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Testing sample stability using four storage methods and the macroalgae Ulva and Gracilaria
Citation:
Oczkowski, A., C. Thornber, E. Markham, R. Rossi, A. Ziegler, AND S. Rinehart. Testing sample stability using four storage methods and the macroalgae Ulva and Gracilaria. Limnology and Oceanography: Methods. American Society of Limnology and Oceanography, Lawrence, KS, 13(1):9-14, (2015).
Impact/Purpose:
Oftentimes laboratory procedures are developed from a hybrid of our training on a particular method and our own philosophical beliefs of what constitutes "best laboratory practices." But, the relative importance of each prepatory step is rarely addressed by individual researchers. Here we assess the stability of samples for analysis for nitrogen and carbon content and stable isotope values and find that the samples are more robust than we thought, allowing researchers greater flexibility in sample analysis.
Description:
Concern over the relative importance of different sample preparation and storage techniques frequently used in stable isotope analysis of particulate nitrogen (δ15N) and carbon (δ13C) prompted an experiment to determine how important such factors were to measured values in marine organisms. We stored the marine macroalgae Ulva and Gracilaria in four different ways and analyzed replicates every three months over the course of a year to assess treatment effects on stability. Treatments consisted of algae dried at 65°C, ground to a powder, and stored in a desiccator until analysis, algae either left in both a drying oven or freezer and processed (dried and ground) just prior to analysis and some dried, ground samples were kept out in the lab and re-analyzed quarterly for 12 months. Concurrent with this, samples were freshly collected from the same location and analyzed along with the other treatments at each time step. Remarkably, neither storage technique nor time appears to have a long term impact on either δ15N or δ13C values or the %N and %C of the algae tissues. There were clear and consistent differences between species and some large seasonal differences in the freshly collected samples. The interspecies and seasonal ranges of values underscore the stability associated with the method and duration of sample storage.
