Abstract:

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 to validate satellite or airborne ocean color measurements. Chlorophyll and phaeopigment concentrations are often used to estimate the amount of phytoplankton present, and to allow extrapolation of in situ fluorometric measurements. Water was collected using a CTD rosette near the surface and from several depths at each sampling station occupied by the DEEPEND cruise DP05 (see GRIIDC dataset R4.x257.226:0014). A variable amount (<1 to 5 l) of this water was filtered through glass-fiber filter pads. The filter pads were stored for subsequent analysis. Some of the filtrate was passed through an additional nylon membrane (0.2 µm) filter, and also retained for shore based analysis. Optical absorption of the particulate material on the filter pads was determined on shore, using the quantitative filter technique (Yentsch, 1962; Kiefer and SooHoo, 1982). The spectral transmission of light (400-800nm) passing through each filter pad was measured, both before and after the phytoplankton pigments are extracted from the particles retained on the filter pad using methanol (Kishino et al., 1985). These techniques allow the optical absorption spectra of the particles in the water to be determined, as well as the proportion of absorption due to pigmented or detrital material. The extraction of pigments allows the chlorophyll a and phaeopigment concentration to be determined fluorometrically using an acidification technique (Holm-Hansen et al., 1965; Holm-Hansen and Riemann, 1978). The filtrate from the at sea filtration is analyzed using a spectrophotometer to determine the absorption spectra (200-800nm) of the colored dissolved material (CDOM) in the water sample. This data was collected during the same cruise as GRIIDC CTD dataset R4.x257.230:0013.

Suggested Citation:

Hu, Chuanmin. 2018. Chlorophyll concentration and optical absorption spectra of particulate and dissolved material, collected at several depths on DEEPEND cruises DP05 from January-December 2017. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N73B5XHK

Purpose:

Chlorophyll concentrations and the spectral absorption of particulates and dissolved material was measured from selected water samples to validate in situ fluorometers, for comparison with remote sensing reflectance and optical properties, and to aid estimates of the distribution of light.

Data Parameters and Units:

Time (DD-MMM-YYYY HH:MM UTC) Latitude (decimal degrees) Longitude (decimal degrees) Sampling depth (m) Station Chlorophyll a (mg m^-3) Particulate absorption (m^-1) from 400 to 750nm Detrital absorption (m^-1) from 400 to 750nm Colored Dissolved Organic Matter (CDOM) absorption (m^-1) from 250 to 600nm

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 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. 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 and B. Riemann (1978). Chlorophyll a Determination: Improvements in Methodology. Oikos, 30(3): 438-447. doi:10.2307/3543338

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