Greater Number of Samples?My last entry had a huge gap before it and I would just like to give you an idea of why things have become so hectic. We started the season sampling from the zodiac to collect two bottles per depth, a 1 liter black Teflon bottle for our delicate samples and a brown plastic gallon bottle for our pigment filtrations. Pigments are a sample taken to define the types of biological matter present in the water; this is frozen and sent back to the US for HPLC analysis. These were taken in this order and each depth would take about 5 minutes to sample from. This has increased to 8 bottles and the time required to sample each depth is about 15-20 minutes. So things have changed more than slightly. I thought over the next couple days I would run through the reasons for increasing the amount of samples and explain what these samples are used for.
Back when we were experiencing early growth of a pretty large phytoplankton bloom, we realized that the DMS samples (delicate gas samples) needed to be sampled out on the boat instead of trying to re-pour the samples after getting them home. The reason for this is that the phytoplankton are more apt to create DMS while being disrupted. There is not really any good way to keep from disrupting them while transferring them from the black bottle into a sample vial. This is one of the difficult sampling situations we had decided against back in the beginning of our stay. This is unfavorable for us due to the increased amount of time out in the boat pushing our very full day back and potentially sacrificing our ability to perform well on rough sea days. We fear this from the aspect of seasickness and loss of good sampling technique.
Since we started this type of sampling we have had better reproducibility until the bloom really started to produce. A couple samplings later it became obvious that there was still some DMS production occurring in the samples. Too many of the phytoplankton were getting into the samples so we had to resort to increasing our time out on the boat again. This time the answer was to pass the water through a Nytex mesh screen to remove a large portion of the phytoplankton. Since the transportation of the samples with the phytoplankton still insolution was the cause of extra DMS, this simple screening keeps the DMS levels stable and our analysis more exact.
The next issue…