Papers by William G Ambrose
Polar Biology, 2020
This work was partially financed by the Fram Center flagship "Climate Change in Fjord and Coast" ... more This work was partially financed by the Fram Center flagship "Climate Change in Fjord and Coast" though the project "Effects of climate on cod life history and ecology along a temperate-arctic gradient" and Akvaplan-niva AS. MLC was supported in part by "ARCEx-The Research Centre for ARCtic Petroleum Exploration" funded by the Research Council of Norway (Project #228107) together with 10 academic and 8 industry partners. Thanks to Paul Renaud for his support carrying out the ANOSIM tests.
CAGE – Centre for Arctic Gas Hydrate, Environment and Climate Report Series
The main goal of CAGE 15-2 cruise was to study the gas hydrate system and methane emissions off ... more The main goal of CAGE 15-2 cruise was to study the gas hydrate system and methane emissions off western Svalbard and in Storfjordrenna. We addressed this through a comprehensive scientific program comprising dives with the MISO-‐Tow Cam adapted to the multicorer frame from UiT-‐NPI (TowCam/Multicorer, TCM), methane measurements in sediments and water column, sediment coring (multicorer + gravitycorer), water column and sediment biogeochemistry, microbiology, micropaleontology, macrobiology, and bathymetric mapping. In addition, during the ecosounder and TCM surveys we collected data for selecting the locations for the CAGE observatories to be deployed during the cruise. The areas investigated were: W Prins Karls Forland (two sites at ca 90 m and 240 m water depth),An area located at the coordinate 78N 08E called “site 7808” (ca 90 m water depth; marker CAGE 882),Vestnesa Ridge (ca 1200 m water depth; markers CAGE 888 and 895),Storfjordrenna (two sites at ca 350, benthic station ...
Polar Biology, 2018
Many marine species are known to change their distribution in response to changing climatic condi... more Many marine species are known to change their distribution in response to changing climatic conditions. One such example is the blue mussel Mytilus spp., spreading northward coincident with an increase in ocean temperatures. On Svalbard, the first living specimens of Mytilus spp. were discovered in 2004. Here we present an analysis of the current distribution of Mytilus spp. on Svalbard, with a focus on the west coast of Spitsbergen where strong Atlantification has been documented over the last few decades. We conducted diver-based surveys to develop a distributional map and to compare the current distribution with that of the Holocene. Furthermore, we investigate the recent history of recruitment of mussels on Svalbard to help identify invasion pathways. Our results show that blue mussels have been present on the archipelago at least since 2000 and are widespread along the west coast today. We also present evidence of local reproduction in one of the sites explored.
We examined growth of the Arctic bivalve Clinocardium ciliatum from 1977-2006 in the Barents Sea ... more We examined growth of the Arctic bivalve Clinocardium ciliatum from 1977-2006 in the Barents Sea to evaluate the effect of different water masses on growth and to assess the influence of climatic forcing on ecological processes over decadal scales. Analysis of annually-deposited growth lines in shells of 22 individuals from 3 stations allowed us to assess growth conditions for up to 30 years, thus encompassing both warmer and colder climatic phases of the last century. Growth rates of specimens at younger ages (6-13 years) were highest in Atlantic water, resulting in an average size 20% greater compared to similarly aged individuals from Arctic water or at the Polar Front, reflecting warmer sea temperatures and/or presumably greater food supplies in the Atlantic-dominated regions of the Barents Sea. Despite different absolute growth rates, temporal patterns of ontogenetically-adjusted growth (i.e. Standard Growth Index = SGI) had similar features, with below-average but increasing SGI throughout the 1980s and culminating in 1994 or 1995 with the highest SGI. An abrupt decline starting in 1996 led to below-average growth rates for most of the years from the turn of the century to the end of the record in 2006. The decline in growth coincides with abrupt phase shifts in two hemispheric oscillatory indices: the North Atlantic Oscillation (NAO) and the Arctic Climate Regime Index (ACRI). The strongest statistical relationships were found between growth and the ACRI, and its local manifestations through precipitation. The ACRI explained 16.9% and 27.7% of the variation in growth at the Atlantic and Arctic stations respectively while ACRI and annual precipitation together explained 42.1% of the growth at the Polar Front station. Using a two year running mean of the ACRI improved these relationships substantially, indicating a lag in the relationship between index and growth. These results suggest that benthic communities in this area are responding more to regional climate forcing than local parameters and that the predicted increase of Atlantic water in the Climate forcing and bivalve growth in the Barents Sea M.L. Carroll et al. 3 Barents Sea in response to climate change will have an impact on at least suspension feeding benthic organisms.
Cold seeps are locations where hydrocarbons, sulfide or reduced compounds emanate from the seaflo... more Cold seeps are locations where hydrocarbons, sulfide or reduced compounds emanate from the seafloor, which may fuel chemoautotrophic production and form additional hard bottom substrate through carbonate precipitation. Chemosynthetic symbiosis, trophic interactions, and additional bottom substrate types can provide a heterogeneous environment for deep-sea organisms supporting macrofaunal communities including increased biodiversity and biomass. We combined quantitative benthic faunal samples with sea floor photographs from an active, methane seeping pockmark at Vestnesa Ridge (1200 meters depth) to examine community structure and biodiversity in a high Arctic deep cold seep. Quantitative data were compared with samples from the nearby inactive Svyatogor Ridge (1577-1706 meters depth). We measured highly elevated methane concentrations (up to 100x background levels) in the sediment at Vestnesa Ridge. Faunal abundance, species richness and biomass were significantly higher at the Vestnesa pockmark compared to inactive Svyatogor Ridge. Seabed photos from Vestnesa Ridge reveal high megafaunal diversity and biomass and cold seep features including carbonate crust and microbial mats. Our observations indicate that chemoautotrophic production enhances deep-sea biomass and diversity at Vestnesa Ridge. The focused methane emissions create a heterogeneous deep-sea habitat for chemo-associated organisms coexisting with heterotrophic conventional fauna in a high Arctic seep.
Limnology and Oceanography, 2017
Cold seeps can support unique faunal communities via chemosynthetic interactions fueled by seabed... more Cold seeps can support unique faunal communities via chemosynthetic interactions fueled by seabed emissions of hydrocarbons. Additionally, cold seeps can enhance habitat complexity at the deep seafloor through the accretion of methane derived authigenic carbonates (MDAC). We examined infaunal and megafaunal community structure at high-Arctic cold seeps through analyses of benthic samples and seafloor photographs from pockmarks exhibiting highly elevated methane concentrations in sediments and the water column at Vestnesa Ridge (VR), Svalbard (798 N). Infaunal biomass and abundance were five times higher, species richness was 2.5 times higher and diversity was 1.5 times higher at methane-rich Vestnesa compared to a nearby control region. Seabed photos reveal different faunal associations inside, at the edge, and outside Vestnesa pockmarks. Brittle stars were the most common megafauna occurring on the soft bottom plains outside pockmarks. Microbial mats, chemosymbiotic siboglinid worms, and carbonate outcrops were prominent features inside the pockmarks, and high trophic-level predators aggregated around these features. Our faunal data, visual observations, and measurements of sediment characteristics indicate that methane is a key environmental driver of the biological system at VR. We suggest that chemoautotrophic production enhances infaunal diversity, abundance, and biomass at the seep while MDAC create a heterogeneous deep-sea habitat leading to aggregation of heterotrophic, conventional megafauna. Through this combination of rich infaunal and megafaunal associations, the cold seeps of VR are benthic oases compared to the surrounding high-Arctic deep sea. Highlights Seafloor methane emissions support a rich and diverse infaunal community distinct from a nearby non-seepage region Megafaunal composition varies significantly along a spatial gradient from inside pockmarks with strong methane emissions toward conventional habitats outside pockmarks Methane emissions provide both heterogeneous seabed substrates and enhanced chemosynthetic-based organic matter production
Limnology and Oceanography, 2016
The recent discovery of methane seeps in the Arctic region requires a better understanding of the... more The recent discovery of methane seeps in the Arctic region requires a better understanding of the fate of methane in marine sediments if we are to understand the contributions of methane to Arctic ecosystems and climate change. To further this goal, we analyze pore water data from five pockmarks along eastern Vestnesa Ridge, a sediment drift northwest of Svalbard, to quantify the consumption of dissolved methane in the sediments 3-5 meters below seafloor. We use transportreaction models to quantify the hydrology as well as the carbon mass balance in the sediments. Pore water profiles and our model results demonstrate that hydrological, microbial, and geochemical processes/reactions efficiently remove methane carbon from fluid over different time scales. We interpret the non-steady-state behavior of the first 50-70 cm of our pore water profiles from the active sites as an annual scale downward fluid flow due to a seepage-related pressure imbalance. Such downward flow dilutes the concentration of methane within this depth range. Our steady-state modeling confirms the efficiency of anaerobic oxidation of methane (AOM) in consuming dissolved methane in the upper 0.8 to 1.2 meter of sediments. Based on the phosphate profiles, we estimate that AOM at the active pockmarks may have been operating for the last two to four centuries. Precipitation of authigenic carbonate removes a significant fraction of methane carbon from fluid. More than a quarter of the dissolved inorganic carbon produced by l y AOM is fixed as authigenic carbonate in the sediments, a process that sequestrates methane carbon over geological time.
Journal of Marine Science and Engineering
The settlement of spores and larvae on hard substrates has been shown to be influenced by many fa... more The settlement of spores and larvae on hard substrates has been shown to be influenced by many factors, but few studies have evaluated how underlying bedrock may influence recruitment. The characteristics of coastal rock types such as color, heat capacity, mineral size, and free energy have all been implicated in settlement success. We examined the influence of naturally occurring rock types on the initial attachment of zygotes of the brown alga Fucus spiralis Linnaeus 1753. We also assessed the dislodgment of zygotes on four bedrock types after initial attachment in laboratory experiments using wave tanks. Settling plates were prepared from limestone, basalt, schist, and granite, found in the region of Orrs Island, Maine, USA. The plate surfaces tested were either naturally rough or smooth-cut surfaces. We measured the density of attached zygotes after 1.5 h of settlement and subsequently after a wave treatment, in both winter and summer. The pattern of initial attachment was the s...
Palaeogeography, Palaeoclimatology, Palaeoecology, 2017
Understanding rapid climate change in the Arctic and its ecosystem implications requires more inf... more Understanding rapid climate change in the Arctic and its ecosystem implications requires more information on the environment at temporal resolutions and time-periods not available from instrumental records. Such information can be acquired through geochemical proxy records, but sub-annual records are rare. We analyzed shell material of bivalve mollusks (Serripes groenlandicus and Ciliatocardium ciliatum) placed on oceanographic moorings for one year in two Arctic fjords to assess the potential use of shell elemental ratios as environmental proxies.
Environmental Pollution, 2012
Organochlorine compounds (OC) were determined in Arctic bivalves (Mya truncata, Serripes groenlan... more Organochlorine compounds (OC) were determined in Arctic bivalves (Mya truncata, Serripes groenlandicus, Hiatella arctica and Chlamys islandica) from Svalbard with regard to differences in geographic location, species and variations related to their size and age. Higher chlorinated polychlorinated biphenyls (PCB 101ePCB 194), chlordanes and a-hexachlorocyclohexane (a-HCH) were consistently detected in the bivalves and PCBs dominated the OC load in the organisms. OC concentrations were highest in Mya truncata and the lowest in Serripes groenlandicus. Species-specific OC levels were likely related to differences in the species' food source, as indicated by the d 13 C results, rather than size and age. Higher OC concentrations were observed in bivalves from Kongsfjorden compared to the northern sampling locations Liefdefjorden and Sjuøyane. The spatial differences might be related to different water masses influencing Kongsfjorden (Atlantic) and the northern locations (Arctic), with differing phytoplankton bloom situations.
Marine Ecology Progress Series, 2019
Cold seeps are locations where seafloor communities are influenced by the seepage of methane and ... more Cold seeps are locations where seafloor communities are influenced by the seepage of methane and other reduced compounds from the seabed. We examined macro-infaunal benthos through community analysis and trophic structure using stable isotope analysis at 3 seep locations in the Barents Sea. These seeps were characterized by high densities of the chemosymbiotic polychaetes Siboglinidae, clade Frenulata (up to 32 120 ind. m −2), and thyasirid bivalves, Mendicula cf. pygmaea (up to 4770 ind. m −2). We detected low δ 13 C signatures in chemosymbiotic polychaetes and in 3 species of omnivorous/predatory polychaetes. These δ 13 C signatures indicate the input of chemosynthesis-based carbon (CBC) into the food web. Applying a 2-source mixing model, we demonstrated that 28−41% of the nutrition of non-chemosymbiotic polychaetes originates from CBC. We also documented large community variations and small-scale variability within and among the investigated seeps, showing that the impact of seepage on faunal community structure transcends geographic boundaries within the Barents Sea. Moreover, aggregations of heterotrophic macro-and megafauna associated with characteristic seep features (microbial mats, carbonate outcrops, and chemosymbiotic worm-tufts) add 3-dimensional structure and habitat complexity to the seafloor. Cold seeps contribute to the hydrocarbon-derived chemoautotrophy component of these ecosystems and to habitat complexity. These characteristics make the cold seeps of potential high ecological relevance in the functioning of the larger Arctic−Barents Sea ecosystem.
Marine Ecology Progress Series, 2016
Cold seeps are locations where hydrocarbons emanate from the seabed, fueling chemoautotrophic pro... more Cold seeps are locations where hydrocarbons emanate from the seabed, fueling chemoautotrophic production that may support macrofaunal communities via chemosymbiosis or trophic interactions. The recent discovery of offshore sub-seabed gas reservoirs and venting methane at the seabed in Svalbard (75 to 79°N) provides the context to examine the influence of cold seeps on macrofaunal community structure in the high-Arctic. We compared benthic macrofaunal community structure from cold-seep environments and paired control stations from 3 regionally distinct areas along the western Svalbard margin and the western Barents Sea. Specialized seep-related polychaetes (e.g. siboglinid tubeworms) were found at seep stations in the Barents Sea in high densities (up to 7272 ind. m −2). The presence of obligate seep-associated faunal taxa demonstrates that chemoautotrophic production, fueled by methane and sulfur, influences benthic communities at these seeps. Further, total biomass was significantly higher at seep-impacted stations compared to controls (mean = 20.7 vs. 9.8 g wet weight sample −1), regardless of region. Four methane seep-influenced samples showed clear indications of seep impact, with reduced diversity and with a few species dominating, compared to controls. Our results demonstrate that the effect of methane seeps on the Svalbard shelf benthic community are highly localized (i.e. meter scale), reflecting strong gradients associated with the point-source impacts of individual seeps. Regional differences and the restricted spatial extent of focused emissions likely drive the observed complexity and heterogeneity at Svalbard cold seeps. These results provide key base-American plaice Hippoglossoides platessoides in a dense field of chemosymbiotic polychaetes at a Svalbard cold seep. Photo: CAGE OPEN PEN ACCESS CCESS line observations in a high-Arctic location that is likely to be influenced by warming sea temperatures, which may lead to increased seabed methane release.
Polar Biology, 2009
Macrobenthos of the shallow (\10 m) nearshore marine waters of northern Kotzebue Sound was examin... more Macrobenthos of the shallow (\10 m) nearshore marine waters of northern Kotzebue Sound was examined in 2002-2004 to (1) determine nearshore community structure and (2) assess the influence of sewage disposal. A variable number of benthic stations were sampled during three summers, with extensive effort at the disposal zone in 2003. The benthic community structure is similar to other nearshore Arctic locations, and was similar to a previous benthic study done in 1986-1987. The potential of sewage impact was assessed at the request of the community, because sewage is occasionally discharged into the Sound, in volumes of up to 38 million liters, typically through the ice in early spring. Only minimal effects of disposal on the benthos were evident and the effects could not be separated from the impacts of low salinity and relatively high water pigments. Low diversity (H 0) and species richness (d) and high biomass characterized stations in the sewage area. Parameters often associated with extreme sewage pollution, particularly hypoxic and/or anoxic conditions and high abundance of opportunistic taxa, were not observed. Local traditional ecological knowledge was solicited throughout the study, and was used to help define the area potentially affected by sewage disposal.
Marine Ecology Progress Series, 2006
Food web structure and pathways from primary production were studied in pelagic, sympagic (ice-as... more Food web structure and pathways from primary production were studied in pelagic, sympagic (ice-associated) and benthic communities during summer in a seasonally ice covered region of the northern Barents Sea. Stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) were used as tracers of organic material through marine food webs and trophic levels of organisms, respectively. Measurements of δ 15 N show that sympagic amphipods occupy the lowest trophic levels (ca. 2), for primary consumers, followed by zooplankton (2.0 to 2.6), benthic suspension and deposit feeders (2.2 to 3.7), benthic carnivores (3.6 to 4.4) and fishes (3.3 to 4.4). The δ 13 C values indicate that zooplankton mainly graze on suspended particulate organic material (POM). Sympagic amphipods derive most of their energy from ice POM, but some species had δ 13 C values indicating that phytoplankton also contributes to their energy intake. δ 13 C values of some components of the benthic community suggest that POM settling out of the water column is efficiently exploited by the benthic fauna. Elevated δ 13 C values of the benthic fauna relative to zooplankton at some stations indicate that the degree of pelagic-benthic coupling at stations separated by only 90 km is determined by a combination of factors, including water-mass properties and the primary-production regime. These results may qualify findings of previous studies that have sampled from discrete locations or have pooled specimens collected from a broad area to make conclusions about food webs on a regional scale. KEY WORDS: Stable isotopes • δ 13 C • δ 15 N • Food web • Arctic • Barents Sea • Marginal Ice Zone • Pelagic-benthic coupling Resale or republication not permitted without written consent of the publisher
Marine Ecology Progress Series, 1995
We used stable carbon (l3C/I2C) and nitrogen (f S~/ ' ") isotope analysis to investigate linkages... more We used stable carbon (l3C/I2C) and nitrogen (f S~/ ' ") isotope analysis to investigate linkages between sources of primary production and the pelagic and benthic components of the Northeast Water (NEW) Polynya off northeastern Greenland. Ice algae was enriched in 13C (mean 6I3C =-18.6 vs-27.9%) and I5N [mean 6 1 5~ = 8.3 vs 4.9%0) over particulate organic matter [POM) suggesting that the relative importance of these sources might be traced isotopically. Most grazing crustaceans and filter-feeding bivalves had 6I3C and 6 1 5~ values in the range of-21 to-23% and 7 to 9x0, respectively, indicating a direct pathway from POM. Close benthic-pelagic coupling was also confirmed for other benthic organisms examined with the exception of the predatory or deposit feeding echinoderms Ophioctin, Ophiacantha and Pontaster. Compared with other Arctic and temperate marine food webs, stable-carbon isotope values for the NEW Polynya were depleted in I3C. A S1'N trophic model that incorporated taxon-specific isotopic fractionation factors indicated that the NEW Polynya consisted of 4.5 to 5 trophic levels. Stable-isotope analysis Inay be well suited to establ~shing the importance of polynyas as sites of high primary productivity and tight benthic-pelagic coupling relative to regions of more permanent ice cover.
Marine Biodiversity, 2010
Although knowledge of Arctic seas has increased tremendously in the past decade, benthic diversit... more Although knowledge of Arctic seas has increased tremendously in the past decade, benthic diversity was investigated at regional scales only, and no attempt had been made to examine it across the entire Arctic. We present a first pan-Arctic account of the species diversity of the macro-and megabenthic fauna of the Arctic marginal shelf seas. It is based on an analysis of 25 published and unpublished species-level data sets, together encompassing 14 of the 19 marine Arctic shelf ecoregions and comprising a total of 2636 species, including 847 Arthropoda, 668 Annelida, 392 Mollusca, 228 Echinodermata, and 501 species of other phyla. For the four major phyla, we also analyze the differences in faunal composition and diversity among the ecoregions. Furthermore, we compute gross estimates of the expected species numbers of these phyla on a regional scale. Extrapolated to the entire fauna and study area, we arrive at the conservative estimate that 3900 to 4700 macro-and megabenthic species can be expected to occur on the Arctic shelves. These numbers are smaller than analogous estimates for the Antarctic shelf but the difference is on the order of about two and thus less pronounced than previously assumed. On a global scale, the Arctic shelves are characterized by intermediate macro-and megabenthic species numbers. Our preliminary pan-Arctic inventory provides an urgently needed assessment of current diversity patterns that can be used by future investigations for evaluating the effects of climate change and anthropogenic activities in the Arctic.
Marine Biodiversity, 2011
A benthic species inventory of 1,125 taxa was compiled from various sources for the central Arcti... more A benthic species inventory of 1,125 taxa was compiled from various sources for the central Arctic deeper than 500 m, and bounded to the Atlantic by Fram Strait. The inventory was dominated by arthropods (366 taxa), foraminiferans (197), annelids (194), and nematodes (140). An additional 115 taxa were added from the Greenland-Iceland-Norwegian Seas (GIN). Approximately half of all taxa were recorded from only 1 or 2 locations. A large overlap in taxa with Arctic shelf species supports previous findings that part of the deepsea fauna originates from shelf species. Macrofaunal abundance, meiofaunal abundance and macrofaunal biomass decreased significantly with water depth. Robust diversity indices could only be calculated for the polychaetes, for which S, ES(20), H' and Delta+ decreased significantly with water depth, and all but ES (20) decreased slightly with latitude. Species evenness increased with depth and latitude. No mid-depth peak in species richness was observed. Multivariate analysis of the Eurasian, Amerasian and GIN Seas polychaete occurrences revealed a strong Atlantic influence, the absence of modern Pacific fauna, and the lack of a barrier effect by mid-Arctic ridges. Regional differences appear to be moderate on the species level and minor on the family level, although the analysis was confounded by a lack of methodological standardization and inconsistent taxonomic resolution. Future efforts should use more consistent methods to observe temporal trends and This article belongs to the special issue "Arctic Ocean Diversity Synthesis" Electronic supplementary material The online version of this article
Journal of Marine Research, 2007
Reduction of sea ice in the Arctic may significantly alter the relative fluxes of phytoplankton a... more Reduction of sea ice in the Arctic may significantly alter the relative fluxes of phytoplankton and ice algae to the seafloor. To examine the response of Arctic benthic communities to changing food supplies, we incubated sediment cores collected from two sites (Smeerenburg Fjord, northwest Svalbard in May 2003 and Storfjord Trench, Barents Sea in May 2004) with controlled additions of natural phytoplankton and ice algal assemblages, and laboratory-cultured 13 C-labeled ice algae (Nitzschia frigida, in 2004 only). We measured sediment respiration, pigments, lipid biomarkers, and compound-specific ␦ 13 C signals over the course of incubations. Both communities responded rapidly to the addition of food materials: regardless of food type, concentrations of organic biomarkers (pigments and fatty acids) decreased to the levels of control cores within seven days. Although we found no evidence for selective ingestion of the different food types by macrofauna, fatty acids were differentially consumed. The enriched polyunsaturated fatty acids of the ice algae were preferentially utilized compared to saturated and monounsaturated fatty acids bound in ice algae. However, the saturated and monounsaturated fatty acids of phytoplankton (with depleted polyunsaturated fatty acids) are utilized more efficiently than those counterparts bound in ice algae. Bacterial activity was stimulated by food addition, indicated by the immediate increase of bacteria-specific fatty acids, but the direct assimilation of 13 C-labeled carbon into bacterial biomass was limited. Our results imply that Arctic benthic communities can meet their energetic requirements by altering strategies to assimilate different components from variable food supplies.
Journal of Experimental Marine Biology and Ecology, 2009
Recent reductions in sea ice cover and thickness in the Arctic will lead to changes in food suppl... more Recent reductions in sea ice cover and thickness in the Arctic will lead to changes in food supplies for benthic consumers. We experimentally assessed responses of two common Arctic macrobenthic species, Macoma balthica (Bivalvia) and Monoporeia affinis (Crustacea) from Kotzebue Sound (Alaska, USA) to varying food materials (phytoplankton and ice algae). Phytoplankton and 13 C-labelled ice algae were added separately or together to presieved sediment cores containing known numbers of Macoma or Monoporeia. After 8 d, sediments and animals were analyzed for bulk C/N contents, isotopic signatures, fatty acid compositions and compound-specific δ 13 C values. Our results showed that the two species responded differently to varying food materials. Loss of characteristic fatty acids and changes in δ 13 C values in the surrounding sediments indicate that Macoma preferentially consumed ice algae compared to phytoplankton, while Monoporeia non-selectively ingested both food materials. Feeding behaviors also differed between the two species: Macoma fed primarily on material from the sediment surface, and did not appear to mix material to depth, while Monoporeia mixed some fresh food material from the surface down to subsurface sediments (1-2 cm). Analysis of animal biomass showed more 13 Clabelled organic carbon from ice algae was assimilated by individual Macoma compared to individual Monoporeia. Moreover, δ 13 C values of fatty acids in Macoma were much higher than those in Monoporeia, suggesting that Macoma directly assimilates fatty acids from their food source while Monoporeia might de novo biosynthesize fatty acids in their biomass. Additionally, both species had higher fatty acid contents and proportion of polyunsaturated components when they fed on ice algae compared to phytoplankton, implying that ice algae may be a better food than phytoplankton for Arctic benthos. Finally, analysis of bacteria-specific fatty acids in sediments (from both types of animal cores) showed that the δ 13 C values were enriched up to 400‰ relative to natural background values (−25% to −30‰), suggesting that organic carbon from fresh ice algae could be rapidly incorporated into bacteria biomass. The collective results of this experimental study suggest that the changes in food supplies due to reduction of ice coverage will have a greater impact on those benthic organisms that prefer ice algae to phytoplankton. This may lead to the potential changes in community structure favoring those organisms that can best utilize the fatty acids contained in both phytoplankton and ice algae.
Uploads
Papers by William G Ambrose