AN INVESTIGATION OF THE DIFFERENT SPECIES OF MAYFLY WITHIN THE POOL & RIFFLE

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OYINKAN ALLI        AS BIOLOGY COURSEWORK        25/04/06

AN INVESTIGATION OF THE DIFFERENT SPECIES OF MAYFLY WITHIN THE POOL & RIFFLE

AIM:

I am going to investigate the different species of Mayfly within the pool and riffle. I am going to create tables to show results from my investigation. I am also going to draw graphs to show the distribution of Mayfly Nymphs within the pools & riffles.

NULL HYPOTHESIS:

There is no significant difference in numbers of Mayfly Nymphs found within the riffles and pools.

ALTERNATE HYPOTHESIS:

There is a significant difference in numbers of Mayfly Nymphs found in the riffles and pools.

STREAM:

Data was collected from Nant Iago (James Stream) which is situated in St Mary's Vale. It is surrounded by Beech woodland. The source of the stream is the Sugar Loaf Mountain. It also contains peaty soils that are slightly acidic.

Many erosive streams receive most of their energy from organic matter washed into the stream, largely as leaf litter. The litter is processed to carbon dioxide by a succession of microrganisms and animals, which deal with successively smaller particles of it in a continuous sequence, as it is moved downstream. This is common where the stream is bordered by gallery forest

A flowing freshwater stream is all business. It rushes forward. If it slows at all, it is just to create small whirlpools or eddies and then it’s back on down the mountain. It makes its bed on gravel or hard rock. Its water is cool, sometimes painfully cold, especially in the spring when the stream is brimming with newly-melted snow.

A stream is not like a river. A stream’s banks follow the straight and narrow. No playful meandering curves, no muddy bottom, no sunny, quiet shores. A river is a stream without the push.

Animals that live in a stream are adapted to life in the fast lane. Brook trout have strong, streamlined bodies and powerful tail fins that can push against the current. These fish need the cold, oxygen-rich water of a flowing stream in order to thrive.

 Shade is very important in keeping the stream cold. Atlantic salmon are famous for their ability to buck the current. They swim upstream in spring in order to lay their eggs on the gravel bottom where they were born. Where man-made dams block their route, they will dash themselves to death against the concrete walls trying to leap over them.

Other animals adapt to the swift current. Black fly larvae attach their rear ends to the underside of rocks by tiny hooks. If they lose their foothold (so to speak), they can lasso another rock with silken threads. Caddis fly larvae fashion durable homes from sand grains, leaf pieces, or grasses.

In rivers and streams, the water moves in one direction, though the flow rate may vary from very slow to extremely fast. In a given stretch of a river, there is continual exchange of water, so that events at some distance upstream can affect the river much lower down. Movement of water sometimes creates turbulence, so mixing occurs more readily than in static waters. Often this movement considerably increases the oxygenation of water.

The normal nutrient status depends closely on the bedrock, soil and vegetation of the surrounding catchment area. Water that is relatively poor in nutrients is described as oligotrophic, whereas intermediate nutrients are described as eutrophic. This classification of nutrients refers mainly to levels of inorganic nitrogen and phosphorus, although other mineral elements are also important to aquatic organisms. Higher nutrient levels are likely to support high productivity in terms of biomass within the water environment. Organic compounds found in water are derived mainly from decomposition of plants and detritus. They nay include proteins, carbohydrates and fats as well as more complex particles of organic matter, which are sometimes suspended rather than dissolved in the water.

SOURCE: Freshwater Life, John Clegg


MAYFLY NYMPHS

MAYFLY NYMPHS

Cylindrical body or flattened with pale-like or filamentous gills arranged laterally or dorso-laterally along abdomen with three tails.

They are only found in very clean water containing lots of oxygen. They absorb oxygen from the water through their gills which are plate-like structures attached to the sides of the abdominal region.

They walk on sediments and occasionally swim. They often hide under rocks.

They are herbivores, so they eat water plants and tiny algae. They are eaten by water spiders, newts, and damselfly and dragonfly nymphs.

They undergo incomplete metamorphosis. (Egg-nymph-adult). The nymphs may take from two months to two years before they swim to the water surface and shed their nymphal skin to emerge as a winged fly.

They are seen in the spring.

They are 3-30 mm long

SOURCE: http://www.naturegrid.org.uk/biodiversity/invert/mayfly.html

SWIMMING MAYFLY

They are small with more less cylindrical   spindle shaped bodies and delicate legs. The cerci (tail) are provided with numerous hairs and are used in swimming.

FLAT MAYFLY

Parts of the body and limbs are flattened. The claws on its feet are particularly strong for clinging to stones in fast flowing water. (Found in swift flowing water mainly mountain streams & at edges of lakes)

The body is flat with a very broad head and femora. Gills consist of flat plate and tuft of filaments. Large or moderate size found clinging closely to stones.

BURROWING MAYFLY

Live in tunnels which they make in sandy mud near the edge of streams and small rivers. Only become visible when the mud is scooped up on to the bank & examined. They only swim in muddy waters if the light is not too intense. Too much light is detrimental.

Gills are held over the back in life. Mandibles project in front of the head.

EPHEMERELLIDAE

These genera are especially abundant in the trout streams of eastern North America. The genera may be distinguished in the naiad stage by details of the maxillae and by the presence of long intersegmental setae on the apical half of the caudal filaments (the "tails"). Adults emerge in the spring through early summer; nymphs collected in September and October are about halfway through their nymphal stages.

SOURCE: Animal Life In Freshwater by Helen Mellanby, 1983 sixth edition, publisher: Methuen & Co Ltd.

SOURCE: A Guide to Freshwater Invertebrate Animals, Published in 1959 by Longman House

ABIOTIC FACTORS IN FRESHWATER THAT AFFECT MAYFLY NYMPHS

PH

Low pH can upset oxygen uptake through the gills (mayfly nymphs) and ion regulation. Values below 5.0 cause an alteration in the permeability of the gills, which allows H+ ions to move in and sodium ions (Na+) to leak out.

SUBSTRATE

The nature of the substrate is dependent to some extent both on water velocity and geology. Depositing substrates are the normal in slow flowing and still water, where fine particulate matter and detritus settle out. The silts and muds deposited are often low in dissolved oxygen due to the decomposition of organic matter by micro-organisms. Substrate size increases with increased water velocity, providing and increasingly complex series of microhabitats. Beyond a certain velocity the stream bed becomes unstable and at very high velocities only large boulders and sheets of rocks will be present, leading to a reduction in diversity of microhabitats. The size and shape of the rocks forming the bed of the stream will also depend on how easily weathered the underlying rocks are.

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TEMPERATURE

Water is a poor conductor of heat. Because of its high specific heat, it takes longer time to warm up than air and is slower in cooling. So fluctuations in temperature are neither great nor violent in water is in air, which is important to creatures that are dependent on their surroundings for body temp.

An important indirect effect pf temperature on freshwater organisms is the varying quantities of oxygen that water can hold in solution as it becomes warmer/colder. Each species has an optimum temperature at which lives can only survive within a fixed temperature range. Temperature ...

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**** A quite complex investigation reported in full but analysis & evaluation could be more detailed. One significant mistake in the statistical analysis.