We compared four metabolic indicators of nutritional state: citrate synthase activity (CS), malate dehydrogenase activity (MDH), lactate dehydrogenase activity (LDH) and percent body protein to each other and to respiration measurements. These comparisons were made for four species of copepods (Calanoides acutus, Metridia gerlachei, Paraeuchaeta antarctica and another form of Paraeuchaeta that was unidentifiable to species due to its early life stage), three species of Euphausids (Euphausia crystallorophias, Euphausia triacantha, Euphausia superba (including both F6-furcilial and adult stages)) and Thysonessa macrura which were collected off the Western Antarctic Peninsula (WAP) during Spring/Summer and Fall/Winter. Most species showed significant changes in one or more of the enzyme activities. In general, species that engage diapause during the Winter months showed a decrease in citrate synthase whereas those that actively feed throughout the year showed no significant changes. There was also evidence of correlations between citrate synthase activity and respiration as well as between malate dehydrogenase activity and respiration. The observed patterns are consistent with existing models of survival strategy for these Antarctic species.

The Southern Ocean is home to two major types of fishes: endemics in the suborder Notothenioidii and representatives of oceanic fish families that are widely distributed in the midwater and benthic environments elsewhere (e.g. bathylagids, myctophids, liparids, and zoarcids) In most regions of the coastal Antarctic, e.g. the Ross Sea, there is a distinct separation in the pelagic communities at the shelf break between the oceanics (off-shelf) and the endemics (on-shelf). Coincidentally, in much of the coastal Antarctic, the shelf break also marks the boundary between a water column entirely composed of the very cold (-2°C ) Ice Shelf Water and an oceanic profile that includes warmer Circumpolar Deep Water (2°C at 200 m) at intermediate depths. The distinct separation in pelagic communities observed in most coastal regions of the Antarctic is not seen on the western Antarctic Peninsula (WAP), where circumpolar deep water intrudes to form a warmer midwater and oceanic species are strongly represented. It was hypothesized that the cold ice-shelf water, lethal to fishes without antifreeze glycoproteins (AFGP's) in their blood, was excluding the oceanic species from most of the Antarctic continental shelf waters. To test the hypothesis, nine species of fish captured in WAP shelf waters were tested for the presence of AFGP's. The oceanic fish families analyzed: Myctophidae (Electrona and Gymnoscopelus), Zoarcidae (Melanostigma), Gempylidae (Paradiplospinus), Paralepididae (Notolepsis), and Bathylagidae (Bathylagus) showed no antifreeze activity. Two endemic species captured in the same sampling program did show antifreeze activity: the important pelagic species Pleuragramma antarcticum (Nototheniidae) and the Bathydraconid (Vomeridens). The absence of AFGP's in the blood of Antarctic oceanic species makes a strong case for temperature exclusion of oceanic fishes in the coastal Antarctic.

Graduation date: 2006 / Presented on 2005-12-02 / An empirical statistical model is developed that relates the non-tidal motion of the ocean surface currents off the Oregon coast to forecasts of the coastal winds. The empirical statistical model is then used to produce predictions of the surface currents that are evaluated for their agreement with measured currents. Measurements of the ocean surface currents were made at 6 km resolution using Long-Range CODAR SeaSonde high-frequency (HF) surface current mappers and wind forecasts were provided at 12 km resolution by the North American Mesoscale (NAM) model. First, the response of the surface currents to wind-forcing measured by five coastal National Data Buoy Center (NDBC) stations was evaluated using empirical orthogonal function (EOF) analysis. A significant correlation of approximately 0.8 was found between the majority of the variability in the seasonal anomalies of the low-pass filtered surface currents and the seasonal anomalies of the low-pass filtered wind stress measurements. The U and the V components of the measured surface currents were both shown to be forced by the zonal and meridional components of the wind-stress at the NDBC stations. Next, the NAM wind forecasts were tested for agreement with the measurements of the wind at the NDBC stations. Significant correlations of around 0.8 for meridional wind stress and 0.6 for zonal wind stress were found between the seasonal anomalies of the low-pass filtered wind stress measured by the NDBC stations and the seasonal anomalies of the low-pass filtered wind stress forecast by the NAM model. Given the amount of the variance in the winds captured by the NAM model and the response of the ocean surface currents to both components of the wind, bilinear regressions were formed relating the seasonal anomalies of the low-pass filtered NAM forecasts to the seasonal anomalies of the low-pass filtered surface currents. The regressions turned NAM wind forecasts into predictions of the seasonal anomalies of the low-pass filtered surface currents. Calculations of the seasonal cycle in the surface currents, added to these predicted seasonal anomalies, produced a non-tidal estimation of the surface currents that allowed a residual difference to be calculated from recent surface current measurements. The sum of the seasonal anomalies, the seasonal cycle, and the residual formed a prediction of the non-tidal surface currents. The average error in this prediction of the surface currents off the Oregon coast remained less than 4 cm/s out through 48 hours into the future.