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Estuarine, Coastal and Shelf Science 119 (2013) 119e125

Contents lists available at SciVerse ScienceDirect

Estuarine, Coastal and Shelf Science

journal homepage: www.elsevier.com/locate/ecss

Inﬂuence of microhabitat on seedling survival and growth of the
mediterranean seagrass posidonia oceanica (l.) Delile

Adriana Alagna a,b,*, Tomás Vega Fernández b, Antonio Terlizzi a, Fabio Badalamenti b

a DiSTeBA, Department of Biological and Environmental Science and Technologies, Università del Salento, Prov.le Lecce-Monteroni, 73100 Lecce, Italy
b CNR-IAMC, Institute for the Coastal Marine Environment, Via G. da Verrazzano 17, 91014 Castellammare del Golfo (TP), Italy

article info abstract

Article history: Early life history phases are crucial stages limiting species distribution and abundance, thus inﬂuencing
Received 12 February 2012 assemblage composition in marine benthic environments. In seagrass systems the period between seed
Accepted 2 January 2013 germination and establishment is one of the most vulnerable phases for plant development. This study
Available online 18 January 2013 analyzes the inﬂuence of microhabitat structure, in terms of substrate nature and algal canopy, on the
persistence and growth over two years of seedlings of Posidonia oceanica, the dominant Mediterranean
Keywords: seagrass. Long time persistence of seedlings only occurred on microhabitats providing vegetated rocky
settlement substrates, with a maximum value of 81% on rock covered by Cystoseira spp. No seedling was found on
recruitment unvegetated sand and gravel after the ﬁrst year. Seedling growth resulted increased on rock covered by
facilitation Halopteris spp. and Dilophus spp. than on rock covered by Cystoseira spp. Results suggest that high canopy
substrate preference onto a stable substrate enhances seedling persistence, probably because these allow the best anchorage
habitat suitability by roots while hampering water ﬂow. In contrast, turf algal cover promotes better seedling growth,
survival bottleneck possibly through higher light irradiance and nutrient availability. Our ﬁndings support the view that the
understanding of the factors controlling early life processes is a necessary prerequisite for the com-
prehension of seagrass species distribution patterns, colonization and recovery potentials, which, in turn,
can guide sound strategies for seagrass management and restoration.

1. Introduction seedling recruitment events, the contribution of sexual propagules
to the dynamic of seagrass meadows has been considered unim-
The awareness of seagrass importance has grown in the past portant for most large perennial species (Whitﬁeld et al., 2004;
decades at a global scale, together with efforts in protection and Orth et al., 2006a,b) including the Mediterranean seagrass Pos-
restoration initiatives (Duarte, 2002; Kenworthy et al., 2006; Orth idonia oceanica (Gobert et al., 2006). The availability of longer time-
et al., 2006a,b; Duarte et al., 2008). Current trends in seagrass series data about ﬂowering and germination (Balestri and Cinelli,
restoration ecology point to develop methodologies based on un- 2003; Calvo et al., 2006; Diaz-Almela et al., 2006; Balestri and
derstanding of the species natural history and facilitation processes Lardicci, 2008) together with recent ﬁndings about P. oceanica
affecting the early phases of the life cycle, and on a better knowl- meadows genetic variability (Diaz-Almela et al., 2006; Tomasello
edge of factors controlling them (Seddon, 2004; Irving et al., 2010; et al., 2009) conﬁrm that the role played by sexual recruitment
Wear et al., 2010). As colonisation and recovery potentials rely on for this species has been severely underestimated.
dispersed propagules, a deep comprehension of factors controlling
recruitment is an essential prerequisite. In vegetated systems, the recruitment of new individuals is the
outcome of a sequence of processes starting with seed production,
In seagrass systems the role of sexual reproduction in main- dispersion and germination, to seedling settlement and recruit-
taining existing beds and colonizing new areas is scarcely under- ment. Each of these processes has speciﬁc probabilities to occur and
stood (Inglis, 2000; Orth et al., 2000; Kenworthy et al., 2002; can constitute a bottleneck for the plant life-cycle, thus limiting
Whitﬁeld et al., 2004). Owing to the rarity of direct observation of species abundance and distribution and hence inﬂuencing assem-
blage composition (Gomez-Aparicio, 2008). The period between
* Corresponding author. CNR-IAMC, Institute for the Coastal Marine Environ- seed germination and seedling establishment is considered one of
ment, Via G. da Verrazzano 17, 91014 Castellammare del Golfo (TP), Italy. the most vulnerable phase for plant development (Harper,1977) and
evidence collected for seagrasses conﬁrmed the existence of a bot-
E-mail addresses: adriana.alagna@gmail.com, adriana.alagna@libero.it tleneck in seedlings survival within the ﬁrst years of life (Olesen and
(A. Alagna).

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