I was delighted recently to have been invited by the Alva Glen Heritage Trust to give a presentation to volunteers on the amazing underwater life that occurs in the Alva Burn.

The Trust is a fantastic organisation, set up to develop the spirit of the local community by restoring and regenerating Alva Glen. The work of their volunteers is an inspiring example of how ‘people power’ can make a real difference when it comes to protecting our precious landscape.

The tumbling burn that flows through Alva Glen is like a sparkling sliver of life, which is home to a wide range of creatures, including dippers, grey wagtails and trout. As part of my presentation to the group, we surveyed the burn for invertebrates using a technique called ‘kick sampling’. This involves kicking the stony riverbed with wader-clad feet, and then catching in a net any invertebrates stirred-up into the water.

As we emptied the net into the examination tray, a wonderful plethora of life unfolded before us. There were the larvae (nymphs) of mayflies, stoneflies and caddisflies, as well as a water flea. These invertebrates are the engine room of the burn, the driving force that supports everything else – food for birds, fish and other creatures. They provide many other ecological benefits, too, including the recycling of nutrients.

Mayfly, stonefly and caddisfly larvae live on the bed of the burn, before eventually developing into winged flies that will mate and lay their eggs in the water to start the next generation of life. These nymphs or larvae are well adapted to living in the burn and have strangely flattened bodies to enable them to cope with fast-flowing water and to creep under stones.

The stonefly nymph was a good find, for they are especially sensitive to water pollution, so where they occur, all is well with the water course. Like the mayflies and caddisflies, they spend virtually all their life – up to two years – in the underwater stage, grazing algae and vegetarian detritus, or preying upon other tiny creatures, depending on species. Then, they crawl out of the water and moult one last time, unveiling from within this nymphal skin a winged adult fly. It is a true miracle and I find the physiological changes that take place, transforming from one form of creature to another, a spellbinding wonder of nature.

The spectacular aerial mating of mayflies involve hundreds or even thousands of individuals all swirling around at the same time. They are always a joy to watch on warm evenings when engaged in their hypnotic mating flights, dipping up and down in the air on impossibly fragile wings. It is hard to imagine that these beautiful and delicate insects spend most of their life underwater as crawling bugs.

The sampling session on the Alva Burn had opened our eyes to a whole new world; as exciting as any dramas played out on the African plains, a place where nymphs of various species engage in battles, preying upon each other, and themselves being feasted upon by trout, dippers and other creatures.