Spongiaria, from the Latin ‘spoggia’, meaning sponge, are metazoan animals belonging to the branch of the Porifera [9]. The oldest fossils date from 630 million years ago [10]. They inhale and exhale through pores connected to a chamber containing choanocytes, cells provided with flagella bringing nutrients. Spongiae have a very simple organization: it has an outer layer, the ectoderm, and an inner layer, the endoderm. They are diploblastic organisms. They have no tissue or differentiated organs and are therefore the most primitive metazoans. Choanocytes also ensure the digestion of nutrients and the entry of water through pores into an organism without circulation [9]. On the other hand, some sponges, carnivorous sponges in higher bathymetries, are not filtering organisms; they capture their prey using hook on their surface [10].

The morphology of Porifera is very variable within a group or even a species. For this reason, it cannot be used as a reference to their classification. Based on their skeleton [10].

Thus, four classes of Spongiaries are distinguished: Demonspongiae, from the Greek “demos” people and “spoggia” sponge; Hexactinellida, siliceous, calcarea, limestone and homoscleromorpha [11]. There are 8730 species, including 680 genera in the four classes mentioned. The most important class is the Demosponges, which accounts for 83% of all species recorded [12].

Martinique is an island with an area of 1100 km² which is bordered by the Caribbean Sea on the West side and by the Atlantic Ocean on the East side. Its shorelines include different types of habitat, namely coral reefs (fringing and barrier reefs), mangroves, seagrasses and sandy bottoms with variable granulometry and mineralization [13]. These habitats collect different benthic communities including coral communities biobuilt and on rock blocks. They also house the herbage of Thalassiumtestudium (turtle grass), Syringodiumfiliforme (mantis grass). These herbivores may be single species or mixed. There are also algal communities, spongians and gorgonians, soft-bottom communities with enfauna on mobile sediments [13].

The substrate is the abiotic factor for attachment and development of spongiform larvae. Therefore, it is important to identify the type of substrate in characterizing different environments and marine sponge species that grow there [14]. We find:

-Reefs, rocky platforms sometimes composed of blocks or coral structures made up of living or dead colonies [13].

-Sandy bottoms with grain sizes ranging from fine sand to coarse sand [13].

-Consolidated or disassembled rock blocks composed of coral fragments, shells, blocks or calcareous algae [13].

-Muddy seabed at the estuary level [13].

-Sand and rock reefs composed of boulders and interspersed with sandy spaces [13].

The sites chosen for the whole island of Martinique are the Anses d’Arlet (Cap Salomon, la Lézarde, Crique Abricot, la Pouponnière, la Petite Sirène, L’Arbre Mort), le Diamant (la Cerise), le Robert (îlets à l’Eau et Boisseau), Sainte-Anne (la Pointe Marin). Abiotic parameters such as temperature, salinity, pH, particle number and saturation percentage were taken 3 times per site and averaged and tabulated (Table 1 and Figure 1).

Table 1. Abiotic factors of studied sites.

Figure 1. Map of study sites throughout Martinique and GPS coordinates.

The density of each species is calculated by quadrat of 4 m² with a number of 8 per station, giving a total of 176 quadrats. The density of sponges was calculated from the following formula:

We are going to recall that in our experiment a quadrat measures 4 m² (Figure 2).

The factorial analysis of the correspondences (FAC) and the hierarchical ascending classification (HAC) from the XLSTAT software made it possible to compare the stations with respect to the population structures of the different spongiform species. The AFC and the CAH are based on a contingency table composed of 34 lines (species) and 22 columns (inventoried stations) shows that there is a link between the rows and columns from a calculated p-value (0.0001) is below the significant level (0.05). The FAC axes F1 and F2 (inertia: 38.21%) in Figure 1 distinguish stations according to taxonomic criteria.

The correlation factor (FAC) analysis and from the XLSTAT software made it possible to compare the quadrats with respect to densities of different species of sponges. The AFC, applied to the contingency table (34 species × 155 squares), reveals a statistically significant association between the rows and columns. This conclusion is drawn from a p-value of 0.0001, which falls below the standard significance threshold of 0.05. The FAC axes F1 and F2 (inertia: 17.99%) in Figure 5 distinguish stations according to taxonomic criteria.

Figure 2 is a graph of the evolution of the specific density for 34 species for 155 squares of 4 m² with values ranging from 0.25 to 5 individuals/m².

Based on the resulting graph (Figure 2), 6 species of spongiae are found in all types of media, namely Xestospongiamuta, Aplysinafistularis, Iotrochotabirotulata, Amphimedoncompressa, Niphatesdigitalis and Verongulasp.

Figure 2. Graph of specific densities per quadrat of the 22 stations studied.

Figure 3 shows the evolution of the number of sponges species per station for the 22 stations surveyed. Stations with minimum values are CHERRY1, CHERRY 2 and CHERRY 3 with a single listed species. The stations with maximum values are LEZARDE 1 which has 19 species and CAP SALOMON 1, CRIQUE ABRICOT 1 with 18 species. Three other stations PETITE SIRENE 2, CAP SALOMON 2, and ARBRE MORT 1 include 14 species of marine sponges, a significant number of species. ILET A L’EAU 1 station records a small number of species with a total of 4 species, as well as the stations POINTE MARIN 1 and POUPONNIERE 1 which have a total of 5 species.

Figure 3. Graph of number of sponges species per station.

Group1

The stations POUPONNIERE 3, POUPONNIERE 2, LEZARDE 2, PRECHEUR 1 are colonized Neofibularianolitangere, Aplysinafistularis, Amphimedoncompressa, Verongulasp, AmphimedonviridisandIotrochotabirotulata. In the stations ILET BOISSEAU 1 and POINTE MARIN 2 there is only Aplysinafulva (Figure 4).

Group2

The SALOMON 2 station is characterized by Erylus formosus. The SALOMON 1 station is characterized by Plakortis halichondrioides and Niphates erecta. The SIRENE 1 station is characterized by Pseudosuberitesmollis. The stations DEAD TREE 1, LEZARDE 1, DEAD TREE 2, CHERRY 1 and CHERRY 2 are characterized by Agelasclathrodes, Agelasconifera, Clionadelitrix, Ectyoplasiaferox, Topsentiaophiradites and Xestospongiamuta. The stations LEZARDE 3, SIRENE 2 and ARBRE MORT 3 are characterized by Xestospongiamuta, Irciniacampana, Niphatesdigitalis, Agelasdispar, Irciniasp, Cinachyrellakuekenthali, Depsammaanchorata, Spirastrellacoccina, Callyspongiaplicifera and Mycalelaevis (Figure 4).

Group3

The EAU 1 station is characterized by Aplysinacauliformis (Figure 4).

Figure 4. Factor Analysis of Correspondence of the 22 stations studied.

Stations are selected by the HAC through a dendrogram based on their percentage of similarity in sponges population (Figure 5).

Figure 5. Hierarchical Ascending Classification of the 22 stations studied.

Stationsofthesamesitewithhighsimilarityrate

CHERRY 1 and CHERRY 2 stations have 95% similarity. POUPONNIERE 2 and 3 stations have 95% similarity. POINTE MARIN 1 and POINTE MARIN 2 have 90% similarity. ARBRE MORT 1 and ARBRE MORT 3 have 84% similarity (Figure 5).

Stationsfromdifferentsiteswithhighsimilarityrates

The CHERRY 3 and POUPONNIERE 1 stations have 94% similarity. The ILET BOISSEAU 1 and POUPONNIERE 2 stations have 94% similarity. DEAD TREE 2 and LEZARDE 1 have 74% similarity. PRECHEUR 1 and LEZARDE 3 have 64% similarity (Figure 5).

TheIletàl’Eau,particularity

Ilet à l’Eau is a unique station because it has a very small percentage of similarity with the other 21 stations. The most important similarity rate does not exceed 14% (Figure 5).

The CFA differentiated 5 groups according to the density of sponges per quadrats (Figure 6).

Group1

Group 1 is composed of: quadrats 1, 2, 3, 5, 7 of station POUPONNIERE 3; quadrats 2, 4, 6 of station ARBRE MORT 3; quadrats 3, 5,6, 7, 8 of station ARBRE MORT 1; quadrats 3, 7, 8 of station LEZARDE 3; quadrats 2, 3, 4, 5, 5, 6, 7, 8 of the station DEAD TREE 2; of the squares 1, 3, 4, 5, 6, 7, 8 of the station LEZARDE 1; of the quadrat 6 of the station PRECHEUR 1; of the quadrat 1 of the station CHERRY 1; of the quadrat 1 of the CHERRY 2 station; of the quadrats 1, 2, 4, 5, 6, 7, 8 of the PETITE SIRENE 1 station; of the quadrats 1, 8 of the POUPONNIERE 2 station; of the eight quadrats of the stations PETITE SIRENE 2, CAP SALOMON 2, CRIQUE ABRICOT 1.

Figure 6. Factor Analysis of Correspondence of the quadrat of the 22 stations studied.

The characteristic species of this group are: Halisarcacaerulea, Erylusformosus, Niphateserecta, Callyspongiaacuelata, Irciniafelix, Diplastrellasp, Haliclonacarerulea, Clionadelitrix, Pseudomoritesmollis, Agelasconifera, Ectyoplasiaferox, Spirastrellacoccina, Mycalelaevis, Ploakortishalichondroides, Amphimedonviridis, Agelasdispar, Niphateserecta, Cinachyrellakuekenthali, Callyspongiaplicifera, Agelascitrina, Topsentiaophiraphidites, Irciniasp, Agelasclathrodes, Niphatesdigitalis.

Group2

Group 2 is composed of: the quadrats 4, 6, 8 of station POUPONNIERE 3; the quadrats 1, 3, 5, 7, 8 of station ARBRE MORT 3; the quadrats 1, 2, 4 of station ARBRE MORT 1; the quadrats 1, 2, 4, 5, 6 of station LEZARDE 3; the quadrat 1 of station ARBRE MORT 2; of the quadrat 2 of station LEZARDE 1; of the quadrat 3 of station PETITE SIRENE 1; of the quadrats 1, 5, 6 of station PETITE SIRENE 2; of the quadrats 2, 3, 4, 5, 6, 7 of station POUPONNIERE 2; of the quadrat 1 of station CHERRY 3; of the eight quadrats of stations ILET BOISSEAU 1, LEZARDE 2, POUPONNIERE 1 and POINTE MARIN 1.

The characteristic species of this group are: Iotrochotabirotulata, Aplysinafistularis, Amphimedoncompressa, Irciniastrobolina, Irciniacampana et Neofibularianolitangere.

Group3

This group is composed of the quadrats 5 and 8 of EAU 1.

The characteristic species is Aplysinafulva.

Group4

Group 4 is composed of the quadrats 4 and 8 of POINTE MARIN 2 and the quadrat 3 of ILET A L’EAU 1.

The characteristic species is Aplysinacauliformis.

Group5

Group 5 only includes the square 8 of ILET À L’EAU 1.

The species characteristic of this group is Aplysinacauliformis.

In general, there is heterogeneity in the distribution of species according to environmental factors across all quadrants (Figure 6).

In Group 1, 7 stations have a sand-rock substrate namely POINTE MARIN 1, POINTE MARINE 2, ILET BOISSEAU 1, POUPONNIERE 1, POUPONNIERE 2, POUPONNIÈRE 3, CHERRY 3 and 2 stations have a bedrock of PRECHEUR 1 and LEZARDE 2. The 2 rock stations are inclined horizontally (Table 2).

LEZARDE 1, LEZARDE 3, CAP SALOMON 1, CAP SALOMON 2, ARBRE MORT 1, ARBRE MORT 3, CRIQUE ABRICOT 1, PETITE SIRENE 1, PETITE SIRENE 2, and CHERRY 1, CHERRY 2, and ARBRE MORT 2 are the only stations in Group 2 that are covered by a bedrock. The 3 stations with sandy-rocky substrate have a horizontal slope while the other 8 stations with rock substrate have a vertical slope (Table 2).

The ILET BOISSEAU 1 station in Group 3 is unique because of its mixed substrate. It is sandy with a sparse presence of small boulders and seagrass (Table 2). The transition between a coral reef zone and a seagrass is characterized by this substrate [13].

The statistical analysis distinguishes three groups.

The first group is mainly composed of stations with a sandy-rocky bottom. While the second group is mainly composed of stations with a bedrock.

However, two Group 1 stations have a bedrock, namely LEZARDE 2 and PRECHEUR 1. Indeed, sandy and rocky substrates have lower specific recruitment compared to the bedrock. However, these stations, even if they have a bedrock, both have abiotic factors that can cause a regression of the specific recruitment, namely their degree of inclination. The LEZARDE 2 station is at a reef level but with a low degree of inclination. The relationship between inclination and specific abundance has been made [6]. A vertical slope allows for greater recruitment and therefore higher specific abundance [6]. PRECHEUR 1 is a bedrock with a vertical slope. However, the hydrodynamics of this station are strong. This is a factor that decreases specific abundance [6][17].

In the second group, characterized by bedrock (reefs and boulders), 3 stations are distinguished, those with a sandy-rocky substrate. These are CHERRY 1, CHERRY 2 and ARBRE MORT 2.

The CHERRY 1 and CHERRY 2 stations are sandy with a small presence of small boulders. It should be noted that these two stations have a similarity rate of about 95% at population level (Figure 5). Indeed, CHERRY1 and CHERRY2 have a low specific abundance and only count Xestospongiamuta as the species listed on the entire inventory (Figure 3). Hence their presence in Group 2 where Xestospongiamuta is a characteristic species. Aside from the low specific abundance of stations 1 and 2 in Cherry, it is important to note that Xestospongiamuta is a species capable of colonizing any type of substrate, which explains its presence in these two sand-bottom stationsrocky as well as rock-bottom [18].

The ARBRE MORT 2 and LEZARDE 1 stations have a population similarity rate of 74% despite differences in abiotic factors (Table 2 and Figure 5). This high percentage of similarity between these two stations could be explained by the fact that the ARBRE MORT 2 station still has a significant presence of rocks allowing an important specific recruitment.

The nature of the substrate is a predominant abiotic factor in the distribution of marine sponges, particularly in their recruitment. The degree of inclination is also a discriminating factor. Indeed, it is noted that for stations with different types of substrate, the degree of inclination of the bottom becomes the factor allowing a high similarity in their population structure.

There is also a small number of species for depths between 2 and 4 m (Table 1). The stations concerned are CHERRY 1, CHERRY 2, CHERRY 3, ILET BOISSEAU 1, ILET A L’EAU 1, POINTE MARIN 1 and POINTE MARIN 2. These stations have a maximum of 8 species compared to 19 for the more diverse station LEZARDE 1 (Figure 3). This is equivalent to seeing an increase in specific diversity with an increase in bathymetry [19]-[22].

Substrate stability can affect specific diversity through its influence on the balance between supply of new spaces by disturbance and the taking over of these surfaces by dominant competitive species [23]-[25]. This balance is a compromise between competitive prowess and the recruitment efficiency of these spaces by species [23]. Our results are aligned with this reflection. The species Neofibularianolitangere (family Desmacellidae), Aplysinafistularis (family Niphatidae), Amphimedoncompressa (family Niphatidae), Verongulasp (family Aplysinidae), Amphimedonviridis (family Niphatidae) et Iotrochotabirotulata (family Iotrochotidae) et Aplysinafulva (family Aplysinidae) characterize the sandy-rocky bottom stations (Figure 4).

The species Erylusformosus (family Geodiidae), Plakortishalichondrioides (family Plakinidae), Niphateserecta (family Niphatidae), Pseudosuberitesmollis (family Suberitidae), Agelasclathrodes (family Agelasidae), Agelasconifera (family Agelasidae), Clionadelitrix (family Clionaidae), Ectyoplasiaferox (family Raspalidae), Topsentiaophiradites (family Halicondriidae), Xestospongiamuta (family Petrosiidae), Irciniacampana (family Irciniidae), Niphatesdigitalis (family Niphatidae), Agelasdispar (family Agelasidae), Irciniasp (family Irciniidae), Cinachyrellakuekenthali (family Tetillidae), Depsammaanchorata (family Desmacididae), Spirastrellacoccina (family Spirastrellidae), Callyspongiaplicifera (family Callyspongiidae) et Mycalelaevis (family Mycalidae) characterize rocky substrates and reefs (Figure 4).

There are 7 sponge species, with 4 families belonging to sandy-rocky bottoms, whereas 20 species, with 15 families belonging to bedrock. This result shows a high specific diversity in the bedrock. Therefore, stations with an unstable substrate (Table 2) show less specific recruitment, while stations with a stable substrate (Table 2) are the site of interspecific competition for the occupation of these spaces. It should also be noted that these spaces are subject to interspecific competition from non-spongy benthic communities such as corals, gorgonians, algae and other colonial invertebrates [13][26]-[29].