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  After a short journey to the Cranedale Centre, where we would be staying for the next few days, we were instantly brought out of our newly assigned rooms in order to be briefed on our schedule for the remainder of our stay. We were also given an introduction to the preliminary investigation that we were going to undertake that afternoon at a stream nearby. Our aim for the field trip was “to investigate the impact of sewage effluent on the invertebrate biodiversity in rivers.”
The first afternoon of field work enabled the biologists to gain an understanding of the techniques that
we were to use for our final data collection on the penultimate day. Lucky for us we were rewarded with exceptionally nice weather across the three days of
our stay, and so it didn’t bother us too much when our wellies were flooded with river water after testing how far into the river we were able to go without our wellies being overtopped!
After a long day of travelling and data collection, it was time for everyone to cram into the minibuses and head back to the Cranedale centre for the night. Everyone was relieved to find out that when we returned we had some free time before our evening lesson and dinner. Many of us decided to play a huge game of tennis, which to say the least was a very eventful match; many of the hits did not quite go in the direction intended, causing them to travel over the tops of roofs and onto the other side of the centre boundary, hopefully not hitting anyone on their way down.
Our second day entailed our travel to two other sites, including Millington Beck and Pocklington Beck in order for us to collect the final investigation data using the techniques we had learned on the previous day. Each group chose a site along the river within agreed boundaries and set out their equipment to carry out the investigation. Using 40x40 cm quadrats each group chose four spots in the stream where they were to take the four sets of data collection. The places that each group chose depended upon the sampling method that each chose, based on which they thought would provide the most representative data to support a conclusion in relation to our question.
All groups carried out kick sampling for 10 seconds at each of their chosen places, during which sediment, and hopefully invertebrates living along the river bed, would be pushed into the sampling net that was held at the base of the quadrat. Once the materials had been caught we removed any excess bed load that didn’t hold invertebrates and placed our finding in the white trays we had partly filled with water. We all then began to try and distinguish which species we had found
and the number of each. One of the main aims was to
identify the indicator species between the two areas which included fresh water shrimp and mayfly larvae; this information allowed us to determine the water quality at each site. Our second aim was to identify the variety of invertebrates present in the samples we had taken to highlight the impact of sewage effluent on the biodiversity of invertebrates.
As soon as we had finished identifying the range and number of invertebrates that we had collected, we
were then able to use this data to carry out a statistical test to determine whether our results gave a significant difference to allow us to conclude that to a large
extent there is a correlation between the two factors. Our investigation showed that treated sewage effluent did have, as you might imagine, some effect on the biodiversity of the stream, but the impact was not as big as we had thought, with the streams recovering quickly once we were 500m downstream of the outfall. All in
all we had an interesting experience, made all the better by the lovely spring weather.
  Alisha Bhandari, Year 12

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