Elizabeth Ross Hooge | Geology Reports

USGS2007

Oceanography of Glacier Bay, Alaska: Implications for biological patterns in a glacial fjord estuary

Alaska, U.S.A, is one of the few remaining locations in the world that has fjords that contain temperate idewater glaciers. Studying such estuarine systems provides vital information on how deglaciation affects oceanographic onditions of fjords and surrounding coastal waters. The oceanographic system of Glacier Bay, Alaska, is of particular interest ue to the rapid deglaciation of the Bay and the resulting changes in the estuarine environment, the relatively high oncentrations of marine mammals, seabirds, fishes, and invertebrates, and the Bay’s status as a national park, where ommercial fisheries are being phased out. We describe the first comprehensive broad-scale analysis of physical and iological oceanographic conditions within Glacier Bay based on CTD measurements at 24 stations from 1993 to 2002. easonal patterns of near-surface salinity, temperature, stratification, turbidity, and euphotic depth suggest that freshwater nput was highest in summer, emphasizing the critical role of glacier and snowmelt to this system. Strong and persistent tratification of surface waters driven by freshwater input occurred from spring through fall. After accounting for seasonal nd spatial variation, several of the external physical factors (i.e., air temperature, precipitation, day length) explained a large mount of variation in the physical properties of the surface waters. Spatial patterns of phytoplankton biomass varied hroughout the year and were related to stratification levels, euphotic depth, and day length. We observed hydrographic atterns indicative of strong competing forces influencing water column stability within Glacier Bay: high levels of freshwater ischarge promoted stratification in the upper fjord, while strong tidal currents over the Bay’s shallow entrance sill enhanced ertical mixing. Where these two processes met in the central deep basins there were optimal conditions of intermediate tratification, higher light levels, and potential nutrient renewal. These conditions were associated with high and sustained hlorophyll a levels observed from spring through fall in these zones of the Bay and provide a framework for understanding he abundance patterns of higher trophic levels within this estuarine system.

Estuaries and Coasts↗

USGS2003

Living on the edge: Distribution of Dungeness crab Cancer magister in a recently deglaciated fjord

Glacier Bay, Alaska, has supported a productive Dungeness crab fishery, although the area where the fishery occurred was small relative to the remainder of the Bay. We hypothesized that 1 or more abiotic limiting factors prevented crabs from surviving in the upper Bay. We tested this hypothesis by systematically sampling for relative abundance of Dungeness crabs from the mouth to the head of the Bay. We measured salinity, temperature and turbidity at each of the sampling sites and at permanent stations to characterize the habitat within and among years. We expected to find a completely truncated spatial distribution. Instead, we found that adult Dungeness crabs can survive in habitats heavily influenced by tidewater glaciers. There were significantly fewer crabs in the upper Bay and a sharp decrease in abundance around 40 km from the mouth of the Bay. The region of the Bay beyond 40 km from the mouth had a very low density of predominately adult male crabs. The narrow size frequency distribution and the lack of small crabs is consistent with poor survival in one of the pre-adult life stages in the upper Bay.

Alaska↗

USGS1995

Census methodologies of Black-legged Kittiwakes in Glacier Bay National Park

Black-legged Kittiwakes ( Rissa tridactyla ) have recently experienced widespread population declines and frequent colony failures throughout the North Pacific. At Glacier Bay National Park, the Margerie Glacier colony was censused visually in 1991 through 1993. In 1993 a new photographic census technique was also tested to assess its feasibility, accuracy, and ease of use, Three years of monitoring data indicate that kittiwake population size declined by about 10% over the three-year period, and that there were near-total colony reproductive failures in 1991 and 1992. Compared to visual colony counts made from a skiff, counting adult kittiwakes from projected 35-mm slides proved to be both more efficient and equally accurate.

Alaska↗