Now showing items 109-128 of 199

• #### Natural abundance of nitrogen(15) in a subarctic lake and biogeochemical implications to nitrogen cycling

Stable isotope ratios of nitrogen ($\delta\sp{15}$N) were employed to track the origin and fate of nitrogen in a subarctic lake, Alaska. The annual planktonic nitrogen cycle was dominated by N$\sb2$ fixation in spring and NH$\sb4\sp+$ assimilation in summer. In winter, microbial nitrification was the major sink for NH$\sb4\sp+$ and denitrification was accounted for most of the loss of NO$\sb3\sp-.$ The small isotope fractionation in nitrification is proposed as a result of substrate (NH$\sb4\sp+)$ limitation. The temporal and spatial homogeneity of the $\delta\sp{15}$N of dissolved organic nitrogen may be related to its large pool size and refractory nature. A stable isotope mass balance suggests that the winter phytoplankton was only composed of 10 to 20% of the suspended organic matter in water column due to low primary productivity during the ice cover period. A close correlation between $\delta\sp{15}$N of phytoplankton and $\delta\sp{15}$N of dissolved pools indicates that NH$\sb4\sp+$ was the predominant nitrogen source for non-N$\sb2$-fixing algae. The similarity of $\delta\sp{15}$N between a spring blue-green bloom and N$\sb2$ suggests an atmospheric origin for nitrogen. A mixing model estimated that the blue-green algal bloom derived approximately 70% of its nitrogen from molecular nitrogen. This fixed nitrogen was further transferred to higher trophic levels via the food chain and to other primary producers following mineralization. The $\delta\sp{15}$N of aquatic macrophytes indicates that non-rooted species obtained their nitrogen from the water column while rooted species obtained their nitrogen largely from the sediment. Evidence from dual isotope tracers ($\delta\sp{15}$N and $\delta\sp{13}$C) suggests that the zooplankton were supported by phytoplankton throughout the growing season despite an apparent abundance of detritus in the water column. Benthic fauna relied on either phytoplankton detritus or other organic matter in the sediment. The $\delta\sp{15}$N data exhibit only two to three trophic levels in both planktonic and the benthic communities in Smith Lake.
• #### Nitrogen utilization during spring phytoplankton bloom development in the southeast Bering Sea

Interactions between a high latitude, continental shelf, spring phytoplankton bloom and water column physics and chemistry were studied using measured rates of nitrogen uptake. Peak bloom conditions commenced when the mixed layer shallowed and minimized respirational losses. Integrative light-mixing growth models were accurate during early bloom stages. An advection-diffusion model associated peak bloom nitrate uptake with pycnocline mixing rates of 2.1 m d * in an 18 m mixed layer. The accumulation of surface buoyancy was a reliable index of peak bloom temporal and spatial "patchiness" since mixing rates influenced both respirational losses and nutrient supply. Maximum nitrogen specific uptake rates (h r .- 1 ), unlike those of carbon, coincided with peak bloom conditions. Although species com positions among peak bloom periods were similar, particulate C/N ratios were not. Apparently, both intercellular factors and prevailing mixing conditions influence specific uptake rates and cell composition. A large proportion of new (nitrate) to total productivity was associated with the dominance of the early bloom forming diatoms in the mixed layer. In the absence of these net plankton the residual nanoplankton dominated community exhibited a greater dependence on regenerated nitrogen. Nitrate uptake averaged 700 mg-at m during the spring bloom and 1 g-at m-2 year-1 The yearly f factor was 0.40. Nitrogen uptake based carbon productivity was 188 g C m -2 year -1 A mass balance of the inorganic carbon system indicates that nitrate uptake alone cannot account for all the carbon leaving the surface layer. The correspondence between 1SN0~ uptake measurements and nitrate decreases suggests the diffusion of slope water into the middle shelf is slow. Large scale meteorological patterns may be responsible for the inter annual variability observed in production. Frequent May storm activity prolonged peak bloom periods, while calm conditions promoted extensive Chijl layers. The passage of atmospheric low pressure system s was also associated with the cross shelf "pumping" of water masses.
• #### Non-linear dynamics of marine ecosystem models

Despite a rapid trend towards more realistic Nutrient-Phytoplankton-Zooplankton (NPZ) models, in which zooplankton are presented with multiple nutritional resources, investigations into the fundamental dynamics of these newer models have been limited. The objective of this dissertation was to explore the dynamical behavior of such NPZ models parameterized for the coastal Gulf of Alaska. With alternative stationary forcing regimes and zooplankton grazing functions, the dynamics of one-dimensional NPZ models were investigated for a range of specific predation rates (h) and predation exponents (q), which together define the form of the predation (model closure) function. Oscillations in state variables are shown to be an intrinsic property of the NPZ models, not dependent on variable seasonal forcing for their existence. Increasing mixed layer diffusivity or reducing mixed layer depth increased model excitability; it is hypothesized that this is due to the resultant increase in flux of utilizable nutrient. Model behavior was also strongly influenced by the form of both the grazing and predation functions. For all of the grazing functions implemented, Hopf bifurcations, where the form of the solution transitioned between steady equilibrium and periodic limit cycles, persisted across the q-h parameter space. Regardless of the values of h and q, with some forms of the grazing function steady equilibrium solutions that simultaneously comprised non-zero concentrations for all model components could not be found. The inclusion of sinking detritus in the model had important implications for the composition and excitability of model solutions, generally increasing the region of q-h space for which oscillatory solutions were found. Therefore, in order to correctly simulate the depth-explicit concentrations of model components, or to have an accurate understanding of the potential excitability of the system, inclusion of this component is valuable. This dissertation highlights the importance of understanding the potential impact that choice of functional response may have on the intrinsic oscillatory nature of a model prior to interpreting results from coupled bio-physical simulations. As we come to rely more on ecosystem models as a tool to interpret marine ecosystem functionality it will be important to improve our understanding of the non-linear behavior inherent in these models.
• #### Numerical Method For Tsunami Calculation Using Full Navier -Stokes Equations And The Volume Of Fluid Method

A two-dimensional numerical model was developed to study tsunami wave generation, propagation and runup. The model is based on solving the Navier-Stokes (NS) equations. The free-surface motion is tracked using the Volume of Fluid technique. The finite difference two-step projection method is used to solve NS equations and the forward time difference method to discretize the time derivative. A structured mesh is used to discretize the spatial domain. The model has been conceived as a versatile, efficient and practical numerical tool for tsunami computation, which could address a comprehensive understanding of tsunami physics with the ultimate aim of mitigating tsunami hazards. The prediction capability of tsunami generation, propagation and runup is improved by including more accurately the effects of vertical velocity/acceleration, dispersion and wave breaking. The model has the capability to represent complex curved boundaries within a Cartesian grid system and to deal with arbitrary transient-deformed moving boundaries. The numerical model was validated using laboratory experiments and analytical solutions. The model was used as a tool to determine the adequacy of the shallow water (SW) approximation in the application of tsunami simulations. Numerical results were compared with experimental data, analytical solutions and SW results in terms of the time-history free surface elevations and velocity. Reasonable agreements were observed based on the spatial and temporal distributions of the free surface and velocity.
• #### Nutrient Dynamics In The Northern Gulf Of Alaska And Prince William Sound: 1998--2001

The northern Gulf of Alaska (GOA) shelf is a productive coastal region that supports several commercially important fisheries. The mechanisms supporting such high levels of productivity over this shelf are not understood, however, since it is a downwelling-dominated shelf. In an effort to understand the mechanisms underlying such high biological productivity, nutrient distributions were determined 25 times throughout 1998, 1999, 2000, and 2001 from over the northern GOA shelf and in Prince William Sound (PWS). Deep water (>75 m) nitrate, silicate and phosphate concentrations were positively correlated with salinity indicating an offshore nutrient source. The average annual cycle was established, in which nitrate, silicate and phosphate responded seasonally to physical and biological processes. Ammonium concentrations were generally low and uniform (<1.2 muM) with occasional patches of higher concentrations. During each summer, an onshore flux of dense nutrient-rich bottom water onto the shelf was evident when the downwelling relaxed. This seasonal flux created nutrient reservoirs over the deeper shelf regions that were eventually mixed throughout the water column during the winter months. This annual evolution may be vital to the productivity of this shelf. A large degree of interannual variability was found during the study, which included El Nino (1998) and La Nina (1999) years. Spring phytoplankton biomass over the shelf was highest in 2000 when the upper waters were nutrient enriched and strongly stratified. The highest phytoplankton biomass was measured in May 1999 during the passage of a slope eddy, which demonstrated the potential of these phenomena to greatly enhance primary productivity. A large degree of spatial variability was also found, both cross-shelf and along-shelf. Hinchinbrook Canyon was found to consistently have high salinity, nutrient-enriched bottom waters suggesting it plays an important role in the transport of slope waters onto the shelf and probably into PWS. Along-shelf trends were found in the upper coastal waters in the winter and spring, with higher salinities, temperatures, and nutrient concentrations upstream of PWS. The nutrient dynamics were similar in PWS and over the shelf/slope in 2001; however, nutrient drawdown, followed by depletion, and the spring bloom appeared earlier and stronger in PWS.
• #### Nutritional and behavioral aspects of reproduction in walruses

Walruses (Odobenus rosmarus) at Marineland, California consumed food in increasing amounts as they grew larger out ate less per unit of body weight. Adult males consumed the most food in November - December, then fasted throughout the breeding season. Females apparently fasted during ovulation and birth. Females consumed 50% more energy while pregnant or lactating than when not pregnant or lactating. Male walruses spent more time displaying, and their displays were more stereotyped, during the breeding season. Females initiated and terminated interactions with the males during the breeding season, and those interactions were preceeded by displays. Females vocalized to the calf to initiate suckling bouts, reassure the calf, and to call the calf. Calves vocalized to initiate suckling bouts and indicate danger. When the calf was threatened, the female responded quickly by tusk strikes, kinesic tusk threats, vocal threats, or calling the calf. The calf tended to follow the female.
• #### Odors And Ornaments In Crested Auklets (Aethia Cristatella): Signals Of Mate Quality?

Crested auklets (Aethia cristatella) are small colonial seabirds that display an ornamental feather crest and emit a citrus-like odorant during the breeding season. In this study odors and ornaments were investigated as possible signals of mate quality. Crest size was negatively correlated with the stress hormone corticosterone in males, but this was not the case in females. Body condition was negatively correlated with corticosterone in females, but this was not the case in males. Corticosterone levels were interpreted as an index of physiological condition, and it was concluded that males with longer crests were more competent at meeting the social and energetic costs of reproduction. I hypothesized that the crested auklet odorant: (1) functions as a chemical defense against ectoparasites, (2) is assessed as a basis for mate selection, (3) is facilitated by steroid sex hormones. Laboratory and field experiments showed that synthetic replicas of the crested auklet odorant repelled, impaired, and killed ectoparasites in a dose-dependent fashion. Chemical concentrations in plumage were at least sufficient to repel and impair ectoparasites. Chemical emissions from breeding adult crested auklets peaked at the time of egg hatching when young are most vulnerable to tick parasitism. In males, chemical emissions were correlated with crest size, a basis for mate selection. Presentation of synthetic aldehydes elicited behaviors similar to those that occur during courtship. Captive crested auklets responded preferentially to synthetic replicas of their odor, and the highest frequency of response occurred during early courtship. These results show that the chemical odor could be a basis for mutual mate selection. Production of the chemical odorant may be facilitated by steroid sex hormones since octanal emission rates were correlated with progesterone in males. Finally it was determined that the chemical composition of odorants in crested auklets and whiskered auklets (A. pygmaea) differed in three key respects. This suggests that an evolutionary divergence occurred in the odorants of the two species similar to what has been suggested for ornamental traits. In conclusion, crested auklets appear to communicate with odors and ornaments, and these signals may convey multiple messages regarding condition, quality, and resistance to parasites.

• #### Organochlorines In Steller Sea Lions (Eumetopias Jubatus)

Existing populations of Steller sea lions (Eumetopias jubatus ) have declined precipitously over the last half-century. Investigations into the cause of this downward trend have focused on many different possible factors. Toxicity caused by the accumulation of organochlorines (OCs), such as polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane or dichlorodiphenyltrichloroethane (DDT), has been demonstrated in marine mammals and was considered here as one possible factor that may have contributed to the decline of Steller sea lions or their failure to recover. The focus of this project was to investigate the relationship of contaminant loads to hormone levels, specifically thyroid hormones and cortisol in Steller sea lions. Two approaches were taken to this study. Firstly, baseline hormone concentrations were identified for the thyroid hormones, thyroxine (T 4) and triiodothyronine (T3), and cortisol. This involves comparison and extrapolation. Secondly, possible risk effects were examined by comparing levels of OCs in captive and free-ranging Steller sea lions to known effects in related species with known physiological thresholds. Serum concentrations of total T4 were highest in Steller sea lions followed by total T3 concentrations. Concentrations of free T4 and free T3 were three to four orders of magnitude lower. Concentrations for all four thyroid hormone measurements tended to a lower level as animals matured beyond the neonatal stage. When thyroid hormones from captive sea lions were evaluated across seasons, all thyroid hormones were highest in the July to September period. Cortisol concentrations were similar in male and female pups. Cortisol varied with age but when considered in regards to time of year when sampled, followed a seasonal pattern. Cortisol was elevated in fall months in captive sea lions (non-pups), which is similar to what is seen in other marine mammals and is likely associated with the annual molt. Male pups from Alaska had lower levels of SigmaPCBs and SigmaDDT when compared to male pups from Russia. Female pups from Alaska were significantly lower in SigmaPCBs than Russian female pups as were female pups for SigmaDDT levels between areas. Anywhere from 12 to 64% (depending on rookery) of Steller sea lion pups investigated for contaminants had concentrations of SigmaPCBs that are high enough to cause physiological problems. Concentrations in blood taken monthly for 2 years in three captive Steller sea lions were similar at any given sampling time and followed a seasonal pattern with levels significantly higher in the summer months of July to September and lower in the three month winter period January to March. Concentrations of OCs in blubber samples collected quarterly for the captive females followed an analogous pattern to blood samples but the captive male sea lion was considerably lower and declined over the study period. A significant relationship between blubber contaminants and lipids was noted in the three captive Steller sea lions. Even though OC contamination has not been hypothesized to be the primary factor that precipitated the population decline, there is a potential for these chemicals to have a negative effect on the health of free-ranging Steller sea lions. These data suggest that concentrations of OCs in Steller sea lions may be high enough to cause endocrine or reproductive dysfunction and could potentially impact fertility or fecundity. Therefore, OC contaminants can not be dismissed as a contributing source to either the decline or the failure to recover of the Steller sea lion population.
• #### Otters, sea stars, and glacial melt: top-down and bottom-up factors that influence kelp communities

Kelp beds are important features of the Alaska coastline and provide habitat, protect coastlines, and support commercial and subsistence harvests. Kelp beds are affected by top-down and bottom-up factors, which are changing due to human and climate-related impacts. The influences of these top-down and bottom-up factors on kelp beds are investigated in three chapters. My first chapter investigated the influence of glacial discharge on recruitment and early community development in subtidal kelp communities by monitoring benthic sessile algae and invertebrates on cleared rocks across a glacial gradient along with various physical and biological parameters in the summers of 2013-2014. It has been predicted that Alaska's glaciers will lose 30-60% of their volume by 2100. The melt from glaciers increases sedimentation and lowers salinity, impacting important habitat-providing kelp. I found that sites upstream from glacial discharge had higher kelp recruitment than downstream sites, and that up to 72% of the variation in community development was related to mobile invertebrates and kelp in the surrounding community. Glacially-influenced environmental factors did not explain any variation that was not already explained by biological factors. My second chapter explored whether patterns in the recruitment of the dominant canopy kelp, Nereocystis luetkeana and the subcanopy kelp, Saccharina latissima were a result of dispersal limitation or failure to grow to macroscopic size. My goals were to determine 1) whether glacial melt conditions affect adult fecundity (spore production) of either species, 2) how sedimentation affects early gametophyte growth and survival in each species, and 3) whether competitive interaction between species at the gametophyte stage is altered by sediments. I found that glacial melt conditions did not affect the fecundity of either species, but sedimentation affected survival and competition. Saccharina latissima was the superior competitor under high sediment conditions. Because glacially-influenced coastal areas often have little exposed hard substrate and predation by sea otters and sea stars on clams can provide hard substrate for kelp colonization, my third chapter examined methods for determining predation on clams by these predators without direct observation. I found that foraging pits of sea otters and sea stars could not be distinguished using quantitative measurements. In contrast, shell litter proved useful in quantifying relative foraging rates. Clam consumption by sea otters and sea stars was equal at all but one site. Collectively, my thesis chapters provide information on the effects of glacial discharge on microscopic and early kelp life stages in Alaska which can be incorporated into management practices.
• #### Pacific walrus use of higher trophic level prey and the relation to sea ice extent, body condition, and trichinellosis

The changing Arctic ecosystem may prompt Pacific walruses (Odobenus rosmarus divergens) to change their usual diet of lower trophic level prey (e.g., benthic invertebrates) by increasing the consumption of higher trophic level prey (HTLP). Prey-switching may have consequences to walrus populations through increased energetic costs, increased stress response, declines in body condition, and exposure to diseases, including the zoonotic parasite Trichinella spp. Trichinella is possibly transmitted to walruses via predation or scavenging on seals. The goal of this study was to quantify reliance on HTLP using stable carbon and nitrogen isotope ratios, and assess potential correlations among consumption of HTLP and sea ice extent, sex, Trichinella infection, body lipid stores, and cortisol concentrations used as an index of the stress response. Walrus diet is comprised of ~1-22% HTLP and reliance on HTLP may be correlated with sea ice extent in a complex way. Trichinella was present in ringed seal (Pusa hispida, 1/57), Arctic fox (Vulpes lagopus, 3-7/32), and polar bear (Ursus maritimus, 1/1), but was not detected in walruses (0/137) regardless of %HTLP in the diet. Walrus blubber and attached skin contained 44.6 ±12.4% lipid wet weight, which was lower than that found for other Arctic marine mammals; however, the inclusion of skin likely decreased our %lipid values. While the absolute value of %lipid from blubber and attached skin was not a suitable substitute for %lipid from blubber only, we were still able to detect the influence of biological factors, with sex-linked variability in walrus lipid stores observed. Cortisol analysis from full-thickness blubber resulted in a wide range of concentrations (2.77 to 34.04 ng/g), but showed that this stress hormone can be extracted from blubber. While neither %lipid nor blubber cortisol was correlated with the proportion of HTLP in walrus diet, they may serve as minimally-invasive methods for health monitoring of walruses. Overall, dietary plasticity of walruses is robust and switching to HTLP is not likely to have immediate adverse effects on the Pacific walrus population.
• #### Paleoceanographic shifts in the Gulf of Alaska over the past 2000 years: A Multi-proxy perspective

The Gulf of Alaska (GOA) is a dynamic region influenced by climate variability on time scales ranging from days to millennia. Recent regime shifts suggest interdecadal GOA primary productivity patterns, yet it is unclear whether such fluctuations extend beyond the instrumental record. This thesis examined the nature of prevalent climatic and oceanographic patterns before the twentieth century using several marine sediment core proxies for paleoproductivity and paleoceanography. Sediment cores were from two locations: Bay of Pillars, Kuiu Island, in southeast Alaska (56.63 ̊N, 134.35 ̊W), and a central midshelf location (GAK4) along the Global Ecosystem Dynamics (GLOBEC) Seward Line (59.25 ̊N, 148.82 ̊ W). Proxy data from these cores include: percentages of organic carbon, nitrogen and biogenic opal; organic carbon-to-nitrogen ratios; stable isotope ratios from sediment organic matter (δ13C and δ15N) and foraminifera tests (δ13C and δ18O); and foraminifera faunal analysis. Bay of Pillars proxy data suggest that the onset of the Little Ice Age (LIA) ca. 1200 AD coincides with pulses of decreased salinity and increased productivity. GAK4 proxy data indicate increased productivity and decreased terrestrial input over the past century; as well as fresher surface water was during the latter portion of the LIA (1716 – 1894) and positive Pacific Decadal Oscillation phases.
• #### Paralytic shellfish poisoning: the relationship between Alexandrium abundance and psp toxins on Kodiak Island, Alaska

Paralytic shellfish poisoning (PSP) events have severe negative impacts on Alaska commercial shellfish fisheries as well as recreational and subsistence harvests. This study, designed to improve existing PSP monitoring programs, involved the use of a rapid sandwich hybridization assay to detect and quantify the relative abundance of Alexandrium catenella based on species-specific LSU rRNA targeted oligonucleotide probes. Blue mussel (Mytilus edulis) toxicity, expressed as saxitoxin equivalents, was determined using the ³H-Saxitoxin receptor binding assay. Shellfish toxicity was relatively low in both 2000 and 2001 compared to historically high values on Kodiak, but exhibited pronounced late spring and late summer peaks, in both years at four to seven sampling sites. Temporal and spatial variability in shellfish toxicity among sites, seasons, and years suggested dynamic, and possibly unpredictable, Alexandrium bloom events. Importantly, DNA probe data revealed a strong association between Alexandrium abundance and shellfish toxicity. The results also demonstrated that increases in Alexandrium abundance preceded elevated toxin levels in shellfish, indicating that this assay may prove useful as a monitoring tool to predict toxic events in shellfish before they are harvested. Water column nutrients and climate data were evaluated to determine if bloom-triggering mechanisms could be identified.
• #### Pelagic nitrogen cycle in an arctic lake

A mass balance for nitrogen was developed for the water column of Toolik Lake and the isotope tracers 15N and 14C were used to examine the phytoplankton ecology with respect to dissolved in organic nitrogen (ammonium and nitrate). The nutrient budget showed an oligotrophic ecosystem with important flux terms few and small in magnitude. Nitrogen input was primarily from inflowing rivers and was dominated by the dissolved organic fraction. Ammonium release from sediment provided the only other major source of nitrogen to the lake water. Toolik acted as a nitrogen sink, trapping 18% of the annual input. Retention was almost exclusively (98%) as dissolved organic nitrogen. Tracer experiments suggested chronic nitrogen deficiency in the phytoplankton, but indigenous populations were well-adapted for utilizing characteristically low levels of nutrient. Phytoplankton showed a high affinity for both nitrate and ammonium as well as a lack of discrimination between the two forms of inorganic nutrient. The ambient concentration was the most important factor regulating uptake, with light and temperature of secondary importance. More than 66% of the dissolved in organic nitrogen supporting phytoplankton productivity was derived from local recycling, with the remainder from sediment efflux and riverine input. Dissolved organic nitrogen from inflowing waters probably provided an additional, important source of nutrient for the phytoplankton.
• #### Phosphorus metabolism of several aquatic microorganisms

Several taxonomically diverse aquatic microplankton were described growing at phosphorus (P) concentrations that limit growth in many natural aquatic systems. Because natural aquatic systems are subject to periodic fluctuations in P levels, both steady-state (via continuous culture) and transient (via batch culture) growth were described. Complete growth kinetic descriptions of Synechococcus Nageli (strain A) and Scenedesmus quadricauda were used to predict the relative competitive abilities of these species when P was the growth-limiting nutrient. These descriptions, coupled to their morphological characteristics, were used to construct partial physiological profiles for each organism. The profiles indicate that S. Nageli (strain A) (a small unicellular blue-green alga) is better suited for growth in P-limited oligotrophic niches than is S. quadricauda (a green alga). However, results from kinetic experiments with these and several other microplankton, show that such physiological profiles are not necessarily indicative of profiles for taxonomically related species.
• #### Physical And Biological Factors Affecting The Diel Vertical Migration Of Walleye Pollock

The mechanisms underlying diel vertical migration (DVM) in marine fishes are unclear, although it is generally thought that this behavior is influenced by light, hydrography, food availability and predator avoidance. In the North Pacific Ocean, walleye pollock (Theragra chalcogramma) undergo DVM as juveniles, ascending to the surface at night and returning to the bottom at dawn. Adults are generally considered demersal. The objective of this research was to examine the effect of light, temperature and prey availability on the DVM of adult pollock. The work was undertaken to further our understanding of pollock biology, and the mechanisms underlying DVM in marine fishes in general. The study was conducted in the northern Gulf of Alaska in April, August and November 2003. Trawls < 80 m in April, and < 50 m in August, suggested that at least some portion of the pollock population was ascending to within 20 m of the surface in spring and summer. In November, acoustic data and targeted hauls > 100 m indicated that adults were not ascending to the surface at night, and that DVM behavior was occurring at depth. Euphausiids were the primary component of the diet in April and August. Decapods, primarily the shrimp Pandalus borealis, were the main component of the diet in November. Pollock passed through the thermocline during their ascent to the surface at night in August, and there was no relationship between the mean depth of pollock and the isolume (line of equal light intensity) necessary for visual foraging. In contrast, there was a significant relationship between the biomass of adult pollock above the 200 m isobath and the isolume necessary for visual foraging in November. Pollock did not pass through the thermocline at this time. It was concluded that in August adults ignore the isolume and thermocline, simply tracking the movements of euphausiid prey to feed upon them near the surface at night. In November, when euphausiids are no longer in patches, pollock shoals migrate up and down with the isolume necessary for visual foraging to feed on decapods.
• #### Physical environmental and biological correlates of otolith chemistry of Arctic marine fishes in the Chukchi sea

Life history movement patterns in marine fishes can be determined by otolith chemistry if environmental variables are reflected in the otoliths. Arctic cod (Boreogadus Saida), Arctic staghorn sculpin (Gymnocanthus tricuspis), and Bering flounder (Hippoglossoides robustus) are abundant Arctic fishes in the Chukchi Sea with overlapping distributions. Physical environmental data, demersal fishes, bottom seawater, and sediment interface seawater samples were collected from the Chukchi Sea Offshore Monitoring in Drilling Area (COMIDA) cruise on July 30, 2009 and the Russian American Long-term Census of the Arctic (RUSALCA) cruise from September 3 to 30, 2009 in the Chukchi Sea. Magnesium (Mg), strontium (Sr), barium (Ba), and calcium (Ca) were measured with an inductively coupled plasma mass spectrometer (ICP-MS) on the most recent growth edge of otoliths and in whole fish blood, as well as Ba in bottom and sediment interface seawater. Environmental variables and fish age correlated with Arctic cod and Arctic staghorn sculpin otolith signatures while only environmental variables correlated with Bering flounder signatures. Elemental correlations were not always consistent for the variables tested among species. The complexity of this multi-element tool suggests otolith chemistry may not be useful to determine life history movement patterns of these demersal Arctic fishes in offshore waters.
• #### Physiological and behavioral responses of tanner crabs (Chionoecetes bairdi) to handling, emersion and temperature

Commercially harvested Tanner crabs (Chionoecetes bairdi) are exposed to physical stressors during capture and sorting including changes in temperature and oxygen availability. This study characterizes the physiological and behavioral responses of Tanner crabs exposed to air (emersion) at 8 and -15°C for various durations. Concentrations of glucose and lactate in hemolymph measured between 30 and 120 min following emersion for 45 min differed between animals exposed to 8 or -15°C. Glucose concentrations were higher among animals emersed at 8°C than those exposed to -15°C within the intervals sampled. Lactate concentrations were unchanged at intervals following emersion at 8°C, while they were elevated at 120 min following emersion at -15°C. Rates of oxygen consumption (VO₂) increased immediately following 15, 30, and 45 min emersion at 8°C, whereas 30 and 45 min emersion at -15°C resulted in depressed VO₂. All crabs survived handling and emersion at 8°C, while exposure to -15°C resulted in increased mortality. Thus, differences among physiological parameters corresponded with differences in percentage survival between the two temperature treatments. While not providing a causal relationship between survival and physiology, the metabolic responses of Tanner crabs following a simulated capture protocol provide a predictive index of subsequent survival.