Arctic Pre-proposal 3.4-Galloway 1 Research Plan 2 3 A. Project Title: Characterizing lipid production hotspots, phenology, and trophic transfer at the 4 algae-herbivore interface in the Chukchi Sea 5 6 B. Category: 3. Oceanography and lower trophic level productivity: Influence of sea ice dynamics and 7 advection on the phenology, magnitude and location of primary and secondary production, match- 8 mismatch, benthic-pelagic coupling, and the influence of winter conditions. 9 10 C. Rationale and justification: 11 The spatial extent of arctic sea ice is declining and earlier seasonal sea ice melt may dramatically 12 affect the magnitude, and spatial and temporal scale of primary production (Kahru et al. 2011, Wassmann 13 2011). In order to predict the consequences of these changes to ecosystems, it is important that we 14 understand the mechanistic links between temporally dynamic ice conditions and the physical factors 15 which govern phytoplankton growth (Popova et al. 2010). The mechanisms that govern productivity of 16 the Chukchi Sea ecosystem are of considerable interest due to dramatically changing temporal and spatial 17 patterns of sea ice coverage and because this area is likely to be the subject of intense fossil fuel 18 exploration in coming decades (Dunton et al. 2014). Tracing the biochemical pathways of basal resources 19 (pelagic and attached micro- and macroalgae) in this system is critical if we are to better understand how 20 the Chukchi Sea ecosystem might be modified in the future by a changing climate and offshore oil and 21 gas exploration and production (McTigue and Dunton 2014). 22 It is increasingly recognized that lipids and especially essential fatty acids (EFAs) are the drivers 23 of ecosystem production in marine systems (Arts et al. 2001, Litzow et al. 2006). The fatty acid 24 composition of many marine fish is well known (Budge et al. 2002) because of their nutritional 25 importance to humans, and the importance of EFAs for the nutritional physiology of fish is well resolved 26 due to the importance of these molecules for aquaculture systems (Sargent et al. 1999, Copeman et al. 27 2002, Bell and Tocher 2009, Carboni et al. 2012, Murray et al. 2015). However, lipid production by basal 28 resources (benthic and pelagic micro- and macroalgae) and lipid trophic transfer and bioaccumulation in 29 primary consumers such as bivalves and zooplankton is poorly characterized for most regions of the 30 world's oceans. 31 This is particularly true for the Chukchi Sea, where very little previous research has been 32 published on the lipid dynamics of this system (see however, Budge et al. 2007, 2008). Recent research in 33 the Artic has advanced the use of fatty acid compound-specific stable carbon isotope analyses (CSIA) for 34 separating sea ice-originated particulate organic matter (i-POM) from pelagic-originated sources (Wang 35 et al. 2014), and highly branched isoprenoid alkenes such as the lipid IP25 as a trophic biomarker for 36 inference of sea-ice contributions to heterotrophs (e.g., Brown and Belt 2012, Brown et al. 2014). 37 Research using different biomarker approaches to analyze the importance of i-POM to supporting 38 heterotrophs in the Arctic has just begun, and it appears that there is often contradictory evidence for the 39 role of ice algae in supporting heterotrophs. For example, using CSIA, Graham et al. (2014) found little 40 evidence that i-POM supports juvenile polar cod in the Beaufort Sea (Graham et al. 2014). Conversely, 41 Brown and Belt (2012) found ‘convincing’ evidence that i-POM was a significant contributor to benthic 42 invertebrate macrofauna. In order to understand the consequences of changing arctic ice dynamics and 43 associated primary production to food webs, more research, particularly aimed at characterizing multiple 44 lipid and isotope biomarkers in producers and diverse basal heterotrophs, is necessary. 45 Our proposed project will characterize the timing and composition fatty acid (FA) production by 46 functionally distinct arctic basal producer assemblages in the Chukchi Sea, including under-ice, benthic, 47 and pelagic algae. We will investigate the effects of reprocessing of algal lipids by microbial 48 communities, as well as a large spatial analysis of general lipids and essential FA ‘hotspots’ in the benthic 49 and pelagic Chukchi sea invertebrate fauna. This would be an important step towards mapping out the 50 trophic flow of fats through the entirety of this ecosystem, providing critical baseline information on the Arctic Pre-proposal 3.4-Galloway 51 sources and variation of these critical limiting molecules in arctic food webs during a time of dramatic 52 changes in the environment that produces these essential molecules. 53 54 D. Hypotheses: This proposal has three central organizing hypotheses around which the research 55 program is structured, emphasizing fundamental novel research on lipids in 1) lipids of different 56 primary producer assemblages, 2) spatial hotspots of essential lipids in benthic invertebrate 57 consumers, and 3) the changing nutritional value of basal resources as they age and bio-accumulate in 58 the benthos: 59 1. Total lipids and essential long chain polyunsaturated fatty acids (PUFA) will differ among bulk 60 algal communities in ice connected, benthic, and pelagic habitats. Previous research has 61 suggested that ice-algae are more PUFA rich than pelagic phytoplankton but it is unknown 62 whether this is due to differing algal taxonomic composition in these habitats (Galloway and 63 Winder 2015) or because of different environmental conditions. Moreover, recent work by 64 Dunton et al. (unpub. data) indicates that i-POM in benthic algal deposits, even in >40 m depth, 65 are still viable and photosynthesizing. The food value generally, and lipids in particular, of these 66 algal accumulations have not been studied. A comparative analysis of both producer community 67 composition and lipids in these habitats is needed. 68 2. The Chukchi Sea benthic invertebrate communities will be heterogeneous in their lipid 69 composition or content; we will identify essential fatty acid spatial hotspots where benthic 70 invertebrate food quality for predators is the highest. Recent research has shown that invertebrate 71 consumers from different areas of Hanna Shoal (Fig. 1) differ with respect to their density and 72 caloric content among geographic regions (Young 2015). We will used a comparative biomarker 73 approach (e.g., Galloway et al. 2013) to follow up on this work and ask whether benthic caloric 74 spatial density (Fig. 2a) in the Hanna Shoal is predictive of the essential fatty acid content of 75 benthic consumers. Benthic hotspots of caloric content or key fatty acids may be predictive of 76 predator abundance or foraging effort (Fig. 2b). 77 3. Nutritional value (e.g., fatty acid composition and caloric, lipid and sterol contents) of surface ice 78 algae will change as it is experimentally aged and inoculated with seafloor microbes. Recent 79 research on nearshore marine macroalgal producers has shown that as algal detritus ages and is 80 colonized by microbes, the biochemical components and it’s food value to consumers, changes 81 (Galloway et al. 2013, Sosik and Simenstad 2013, Dethier et al. 2014). This aging process may 82 lead to a net loss in food value if essential nutrients are preferentially metabolized by microbes 83 and protozoans, or it may result in a net increase in food value as a result of ‘trophic upgrading’ 84 and concentrating key essential nutrients (Klein Breteler et al. 1999). These processes are 85 potentially critical in arctic food webs but the potential consequences and expected direction of 86 changes to ice algae food quality in particular are currently unknown. 87 88 E. Objectives: These objectives are numbered according to the corresponding hypothesis being 89 evaluated (see above). 90 1. We will collect algal samples in at a broad spatial scale in the two field work years (2017, 2018) 91 corresponding roughly to the spatial area of the Hanna Shoal (Fig. 1) in four differing habitats: ice- 92 attached, under-ice pelagic, ice-free pelagic, and benthic. We will analyze community and biochemical 93 composition of all algal samples following standard protocols (e.g., Lowe et al. 2014) for a comparative 94 analysis of the ‘food value’ of these communities to primary invertebrate consumers. The outcome of 95 this objective will be the first systematic comparison and database of diverse biomarkers (e.g., >25 96 fatty acids and 3 stable isotope signatures) of primary producer assemblages from these four 97 habitats. This novel information will be critical for future efforts to model the implications to arctic food 98 webs of changing ice duration, extent, and persistence. For example, while it is understood that ice extent 99 and duration in the arctic is changing, and that these changes will affect the primary production that drives 100 upper trophic levels (Arrigo et al. 2008), no existing research that we are aware of has identified the 101 consequences of these changes for the relative food quality of resulting algal communities. This is Arctic Pre-proposal 3.4-Galloway 102 important because different types of primary producers vary greatly in their food quality for consumers 103 (Brett and Müller-Navarra 1997, Brett et al. 2009b, 2009a, Galloway and Winder 2015). 104 2. To investigate the spatial heterogeneity of invertebrate consumer fatty acid content, we will 105 collect samples using surface deployed benthic grabs at the same spatial scale as the previous Hanna 106 Shoal Ecosystem Study (http://arcticstudies.org/hannashoal/) funded by the Bureau of Ocean Energy 107 Management (Hanna Shoal Lead Scientist Ken Dunton is a co-PI on the proposed study). New sampling 108 would occur during fieldwork in the years 2017, 2018. Whenever possible, samples will be collected at 109 previously visited stations for optimal comparison with previous Hanna Shoal benthic monitoring efforts 110 (Fig.