Download Several projects have been carried out over the past 20 years into

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An Investigation into the Abundance of Intertidal Flora and
Fauna in the Fal Estuary, Cornwall
ABSTRACT
Several projects have been carried out over the past 20 years into the abundance of flora and
fauna within the intertidal zone of the shore line. This project will record and interpret the
changes in the quality and quantity of organisms over the past 20 years when compared to a
study undertaken in 1992 by Dr. Tompsett. The data collected will provide insight into the
key areas of conservation as well as analysing the potential impacts that we are having on
the intertidal zone. The method used was the same as Pamella Tompsetts’ stated in her
report. The statistical results show that there is insufficient data to reject the null hypothesis
that there is a change of abundance within 20 years. However, the statistical analysis of
biodiversity proved to have a significant difference and the biodiversity within the Fal
Estuary has decreased significantly due to the increase use of the Fal commercially and
climate change affecting the water quality and temperature.
Keywords: Fal Estuary, invasive species, biodiversity, climate change, intertidal areas
INTRODUCTION
The UN Convention on Biological Diversity (CBD) defined biodiversity as comprising
ecosystem diversity, species diversity and genetic diversity (Spangenberg, 2007). In many
areas of the world biodiversity is being affected by human disturbances such as; changes in
land cover and use, pollution(examples used are endocrine disrupters, oil, eutrophication),
modification of coastal processes (coastal defences, siltation), invasive species through
mainly through ballast water and fouling on ships’ hulls (Lavoie, et al., 1999) (Harvey, et al.,
2009), unsustainable harvesting of natural resources and climate change affecting sea levels
(Thompson, et al., 2002) (Kappelle, et al., 1999) (Sala, et al., 2000). Some non-native species
can become invasive and negatively impact species already there (Harvey, et al., 2009). A
journal in science magazine by Worm et al (2006) concluded that the loss of marine
biodiversity is increasingly impairing the ocean’s ability to provide food, maintain its water
quality and the ability to recover from distresses.
There are thought to be 10,000 different species travelling around the world in the
ballast water of ships (Drake & Lodge, 2003). The species carried will most likely die before
reaching the port due to the dark, contaminated conditions (Crooks & Soule, 1999). Others
will find it hard to establish their new environment due to being unable to adapt to the new
environment and from competition from native species (Bax, et al., 2003) (Crooks & Soule,
1999). The species that can adapt will populate the port and surrounding areas. In a survey
done in 2011 by William West looking at the invasive species that have been populating the
Fal Estuary it showed Darwin’s barnacle, Eliminus modestus, to be the most abundant
invasive species collectively around the west and east side of the Fal Estuary. This species of
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barnacle also flourished in the 1992 intertidal survey by Dr. P. Tompsett. Although this
species has little negative effect on the native species of barnacle, and so isn’t much of a
threat in the Fal Harbour (Watson, et al., 2005), the invasive species that do effect the native
can have a detrimental effect on not only the biodiversity of the area, but also marine
industries and the human health of the area (Bax, et al., 2003). The invasions of these nonnative species have increased during the last 20 years and will continue to increase over the
next few decades which will also introduce, not only completion to the native species, but
also will introduce pathogens (Thompson, et al., 2002).
The increasing development of the harbour means that natural habitats are being
replaced by man-made structures such as pontoons and pilings (Connell & Glasby, 1999)
(Connell, 2001). Both natural and man-made structures offer habitats for flora and fauna, and
so also offer habitats for the non-native species to settle and populate (Connell, 2001).
Developed and industrialised countries cause a lot of pollution to the surrounding waters
causing chronic effects through eutrophication which can have major effects on the whole
coastline as it affects the water quality of the oceans. Nutrient levels may also rise and have
been implicated in a trend of increasing frequency of decreasing populations of some species
due to toxic algae (Thompson, et al., 2002).
There are gaps in our knowledge about how climate change affects our oceans’ biodiversity.
It is difficult to measure the effects that climate change has on our oceans as it occurs slowly
and interacts with other stress factors already imposed on the environment. In the near future,
greater frequency of environmental extremes is likely. These include large scale weather
events such as El Niño Southern Oscillation events, global changes in sea levels and
temperatures and increases in the frequency of storms, all of which will have a great effect on
rocky shores around the world’s coastlines (Thompson, et al., 2002). Over the next few
decades responses of the communities on the rocky shore will be subtle but will be subject to
a decrease in biodiversity. These small changes can be seen on the intertidal communities and
can be shown by documenting changes in intertidal communities and sea temperature over
time (Cheung, et al., 2009) (Thompson, et al., 2002).
R.D. Sagarin (1999) said that there are changes in the abundance of macroinvertebrate species documented in a rocky intertidal community between surveys in 1931–
1933 and 1993–1996 which are consistent with the predicted effects of recent climate
warming (Sagarin, et al., 1999).
D.R Schiel (2004) said that one of the most commonly predicted effects of global
ocean warming on marine communities is a pole ward shift in the distributional boundaries of
species in relation to seawater temperature. His 18 year sampling study concluded a change
in marine benthic communities with an induced warming of the sea water by a powergenerating station. His results showed that the responses of the species were mostly
unpredicted and strongly coupled to direct effects of temperature on key taxa (Schiel, et al.,
2004).
This prediction of a shift in distribution of species may lead to extinctions in the sub-polar
regions, the tropics and semi- enclosed seas. Invasive species is also predicted to have a
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significant affect in the Arctic and Southern Ocean. This shift and dramatic change in
diversity will imply ecological disturbance that will potentially disrupt the oceans many
cycles and therefore major ecosystems. (Cheung, et al., 2009) (Thomas, et al., 2012)
(National-Science-Foundation, 2013).
In a time where climate change has become one of our most talked about issues more
research is needed to establish the possible increasing effects it has on our oceans, such as,
sediment loads, UV radiation and introduced species on rocky shore communities. This
information could possibly be used to help conserve rocky shores through networks of marine
protected areas (MPA’s) and maybe reduce environmental pollution (Cheung, et al., 2009)
(Pimental, et al., 2005).
This study aims to show a change in distribution and biodiversity within the Fal Estuary over
a 20 year period in comparison with an intertidal survey done in 1992 (Tompsett, et al.,
1992). If there is a significant difference within results then further research into the areas
stated above it could generate input data for predictive models based on climate change
scenarios (Kappelle, et al., 1999).
To do this species population and biodiversity will be recorded on selected sites around the
Fal Estuary. These will be the same, if not similar, sites to the locations tested in the 1992
intertidal report which will cover both rural and urban sites. The results will be converted into
the ACFOR scale of abundance as an indicator, and will be easier to analyze and compare.
This is presented in the following hypothesis: There is no significant difference within 20
years in the population and biodiversity of the intertidal species found around the Fal Estuary.
The sites chosen are shown in table 1.
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Figure 1: GIS Map of the Test Sites in Falmouth (Digimaps, 2013).
METHODS
The field methodology follows that of the 1992 Intertidal Monitoring of Flora and Fauna in
the Fal Estuary Report for the National Rivers Authority (Tompsett et al., 1992).
The same sites will be used as Tompsett's survey but some sites can now not be accessed, and
so sites will be chosen as close as possible to the original sites. All test sites will be recorded
on GPS and plotted on a GIS map in which to accurately be seen shown in figure 1. The GPS
will be taken at the top of each transect line. A photo will also be taken at each transect on
every quadrat to allow for future reference and research at the sites surveyed. On site, date,
time, and weather should be documented. There will be 11 sites on the estuary; Flushing
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West, Trefusis Point, Pendennis Point, Mylor Churchtown, Greatwood Boathouse,
Restronguet Point, Loe Beach, King Harry Ferry West, St. Anthony Amsterdam, St. Just in
Roseland, and Turnaware Point.
Table 1: substrate type of the test sites
Site
1. St. Anthony
Amsterdam
2. St. Just in Roseland
Substrate and shore type
Rocky, exposed
Rocky/pebbles, sheltered
3. Loe Beach
Rocky/pebbles, exposed
4. King Harry Ferry
West
5. Turnaware Point
Rocky/ pebbles, sheltered
6. Greatwood
Boathouse
7. Trefusis Point
Rocky/ granules, exposed
8. Pendennis Point
Rocky, exposed
9. Restronguet Point
Rocky, sheltered
10. Mylor Churchtown
Rocky/ pebbles, exposed
Rocky/pebbles, sheltered
Rocky, exposed
Biodiversity and abundance will be recorded on one quadrat on a line transect at each
site. Quadrats are recorded proceeding down the shore at the intervals to the furthest extent
exposed at extreme low water. If the transect line is 50m or more, measure the quadrats at
every 10m. If the transects are less than 50m then measure quadrats at every 5m. Species are
observed and recorded on the overlaying top layer of algae. Then pull back the algae to reveal
the under layer substrate, any boulders or rocks should be lifted and any species should be
recorded. All substrate moved must be put back so not to disturb their habitat. Particle size on
the substrate is estimated using the categories shown in table 2.
The ACFOR scale of abundance is used to measure the non-native species in each
quadrat. ACFOR stands for Abundant, Common, Frequent, Occasional and Rare. Table 3
shows the number of individuals needed to qualify for each category.
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Table 2: Categories for particle sizes (Tompsett, et al., 1992)
Particle type
Silt and clay
Very fine sand
Fine sand
Medium sand
Coarse sand
Very coarse sand
Granules
Pebbles
Cobbles
Boulders
Size (mm)
<0.06 (remains in suspension when stirred)
0.06-0.1
0.1-0.25
0.25-0.5
0.5-1
1-2
2-4
4-64
64-256
>256
Table 3: ACFOR Scale of Abundance some aspects were adapted (Tompsett, et al., 1992)
Species
Abundant
5
Common
4
Frequent
3
Occasional
2
Rare
1
Lichens
>80%
50-80%
20-50%
10-20%
<10%
Algae
>90%
60-90%
30-60%
5-30%
<5%
Cirripedia
>5/cm2
(300 and
above)
3-5/cm2
(100-299)
1-3/cm2
(70-99)
10-100/dm2
(20-69)
<1/dm2
(0-19)
Patellogastropoda/
Littorinidae
>200/m2
100-200/m2
50-100/m2
10-50/m2
<10/m2
Mytilidae
>80%
50-80%
20-50%
10-20%
<10%
Other invertebrates
>100/m2
50-100/m2
10-50/m2
5-10/m2
<5/m2
The method used to analyze the data converted into the ACFOR scale of abundance
will be the paired t-test. Values are given to the ACFOR scale in which to analyze the data;
Abundant is given 5, Common 4, Frequent 3, Occasional 2 and Rare 1. This method will give
a test statistic to then reject the null hypothesis. If the results are not significantly different
then there was not sufficient evidence to reject the null hypothesis.
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RESULTS
Figure 2: ACFOR score 2013
Figure 3: Biodiversity 2013
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Figure 4: biodiversity 1992
Figure 5: ACFOR score 1992
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DISCUSSION
From the statistical analysis shown in the appendix, there is a significant difference between
the biodiversity of the Fal Estuary in 1992 and the biodiversity in 2013. This proposes the
idea that some change has occurred over the past 20 years. This may be due to the water
quality changing due to the increase of shipping and activities occurring in the Fal Estuary or
even the increase in sewage disposal into the Fal from fouling and other activities that occur.
The Biodiversity over the last 20 years has decreased substantially. This is also a victim of
climate change as this is the main event to occur over the last 20 years in the warming and
water level rising causing species to migrate or die due to not being able to adapt to the sea
water temperature rise.
The statistical test for the ACFOR score of abundance shown in the appendix, shows that
there is insufficient evidence to reject the null hypothesis, and therefore further surveys need
to be done in greater detail to ensure sufficient data which to make a statistical conclusion
and evaluation into the change of abundance over the last 20 years.
In figure 2 the most abundant species in 2013 is in fact the Acorn barnacle which is the same
for the abundance in 1992 showing no significant change meaning that this species has
adapted well to the abiotic changes to its environment. And hasn’t been effected much but the
invasive species in competition with it, which is, Darwins barnacle. In figure 3 it shows this
barnacle to be more abundant in 1992 than it is now in figure 2. The change isn’t significant
and so cannot make a reliable conclusion that this species has decrease in population.
There are many species that were present in 1992 that are no longer present in the survey
done in 2013, such as Asterina phylactica this species may be a classic victim of the current
issues that may not have adapted to the changes and was not able to cope under the
conditions and so may have migrated to a different area.
Although the results from the statistical analysis of abundance between the two surveys
concluded in insufficient data to reject the null hypothesis, the abundance seen in figures 4
and 5 show that abundance has increased at Greatwood Boathouse, although a reference site
was used for this site as access was not available. The abundance has still increased in this
area maybe due to better water quality and better living conditions not affected by the many
activities occurring in the Fal Estuary.
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CONCLUSION
There is insufficient evidence to reject the null hypothesis that there is a significant difference
between the abundance of species in the 1992 survey and the abundance of species in the
2013 survey. Therefore a reliable conclusion as to whether there was change over the last 20
years is not possible.
The statistical test for the biodiversity change proved to be significantly different and so the
null hypothesis was rejected. The biodiversity over the last 20 years has decrease
significantly due to the issues stated in the introduction as a victim of climate change and
increased usage of the Fal Estuary. These results can then be used to help conserve the Fal
Estuaries biodiversity.
ACKNOWLEGEMENTS
Thank you to Falmouth Marine School for supplying equipment and support with this survey
and to William Peter West for supplying information from his survey completed in 2011.
Thank you to Pamella Tompsett for the use of her data in which to compare this survey.
APPENDICES
Statistical analysis:
Paired T for biodiversity:
C1= 2013
C2= 1992
N Mean StDev SE Mean
C1
10 25.30 4.99 1.58
C2
10 26.30 11.50 3.64
Difference 10 -1.00 10.00 3.16
95% CI for mean difference: (-8.15, 6.15)
T-Test of mean difference = 0 (vs not = 0):
T-Value = -0.32 P-Value = 0.759
d.f= 9
Critical value = 2.262
T-Value = -0.32
If t value > thank critical value
Reject the null hypothesis.
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Paired T for ACFOR score of abundance:
C1= 1992
C2= 2013
N Mean StDev SE Mean
C1
63 17.19 29.10 3.67
C2
63 23.71 40.78 5.14
Difference 63 -6.52 44.85 5.65
95% CI for mean difference: (-17.82, 4.77)
T-Test of mean difference = 0 (vs not = 0): T-Value = -1.15 P-Value = 0.253
T-Value = -1.15
Critical value= 1.6698
Test value is smaller than the critical value and therefore there is insufficient data to reject the null hypothesis.
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Table 4: ACFOR Score for all species observed
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Table 5: Biodiversity of all locations' quadrats 2013.
QUADRAT
Pendennis
point
trefusis
point
0m
5m
2
10m
1
15m
2
20m
7
25m
9
30m
8
35m
11
40m
11
45m
8
50m
12
10
55m
60m
65m
17
13
8
11
8
10
0
4
7
8
10
0
7
9
12
8
8
5
2
1
0
0
5
5
9
9
8
6
3
9
8
12
10
mylor
churchtown
greatwood
boathouse
reference
point
6
restronguet
point
5
5
5
12
10
8
5
1
2
5
6
6
10
10
9
8
6
1
5
4
8
7
8
6
6
6
6
4
3
10
4
9
8
5
7
5
8
10
10
6
6
1
5
6
4
loe beach
king harry
ferry west
1
turnaware
point
8
st. just-inroseland
2
5
2
8
6
st. anthony,
amsterdam
point
6
1
6
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