At some expense, I have subscribed to the international Freshwater Watch citizen science programme, as this gives nutrient sampling kit for 12 months. Previously, we used the free Thames River Watch and other one-off citizen science schemes, but this restricted us to their programme for one-off samples, preventing enough sampling for a good overview. The anglers have sampled lake water quality, but somewhat erratically. The kit arrived a bit late and my first sample was made on the 4th, rather than in January, when it theoretically began. The results were interesting, as the phosphate concentration was the highest I have seen in the 30 samples taken since 2017 and well into the range regarded as nutrient pollution. Although sewage or agricultural runoff are the usual causes of high phosphate, in urban areas road runoff can contribute. No regular sampling is undertaken of the tributaries of the lake. In contrast, the nitrate pollution was low and not indicative of pollution, so there seemed to be a source which adds phosphate but not nitrate. Feeding excess bread, or other food, to the birds is ruled out on those grounds, but it's possible that birds feeding on the grassland and returning to the lake to defecate could mimic sewage pollution. We can also rule out atmospheric deposition, as this would bring nitrates, not phosphates. So, we don't know the source of our high phosphate. We should, and it's reprehensible that AELTC, who own land uphill from the lake and have a drain going direct to the lake, don't admit to carrying out any monitoring. Our lake would be in a terrible mess, were it not for the low concentration of nitrogen constituting a limiting nutrient here.
Then, I did the second sample at the end of the month. The results were startlingly different. Whilst nitrates remained low, the phosphates had come right down, suggesting that the high values were from some brief cause, perhaps an otherwise unreported pollution incident or a seasonal factor coming to an end. So the next months' results are eagerly awaited.
This month reflects the end of winter and first signs of spring. The Blackthorn flowers and Hazel catkins were dying back and most Ivy fruit had been consumed, despite low numbers of the Blackbirds that consume most of them. By the end of the month Alders were flowering, Hawthorn buds were bursting and the first few Hawthorn flowers were seen. Weeping willows are the first trees to break bud and there were fresh leaves on them by the end of the month.
It seems that there are few small fish to be had in the lake, as there were still no Great Crested Grebes there yet again.
