11 Management of Infralittoral Habitats: Towards a Seascape Scale Approach
175
i.e. essentially the effectiveness of predation and the access to food. The patterns of abundance of juveniles of fishes thus resulting from the structuring of
the infralittoral zone at its different scales (habitat and seascape mosaic) may
for example be illustrated by: (1) at habitat scale, the homogenisation of the
shallow bottoms with heterogeneous granulometry (small rocks, stones, gravel,
sand) off artificial beaches by the artificial addition of fine and homogeneous
granulometry reduces the nursery value of these bottoms for the Diplodus spp.
(Cheminée et al. 2011); (2) habitat scale: the arborescent macrophyte-formed
habitat (such as the forested assemblages of Cystoseira crinita or C. balearica)
shelter 9–12 times more juveniles of Symphodus spp. than the less complex
habitat formed by shrubby Dictyotales-Sphacelariales assemblages (Cheminée
et al. 2013); (3) at the mixed scale of habitat and seascape: the alteration of
a forest of Cystoseira, which is reflected by (a) a decline in the density of
the forest (reduction of complexity) and (b) its fragmentation (increase in heterogeneity) reduces its nursery value for the juveniles of Symphodus ocellatus
(Cheminée 2012), but at the same time this heterogeneity (co-occurrence of the
two different habitats Cystoseira forest and shrubby Dictyotales-Sphacelariales
assemblage) is favourable for the juveniles of Coris julis (‘edge effect’) and
increases for this species the nursery value of these two habitats (Cheminée
2012); (4) at the scale of the seascape mosaic: the co-occurrence of several different nursery habitats (heterogeneity), because of their complementarity will
shelter a greater diversity of species of juveniles than a seascape constituted of
a single habitat. Indeed, there is a spatial partition of the juveniles of different
species (Harmelin-Vivien et al. 1995); (5) at the scale of the seascape mosaic: the homogenisation of the bottoms with meadows of Caulerpa taxifolia
is harmful for juveniles of Coris (Cheminée et al. under review).
Box 2: Historic causes: the case of the major coastal redevelopment
schemes of the nineteenth and twentieth centuries in the bay of Marseille
In the bay of Marseille (i.e. partly within the adjacent maritime area of the
Park), what has been the degree of fish productivity lost through the irremediable destruction of the nurseries situated at the sites of the major coastal
redevelopment schemes of the nineteenth and twentieth centuries? According
to Meinesz et al. (2006), in the urban district of Marseille, prior to the main artificialisation of the coast (i.e. before 1800), the initial coastline was 114 km in
length; 32 km of coastline were artificialised, resulting in a rate of occupation of
the shallow bottoms (0–10 m) of 49 % of their initial surface area (1421 ha). For
example, the horseshoe-shaped artificial beaches constructed at Prado (PradoPlage and Prado Bonneveine, Annexe 1) consist of a homogeneous substrate
of fine gravel, separated by sheer, solid rock seawalls. This redevelopment
was carried out (late 1970s) over shallow bottom areas including nursery areas
175
i.e. essentially the effectiveness of predation and the access to food. The patterns of abundance of juveniles of fishes thus resulting from the structuring of
the infralittoral zone at its different scales (habitat and seascape mosaic) may
for example be illustrated by: (1) at habitat scale, the homogenisation of the
shallow bottoms with heterogeneous granulometry (small rocks, stones, gravel,
sand) off artificial beaches by the artificial addition of fine and homogeneous
granulometry reduces the nursery value of these bottoms for the Diplodus spp.
(Cheminée et al. 2011); (2) habitat scale: the arborescent macrophyte-formed
habitat (such as the forested assemblages of Cystoseira crinita or C. balearica)
shelter 9–12 times more juveniles of Symphodus spp. than the less complex
habitat formed by shrubby Dictyotales-Sphacelariales assemblages (Cheminée
et al. 2013); (3) at the mixed scale of habitat and seascape: the alteration of
a forest of Cystoseira, which is reflected by (a) a decline in the density of
the forest (reduction of complexity) and (b) its fragmentation (increase in heterogeneity) reduces its nursery value for the juveniles of Symphodus ocellatus
(Cheminée 2012), but at the same time this heterogeneity (co-occurrence of the
two different habitats Cystoseira forest and shrubby Dictyotales-Sphacelariales
assemblage) is favourable for the juveniles of Coris julis (‘edge effect’) and
increases for this species the nursery value of these two habitats (Cheminée
2012); (4) at the scale of the seascape mosaic: the co-occurrence of several different nursery habitats (heterogeneity), because of their complementarity will
shelter a greater diversity of species of juveniles than a seascape constituted of
a single habitat. Indeed, there is a spatial partition of the juveniles of different
species (Harmelin-Vivien et al. 1995); (5) at the scale of the seascape mosaic: the homogenisation of the bottoms with meadows of Caulerpa taxifolia
is harmful for juveniles of Coris (Cheminée et al. under review).
Box 2: Historic causes: the case of the major coastal redevelopment
schemes of the nineteenth and twentieth centuries in the bay of Marseille
In the bay of Marseille (i.e. partly within the adjacent maritime area of the
Park), what has been the degree of fish productivity lost through the irremediable destruction of the nurseries situated at the sites of the major coastal
redevelopment schemes of the nineteenth and twentieth centuries? According
to Meinesz et al. (2006), in the urban district of Marseille, prior to the main artificialisation of the coast (i.e. before 1800), the initial coastline was 114 km in
length; 32 km of coastline were artificialised, resulting in a rate of occupation of
the shallow bottoms (0–10 m) of 49 % of their initial surface area (1421 ha). For
example, the horseshoe-shaped artificial beaches constructed at Prado (PradoPlage and Prado Bonneveine, Annexe 1) consist of a homogeneous substrate
of fine gravel, separated by sheer, solid rock seawalls. This redevelopment
was carried out (late 1970s) over shallow bottom areas including nursery areas