As a UNESCO Associated School we - along with schools around the world- are testing the water in our local river, as part of theWorld's Biggest Chemistry Experiment. Partly it is to show how much fun science is and partly to show how important our rivers and waterways are. The River Ely flows past our school and down into Cardiff Bay with the River Taff. Cardiff Bay is managed by Cardiff Harbour Authority who do lots of water quality tests, in fact we learnt that they have buoys floating in the bay that test the water quality ever 15 minutes every day- wow! So we asked if we could visit and find out more.

We were met by the Environmental Officer Mr Hall who kindly showed us the lab where he works. It was full of sample tubs which he uses to analyse the creatures living in the mud in the Bay. There were also lots of tubes that are the ones suspended under the automatic water quality testing buoys moored around the bay. He and the team also carry out their own more detailed tests to supplement and check those carried out by the buoys.

When Mr Hall showed us the results of the oxygen dissolved in the water we could see peaks and troughs and he asked if we knew why that was- we did not. Some of the oxygen dissolves by diffusion from the surrounding air; aeration of water that has tumbled over falls and rapids. But he said that the variation in the lower parts of the river and bay was because it was night and day; and during the day when there is sunlight the little plants produce oxygen as a by product of photosynthesis. Some scientists think as much as three- quarters of the earth’s oxygen supply is produced by phytoplankton in the oceans. So it is very important to us not to pollute the waters as we have in the past.

Mr Hall told us that the job of his team is to look after the animals and creatures in the bay and keep them all in balance. We asked him some questions.

WHAT FISH ARE IN THE BAY, ARE THERE ANY PIRANAHS? "There are no Piranhas and they are not that dangerous as the movies make out. There are Roach, Rod, Bream, Sticklebacks, and Salmon and sea bream pass trough the bay too using the salmon jumps especially left in the barrage for these migratory fish to leap over a series of little steps and pools right up to the level of the bay and then swim up river."

WHAT IS THE STRANGEST THING YOU HAVE FOUND IN THE BAY? "We found a dead horse and bits of cars that get washed down the rivers. But the strangest creatures I think are the eels we often find them in the mud and I saw one wrapping itself around a cormorant that was trying to eat it" (You can see one such story on the BBC or in the Sun)

DO YOU LIKE YOUR JOB? Yes, I have been doing this job for 9 years now.

HOW OFTEN DO YOU GO OUT IN THE BAY? "There is a team of 7 of us and we go out 2 to 3 times a week every week even if it is snowing or raining to make our tests and check on the buoys and make sure that they are working okay."

HOW OFTEN ARE THE ARE AERATORS USED? "They are used about 1/2 an hour a day during the Winter. There are 600 'bubblers' around the bay and they pump water not air but they cause the water to circulate vertically so that the top layers near the sun and full of oxygen and brought down to the bottom of the river.

HOW MANY BUOYS ARE THER IN THE BAY? "We have 9 water quality buoys but there are lots of different types you can see. Some are navigation buoys to tell people where it is safe to sail your yatch or warn of wrecks or sandbanks hidden below the water; some are mooring buoys which you can tie your boat to; some have signs with the speed limits on."

You can watch the Cardiff bay webcam here. The Harbour Authority website is here

We carried out the simple water tests, but forgot our collection net so we did not get many samples of the many creatures that live in the bay