... lots of data and some dead fish.
This is actually the last sampling event (one of twenty seven) for the mesocosm experiment. So in case I miss it here is a break down of what happens when we go and sample.
Day 1: in situ data collection (sondes, algaetorch and nephlometer), periphyton and maintenance
Day 2: collection of water samples, filtration in the lab for toxins and chlorophyll a, srp analysis and sample fixation for bio-volume counts
Day 3: Night time zooplankton sampling
Day 1 - Tuesday, in situ data collection
As soon as I get to the mesocosms the Exo2-sonde goes into the first tank, we take averages from at least six readings which takes four minutes per tank, four times thirty two equals lots of minutes so I get that started straight away. The EXO2 is a muti-parameter sonde that measures temperature, conductivity, salinity, pH, dissolved oxygen, chlorophyll and blue-green alage (cyanos). Measurements are logged internally which means I can get on with taking some other readings. The algae torch also measures chlorophyll a and cyanobacteria biomass using fluorescence of algae cells and is used to get an in-situ measurements. I, as a plankton geek think it pretty cool! The nephelometer measures turbidity (suspended particulates) by recording the light reflected from the particles (from a beam of light emitted from the instrument).
As I go around I also check all the tanks for any maintenance issues and clean all the sensors (temperature, oxygen and PAR - photosynthetically active radiation) located in the tanks. I also make any observations of 'unusual' activity in the tanks, like these dead fish found below. I'm not entirely sure why there were so many dead right now, the only thing immediately different about this tank is the amount of dissolved oxygen (%) - 27% compared to >65% in the rest of the tanks, which could be a factor.
To account for this, periphyton growth is measured on a monthly basis in each tank by calculating the dried weight from pre-measured in-situ strips. The picture below shows the difference in the bio-volume and type of periphyton growing in each tank which demonstrated nicely the need to account for this effect.
And that marks the end of the Tuesday session up at the mesocosms. All I need to do now is enter the data and prepare for the sampling marathon tomorrow.
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.