The summer distribution, habitat associations and abundance of seabirds in the sub-polar frontal zone of the Northwest Atlantic
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Biological production in the oceanic zone (i.e. waters beyond the continental shelves) is typically spatially patchy and strongly seasonal. In response, seabirds have adapted to move rapidly within and between ocean basins, making them important pelagic consumers. Studies in the Pacific, Southern and Indian Oceans have shown that seabirds are relatively abundant in major frontal systems, with species composition varying by water mass. In contrast, surprisingly little was known about seabird distribution in the oceanic North Atlantic until recent tracking showed that relative abundance and diversity peak in the Sub-polar Frontal Zone, west of the Mid-Atlantic Ridge, now proposed as a Marine Protected Area. However, absolute seabird abundance, distribution, age and species composition, and their potential environmental drivers in the oceanic temperate NW Atlantic remain largely unknown. Consequently, we systematically surveyed seabirds and environmental conditions across this area by ship in June, 2017, then modelled the density of common species as functions of environmental covariates, validating model predictions against independent tracking data. Medium-sized petrels (99.8%), especially Great Shearwaters (Ardenna gravis, 63%), accounted for the majority of total avian biomass, which correlated at the macroscale with net primary production and peaked at the sub-polar front. At the mesoscale, the density of each species was associated with sea surface temperature, indicating zonation by water mass. Most species also exhibited scale-dependent associations with eddies and fronts. Approximately 51, 26, 23, 7 and 1 % of the currently estimated Atlantic populations of Cory's Shearwaters (Calonectris borealis), Great Shearwaters, Sooty Shearwaters (A. grisea), Northern Fulmars (Fulmarus glacialis) and Leach’s Storm-petrels (Oceanodroma leucorhoa) occurred in the area during our survey, many of which were undergoing moult (a vital maintena nce activity). For some species, these estimates are higher than suggested by tracking, probably due to the presence of immatures and birds from untracked populations. Our results support the conclusion that MPA status is warranted and provide a baseline against which future changes can be assessed. Moreover, they indicate potential drivers of seabird abundance and diversity in the oceanic zone of the North Atlantic that should be investigated further.
Wakefield , E D , Miller , D L , Bond , S L , le Bouard , F , Carvalho , P C , Catry , P , Dilley , B J , Fifield , D A , Gjerdrum , C , González-Solís , J , Hogan , H , Laptikhovsky , V , Merkel , B , A. O. Miller , J , Miller , P I , Pinder , S J , Pipa , T , Ryan , P M , Thompson , L A , Thompson , P M & Matthiopoulos , J 2021 , ' The summer distribution, habitat associations and abundance of seabirds in the sub-polar frontal zone of the Northwest Atlantic ' , Progress in Oceanography , vol. 198 , 102657 . https://doi.org/10.1016/j.pocean.2021.102657
Progress in Oceanography
Copyright © 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
DescriptionFunding was provided by the UK Natural Environmental Research Council (NERC) [grant number NE/M017990/1] and Fundação para a Ciência e a Tecnologia (FCT) [grant numbers MARE - UIDB/04292/2020 and UIDP/04292/2020]. Remotely-sensed data were supplied by the NERC Earth Observation Data Acquisition and Analysis Service (NEODAAS) and the Copernicus Marine Service. Support for NOFU loggers and analysis was provided through the SEATRACK project http://www.seapop.no/en/seatrack/, funded by the Norwegian Ministries of Climate and Environment, and Foreign Affairs and the Norwegian Oil and Gas Association.
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