Dataset: DEPRECATED: Optical properties

The Varadero Reef is located south-west of the Cartagena Bay close to the southern strait that connects the Bay to the Caribbean Sea in Colombia. The Bay is a receiving estuary from the Magdalena River through the Canal del Dique, a man-made channel whose construction and operation dates back almost a century. The depth of the particular transplant site in Varadero is 3.5m, while at Rosario, a site inside a marine protected area located south-west with relatively high coral cover, is 3m and 12m.

These are results of the preliminary analysis of the optical descriptors calculated from the raw data for each coral fragment: 
- The average (AVG) and standard deviation (SD) of Chlorophyll a density (mg Chl a m-2),
- Estimated absorbance at 675 nm (D 675nm),
- The specific absorption coefficient per unit of pigment (aChl a*, m2 mg Chla -1) and per symbiont (aSymb*, m2 cell-1),
- Symbiodinium density (cell-cm2), and pigment content per symbiont (Ci) (pg Chl a cell-1).
- Coral fragments area (cm2) was calculated using the aluminum foil technique (Marsh 1970).
- Chlorophyll a concentration (mg Chl a cm-2)
- The specific absorption coefficient (a*)

Chlorophyll a concentration was estimated spectrophotometrically after extraction from symbiont cells in acetone/dimethyl sulfoxide (95:5, Vol:Vol; Iglesias-Prieto et al. 1992), using the equations of Jeffrey and Humphrey (1975). Cell numbers were estimated from preserved samples (40 μml Lugol’s iodine) by direct count using a hemocytometer. Coral tissue area was estimated with the aluminum foil technique (Marsh, 1970). Reflectance (R) spectra of coral samples were measured between 400 and 750 nm (5 scans to average per measurement, boxcar width of 1.65 nm). Reflectance is expressed as the ratio of the radiance measured from the coral tissue surface, relative to the radiance obtained from the reference standard, a bleached O. faveolata skeleton. Absorbance (D) spectra were calculated as D=log (1/R), assuming that transmission through the skeleton is negligible. Optical determinations were estimated following Shibata (1969) and Enríquez et al. (2005).

The spectroscopy analyses were performed with a Flame mini-spectrophotometer (Ocean Optics Inc, Florida, USA). Cell counting was performed using a phase hemocytometer (Hausser Scientific, Horsham, USA) .

OceanView 1.6.7 was the software used for processing the tasks of the Flame spectrophotometer.

Methodology References:

- Iglesias-Prieto, R., Matta, J.L., Robins, W.A. and R.K. Trench. 1992. Photosynthetic response to elevated temperature in the symbiotic dinoflagellate Symbiodinium microadriaticum in culture. Proc Natl Acad Sci U S A. 89:10302-10305. Full text pdf: http://www.pnas.org/content/89/21/10302.full.pdf.
- Jeffrey, S.W. and G.F. Humphrey. 1975. New spectrophotometric equations for determining chlorophylls a, b, c1 and c2 in higher plants, algae and natural phytoplankton. Biochem. Physiol. Pflanzen 167: 191-194. DOI:10.1016/S0015-3796(17)30778-3
- Marsh, J. A. 1970. Primary productivity of reef-building calcareous red algae. Ecology 51: 255–265. DOI: 10.2307/1933661.
- Shibata, K. 1969. Pigments and a UV-absorbing substance in corals and a blue-green alga living in the Great Barrier Reef. Plant Cell Physiol. 10: 325–335. DOI: 10.1093/oxfordjournals.pcp.a074411
- Enríquez, S., E.R. Méndez and R. Iglesias-Prieto. 2005. Multiple scattering on coral skeletons enhances light absorption by symbiotic algae. Limnol. Oceanogr., 50(4), 2005, 1025–1032. DOI: 10.4319/lo.2005.50.4.1025