• European Marine Science
• 2022-2022close
• BF close

Abstract Indonesia is the largest country made only of islands, with previous census identifying between 13,000 and 25,000 islands. The current official figure puts the number at 17,508 islands. Landsat satellite images were used to provide a documented consistent inventory of the country’s islands. A total of 13,558 islands were mapped considering a minimum size of about 0.001 km2-with 87% and 39% of the islands covering less than 1 and 0.01 km2 respectively. These numbers highlight the dominance of small to very small islands. Beyond providing new accurate spatial statistics, we argued that the island census could be the foundation of a One Map for Small Islands Policy. Indonesia launched its One Map Policy in 2017 to mitigate land use conflicts in the largest of the islands, but small islands have their own development, social and conservation issues, and an extension of the One Map Policy vision to Small Islands is warranted.

International audience; Among the 18 species included in the Ceiba genus in the Malvaceae (Bombacoideae) family, Ceiba pentandra (L.) Gaertn. is not only the tallest and most widespread but also occupies the most prominent place in Neotropical cosmovisions. In this ethnobotanical review, we compare perceptions and uses of Ceiba and related species across Indigenous and Afro-descendant cultures ranging from the Caribbean to the Argentinian Chaco. Ceiba’s widely shared role as axis mundi (particularly in Amazonia), psychopomp, and as a shelter of major forest spirits makes it a perfect example of a Spiritual Keystone Species, a new concept inspired from the concept of Cultural Keystone Species and defined here for the first time.

Ulva is a green macroalgal genus with rich species diversity and worldwide distribution. While current knowledge on Ulva diversity focuses on temperate regions, genetic and morphological data in tropical and subtropical areas are scarce and the species richness is not clearly defined. The genus is known for its bloom-forming ability that can induce green tides leading to severe environmental and economic damage. In the last two decades, several important blooms of Ulva spp. have occurred in New Caledonia, requiring further investigations to identify the species involved. As knowledge of New Caledonian Ulva diversity is limited, an update to the Ulva spp. inventory in the area is essential. Based on Ulva specimens collected throughout New Caledonia (Grande Terre, Isle of Pines and Loyalty Islands), we (1) reassessed species diversity using species delimitation methods, (2) analysed morpho-anatomical characters to identify species and/or enrich their diagnosis, and (3) reconstructed a multilocus phylogeny (ITS, rbcL, tufA) of the genus. We found 21 secondary species hypotheses (SSHs) among our dataset, from which five were successfully assigned to U. lactuca, U. ohnoi, U. tepida, U. meridionalis and U. taeniata. Ten SSHs were defined as new species for which we provided taxonomic description, and six other SSHs were singletons that will need to be data-enriched for better interpretation. Our concatenated multilocus matrix included 61 Ulva species. Of these, 15 species were found in New Caledonia and were moderately to strongly supported. Among the Ulva species found in New Caledonia, seven are known to be bloom-forming which highlights the need for strict regulation and regular monitoring of water quality, particularly in areas exposed to strong nutrient input where these species can form green tides. Highlights Ulva diversity in New Caledonia was reassessed with 15 species highlighted. Ten new species have been discovered in New Caledonia. Indigenous species caused recent green tides in New Caledonia.

French Polynesia atolls are spread on a vast 2300 by 1200 km Central Pacific Ocean area exposed to spatially and temporally dependent wave forcing. They also have a wide range of closed to open morphologies and several have been suitable to develop from black-lipped pearl oysters a substantial pearl farming activity in the past 30 years, representing nowadays the 2nd source of income for French Polynesia. Considering here only the component of lagoon renewal that is driven by waves, we investigate for 74 atolls different lagoon renewal metrics using 20 years of wave model data at 0.05° spatial resolution. Wavelet spectral analyses highlight that atolls, even in close vicinity, can be exposed to different and characteristic periodicities in wave-driven flows and water renewal. These characteristics are discussed in relation to pearl farming atolls, including atolls known to be efficient oyster spat producers, a critical activity for pearl farming sustainability.

For more than a decade, high-throughput sequencing has transformed the study of marine planktonic communities and has highlighted the extent of protist diversity in these ecosystems. Nevertheless, little is known relative to their genomic diversity at the species-scale as well as their major speciation mechanisms. An increasing number of data obtained from global scale sampling campaigns is becoming publicly available, and we postulate that metagenomic data could contribute to deciphering the processes shaping protist genomic differentiation in the marine realm. As a proof of concept, we developed a findable, accessible, interoperable and reusable (FAIR) pipeline and focused on the Mediterranean Sea to study three a priori abundant protist species: Bathycoccus prasinos, Pelagomonas calceolata and Phaeocystis cordata. We compared the genomic differentiation of each species in light of geographic, environmental and oceanographic distances. We highlighted that isolation-byenvironment shapes the genomic differentiation of B. prasinos, whereas P. cordata is impacted by geographic distance (i.e. isolation-by-distance). At present time, the use of metagenomics to accurately estimate the genomic differentiation of protists remains challenging since coverages are lower compared to traditional population surveys. However, our approach sheds light on ecological and evolutionary processes occurring within natural marine populations and paves the way for future protist population metagenomic studies. International audience

The crucial role of crustose coralline algae (CCA) in inducing hard coral larval settlement and ensuring the replenishment of coral reefs is widely accepted, and so are the negative effects of anthropogenic CO 2 emissions on both CCA abundance and coral development. However, diversified and well-developed coral reef communities have been recently discovered in natural conditions where CCA and corals would not be expected to thrive. Back-reef pools, volcanic CO 2 vents, mangrove estuaries, and semi-enclosed lagoons systems can present seawater pH, temperature, and dissolved oxygen values reaching or even exceeding the conditions currently predicted by the Inter Panel on Climate Change (IPCC) for 2100. In the semi-enclosed lagoon of Bouraké (New Caledonia, southwest Pacific Ocean), seawater pH T , dissolved oxygen, and temperatures regularly fluctuate with the tide reaching respectively minimum values of 7.23 pH T units, 2.28 mg O 2 L -1 , and maximum of 33.85°C. This study reports the effect of such extreme environmental conditions on hard coral recruitment and CCA originally settled at a forereef on artificial substrates that were transplanted over two years in two fringing reef and at the Bouraké lagoon. Our data emphasize the negative effects of the extreme conditions in our study sites on the CCA, which decreased in cover by ca. 80% and lost in the competition with turf algae, which, in turn, increased up to 162% at the end of the two years. Conversely, hard coral recruitment remained high at Bouraké throughout the study, three-fold higher than at two sites located outside Bouraké where environmental conditions were typical for coastal fringing reefs. Our findings show that while such extreme, climate change like-conditions have a direct and adverse effect on CCA abundance, and despite a certain persistence, coral larvae settlement was not affected. Based on previous findings from Bouraké, and the present observations, both coral recruits and adults seem to be unaffected despite the extreme environmental conditions. This study supports previous research illustrating how extreme natural and variable environments may reveal unexpected and positive insights on the processes underlying coral acclimatization and adaptation to global change. International audience

To assess the photophysiological capacity of the recently described Ulva batuffolosa to form blooms in coral reefs, we monitored its biomass and photophysiological capacity with pulse amplitude modulated (PAM) fluorometry over a year period on a coastal barrier reef in New Caledonia, along with temperature and light. Effective and maximum quantum efficiencies of the photosystem II measured on this Ulva species indicated that the algae was in a “good health” all over the year with high quantum efficiencies under either light (Fq’/Fm’) or dark incubated conditions and (Fv/Fm). Photo-acclimation and -regulation status used by this Ulva sp. were driven by seasons (i.e., light and temperature) in the lagoon. Although photo-inhibition was an evidence during the warm period, U. batuffolosa was overall well adapted to tolerate the range of irradiance and temperature that characterized the lagoon over the year, which suggests that photosynthesis is not an impediment to green tides by this species.