• Decadal Variability In The Arctic Ocean: Greenland-Iceland-Norwegian Seas Ice-Ocean-Atmosphere Climate System

      Dukhovskoy, Dmitry Stanislavovich; Johnson, Mark; Proshutinsky, Andrey (2003)
      This study investigates the decadal variability of the Arctic Ocean---Greenland, Iceland, Norwegian Seas (GIN Sea) system and possible mechanisms driving variability. The theoretical foundation of this work is the theory of Proshutinsky & Johnson [1997] that two major climate states of the Arctic---Anticyclonic Circulation Regime (ACCR) and Cyclonic Circulation Regime (CCR)---are driven by variations in the freshwater contents of the Arctic Ocean and the GIN Sea. It is hypothesized that the Arctic Ocean and the GIN Sea form an auto-oscillatory ice-ocean-atmosphere climate system with a quasi-decadal period of interannual variability. The system is characterized by two stages: (1) cold Arctic (ACCR)---warm GIN Sea with weak interaction between the basins; (2) warm Arctic (CCR)---cold GIN Sea with intense interaction between the basins. Surface air temperature and dynamic height gradients between the basins drive the auto-oscillations. This study investigates interactions between the Arctic Ocean and the GIN Sea. To test the hypothesis, a simple model of the Arctic Ocean and Greenland Sea has been developed. The Arctic shelf processes have been parameterized in a box model coupled with an Arctic Ocean module. Both the Arctic Ocean and Greenland Sea modules are coupled with a thermodynamic ice model and atmospheric models. Several model experiments have been conducted to adjust the model and to reproduce the auto-oscillatory behavior of the climate system. One of the major results of this work is the simulation of auto-oscillatory behavior of the Arctic Ocean---GIN Sea climate system. Periodical solutions obtained with seasonally varying forcing for scenarios with high and low interaction between the regions reproduce major anomalies in the ocean thermohaline structure, sea ice volume, and fresh water fluxes attributed to ACCR and CCR regimes. According to the simulation results, the characteristic time scale of the Arctic Ocean---GIN Sea system variability reproduced in the model is about 10--15 years. This outcome is consistent with theory of Proshutinsky and Johnson [1997] and shows that the Arctic Ocean---GIN Sea can be viewed as a unique auto-oscillating system.
    • Decomposition and adsorption of peptides in Alaskan coastal marine sediments

      Luo, Honghong (1994)
      In organic-rich coastal sediments, hydrolyzable amino acids make up a substantial fraction of the sedimentary content of organic nitrogen. How this organic nitrogen resists decomposition and is preserved in sediments is poorly understood. In order to investigate the factors controlling mineralization and preservation of hydrolyzable amino acids, decomposition and adsorption of peptides were studied in suboxic and anoxic pore water and sediments from Resurrection Bay (RB) and Skan Bay (SB), Alaska. Five tritium-labeled peptides, basic di-lysine, acidic di-glutamic acid, and neutral di-alanine, tri-alanine and hexa-alanine, were used as tracers. In filtered pore water, the hydrolysis rates were usually low. The exception was that the initial enzymatic hydrolysis of di-alanine and di-glutamic acid was rapid in SB pore water. The hydrolysis rates of both peptides increased with concentration. In sediments, hydrolysis was found to be the rate-limiting step of peptide decomposition. Alanyl and glutamyl peptides were hydrolyzed faster than lysyl peptide, and the hydrolysis rates among alanyl peptides decreased with increasing molecular weight. Peptide hydrolysis was affected more by molecular structure than by oxic or anoxic conditions. Adsorption of lysyl peptide to sediments was greater than that of other peptides. Basicity enhanced peptide adsorption more than increased molecular weight. Sedimentary organic matter was mainly responsible for peptide adsorption. The different patterns of peptide adsorption in RB and SB sediments were related to the greater total organic carbon concentration in SB sediment. Some of the peptide adsorption was irreversible. Adsorbed peptides were more resistant to biological decomposition than dissolved peptides. Adsorption may be an important step in the process of peptide preservation in sediments, and thus the preservation of sediment organic matter during early diagenesis.
    • Defining genetic population structure and historical connectivity of snow crab (Chionoecetes opilio)

      Albrecht, Gregory T.; Hardy, Sarah M.; Lopez, J. Andres; Hundertmark, Kris J. (2011-08)
      The snow crab (Chionoecetes opilio) is a valuable commercial resource within the Bering Sea, as well as other areas in the North Pacific and Atlantic Oceans. Large populations are known to exist within the Chukchi and Beaufort Seas, including recently discovered commercial sized individuals (Beaufort). However, genetic connectivity throughout these regions has not been examined until now. Based on seven polymorphic microsatellite loci, relatively low population genetic structuring occurs throughout the Alaskan region (Gst = 0.001). This homogeneity is likely due to long-distance larval dispersal, adult migrations, and a possible recent population expansion following the last glacial maximum. Furthermore, meta-population analysis was conducted for Alaskan and Northwest Atlantic stocks. Although significant genetic divergence characterizes the West Greenland stock in relation to all other populations, low divergence (Gst = 0.005) was found between Atlantic Canada crabs and those from the Alaska region. Larval dispersal between regions is highly unlikely due to the transit distance. Therefore, low divergence is likely the result of a recent population expansion into the Northwest Atlantic <5000 years ago.
    • Density and distribution of meiofauna in the northeastern Chukchi Sea

      Hajduk, Marissa; Blanchard, Arny; Hardy, Sarah; Bluhm, Bodil (2015-05)
      Meiofaunal communities in the northeastern Chukchi Sea (Alaska) are poorly known and were investigated to determine coarse taxonomic composition, distributional patterns, and density and biomass. Core samples were taken in August through October 2012 from van Veen grabs at depths of 20-45 m, in order to assess meiofauna community structure and associations with environmental and biological variables. Overall, density and biomass were dominated by nematodes, harpacticoid copepods, and foraminifera. Total meiofaunal density (9-13 ind. cm-2) was lower than in some deeper polar regions (e.g., Yermak Plateau and Nansen Basin), but generally fell within the range of published estimates for the Arctic and sub-Arctic. Total region-averaged biomass (27.4 mg C m-2) was similar to estimates for the deep Arctic Makarov and Amundsen Basins, but was much lower than shallow and productive sub-Arctic regions such as the Oosterschelde estuary (North Sea, Netherlands) and intertidal areas in Kongsfjorden (Svalbard), and some Arctic locations in the Barents Sea. The ratio of meiofaunal to macrofaunal biomass (1:438) was comparable to estimates from less productive Arctic basins and from fjords, but was unexpectedly lower than other productive polar shelves (e.g., Barents Sea shelf). Regression analysis and Canonical Correspondence Analysis (CCA) ordination suggest water depth, % mud, and TOC are important predictors of nematode and harpacticoid copepod densities, whereas temperature, TOC, and macrofaunal biomass were correlated with meiofaunal community structure. These variables are proxies for the topographic control and water circulation in the region, and suggest circulation with advected nutrient input as the primary driving force behind community density and distribution patterns.
    • Describing Forage Fish Availability In Coastal Waters Of The Kodiak Archipelago, Alaska

      Guo, Lei; Wynne, Kate; Foy, Robert; Coyle, Kenneth; Hillgruber, Nicola; Schaufler, Lawrence (2010)
      Assessing the availability of forage fishes is key to understanding fluctuations in populations of apex predators that prey upon them, including pinnipeds and seabirds in the Gulf of Alaska. In this study, multiple aspects of forage fish availability were measured in coastal waters of the Kodiak Archipelago, Alaska, in May (2004 & 2005), August (2004 & 2005), November (2006), and April (2007). Efforts were focused on four pelagic species that consistently dominated midwater trawl catches and have been described as important prey for upper trophic level predators around the Archipelago: walleye pollock (Theragra chalcogramma), Pacific herring (Clupea pallasii), capelin (Mallotus villosus), and eulachon (Thaleichthys pacificus). Fatty acid and stomach content analyses were combined to estimate the diet composition of these forage fishes as a means of identifying the immediate source of energy they transfer to upper trophic level taxa. Values of copepod-originated fatty acids indicated underestimation of dietary copepods by stomach content analysis, which suggests that fatty acid analysis should be used to supplement conventional methodologies in forage fish field studies. Lipid content and fatty acid composition were highly variable within species, suggesting that the use of average values at the species level should be avoided in fine-scale ecological investigations. Mesoscale horizontal distribution and energy density of forage fishes were measured in May and August (2005) to assess the prey fields available to local apex predators over critical periods of their life history. Dense post-spawning aggregations formed seasonal energetic "hotspots", exemplified by herring schools on the northwest side of the Archipelago in May and capelin schools on the northeast side in August. Results presented in this dissertation offer key information needed to identify energetic pathways of significance to upper trophic level consumers in the Kodiak Archipelago. Understanding local trophic interactions and their role in regional apex predator population fluctuations will improve efforts to develop trophodynamic models and ecosystem-based fishery management plans in the North Pacific Ocean.
    • Development And Application Of A Methodology To Estimate Regional Natural Conditions For Trace Metals In Marine Sediments Of Southcentral Alaska's Coastal Region

      Dasher, Douglas H.; Kelley, John J.; Duffy, Lawrence; Mueter, Franz; Naidu, A. S.; Perkins, Robert (2010)
      Increasing levels of resource development and population growth along Alaska's relatively pristine coastline require responsible environmental stewardship that is based on scientifically defensible monitoring and assessment. This thesis develops a methodology to assess the spatial distribution of coastal sediment trace metals and estimate their natural condition along Alaska's coastline. Marine sediments provide a better integrated long-term signal for naturally occurring and anthropogenic chemicals than repeated water measurements. The first of three manuscripts reports on marine sediment trace metal concentrations from a probabilistic sampling survey of Alaska's Southcentral coastal region. Results are described on a proportional basis, i.e., percent of estuary area, for the distribution of As, Cd, Cr, Cu, Pb, Hg, Ni, Ag, and Zn in the sediments. With the exception of naturally elevated Cr and Ni at a site bounded by a chromite ore body, sediment trace metal concentrations measured represent non-analmous levels. The second manuscript develops natural conditions for fluvial trace metal inputs from two major Southeast Alaska coastal watersheds: Cook Inlet and Copper River. The stream sediment trace metal natural conditions place levels in the adjacent coastal sediments into context. Two exploratory data analysis techniques, the Tukey Box plot and Median + 2 Median Absolute Deviation, combined with geochemical mapping are used to develop stream sediment trace metal natural conditions. The third manuscript builds on the first two to develop a methodology to estimate coastal sediment natural conditions. Population estimates for the cumulative area 90% UCB 95% sediment trace metal of interest obtained from the sampling survey methodology and screened reference sites is used to establishing an upper threshold value for regional natural conditions. While this work establishes natural condition marine sediment trace metal levels for this region, the significance of these levels from an ecotoxciological perspective remains to be established. Additional studies are needed along other sections of Alaska's coastline, coupled with biological assessments, if Alaska is to develop relevant sediment quality guidelines.
    • Development, growth, and egg production of Centropages abdominalis and Neocalanus flemingeri from the eastern subarctic Pacific

      Slater, Laura Michelle (2004-08)
      Copepods dominate oceanic mesozooplankton in terms of abundance and biomass thus contributing a significant source of secondary production. I determined development, growth, and egg production of Centropages abdominalis and Neocalanus flemingeri at temperatures representative of the northern Gulf of Alaska in spring. Median development times from eggs to adults were 42 and 59 days for C. abdominalis at 5 and 7°C, respectively, and 117 days from eggs to copepodite stage five for N. flemingeri at 5°C. Average copepodite growth rates were 0.08 and 0.17 d⁻¹ for C. abdominalis at 5 and 7°C, respectively, and 0.15 d⁻¹ for N. flemingeri at 5°C. In situ egg production of C. abdominalis was 37 ± 22 eggs female⁻¹ d⁻¹ (mean ± S.D.), corresponding to a growth rate of 0.14 d⁻¹. Lifetime fecundity of N. flemingeri determined at 5°C was 535 ± 258 eggs female⁻¹ (mean ± S.D.). Comparing these results to in situ populations reveals that C. abdominalis may be food limited during the summer and fall, while N. flemingeri is likely not food limited in late spring. Overall, this information helps clarify the life history patterns of these two species and allows production to be estimated and models of secondary production created for conditions within the Gulf of Alaska.
    • Dietary effects on protein turnover in three pinniped species, Eumetopias jubatus, Phoca vitulina, and Leptonychotes weddellii

      Inglis, Susan D.; Castellini, Michael; Atkinson, Shannon; Barboza, Perry; Carpenter, James; Rea, Lorrie (2019-05)
      The role of dietary protein in pinniped (seal and sea lion) nutrition is poorly understood. Although these marine mammals derive the majority of their daily energetic needs from lipid, lipids cannot supply essential amino acids which have to come from protein fractions of the diet. Protein regulation is vital for cellular maintenance, molt, fasting metabolism, exercise and development. Proteins are composed of linked amino acids (AA), and net protein turnover is the balance between protein synthesis from component AA, and degradation back to AA. Protein regulation is influenced by dietary intake and quality, as well as physiological and metabolic requirements. In this work, pinniped diet quality was assessed through comparisons of amino acid profiles between maternal milk, blood serum, and seasonal prey of wild juvenile Steller sea lions (Eumetopias jubatus) in Southcentral Alaska. Both Pacific herring (Clupei pallasi) and walleye pollock (Gadus chalcogramma) showed similar patterns to milk in essential and branched chain amino acid content. Serum amino acid profiles suggest the juvenile sea lions were not in protein deficit at the time of capture. Protein metabolism in the blood and urine was assessed through turnover studies using amino acid tracers. The turnover kinetics of ¹⁵N-labelled glycine in the blood amino acid and protein pool, red blood cells, and urine urea were measured in wild adult female Weddell seals (Leptonychotes weddellii) in the Antarctic. Labelled glycine moved quickly into serum protein and red blood cells (1-2 hours) and urinary urea (2-4 hours). The turnover rates in the blood amino acid and urine urea pools demonstrated a reduced turnover rate associated with molting. Lastly, whole body protein turnover experiments using a single bolus ¹⁵N-labelled glycine tracer method with endproduct collection of blood, feces and urine were conducted on 2 Cohort groups of captive Alaskan harbor seals over 2 years. Season was found to have the greatest effect on whole body protein turnover, which increased during the winter and decreased in the summer molt. Conversely, protein intake decreased during the winter and increased in the summer molt. This pattern corresponded with an increase in mass and protein synthesis in the winter, while mass decreased and protein degradation rates increased in molting seals. Weaning also influenced the patterns with reduced protein turnover in newly weaned animals that had recently transitioned from milk to a fish diet. This project presents results on whole body protein turnover rates in nonfasting pinnipeds and reveals that protein turnover is strongly regulated by developmental and seasonal physiological and metabolic demands.
    • Distribution, Growth And Egg Production Of Euphausiids In The Northern Gulf Of Alaska

      Pinchuk, Alexei I.; Hopcroft, Russell (2006)
      The euphausiids Thysanoessa inermis, Thysanoessa spinifera and Euphausia pacifica are key pelagic grazers and important prey for many vertebrates in the Gulf of Alaska (GOA). This thesis provides the first account of distribution, egg production, growth, development, and temporal variability in abundance of the euphausiids in relation to environmental variations in the northern GOA. T. inermis and T spinifera were abundant on the shelf within 120-130 km from the coast, while E. pacifica originated from offshore and was advected onto the shelf during summer. E. pacifica produced multiple broods with brood size strongly related to ambient chlorophyll a concentrations. In contrast, T. inermis released eggs once in the season and its brood size did not depend on chlorophyll content. Early development of these species showed a remarkably similar response to changes in temperature. The highest molting increments were observed during the spring phytoplankton bloom for T. inermis, and in summer for T. spinifera and E. pacifica, suggesting coupling with food availability. The molting rates were strongly influenced by temperature. Growth rates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm d-1 or 0.023 d -1 for T. inermis) and July (0.091 mm d-1 or 0.031 d-1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm d -1 (0.016 d-1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5�C) and ambient chlorophyll-a concentration fit a Michaelis-Menten curve (r2=0.48), but such relationships were not significant for T. spinifera or E. pacifica. Reproduction of T. inermis occurred during April in 1998 and 2003, and was extended through May in 1999-2002. The spawning of T. inermis and T. spinifera was related to the spring diatom bloom on the inner shelf, while the spawning of E. pacifica occurred later in season, when the water temperature increased. A strong increase in abundance of T. inermis, associated with the extended colder phase in the North Pacific, indicates that progressive cooling in 1999-2002 may have resulted in greater reproductive success of early spawning T. inermis on the inner shelf.
    • Diversity, abundance and fate of ice algae and phytoplankton in the Bering Sea

      Szymanski, Anna; Gradinger, Rolf; Iken, Katrin; Collins, R. Eric (2014-12)
      Sea ice algae are an essential part of Arctic and subarctic ecosystems. They significantly contribute to total algal primary production, serve as an early spring food source for both pelagic and benthic biota, and can seed the spring phytoplankton bloom during periods of ice melt. In the subarctic Bering Sea, virtually nothing has been known about the composition of the ice algal community, its magnitude, and its connection to pelagic and benthic ecosystems. This study, therefore, focused on the diversity, abundance, and ultimate fate of ice algae in the Bering Sea using sea ice, water and sub-ice sediment trap samples collected during two spring periods: ice growth (March to mid-April) and ice melt (mid-April to May) in 2008 and 2009. Ice algal species composition was comparable to those in Arctic regions. The phytoplankton species inventory was similar to that found in the overlying ice, suggesting that the spring phytoplankton were seeded from the ice algae. Algal abundance in the ice was on average three orders of magnitude higher than in the water column throughout both periods, as the extensive Bering Sea ice cover in 2008-2009 delayed the phytoplankton bloom. There was a substantial increase in the vertical flux of algal cells beneath the ice during the period of ice melt, but measurable amounts appeared as early as mid-March. The majority of this flux was composed of healthy algal cells, making it a rich food source for benthic organisms. Differences in the relative species composition between ice and trap samples indicate that algal fate was influenced by the species specific sinking rate of algal cells, among other factors, in the water column. In conclusion, ice algae in the Bering Sea are diverse and abundant, and contribute to both pelagic and benthic systems.
    • Diving physiology of the ringed seal: adaptations, capability and implications

      Ferren, Howard Jennings (1980-08)
      Adaptations that influence duration of diving in the ringed seal, Phoaa (Pusa) hispida were examined. Mean blood volume was 234 ml/kg lean body mass (LBM) and oxygen capacity was 30.7 ml O2/100 ml of whole blood, yielding a total blood oxygen capacity of 70 ml O2/kg LBM. Abrupt and prolonged bradycardia occurred upon submersion. Experimental dives indicated submersion durations of up to 18 minutes before the onset of physiological dysfunction. The percentage of LBM represented by the brain is least in the relatively large Weddell seal (0.2%), greater in the harbor seal (0.7%) (the compared species) and greatest in the ringed seal (1.4%); this sets the requirement for minimum obligatory oxygen consumption. The differences observed in diving durations between the three species is considered to be mainly the consequence of brain/body size relationship.
    • The effect of under ice crude oil spills on sympagic biota of the Arctic: a mesocosm approach

      Dilliplaine, Kyle B.; Gradinger, Rolf; Bluhm, Bodil; Collins, Eric; Eicken, Hajo (2017-05)
      The Arctic marine environment is facing increasing risks of oil spills due to growing maritime activities such as tourism and resource exploration. Encapsulation and migration of spilled oil through the brine channel system in sea ice poses significant risk to ice-associated biological communities. The first objective of this study was to establish mesocosms that allow the growth of artificial sea ice leading to sea ice physical properties similar to young natural sea ice. In addition, the mesocosms should be capable of growing and maintaining a sea ice community. Six sea water tanks with 360 l capacity each were inoculated with biological cultures collected from landfast sea ice near Utqiaġvik AK in April 2014 (year 1) and March 2015 (year 2). The two experiments lasted 24 and 27 days, and final ice thickness reached a mean value of 33 cm. The light conditions under the ice mimicked natural spring irradiances of 15 umol photons m² s⁻¹. Different inoculation approaches for ice biota were used. In year 1 we did not observe any algal growth. In year 2, biological characteristics in the ice prior to oil release (chlorophyll a, Extracellular Polymeric Substance (EPS) concentrations and algal and bacterial abundances) were similar to natural concentrations from early spring first year ice. The second objective was to evaluate the impact of Alaska North Slope crude oil on sea ice biota. Two different oil spill scenarios were tested in the mesocosms: discrete oil lenses and dispersed emulsions. Tanks were sampled prior to oil release and 13 or 10 days post-release in year 1 and year 2, respectively. In year 1, bacterial abundances increased after oil release, while establishment of algal populations was unsuccessful. In year 2, algal growth rates and EPS production increased over time in the control tanks, while they did not change in the oil exposed tanks. Differential response of bacteria and algae between year 1 and 2 not only point to the potential of nutrient competition, but also to the need of measuring several biological properties to detect effects of oil exposure in the event of a spill. Future studies can build upon the developed experimental framework including biological responses to low, sub-lethal oil dosing.
    • Effects of areas closed to bottom trawling on fish and invertebrate species in the eastern Bering Sea

      Frazier, Christine Ann; Norcross, Brenda; Hills, Sue; Norcorss, Brenda; Witherell, David (2003-12)
      The Bering Sea is a productive ecosystem with some of the most important fisheries in the United States. Constant commercial fishing for groundfish has occurred since the 1960s. The implementation of areas closed to bottom trawling to protect critical habitat for fish or crabs resulted in successful management of these fisheries. The efficacy of these closures on non-target species is unknown. This study determined if differences in abundance, biomass, diversity and evenness of dominant fish and invertebrate species occur among areas open and closed to bottom trawling in the eastern Bering Sea between 1996 and 2000. This study represented four areas: two within Bristol Bay closed areas and two within comparable fished areas. Total abundance and biomass were not significantly different among fished and closed areas or between pre-closure (1990-1994) and post-closure (1996-2000) years. Diversity and evenness were greater in fished areas than closed areas. The biomass of some functional feeding groups (i.e. piscivores, detritivores) of species decreased when compared among areas and in pre-closure versus post-closure years while others increased. These results support the need for continued research and monitoring of eastern Bering Sea closed areas to determine recovery time and the efficacy of closures as a management tool.
    • Effects of disturbance by clipping on two distinct forms of Zostera marina L.

      Roth, Joanna E. (1986-05)
      Biweekly clipping of leaves was used as a type of disturbance to compare the responses of eelgrass (Zostera marina) in shallow and deep water to those predicted from a terrestrial ecosystem succession model. All clipped plants had lower leaf growth rates than controls. Clipped plants decreased root-rhizome biomass in shallow water, but not in deep-water stands during 1981. During 1982 (better weather), shallow-water plants increased leaf carbon concentrations; deep-water plants decreased root-rhizome biomass. Root-rhizome to leaf ratios (high in shallow water and low in deep water) and weather conditions appeared important in determining the response to clipping. All plants had similar nitrogen content. These responses were typical of those reported for the tropical turtle grass, but were contrary to differences in plant growth strategies and nutrient use predicted from some terrestrial ecosystem studies of other higher vascular plants.
    • Effects of environmental characteristics on the fish assemblages of high latitude kelp forests in South-central Alaska

      Efird, Terril P.; Konar, Brenda; Seitz, Andrew; Stekoll, Michael (2013-12)
      Alaskan kelp forests are patchy habitats, varying greatly in size, physical complexity, and biotic and abiotic characteristics, and are important to fish communities. Patchy habitats often support different communities on patch edges versus interiors, while patch size and physical complexity are typically correlated to the resident community structure. This study quantified the biological and physical heterogeneity within different sized kelp forests and identified which factors are important in structuring the associated fish communities. Fish and habitat surveys were conducted at ten kelp forests of varying sizes. Significantly different fish communities were found at edge compared to interior locations. The relative abundance of seven species explained 91.4% of the variability in the fish community. Fish community structure was not correlated with kelp forest size or the species composition of canopy forming kelps. Instead, it related to the abundances of two understory kelps, bottom rugosity, and water depth. Together these benthic attributes correlated with 53.6% of the fish community variability. These findings suggest that within patchy systems that are spatially and structurally non-uniform, associated fish species composition and abundance may be more directly linked to location within the patch and year-round habitat complexity rather than habitat patch size or foundational species composition.
    • Effects Of Glacial Discharge On Kelp Bed Organisms In An Alaskan Subarctic Estuary

      Sparkland, Tania Marie; Iken, Katrin; Braddock, Joan; Gradinger, Rolf; Himelbloom, Brian; Konar, Brenda; Whitledge, Terry (2011)
      Global climate warming is having large-scale, pronounced effects on the physical environment of Arctic and subarctic nearshore marine ecosystems, such as the widespread melting of glaciers. The purpose of this study was to determine how changing environmental conditions due to glacial melting affect subarctic kelp bed community structure and organism fitness. This study compared kelp bed community structure under disparate environmental conditions on a glacially-influenced and an oceanic shore in the same subarctic Alaskan estuary. Laboratory tests assessed the effects of varying salinity and irradiance on growth and physiological competence (as maximum quantum yield ( Fv/Fm)) of the dominant kelp, Saccharina latissima. Reciprocal in situ shore transplant studies examined seasonal growth, Fv/Fm, morphology and storage product levels (mannitol) in S. latissima. This study showed that kelp communities were distinctly different in these two nearshore regions within the same subarctic estuary. In addition, the kelp S. latissima from these two environments, exhibited phenotypic plasticity in terms of growth to varying levels of salinity and light availability, while both populations maintained high physiological competence year-round. However, this phenotypic plasticity was constrained within different seasonal growth patterns in the populations from the two shores, which likely are genetically fixed. This is the first time that phenotypic plasticity within a genetically fixed seasonal growth cycle has been described for macroalgae and especially for two populations in such close proximity. However, the ability to elicit plastic responses and seasonal adaptations in S. latissima may be limited and concerns remain about the long-term persistence of this and other important foundation species and nearshore habitats with continued climate change.
    • Effects of ocean acidification on development of Alaskan crab larvae

      Descôteaux, Raphaëlle; Hardy, Sarah; Iken, Katrin; Mathis, Jeremy (2014-05)
      The oceans absorb a large proportion of the carbon dioxide gas (CO₂) emitted into the atmosphere. This CO₂ changes the chemistry of seawater to make it more acidic, a phenomenon termed ocean acidification. Ocean acidification can have negative impacts on marine fauna, especially during early life stages, presenting a risk to ecosystems and fisheries. This research tested the effects of ocean acidification on the larval development of three crab species in Alaska: Tanner crab (Chionoecetes bairdi), rock crab (Glebocarcinus oregonensis), and Dungeness crab (Metacarcinus magister). Experiments were undertaken to assess the effects of exposure to low-pH conditions (decrease of up to 0.6 pH units from current levels, range of pH ~8.1 to 7.5) on survival, growth (morphometrics and mass), and carapace mineral composition of larval Tanner, rock, and Dungeness crabs. Results showed a decrease in survival as well as a small but nonsignificant decrease in size of Tanner crabs. There was a small and complex effect of pH on survival of Dungeness crabs. Rock crabs raised in low-pH conditions (pH 7.5) had higher individual biomass than those raised in ambient conditions (pH 8.1). There was no significant impact of pH on mineralization of any species. Therefore, low pH had a negative effect on development of Tanner crabs, a small effect on Dungeness larval survival and no discernible negative effect on rock crab larvae. Differences in response to ocean acidification may be related to pre-adaptation to variable pH conditions through lifestyle such that species that live in deeper, more stable waters (e.g., Tanner crab) are more vulnerable than species living in shallower, more variable waters (e.g., rock and Dungeness crabs). These observations suggest that ocean acidification will have negative impacts on Tanner and Dungeness crab larval survival with potential implications for recruitment to the adult population and consequently, for their fisheries.
    • Effects of rising sea surface temperature and decreasing salinity on kelps and associated macroalgal communities

      Lind, Alyssa; Konar, Brenda; Danielson, Seth; Edwards, Matthew (2016-05)
      Kelp forests provide a multitude of vital ecosystems services, such as habitat for commercially and recreationally important species, support of complex food webs, and reduction of coastal erosion. The diversity and resilience of kelp forest communities are threatened as the severity of climate change and other anthropogenic stressors continues to mount. Particularly in the North Pacific, sea surface temperature (SST) is warming and glacier melt is discharging into coastal waters, causing decreases in salinity. This study assesses possible impacts of increasing SST and decreasing salinity on kelp forests by examining the response of key kelp species and their associated macroalgal community to these parameters in a North Pacific estuary, using Kachemak Bay as a model system. This two-part study combines both 1) a retrospective analysis of effects of environmental variables on existing kelp populations (Agarum clathratum, Laminaria yezoensis, and Saccharina latissima) and their associated macroalgal communities at three discreet water depths (5, 10 and 15 m), and 2) a factorial laboratory experiment investigating the effects of rising SST and decreasing salinity on kelp spore settlement and initial gametophyte growth in Eualaria fistulosa, Nereocystis luetkeana, and S. latissima. No strong correlations were observed between adult kelp biomass of any individual species with past SST and salinity changes, with the exception of a negative correlation between SST and L. yezoensis biomass at 10 m. In addition, SST and salinity were insignificant factors in shaping the associated macroalgal community biomass. In contrast to the retrospective analyses, the experimental results indicated that the early life-history stages of all kelp study species experienced decreased settlement and growth at elevated temperatures and decreased salinities. Eualaria fistulosa spores and gametophytes were the most negatively impacted, compared to the more widely distributed N. luetkeana and S. latissima. These results suggest that N. luetkeana and S. latissima are more likely to outperform E. fistulosa under projected conditions. By exploring how both early and late life-history stages of several key kelp species are impacted by dual stressors, this research enhances our understanding of how these species and their associated macroalgal communities will respond to projected changes in SST and salinity.
    • Effects of variable maternal diet conditions on the reproductive success and development of the California sea cucumber (Parastichopus californicus)

      Regula-Whitefield, Charlotte Marie; Hardy, Sarah Mincks; Oliveira, Alexandra; Iken, Katrin; Gradinger, Rolf; Hervey, H. Rodger (2016-12)
      Anthropogenic and natural climate change is altering the biology and ecology of marine organisms, which can be reflected in the supply of primary production that provides food for consumers. Primary producers differ in their biochemical composition, and marine food webs are thus based on specific combinations of producers that provide key nutrients such as dietary fatty acids (FA). Some FA cannot be synthesized by marine invertebrates, and must be acquired directly from diets. Reproductive processes in marine invertebrates are often timed to correspond with seasonal patterns in primary production, such that dietary FA and other nutrients can be partitioned to eggs to provide energy for cell division and biomolecules needed for membrane development. My dissertation investigates the consequences of changing patterns in primary production by examining the effects of maternal diet on reproductive fitness of a deposit feeder, and provides information to support the management and continued captive culturing of the commercially harvested Parastichopus californicus (California sea cucumbers). In chapter 1, I describe a novel live-spawning method and quantify basic reproductive parameters for P. californicus. Peak spawning in the Southeast AK population was about two months earlier and three times smaller than previously observed in British Columbia, Canada. Live-spawned captive females produced more viable eggs and strip-spawned females produced higher fecundity rates. These findings are relevant for the management of commercially harvested populations of P. californicus because they more accurately define spawning seasons, and provide a reliable method to spawn captive animals for further aquaculture development. In chapter 2, I present the results of feeding experiments that explore the effects of two mono-specific algal feeds with different FA profiles on female reproductive output and pre-feeding larval fitness. Females fed with the green alga Tetraselmis sp. had higher fecundity, but there was reduced larval survival relative to females that were fed the diatom Thalassiosira sp. Similar rates of larval development were recorded in both feed treatments. Significant differences were observed in the abundance of FA 20:5ɷ3 (EPA), 22:3ɷ6 (DHA), 12:0, 16:0, and 18:0 FAs in eggs and female gonads between the two feed treatments. In chapter 3, I used field collections in Southeast AK to assess temporal patterns feeding behavior and diet, and examined tissue-specific patterns in total lipid and FA storage and utilization, in in situ populations of P. californicus. All tissue ratios (percent of each tissue relative to the total body mass) varied significantly among collection dates. Tissue and gut content total lipid content also varied significantly among collection dates, except for muscle tissue. Shell debris and terrestrial debris were abundant in all guts regardless of collection date. FA composition differed significantly among females with different gonad maturation periods in skin, viscera, and gonads, suggesting the use of lipids stored in skin and viscera for gonad development. These results further the understanding of dietary factors affecting reproductive fitness in deposit feeders by demonstrating the importance of diet and lipid storage to gonad development.