VULNERABILITY OF MODIOLUS MODIOLUS BIOGENIC REEFS TO CLIMATE CHANGE:
A POPULATION-BASED APPROACH FOR EFFECTIVE MARINE MANAGEMENT
Mackenzie, C.L.1, Gormley, K.S.G. 1, Hartl, M.G.J.1, Sanderson, W.G.1 and Porter, J.S.1
1School of Life Sciences, Heriot-Watt University, Edinburgh, EH52 6BN, clm32@hw.ac.uk
BACKGROUND
The marine bivalve, Modiolus modiolus (horse mussel) is an Arctic-Boreal species with a distribution range that extends from the seas around Scandinavia and Iceland southward to the Bay of Biscay. Horse mussel reefs are more limited in their
distribution as compared to the species as a whole with current estimates placing the southern limit of such habitats in the southern Irish Sea. Decline in the extent of M. modiolus reefs has been noted across the species’ European distribution
(Figure 1). Historical fishing activity (scallop trawling and dredging) has caused widespread damage to these areas. M. modiolus reefs are listed as a threatened and/or endangered species and habitat in all OSPAR regions (OSPAR, 2008). Additionally,
key structural or functional species such as M. modiolus may be affected by physical changes in marine environments arising from increases in global CO2 concentrations. Such impacts may result in a decline in the extent and distribution of this
habitat of high conservation importance.
CONSERVATION IMPORTANCE
• M. modiolus reefs are typically characterized by high species diversity;
• Habitat modification by M. modiolus can have substantial effects on the composition and
abundance of mega-faunal benthic organisms in coastal waters;
SOUTHERN LIMIT
• M. modiolus reefs contribute a number of ecosystem services including water quality
improvements, benthic-pelagic coupling, and seabed stabilisation;
• M. modiolus reefs provide important spawning and nursery grounds for fish species;
Figure 1. Modiolus modiolus reefs are listed as
threatened or endangered in all OSPAR areas (shown)
with the southern limit of distribution estimated to be
in the southern Irish Sea.
• M. modiolus reefs are a conservation priority under the EU Marine Strategy Framework Directive
and are a UK Biodiversity Action Plan priority habitat.
RESEARCH QUESTIONS
How does vulnerability to climate change vary between populations of the same species?
What roles do environment and genetics play in shaping the vulnerability of a given population to any particular
stressor?
How can a population-based approach be applied for effective marine management?
Video example (CLICK TO PLAY) of a Modiolus modiolus reef in
Orkney, Scotland (Source: Flora Kent, Heriot-Watt Scientific Dive
Team)
PRELIMINARY RESEARCH OBJECTIVES
1. Determine stress response of M. modiolus populations under climate change conditions relevant to
those conditions experienced by each population (SLIDE 2);
2. Determine genetic connectivity and diversity of M. modiolus populations via microsatellite
screening (SLIDE 3).
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VULNERABILITY OF MODIOLUS MODIOLUS BIOGENIC REEFS TO CLIMATE CHANGE:
A POPULATION-BASED APPROACH FOR EFFECTIVE MARINE MANAGEMENT
Mackenzie, C.L.1, Gormley, K.S.G. 1, Hartl, M.G.J.1, Sanderson, W.G.1 and Porter, J.S.1
1School of Life Sciences, Heriot-Watt University, Edinburgh, EH52 6BN, clm32@hw.ac.uk
RESULTS
CLIMATE CHANGE IMPACTS:
HOW DO STRESS RESPONSES VARY BETWEEN SITES?
(I) DNA STRAND BREAKS
(II) LIPID PEROXIDATION
25
20
% Tail DNA
METHODOLOGY
nmol TBARS mg protein-1
a..
6.0
• M. modiolus were collected during May-June 2014 from three populations situated across the UK range of the
species and representing varying latitudinal positions (Figure 2);
15
10
5
• Thermal acclimation experiments were carried out for each population at ambient (i.e. collection temperature) and
ambient +5°C temperatures for a 7-day period;
Baseline
nmol TBARS mg protein-1
15
10
5
Baseline
c..
Lleyn Peninsula, Wales
20
15
10
5
Warming (15°C)
Baseline
Control (11°C)
Warming (16°C)
Baseline
Control (14°C)
Warming (19°C)
4.0
3.0
2.0
1.0
5.0
4.0
3.0
2.0
1.0
0.0
Baseline
Figure 2. Sampling locations (M. modiolus
population sites).
Control (10°C)
6.0
0
Figure 3. Overview of the Comet Assay.
(CLICK TO PLAY)
Baseline
5.0
Warming (16°C)
nmol TBARS mg protein-1
END
Control (11°C)
25
% Tail DNA
Port Appin, Scotland
1.0
0.0
0
Orkney, Scotland
2.0
6.0
20
• Cellular energetics and gene expression samples were also collected at each sampling point for future analyses.
3.0
Control (10°C) Warming (15°C)
25
b..
4.0
0.0
0
% Tail DNA
• Oxidative stress biomarkers of lipid peroxidation (TBARS assay) and DNA damage (Comet assay) in gill tissue were
measured after one week of exposure to warming conditions (Figures 3 and 4);
5.0
Control (14°C)
Baseline (19°C)
Figure 4. (i) DNA strand break (expressed as % tail DNA) and (ii) lipid peroxidation (expressed as concentration of
TBARS per mg protein) in M. modiolus populations (a. Orkney, b. Port Appin, c. Lleyn Peninsula) following exposure
to ambient (collection temperature) and warming (ambient + 5°C) conditions. Means ± SE shown for n=4-5.
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VULNERABILITY OF MODIOLUS MODIOLUS BIOGENIC REEFS TO CLIMATE CHANGE:
A POPULATION-BASED APPROACH FOR EFFECTIVE MARINE MANAGEMENT
Mackenzie, C.L.1, Gormley, K.S.G. 1, Hartl, M.G.J.1, Sanderson, W.G.1 and Porter, J.S.1
1School of Life Sciences, Heriot-Watt University, Edinburgh, EH52 6BN, clm32@hw.ac.uk
GENETIC CONNECTIVITY AND DIVERSITY:
RESULTS
Table 1. Genetic diversity parameters
WHAT IS THE GENETIC BASIS FOR RESILIENCE?
METHODOLOGY
•
•
•
•
•
Genetic samples (n=50) were collected from M.
modiolus populations across the species’ UK
distribution (Figure 5);
Orkney, Scotland
Genetic screening of each population was carried out
using microsatellite markers;
PCR product amplification confirmed by gel
electrophoresis and genotyping of all markers for all
populations completed by University of Dundee;
Port Appin, Scotland
Point of Ayre, Isle of Man
Strangford Lough,
Northern Ireland
N
He
Ho
NA
48
0.7171
0.4322
13.0
Point of Ayre 31
0.6241
0.5819
9.4
8.84±5.88
0.069
0.0511
Lleyn
Peninsula
10.14± 6.96 0.400
0.0257
0.0659
0.0270
0.0188
0.1079
0.0141
0.0381
0.0893
0.0247
51
0.8450
0.5958
20.8
14.65±8.43
0.297
0.0645
0.1191
Port Appin
41
0.6674
0.6361
14.2
10.85±9.58
0.047
0.0471
0.0108
0.0986
Karlsruhe
54
0.7795
0.5769
15.8
11.75±5.90
0.262
0.0225
0.0481
0.0240
0.0345
0.0432
N = number of samples; He = Expected Heterozygosity; Ho = Observed Heterozygosity; NA = number of alleles; AR = Allelic Richness; Fis = inbreeding
coefficient; Fst = differentiation coefficient, (before (upper diagonal) and after (lower diagonal) ENA correction)).
Table 2. Population differentiation (Fst values)
Lleyn Peninsula, Wales
Lleyn Peninsula
Point of Ayre
Strangford Lough
Figure 5. M. modiolus reef sites for
microsatellite screening.
Fis
Strangford
Lough
Allele peaks scored and analyses of genetic diversity
and connectivity carried out in FreeNA, FSTAT and
Genepop software packages;
Future particle tracking modelling to be carried out to
examine alignment of genetic connectivity data and
potential larval dispersal (Figure 6).
AR
Fst (before and after ENA correction)
Lleyn
Strangford
Point of Ayre
Port Appin Karlsruhe
Peninsula
Lough
Port Appin
Karlsruhe
Lleyn
Peninsula
Point of Ayre
Strangford
Lough
0.0000
0.0239
0.0670*
0.0272*
0.0195*
0.0000
0.1031*
0.0098*
0.0367*
0.0000
0.0893*
0.0245*
0.0000
0.0339
0.0000
Figure 6. Larval dispersal (particle tracking
model) for Wales M. modiolus population
following 10, 20, 30 days (Source: Peter
Robins, Bangor University). (CLICK TO PLAY)
KEY FINDINGS
Port Appin Karlsruhe
1. The Lleyn Peninsula population has the highest inbreeding
coefficient and lowest observed heterozygosity (Table 1).
2. There is significant but generally low genetic differentiation
between most populations (Table 2).
*= significant value (p<0.05)
FUTURE RESEARCH QUESTIONS
CONCLUSIONS
• Do M. modiolus populations vary in their abilities (i.e. phenotypic plasticity) to respond to climate change conditions (under
similar stress levels) ?
Preliminary examination of stress response in M. modiolus populations shows that oxidative stress biomarkers
have potential use as indicators of climate change induced stress response;
• Do M. modiolus populations with increased inbreeding and/or decreased genetic variability exhibit decreased resilience
and/or physiological plasticity to climate change stressors?
Temperatures at the southern limit (Wales) may cause increased levels of oxidative stress in M. modiolus with
regards DNA damage;
• Do M. modiolus have the ability to adapt to extended exposure to single/multiple climate change stressors?
Given its higher degree of inbreeding and lower observed heterozygosity (potentially indicating a reduced ability
for adaptation to changing conditions), the southern limit population (Lleyn Peninsula) may be increasingly
vulnerable to climate change as compared to other populations.
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