Growth Rates of Important Reindeer Forage Lichens on the Seward Peninsula, Alaska

Cladonia alpestris, C. rangiferina and C. sylvatica may comprise 75-90% of all lichens eaten by reindeer. Their growth rates must be known to determine the carrying capacity, rates of recovery and patterns for rotational grazing of reindeer rangelands. Data from two sites near Nome and a third near Koyuk show the annual linear rates of growth of these three species to be 5.0, 5.3 and 5.4 mm respectively. These averages exceed those of northern Canada and some areas in the USSR. C. rangiferina reaches the podetium renewal period in 5.9 yr, or in almost half the time required by the other two species.Taux de croissance d'importants lichens fourragers du renne, dans la Péninsule de Seward, Alaska. Les taux linéaires moyens annuels de croissance de Cladonia alpestris, C. rangiferina et C. sylvatica dans la péninsule de Seward, Alaska, ont été établis respectivement à 5, 5.3 et 5.4 mm. Ces moyennes sont plus grandes que celles du nord du Canada et de quelques régions de l'U.R.S.S. Cladonia rangiferina atteint sa période de renouvellement du podétium en 5.9 années, ce qui est à peu près la moitié du temps requis par les deux autres espèces

Reindeer Range Appraisal In Alaska

Thesis (M.S.) University of Alaska Fairbanks, 196

Spectral variability of the particulate backscattering ratio

The spectral dependency of the particulate backscattering ratio is relevant in the fields of ocean color inversion, light field modeling, and inferring particle properties from optical measurements. Aside from theoretical predictions for spherical, homogeneous particles, we have very limited knowledge of the actual in situ spectral variability of the particulate backscattering ratio. This work presents results from five research cruises that were conducted over a three-year period. Water column profiles of physical and optical properties were conducted across diverse aquatic environments that offered a wide range of particle populations. The main objective of this research was to examine the behavior of the spectral particulate backscattering ratio in situ, both in terms of its absolute magnitude and its variability across visible wavelengths, using over nine thousand 1-meter binned data points for each of five wavelengths of the spectral particulate backscattering ratio. Our analysis reveals no spectral dependence of the particulate backscattering ratio within our measurement certainty, and a geometric mean value of 0.013 for this dataset. This is lower than the commonly used value of 0.0183 from Petzold\u27s integrated volume scattering data. Within the first optical depth of the water column, the mean particulate backscattering ratio was 0.010

Why should we measure the optical backscattering coefficient?

In recent years commercial sensors for in situ determinations of optical backscattering coefficient, bb, have become available. The small size and low power requirements of these sensors permit deployment from small sensing platforms such as autonomous underwater vehicles, in addition to standard profiling packages. Given their rapid sampling time (sub second) they can collect data with high temporal and spatial resolution (sub meter). While these are attractive features of any sensor they do not answer the question: why should oceanographers measure bb? The short answer is that bb carries useful information about seawater constituents that scatter light. The potential to derive information about the abundance and the types of suspended marine particles, which play different roles in ocean ecosystems and biogeochemical cycling, is particularly attractive. To first order, the bb coefficient is a proxy for particle abundance but it also depends significantly on particle size distribution and particle composition, for example, on relative proportions of small and larger particles or on whether the particles are organic or inorganic. Most importantly, however, the spectral reflectance of the ocean (known as ocean color) is, to first order, proportional to bb. The measurements of ocean color from remote optical sensors on satellites provide a unique capability to monitor surface ocean properties (e.g., chlorophyll concentration and biological primary productivity) over extended spatial and temporal scales. Measurements and fundamental understanding of bb are required for understanding and successful applications of remotely sensed ocean color

Evaluation of bio-optical inversion of spectral irradiance measured from an autonomous underwater vehicle

Autonomous underwater vehicles (AUVs) can map water conditions at high spatial (horizontal and vertical) and temporal resolution, including under cloudy conditions when satellite and airborne remote sensing are not feasible. As part of the RADYO program, we deployed a passive radiometer on an AUV in the Santa Barbara Channel and off the coast of Hawaii to apply existing bio-optical algorithms for characterizing the optical constituents of coastal seawater (i.e., dissolved organic material, algal biomass, and other particles). The spectral differences between attenuation coefficients were computed from ratios of downwelling irradiance measured at depth and used to provide estimates of the in-water optical constituents. There was generally good agreement between derived values of absorption and concurrent measurements of this inherent optical property in Santa Barbara Channel. Wave focusing, cloud cover, and low attenuation coefficients influenced results off the coast of Hawaii and are used to evaluate the larger-scale application of these methods in the near surface coastal oceans

Spectral backscattering properties of marine phytoplankton cultures

The backscattering properties of marine phytoplankton, which are assumed to vary widely with differences in size, shape, morphology and internal structure, have been directly measured in the laboratory on a very limited basis. This work presents results from laboratory analysis of the backscattering properties of thirteen phytoplankton species from five major taxa. Optical measurements include portions of the volume scattering function (VSF) and the absorption and attenuation coefficients at nine wavelengths. The VSF was used to obtain the backscattering coefficient for each species, and we focus on intra- and interspecific variability in spectral backscattering in this work. Ancillary measurements included chlorophyll-a concentration, cell concentration, and cell size, shape and morphology via microscopy for each culture. We found that the spectral backscattering properties of phytoplankton deviate from theory at wavelengths where pigment absorption is significant. We were unable to detect an effect of cell size on the spectral shape of backscattering, but we did find a relationship between cell size and both the backscattering ratio and backscattering crosssection. While particulate backscattering at 555 nm was well correlated to chlorophyll-a concentration for any given species, the relationship was highly variable between species. Results from this work indicate that phytoplankton cells may backscatter light at significantly higher efficiencies than what is predicted by Mie theory, which has important implications for closing the underwater and remotely sensed light budget

Toward closure of upwelling radiance in coastal waters

We present three methods for deriving water-leaving radiance Lw(λ) and remote-sensing reflectance using a hyperspectral tethered spectral radiometer buoy (HyperTSRB), profiled spectroradiometers, and Hydrolight simulations. Average agreement for 53 comparisons between HyperTSRB and spectroradiometric determinations of Lw(λ) was 26%, 13%, and 17% at blue, green, and red wavelengths, respectively. Comparisons of HyperTSRB (and spectroradiometric) Lw(λ) with Hydrolight simulations yielded percent differences of 17% (18%), 17% (18%), and 13% (20%) for blue, green, and red wavelengths, respectively. The differences can be accounted for by uncertainties in model assumptions and model input data (chlorophyll fluorescence quantum efficiency and the spectral chlorophyll-specific absorption coefficient for the red wavelengths, and scattering corrections for input ac-9 absorption data and volume scattering function measurements for blue wavelengths) as well as radiance measurement inaccuracies [largely differences in the depth of the Lu(λ, z) sensor on the HyperTSRB]. © 2003 Optical Society of America

Particulate Backscattering Ratio at Leo 15 and Its Use to Study Particle Composition and Distribution

Particulate scattering and backscattering are two quantities that have traditionally been used to quantify in situ particulate concentration. The ratio of the backscattering by particles to total scattering by particles (the particulate backscattering ratio) is weakly dependent on concentration and therefore provides us with information on the characteristics of the particulate material, such as the index of refraction. The index of refraction is an indicator of the bulk particulate composition, as inorganic minerals have high indices of refraction relative to oceanic organic particles such as phytoplankton and detrital material that typically have a high water content. We use measurements collected near the Rutgers University Long-term Ecosystem Observatory in 15 m of water in the Mid-Atlantic Bight to examine application of the backscattering ratio. Using four different instruments, the HOBILabs Hydroscat-6, the WETLabs ac-9 and EcoVSF, and a prototype VSF meter, three estimates of the ratio of the particulate backscattering ratio were obtained and found to compare well. This is remarkable because these are new instruments with large differences in design and calibration. The backscattering ratio is used to map different types of particles in the nearshore region, suggesting that it may act as a tracer of water movement. We find a significant relationship between the backscattering ratio and the ratio of chlorophyll to beam attenuation. This implies that these more traditional measurements may be used to identify when phytoplankton or inorganic particles dominate. In addition, it provides an independent confirmation of the link between the backscattering ratio and the bulk composition of particles