14 research outputs found
Microplastics contamination in pearl-farming lagoons of French Polynesia and their impacts in the pearl oyster Pinctada margaritifera
Plastic pollution of the marine environment is a global environmental, health and socio-economic issue. In French Polynesia, a specific source of plastic waste is associated with pearl-farming of which farming gears have been accumulating in the lagoons for more than 40 years. This plastic deposit is likely to degrade in micro- and nanoplastics (MNP, <5 mm), leading to an ubiquitous contamination at the global scale which is of great concern for risks to marine organisms and ecosystems. The aims of this thesis were to assess microplastics (MP) contamination in pearl-farming lagoons of French Polynesia and to investigate their effects on pearl oyster (Pinctada margaritifera). Results of sampling campaigns carried out in Ahe, Manihi and Takaroa atolls revealed the ubiquity of MP in the surface water, in the water column and the cultured pearl oystersâ tissues. The concentrations recorded in surface waters (0.2 to 8.4 MP.m-3) place these atolls at an unfavorable position compared to the microplastic concentrations measured at sea. Furthermore, the water column was found to be a highly contaminated compartment (14.0 to 716.2 MP.m-3). The pearl oyster, a filter-feeding species reared between 4 and 6 meters deep, is then particularly exposed. Concentrations measured in the tissues of P. margaritifera (~ 0.3-21.5 MP.g-1 wet weight) are among the most contaminated values in marine bivalves. In order to assess the impact of MP in P. margaritifera biology and pearl quality, two in vivo experiments were carried out under controlled laboratory conditions: one involving polystyrene microbeads (standardized micro-PS) and the other involving MNP produced from pearl-farming gears collected in situ including a low level of exposure to consider more realistic scenario. Results indicated a significant impact of micro-PS and pearlfarming MNP on the energy metabolism of exposed individuals. This alteration resulted in decreased of assimilation efficiency resulting in a dose-dependent reduction in energy gain. This energetic disruption has led to gametogenesis alteration and modulation of genes expression involved in defense mechanisms. Furthermore, the pearl quality was impacted at the microstructure level of the pearl nacre deposition. A toxicological approach conducted on pearl-farming plastic gears demonstrated their chemical toxicity potential through a significant hazardous contaminantsâ desorption (e.g. phthalates) in seawater (i.e. leachates). P. margaritifera embryos were exposed to these leachates and an alteration of the embryo-larval development was observed in vitro. These results suggest that massive accumulation areas of pearlfarming gears (operational and/or discarded) could represent hotspots of chemical contaminants desorption, potentially harmful for P. margaritifera but also the surrounding biota. Overall, this thesis demonstrates a threat associated with MNP burden on the pearl oyster, the sustainability of pearl-farming industry and more broadly, on the lagoon ecosystem.La pollution plastique du milieu marin est un enjeu mondial sur le plan environnemental, sanitaire et socio-Ă©conomique. En PolynĂ©sie française, une source spĂ©cifique de dĂ©chets plastiques est associĂ©e Ă la perliculture dont les structures dâĂ©levage sâamoncellent dans les lagons depuis plus de 40 ans. Ce gisement de plastique est susceptible de se dĂ©grader sous la forme de micro- et nanoplastiques (MNP, < 5 mm) dont la contamination ubiquitaire Ă lâĂ©chelle mondiale suscite une grande prĂ©occupation Ă cause des risques quâelle reprĂ©sente pour les organismes et les Ă©cosystĂšmes marins. Les objectifs de cette thĂšse Ă©taient dâĂ©valuer la contamination microplastique (MP) dans les lagons perlicoles de PolynĂ©sie française et dâen Ă©valuer les effets sur lâhuĂźtre perliĂšre (Pinctada margaritifera). Les rĂ©sultats des campagnes dâĂ©chantillonnages rĂ©alisĂ©es in situ dans les atolls de Ahe, Manihi et Takaroa ont rĂ©vĂ©lĂ© lâomniprĂ©sence des MP dans les eaux de surface, la colonne dâeau et les tissus dâhuĂźtres perliĂšres en Ă©levage. Les concentrations enregistrĂ©es dans les eaux de surface (0,2 Ă 8,4 MP.m-3) placent ces trois atolls Ă une position trĂšs dĂ©favorable par rapport aux concentrations en MP mesurĂ©es dans le monde. De plus, la colonne dâeau sâest rĂ©vĂ©lĂ©e ĂȘtre un compartiment hautement contaminĂ© (14,0 Ă 716,2 MP.m-3). LâhuĂźtre perliĂšre, organisme filtreur Ă©levĂ© entre 4 et 6 mĂštres de profondeur, est particuliĂšrement vulnĂ©rable Ă cette contamination. Les concentrations mesurĂ©es dans les tissus de P. margaritifera (~ 0,3-21,5 MP.g-1 de chair humide) la positionne dâailleurs parmi les bivalves marins les plus contaminĂ©s. Afin dâĂ©valuer lâimpact des MP sur la biologie de P. margaritifera et la qualitĂ© de la perle, deux expĂ©rimentations in vivo ont Ă©tĂ© menĂ©es en conditions contrĂŽlĂ©es de laboratoire : lâune impliquant des microbilles de polystyrĂšne (micro-PS standardisĂ©es) et lâautre impliquant des MNP produits Ă partir de structures perlicoles rĂ©coltĂ©es in situ dont une dose dâexposition faible proche dâun scenario environnemental. Les rĂ©sultats de ces travaux ont rĂ©vĂ©lĂ© un impact important des micro-PS et des MNP perlicoles sur le mĂ©tabolisme Ă©nergĂ©tique des individus exposĂ©s. Cette altĂ©ration sâest traduite par une diminution de lâefficacitĂ© dâassimilation entraĂźnant une rĂ©duction dose-dĂ©pendante de gain dâĂ©nergie. Ce dĂ©rĂšglement Ă©nergĂ©tique sâest rĂ©percutĂ© au niveau cellulaire (i.e. altĂ©ration de la gamĂ©togĂ©nĂšse) et molĂ©culaire (i.e. modulation de lâexpression des gĂšnes impliquĂ©s dans des mĂ©canismes de dĂ©fense face au stress). Par ailleurs, la qualitĂ© de la perle sâest avĂ©rĂ©e impactĂ©e au niveau de la microstructure des dĂ©pĂŽts nacriers. Une approche toxicologique menĂ©e en parallĂšle sur les plastiques perlicoles a permis de dĂ©montrer leur potentiel de toxicitĂ© chimique Ă travers une dĂ©sorption importante dâadditifs (e.g. phtalates) dans lâeau de mer (i.e. lixiviats). Des embryons de P. margaritifera ont Ă©tĂ© exposĂ©s Ă ces lixiviats et une altĂ©ration du dĂ©veloppement embryolarvaire a Ă©tĂ© observĂ©e in vitro. Ces rĂ©sultats suggĂšrent que les zones dâaccumulation massive de structures perlicoles en plastique (opĂ©rationnelles et/ou abandonnĂ©es) pourraient reprĂ©senter des points chauds de dĂ©sorption de contaminants chimiques, impactant P. margaritifera, en contact Ă©troit avec ces Ă©quipements, mais aussi le biote environnant. Dans lâensemble, cette thĂšse dĂ©montre une menace associĂ©e aux MNP qui pĂšse sur lâhuĂźtre perliĂšre, la durabilitĂ© de son industrie et plus largement, sur lâĂ©cosystĂšme lagonaire
Microplastics Affect Energy Balance and Gametogenesis in the Pearl Oyster Pinctada margaritifera
Plastic pollution in the environment is increasing at global scale. Microplastics (MP) are derived from degradation of larger plastic items or directly produced in microparticles form (<5 mm). Plastics, widely used in structures and equipments of pearl farming, are a source of pollution to the detriment of the lagoon ecosystem. In order to evaluate the impact of MP on the physiology of Pinctada margaritifera, a species of ecological and commercial interests, adult oysters were exposed to polystyrene microbeads (micro-PS of 6 and 10 ÎŒm) for 2 months. Three concentrations were tested: 0.25, 2.5, 25 ÎŒg L-1 and a control. Ingestion and respiration rate and assimilation efficiency were monitored on a metabolic measurement system to determine the individual energy balance (Scope For Growth, SFG). Effects on reproduction were also assessed. The assimilation efficiency decreased significantly according to micro-PS concentration. The SFG was significantly impacted by a dose-dependent decrease from 0.25 ÎŒg L-1 (p < 0.0001). A negative SFG was measured in oysters exposed to 25 ÎŒg L-1. Gonads may have provided the missing energy to maintain animalsâ metabolism through the production of metabolites derived from germ cells phagocytosis. This study shows that micro-PS significantly impact the assimilation efficiency and more broadly the energy balance of P. margaritifera, with negative repercussions on reproduction
Cryogrinding and sieving techniques as challenges towards producing controlled size range microplastics for relevant ecotoxicological tests
The impact of microplastics (MP) has attracted much attention from the scientific community and many laboratory assessments have been made of their effects on aquatic organisms. To produce MP from real environmental plastic waste, which would enable more realistic experiments, we used plastic pearl farming equipment from French Polynesian lagoons. Here, the pearl oyster Pinctada margaritifera could encounter MP coming from their breakdown in its surrounding environment. We tested an established method based on mechanical cryogenic grinding and liquid sieving. Our desired size range was 20â60 Όm, corresponding to the optimal particle size ingested by P. margaritifera. The protocol was effective, generating MP particles of 20â60 Όm (âŒ17,000â28,000 MP Όgâ1), but also produced too many smaller particles. The peak in the desired size range was thus flattened by the many small particles <3 Όm (âŒ82,000â333,000 MP Όgâ1; 53â70% of total analysed particles), visible at the limit of Coulter counter analysis (cut-off point: 2 Όm). Laser diffraction analysis (cut-off point: 0.4 Όm) provided greater detail, showing that âŒ80â90% of the total analysed particles were <1 Όm. Diverging particle size distributions between those expected based on sieving range and those really observed, highlight the need to perform fine-scaled particle size distribution analyses to avoid underestimating the number of small micro- and nanoplastics (MNP) and to obtain an exact estimation of the fractions produced. Size and microstructure characterization by scanning electron microscopy suggested spontaneous particle self-assembly into crystal superstructures, which is the supposed cause of the divergence we observed. Overall, our results emphasize that particle self-assembly is a technical hurdle requiring further work and highlight the specific need to finely characterize the size distribution of MNP used in ecotoxicological experiments to avoid overestimating effects
Microplastics induce dose-specific transcriptomic disruptions in energy metabolism and immunity of the pearl oyster Pinctada margaritifera
A combined approach integrating bioenergetics and major biological activities is essential to properly understand the impact of microplastics (MP) on marine organisms. Following experimental exposure of polystyrene microbeads (micro-PS of 6 and 10âŻÎŒm) at 0.25, 2.5, and 25âŻÎŒgâŻLâ1, which demonstrated a dose-dependent decrease of energy balance in the pearl oyster Pinctada margaritifera, a transcriptomic study was conducted on mantle tissue. Transcriptomic data helped us to decipher the molecular mechanisms involved in P. margaritifera responses to micro-PS and search more broadly for effects on energetically expensive maintenance functions. Genes related to the detoxification process were impacted by long-term micro-PS exposure through a decrease in antioxidant response functioning, most likely leading to oxidative stress and damage, especially at higher micro-PS doses. The immune response was also found to be dose-specific, with a stress-related activity stimulated by the lowest dose present after a 2-month exposure period. This stress response was not observed following exposure to higher doses, reflecting an energy-limited capacity of pearl oysters to cope with prolonged stress and a dramatic shift to adjust to pessimum conditions, mostly limited and hampered by a lowered energetic budget. This preliminary experiment lays the foundation for exploring pathways and gene expression in P. margaritifera, and marine mollusks in general, under MP exposure. We also propose a conceptual framework to properly assess realistic MP effects on organisms and population resilience in future investigations
Microplastics Affect Energy Balance and Gametogenesis in the Pearl Oyster <i>Pinctada margaritifera</i>
Plastic
pollution in the environment is increasing at global scale.
Microplastics (MP) are derived from degradation of larger plastic
items or directly produced in microparticles form (< 5 mm). Plastics,
widely used in structures and equipment of pearl farming, are a source
of pollution to the detriment of the lagoon ecosystem. To evaluate
the impact of MP on the physiology of <i>Pinctada margaritifera</i>, a species of ecological and commercial interests, adult oysters
were exposed to polystyrene microbeads (micro-PS of 6 and 10 ÎŒm)
for 2 months. Three concentrations, 0.25, 2.5, and 25 ÎŒg L<sup>â1</sup>, and a control were tested. Ingestion and respiration
rate and assimilation efficiency were monitored on a metabolic measurement
system to determine the individual energy balance (Scope For Growth,
SFG). Effects on reproduction were also assessed. The assimilation
efficiency decreased significantly according to micro-PS concentration.
The SFG was significantly impacted by a dose-dependent decrease from
0.25 ÎŒg L<sup>â1</sup> (<i>p</i> < 0.0001),
and a negative SFG was measured in oysters exposed to 25 ÎŒg
L<sup>â1</sup>. Gonads may have provided the missing energy
to maintain animalsâ metabolism through the production of metabolites
derived from germ cells phagocytosis. This study shows that micro-PS
significantly impact the assimilation efficiency and more broadly
the energy balance of <i>P. margaritifera</i>, with negative
repercussions on reproduction
Pearl Farming Micro-Nanoplastics Affect Oyster Physiology and Pearl Quality
International audiencePearl farming is crucial for the economy of French Polynesia. However, rearing structures contribute significantly to plastic waste, and the widespread contamination of pearl farming lagoons by microplastics has raised concerns about risks to the pearl industry. This study aimed to evaluate the effects of micro-nanoplastics (MNPs, 0.4â200 ÎŒm) on the pearl oyster (Pinctada margaritifera) over a 5-month pearl production cycle by closely mimicking ecological scenarios. MNPs were produced from weathered plastic pearl farming gear and tested at environmentally relevant concentrations (0.025 and 1 ÎŒg Lâ1) to decipher biological and functional responses through integrative approaches. The significant findings highlighted the impacts of MNPs on oyster physiology and pearl quality, even at remarkably low concentrations. Exposure to MNPs induced changes in energy metabolism, predominantly driven by reduced assimilation efficiency of microalgae, leading to an alteration in gene expression patterns. A distinct gene expression module exhibited a strong correlation with physiological parameters affected by MNP conditions, identifying key genes as potential environmental indicators of nutritional-MNP stress in cultured oysters. The alteration in pearl biomineralization, evidenced by thinner aragonite crystals and the presence of abnormal biomineral concretions, known as keshi pearls, raises concerns about the potential long-term impact on the Polynesian pearl industry
La perliculture de Polynésie française menacée par les microplastiques
National audienceLa pollution plastique du milieu marin est un enjeu mondial sur le plan environnemental, sanitaire et socio-Ă©conomique. En PolynĂ©sie française, une source spĂ©cifique de dĂ©chets plastiques est associĂ©e Ă la perliculture dont les structures dâĂ©levage sâaccumulent dans les lagons depuis plus de 40 ans. Ce gisement de plastique est susceptible de se dĂ©grader sous la forme de micro- et nanoplastiques (MNP, < 5 mm) dont la contamination ubiquitaire Ă lâĂ©chelle mondiale suscite une grande prĂ©occupation Ă cause des risques quâelle reprĂ©sente pour les organismes et les Ă©cosystĂšmes marins. La contamination en MP a Ă©tĂ© Ă©valuĂ©e dans les lagons perlicoles ainsi que leurs impacts sur lâhuĂźtre perliĂšre (Pinctada margaritifera) en conditions de laboratoire. Cependant, comme la plupart des Ă©tudes dâimpact Ă ce jour, ces phases dâexposition aux MP Ă©taient limitĂ©es aux particules standards (microbilles). Afin de mieux apprĂ©hender les risques associĂ©s aux MNP, des huĂźtres perliĂšres ont Ă©tĂ© exposĂ©es pendant 5 mois Ă des MNP produits Ă partir de structures perlicoles collectĂ©es in situ, Ă des doses prochent dâun scenario environnemental, tout en simulant le cycle de production dâune perle. Un impact sur le mĂ©tabolisme Ă©nergĂ©tique de P. margaritifera a pu ĂȘtre observĂ© ainsi quâune modulation de lâexpression des gĂšnes impliquĂ©s dans la rĂ©ponse immunitaire et les mĂ©canismes de dĂ©toxification. La qualitĂ© de la perle a Ă©galement Ă©tĂ© altĂ©rĂ©e au niveau de la microstructure des dĂ©pĂŽts nacriers. Dans l'ensemble, ces rĂ©sultats dĂ©montrent une menace associĂ©e aux MNP qui pĂšse sur lâhuĂźtre perliĂšre, la durabilitĂ© de son industrie et plus largement, sur lâĂ©cosystĂšme lagonaire
Validation of the rapid assessment procedure for loiasis (RAPLOA) in the democratic republic of CongoS
Background: A simple method called RAPLOA, to rapidly assess what proportion of people in a community are infected with L. loa and hence which communities are at high risk of severe adverse reactions following ivermectin treatment, was developed in Cameroon and Nigeria. The method needed further validation in other geographical and cultural contexts before its application in all endemic countries. The present study was designed to validate RAPLOA in two regions in the North East and South West of the Democratic Republic of Congo. Methods: In each study region, villages were selected from different bio-ecological zones in order to cover a wide range of loiasis endemicity. In each selected community, 80 people above the age of 15 years were interviewed for a history of eye worm (migration of adult L. loa under the conjunctiva of the eye) and parasitologically examined for the presence and intensity of L. loa infection. In total, 8100 individuals from 99 villages were enrolled into the study. Results: The results confirmed the findings of the original RAPLOA study: i) the eye worm phenomenon was well-known in all endemic areas, ii) there was a clear relationship between the prevalence of eye worm history and the prevalence and intensity of L. loa microfilaraemia, and iii) using a threshold of 40%, the prevalence of eye worm history was a sensitive and specific indicator of high-risk communities. Conclusion: Following this successful validation, RAPLOA was recommended for the assessment of loiasis endemicity in areas targeted for ivermectin treatment by lymphatic filariasis and onchocerciasis control programmes
La perliculture de Polynésie française menacée par les microplastiques
National audienceLa pollution plastique du milieu marin est un enjeu mondial sur le plan environnemental, sanitaire et socio-Ă©conomique. En PolynĂ©sie française, une source spĂ©cifique de dĂ©chets plastiques est associĂ©e Ă la perliculture dont les structures dâĂ©levage sâaccumulent dans les lagons depuis plus de 40 ans. Ce gisement de plastique est susceptible de se dĂ©grader sous la forme de micro- et nanoplastiques (MNP, < 5 mm) dont la contamination ubiquitaire Ă lâĂ©chelle mondiale suscite une grande prĂ©occupation Ă cause des risques quâelle reprĂ©sente pour les organismes et les Ă©cosystĂšmes marins. La contamination en MP a Ă©tĂ© Ă©valuĂ©e dans les lagons perlicoles ainsi que leurs impacts sur lâhuĂźtre perliĂšre (Pinctada margaritifera) en conditions de laboratoire. Cependant, comme la plupart des Ă©tudes dâimpact Ă ce jour, ces phases dâexposition aux MP Ă©taient limitĂ©es aux particules standards (microbilles). Afin de mieux apprĂ©hender les risques associĂ©s aux MNP, des huĂźtres perliĂšres ont Ă©tĂ© exposĂ©es pendant 5 mois Ă des MNP produits Ă partir de structures perlicoles collectĂ©es in situ, Ă des doses prochent dâun scenario environnemental, tout en simulant le cycle de production dâune perle. Un impact sur le mĂ©tabolisme Ă©nergĂ©tique de P. margaritifera a pu ĂȘtre observĂ© ainsi quâune modulation de lâexpression des gĂšnes impliquĂ©s dans la rĂ©ponse immunitaire et les mĂ©canismes de dĂ©toxification. La qualitĂ© de la perle a Ă©galement Ă©tĂ© altĂ©rĂ©e au niveau de la microstructure des dĂ©pĂŽts nacriers. Dans l'ensemble, ces rĂ©sultats dĂ©montrent une menace associĂ©e aux MNP qui pĂšse sur lâhuĂźtre perliĂšre, la durabilitĂ© de son industrie et plus largement, sur lâĂ©cosystĂšme lagonaire