College of Fisheries and Ocean Sciences (CFOS)
The College of Fisheries and Ocean Sciences (CFOS) at the University of Alaska Fairbanks is a world-class marine research and teaching organization focusing on marine and freshwater fisheries, oceanography, marine biology, and community outreach. As Alaska’s university marine science institution, CFOS is uniquely positioned to help the citizens of Alaska understand our varied and changing marine and freshwater ecosystems and coastal resources on which so many depend.
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Theses and dissertations are in the following Graduate School collections
Sub-communities within this community
Evaluating the Accuracy of Unmanned Aerial Systems to Quantify Glacial Ice Habitats of Harbor Seals in AlaskaLong-term monitoring programs to evaluate climate-driven changes to tidewater glaciers, an important habitat for harbor seals (Phoca vitulina) in Alaska, are primarily carried out by costly, weather-dependent aerial surveys from fixed-winged aircraft. Unmanned aerial systems (UAS) can be an alternative cost-effective solution for gathering image data to quantify, monitor, and manage these habitats. However, there is a paucity of information related to the accuracy of using imagery collected by UAS for purposes of measuring floating icebergs. We evaluated the accuracy of using a UAS with a built-in 20 megapixel (MP) camera as well as a consumer-grade digital 16 MP camera to capture images of floating and stationary icebergs for the purpose of collecting vertical height measurements. Images (n=869) were captured of simulated icebergs (Cuboidal foam boxes) “Cb” (n=5) and real icebergs (n=5) that were either grounded or floating. The mean error ratios obtained were less than 10% and derived by comparing the mean calculated measurements of heights of Cb obtained from images captured by UAS with the physical measured heights of these Cb. The mean error ratio for height measurements of grounded icebergs (n=4) and one floating iceberg was also less than 10%. Within an object-image distance range of 6-25 m, the cameras captured images that were suitable to accurately calculate the heights of floating and grounded objects, and drift or uncontrolled movement of the UAS caused by wind or temporary loss of GPS did not appear to have any significant effects on measurement error. Our study provides substantial evidence of the high accuracy associated with using images captured by UAS for measuring dimensions of structures positioned on water and land surfaces. Ultimately, accurate surveys of glacial ice used by harbor seals will improve our understanding about the role of decreasing habitat in explaining population variability between different tidewater glaciers.
Carbon and nitrogen assimilation in the Bering Sea clams Nuculana radiata and Macoma moestaWe analyzed bulk carbon and nitrogen stable isotope values (delta C-13 and delta N-15) of the benthic clams Nuculana radiata and Macoma moesta from the Bering Sea during controlled feeding experiments (spring of 2009 and 2010) using isotopically labeled sea ice algae. The aim was to determine the ability of these clam species to assimilate carbon and nitrogen from sea ice algae. Specimens were collected in the Bering Sea and placed into jars without sediment (2009, N. radiata only) or into natural sediment cores (2010, both species). The clams were offered isotopically enriched (both C and N) or non-enriched algal feeds for time periods of 42 (2009) and 18 d (2010). Isotopic assimilation rates for carbon and nitrogen were calculated using the change in the isotope ratios of the clams over the experimental time. N. radiata in the jar experiments had slow isotopic assimilation rates (0.01 to 0.23 parts per thousand d(-1)), with solvent-extractable organic matter/lipids taking up both of the isotope markers fastest and muscle tissue the slowest. Lipids may thus be particularly suitable to track the immediate ingestion of sea ice algal production in benthic consumers. M. moesta showed 30% higher isotopic assimilation compared to N. radiata in sediment cores, likely reflecting the different feeding behaviors of these two species. Based on our results, N. radiata is likely better able to utilize food sources buried in the sediment and may be more competitive over the sediment surface feeding M. moesta under conditions of reduced ice algal production in the northern Bering Sea. (C) 2012 Elsevier B.V. All rights reserved.
CARBON AND NITROGEN ASSIMILATION IN THE CLAMS NUCULANA RADIATA AND MACOMA MOESTA FROM THE BERING SEAThe predicted climate-induced reduction in sea ice presence in the Bering Sea could impact benthic trophic interactions; however, species-specific consumer dependence on ice algal production is largely unknown. My objective was to track feeding in the benthic clams, Nuculana radiata and Macoma moesta, using stable carbon and nitrogen isotopes. Nuculana radiata had slow isotopic assimilation rates, with lipids taking up isotope markers fastest and muscle tissue the slowest. Lipids may thus be particularly suitable to track the immediate ingestion of sea ice algal export in benthic consumers. When isotopically enriched food was added to natural sediment cores, N. radiata assimilated 60% less of the isotope markers than when feeding on algal food in isolation. Possibly, this difference is related to the ingestion of other, naturally present food sources in the sediment. Macoma moesta showed 30% higher isotopic assimilation compared to N. radiata in sediment cores. I suggest that differing feeding behaviors between the species provide differential access to the sedimented algal food. Based on these results, N. radiata is likely better able to utilize food sources buried in the sediment and may be more competitive over M. moesta under conditions of reduced ice algal production in the northern Bering Sea.