How to display information from transects of the rocky seashore.

Counting the animals and plants in quadrats along the line of a transect generates a lot of numbers, making it difficult to see trends and compare different parts of the shore. The solution is to present the data visually as a kite diagram.

Counting animals and plants on the shore

When the 50cm square quadrat is placed on the shore (see ‘how to do a transect’) the organisms inside the square need to be counted. This is easy for animals such as limpets, but for others – such as barnacles - there might be too many to count accurately in the time available. For barnacle counting it is probably best to count only a 10cm square. With the larger shore algae (Fucus vesiculosus, Fucus serratus etc.) the best thing to do is to forget numbers and estimate percentage cover – ignore the fronds and estimate the percentage of rock surface covered by the holdfast. Winkles will probably be hiding in the fronds of the weed, so it will be necessary to give the seaweed a good shake before counting them.

ACFOR Scales

Is the species abundant, common, frequent, occasional or rare? (ACFOR). Numbers (of animals) and percentage cover (of plants) can be given an ACFOR scale of 1 – 5 to help present results graphically and compare different parts of the shore. There are many ways to do this – such as:

• Seaweeds

More than 30% cover = A = 5

5 – 29% cover = C = 4

Less than 5% cover = F = 3

Scattered around the area (but none in the quadrat) = O = 2

Rare at that level on the shore = R = 1

• Barnacles

More than 100 per 10cm square = A = 5

10 – 99 per 10cm square = C = 4

1 – 9 per 10cm square = F = 3

1 – 25 in the whole 50cm square = O = 2

Just a few visible at this level of the shore = R = 1

Kite Diagram

Use graph paper and begin by drawing a sketch of the shore profile across the bottom. Next draw a horizontal line above this and locate the stations – mark a vertical bar at each station for the first species (5 squares above and 5 below for Abundant, 4 for Common etc.). Then join the tops and bottoms of these bars. Not present will be a point on the horizontal line, so the diagram that results will have a shape something like a kite (hence ‘kite diagram’!). That is the profile and one species done. Draw another horizontal line and enter the data for the next species, and so on.

Zonation

The finished kite diagrams for several transects can now be compared, and organisms that are restricted to particular zones will be obvious. The final stage is to try to explain this zonation!

Other articles by John Blatchford