Activity 4
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Rocky Shore
Intertidal
Survey
Marine
Ecology
LEVEL 1
The seashore will give you a taste of the diversity of life in the sea. The transition from
a fully aquatic marine environment to fully terrestrial conditions occurs within a few
hundred meters at the most and often less than 10m. Therefore the shore is a sharp
environmental gradient. Neither the seaweeds nor the animals found on the beach are
scattered haphazardly over the shore! Instead they occur in distinct zones -
i.e. seashore zonation - you will notice species occurring in bands along the shore.
The major underlying variables influencing the distribution of shore plants and animals
are height on the shore in relation to the tide level (“Tidal height”) and exposure to
wave action (“Exposure”). Both of these can be termed as environmental stresses.
This means that it is very often possible to describe the distribution of a species on a
shore in relation to a stress such as the tidal height.
Here we will show you how to carry out a very simple transect down the shore
examining the abundance of rocky shore organisms and how to analyse these results.
[Sample answers are provided to allow students who do not have access to the shore to
analyse a data set.]
First we must quickly go over the basics:
Choosing a transect A transect is a slice down the shore through the different zones. It is subdivided into
stations, or sampling positions , where plants and animals are counted and studied. If
possible choose a shore of unbroken bedrock which gently slopes seawards.
Here we will examine only 3 stations along a transect - one in each of the three main
zones - upper, mid and lower shore. These zones can be identified by the different
seaweed species present or by visiting the shore at extreme low tide to determine the
lower shore and then dividing the shore into three sections.
Funding was provided by the Heritage Council in Ireland to try and test the intertidal survey methods
with two coastal schools in Ireland. The surveys were carried under the supervision of two marine
biologists from EcoServe and Marine Dimensions under the project title InterEST.
Activity 4
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Intertidal
Survey
Marine
Ecology
Levelling the shore The simplest, cheapest and least accurate method but sufficient for this study is to use
two cane poles of 1.5 and 1m. By sighting from the 1m pole to the top of the 1.5m pole
and hence to the sea horizon so that all three are level, gives a vertical drop of 0.5m.
Some red insulating tape at the top and at 0.5m intervals is a help.
horizon
1.5m cane
1m
0.5m difference
An example of a shore profile with 3 different transects.
Activity 4
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Intertidal
Survey
Marine
Ecology
Assessing Abundance There are two kinds of sampling: destructive and non-destructive. In destructive
sampling, plants and animals are removed from quadrats on the shore. Non-destructive
sampling is preferable and is used here. Where the majority of species are identified in
the field.
Don't just count the species present - OBSERVE them! Consider the role of these spe-
cies and note what the species is doing:
• Is it stuck to the rock, or moving?
• Is it interacting (perhaps feeding on) another species?
• How do you think this species feeds?
• Make notes on these aspects alongside your records for each station.
The abundance of each species down the shore helps to reveal relationships between
the organisms and the physical character of the shore.
