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DOES ENVIRONMENTAL CONTEXT INFLUENCE MACROALGAL COMMUNITY COMPOSITION ON
ARTIFICIAL STRUCTURES ?
Veronica Farrugia Drakard
*, Paul Brooks
, Ally Evans
, Tasman Crowe
and
Ecostructure WP2 Partners
University College Dublin
-
veronica.farrugiadrakard@ucdconnect.ie
IBERS, Aberystwyth University, UK
http://www.ecostructureproject.eu/
Abstract
Artificial structures tend to support less diverse assemblages than natural hard substrata, but it is as yet unclear how this effect
varies with environmental context. Here macroalgal assemblages were compared between artificial and natural substrata in
different environmental contexts within the Irish Sea. We find no differences in macroalgal community structure between natural
and artificial structures in any given environmental context. In contrast, we found coralline species to be significantly more
abundant on natural substrata. Community composition differed in two contexts, between estuarine and marine sites, and between
sites with different degrees of urban influence. We propose that these differences may be due to the presence and abundances of
‘
thick leathery
’ species.
Keywords: North Atlantic, Algae, Biodiversity, Coastal systems, Rocky shores
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Artificial infrastructure has become a significant component of coastal and
marine systems, primarily due to accelerated urbanisation [1]. This increase
has major implications for coastal biodiversity, as biotic community
composition differs between artificial and natural substrata [2]. The eco-
engineering approach, which applies ecological principles to the design of
artificial infrastructure, is likely to play a significant role in future strategies to
incorporate ecologically
-sensitive design into marine developments. As
primary producers and habitat providers, seaweeds are integral to both the
physical and trophic structure of many shallow-water marine systems.
Variation in environmental conditions can alter both the species present and
their responses to microhabitats [3]. The aim of this study was therefore to
investigate how environmental context influences macroalgal community
composition on artificial and natural substrata along Irish and Welsh coasts.
We selected 54 sites around the Irish Sea for sampling, 30 along the Irish coast
and 24 along the Welsh coast. These consisted of both natural and artificial
substrata, and were characterised in terms of their environmental (‘
marine
’ vs.
‘estuarine’) and anthropogenic contexts (‘urban’ vs. ‘low urban’ vs. ‘
rural
’).
Ten 25 cm x 25 cm quadrats were deployed at all sites and the abundances of
all macroalgal species present were recorded as percentage cover. Three-way
PERMANOVA and SIMPER procedures were used to characterise patterns in
macroalgal communities between sites.
Contrary to expectation, macroalgal abundances on artificial and natural
substrata did not differ (p = 0.15). There was no evidence of any effect of
environmental or anthropogenic context. There was a significant difference in
macroalgal abundances between
‘
marine
’ and ‘estuarine’ sites (F = 9.55, p <
0.05, df = 1), which was due to Ascophyllum nodosum predominating at
estuarine sites and Fucus vesiculosus predominating at marine sites (Table 1).
There were also significant differences between sites with different degrees of
urban influence (F = 3.04, p < 0.05, df = 2), once again due to A. nodosum and
F. vesiculosus, both of which were present at significantly higher abundances
in
‘
rural
’ locations compared to more urban areas (Table 1).
Coralline species were consistently more abundant on natural rather than
artificial substrata (F = 10.81, p < 0.05, df = 1). These tend to display low
rates of growth and may be unable to establish stable populations under
conditions of frequent disturbance. This has implications for succession on
artificial structures, as coralline species have been shown to influence
recruitment [4] and may provide a more suitable substrate for settlement of
later macroalgal colonists [5].
There was considerable variation among sites in all analyses and we will
undertake statisticial modelling to investigate associated environmental factors.
Although percentage cover is a robust measure widely utilised in this field, it
tells us little about the health and persistence of seaweed populations;
therefore, we are also undertaking a more detailed investigation focused on the
biological function of key habitat providers. The ultimate aim of the work is to
inform effective design of eco
-engineering solutions to enhance biodiversity on
coastal infrastructure.
Tab. 1. SIMPER results showing taxa cumulatively contributing up to 50% to
the dissimilarity between groups tested. Abundances are square root
transformed.
Acknowledgements This research has been funded in part by the Irish
Research Council under the Government of Ireland Postgraduate Programme,
co
-funded by the Environmental Protection Agency. This work was
undertaken as part of the Ecostructure project, which was part-funded by the
European Regional Development Fund (ERDF) Ireland Wales Cooperation
Programme 2014
– 2020.
References
1 - Brook T.W., Gilby B.L., Olds A.D., Connolly R.M., Henderson C.J. and
Schlacher T.A. (2018). The effects of shoreline armouring on estuarine fish are
contingent upon the broader urbanisation context. Marine Ecology Progress
Series, 605, 195 – 206.
2 - Mineur F., Cook E.J., Minchin D., Bohn K., MacLeod A. and Maggs C.A.
(2012). Changing coasts: marine aliens and artificial structures. Oceanography
and Marine Biology: An Annual Review, 50, 189 – 234.
3 - Strain E.M.A., Olabarria C., Mayer-Pinto M., Cumbo V., Morris R.L.,
Bugnot A.B., ... and Bishop M.J. (2017). Eco-
engineering urban infrastructure
for marine and coastal biodiversity: which interventions have the greatest
ecological benefit?
Journal of Applied Ecology
. DOI: 10.1111/1365-
2664.12961.
4 - McCoy S.J. and Kamenos N.A. (2015). Coralline algae (Rhodophyta) in a
changing world: integrating ecological, physiological, and geochemical
responses to global change.
Journal of Phycology
, 51, 6 – 24.
5 - Asnaghi V., Thrush S.F., Hewitt J.E., Mangialajo L., Cattaneo-Vietti R. and
Chiantore M. (2015). Colonisation processes and the role of coralline algae in
rocky shore community dynamics. Journal of Sea Research, 95, 132 – 138.
219 Rapp. Comm. int. Mer Médit., 42, 2019
