Measurements of spectral optical properties and their relation to biogeochemical variables and processes in Crater Lake, Crater Lake National Park, OR

Spectral inherent optical properties (IOPs) have been measured at Crater Lake, OR, an extremely clear sub-alpine lake. Indeed Pure water IOPs are major contributors to the total IOPs, and thus to the color of the lake. Variations in the spatial distribution of IOPs were observed in June and September 2001, and reflect biogeochemical processes in the lake. Absorption by colored dissolved organic material increases with depth and between June and September in the upper 300 m. This pattern is consistent with a net release of dissolved organic materials from primary and secondary production through the summer and its photo-oxidation near the surface. Waters fed by a tributary near the lake’s rim exhibited low levels of absorption by dissolved organic materials. Scattering is mostly dominated by organic particulate material, though inorganic material is found to enter the lake from the rim following a rain storm. Several similarities to oceanic oligotrophic regions are observed: (a) The Beam attenuation correlates well with particulate organic material (POM) and the relationship is similar to that observed in the open ocean. (b) The specific absorption of colored dissolved organic material has a value similar to that of open ocean humic material. (c) The distribution of chlorophyll with depth does not follow the distribution of particulate organic material due to photo-acclimation resulting in a subsurface pigment maximum located about 50 m below the POM maximum.

[1]  Katja Fennel,et al.  Subsurface maxima of phytoplankton and chlorophyll: Steady‐state solutions from a simple model , 2003 .

[2]  Sean G. Herring,et al.  Shape of the particulate beam attenuation spectrum and its inversion to obtain the shape of the particulate size distribution. , 2001, Applied optics.

[3]  James W. Brown,et al.  A semianalytic radiance model of ocean color , 1988 .

[4]  E. Boss,et al.  Relationship of light scattering at an angle in the backward direction to the backscattering coefficient. , 2001, Applied optics.

[5]  Andrew H. Barnard,et al.  Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf , 2001 .

[6]  Volume Scattering Function and Backscattering Coefficients: Instruments, Characterization, Field Measurements and Data Analysis Protocols , 2003 .

[7]  A. Morel.  Optical properties of pure water and pure sea water , 1974 .

[8]  J. Zaneveld,et al.  An analysis of the optical features of the near-bottom and bottom nepheloid layers in the area of the Scotian Rise , 1982 .

[9]  James C. Kitchen,et al.  On the noncorrelation of the vertical structure of light scattering and chlorophyll α in case I waters , 1990 .

[10]  James K. B. Bishop,et al.  Transmissometer measurement of POC , 1999 .

[11]  C. Moore,et al.  WET labs ac-9: field calibration protocol, deployment techniques, data processing, and design improvements , 1997, Other Conferences.

[12]  Richard F. Davis,et al.  Reducing the effects of fouling on chlorophyll estimates derived from long‐term deployments of optical instruments , 1997 .

[13]  L. Young,et al.  Unusual bacterioplankton community structure in ultra‐oligotrophic Crater Lake , 2001 .

[14]  P. Kaiser.  The role of non-living organic matter in the earth's carbon cycle: Zepp, R.G. & Sonntag, C.H. (Eds) Vol. 1 (15.5×23.5 cm), 342 pages. John Wiley & Sons , 1995 .

[15]  Michael S. Twardowski,et al.  Microscale Quantification of the Absorption by Dissolved and Particulate Material in Coastal Waters with an ac-9 , 1999 .

[16]  W. Gardner,et al.  Effects of monsoons on the seasonal and spatial distributions of POC and chlorophyll in the Arabian Sea , 1998 .

[17]  M. Buktenica,et al.  Ultraviolet radiation and bio-optics in Crater Lake, Oregon , 2006, Hydrobiologia.

[18]  Andrew H. Barnard,et al.  A model for estimating bulk refractive index from the optical backscattering ratio and the implications for understanding particle composition in case I and case II waters , 2001 .

[19]  R. Maffione,et al.  Instruments and methods for measuring the backward-scattering coefficient of ocean waters. , 1997, Applied optics.

[20]  Casey C. Moore,et al.  Scattering error correction of reflecting-tube absorption meters , 1994, Other Conferences.

[21]  Michael S. Twardowski,et al.  Particulate backscattering ratio at LEO 15 and its use to study particle composition and distribution , 2004 .

[22]  R. Bukata,et al.  Optical Properties and Remote Sensing of Inland and Coastal Waters , 1995 .

[23]  Walker O. Smith,et al.  Seasonal patterns of water column particulate organic carbon and fluxes in the Ross Sea, Antarctica , 2000 .

[24]  C. D. Mcintire,et al.  Taxonomic structure and productivity of phytoplankton assemblages in Crater Lake, Oregon , 1996 .

[25]  K. Baker,et al.  Optical properties of the clearest natural waters (200-800 nm). , 1981, Applied optics.

[26]  A. J. Allnutt.  Optical Aspects of Oceanography , 1975 .

[27]  H. Claustre,et al.  Variability in the chlorophyll‐specific absorption coefficients of natural phytoplankton: Analysis and parameterization , 1995 .

[28]  H. Sosik,et al.  Light absorption by phytoplankton, photosynthetic pigments and detritus in the California Current System , 1995 .

[29]  C. Mobley.  Light and Water: Radiative Transfer in Natural Waters , 1994 .