Lake Biology

Chlorophyll-A Concentrations in Lake Hoare Benthic Mats 1996-97


As part of the Long Term Ecological Research (LTER) project in the McMurdo Dry Valleys of Antarctica, the growth of benthic cyanobacteria-dominated mats in the lakes have been monitored. This dataset shows chlorophyll-a levels associated with the benthic mats. Values are provided for various depths of Lake Hoare during the 1996-97 field season, both with and without correction for phaeopigments.

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These data are based on analysis of replicated 1.98 cm2 cores of the pigmented surface layer of benthic microbial mats from Lake Hoare. Parallel experiments in which thicker cores were sectioned showed that this surface layer contained all chlorophyll-a present in the cores. They are expressed per unit area of core, units andmicro;g/cm2 (micrograms per square centimeter). All depths refer to depth from the surface and are in meters. Samples were obtained from an approximately linear transect stretching from the Lake Hoare laboratory complex towards the lake deepspot. Cores were collected through December 1996 by scuba divers. Initially, cores of 7 cm diameter were collected using sharpened perspex coring tubes. After retrieval to the surface, these were subsampled using sharpened, cut-off syringe barrels. Cores were stored at -20anddeg;C, in the dark, until processed in New Zealand some 2-3 months later. Extraction was into 10 ml of 90% acetone (allowing for volume of water in core), and was aided by grinding with a teflon pestle in a glass tube. Calculations were based on absorptance of the extract measured at 665, corrected by subtracting that at 750 nm. Correction for phaeopigments was accomplished by re-measuring absorptance after acidification with dilute HCl. Equations used for calculating chlorophyll-a in andmicro;m/cm2 with (Eq 1) and without (Eq 2) correction for phaeopigments were: Eq 1: (A665(na)-A665(ac)) x 27.3 x 1/vol x 1/area Eq 2: A665(na) x 11.23 x 1/vol x 1/area where A665(na) and A665(ac) are corrected absorptances (as optical density) before and after acidification, vol is volume of acetone used (ml) and area is the area of the core (cm2).


Metadata completed in 2016Data and metadata migrated into the Drupal Ecological Information Management System in 2014. (San Gil)

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The data were obtained by Dr. Ian Hawes of the National Institute of Water and Atmospheric Research, Christchurch New Zealand ( ), who should be contacted with any queries. The research was funded by the New Zealand Foundation for Research, Science and Technology, under grant CO1601. Logistic support was provided by the Taylor Valley Long Term Ecological Research Program.


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