Browsing by Subject "Chukchi Sea"
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Item Abundance, biomass and caloric content of Chukchi Sea bivalves and influence on Pacific walrus (Odobenus rosmarus divergens) abundance and distribution in the northeastern Chukchi Sea(2015-05) Young, Jordann Kailey; Dunton, Kenneth H.; Black, Bryan A.; Hardison, Amber KThe northeastern Chukchi Sea is a shallow subarctic shelf ecosystem that supports a significant benthic infaunal community. Bivalves are one of the dominant benthic taxa in this region, and represent a vital food resource for consumers such as Pacific walrus (Odobenus rosmarus divergens). The biomass, abundance and species composition of these bivalve communities not only reflect local patterns of productivity, but have the potential to affect upper trophic level consumers through bottom-up processes. Ten dominant bivalve taxa were collected over four cruises in the northeastern Chukchi Sea from 2009-2013 to establish baseline parameters in size frequency distributions, abundance, biomass and caloric content and to quantify their influence on the distribution of Pacific walrus. Pooled size-frequency distributions across all years showed strongly right-skewed distributions for most taxa, with a few showing evidence of a bimodal distribution. Calorimetric measurements revealed significant differences in caloric density between taxa (p-value < 0.001), and whole animal wet weight was a reliable predictor of caloric content. Abundance and biomass were largely dominated by calorie-dense, deposit-feeding species, including Macoma spp., Ennucula tenuis, Nuculana spp. and Yoldia spp.. Hotspot analysis revealed areas of high abundance, biomass and calories centered on and to the southeast of Hanna Shoal. Pacific walrus abundance from June through October was generally greatest in areas of high bivalve abundance and biomass. ANOVA analysis showed significant differences in mean caloric values between areas with and without walrus present (student’s t-test, p-value < 0.001), as well as between areas with low and high densities of walrus in the pooled annual dataset and in each individual month except October. The dominant bivalve taxa in this study were high-calorie deposit feeders which preferentially consume food sources that are likely to be affected by shifting sea ice dynamics, such as benthic microalgae and sea ice algae. As such, shifting sea ice dynamics have the potential to dramatically alter bivalve communities in the northeastern Chukchi Sea that may have profound implications for upper trophic levels.Item Chukchi Sea environmental data management in a relational database(2013-05) Yang, Fengyan; Maidment, David R.Environmental data hold important information regarding humanity’s past, present, and future, and are managed in various ways. The database structure most commonly used in contemporary applications is the relational database. Its usage in the scientific world for managing environmental data is not as popular as in businesses enterprises. Attention is caught by the diverse nature and rapidly growing volume of environmental data that has been increasing substantially in recent. Environmental data for the Chukchi Sea, with its embedded potential oil resources, have become important for characterizing the physical, chemical, and biological environment. Substantive data have been collected recently by researchers from the Chukchi Sea Offshore Monitoring in the Drilling Area: Chemical and Benthos (COMIDA CAB) project. A modified Observations Data Model was employed for storing, retrieving, visualizing and sharing data. Throughout the project-based study, the processes of environmental data heterogeneity reconciliation and relational database model modification and implementation were carried out. Data were transformed into shareable information, which improves data interoperability between different software applications (e.g. ArcGIS and SQL server). The results confirm the feasibility and extendibility of employing relational databases for environmental data management.Item The Long Tail of hydroinformatics : implementing biological and oceanographic information in hydrologic information systems(2012-12) Hersh, Eric Scott; Maidment, David R.; Bonner, Timothy; Dunton, Kenneth; Gilbert, Robert; Hodges, Ben; McKinney, DaeneHydrologic Information Systems (HIS) have emerged as a means to organize, share, and synthesize water data. This work extends current HIS capabilities by providing additional capacity and flexibility for marine physical and chemical observations data and for freshwater and marine biological observations data. These goals are accomplished in two broad and disparate case studies – an HIS implementation for the oceanographic domain as applied to the offshore environment of the Chukchi Sea, a region of the Alaskan Arctic, and a separate HIS implementation for the aquatic biology and environmental flows domains as applied to Texas rivers. These case studies led to the development of a new four-dimensional data cube to accommodate biological observations data with axes of space, time, species, and trait, a new data model for biological observations, an expanded ontology and data dictionary for biological taxa and traits, and an expanded chain-of-custody approach for improved data source tracking. A large number of small studies across a wide range of disciplines comprise the “Long Tail” of science. This work builds upon the successes of the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) by applying HIS technologies to two new Long Tail disciplines: aquatic biology and oceanography. In this regard this research improves our understanding of how to deal with collections of biological data stored alongside sensor-based physical data. Based on the results of these case studies, a common framework for water information management for terrestrial and marine systems has emerged which consists of Hydrologic Information Systems for observations data, Geographic Information Systems for geographic data, and Digital Libraries for documents and other digital assets. It is envisioned that the next generation of HIS will be comprised of these three components and will thus actually be a Water Information System of Systems.Item Trophodynamics of the benthic food webs in the Chukchi and Beaufort Seas, Alaska(2013-12) McTigue, Nathan David; Dunton, Kenneth H.The Chukchi and Beaufort Sea shelves host diverse and productive seafloor ecosystems important for carbon and nitrogen cycling for the Arctic Ocean. The benthic food web transfers energy from primary producers to high trophic level organisms (e.g., birds, fish, and mammals), which are important for cultural practices and subsistence hunting by Native Alaskans. This work focuses on the trophic ecology of arctic food webs through use of several different approaches. First, variation in the natural abundance of stable carbon and nitrogen isotopes facilitated the identification of trophic pathways and, subsequently, allowed the comparison of trophic guilds and food webs from the Chukchi and Beaufort Seas. Compared to water column and sedimentary organic matter end-members, second trophic level grazers and suspension feeders were conspicuously ¹³C-enriched throughout the Chukchi Sea, which supports the hypothesis that microbial degradation of organic matter occurred prior to metazoan assimilation. Second, food web recovery from disturbances caused by exploratory oil drilling at the seafloor that had occurred approximately 20 years prior were assessed in both the Chukchi and Beaufort Seas. Based on isotopic trophic niche overlap between organisms common to drilled and reference sites in the Chukchi and Beaufort Seas, the oil drilling sites had similar food web structure, indicating recovery from the activity associated with the drilling process. Third, photosynthetic pigment biomarkers were used to better understand the diagenetic process, specifically focusing on how both microbial and metazoan grazing pathways degrade organic matter in relation to seasonal sea ice retreat in the Chukchi Sea. The benthic macrofaunal and microbial food web caused rapid degradation of organic matter upon the initial pulse of microalgal food sources to the seafloor. These diagenetic pathways are linked to the ¹³C-enrichment of residual organic matter, which corresponds to the stable isotope values measured in the benthic macrofauna. Lastly, high-precision liquid chromatography and spectrophotometry were compared for estimating sedimentary pigments in the marine environment. Substantial differences in pheopigment (chlorophyll degradation products) concentrations were observed between the two techniques, suggesting the need for revisions to the monochromatic spectrophotometric equation that relates absorbance to pigment concentrations. One pheopigment, pheophorbide, was found to interfere with the accuracy of the spectrophotometric equation and caused the overestimation of pheopigments.