A TRIP to the Lake District highlighted the problems faced when hot weather co-incides with lots of visitors.

The presence of human sewage has to be disposed of by water treatment but the breakdown of waste matter uses up lots of oxygen. Hot weather brings with it a problem because cold water holds more oxygen than warmer water.

Put these two things together and you have a problem. Aquatic animals die, and water weeds and microscopic algae build up, and as these decay the lakes and reservoirs become poisonous. This shows just how important sewage treatment works are. Next time you complain about water rates, give a thought to the cost of building and maintaining these works. I passed the Tower Wood treatment works on the banks of Windermere. The water looked clear and the tourists aboard a steamer would be sailing through clear water and with no nasty smell.

FOOD FOR THOUGHT

I get a bit fed up sometimes when people say that all nature is cruel. With very few exceptions – human beings are one – animals do not kill for any other reason except to feed.

Nature works on food chains. Firstly plants produce food from sunlight, carbon dioxide and the heat of the sun. Small animals feed on these plants and larger animals feed on the smaller ones. The top predators like lions and tigers are called cruel. They are not - they are just hungry.

Every where you look you can see food chains in action and a good example is in a reservoir or a lake. It works like this:- Sunlight>Tiny plants>small aninmals>fish like the roach>top predator such as the pike.

Pike can grow to a weight of more than 30 pounds. No wonder they eat a lot but all they are is hungry. Imagine how you would feel if you had nothing to eat for a week!

DAPHNIA AND CYCLOPS

When I was working as a fresh water biologist I was lucky to be able to study microscopic plants and animals and had access to the equipment needed to photograph them. In the recent hot weather I did a pond dip on the Leeds and Liverpool Canal near Hapton. The sample of water was not clear but full of little creatures. They provide food for larger animals, especially fish.

One was called Daphnia also known as the water flea – it gets this name because of its jerky movement. Those who keep fish in tanks at home know of the water flea because these can be bought in huge numbers from pet shops.

Another lovely animal found all over Britain is called Cyclops because it has one eye. Both these species are so delicate thet you can clearly see their internal organs. The more I see of these fresh water mini-beasts the more that I realise just how wonderful nature is. These two animals are crustaceans and are related to crabs, lobsters and crayfish.