Abstract:

This dataset contains measurements of chlorophyll concentrations and optical absorption spectra derived from particulate filtrations of water samples and the particle-free filtrate. More specifically, the dataset reports chlorophyll-a concentration using the Welschmeyer (1994) method (“no acid” technique), chlorophyll-a and phaeophytin concentration using the Holm-Hansen and Riemann (1978) methods (‘acid” technique), optical absorption measurements of detrital, dissolved material (colored dissolved organic matter (CDOM) or gelbstoff) and particulate material. The water samples were collected using a CTD rosette or surface water sample aboard the R/V Point Sur cruise DP06 from 2018-07-20 to 2018-08-01. The CTD data collected during this cruise can be found under GRIIDC Unique Dataset Identifier (UDI) R4.x257.000:0031 (DOI: 10.7266/n7-ceq1-5g82). The optical absorption spectra from seawater’s particulate and dissolved components can be used to compute the penetration of light to various depths, estimate the proportion of living to non-living particulate matter, assess photosynthetic light availability and the type of phytoplankton present, and the validate of satellite or airborne ocean color measurements. Chlorophyll and phaeopigment concentrations are often used to estimate the amount of phytoplankton in water samples, and to allow extrapolation of in situ fluorometric measurements. The R/V Point Sur DEEPEND cruise DP06 was led by chief scientist Dr. Tracey Sutton.

Suggested Citation:

Chuanmin Hu. 2019. Chlorophyll concentration and optical absorption spectra of particulate and dissolved material collected aboard the R/V Point Sur cruise DP06 from 2018-07-20 to 2018-08-01. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-3t9h-8p38

Purpose:

Chlorophyll concentrations and the spectral absorption of particulates and dissolved material was measured from selected water samples to validate in situ fluorometers and to aid estimates of the distribution of light.

Data Parameters and Units:

File DP06_chl.xlsx: date and time (DD-MMM-YYYY hh:mm UTC), latitude (decimal degrees), longitude (decimal degrees), station, cast id, sampling depth (m), chlorophyll a (Chl a; mg m^-3), phaeophytin (Pheo; mg m^-3), comments. W94 stands for Welschmeyer (1994) method (“no acid” technique) and HH&R stands for Holm-Hansen and Riemann (1978) methods (‘acid” technique). Files DP06_[ad, ag, ap]_5nm.xlsx: date (MM-DD-YYYY), time (hh:mm UTC), ), latitude (decimal degrees), longitude (decimal degrees), cast id, sampling depth (m), optical density of particulate filter at 675nm (ODp(675)), wavelength (nm), particulate absorption (ap(lambda); m^-1) from 400 to 750nm, detrital absorption (ad(lambda); m^-1) from 400 to 750nm, Colored Dissolved Organic Matter (CDOM) absorption (aCDOM(lambda); m^-1) from 250 to 600nm. Absorption values are unreliable when optical ODp(675) is <0.03, i.e. too little water filtered). Data with ODp(675) values between 0.03 and 0.04 should be treated with caution. Dataset also includes readme files and cruise data documentation.

Methods:

Optical absorption measurements for detrital and particulate material were made using the Quantitative Filter Technique (QFT, Mitchell, 1990) and the spectra measured in 5 nm increments from 400 to 750nm material using a 512-channel spectral radiometer (Spectrix). Whatman’s GF/F (25mm diameter) filters were used particulate and detrital material. Pigment extraction was done using hot methanol (Kishino et al., 1985). Chlorophyll-a measurements were done using a Turner Designs 10-AU-005 Field Fluorometer. Fluorometers were both calibrated using chlorophyll a from A. nidulans (Sigma) dissolved in 100% HPLC-grade methanol. Samples for CDOM were filtered using a Whatman 0.2 um filter. Optical absorption measurements of CDOM were made in 250 to 600nm using a Perkin-Elmer Lambda 25 UV/VIS spectrophotometer.

Instruments:

512-channel spectral radiometer (Spectrix) Turner Designs 10-AU-005 Field Fluorometer Perkin-Elmer Lambda 25 UV/VIS spectrophotometer

Provenance and Historical References:

C.S. Yentsch (1962). Measurement of visible light absorption by particulate matter in the ocean. Limnology and Oceanography, 7(2): 207-217. doi:10.4319/lo.1962.7.2.0207 D.A. Kiefer and J.B. SooHoo (1982). Spectral absorption by marine particles of coastal waters of Baja California. Limnology and Oceanography, 27(3): 492-499. doi:10.4319/lo.1982.27.3.0492 Holm-Hansen, O., Lorenzen, C.J., Holmes, R.W., and J.D.H. Strickland (1965). Fluorometric Determination of Chlorophyll. ICES Journal of Marine Science, 30(1): 3-15. doi:10.1093/icesjms/30.1.3 O. Holm-Hansen, O., and Riemann, B. (1978). Chlorophyll a Determination: Improvements in Methodology. Oikos, 30(3), 438. doi:10.2307/3543338 Kishino, M., Takahashi, M., Okami, N., and S. Ichimura (1985). Estimation of the spectral absorption coefficients of phytoplankton in the sea. Bulletin of Marine Science, 37(2): 634-642. Mitchell, B. G. (1990). Algorithms for determining the absorption coefficient for aquatic particulates using the quantitative filter technique. In Ocean optics X (Vol. 1302, pp. 137-149). International Society for Optics and Photonics. doi:10.1117/12.21440 Mueller, J.L., Fargion, G.S., McClain, C.R., Pegau, S., Zanefeld, J.R.V., Mitchell, B.G., Kahru, M., Wieland, J. and Stramska, M. (2003). Ocean optics protocols for satellite ocean color sensor validation, revision 4, volume IV: Inherent optical properties: Instruments, characterizations, field measurements and data analysis protocols. Welschmeyer, N. A. (1994). Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments. Limnology and Oceanography, 39(8), 1985–1992. doi:10.4319/lo.1994.39.8.1985

Individual Files: