Spatial variability of phytoplankton absorption coefficients and pigments off Baja California during November 2002
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We have estimated the spatial variability of phytoplankton specific absorption coefficients (a*ph) in the water column of the California Current System during November 2002, taking into account the variability in pigment composition and phytoplankton community structure and size. Oligotrophic conditions (surface Chl < 0.2 mg m−3) dominated offshore, while mesotrophic conditions (surface Chl 0.2 to 2.0 mg m−3) where found inshore. The specific absorption coefficient at 440 [a*ph(440)] ranged from 0.025–0.281 m2mg−1 while at 675 nm [a*ph(675)] it varied between 0.014 and 0.087 m2mg−1. The implementation of a size index based on HPLC data showed the community structure was dominated by picoplankton. This would reduce the package effect in the variability of a*ph(675). Normalized aph curves were classified in two groups according to their shape, separating all spectra with peaks between 440 and 550 nm as the second group. Most samples in the first group were from surface layers, while the second group were from the deep chlorophyll maximum or deeper. Accessory photoprotective pigments (APP) tended to decrease with depth and accessory photosynthetic pigments (APS) to increase, indicating the importance of photoprotective mechanisms in surface layers and adaptation to low light at depth. Samples with higher ratios of APP:APS (>0.4) were considered as phytoplankton adapted to high irradiances, and lower ratios (<0.26) as adapted to low irradiances. We found a good relationship between APP:APS and a*ph(440) for the deeper layer (DCM and below), but no clear evidence of the factors causing the variability of a*ph(440) in the upper layer.
KeywordsAbsorption coefficient phytoplankton pigments HPLC California Current
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- Bidigare, R. R. and C. C. Trees (2000): HPLC phytoplankton pigments: sampling, laboratory methods, and quality assurance procedures. p. 154–161. In Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Revision 2, Chapter 4, ed. by G. S. Farigion and J. L. Mueller, NASA TM 2000-209966, Goddard Space Flight Center, Greenbelt, MD.Google Scholar
- Jeffrey, S. W., R. F. C. Mantoura and S. W. Wright (1997): Phytoplankton Pigments in Oceanography: Guidelines and Modern Methods. UNESCO Publishing, Paris, 661 pp.Google Scholar
- Kishino, M., N. Takahashi, N. Okami and S. Ichimura (1985): Estimation of the spectral absorption coefficients of phytoplankton in the sea. Bull. Mar. Sci., 37, 634–642.Google Scholar
- Utermöhl, H. (1958): Zur vervollkommnung der quantitativen phytoplankton methodik. Mitteilungen Internationale Vereingung fuer Theoretische und Angewandte Limnologie, 9, 1–38.Google Scholar