Water-net

Firstly, thank you all so much for the stars and hearts for yesterday's dragonfly. I have to admit I was very pleased to have captured some good images of flying dragonflies, after many years of failure!

Today's image is perhaps less attractive, but nonetheless interesting. Pete brought back a large sample of Hydrodictyon reticulatum from a lake in Surrey that he was surveying yesterday.

This is a very invasive nuisance alga, and is commonly known as 'water-net' reflecting the net-like structure of its sack or membrane-like colonies. The individual cells are quite large for an alga, and join with two or three adjacent cells to form polygonal shapes, primarily hexagons, but with a smattering of pentagons and heptagons.

Over the past 20 years it has become more common and widely distributed in ponds, lakes and rivers in the British Isles. Water-net is a serious nuisance because it clogs waterways and irrigation ditches, taints potable water, causes economic losses to trout fisheries, smothers aquatic plants and fauna and adversely impacts boating, fishing, swimming and tourism.

The rapid spread of the water-net is believed to be a response to elevated and extended summer water temperatures and low river flows caused by climate change. The extensive mats start to break up un the autumn and have usually gone by the end of September. This one is already looking a little worse for wear, with a number of tears in its structure. Perhaps one day I'll be able to photograph one in better condition.