11 research outputs found
Impact of Super Typhoon ‘Hinnamnor’ on Density of Kelp Forest and Associated Benthic Communities in Jeju Island, Republic of Korea
No full textThis study was carried out to determine the levels of resistance and resilience of kelp forests to large-scale physical disturbances. Our study site, Seongsan, Jeju Island, was impacted by super typhoon ‘Hinnamnor’. Before the typhoon, Seongsan had shown high ecosystem stability. Our results indicated that the ecological stability of a kelp forest facing a severe typhoon is strongly linked to the prevailing environmental conditions. Although typhoon impact resulted in a significant loss of brown macroalgae canopy, Ecklonia cava remained dominant within the kelp forest community. Resistance and resilience levels strongly depended on water temperature and movement and presence of turf-forming algae. Hence, hydrodynamic and biological factors strongly influence the overall stability of a kelp forest. We also report the first occurrences of a scleractinian coral species (i.e., Montipora millepora) at Seongsan, which became visible after canopy loss following the typhoon. Our findings provide valuable ecological information about the benthic community of kelp-dominated ecosystems and are essential to mitigate the impacts of expected climate change-driven rises in seawater temperature and the frequency of super typhoons
Monitoring ecological dynamics on complex hydrothermal structures: A novel photogrammetry approach reveals fine‐scale variability of vent assemblages
No full textWe set out to characterize the fine-scale processes acting on interannual dynamics of deep-sea vent fauna by using a novel approach involving a 5-yr time series of 3D photogrammetry models acquired at the Eiffel Tower sulfide edifice (Lucky Strike vent field, Mid-Atlantic Ridge). Consistently, with the overall stability of the vent edifice, total mussel cover did not undergo drastic changes, suggesting that they have been at a climax stage for at least 25 yr based on previous data. Successional patterns showed consistency over time, illustrating the dynamic equilibrium of the ecological system. In contrast, microbial mats significantly declined, possibly due to magmatic events. The remaining environmental variability consisted of decimeter-scale displacement of vent outflows, resulting from their opening or closure or from the progressive accretion of sulfide material. As a result, vent mussels showed submeter variability in the immediate vicinity of vent exits, possibly by repositioning in response to that fine-scale regime of change. As former studies were not able to quantify processes at submeter scales in complex settings, this pioneering work demonstrates the potential of 3D photogrammetry models for conducting long-term monitoring in the deep sea. We observed that the ability of mussels to displace may enable them to cope with changing local conditions in a stable system. However, the long-term stability of mussel assemblages questions their capacity to withstand large-scale disturbances and may imply a low resilience of these “climax” communities. This suggests that they may be particularly vulnerable to the negative effects of mining activities in hydrothermal ecosystems
Warming could shift the phenological responses of benthic microalgae in temperate intertidal zones
No full textInternational audienc
Exposure to nanoplastics and nanomaterials either single and combined affects the gill-associated microbiome of the Antarctic soft-shelled clam Laternula elliptica
No full textNanoplastics and engineering nanomaterials (ENMs) are contaminants of emerging concern (CECs), increasingly being detected in the marine environment and recognized as a potential threat for marine biota at the global level including in polar areas. Few studies have assessed the impact of these anthropogenic nanoparticles in the microbiome of marine invertebrates, however combined exposure resembling natural scenarios has been overlooked. The present study aimed to evaluate the single and combined effects of polystyrene nanoparticles (PS NP) as proxy for nanoplastics and nanoscale titanium dioxide (nano-TiO2) on the prokaryotic communities associated with the gill tissue of the Antarctic soft-shell clam Laternula elliptica, a keystone species of marine benthos Wild-caught specimens were exposed to two environmentally relevant concentrations of carboxylated PS NP (PS-COOH NP, ∼62 nm size) and nano-TiO2 (Aeroxide P25, ∼25 nm) as 5 and 50 μg/L either single and combined for 96h in a semi-static condition.Our findings show a shift in microbiome composition in gills of soft-shell clams exposed to PS NP and nano-TiO2 either alone and in combination with a decrease in the relative abundance of OTU1 (Spirochaetaceae). In addition, an increase of gammaproteobacterial OTUs affiliated to MBAE14 and Methylophagaceae (involved in ammonia denitrification and associated with low-quality water), and the OTU Colwellia rossensis (previously recorded in polluted waters) was observed. Our results suggest that nanoplastics and nano-TiO2 alone and in combination induce alterations in microbiome composition by promoting the increase of negative taxa over beneficial ones in the gills of the Antarctic soft-shell clam. An increase of two low abundance OTUs in PS-COOH NPs exposed clams was also observed. A predicted gene function analysis revealed that sugar, lipid, protein and DNA metabolism were the main functions affected by either PS-COOH NP and nano-TiO2 exposure. The molecular functions involved in the altered affiliated OTUs are novel for nano-CEC exposures
Peculiar Morphology of Montipora millepora Reveals Interspecific Competition for Space Among Two Other Major Foundation Species in Jeju Waters, South Korea
No full textAn atypical surface shape was observed in encrusting coral colonies of Montipora millepora. Initial assumptions on their origin focused on the presence of epibiotic intermediate habitat formers, such as coral-dwelling and -boring organisms. However, further investigations revealed their origin to also be substrate shape-related, prompted by overgrowing other foundation species. The unusual bumps stemmed from encrusting over specimens of the coral Alveopora japonica, and the forked, tube-like structures over holdfasts of the brown alga Ecklonia cava. Spatial distribution patterns and interspecific competition are briefly reviewed. Potential effects of morphological changes for Montipora species identification, as well as implications of altered topography in general, are mentioned
Transcriptomic responses of Antarctic clam Laternula elliptica to nanoparticles, at single and combined exposures reveal ecologically relevant biomarkers
No full textIn recent years micro- and nanoplastics and metal-oxide nanomaterials have been found in several environmental compartments. The Antarctic soft clam Laternula elliptica is an endemic Antarctic species having a wide distribution in the Southern Ocean. Being a filter-feeder, it could act as suitable bioindicator of pollution from nanoparticles also considering its sensitivity to various sources of stress. The present study aims to assess the impact of polystyrene nanoparticles (PS-NP) and the nanometal titanium-dioxide (n-TiO2) on genome-wide transcript expression of L. elliptica either alone and in combination and at two toxicological relevant concentrations (5 and 50 µg/L) during 96 h exposure. Transcript-target qRT-PCR was performed with the aim to identify suitable biomarkers of exposure and effects. As expected, at the highest concentration tested, the clustering was clearer between control and exposed clams. A total of 221 genes resulted differentially expressed in exposed clams and control ones, and 21 of them had functional annotation such as ribosomal proteins, antioxidant, ion transport (osmoregulation), acid-base balance, immunity, lipid metabolism, cell adhesion, cytoskeleton, apoptosis, chromatin condensation and cell signaling. At functional level, relevant transcripts were shared among some treatments and could be considered as general stress due to nanoparticle exposure. After applying transcript-target approach duplicating the number of clam samples, four ecologically relevant transcripts were revealed as biomarkers for PS-NP, n-TiO2 and their combination at 50 µg/L, that could be used for monitoring clams’ health status in different Antarctic localities
Productive mats of micro-algae continue to thrive with a warmer world
No full text<p>Intertidal mudflats are amongst the most productive coastal ecosystems on Earth. They are widely spread worldwide supporting food webs and many ecosystem services. Their productivity mostly relies upon mats composed of benthic micro-algae called microphytobenthos (MPB). Despite their critical importance in carbon cycling and trophic cascading, the MPB response to global warming is largely overlooked in biogeochemical models. Here, we use a numerical model to simulate the response of MPB exposed to light and temperature conditions predicted by three IPCC climate change scenarios covering years 1950 to 2099. MPB undergo important phenological shifts with the increase of mud surface temperature foreseen by the end of the century. MPB bloom up to 14 days earlier in spring and 5 days later in fall expanding by 3 weeks the low-level MPB biomass summertime period in RCP 8.5. During the 21<sup>st</sup> century, MPB net primary production (NPP) continues to thrive due to the compensation of increasing/decreasing NPP during winter/summer. The ratio SP:NPP remains unaffected by changes in MPB NPP and phenology. Therefore, we suggest that low trophic levels will be resilient in a projected warmer climate, but with a cascading effect throughout the entire food-web that remains to be assessed. Regarding the role of MPB in supporting tidal mudflats ecosystems, the model ability to infer MPB response to change in irradiance and temperature brings new insights about the fate of associated ecosystem services in a warmer climate.</p>
English in french-speaking african countries: the case of Gabon
No full textA number of historically French-speaking countries have adopted English as second or one of the official languages. This does not only pose a problem of multilingualism at State level as well as at social level, but it also questions the actual status of English as a language at both levels. In fact, English does not only have to compete with French, but also with native African languages. This article gives an insight into the status of English in Gabon – a French-speaking country in western central Africa. Gabon has not (yet) adopted English as one of the official languages, but the status of the language needs to be investigated from a sociolinguistic perspective. The paper retraced the story of English in Gabon by outlining three periods of contact between the English language and the populations of Gabon. The presence of English throughout the three periods is then linguistically attested through an empirical study of English loanwords in the general vocabulary of Gabonese native languages. The second topic that the article covers is the contemporary situation of the language in the country whose policy refers to it as foreign language. Meanwhile, the influence of the American lifestyle and music, the education system and the elites that were educated in English-speaking countries produce a different social view on the language. This growing social status may signal prominent new developments in the future. This leads the author to set perspectives of the language as it is spoken in Gabon
Environmental impact on marginal coastal benthic communities within the Jeju Island, South Korea temperate transition zone
No full textAim of studyMarine climatic transition zones are boundary areas of major climate zones, here the boundary between the subtropical and temperate zones. They present areas containing high abundance of organisms living at the limit of their physiological tolerance. These marginal populations are particularly sensitive to changes in their environment. As such, marine climatic transition zones are excellent natural playgrounds for climate change-related hypothesis testing, especially with respect to marine habitat response to ocean warming. The marginal biogenic habitats around Jeju Island, South Korea, which lies within the temperate transition zone, have gradually changed from macroalgal-dominated to hard coral-dominated habitats. Understanding the specific abiotic environmental factors that influence the distribution of the marginal populations in temperate transition zones (i.e., species at their occurrence limit) is crucial to predicting and managing temperate zone habitat changes caused by climate change. This study aims to identify the specific abiotic environmental factors that contribute to explaining the current spatial distribution of the declining temperate and expanding subtropical foundation species in Jeju waters.MethodsCoverage and composition of sessile benthic communities were determined by photo-quadrat analysis at two depths (10 m and 15 m) at three sites along the island’s south, east, and north coasts in May and November 2022. Divergences in community composition between sites were characterized in light of ten quantitative environmental parameters.ResultsOur results show that sessile foundation communities vary significantly at different sites around the island. While the south is defined by high-latitude hard corals, predominately Alveopora japonica, the east is defined by the temperate canopy-forming macroalga Ecklonia cava, and the north is characterized by coralline algae. Winter sea surface temperature, water transparency, nutrient concentration, and water movement were statistically the most impactful environmental factors determining which foundation species constitute each distinct benthic community.ConclusionThis study provides valuable baseline information on the impacts of abiotic environmental factors on marine sessile communities in a temperate transition zone
How the digestive gland of Laternula elliptica reacts to nanoplastics and nanometals, both alone and together at global gene expression and oxygen consumption level
No full textHuman activities are impacting even the most remote territories of our planet including Antarctica. The Fildes Bay coast is among those considered more at risk with increasing concern on consequences to marine life. Here we investigated the potential hazard posed by contaminants of emerging concern (CECs) as nanoplastics and nanomaterials single and in combination in filter-feeder species as the Antarctic clam Laternula elliptica. The digestive gland was used to assess the transcriptomic response meanwhile oxygen consumption modulations upon in vivo exposure to polystyrene (PS-NP-COOH) and titanium-dioxide nanoparticles (TiO2-NP) at environmental realistic concentrations as those most likely found in marine coastal waters (5 and 50 µg/L). A total of 2852 differentially expressed genes were found in clams exposed either single and in combination versus controls. The transcript functions affected were autophagy, cell cycle, proteases co-chaperones and their transcription factors, antioxidants, membrane fatty acids, cell pH balance enzymes, mitochondria stress and ATP production in PS-NP-COOH 5 µg/L, TiO2-NP 5 µg/L and 50 µg/L and co-exposure 50 µg/L. The last three treatments also had transmembrane transport enzymes and histones. The co-exposure at 5 µg/L had ribosomal proteins, protease and apoptosis transcripts affected and PS-NP-COOH 50 µg/L only had protease as transcripts with known functions. Oxygen consumption decreased significantly for the combination of pollutants at two concentrations, suggesting that this synergy provoked a diminution of clam metabolism. These results highlighted the molecular toxicity and potential stress for the Antarctic benthos key species L. elliptica
