Ponds

The plants in the pond make food which is eaten by the smaller animals in the pond such as snails and insects. These plant-eating animals are herbivores. They in turn are eaten by larger animals such as frogs and fish. These meat-eating animals are carnivores. They too can become the prey of one of the largest pond predators - the heron.
Food passes through a chain of living things - the plants, the plant-eaters and the meat-eaters. Ecologists link these living things together by the food they eat and call them food chains.
One example of a food chain in a pond is
Water plant > snail > fish.

Water lilies only open in an afternoon. Why?
Water lily flowers open and close over a twenty-four hour period. They close in late afternoon and open again in the following afternoon. They do this because afternoons are warmer than mornings and there is a greater chance of insects flying over the water during the afternoon to pollinate them. The surface of the water can be a dangerous place for a flower. It may sink if it takes in too much water. This can happen when wind blows waves across the pond or if there is a downpour of rain. The plant is adapted to this by being sensitive to weather conditions and does not open its flowers at all on cold, cloudy days when there is a chance water could enter them.
How can you tell a rush from a sedge and a reed?
All three plants can grow in the wet soil on the edges of ponds. A rush and a sedge form spiky clumps about a metre high. The rush has a cylindrical stem which ends in a point, and a cluster of brown flowers stick out as a tuft near the top of the stem. If you snap open a stem you will see that it is filled with spongy material. A sedge has a three-sided stem. If you snap one open you will see the triangular shape more clearly and also find that the stem is solid. Reeds grow about two metres high. They have cylindrical hollow stems and flower heads like giant grasses. This is because reeds are, in fact, giant grasses.
You don't find plants growing on the water surface or round the edges in winter. Why?
Most plants avoid the ice. Plants contain a large amount of water in their bodies. When water changes to ice it expands. The ice forming inside the plant would push on the living materials in the plant and tear them up. Water plants avoid this by keeping away from where ice forms. The shoots of the plants growing on the pond edge simply die, but the plant survives as a root or an underground stem until the following year.
Plants which live on the water surface in spring and summer sink to the bottom during the winter so they are clear of the ice sheet that forms on the surface. The water soldier takes substances from the water and makes a material called lime on its leaves. This makes the plant heavy so it sinks. The frogbit makes heavy buds on its stems which sink in the autumn. Pond plants are sensitive to the changes in light and temperature in the spring and respond by growing back to the surface.
How do plants that live underwater differ from those that live above water?
They do not have strong fibres in their stems to hold them up but rely on the water to support them. If you take a plant out of water it will collapse. Underwater plants also have feather-like leaves. This gives them a large surface for taking in water directly from the pond water and using it to make food. Plants such as water crowfoot, which has an underwater stem that grows out above the pond surface, have two kinds of leaves. Feathery leaves grow below the water surface and flat broad leaves develop above the water surface and float on it. Each kind is adapted to the conditions around it so that it can make food.


What types of fish are found in ponds?
Common fish include the carp, tench and pike. The carp is similar to a goldfish but has a brown body and can reach a length of 75cm. The tench can be told from a carp by its green brown body and thick tail. It is usually reaches a length of between 30-50cm. Both fish search the bottom of the pond for food. They have fleshy tentacles around their mouths which they use to feel in the mud for food such as snails and worms.
The pike looks like a long, scaly cylinder with a snout that looks like a duck's beak. It can reach 130cm in length and has sharp teeth and long jaws which it uses like a crocodile to snap up its food. Then pike feeds on other fish, frogs and will even pull down floating water birds and eat them.
All the fish share a similar adaptation. They have darker backs and lighter undersides. This is called counter-shading and makes the fish difficult to see. The dark back blends in with the pond mud so they are difficult for predators to see from above. The light-coloured underside blends in with the cloudy sky above the pond so they are also difficult to see by predators below them.
What kinds of amphibians may you find in a pond?
You may find frogs, toads and newts. Frogs and toads have a similar body shape with eyes on the tops of their heads, but they have different skins. The skin of a frog is green and slimy. The skin of a toad is brown and warty. The newt has a body shaped like that of a lizard but does not have scales. It has a smooth skin. A newt may have a crest all the way down its back to the tip of its tail. Amphibians need water for the early stage of their life cycle. They all lay jelly-covered eggs which hatch into tadpoles. Frogs lay their eggs in clumps known as frog spawn. Toads lay their eggs in strings of jelly and newts lay their eggs one at a time and hide each one by curling it up in the leaf of a water plant.

What birds may you find on a pond?
Two kinds of duck may be found on ponds. They are the mallard and the teal. The mallard is the larger bird. The male mallard has a green head. The female is brown, but both sexes have a purple patch on their wing. The male teal has a brown head with a green stripe through its eye. The female is brown. Neither sex has a purple wing patch. The ducks have webbed feet to help push themselves through the water but also come out onto the mud round the pond.
Both kinds of ducks are plant and meat-eaters, that is they are omnivores. They feed on the leaves, seeds and buds of water plants and also on insects, worms and crustaceans. The coot and the moorhen are both black birds, but the moorhen has a red and yellow beak while the coot has a white patch above a white beak. They are omnivores like the ducks but have unwebbed feet with long toes and may search for food around the edges of the pond as well as in the water. The heron is a very tall grey and white bird with a long, yellow, spear - like bill. It is a carnivore and visits many ponds to feed on fish, frogs, water voles and rats. It has long legs and waders out from the shore to catch its prey.


What are the specks you can see swimming and jerking about in a jar of pond water?
The largest ones are water fleas. They get their name from the way they move, which is jerky like a flea. They are crustaceans, not insects. Water fleas have rounded bodies and may be green, brown or red.
The copepods (sorry, they don't have a common name!) are even smaller crustaceans with a body like an exclamation mark without the dot. Many copepods may have two bags of eggs hanging from their side. Both types of crustacean feed on even smaller, often microscopic, plant-like algae.