The Barton team went back to the lakes in early September 2014 to carry out a vegetation survey. Despite the bad discoveries regarding the invasive species, the surprises were not over yet.
Again the weather allowed the team to work without problems for the whole day on the boat, surveying a total of 6 transects across all the lakes; in particular 2 transects were created in Lake A, 1 transect in Lake B, 2 in Lake C and 1 in Lake D (Site map). The Lake Anew (in red in the map) unfortunately couldn’t be fully investigated due to a time limit and the delay in its flooding. This latter decision was taken by the Hanson-Heidelberg Cement group after breeding birds were found in the area and they would have been affected by the water rise.
The vegetation survey was planned to be carried out creating 2 transects in each lake; however Lake B showed that it didn’t fully required a second transect because of its bed reaching the depth of approximately 2.5-3m with a very long slope, therefore we assumed that 1 transect could provide us a good representation of its vegetation cover. Different situation happened in Lake D which unfortunately was used by boaters for leisure activities and on that day it was not feasible for the team to safely reach another area of the lake for a second transect.
As mentioned above the results of the survey were not deprived of surprises. The survey was carried out using a double-headed rake (length 25cm), the depth was measured using a portable depth sounder and the light penetration was measured using a Secchi Disk. Of particular interest was eutrophic Lake C which, with its 50cm of light penetration depth a meximum depth of 6 meters and surprisingly the presence of the Short-leaved Water-starwort (Callitriche truncata) which is very local across England (Source: NBN Gateway – https://data.nbn.org.uk/Taxa/NBNSYS0000003621). Furthermore despite its poor light penetration and its water level fluctuations, the lake showed the highest number of species of aquatic plants if compared with the other lakes, even if all at very low abundances.
The rest of the lakes showed a quite spread and substantial proportion of Nuttall’s Pondweed (Elodea nuttallii) which showed highest values in all the sites. Another important parameter assessed during the survey was the colonisation depth. This parameter (highly connected to the light penetration) is an indicator of the status of the lake, because a well established vegetation community across the lake bed is going to positively affect the whole food chain from the benthic community of detritivorous, filter feeders and predators; till the top predators (fish and birds). In the Barton lakes the colonisation depth varied greatly, highlighting the issue of the lakes morphology. In particular 3 lakes were recorded being 5-6m deep with very steep slopes; only 1 (Lake B) showed a depth suitable for a shallow lake with the bottom slowly reaching the maximum depth of 2-3m.
As visible from the graph Lake C showed a colonisation depth restricted to the top 50cm of water (confirmed also by the Secchi Disk measurement), and only Lake B presented vegetation cover along the whole transect even if a big drop in the cover percentage was recorded after 15 meters. The data not quantitatively recorded was the actual length of the transects; however few observation were made on site. Lake A and Lake C both presented a submerged cliff only few meters off the shore (less the 5 meters); Lake B didn’t show the presence of a steep cliff along the whole transect which covered approximately 30 meters towards the centre of the lake. Ultimately Lake D, similarly to Lake A and C, presented a steep cliff at about 10 meters off the shore.
More updates soon about the results of the Water Chemistry and the final presentation for the Quarry Life Award.