An airborne tunable diode laser instrument is described that is capable of operating in two measurement modes. One mode provides high precision (0.1 percent CH4; 1 percent CO) measurements of CH4 and CO with a 5 second response time, and a second mode achieves the very fast response time ( 60 msec) that is necessary to make airborne eddy correlation flux measurements. Examples of data from atmospheric expeditions of the Global Tropospheric Experiment are presented.

Abstract.Based

Seawater adaptation of 1- and 2-yr-old Atlantic salmon, Salmo salar, presmolts and smolts was assessed during exposure to salinity increasing from 0.1 to 31‰ by examining changes in the osmotic concentration of their serum, urine, and intestinal fluid. Both age-classes adapted to seawater equally well; the marine osmoregulatory mechanisms apparently function before completion of parr–smolt transformation. Adaptation was possible during the parr stage for fish exceeding 12–13 cm fork length. The timing of transformation was synchronous for 1- and 2-yr-old juveniles as demonstrated by changes in their lipid and moisture content and condition factor (K). Condition factor of juveniles at the Mactaquac Hatchery, New Brunswick (45°58′N), decreased from February until the second half of May, while lipid content decreased from February until the second half of June. Migratory activity of juveniles at this location was maximal during the second half of May coincident with attainment of minimum K values and decreased during the first half of June as K values increased. While timing of changes in lipid and moisture content and K values were similar for juveniles at the Mersey Hatchery, Nova Scotia (44°10′N), lipid content of fish at the more southerly station decreased at a greater rate and migratory activity was apparent earlier. This was probably attributable to the advanced temperature cycle at that location. Smolt-release dates are discussed in terms of the development of the marine osmoregulatory mechanisms and the timing of parr–smolt transformation. Key words: Atlantic salmon, seawater adaptation, parr–smolt transformation, migration, hatchery management

We developed an age-structured simulation model incorporating pH-dependent mortality to assess impacts of acidification on Atlantic salmon (Salmo salar) populations at the reach and river system level. Applied to the LaHave River, Nova Scotia, acidic reaches (mean annual pH 4.6–5.1) were predicted to have 0–15% of the annual smoit production and 0–31% of the maiden spawner production compared with circumneutral reaches (pH ≥ 5.6) and increased juvenile growth due to lower parr densities. The benefit of increased growth (earlier age of smoltification and increased early marine survival) was not sufficient to outweigh impacts of higher freshwater juvenile mortality. Simulated removal of acidic conditions resulted in a 41% increase in recruits, but only after several decades following complete chemical recovery. Circumneutral reaches were predicted to be 4–12 times more efficient at producing smolts and 3–7 times more efficient at producing adults from hatchery fingerlings compared with acidic reaches. To maintain current target egg deposition rates of 240 eggs/100 m2, circumneutral reaches could withstand grilse exploitation rates of up to 65%, while acidic reaches, even without harvesting mortality, could not maintain this level. Fisheries management strategies need to account for variability in freshwater production both within and between river systems.

In situ airborne measurements of the turbulent flux and mean values for O3, CO, and CH4 were obtained in the boundary layer over selected wetland systems in Alaska. These measurements were obtained in July–August 1988 as part of the NASA Global Tropospheric Experiment Program's Arctic Boundary Layer Expedition (ABLE 3A). The flux measurements obtained from this study provide information on the source/sink distribution of O3 and CH4 over the Yukon‐Kuskokwim Delta (YKD) and Alaskan North Slope (ANS) regions of Alaska. The source/sink distribution over the YKD is qualitatively correlated with surface vegetation type, identified from multispectral scanner imagery. Direct measurements of the spatial variation in the CH4 source strength were obtained over the YKD. The CH4 source strength over the YKD ranged from 25 to 85 mg m−2 d−1 during a flux survey flight which spanned a considerable portion of the YKD. A spatially averaged, seasonally adjusted source strength of 51 mg m−2 d−1 was established for the YKD. Indirect CH4 flux estimates obtained over the ANS indicate a much lower (∼10 mg m−2 d−1) source strength. The global CH4 emissions from tundra were estimated to be 44 Tg/a based on (1) the spatially averaged source strength obtained over the YKD, (2) current estimates of the global coverage of tundra, and (3) assuming a similarity between other tundra areas and that of the YKD. This estimate is taken to be an upper limit due to possible sampling inadequacies and because the spatial distribution of the CH4 source function over the YKD may not extend to all other northern wetland regions. This estimate is, however, in reasonable agreement with previous estimates. Airborne CO flux measurements over the YKD indicated low negative flux values over the coastal areas, while some positive fluxes were observed in the inland, sparsely forested regions. An inspection of the cospectrum of CO with vertical velocity for sample runs in coastal areas indicated a minimum at wavelengths which were noticeably shorter (70–400 m) than where any prominent feature could be found for similar cospectrums of heat, moisture, O3, or CH4 with vertical velocity. Similar analyses for transects over inland areas indicated occasional peaks in this same, short wavelength band. These features indicate the possibility of in situ photochemical destruction/production of CO, although the identification of a possible chemical mechanism was not attempted at this time. Tundra surfaces are estimated to be responsible for ∼32% of the total deposition loss of O3 poleward of 60°N. Data from the airborne O3 flux measurements made during this study indicate similar values of Rc for the ANS and YKD regions.