Contents lists available at ScienceDirect Marine Environmental Research journal homepage: www.elsevier.com/locate/marenvrev Seasonal ecology in ice-covered Arctic seas - Considerations for spill response decision making Magnus Aune a,* , Ana Sofia Aniceto a,b , Martin Biuw c , Malin Daase d , Stig Falk-Petersen a,d , Eva Leu e , Camilla A.M. Ottesen d , Kjetil Sagerup a , Lionel Camus a a Akvaplan-niva AS, The Fram Centre, Hjalmar Johansens Gate 14, 9007, Tromsø, Norway b ARCEx (Research Centre of Arctic Petroleum Exploration), UiT The Arctic University of Tromsø, Department of Geology, Dramsveien 201, Postboks 6050 Langnes, N- 9037, Tromsø, Norway c Institute of Marine Research, 9294, Tromsø, Norway d Department of Arctic and Marine Biology, University of Tromsø – The Arctic University of Norway, 9037, Tromsø, Norway e Akvaplan-niva AS, Gaustadalléen 21, 0349, Oslo, Norway ARTICLE INFO Keywords: Arctic ecosystem NEBA Oil spill response Seasonal dynamics ABSTRACT Due to retreating sea ice and predictions of undiscovered oil and gas resources, increased activity in Arctic shelf sea areas associated with shipping and oil and gas exploration is expected. Such activities may accidentally lead to oil spills in partly ice-covered ocean areas, which raises issues related to oil spill response. Net Environmental Benefit Analysis (NEBA) is the process that the response community uses to identify which combination of response strategies minimises the impact to environment and people. The vulnerability of Valued Ecosystem Components (VEC's) to oil pollution depends on their sensitivity to oil and the likelihood that they will be exposed to oil. As such, NEBA requires a good ecological knowledge base on biodiversity, species' distributions in time and space, and timing of ecological events. Biological resources found at interfaces (e.g., air/water, ice/ water or water/coastline) are in general vulnerable because that is where oil can accumulate. Here, we sum- marize recent information about the seasonal, physical and ecological processes in Arctic waters and evaluate the importance these processes when considering in oil spill response decision making through NEBA. In spring- time, many boreal species conduct a lateral migration northwards in response to sea ice retraction and increased production associated with the spring bloom. However, many Arctic species, including fish, seabirds and marine mammals, are present in upper water layers in the Arctic throughout the year, and recent research has de- monstrated that bioactivity during the Arctic winter is higher than previously assumed. Information on the seasonal presence/absence of less resilient VEC's such as marine mammals and sea birds in combination with the presence/absence of sea ice seems to be especially crucial to consider in a NEBA. In addition, quantification of the potential impact of different, realistic spill sizes on the energy cascade following the spring bloom at the ice- edge would provide important information for assessing ecosystem effects. 1. Introduction According to predictions, up to 30% of the worlds' undiscovered gas reserves and 13% of the worlds' undiscovered oil resources are located in the areas north of the Arctic Circle, mainly offshore in relatively shallow waters (Gautier et al., 2009). However, major parts of these areas are covered by sea ice, either permanently or seasonally (Fetterer et al., 2002). Activities associated with oil exploration and production will always be associated with a certain risk of oil spills. Oil spills may happen during drilling, production (extraction), transportation in pi- pelines or by ships, and from other vessels associated with oil activities (e.g., supply vessels). The presence of ships in the Arctic is expected to rise, not only as a consequence of increased oil exploration, but also because the decreasing ice coverage in the Arctic facilitates increased shipping in these areas (Glickson et al., 2014). An accidental oil spill in the Arctic may result in oil contamination of ice-covered areas, thereby affecting Valued Ecosystem Components (VEC's). In the case of an ac- cidental spill, the response community should have tools available to support Arctic spill response decision making, in order to minimize the impact on VEC's. Net Environmental Benefit Analysis (NEBA) is a process that is used by the response community to select the response strategy that https://doi.org/10.1016/j.marenvres.2018.09.004 Received 14 November 2017; Received in revised form 9 March 2018; Accepted 3 September 2018 * Corresponding author. E-mail address: magnus.aune@akvaplan.niva.no (M. Aune). Marine Environmental Research xxx (xxxx) xxx–xxx 0141-1136/ © 2018 Elsevier Ltd. All rights reserved. Please cite this article as: Aune, M., Marine Environmental Research, https://doi.org/10.1016/j.marenvres.2018.09.004