Algal microbial mat biomass measurements from the McMurdo Dry Valleys and Cape Royds, Antarctica (1994-2025, ongoing)

Abstract:

As part of the Long Term Ecological Research (LTER) project in the McMurdo Dry Valleys of Antarctica, a systematic sampling program has been undertaken to monitor the glacial meltwater streams in that region. This dataset contains microbial biomass concentrations found in algal mats located in streams throughout the McMurdo Dry Valleys as well as in ponds of the nearby Cape Royds. Microbial mat biomass has been collected as part of the McMurdo LTER since the 1993-1994 field season and measured as ash-free dry mass (AFDM) and chlorophyll-a (Chl-a).

LTER Core Areas:

primary production

Dataset ID:

Associated Personnel:

1246

927

1247

926

928

Short name:

STRM_MICROBIAL_BIOMASS

Data sources:

STREAMS_MICROBIAL_BIOMASS

Methods:

Algal mats were sampled along transects established by the MCM LTER in early to mid-January as in Alger et al. (1997), and mats were identified as either orange, black, green, or red in color. Mats were collected using a brass cork borer (1.7 cm diameter) and placed into Whirlpack® bags containing stream water. In the laboratory, samples were de-watered on pre-combusted Whatman GF/C filters, wrapped in foil, and stored at -20°C. Prior to the year 2000, Chl-a samples were extracted in buffered acetone and analyzed spectrophotometrically using the trichromatic method. After 2000, Chl-a was extracted in buffered acetone and analyzed using a Turner Designs 10-AU field fluorometer. Both methods have been shown to produce comparable Chl-a results (Lorenzen and Jeffrey 1980). For AFDM analysis, samples were dried at 100 °C for 24 h, weighed, burned at 450 °C for 4 h and re-weighed, and then re-wetted and dried to determine mass loss due to hydration of sediments. Both Chl-a and AFDM analyses were performed at Crary Laboratory in McMurdo Station.

Additional notes:

AFDM for 2019-2020 season samples was conducted at CU Boulder in 2022.

Samples collected during the 2020-2021 "Covid year" season were collected by a contractor and sent back to CU Boulder for analysis. Chl-a was analyzed on a UV Vis Spectrophotometer. Samples were kept in refrigeration for two months before Chl-a was analyzed. For AFDM analysis, samples were put directly into drying tins and were not placed on filters.

In the 2022-2023 season, the protocol varied from the the typical protocol, which is to collect a sample of algal mat and dewater it with a combusted and pre-weighed filter. This filter is then a part of the sample when it is dried, combusted, and rewett. Inserting the filter after collection was overlooked and was realized at the rewetting step because the filter aids in rewetting the combusted mat. We made the decision to add the filter at this step in order to continue with the rewetting. We took note of the weight of the filter and subtracted it out as is usually done.

Maintenance:

The original iterations of the 'stream microbial biomass' data file were created by Tyler Kohler, Lee Stanish and Diane McKnight, and submitted to Inigo San Gil (the data manager) at the Institute of Arctic and Alpine Research (INSTAAR). For proper standardization in the database, the data was massaged into the fields strmgageid, collection date, etc. Entered in the database using Toad 4 Oracle from Dell inc (formerly own by Quest inc.)