Monitoring nutrient levels in gravel pits


So here we are a showery weekend in July and we have a batch of water sampling kits to monitor nutrient levels in freshwater habitats locally. We started this project some time ago and this is our second batch of water sampling kits.

The technique is fairly simple, each tube is secured with a small green tab, this, when removed, leaves a hole. The air is squeezed out of the tube, which is then inserted in a sample of the water. Once the water has been sucked into the tube, the contents are shaken and the colour change develops over 3 minutes for nitrates and five minutes for phosphates. The colour produced corresponds to a range of nitrates or phosphates in the water. A GPS location for the water body and a photograph of each area sampled and the process is complete

We decided this weekend was time to sample the gravel pits at Attenborough Nature reserve so we set off to collect some samples and get some results.

First was the sailing pit away from the River Trant and deep we failed to see much algal growth and we were hopeful levels of nutrient would be low. However, nitrate levels were higher than we had expected at 2.5 ppm whilst phosphate levels were much lower at 0.02-0.05ppm ( parts per million).

SAILING PITIMG_5738We then headed towards the main centre and church pond. This pond is away from the river and therefore less likely to have nitrate runoff from farmland.  Indeed here the nitrate levels were less than 0.2ppm and the phosphate levels were less than 0.02ppm making this pond very beneficial to q=aquatic insects that fail to thrive in water bodies with higher nutrient levels. We then met some fellow scientists who informed us that this pond is groundwater fed and consequently does not receive water from sewage overflow or from the river.

CHURCH PONDIMG_5740Tween pond is opposite the church pond and we sampled that pond next. A young Canada goose with a broken wing and damaged foot was struggling in the shallows. We reported it rather than let it suffer. Nitrate levels were much higher here at 2.5ppm whereas phosphate levels were still low at less than 0.02ppm. We did notice some algae around the edges and a number of ducks and swans were on the water. We suspected that the algae had removed nitrates from the water in order to grow. However, Tween pond is nearer the River Trent and could be receiving excessive water from the Trent following heavy rain. We were disturbed with a Southern Hawker that came to investigate us.

TWEEN POND

IMG_5739

At the corner, there is a smaller pond that leads to a ditch beside the path. This pond is next to the house called Ireton House. One of Oliver Cromwell’s generals was Ireton. Here there is a multitude of ducks, some wild and some definitely domesticated. We thought the nutrient levels would be high in this pond from all the duck faeces.We were wrong the nitrate levels were less than 0.2ppm whilst the phosphate levels were higher at 0.2-0.5ppm. Possible the algae we found could have taken up surplus nitrates from their growth. A common blue damselfly was perched up and further examination revealed a blue tailed damselfly nearby.

IRETON POND

IMG_5741

 

Main pond nitrates were the same as the sailing pit 2-5ppm and phosphate levels were also higher at 0.2-0.5ppm. Main pond is huge but it connects with the river through a sluice so excess river water can be channelled away to prevent flooding.

MAIN POND

IMG_5742More common blue damselflies and blue tailed damselflies were perched up and several different bee species were busy.  These included Bombus pascorum the common carder, Bombus hypnorum the tree bumblebee and Apis mellifera the honey bee.

We headed down towards Clifton pit the pit with the two hides beside the banks. The nitrate level was less than 0.2ppm whilst the phosphate level was 0.05-1ppm. The lake is very deep and despite the number of birds who make their home on it, they are not significantly increasing the nitrate level in the water. We had been told that this lake was also ground water fed.

 CLIFTON POND

IMG_5743Finally, we drove to the railway crossing on Meadow Lane to take samples from Beeston pond We had been warned that the nutrient levels were likely to be very high here due to an overflow sewage outlet nearby. However, nitrate levels were less than 0.2 and phosphate levels were 0.05-0.1 so we were pleasantly surprised. We watched a warbler making its way through the reeds for a few minutes before returning home to input the data.

BEESTON POND

 

IMG_5744

Here is the map of the site Map – Attenborough Nature Reserve (1)

 

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