... a very long day and almost the death of my filtering pumps.
I then drive the samples back down to the lab, pop them in the fridge and get ready to filter for the next four or five hours. First I preserve 100ml of unfiltered water from each tank with Lugols, this is for algae identification and bio-volume counts. I send off 50ml unfiltered water from each tank to chemistry for total nutrient analysis (the nutrients found in the water and also within organisms).
The rest of the water sample gets filtered like you can see below. I need one filter for chlorophyll a analysis (we do laboratory analysis as well as using the sonde ) and one filter for cyanobacteria cellular toxin analysis. Toxins can be within cells or released into the water so I also need to take a certain volume of the filtered water for in-water toxin analysis. Some of the tanks are so high in biomass that obtaining the right volume of water for toxin analysis takes a long time and a lot of filters. Below is pump one of two, they run continuously. I started filtering at 10am and finished at 3.15pm - the poor pumps felt a bit hot by the end. The remainder of the filtered sample is split into another sample for nitrate analysis which the chemists process and the other part for srp (soluble reactive phosphorus) analysis which I will do later in the afternoon. Nutrients can be held within organisms or are available in the water column, total nutrients is a measure of both whilst srp calculates what is available in the water. Cells will release these nutrients when they die and so a high srp in a closed system like the mesocosms can be indicative of a break down of biomass.
Once the filtering is done I get on with srp analysis. This involves chemistry, reactions, sulphuric acid which smells pretty bad, wearing safety goggles which make me look very attractive and a spectrophotometer, which I can't say properly.
And that marks the end of Wednesday, well usually it would. Because of the weather day three, Thursday is being moved to day two so I have to now bike home to get the head torches (which I forgot) to start on part three, night zooplankton sampling.
I have managed to turn my rather unhealthy obsession with plankton in to my day job. Things don't get much better than this! This blog documents my PhD research and the plankton delights I encounter along the way.