• Satellite evidence of physical features and processes in the Bering Sea

      Paluszkiewicz, Theresa (1982-05)
      Satellite infrared imagery is used to study temporal and spatial relationships of physical features and processes in the Bering Sea. A two-year collection of enhanced infrared imagery reveals that the maximum extent of the ice corresponds with the location of the Bering Slope current. Sea surface temperature patterns visually correlate with the 50-m and 70-m bathymetric contours. Processes which establish fronts in these regions are possible explanations for this correlation. Warm surface water extending from the Gulf of Alaska, through the Aleutian passes into the Bering Sea, is found simultaneously with warm surface water and eddies along the shelf break. Spatial and temporal relationships of these patterns imply surface circulation in the Bering Sea basin with inflow of Gulf of Alaska water through the Aleutian passes, cyclonic flow in the basin, and flow along the shelf by the Bering Slope current. Several generating mechanisms for the eddies are proposed.
    • Saxitoxins: role of prokaryotes

      Baker, Tracie Renee (2001-05)
      Saxitoxins, the toxins associated with paralytic shellfish poisoning (PSP), are synthesized by dinoflagellates, cyanobacteria, and possibly bacteria. The specific objectives of this study were to determine growth conditions that promote high and low levels of toxin accumulation in Aphanizomenon flos-aquae (cyanobacterium) and Pseudomonas stutzeri (bacterium). Putative saxitoxins of P. stutzeri identified by HPLC-FLD in this study, and previously by other laboratories, were determined to be 'imposters' based on their chemical and physical properties, suggesting that this bacterium may not synthesize PSP toxins. In the cyanobacterium, toxin production was enhanced under higher light intensities and temperatures. Toxin accumulation reached maximal levels when cellular nitrogen was from either (NO₃-+NH₄)-N or N₂-N, while urea-N drastically reduced toxin levels. These data will be used in future studies aimed at identifying the genes involved in saxitoxin synthesis via molecular technologies that rely upon expression of the 'saxitoxin genes' under different growth conditions.
    • Sea ice near-inertial response to atmospheric storms

      Stoudt, Chase A.; Simmons, Harper; Gradinger, Rolf; Johnson, Mark; Hibler, William (2015-05)
      A moored oceanographic array was deployed on the Beaufort Sea continental slope from August 2008-August 2009 to measure Arctic sea ice near-inertial motion in response to rapidly changing wind stress. Upward looking Acoustic Doppler Current Profilers detected sea ice and measured ice drift using a combination of bottom track and error velocity. An analysis of in-situ mooring data in conjunction with data from National Center for Environmental Prediction (NCEP) reanalysis suggest that many high and low pressure systems cross the Beaufort in winter, but not all of these create a near-inertial ice response. Two unusually strong low pressure systems that passed near the array in December 2008 and February/March 2009 were accompanied by elevated levels of near-inertial kinetic energy in the ice. The analysis suggests pressure systems which have a diameter to ground track velocity ratio close to 3/4 of the local inertial period can excite a large near-inertial response in the sea ice. It is conjectured that this results from the combined effect of resonance arising from similar intrinsic timescales of the storm and the local inertial period and from stresses that are able to overcome the damping of sea ice arising from ice-mechanics and damping in the ice-ocean boundary layer. Those systems whose intrinsic times scales do not approach resonance with the local inertial period did not excite a large near- inertial response in the sea ice. From an analysis of two storms in February 2009, and two in December 2008, it appears that wind stresses associated with previous low pressure systems preconditioned the ice pack, allowing for larger near-inertial response during subsequent events.
    • Seabird Habitat Use And Zooplankton Abundance And Biomass In Relation To Water Mass Properties In The Northern Gulf Of Alaska

      De Sousa, Leandra; Coyle, Kenneth; Weingartner, Thomas; Barry, Ronald; Springer, Alan; Jr., George Hunt (2011)
      Understanding of biological and physical mechanisms that control the Gulf of Alaska (GOA) ecosystem is of major importance to predicting the responses of bird and zooplankton communities to environmental changes in this region. I investigated seasonal (March-October) changes in seabird abundance in relation to changes in zooplankton biomass and water mass properties from 1998 to 2003. Oceanodroma furcata and Fratercula cirrhata were most abundant during the peak of the zooplankton production season (May-August). Overall abundance of seabirds did not follow seasonal changes in zooplankton biomass. Seabird abundance was low in the study area when compared to other regions in the GOA. Furthermore, low bird densities suggest that productivity in this study area is not high enough to sustain a significant seasonal increase in local seabird abundance. I further investigated the distribution and abundance of seabird foraging guilds across the neritic and oceanic domains in relation to water mass properties and zooplankton biomass during March and April. Overall zooplankton biomass increased from the inner shelf to the oceanic domain. Highest density of subsurface-foraging seabirds occurred in the middle shelf and surface-feeding seabirds were most abundant in the middle shelf and oceanic domain. Murre (Uria spp.) abundance was positively correlated with the biomass of Thysanoessa inermis, and Northern Fulmars (Fulmarus glacialis) were associated with cephalopod paralarvae and Eucalanus bungii. Elevated biomass of Thysanoessa inermis in March and April may be an important factor influencing habitat choice of wintering murres in this region. Lastly, I investigated the inter-annual variation in the abundance of sixteen zooplankton taxa in relation to water mass properties during May from 1998 to 2009. Significant variations in temperature, salinity and zooplankton abundance were identified. Thysanoessa inermis and Calanus marshallae had increased abundances in years when there was a strong phytoplankton spring bloom preceded by anomalously cold winters. However, abundances of Pseudocalanus spp., Neocalanus plumchrus/Neocalanus flemingeri, Euphausia pacifica and Oithona spp. were not strongly affected by relatively higher mean water temperatures. The abundance of zooplankton in the northern GOA was highly influenced by advective processes.
    • Seabirds at sea in relation to oceanography

      Day, Robert Hugh (1992)
      This study investigated the macroscale distribution of seabirds in relation to oceanography in a neritic environment characterized by well-defined water masses (the northern Bering Sea) and an oceanic environment characterized by weaker differences between water masses (the northern North Pacific Ocean). In the northern Bering Sea, the total density (birds/km$\sp2)$ of all seabirds combined and densities and/or frequencies of occurrence of seven of nine species of seabirds that exhibited significant differences among water masses showed the strongest attraction to Anadyr Water. In general, attractions were second highest in Bering Shelf Water, third highest in Two-layered Water (Alaska Coastal Water overlying Bering Shelf Water), and lowest in Alaska Coastal Water. This pattern of seabird distributions reflected distributions of zooplankton biomass, which were highest in Anadyr Water and consisted of species that were large enough to be eaten directly by seabirds. Further, whereas copepods in Bering Shelf Water also are large, they are much smaller in Alaska Coastal Water and, thus, must pass through more trophic levels to fishes before the energy is directly accessible to seabirds. Consequently, zooplankton-based food webs dominated in Anadyr and Bering Shelf waters and fish-based food webs dominated in Two-layered and Alaska Coastal waters. In addition, seabirds concentrated near a strong, mesoscale thermal front between Bering Shelf and Alaska Coastal waters. In the northern North Pacific, assemblages of seabirds exhibited three main groupings, a "subarctic assemblage," a "transitional assemblage," and a "'subtropical/tropical assemblage." These assemblages matched those for zooplankton, squids, and fishes in the same vicinity, suggesting that there are geographically- and temporally-stable biological communities in the North Pacific that are associated with well-defined, persistent physical environments. The total density of all seabirds combined and densities and/or frequencies of occurrence of 13 of 16 species of seabirds that exhibited significant two-way ANOVAs exhibited primarily a water mass effect; only one species exhibited primarily a year effect, and two exhibited primarily an interaction (i.e., a change in habitat use between years).
    • Seasonal abundance and diversity of nearshore fishes around Steller sea lion haulouts of Kodiak Island

      Hegwer, Catherine L. (2003-12)
      Nearshore fishes around haulouts are potential prey for Steller sea lions, especially pups, as they learn to forage and supplement their milk diets during weaning. Visual surveys in July and November 2001, and March, May and July 2002 were used to quantify spatial and temporal variation in fish diversity and abundance around two Steller haulouts and two control sites. SCUBA divers sampled depths of 9, 15, 21, 27, and 33 m. Concurrent habitat surveys were used to quantify substrate, macroalga and benthic invertebrate cover. Steller haulout sites had fewer fish than control sites, but similar species richness and species composition at the 9, 15 and 21 m depths during the summer sampling periods. In winter, fish were fewer but more evenly distributed. Habitats were not significantly different between Steller haulouts and control sites. All sites had seasonal cover of canopy forming kelp, and overstory algal cover was heavy down to 21 m. At approximately 27 m the habitat changed abruptly from kelp-covered bedrock to bare gravel and shell hash. While nearshore fish are an important component of Steller diets, results from this study do not indicate that fish assemblages at haulouts are substantially different from other headland sites.
    • Seasonal and interannual patterns of larvaceans and pteropods in the coastal Gulf of Alaska, and their relationship to pink salmon survival

      Doubleday, Ayla; Hopcroft, Russell; Gradinger, Rolf; Coyle, Kenneth (2013-12)
      Larvacean (=appendicularians) and pteropod (Limacina helicina) composition and abundance were studied with physical variables each May and late summer across 11 years (2001 to 2011), along one transect that crosses the continental shelf of the subarctic Gulf of Alaska and five stations within Prince William Sound (PWS). Collection with 53-µm plankton nets allowed the identification of larvaceans to species: five occurred in the study area. Temperature was the driving variable in determining larvacean community composition, yielding pronounced differences between spring and late summer, while individual species were also affected differentially by salinity and chlorophyll-a concentration. During the spring Oikopleura labradoriensis and Fritillaria borealis were most abundant and present at all stations. Late summer had highest abundances of O. dioica at nearshore stations, while F. borealis dominated numerically at outer stations. The 53-µm plankton nets collected higher abundances of Oikopleura spp., Fritillaria spp., and L. helicina than coarser 150 and 505-µm plankton nets. Limacina helicina abundance had a significant interaction effect among years, seasons and station location. Limacina helicina abundance in nearby PWS explained 30% of the variability in pink salmon survival; however, no significant correlations existed with larvacean or L. helicina abundances from the Gulf of Alaska stations.
    • Sensitivity to hydrocarbons and cytochrome P4501A enzyme activity in Arctic marine birds and waterfowl

      Riddle-Berntsen, Ann E.; Hollmén, Tuula; Buck, C. Loren; Aguilar-Islas, Ana (2017-12)
      The Arctic is host to a taxonomically diverse group of birds, including species of conservation and subsistence importance that spend many months of their annual cycle in the region. With prospects for oil and gas resource development and increases in vessel traffic in the Beaufort and Chukchi Seas, arctic birds could be valuable bioindicators to monitor contaminants and specifically hydrocarbons from crude oil. Using liver cytochrome P4501A (CYP1A) activity, I measured levels of hydrocarbon exposure in three bird species of subsistence importance: king eiders (Somateria spectabilis), common eiders (Somateria mollissima), and greater white-fronted geese (Anser albifrons). Over the course of three years, I collected liver samples during spring and fall hunts near Utqiaġvik (formally Barrow) and validated methods for both direct-take and opportunistic liver sampling. Enzyme activity results show significant differences in CYP1A activity levels among species, seasons, and years. Except birds collected during fall 2014, when significantly high enzyme activity was observed in all sampled species, all other collections resulted in median activity levels similar to those reported in other sea duck species in Alaska from un-oiled or non-industrialized habitats. I also used species-specific hepatocyte culture in a broader selection of arctic marine birds and waterfowl candidate bioindicators to assess and compare species CYP1A activity responses as a measure of sensitivity to hydrocarbons. Cytochrome P4501A results from hepatocyte cultures dosed with positive control reference reagents and Alaska North Slope crude oil showed differences in species responses. Based on sensitivity results, I recommend the common eider and common murre (Uria aalge) as bioindicators for use in CYP1A monitoring due to their consistent and measureable responses in our experiments. However, additional species are promising candidates (e.g., tufted puffin; Fratercula cirrhata) but further testing is needed. This is the first study of reference hydrocarbon exposure and comparative laboratory assessment of CYP1A inducing compounds for arctic marine birds and waterfowl and these results form the basis for hydrocarbon monitoring programs and risk assessments.
    • Six Thousand Years Of Change In The Northeast Pacific: An Interdisciplinary View Of Maritime Ecosystems

      Misarti, Nicole; Finney, Bruce (2007)
      The goal of this thesis is to develop long-term records of North Pacific ecosystems and explore relationships between change in marine ecosystems and prehistoric Aleut culture through soil chemistry, isotope analyses of lake cores, and isotope analyses of bone from archaeological middens. Chemical analysis of soils yielded differences in soils of various archaeological features as well as middens of varying composition. Sites that had no middens were chemically distinguishable from sites that did have middens helping to define resource consumption in the local region. An important result of this study is that no single ecosystem (nearshore benthic, coastal pelagic or deep-ocean pelagic) experienced the same changes in delta13C and delta 15N over the past 4,500 years. This suggests that changes in climate affected different ecosystems in unique ways. Only one change spans all species studied, the decrease in modern delta13C in comparison to delta13C of prehistoric specimens. According to these comparisons, the modern Gulf of Alaska may not be in the highly productive state that it was for the past 4,500 years, with the possible exception of the Medieval Warm Period. Lake core sediment analysis suggests an increase in salmon stocks in the Gulf of Alaska beginning ∼6,000 years ago, with a decrease during the Medieval Warm Period. In fact, salmon stocks in the Gulf of Alaska appear to be healthiest during periods of atmospheric cooler and wetter climate over the past 4,500 years. In comparing my paleoecological records to the archaeological record of the area it appears that humans were affected by changes in their environment but, even in relatively small numbers, humans also influenced local ecosystems for the past 6,000 years. By building on our understanding of long-term climate change and long-term fluctuations in ecosystems and trophic dynamics of species in the North Pacific, and through considering humans in the ecological context, we can better understand present conditions in marine ecosystems.
    • Small-scale variability in benthic food webs in the Northeastern Chukchi Sea

      Tu, Kelley Lannon; Blanchard, Arny; Horstmann-Dehn, Larissa; Iken, Katrin (2013-08)
      Benthic food web structure can differ over large scales across Arctic shelves in relation to hydrographic conditions, but little is known if such differences also may occur on smaller scales in hydrographically complex areas. The length, food sources, trophic composition, and energy distribution of benthic food webs in three study areas in the northeastern Chukchi Sea (i.e., Klondike, Burger, and Statoil, as part of the Chukchi Sea Environmental Studies Program) were compared using stable isotope analysis and bomb calorimetry. Food web length (four trophic levels), food sources, and linear models of food webs were comparable among areas. Marked differences in food web structure were observed when trophic levels were quantified by benthic biomass and abundance. High proportions of biomass and abundance of trophic level 3 taxa at Burger were attributed to high deposition of refractory material. High proportions of trophic level 1 and 2 taxa at Klondike and Statoil reflected availability of fresh material. Burger could potentially present a rich foraging ground for some benthic predators due to especially high benthic prey energy densities. Findings emphasize that marine food webs can vary on small spatial scales in accordance with hydrographic conditions, particularly when quantitative trophic level distribution is considered.
    • Spatial and temporal patterns of epibenthic community and food web structures in the Chukchi sea between 2004-2012

      Serratos, Carlos; Iken, Katrin; Bluhm, Bodil; Danielson, Seth (2015-12)
      The Chukchi Sea shelf, an area undergoing rapid environmental change and concurrently increasing human activity, supports communities of epibenthic organisms and food webs that are sustained by high primary productivity in the overlying water column and are influenced by physical environmental conditions. The goal of this study was to characterize these epibenthic communities (using trawl hauls) and benthic food webs (using carbon and nitrogen stables isotopes) in 2009 and 2012 and to identify persisting or changing patterns between 2004, 2009 and 2012 as part of NOAA's Russian-American long-term Census of the Arctic (RUSALCA) program. Fifteen stations each were sampled in August to September of 2009 and 2012 in the Chukchi Sea, of which eight repeat stations in the southern Chukchi were sampled in 2004, 2009 and 2012 for temporal comparisons. Epibenthic communities differed in structure between the northern and the southern study regions, with somewhat variable subgroupings within each of those larger regions between years. Overall biomass (mean 49680 ± 45510 g wet weight 1000 m⁻²) was dominated by echinoderms in particular at northern stations, followed by crustaceans. Repeat stations retained relatively consistent epibenthic community composition across sampling years, despite the at times drastic temporal variability in abundance and biomass. Point in time measurements of water column environmental variables (e.g., salinity, oxygen, temperature) were less strongly correlated to the epifaunal community structure than comparatively stable environmental measures (e.g., substrate type, depth, latitude). Benthic food web structure in the southern Chukchi Sea varied significantly and consistently between water masses in all study years, while δ¹⁵N and δ¹³C of pelagic particulate organic matter (PPOM) did not. This indicates that benthic consumers integrate the highly variable POM isotopic signatures and reflect long-term conditions. A persistent gap in δ¹⁵N values between PPOM and epibenthic consumers in nutrient-poor Alaska Coastal Water indicated that the majority of consumers in that water mass did not directly consume POM, which may undergo an additional trophic step of microbial processing before entering the benthic food web. In contrast, shorter food webs without this gap in the nutrient-rich Bering Sea Anadyr Water reflected tight pelagicbenthic coupling. The mostly consistent temporal patterns in epibenthic and food web structure compared to variable standing stock stress the importance of selecting multiple metrics for ecosystem monitoring. The data from this study may serve as a benchmark by which to measure a biological response to climate change and human impacts.
    • Spatial trends and environmental drivers of epibenthic shelf community structure across the Aleutian Islands

      Bland, Aaron; Konar, Brenda; Iken, Katrin; Johnson, Mark; Zimmermann, Mark (2018-12)
      The continental shelf around the Aleutian Islands supports important commercial and subsistence fisheries as well as multiple seabird and marine mammal populations. To sustainably manage these populations, more information is needed on the distribution of the benthic communities that support some of the top level consumers. Given the vast size and highly variable physical environment of the Aleutian Islands, it is likely that epibenthic community structure on the continental shelf will vary by geographic area and physical and oceanographic conditions. This project examined spatial patterns in Aleutian epibenthic shelf communities among oceanographic regions (island groups separated by major oceanographic passes) and islands within these regions and identified environmental drivers responsible for important community divisions. Benthic trawls were conducted at 12 Aleutian islands across four oceanographic regions to characterize epibenthic shelf community structure along the island chain. It was tested whether the spatial variability in shelf community structure among regions and islands was correlated to multiple environmental variables including bottom water temperature, water depth, distance from shore, exposure, bottom rugosity, sediment grain size, sediment chlorophyll content, and drift algal food subsidies. Overall, communities differed both among regions and among islands within regions. Communities in the Far Western region (Near Strait to Buldir Strait) differed from communities in other regions, largely due to a high density of sand dollars in the Far West. However, none of the measured environmental characteristics explained this difference. Additionally, there was no evidence for a break in epibenthic shelf community structure across Samalga Pass between the East and the Central regions, even though Samalga represents a biogeographic break for many other Aleutian community types, including zooplankton, fish, and kelp forest communities. Within the Central region, a characteristic soft-sediment community (including the flatfish Atheresthes spp. and the crabs Labidochirus splendescens and Chionoecetes bairdi) distinguished Adak Island from other Central islands. Compared with groundfish trawl surveys conducted by the Alaska Fisheries Science Center (AFSC), this study captured less fish but more invertebrates by biomass, which is likely related to different gear selectivity used by the two studies. These findings provide information on the distribution of Aleutian shelf communities that complement existing information from AFSC surveys. In particular, it is shown that there is potentially an important division in epibenthic shelf communities across Buldir Strait, in agreement with the literature identifying this pass as an important biogeographic break. Furthermore, it is suggested that future assessments of Aleutian epibenthic communities should employ a combination of sampling gear types to better represent various epibenthic taxa.
    • Sponges Dominant In The Alaska Intertidal: Biology, Ecology, And Genetic Diversity

      Knowlton, Ann Lynette; Highsmith, Raymond C. (2002)
      The role of the sponge, Halichondria panicea, in a Kachemak Bay, Alaska, intertidal community was investigated through field and laboratory experiments. The relationship between H. panicea and co-occurring macroalgae was studied and results indicate that removing macroalgae had no effect on sponge abundance. A laboratory feeding trial investigating H. panicea and its primary predator Archidoris montereyensis showed that nudibranchs consuming symbiotic sponge had higher feeding and egg production rates than individuals eating aposymbiotic sponge. In a simulated predation event, initial sponge growth rates into experimental feeding scars were high, indicating a response mechanism to tissue damage. A naturally occurring high nudibranch recruitment into a sponge population resulted in the local decline and extinction of both sponge and predator. Genetic studies revealed that at least two sponge species likely comprise the intertidal populations investigated, Halichondria panicea and H. bowerbanki. The reproductive cycle of H. panicea at exposed, hard-substrate habitats, and H. bowerbanki at sheltered, soft-sediment sites, exhibited seasonal peaks in oocyte production and maturation. H. panicea produced embryos 3--4 months earlier than H. bowerbanki. Six genomic DNA microsatellite loci were isolated and utilized in the characterization of two Halichondria panicea populations. The two populations were differentiated from one another with no significant inbreeding or bottleneck effect detected. All individuals were genetically unique, indicating little or no cloning. Sexual reproduction appears to be the dominant mode of reproduction maintaining the populations. DNA sequence analyses suggest that at least two species are likely present in Kachemak Bay. Distributions of ITS and CO1 haplotypes corresponded to habitat type. Analyses of the data grouped Alaska haplotypes separately from European samples of Halichondria panicea and H. bowerbanki , suggesting separate species may occur in Alaska. A re-examination of sponge systematics in southcentral Alaska is needed.
    • The status of Pacific Walrus (Odebenus rosmarus divergens) foraging habitat and diet around St. Lawrence Island

      Merrill, Tracie E.; Konar, Brenda; Hills, Susan; Bluhm, Bodil; Coyle, Kenneth (2008-12)
      With ongoing climate change, food resources may be reduced for Pacific walruses (Odobenus rosmarus divergens). Significant differences in walrus foraging habitat (benthic communities) or diet might indicate changes in prey quality or quantity. In this study, benthic infaunal biomass, abundance, and composition were compared between 1970-1974 and 2006 at stations southwest of St. Lawrence Island. Sediment grain size was compared because it strongly determines benthic community structure. Wet weights, counts, and species composition of prey items found in stomachs of walruses collected near the island were compared between the 1980s and 2007. Benthic invertebrate biomass and abundance increased mainly due to high Nuculidae biomass and abundance, although results may be skewed by low sample size. Silt fractions increased regionally. No significant dietary differences were detected in walruses. Walruses may have undergone a population redistribution or decline in response to benthic community changes that would be undetected in stomach content analyses.
    • Steller sea lion survivors: a retrospective on the impact of alternative research methods on an endangered species

      Shuert, Courtney; Mellish, Jo-Ann; Horning, Markus; Buck, C. Loren; Aguilar-Islas, Ana (2015-08)
      Two novel research approaches were developed to facilitate access to wild juvenile Steller sea lions. First, the Transient Juvenile Steller sea lion Project (TJ) facilitated numerous studies of physiology, behavior, and nutrition through temporary captivity (branded TJs, n=45) over the past decade. As a complement, a control group was sampled and released during capture events (FRs, n=35). Second, the Life History Tag (LHX) project was implemented within the TJ project to implant individuals (LHX-1, n=35) with internal transmitters to detect potential causes of mortality. Our goal was to evaluate the potential for long-term impacts of these two research programs on study individuals (Chapter 1) as well as identify potential metrics of survival for use in field efforts (Chapter 2). The first chapter used open-population Cormack-Jolly-Seber (CJS) mark-recapture models to project survival from resights of branded individuals in combination with demographic covariates in program MARK. TJ and FR groups were compared to identify the potential effect of temporary captivity on survival, while LHX-1 and non-implants were compared to examine a tagging effect on survival. Overall, our results mirror previous efforts to characterize survival in sea lions and indicate minimal long-term effects on mortality from research efforts, higher survival in females than males, and increasing survival rate with age. For the second chapter, a three-tiered approach to the decade of archived physiological data attempted to build links to survival in TJs through similar CJS modeling techniques. The first two levels looked at survival in relation to observed responses of handling stress through six a priori principle blood parameters measured at entry and exit. In addition, several condition indices were also incorporated into mark-recapture models, but separately considered when measured at entry and exit due to sampling inconsistencies. The third level evaluated the efficacy of single-point sampling to project similar trends for field use. Change in mass (kg) and white blood cell count (WBC, m/mm3) had the most support in predicting survival. Mass gains over captivity and slight increases in WBC resulted in a higher averaged survival rate. Minor support was identified for exit mass and entry WBC. A higher exit mass predicted a higher survival rate, while a higher entry WBC predicted a lower survival rate and may demonstrate the efficacy of single-point sampling as a management tool.
    • Structure of nearshore fish assemblages in relation to varying levels of habitat complexity

      Markis, Joel A. (2007-05)
      Complex kelp and rocky habitats can be beneficial to fishes, however, their use of these habitats is poorly understood in northern latitudes. This study examined nearshore kelp habitats to examine the potential effects of kelp density and substrate topography on nearshore fish communities in Kachemak Bay, Alaska. Fish were collected from multiple sand, understory kelp, and understory and canopy kelp sites, along with kelp and substrate complexity measurements. Standard Monitoring Units for the Recruitment of Fish (SMURFs), light traps, shrimp pots, and SCUBA visual surveys were all employed in these collections. Relative fish abundance and community composition varied temporally in all habitats. The dominant fish families were gadids, pleuronectids, hexagrammids, and sebastids. Habitat use differed significantly temporally and spatially in relation to size class. These differences were family specific. Community analysis of the dominant fish families showed that different habitat complexities supported distinct fish assemblages. Low complexity sand habitats were particularly important for juvenile pleuronectids in this region and complex nearshore kelp habitats may be essential fish habitat for juvenile Pacific cod. Although these high complexity nearshore environments may be challenging to sample, they support large fish assemblages and may be essential to a variety of fish families and species.
    • Structure, inter-annual variability, and long-term change in zooplankton communities of the Chukchi Sea

      Ershova, Elizaveta A.; Ершова, Елизавета А.; Hopcroft, Russell; Kosobokova, Ksenia; Gradinger, Rolf; Coyle, Ken; Winsor, Peter (2016-08)
      The Chukchi Sea is a complex transition zone between the Pacific and Arctic Oceans that has been experiencing dramatic change in recent decades due to shifting sea ice cover and increasing temperatures. We examine summer mesozooplankton communities of the Chukchi Sea in Alaskan and Russian waters during summers 2004, 2009, 2010 and 2012 within the scope of the RUSALCA (Russian-American Long Term Census of the Arctic) program. Community structure was highly variable between the study years, but was overall tightly correlated to water mass properties, with bottom temperature being the most significant factor influencing communities. Zooplankton biomass was dominated by the large copepod Calanus glacialis, while abundance was dominated by small shelf species of copepods, such as Pseudocalanus spp. and Oithona similis. The “cold" summers of 2009-2012 had nearly twice the biomass and abundance of zooplankton compared to the oceanographically “warm" summer of 2004. We discuss the implications of the inter-annual variability of planktonic communities within the Chukchi Sea, and the possible effects of longer-term climate change. We then look at distribution and population structure of an ecologically important species complex within the zooplankton, Pseudocalanus spp, and evaluate the implications of a warming climate for this group of copepods. While numerically dominating the communities, Pseudocalanus spp. has been historically understudied at the species level due to very subtle morphological differences between the species. Our approach used a combination of microscopic identification as well as a novel species-specific PCR identification method to discriminate between the four species found in the Chukchi Sea. Our results suggest that shifting oceanographic patterns and climate warming will have unequal impact on this group of organisms, arising from species-specific life histories and tolerance to environmental conditions. These recent observations on zooplankton are then placed into a historical context through comparison to data collected throughout the past half-century (1946-2012). Despite significant challenges associated with the highly variable spatial coverage and methodology of the available datasets, significant trends were detected. In addition to high levels of inter-annual variability, we demonstrate significant increases in zooplankton biomass and abundance in recent years compared to historical studies, as well as shifting distribution ranges for several key species. This signal was most pronounced within the copepods, particularly Calanus glacialis, which appears to be indirectly benefiting from warming of the region. While summer zooplankton communities of the Chukchi Sea have been primarily Bering-Pacific in character for as long as our records exist, continuing warming and ice loss are increasing the influence of Bering-Pacific fauna within the Chukchi region.
    • Summer distribution and habitat characteristics of fin whales (Balaenoptera physalus) and humpback whales (Megaptera novaeangliae) off Northeast Kodiak Island, Alaska

      Baraff, Lisa Susan (2006-12)
      Summer distributions of fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales were examined relative to bathymetry, oceanography, and zooplankton composition and density in Marmot and Chiniak Bays (Kodiak Island, AK) during 2002 and 2003. Habitat use and habitat partitioning were assessed using Monte Carlo and randomization tests, logistic regression analyses, and kernel density probability contours of high-use areas. Fin whales associated with deeper, cooler waters near areas of maximum slope and consistently used Marmot Bay. Fin whale spatial-temporal distribution likely coincided with Neocalanus copepod concentrations during early summer and adult euphausiids later in summer. Fin whale associations with Pseudocalanus copepods may relate more to that copepods' prevalence than to relevance as prey. Humpback whale site fidelity and association with shallow waters was evident in 2002, but not in 2003. Variability in humpback whale distribution was likely related to their exploitation of forage fish aggregations and threshold foraging needs. High densities of adult euphausiids may promote spatial overlap and shared resource use by fin and humpback whales. This mesoscale snapshot of a dynamic nearshore marine environment and the whales foraging there is an integral step toward identifying and characterizing important habitats for endangered fin and humpback whales.
    • A synopsis of the marine prosobranch gastropod and bivalve mollusks in Alaskan waters

      Foster, Nora Rakestraw (1979-12)
      This study presents information on the taxonomv and distribution of the marine prosobranch gastropod and bivalve mollusks from the waters surrounding Alaska. Three hundred fifty-two species of prosobranch gastropods and 202 species of bivalves are reported from these waters. Over 3,000 lots of specimens, representing 330 species and literature sources form the basis of this study. References, synonymy, geographic and bathymetric ranges are provided for each species. Characteristics used to identify the species of 66 genera are presented in tabular form. The greatest number of species is reported from the southern Bering Sea, the fewest from the Beaufort Sea. Most of the species have wide ranges in the eastern or western Pacific. New collecting records reported here extend the known ranges of 27 species. Eight species were previously unknown from Alaskan waters.