude and longitude. Results A total of 1,989 sightings were logged, and 26 cetacean species were identified. Species richness and relative abundances of the eight most common species differed substantially between sub‐regions. Common and bottlenose dolphins distributed in shallow coastal waters contrasting with the oceanic distribution of Stenella dolphins. Cuvier's beaked whale and minke whale had similar distributions. Pilot and sperm whales were distributed in southern waters. Main conclusions A considerable amount of survey effort was needed to attain reliable estimates of species richness. In less surveyed areas, species richness and abundance are likely to be underestimated. The offshore waters presented high species richness and several hotspots of cetacean abundance. This work provides new knowledge on cetacean distribution at a large scale in the eastern North Atlantic, relevant to future conservation management.
Data on species occurrence at the scale of their distributional range and the determination of their habitat use requirements are essential to support conservation and define management plans that account for their habitat requirements. For wide-ranging species, such as cetaceans, especially considering that their marine habitats include offshore areas, collection of such data is challenging. In the absence of dedicated surveys, alternative methodologies are needed, such as the use of data collected from platforms of opportunity and modelling techniques to predict distribution in unsurveyed areas. Using 6 years of cetacean occurrence data collected along cargo ship routes between the Iberian Peninsula, northwestern African coasts and the Macaronesian islands, we developed ecological niche models to assess habitat preferences and predict suitable habitats of the eight most frequently sighted cetacean taxa in the area. Explanatory variables used for model fitting included topographic, oceanographic, detectability, geographic and seasonal features. To provide a robust habitat characterisation, along with predictions of habitat suitability, making best use of occurrence datasets, we applied two modelling techniques, GAM and Maxent, which offer complementary strengths. Coastal areas provide important habitats for common and bottlenose dophins, while other dolphin species (spotted and striped dolphins) have a more oceanic distribution. The predicted niches of Cuvier’s beaked whale and minke whales are mainly in the high seas at northern latitudes. Suitable habitats for sperm whales and pilot whales are mostly in southern areas in continental slope regions. For all the species, models indicated that areas around seamount features offer suitable habitats, likely of high relevance in oligotrophic offshore waters. As such, dedicated survey effort in such areas would facilitate development and implementation of appropriate management plans, which are currently lacking. Our models offer an important contribution to baseline knowledge of cetacean distribution at basin-scale in the region and could support the definition of priority areas, monitoring plans, and conservation measures, essential to comply with the requirements of the EU Marine Strategy Framework Directive.
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Macaronesia, an oceanic area located in the Northeast Atlantic, exhibits a high topographic and oceanographic complexity that enables a rich biodiversity. So far, seven species of baleen whales have been recorded in the area. These are migratory animals that travel long distances between feeding grounds at high latitudes in summer and tropical areas for mating and breeding in winter. As baleen whales are such mobile animals, the conservation and management of their habitat is highly challenging. Hence, knowing and understanding the patterns of their distribution is fundamental. Despite the many records of baleen whales in Macaronesia, heterogeneity in research effort has resulted in scattered occurrence data that leads to an incomplete picture of their distribution in the area. We aim to increase knowledge of distribution patterns of baleen whales, and identify research effort gaps in Macaronesia. From a total of 14 peer‐reviewed publications, four public reports, two poster presentations, and four data bases, we gathered 1798 records in Macaronesia since 1990 for four species of baleen whale: minke whale Balaenoptera acutorostrata, fin whale Balaenoptera physalus, blue whale Balaenoptera musculus, and humpback whale Megaptera novaeangliae. Spatio‐temporal descriptive analyses and ecological modelling were carried out in order to understand occurrence patterns. The results show a big lack of research effort and occurrence data in offshore areas and in some coastal waters, namely off the West African coast. Moreover, blue, fin, and humpback whales are sighted mainly in spring in the north of Macaronesia, while minke whale distribution is clearly different: they have a stronger presence in summer. This study highlights areas in urgent need of research effort in order to inform decision‐makers and support effective measures for the protection and conservation of baleen whales in Macaronesia.
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