1. General observations:

Generally speaking, whether in the lagoon or on the outer slopes, the reefs are in fairly good condition in the 0-15m zone (Fig. 9), with a good level of live coral cover and large branching colonies in the lagoon, although there have been a few isolated cases of bleaching (Fig. 11).

Figure 9 : Coral colonies in the 0-15m zone

The situation is quite different on the western outer slope between 20 and 50 m depth, where we discovered landscapes of coral debris and upturned coral (Fig. 10) at most sites (Fig. 8: stations WLF10, 12, 18, 21, 22, 24), certainly due to the passage of cyclone Evans in December 2012, which hit Wallis from the west. Dead colonies (in the lagoon or outside) are then quite often colonised by cyanobacteria.

Figure 10: Western external slopes at ~40m depth

We only encountered a few specimens of Acanthaster planci here and there during our dives (Fig. 11), a far cry from the massive invasions we witnessed in French Polynesia or more recently in New Caledonia, where there were dozens of them at impacted sites.

Figure 11: Acanthaster planci and bleaching of a coral colony

Large fish and sharks in particular were quite rare in general.

2. Concerning sponges :

A total of 338 samples were collected, divided into 82 identified species (with a species name or OTU number), with their distribution around the island.

Figure 12: Some specimens of sponges

Of the 87 species collected, 41 were in sufficient quantity to produce an extract and screen for biological activity. 29 of these were abundant enough for more in-depth chemical studies. The remaining 46 species were found in single specimens only. For this phylum, in terms of the number of species inventoried, the results are very positive compared with our previous inventories in the Pacific (Tab. 1).

Tableau 1 : Inventories of sponges in the Pacific

Genetic analyses (rDNA of the C 28S region and CO1 mtDNA) carried out by Dirk Erpenbeck's team have enabled the sponge fauna of Wallis & Futuna to be compared and repositioned in relation to the other archipelagos of the South Pacific. They highlight a low number of shared MOTUs, indicating a faunal differentiation between the islands and other regions of the Indo-Pacific. Furthermore, between the islands of Wallis and Futuna, which are 230 km apart, only 8% of the species were found to be common. Finally, of the 82 taxa recorded, 25 have been identified to species level and 9 calcareous sponges are thought to be new (subject to further verification) [1].

Figure 13: Relative taxonomic distribution (approximated) of combined 28S and CO1 MOTUs per Demospongiae order or other sponge class (*) [1]

Following biological activity screening of the 41 most abundant species, several have proved particularly interesting for: the development of new antibacterial strategies, due to their antibiofilm activity [2] (Fig.14); their osteogenic properties [3]; their anti-prion or protein kinase inhibiting capacities.

Figure 14: Antibiofilm activities on Vibrio harveyi [2]

3. Concerning gorgonians:

Merrick Ekins, who worked on these organisms, was able to collect 65 samples, for a total of 35 species. Compared with previous samplings in other Pacific archipelagos, this is half the number of species and half the number of samples.

Figure 15: Some specimens of gorgonians

4. Concerning molluscs:

For Marco Oliverio, who carried out the sampling and initial identifications, the results are rather mixed. 260 samples of macro-molluscs divided into 120 taxa were collected.

Figure 16: Some species of macro-molluscs

By way of comparison, during a previous 15-day campaign carried out in the Marquesas Islands (French Polynesia) in 2011 [4], 600 samples were collected, for a total of 250 taxa. If we refer to the inventory of molluscs published in 1983 [5], 310 species were recorded in Wallis, Futuna and Alofi. The difference between these 2 inventories can be explained in part by the fact that collection was carried out over a much longer period and 3 islands were surveyed. However, there is reason to fear a certain erosion of this biodiversity in the space of 35 years. The samples collected will be identified and placed in a collection at the MNHN in Paris.

^{[1] Galitz A., Ekins M., Reddy M.M., Folcher E., Dumas M., Butscher J., Thomas O.P., Voigt O., Wörheide G., Petek S. and Erpenbeck D. Molecular genetic biodiversity assessment of the Wallis Island sponge fauna in the Tropical Pacific. Journal of the Marine Biological Association of the United Kingdom, 2024, 104, e56. [2] Caudal F., Rodrigues S., Dufour A., Artigaud S., Le Blay G., Petek S., Bazire A. Extracts from Wallis Sponges Inhibit Vibrio harveyi Biofilm Formation. Microorganisms, 2023, 11 (7), 1762. [3] Jourdain de Muizon C., Moriou C., Petek S., Ekins M., Rousseau M., Al Mourabit A. Isolation, Synthesis and Absolute Configuration of the Pericharaxins A and B, Epimeric Hydroxy-Polyene Glycerol Ethers from the Calcarean Sponge Pericharax heteroraphis. Marine Drugs, 2022, 20, 635. [4] Payri C. et al. Pakaihi i te Moana (Leg 2), N/O Braveheart (2011). [5] Richard G. Wallis et Futuna: Ses iles, ses lagons, ses coquillages. (1983) Xenophora, 18, 9-20}