• Factors affecting estuarine populations of Nereocystis luetkeana in Kachemak Bay, Alaska

      Chenelot, Héloïse Anne Claude (2003-12)
      Nereocystis luetkeana forms extensive kelp beds in Kachemak Bay, Alaska. Salinity and turbidity gradients apparently regulate kelp bed distribution throughout this estuary. The beds are large at the entrance of the bay, only solitary stands occur in the inner bay, and no kelp is found at the head of the bay. The role of salinity and turbidity on Nereocystis sporophyte growth was investigated by performing reciprocal transplants among three beds along the bay axis and regularly measuring stipe growth. The effects of salinity and light on spores were studied in the laboratory by recording sinking tendency, settlement success, germination success, and germ tube length under different salinity and light levels. Grazing effects of Lacuna vincta impacted the survival of Nereocystis transplants in-situ and on plants of different age classes in the laboratory. Overall, this study suggests a possible negative estuarine effect on sporophytes transplanted from the outer to the inner bay and on certain aspects of spore development. Herbivory pressure had significant localized effects on Nereocystis survival and was most pronounced on juvenile plants. The dynamics of Nereocystis kelp beds in Kachemak Bay results from large-scale environmental factors and local-scale biological processes.
    • Factors influencing zooplankton populations in Alaskan sockeye salmon (Oncorhynchus nerka) nursery lakes: insights from limnological and paleolimnological analyses

      Sweetman, Jon N.; Finney, Bruce; Barry, Ronald; Hughes, Nicholas (2001-08)
      The relative importance of sockeye salmon, invertebrate predators, and other environmental factors in structuring the size and abundance of zooplankton populations was examined in a series of 23 lakes from southern Alaska. Zooplankton abundance was strongly related to sockeye density, along with nutrient availability and alkalinity. The mean size of Bosmina longirostris, the dominant herbivorous cladoceran, was positively correlated with the abundance of the predatory copepod, Cyclops columbianus. Changes in the size and abundance of Bosmina remains over the past 300-500 years were then determined for sediments from two lakes on Kodiak Island, Alaska. The zooplankton communities showed varying responses to past changes in salmon populations, resulting from relative changes in the magnitude of adult salmon-derived nutrient loading and in predation pressure from juvenile sockeye and cyclopoid copepods. Knowledge of how various factors impact zooplankton can have important implications for the effective management of sockeye within these lake systems.
    • Fatty acid profiles of Alaskan Arctic forage fishes: evidence of regional and temporal variation

      Dissen, Julia; Hardy, Sarah; Horstmann-Dehn, Lara; Oliveira, Alexandra (2015-08)
      Fatty acids, the main components of lipids, are crucial for energy storage and other physiological functions in animals and plants. Dietary fatty acids are incorporated and conserved in consumer tissues in predictable patterns and can be analyzed in animal tissues to determine the composition of an individual's diet. This study measured the variation in fatty acid profiles of three abundant Arctic forage fish species, Arctic Cod (Boreogadus saida), Canadian Eelpout (Lycodes polaris), and Longear Eelpout (Lycodes seminudus) across multiple years (2010-2013) and geographic locations (Beaufort and Chukchi seas). These fishes are important prey items of marine mammals, sea birds, and predatory fishes, and as such they serve as a critical trophic step connecting lower trophic-level production to higher level predators. Analyzing forage fish fatty acid profiles across multiple years and geographic locations can provide insight into system-level trends in lipid transfer through the Arctic ecosystem. Fatty acid profiles differed among species, with Arctic Cod having higher concentrations of pelagic zooplankton indicator fatty acids, and Eelpout species containing higher concentrations of indicators for benthic prey. While the two Eelpout species displayed major overlap in fatty acid profiles, differences in individual fatty acids may represent niche separation between Canadian and Longear Eelpout in the Beaufort Sea. In addition to variation between species, fatty acid profiles also differed in Arctic Cod between the Beaufort and Chukchi seas, and among collection years. High lipid content and energy-rich fatty acid classes observed in Chukchi Sea Arctic Cod relative to the Beaufort Sea Arctic Cod may indicate favorable feeding conditions in this region over the years sampled, and high energy density of Arctic Cod as prey. Despite the within-species variation observed, the results of this study suggest that Alaskan Arctic forage fish with different foraging ecology can be distinguished based on fatty acid profile, which could be useful in studies that use fatty acid data to characterize diets of top predators.
    • The feeding, movement, and growth of pink salmon, Oncorhynchus gorbuscha, fry released from a hatchery in Prince William Sound, Alaska

      Urquhart, David Lindsay (1979-12)
      As part of a study that investigated the ability of Prince William Sound to support large numbers of juvenile salmon, the movements, feeding, and growth of pink salmon, Oncorhynchus gorbuscha, fry released in the springs of 1977 and 1978 from the Port San Juan hatchery, are described. Fry were released in Sawmill Bay but preferred the waters of adjacent Elrington Passage where they remained for up to two months. Nursery areas in the Passage established by the fry in 1977 were not occupied to the same degree in 1978. Fry fed initially on epibenthic harpacticoid copepods but soon switched to feeding on calanoid copepods. Fry growth rates and diet are comparable with results of other studies. Fry behavior affected sampling and may account for between-year differences detected in growth. Weather, food abundance, and the condition of out-migrants may also account for between-year differences in fry behavior and growth.
    • Fifty years of Cook Inlet beluga whale ecology recorded as isotopes in bone and teeth

      Nelson, Mark A.; Wooller, Matthew J.; Iken, Katrin; Quakenbush, Lori T. (2017-12)
      Beluga whales (Delphinapterus leucas) are found across the Arctic and Subarctic in seasonally ice covered waters. Five stocks of beluga whales are associated with the waters near Alaska for at least part of the year and four of those five stocks are abundant and commonly hunted by Alaskan Natives. The belugas resident in Cook Inlet are also an important cultural and subsistence resource to Alaskan Natives in the area, but a ~50% decline in abundance in the 1990's led to the stock being designated as depleted under the Marine Mammal Protection Act in 2000 and listed as endangered under the Endangered Species Act in 2008. Numerous studies of beluga whales in relation to stranding events, predation (killer whales), parasitism, disease, contaminants, and other potential population threats have not identified the reason for their inability to recover. Changes in diet have been considered, but are difficult to study because observations of feeding in muddy water and beluga stomachs are difficult to obtain. To investigate the past feeding ecology of beluga whales from Cook Inlet I sampled bone and teeth for isotopic analyses. I sampled bone from 20 individuals that died between 1964 and 2007 for stable carbon and nitrogen isotope analysis (values expressed as δ¹³C and δ¹⁵N values). I also micro-sampled annual growth layer groups in the teeth of 26 individuals representing the years from 1962 to 2007. Bone and tooth data showed a general decrease in δ¹³C and δ¹⁵N values over time. The δ¹³C values from analyses of growth layer groups declined from -13.4‰ to -16.2‰ and δ¹⁵N values declined from 17.2‰ to 15.4‰. Although these values are consistent with a change in feeding ecology over time, the magnitude of the decrease in δ¹⁵N values (~2‰) is insufficient for a full trophic level shift (~3‰).The relatively large decrease in the δ¹³C values over the same time period (~3‰), however, is much greater than a full trophic level shift (~1‰) and suggests an increase in prey associated with freshwater, which typically have lower δ¹³C values than prey associated with marine water. To test this hypothesis I analyzed the strontium isotope composition (⁸⁷Sr/⁸⁶Sr ratios) of growth layer groups in teeth from a sub-set of individuals. The resulting ⁸⁷Sr/⁸⁶Sr ratios trended away from the global marine signature (0.70918) over time and toward the more freshwater signatures measured in rivers flowing into the upper reaches of Cook Inlet. These results indicate that the diet of Cook Inlet beluga whales has changed over time. This could be from feeding on different, more freshwater derived prey species, or from feeding on the same species, but on individuals from locations with a more freshwater influence. Both of these interpretations are consistent with population survey data indicating a retraction in beluga range into the upper reaches of Cook Inlet. This study presents the first evidence of a long term (~50 years) change in Cook Inlet beluga whale feeding ecology. The consequences of this change toward more freshwater-influenced prey, and how this change relates to Cook Inlet beluga whales' decline or recovery remains unknown. However, to better examine this change in feeding ecology a follow-up study will; 1) develop a strontium isoscape for the Cook Inlet watershed; 2) analyze more teeth to better analyze changes in feeding ecology by demographic group (sex, age); and 3) analyze growth layer groups from Bristol Bay beluga teeth for a comparison with Cook Inlet belugas to determine if the changes represent an ecosystem change within Cook Inlet or a broader scale change affecting another region. This study builds towards a better understanding of the changes in Cook Inlet beluga feeding ecology and will help to determine if changes in diet could be a factor in their recovery.
    • Foraging Ecology And Nutritional Stress Of Tufted Puffins (Fratercula Cirrhata) Inferred From Stable Isotopes, Fatty Acid Signatures, And Field Endocrinology

      Williams, Cory T.; Buck, C. Loren (2008)
      Prey availability has a major impact on the reproductive output of seabirds, yet information on seabird diets throughout the breeding season is often lacking. Although reduced prey availability is known to affect the growth and survival of nestling seabirds, few studies have demonstrated similar effects on indices of adult body condition. I used stable isotopes and fatty acid (FA) signatures to investigate seasonal and age-related variation in the foraging niches of tufted puffins (Fratercula cirrhata). I conducted captive feeding experiments to determine whether inferences based on these techniques are affected by moderate food restriction during growth. I also examined how adult puffins prioritize the competing goals of maximizing the growth rate of their offspring and maintaining their own condition, as measured by body mass and by the stress hormone, corticosterone (CORT). Food restriction during nestling growth affected adipose tissue FA signatures and resulted in blood that was depleted in 15N and 13C relative to well-fed controls. However, effects of nutritional restriction on delta 15N, delta13C, and FA signatures were small compared to variability in prey, indicating physiological effects do not preclude use of these techniques as dietary tracers. Stable isotopes and FA signatures of free-living adults indicated foraging niches changed over the course of the breeding season. Stable isotopes suggest chick-rearing adults and nestlings feed at the same trophic level while FA signatures indicate that parents feed nestlings a diet different from their own. Body mass of adult puffins declined between incubation and chick rearing periods. For females the magnitude of mass decline did not differ between years, whereas for males the decline was greater in the year where young puffins fledged at a lower mass. In a separate analysis, baseline CORT values of adults of both sexes did not differ between years, but were lower than those observed in a separate study area during two consecutive years with low rates of nestling growth and survival. Assuming elevated CORT and reduced body mass impact survival and/or future fecundity, these results suggest the cost of reproduction may be higher for those adults able to fledge young in years characterized by low productivity.
    • Foraging patterns of northern fulmars in Alaska inferred from fatty acid signature analysis

      Wang, Shiway W. (2005-12)
      Diets of Northern Fulmars (Fulmarus glacialis) in the North Pacific are poorly known, and thus relationships of fulmars to supporting food webs and their potential sensitivity to ecosystem variability, such as that driven by a changing climate, also are uncertain. I employed a new technique, fatty acid (FA) signature analysis, to examine dietary differences among fulmars at three colonies in Alaska. I predicted that 1) signatures of adipose tissue and stomach oils would differ because the time scale each depot reflects differ and/or because adipose tissue FAs may be influenced by predator metabolism, while stomach oil FAs may be influenced by differential uptake; 2) fulmar diets would differ between colonies located in distinct oceanographic settings, which create unique habitats for prey assemblages; 3) diets would differ temporally within colonies because of inter-annual variability in the physical environment resulting in variation of prey FA signatures; and 4) diets of adult fulmars and their chicks would be similar because they feed by regurgitation. I found that FA signatures of adipose tissue were significantly different than those of stomach oil; there were conspicuous spatial and temporal differences in adipose tissue signatures; but diets of adults may differ from those of chicks.
    • Freezing tolerance and survival experiments with various intertidal organisms from Kachemak Bay, Alaska

      Patterson, Heather Kristine (2004-08)
      Intertidal organisms at high latitudes experience multiple stresses created by freezing, including ischemia, free water reduction, and distortion and destruction of cells, and in response have adapted behavioral and physiological solutions. This study examined the response of intertidal organisms in Kachemak Bay, Alaska to freezing through laboratory experiments and field studies. Mytilus trossulus, Balanus glandula, Protothaca staminea and various limpets (Lottidae) survived freezing conditions to -10 and -20°C, depending on the season. Mytilus trossulus and B. glandula survived multiple freeze events at -10°C. Seasonal freeze response was not induced by exposure to low air temperature in M trossulus. Exposure to O⁰C was not fatal to any of the species studied: M trossulus, B. glandula, P. staminea, limpets, Fusitriton oregonensis, Katharina tunicata and Leptasterias hexactis. Preliminary results suggest that M trossulus and P. staminea have an ice nucleator. Freezing avoidance may be one cause for the differences seen in seasonal distribution patterns of F. oregonensis, Nucella lima, Onchidella borealis, Siphonaria thersites and Littorina sitkana. The current study demonstrated that intertidal organisms in this region exhibit differing responses to freezing. Some organisms survive freezing conditions by freeze tolerance, while others may avoid it by moving lower in the intertidal.
    • Growth Rates Of Calanoid Copepods In The Northern Gulf Of Alaska, And Their Relationships To Temperature, Chlorophyll And Body Size

      Liu, Hui; Hopcroft, Russell (2006)
      The juvenile growth rate and development time of the dominant calanoid copepods in the northern Gulf of Alaska were investigated. The utility of the artificial-cohort method was successfully validated as the most practical approach for estimating copepod growth rates in this ecosystem. The underlying functional responses of growth rates to temperature, food concentration, and body size were thoroughly explored for Neocalanus flemingeri/plumchrus, Metridia pacifica, Calanus marshallae, C. pacificus and Pseudocalanus spp. These results lay the foundation for the calculation of copepod secondary production and ongoing ecosystem modeling activities for the northern Gulf of Alaska, and will contribute to the refinement of global models of copepod growth rates. In general, the rates of copepod growth were negatively size-dependent. However, a positive relationship between growth rate and body size within each stage emerged in response to food climate. The effect of temperature on growth rates was prominent, but confounded with food conditions and body sizes, which also vary with temperature conditions. Copepod growth rates were significantly related to chlorophyll a, and were frequently food-limited, particularly for later developmental stages during the summer. Compared to other co-occurring calanoid copepods, egg-carrying species (i.e. Pseudocalanus) tend to grow slowly to meet their unique life history strategy. Statistically, more variability in temperature corrected growth rates can be explained by composite nonlinear models that incorporate development stage and body size into the traditional Michaelis-Menten relationship. The species-specific comparisons of the measured growth rates with those predicted by global models of copepod growth suggested more direct measurements of copepod growth rates in various ecosystems are required for fully appreciating the global patterns of copepod growth. Caution should be used in the widespread application of those models for estimating copepod secondary production, especially in polar and sub-polar waters.
    • Habitat characteristics of black oystercatcher breeding territories

      McFarland, Brooke A.; Konar, Brenda; Goldstein, Michael I.; Rosenberger, Amanda (2010-05)
      Habitat use in birds is often related to forage resources and predation avoidance. The large, long-lived black oystercatcher is a shorebird that defends a composite breeding territory for foraging in the intertidal zone and nesting in the immediate upland. Predation on young is a major source of mortality for many bird species, including black oystercatcher. As these are long-lived birds with many reproductive opportunities, adult survival, associated with forage resources, is expected to be more important in habitat use than less-predictable breeding success. To identify which factors most influence black oystercatcher breeding territory use, logistic regression models were developed and tested in south-central Alaska and tested in southeast Alaska. Intertidal community composition was sampled at a subset of sites. All known breeding sites in Kenai Fjords National Park and western Prince William Sound, plus sites in southeast Alaska, were matched with available breeding sites based on substrate and exposure classifications. Two factors available breeding related to predation avoidance, greater distance to vegetation and isolation from the mainland, were the most important variables in habitat models. Intertidal community composition did not vary between known breeding and available breeding sites. This suggests black oystercatchers choose breeding territories that reduce predation risk, contrary to expectations.
    • Habitat use of Pacific herring (Clupea pallasii) in Prince William Sound, Alaska

      Kelly, Seanbob R. (2007-12)
      To determine the spawning area contributions of Pacific herring (Clupea pallashii) larvae to nursery bays, otolith chemical analysis was conducted on juvenile fish collected from 1995 to 1997 in Prince William Sound, Alaska. The otolith edge, representing the chemical signature of the known capture location, and the otolith core, representing the unknown spawning ground chemistry, were compared with discriminant function analysis to infer spawning area origin. Chemical signatures of ⁸⁷Sr/⁸⁶Sr, ⁸⁸Sr/⁴⁸Ca, ²⁴Mg/⁴⁸Ca, and ¹³⁸Ba/⁴⁸Ca were used to identify broad spawning regions from inner and outer PWS that persisted for the three years sampling period despite significant interannual variability in otolith edge chemistry within nursery bays. Age of juvenile Pacific herring, age-0, 1, 2, did not significantly affect the otolith edge signatures; thus, this study is able to conclude from the otolith core chemistry that spawning areas do not contribute equally to nursery bays. This is the first demonstration that otolith chemical signatures can be used to identify the important spawning areas of this commercially important species in the Gulf of Alaska coastal areas.
    • Harmothoe imbricata: species complex or complex species?

      Gastaldi, Angela; Lopez, J. Andres; Hardy, Sarah; Kelley, Amanda; Sikes, Derek (2019-05)
      Accurate estimates of species diversity are constrained by cryptic species complexes, in which multiple closely related species are grouped under a single species name due to the absence of clear morphological differences. Cryptic diversity is known to be prevalent in polychaete worms, a mostly marine group commonly known as bristle worms. A recent survey of polychaete diversity discovered that the widespread scale-worm Harmothoe imbricata comprises multiple distinct mitochondrial lineages based on analysis of the Cytochrome c oxidase I (COI) gene, which is often referred to as the 'barcoding' gene. Analyses based solely on DNA sequences from COI may overestimate the number of lineages comprising a cryptic species complex, so it has been recommended that cryptic species investigations incorporate nuclear gene sequences. The goal of this study was to determine whether the incorporation of DNA sequences from the nuclear genome corroborates the designation of H. imbricata as a cryptic species complex. I sequenced segments of COI and five nuclear genes: ITS1, ITS2, H3, and portions of the 18S and 28S genes of H. imbricata and analyzed them using distance measures, maximum likelihood, and Bayesian inference. I compared phylogenetic trees produced from mitochondrial and nuclear DNA sequences, as well as from a combined mitochondrial/nuclear dataset. Harmothoe imbricata was found to include five mitochondrial lineages, whereas the nuclear sequences only supported four well-defined lineages. These results corroborate previous reports showing COIbased cryptic species investigations find more lineages than nuclear DNA based investigations. These results provide additional lines of evidence that H. imbricata is a cryptic species complex. These divergent lineages likely arose after being separated during the last glacial maximum but they are now found in sympatry. A thorough morphological study of H. imbricata populations may reveal phenotypic differences correlated with the genetic lineages identified here.
    • Heat And Freshwater Controlling Processes On The Northern Gulf Of Alaska Shelf

      Janout, Markus A.; Weingartner, Thomas; Coyle, Kenneth; Hedstroem, Ketherine; Johnson, Mark; Okkonen, Stephen (2009)
      We examined conditions and processes that control the distribution of heat and freshwater on the northern Gulf of Alaska (GOA) shelf. Cross-shelf heat gradients are weak throughout the year, while salinity gradients are substantial due to the impact of coastal freshwater runoff. Outer shelf water properties are influenced by large anticyclonic eddies, while the inner and middle shelves may be regulated by wind and freshwater runoff dynamics around the Alaska Coastal Current (ACC). On the outer shelf, anticyclonic eddies propagate from the eastern GOA southwestward along the continental slope, where they favor on-shelf (off-shelf) transport of saline and nutrient-rich (fresh and iron-rich) waters Certain along-shelf locations are identified where low-salinity coastal waters are found near the shelfbreak within reach of eddies and may be regions of enhanced cross-shelf freshwater transport. The eddies have lifetimes of ~5 years and increase in size and sea level anomaly west of the Seward Line, which implies more vigorous eddy cross-shelf exchange in the northwestern GOA. By comparison, on the inner shelf the heat and freshwater distribution is dominated by large coastal river runoff, which forces the ACC and controls the vertical distribution of temperatures through stratification. In May 2007, the coastal GOA revealed some of the lowest ocean temperatures since the early 1970s, initiated by strong atmospheric cooling and reduced coastal runoff in November 2006. Stepwise regression shows that 81% of the variability of deep temperatures is explained by salinity stratification and air-sea heat fluxes. Weak baroclinic flow in May 2007 likely aided the cooling through reduced along-shore heat transport. A more detailed examination of heat transport indicated that along-shore heat flux convergence in the ACC may re-supply 10-35% of the heat removed by air-sea fluxes throughout the coastal GOA cooling season, while the annual mean cross-shore heat flux convergence is insignificant. Spatial gradients show increasing heat fluxes from off- to on-shore and from east to west. The cross-shore gradients result from wind speed gradients due to ageostrophic near-shore wind jets near coastal mountains, while the along-shore gradients result from larger-scale pressure systems. While the ACC advects coastal freshwater around the GOA shelf its waters are subjected to disproportional heat loss west of the Seward Line.
    • Heavy metals in the sediments of an arctic lagoon, northern Alaska

      Sweeney, Michael Devlin (1984-12)
      The total abundances of V, Cr, Mn, Fe, Co, Ni, Cu, and Zn in oxic, nearshore sediments of north arctic Alaska, are similar to those of corresponding pristine or pre-industrial-age sediments of many tropical-temperate regions, and thus do not reflect the unique weathering and depositional processes of the Arctic. Laboratory experiments on metal partitioning suggest that about 50% of the metal contents (<20% for V, Cr), which are bound predominantly in Fe oxides, may be mobilized into solution following the onset of reducing conditions at the sediment surface. A three-part extraction design would be effective in discriminating the three major associations of heavy metals in the sediments: easily leachable, Fe hydroxides, and refractory particles, and is recommended for use in monitoring the nearshore Beaufort Sea for future contamination by heavy metals.
    • Hemocyte and tissue changes by crude oil in the blue mussel Mytilus edulis

      McCormick-Ray, M. Geraldine (1983)
      This study examines the effects of Prudhoe Bay crude oil on the number and types of circulating hemocytes, on the phagocytic response, on spawning progression, and on internal structural changes. The number of hemocytes was reduced with 4-5 week exposure to 1000 nL/L of oil; a significant number of individuals showed a higher than average cell count with longer exposure. An increase in agranulocytes in the 8-9 week control population does not occur in populations exposed to 1000 nL/L and 500 nL/L of oil for 8-9 weeks, but, the phagocytic response was significantly depressed. The Chi-square test showed that oil interferes significantly with progression of spawning. Analysis of internal tissue structure indicates that oil can affect adipogranular storage cells, vesicular tissue, and digestive tubule cells. The changes occurring in circulating hemocytes are not necessarily consistent with changes in internal morphology.
    • Humpback whale (Megaptera novaeangliae) entanglement in fishing gear in northern southeastern Alaska

      Neilson, Janet L. (2006-05)
      The prevalence of non-lethal entanglements of humpback whales (Megaptera novaeangliae) in fishing gear in northern southeastern Alaska (SEAK) was quantified using a scar-based method. The percentage of whales assessed to have been entangled ranged from 52% (minimal estimate) to 71% (conditional estimate) to 78% (maximal estimate). The conditional estimate is recommended because it is based solely on unambiguous scars. Eight percent of the whales in Glacier Bay/Icy Strait acquired new entanglement scars between years, although the sample size was small. Calves were less likely to have entanglement scars than older whales and males may be at higher risk than females. The temporal and spatial distribution of commercial fisheries is complex and difficult to correlate with these results. The percentage of whales with entanglement scarring is comparable to the Gulf of Maine where entanglement is a substantial management concern. Consequently, SEAK humpback whale-fisheries interactions may warrant a similar level of scrutiny.