RSS 1.0University of Alaska Southeast
Sub-communities within this community
-
Evening at Egan
Annual UAS Fall Semester Lecture Series -
One Campus, One Book
One Campus, One Book is the common reading program at UAS-Juneau. -
Writing Center
The Writing Center advises students from all disciplines on writing projects.
Recent Submissions
-
Evolution of marine organisms under climate change at different levels of biological organisation.Research to date has suggested that both individual marine species and ecological processes are expected to exhibit diverse responses to the environmental effects of climate change. Evolutionary responses can occur on rapid (ecological) timescales, and yet studies typically do not consider the role that adaptive evolution will play in modulating biological responses to climate change. Investigations into such responses have typically been focused at particular biological levels (e.g., cellular, population, community), often lacking interactions among levels. Since all levels of biological organisation are sensitive to global climate change, there is a need to elucidate how different processes and hierarchical interactions will influence species fitness. Therefore, predicting the responses of communities and populations to global change will require multidisciplinary efforts across multiple levels of hierarchy, from the genetic and cellular to communities and ecosystems. Eventually, this may allow us to establish the role that acclimatisation and adaptation will play in determining marine community structures in future scenarios.
-
Seawater acidification more than warming presents a challenge for two Antarctic macroalgal-associated amphipodsElevated atmospheric pCO2 concentrations are triggering seawater pH reductions and seawater temperature increases along the western Antarctic Peninsula (WAP). These factors in combination have the potential to influence organisms in an antagonistic, additive, or synergistic manner. The amphipods Gondogeneia antarctica and Paradexamine fissicauda represent prominent members of macroalgal-associated mesograzer assemblages of the WAP. Our primary objective was to investigate amphipod behavioral and physiological responses to reduced seawater pH and elevated temperature to evaluate potential cascading ecological impacts. For 90 d, amphipods were exposed to combinations of seawater conditions based on present ambient (pH 8.0, 1.5°C) and predicted end-of-century conditions (pH 7.6, 3.5°C). We recorded survival, molt frequency, and macroalgal consumption rates as well as change in wet mass and proximate body composition (protein and lipid). Survival for both species declined significantly at reduced pH and co-varied with molt frequency. Consumption rates in G. antarctica were significantly higher at reduced pH and there was an additive pH−temperature effect on consumption rates in P. fissicauda. Body mass was reduced for G. antarctica at elevated temperature, but there was no significant effect of pH or temperature on body mass in P. fissicauda. Exposure to the pH or temperature levels tested did not induce significant changes in whole body biochemical composition of G. antarctica, but exposure to elevated temperature resulted in a significant increase in whole body protein content of P. fissicauda. Our study indicates that while elevated temperature causes sub-lethal impacts on both species of amphipods, reduced pH causes significant mortality.
-
Ocean warming and acidification alter Antarctic macroalgal biochemical composition but not amphipod grazer feeding preferencesIncreased anthropogenic atmospheric CO2 concentrations have resulted in ocean warming and alterations in ocean carbonate chemistry, decreasing seawater pH (ocean acidification). The combination of ocean warming and acidification (OWA) may alter trophic interactions in marine benthic communities along the western Antarctic Peninsula (WAP). Abundant and diverse macroalgae–grazer assemblages, dominated by macroalgae (e.g. chemically defended Desmarestia anceps and D. menziesii) and gammarid amphipods (e.g. Gondogeneia antarctica), occur on the nearshore benthos along the WAP. In the present study, the amphipod G. antarctica and macroalgae D. anceps and D. menziesii were exposed for 39 and 79 d, respectively, to combinations of current and predicted near-future temperature (1.5 and 3.5°C, respectively) and pH (8.0 and 7.6, respectively). Protein and lipid levels of macroalgal tissues were quantified, and 5-way choice amphipod feeding assays were performed with lyophilized macroalgal tissues collected at time zero and following exposure to the 4 temperature-pH treatments. For D. anceps, we found a significant interactive temperature-pH effect on lipid levels and significantly lower protein levels at reduced pH. In contrast, tissues of D. menziesii exhibited significantly greater lipid levels after exposure to reduced pH, but there was no temperature effect on lipid or protein levels. Despite shifts in macroalgal biochemical composition, there were no changes in amphipod feeding preferences. Our results indicate that despite altered macroalgal nutritional quality under OWA, both macroalgae retained their ability to deter amphipod feeding. This deterrent capacity could become an important contributor to net community resistance of macroalgae−mesograzer assemblages of the WAP to predicted OWA.
-
Trophic Transfer of Macroalgal Fatty Acids in Two Urchin Species: Digestion, Egestion, and Tissue BuildingSea urchins are ecosystem engineers of nearshore benthic communities because of their influence on the abundance and distribution of macroalgal species. Urchins are notoriously inefficient in assimilation of their macroalgal diets, so their fecal production can provide a nutritional subsidy to benthic consumers that cannot capture and handle large macroalgae. We studied the assimilation of macroalgal diets by urchins by analyzing the profiles of trophic biomarkers such as fatty acids (FAs). We tracked macroalgal diet assimilation in both Strongylocentrotus droebachiensis and S. purpuratus. Juvenile S. droebachiensis and adult S. purpuratus were maintained for 180 and 70 days, respectively, on one of three monoculture diets from three algal phyla: Nereocystis luetkeana, Pyropia sp., or Ulva sp. We then analyzed FA profiles of the macroalgal tissue fed to urchins as well as urchin gonad, gut, digesta, and egesta (feces) to directly evaluate trophic modification and compare nutritional quality of urchin food sources, urchin tissues, and fecal subsidies. In the S. purpuratus assay, there were significantly more total lipids in the digesta and egesta than in the algae consumed. The FA profiles of urchin tissues differed among urchin species, all diets, and tissue types. Despite these differences, we observed similar patterns in the relationships between the urchin and macroalgal tissues for both species. Egesta produced by urchins fed each of the three diets were depleted with respect to the concentration of important long chain polyunsaturated fatty acids (LCPUFAs), but did not differ significantly from the source alga consumed. Both urchin species were shown to synthesize and selectively retain both the precursor and resulting LCPUFAs involved in the synthesis of the LCPUFAs 20:4ω6 and 20:5ω3. S. droebachiensis and S. purpuratus exhibited consistent patterns in the respective depletion and retention of precursor FAs and resulting LCPUFAs of Pyropia and Ulva tissues, suggesting species level control of macroalgal digestion or differential tissue processing by gut microbiota. For both S. droebachiensis and S. purpuratus, macroalgal diet was a surprisingly strong driver of urchin tissue fatty acids; this indicates the potential of fatty acids for future quantitative trophic estimates of urchin assimilation of algal phyla in natural settings.
-
The Purple Sea Urchin Strongylocentrotus purpuratus Demonstrates a Compartmentalization of Gut Bacterial Microbiota, Predictive Functional Attributes, and Taxonomic Co-OccurrenceThe sea urchin Strongylocentrotus purpuratus (order Camarodonta, family Strongylocentrotidae) can be found dominating low intertidal pool biomass on the southern coast of Oregon, USA. In this case study, three adult sea urchins were collected from their shared intertidal pool, and the bacteriome of their pharynx, gut tissue, and gut digesta, including their tide pool water and algae, was determined using targeted high-throughput sequencing (HTS) of the 16S rRNA genes and bioinformatics tools. Overall, the gut tissue demonstrated Arcobacter and Sulfurimonas (Epsilonproteobacteria) to be abundant, whereas the gut digesta was dominated by Psychromonas (Gammaproteobacteria), Propionigenium (Fusobacteria), and Flavobacteriales (Bacteroidetes). Alpha and beta diversity analyses indicated low species richness and distinct microbial communities comprising the gut tissue and digesta, while the pharynx tissue had higher richness, more closely resembling the water microbiota. Predicted functional profiles showed Kyoto Encyclopedia of Genes and Genomes (KEGG) Level-2 categories of energy metabolism, membrane transport, cell motility, and signal transduction in the gut tissue, and the gut digesta represented amino acid, carbohydrate, vitamin and cofactor metabolisms, and replication and repair. Co-occurrence network analysis showed the potential relationships and key taxa, such as the highly abundant Arcobacter and Propionigenium, influencing population patterns and taxonomic organization between the gut tissue and digesta. These results demonstrate a trend of microbial community integration, allocation, predicted metabolic roles, and taxonomic co-occurrence patterns in the S. purpuratus gut ecosystem.
-
Eelgrass pathogen Labyrinthula zosterae synthesizes essential fatty acidsNegative consequences of parasites and disease on hosts are usually better understood than their multifaceted ecosystem effects. The pathogen Labyrinthula zosterae (Lz) causes eelgrass wasting disease but has relatives that produce large quantities of nutritionally valuable long-chain polyunsaturated fatty acids (LCPUFA) such as docosahexaenoic acid (DHA). Here we quantify the fatty acids (FA) of Lz cultured on artificial media, eelgrass-based media, and eelgrass segments to investigate whether Lz may similarly produce LCPUFA. We also assess whether fieldcollected lesions show similar FA patterns to laboratory-inoculated eelgrass. We find that Lz produces DHA as its dominant FA along with other essential FA on both artificial and eelgrass-based media. DHA content was greater in both laboratory-inoculated and field-collected diseased eelgrass relative to their respective controls. If Lz’s production scales in situ, it may present an unrecognized source of LCPUFA in eelgrass ecosystems.
-
Ghost Factors of Laboratory Carbonate Chemistry Are Haunting Our ExperimentsFor many historical and contemporary experimental studies in marine biology, seawater carbonate chemistry remains a ghost factor, an uncontrolled, unmeasured, and often dynamic variable affecting experimental organisms or the treatments to which investigators subject them. We highlight how environmental variability, such as seasonal upwelling and biological respiration, drive variation in seawater carbonate chemistry that can influence laboratory experiments in unintended ways and introduce a signal consistent with ocean acidification. As the impacts of carbonate chemistry on biochemical pathways that underlie growth, development, reproduction, and behavior become better understood, the hidden effects of this previously overlooked variable need to be acknowledged. Here we bring this emerging challenge to the attention of the wider community of experimental biologists who rely on access to organisms and water from marine and estuarine laboratories and who may benefit from explicit considerations of a growing literature on the pervasive effects of aquatic carbonate chemistry changes.
-
Granular decoherence precedes ice mélange failure and glacier calving at Jakobshavn IsbræThe stability of the world’s largest glaciers and ice sheets depends on mechanical and thermodynamic processes occurring at the glacier–ocean boundary. A buoyant agglomeration of icebergs and sea ice, referred to as ice mélange, often forms along this boundary and has been postulated to affect ice-sheet mass losses by inhibiting iceberg calving. Here, we use terrestrial radar data sampled every 3 min to show that calving events at Jakobshavn Isbræ, Greenland, are preceded by a loss of flow coherence in the proglacial ice mélange by up to an hour, wherein individual icebergs flowing in unison undergo random displacements. A particle dynamics model indicates that these fluctuations are likely due to buckling and rearrangements of the quasi-two-dimensional material. Our results directly implicate ice mélange as a mechanical inhibitor of iceberg calving and further demonstrate the potential for real-time detection of failure in other geophysical granular materials.
-
Integral functions of marine vertebrates in the ocean carbon cycle and climate change mitigationIn the last decade, the ocean has absorbed a quarter of the Earth’s greenhouse gas emissions through the carbon (C) cycle, a naturally occurring process. Aspects of the ocean C cycle are now being incorporated into climate change mitigation and adaptation plans. Currently, too little is known about marine vertebrate C functions for their inclusion in policies. Fortunately, marine vertebrate biology, behavior, and ecology through the lens of C and nutrient cycling and flux is an emerging area of research that is rich in existing data. This review uses literature and trusted data sources to describe marine vertebrate C interactions, provides quantification where possible, and highlights knowledge gaps. Implications of better understanding the integral functions of marine vertebrates in the ocean C cycle include the need for consideration of these functions both in policies on nature-based climate change mitigation and adaptation, and in management of marine vertebrate populations.
-
Assessing the Behavioural Responses of Small Cetaceans to Unmanned Aerial VehiclesUnmanned Aerial Vehicles (UAVs), or drones, have recently emerged as a relatively affordable and accessible method for studying wildlife. Vertical Take-off and Landing (VTOL) UAVs are appropriate for morphometric, behavioural, abundance and demographic studies of marine mammals, providing a stable, nonintrusive and highly manoeuvrable platform. Previous studies using VTOL UAVs have been conducted on various marine mammal species, but specific studies regarding behavioural responses to these devices are limited and scarce. The aim of this study was to evaluate the immediate behavioural responses of common (Delphinus delphis) and bottlenose (Tursiops truncatus) dolphins to a VTOL UAV flown at different altitudes. A multirotor (quadcopter) UAV with an attached GoPro camera was used. Once a dolphin group was located, the UAV was flown at a starting height of 50 m directly above the group, subsequently descending 5 m every 30 s until reaching 5 m. We assessed three behavioural responses to a VTOL UAV at different heights: (i) direction changes, (ii) swimming speed and (iii) diving. Responses by D. delphis (n = 15) and T. truncatus (n = 10) groups were analysed separately. There were no significant responses of T. truncatus to any of the studied variables. For D. delphis, however, there were statistically significant changes in direction when the UAV was flown at a height of 5 m. Our results indicate that UAVs do not induce immediate behavioural responses in common or bottlenose dolphins when flown at heights > 5 m, demonstrating that the use of VTOL UAVs to study dolphins has minimal impact on the animals. However, we advise the use of the precautionary principle when interpreting these results as characteristics of this study site (e.g., high whale-watching activity) may have habituated dolphins to anthropogenic disturbance.
-
Tidewater glacier response to individual calving eventsTidewater glaciers have been observed to experience instantaneous, stepwise increases in velocity during iceberg-calving events due to a loss of resistive stresses. These changes in stress can potentially impact tidewater glacier stability by promoting additional calving and affecting the viscous delivery of ice to the terminus. Using flow models and perturbation theory, we demonstrate that calving events and subsequent terminus readvance produce quasi-periodic, sawtooth oscillations in stress that originate at the terminus and propagate upstream. The stress perturbations travel at speeds much greater than the glacier velocities and, for laterally resisted glaciers, rapidly decay within a few ice thickness of the terminus. Consequently, because terminus fluctuations due to individual calving events tend to be much higher frequency than climate variations, individual calving events have little direct impact on the viscous delivery of ice to the terminus. This suggests that the primary mechanism by which calving events can trigger instability is by causing fluctuations in stress that weaken the ice and lead to additional calving and sustained terminus retreat. Our results further demonstrate a stronger response to calving events in simulations that include the full stress tensor, highlighting the importance of accounting for higher order stresses when developing calving parameterizations.
