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    • Oysters with a plastic flavor in your plates for your celebrations!by Léa Bascoul, Vincent Dumontet and Sophia Lestringuez

      Published by Charlotte Recapet the November 8, 2021 on 5:52 PM

      For over half a century, global plastic production has increased exponentially. Plastics represent 50% to 80% of marine litter. Microplastics (MP) are derived from the degradation of larger plastic articles or directly produced as microparticles (< 5 mm). Oceans have a “funnel” effect concerning MP drained from rivers and streams, they concentrate pollution from fresh waters in the oceans. In pearl farming structures and equipment, the use of plastics is a source of pollution to the detriment of the lagoon ecosystem. Due to their ubiquitous and small dimensions, MP are likely to be ingested by many organisms and in particular by the oyster, Pinctada margaritifera (Figure 1), which is a species of ecological and commercial interest. So, the objective of the study is to assess the impact of these microplastics on the physiology of this oyster species from the pearl lagoon of Ahe atoll, in the waters of French Polynesia (Figure 2).

      Figure 1: Pinctada margaritifera

      Figure 2: Ahe atoll localisation

      In order to assess the effects of these molecules, IFREMER from French Polynesia, recreated microcosms [1] where oysters are exposed to polystyrene microbeads. Indeed, polystyrene is one of the most widely used plastic polymers and the most found in marine ecosystems.

      After two weeks of depuration, oysters, were divided into three treatments. For each, 24 oysters were exposed to polystyrene solutions for two months. These solutions were a mixture of polystyrene microbeads of different diameters (6 and 10 μm) at equal weight. A control was carried out without exposure to polystyrene. Each tank, kept homogeneous, was exposed for 12 hours a day to light and the physico-chemical parameters were kept constant. The microplastic solution was injected continuously into the tanks associated with a mixed diet of two microalgae (Tisochrysis lutea and Chaetoceros gracilis).

      Figure 3: Experimental exposure device of oysters to microplastics

      During the experiment (Figure 3), various parameters, like oxygen consumption, were measured to assess the different energy expenditure of the oyster. Expenses related to food (ingestion rate and assimilation efficiency), to growth (the scope for growth defined from the energy budget and the shell growth rate) as well as those allocated to reproduction (characterization gonad [2] size and analysis of gametogenesis [3]) are quantified in each experimental group and compared to the control. The measurements were carried out on eight oysters per treatment after one month and then at the end of the experiment.

      This experiment made it possible to demonstrate that at low MP concentrations, pearl oysters suffer adverse consequences for the sustainability of their populations. In fact, the metabolic responses of a stressed organism can lead to an increase in an individual's energy costs, forcing the organism to sacrifice some of its energy normally allocated to functions, such as growth or reproduction.

      In this classical and standardized experiment, the oysters exhibited a significant dose-dependent reduction in the “scope for growth” without however modifying the shell deposit rate. On the other hand, although the ingestion rates of the microalgae were not affected by the microplastics, for an equal volume of filtered water the assimilation of the microalgae is disturbed by the presence of the microplastics and the energy supplied by food is lower. This is either linked to interference in assimilation processes in the digestive tract or to indirect competition between algae and microplastics.

      The fact that metabolic (respiration) rates are not impacted suggests that the only possibility for the oyster to cope with a decrease in available energy is to modify its gametogenesis and / or its reproductive effort. However, reproduction in P. margaritifera is continuous and requires a lot of energy. The results of the study show that reproductive effort is not affected but that gametogenesis is strongly impacted. Thus “small holes” in the gonadal tubules [4] are observed in oysters exposed to microplastics. They could therefore be the start of the phagocytosis [5] of germ cells initiated to recover energy (Figure 4).

      Figure 4: Impact on P. margaritifera metabolism

      In a few words, the pearl oyster exposed to MP for a period of two months maintains its metabolism and its vital functions to the detriment of its reproduction, and therefore the sustainability of its future population.

      This study could also serve as a model for the MSFD [6] Technical Group Marine Litter to assess the effects of microplastic litter in biota (D10C3), because the effects observed on Pinctada margaritifera in the lagoon of French Polynesia must be the same as on other filter feeding bivalves in Europe. The European Technical Group Marine Litter could thus propose a regulation of waste at the European level and not only at the level of the lagoon of French Polynesia.

      The experiment results should support decision-making on plastic waste management measures in Polynesian lagoons, especially in atolls that have decades of pearl culture history without waste regulation or clean-up. This work would provide the necessary information to local authorities to regulate pearl equipment and establish a waste management policy such as the collection and recycling of this equipment.

      The aim of the study was to measure the impact of microplastics on the metabolism of Pinctada margaritifera. The team of researchers therefore sought to artificially recreate different levels of pollution in the laboratory. This methodology is suitable because it aims to recreate the pollution conditions possibly encountered in natural environments. To measure these different levels of pollution, the experiment is carried out at different concentrations. As for the various parameters measured to assess energy losses, they make it possible to identify, in a non-invasive manner, the functions (growth and reproduction) "sacrificed" to cope with the loss of energy. They also allow us to see if this loss of energy had an effect on the metabolism of oysters. The parameters monitored therefore seem consistent for this study and could be used for similar studies on other bivalve filter-feeding organisms. Experiments using this protocol could be considered in fresh waters with other types of bivalves such as the mussel pearl (Margaritifera margaritifera). Also, this study can be evaluated with a direct approach on oysters from pearl farms and over several generations.

      In several years, oyster populations on a global scale could be impacted by pollution from microplastics … so, if there are no more oysters, what will we eat with our white wine?

      Read the full study: Gardon T., Reisser C., Soyez C., Quillien V. & Le Moullac G (2018). Microplastics Affect Energy Balance and Gametogenesis in the Pearl Oyster. Environmental Science & Technology. 52(9), 5277‑5286.

      [1] smaller version of ecosystem

      [2] an animal organ in which gametes (a haploid germ cell, such as a spermatozoon or ovum) are produced

      [3] gamete formation process

      [4] organs of gametes excretion

      [5] cellular defense process, destructive function of phagocytes

      [6] Marine Strategy Framework Directive

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    • Does food quality increases moult organism vulnerability to pollutant impacts? by Charlotte Couedel, Axel Rochaud and Stellia Sebihi

      Published by Charlotte Recapet the April 27, 2021 on 9:06 AM

      Today's ecotoxicology

      For a long time, ecotoxicology focused on the lethal effects of pollutants, with increased individual mortality translating into smaller population size or population extinction. There has been a shift from the study of lethal doses to the impact of smaller doses on more specific processes such as physiology and behaviour (Rand and Petrocelli, 1985; Døving, 1991). The article deals with the effect of pollutants on moulting.

      Possible use of ecotoxicology (the case of the article)

      Pollutants are an environmental factor causing stress in individuals. Lack of resources is another factor. For this reason, the study attempts to demonstrate and quantify the impact of food quality on the resistance to pollutants of moulting organisms.

      Hypotheses of the effect of the diet on the assimilation and detoxification of pollutants

      When a pollutant is assimilated by an organism, the body sets up the detoxification system, but it requires energy. Food allows the assimilation of energy by organisms. Good quality of food makes an individual capable of accumulating the energy necessary to ensure vital functions. An organism with energy from good quality food, should be able to activate an effective detoxification. Thanks to this detoxification, the body should be less impacted by pollutants. The study seeks to demonstrate whether this is true.

      Hypotheses illustration

      The interest of the biological model

      Gammaridae are macro-invertebrates that are mainly detritus feeders. They feed on detritus, corpses, living or decaying plants. Moreover, they are at the base of the human food chain as they are often industrially bred as fish food. Gammaridae are used to determine the biological quality of watercourses. They are rather pollution tolerant organisms but are nevertheless affected by pollution. Could the physiological changes noticed in Gammaridae be noticed in humans?

      A picture of two Gammaridae

      Way to understand the effects

      The experiment is designed to evaluate single and combined effects of leaf litter stoichiometric quality and Cd exposure on G. fossarum survival and growth. Phosphorus (P) is used as the nutrient in leaf litter. Cadmium (Cd) is used as the pollutant. Phosphorus (P) is a nutrient naturally present in the Gammaridae's food, in this case, leaf litter. Also, industrial activities are often sources of cadmium released into aquatic environments. The main route of exposure to cadmium (Cd) is through the ingestion of contaminated water and food, so Gammaridae is particularly exposed to this type of pollutant.

      The experiment design

      144 microcosms were performed for each of the 3 levels of Cd concentrations (0 ; 0.35 ; 0.7). For each group, 72 microcosms were realised with Sycamore discs and 72 with Alder discs. It allows to observe the effect in different conditions. Then, among these 72 microcosms, three batches of 24 have been realized. The first batch is a control batch where the composition of the litter was not modified. The second batch was a P- batch, where the litter was deficient in phosphorus and therefore in nutritional value (and which does not allow individuals to extract a lot of energy). Finally, the third lot was P+, it was enriched in phosphorus, the nutritional value is very good.

      Several metrics were measured to validate the initial hypotheses. The metrics were chosen for their relevance to evaluate organisms sensitivity to resources quality (leaf species and P content) and pollutant (Cd concentration in water): Cd bioaccumulation and survival rate. But also for their ecological importance: time-to-death, mass growth, time to moult and feeding rate.

      Results to remember

      • The Gammaridae's moult frequency and growth is amplified by a nutrient-rich diet (P+).
      • A presence of pollutants (cadmium) in the Gammaridae’s life site reduces their growth and raise their probability of death.
      • A nutrient-rich diet amplified effects of cadmium.
      • If we make the connection: The higher quality of food ressources, the more moulting there is and the greater the effect of cadmium. So moulting makes Gammaridae vulnerable to pollutants.
      • Species sensitivity to pollutants might be underestimated in ecosystems facing both nutrient constraint and pollutant.

      Schematization of the main results

      What to infer from this experiment.

      The presence of pollutants in the water causes problems in the survival of Gammaridae. Ecotoxicologists are well aware of the bioaccumulation of pollutants in the food chain. As a result, a predator will be more contaminated by the pollutants than is prey. Indeed, predators will keep in them the majority of the pollutants present in their prey. Thus, humans present in the upper part of the trophic chain will be much more contaminated than the Gammare.

      So why discharge pollutants into the water? Let's drink it directly!

      Read the full study: Arce-Funck, J., Crenier, C., Danger, M., Billoir, E., Usseglio-Polatera, P., and Felten, V. (2018) High stoichiometric food quality increases moulting organism vulnerability to pollutant impacts: An experimental test with Gammarus fossarum (Crustacea: Amphipoda), Science of The Total Environment, 645, 1484-1495,

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    • A new way to understand the effects of toxic compoundsby Flore Emonnot and Anne Michaud

      Published by Charlotte Recapet the September 7, 2020 on 8:07 AM

      Water pollution is a major concern. It can be induced by many elements. For example, Cadmium (Cd) which belongs to the heavy metals family can be source of pollution in certain concentrations. This element is naturally present in the environment, but the use of agricultural chemicals has been indicated as the main anthropogenic source of Cd pollution in aquatic environments. The organisms living in these aquatic ecosystems are exposed to this pollution. Moreover, this compound is bioaccumulated in organs and tissues, so it can induce damages. 

      Daphnia magna

      That is why it is important to evaluate the effects of this pollutant on organisms. Daphnia magna (a cladoceran crustacean) is one of the most widely used animals in aquatic toxicology. In terms of sensitivity to toxic substances, it is generally thought to be representative of other zooplankters (Anderson, 1944).  It plays an important role in the balance of an ecosystem, because of its position on the first levels of the food chain. Also, D. magna enhances water purification by filtering water and retaining food particles, it is its way to eat. This animal spends its whole life in a variety of freshwater environments.  As long as the conditions remain favourable, it reproduces predominantly by parthenogenesis.

      Bioassays are used in aquatic toxicology to provide individual-level information, while ecotoxicology is assessing the impact of pollution on populations. The DEB theory (Dynamic Energy Budget) is a theory that describes the aspects of metabolism (energy and mass budgets) at the individual level. Food assimilation results in energy, which can then be used for reproduction, growth or maintenance (life-history traits). The DEBtox is a toxicological application of the DEB theory which attempts to assess the effects of pollutants on life-history traits over time.

      The key challenge is how to infer the impact of toxic effects observed in individuals and apply it to an entire population. Elise Billoir and her team combined the following tools to extrapolate the individual effects to the entire population:

      The DEBtox is a good way of modeling survival, reproduction and growth continuously as a function of time and exposure concentration and at the individual level.

      The population growth rate (which incorporates lethal and sublethal effects), is the best parameter to evaluate the risk of a pollutant on a population, hence matrix population models are a useful tool. Billoir explains that in population matrix, population is divided into classes based on development stage, and individuals transfer from a class to the next one depending on their survival and their fecundity.

      By combining DEBtox theory and matrix population models, it is possible to extrapolate every effect of the toxic compound on the individual to the population level (as explained in the synthetic diagram below). 

      This technique used by Billoir, has not yet been used in an ecotoxicological context. It consists of reorganizing all the age-specific information in a stage-specific way. This way it makes possible to compare the sensitivity in the face of cadmium and in relation to the age of the individual. 

      Diagram of the method developed in the study of Billoir et al.

      In this case, the sensitivity analyses showed that the effects of cadmium at the individual level were not significant but the application of the model proved that the population growth rate is highly affected through the cadmium contamination. Moreover, we think that this model could be applied to similar aquatic organisms and other pollutants such as heavy metals and could be useful to enhance existing bio-indicators of water quality.

      Read the full study: Billoir, E., Péry, A.R.R. , and Charles, S. (2007) Integrating the lethal and sublethal effects of toxic compounds into the population dynamics of Daphnia magna: A combination of the DEBtox and matrix population models. Ecological Modelling, 203(3–4), 204-214.

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    • Microplastics: no effect on the productivity of the marine environment?!by Amaelle Bisch and Anaelle Bouloy

      Published by Charlotte Recapet the July 6, 2020 on 2:45 PM

      According to the paper: “Do microplastics affect marine ecosystem productivity?” by Troost et al. 2018, microplastics would have almost no effect on primary and secondary production, or at least this effect could not be demonstrated! 

      But what are microplastics?

      Plastics appeared at the beginning of the 20th century and quickly became indispensable in everyday life. Plastics are composed of polymers (long carbon chain) of synthetic or natural origin. Microplastics are plastic particles smaller than 5 mm (. There are two types of microplastics: primary (directly manufactured at this size) and secondary (resulting from the degradation of macroplastics). The major disadvantage of microplastics is that they are easily ingested by marine biota (2,3).




      Primary production, the basic link in a long chain 

      Primary producers are at the base of the trophic chain. They are autotrophic organisms that produce their organic matter from a light (photosynthesis) or mineral source. In the marine environment, these organisms correspond to algae, phytoplankton and cyanobacteria and are the basis for zooplankton feeding. Zooplankton are secondary producers and heterotrophic organisms unable to synthesize their organic matter.



      How can microplastics affect these organisms?

      In most of laboratory experiments, the impacts showed on plankton, they were for primary producers an inhibition on the algae growth, chlorophyll content and photosynthesis (4,5,6). For zooplankton, it was observed a reduced food consumption and an increasing in energy consumption with a low allocation of this energy for growth (7,8). But these effects depend to the species of plankton and the nature of microplastics (9). However, are these observations noted in the laboratory really transposable to the ecosystem scale?

      The models spoke...

      The study by Troost et al. (1) shows, by means of modelling, that at the level of primary production (algal biomass) there is no significant impact of microplastics. Indeed, this can be explained by different theories: (i) environmental conditions (availability of nutrients and light) already strongly impact the growth of algae, (ii) a transport technique (advection) would provide some protection.

      Concerning zooplankton, or secondary production, the impact of microplastics is considered low over the entire North Sea because the observed changes are both positive and negative and therefore compensate each other. Exposure to microplastics leads to changes in spatial patterns and strangely enough the impact is not greatest in areas with the highest concentration of microplastics. Surprising but not so much because this can be explained simply by the small concentrations of algae found in off-shore areas (areas with the least concentration of microplastics) making zooplankton more sensitive to any change.

      And how they have managed to demonstrate that?

      The difficulty lies in a successfully integration of the data observed in the laboratory into an ecosystem-scale model. They modelled biogeochemical transport, hydrodynamics, nutrient inputs from rivers, primary production, zooplankton biomass and also microplastic concentrations in the North Sea. In the end, the results obtained are only based on modelling and could not be verified in the field, so the conclusions should be "swallowed" with caution.

      Cited articles

      1. Troost, A., Desclaux T., Leslie, A., Van Der Meulen, M., Dick Vethaak, A., 2018. Do microplastics affect marine ecosystem productivity? Marine Pollution Bulletin 135 (2018) 17–29
      2. Ivar do Sul, J., Costa, M.F., 2014. The present and future of microplastic pollution in the marine environment. Environ. Pollut. 185, 352–364. envpol.2013.10.036.
      3. GESAMP, 2016. Sources, fate and effects of microplastics in the marine environment: part two of a global assessment. In: Kershaw, P.J., Rochmann, C.M. (Eds.), IMO/FAO/ UNESCO-IOC/UNIDO/WMO/IAEA/UN/ UNEP/UNDP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection. Rep. Stud. 2016pp. 220 GESAMP No. 93.
      4. Zhang, C., et al., 2017. Toxic effects of microplastic on marine microalgae Skeletonema costatum: interactions between microplastic and algae. Environ. Pollut. 220, 1282–1288.
      5. Sjollema, S.B., et al., 2016. Do plastic particles affect microalgal photosynthesis and growth? Aquat. Toxicol. 170, 259–261.
      6. Casado, M.P., et al., 2013. Ecotoxicological assessment of silica and polystyrene nano-particles assessed by a multitrophic test battery. Environ. Int. 51, 97–105.
      7. Watts, A.J., et al., 2015. Ingestion of plastic microfibers by the crab carcinus maenas and its effect on food consumption and energy balance. Environ. Sci. Technol. 49, 14597–14604.
      8. Van Cauwenberghe, L., et al., 2015. Microplastics are taken up by mussels (Mytilus edulis) and lugworms (Arenicola marina) living in natural habitats. Environ. Pollut. 199, 10–17.
      9. Wenfeng Wang, Hui Gao, Shuaichen Jin, Ruijing Li, Guangshui Na, 2019. The ecotoxicological effects of microplastics on aquatic food web, from primary producer to human: A review. Ecotoxicology and Environmental Safety 173, 110–117

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    • Are pesticides more dangerous when you are hungry?by Angèle Lorient

      Published by Charlotte Recapet the January 6, 2020 on 1:52 PM

      Today, the impact of pesticides on our environment is a central issue in many publications and a major concern for all citizens. Between 2014 and 2016 the use of pesticides increased by 12%. Indeed, intensive farming currently used implies that we find in our food, in the air but also in water, traces of pesticides. A 2013 Inserm report highlights a link between exposure to pesticides and the appearance of cancer or pathology such as Parkinson's disease but also developmental problems on children. Therefore, they harm the health of humans but also the entire terrestrial and aquatic ecosystems.

      Water Flea Daphnia Magna.

      In addition to using a large amount of chemicals, modern farming methods make soils less permeable. As a result, precipitation runoff is a major contributor to pesticide pollution from our streams. In order to study the toxicity of pesticides in the aquatic environment, the majority of laboratories use Daphnia as an indicator of water quality, and in particular the species Daphnia magna for their sensitivity to toxins.

      Daphnies are small crustaceans measuring about 1 to 4 millimeters. They live mainly in fresh water (river, pond, lakes). They are filter feeders that help maintain the clarity of the water thanks to their ability to eat green algae. During a day they move between the bottom and the surface of the water depending on the light (photoperiod).

      In 2006 a study was conducted by 4 scientists (2) to study the physiological responses (sensitivity, growth, reproduction) of daphnies to different dietary concentrations of the same pesticide to which they and their mothers were subjected. (high food or low food).

      The study shows that lack of food does not play a direct role in the sensitivity of daphnies to the pesticide in question. However, it is one of the factors determining the level of absorption and elimination of this toxic substance by the body. In addition, the energy used to fight this toxin has a negative effect on the maintenance of vital functions.

      In a period of low availability of food resources, invertebrates will have a more limited growth and a lower reproductive rate in proportion to the level of pesticide present in their environment. While the impact is less when they are subject to sufficient food resources (Fig 1).

      For the different types of food resource, the effect of the pesticide concentration is proportional to the survival rate. On the other hand, we can notice that there is a threshold effect concerning growth and reproduction.

      However, they also highlighted that these individuals, when no longer subject to the pesticide, found a normal activity (resilience).

      This study makes it possible to highlight the potential impacts on the results of the experiments if certain non-standardized conditions vary between laboratories (concentration of food, respect of the photoperiod). As well as the differences in test organism responses between conventional environmental conditions (controlled artificial environment) and the natural environment (subject to variations).

      The analysis of the results of this study raises the following questions:

      • What is happening in the longer term?
      • Does the repeated presence of pesticide pulses have the same physiological effects on an individual throughout his life?
      • Is the speed of resilience due to the species or can it vary individually?
      • Is there resiliency of newborns from underfed mothers?

      It also shows the urgency of taking into account the impacts of pesticides, both on our current health, on the heritage that we will transmit, but also on our ability to reproduce. Despite the mobilization of the Ministry of Agriculture including the program "Ambition bio 2017" there is urgency. Pesticides are one of the main causes of pollution in our waterways. This pollution endangers aquatic life, as has been demonstrated, but also the drinking water resource. Should not our entire consumption system be called into question in order to be able to realistically implement the planned management plans?

      Cited study: Pieters, B.J., Jager, T., Kraak, M.H.S., Admiraal, W. (2006) Modeling responses of Daphnia magna to pesticide pulse exposure under varying food conditions: intrinsic versus apparent sensitivity. Ecotoxicology 15, 601–608.

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    • Can new ecosystems develop in metal contaminated soils?by Robin Brouat and Théo Garcia

      Published by Charlotte Recapet the December 2, 2019 on 1:38 PM

      A recent study revealed that gray birch has interesting characteristics in ecological restoration, which allow the tree to support high metal contaminated soils.

      What is the experiment?

      Whereas the majority of scientists were kept in their laboratory testing contaminant, a group of American biologists performed an experiment in the field, a full-scale exercise.  In Jersey City, they measured a lot of photosynthetic parameters, in gray birch (Betulia populifolia) in two different conditions in Liberty State Park: One with High trace Metal Loads (HML) and the second with Low trace Metal Loads (LML). It results that none measured biophysical parameters vary. The only parameter that varied significantly was the leaf mass per area which decreased when the tree was in contaminated soil. This result can have two main explications. The first is that photosynthesis will no longer be affiliated with leaves but with other organs such as roots. The second is the fact that the tree will renew its leaves more often and this will impact its growth rate.

      Photo by Charlie Hohn

      Photograph by Richtid

      What is the link with ecological restoration?

      Gray birch can capture trace metals through their leaves and roots. This allows partial decontamination of areas polluted by heavy metals. Nevertheless, it is necessary to seed the plots after contamination so that only trees with a genotype with a high tolerance for trace metal concentrations grow. However, this decontamination by trees will not be possible anywhere in the world because trees are less efficient to get trace metals pollution in areas of high temperature and drought.

      It’s wonderful, but where is the new ecosystem promised?

      Yes, we are coming here. We can see an ecosystem like a pyramid with at its base the plants (also called primary producer) which convert the solar energy in organic matter for the higher steps of the trophic chain. In the study, the scientists explain that the diminution of leaf mass per area in HML affects the energy in entrance to the ecosystem. If less energy enters in the ecosystem, the whole ecosystem will be affected.

      Pretty cool! So what species could we find here?

      In theory this will be happened. But in practice, it could be quite different. Indeed, the diminution of Leaf Mass per Area is significantly, but does it could have a really impact on the ecosystem? The diminution it’s approximately 10g.m-2 and it’s not very well documented in the paper how this diminution could have an impact. In addition, we have just information about one species of primary producer; in a temperate forest we can found several tens of species which can do photosynthesis housing an animal diversity. For having a better idea of what kind of forestall ecosystem we can obtain, it seems better study the whole vegetal community of the site, and not simply a unique species.

      Hum, so this forest is not different than another one… So bad…

      Nevertheless, this study is interesting, and allows us to see the adaptation capacity of a specific tree to contaminated conditions. The gray birch is commonly used in ecological restoration, and the study proves that the species is robust for this type of projects. In the future, it will be frequent to walk in a forest, in a place in which in the past there was an industrial zone, without realizing the past of this forest. When local people will tell you that, before, there were factories. You will see the forest with a different way. And for this it will be a different forest for you. And it’s the more important.

      Cited study: Salisbury, A.B., Gallagher, F.J., Caplan, J.S., and Grabosky, J.C. (2018) Maintenance of photosynthesis by Betula populifolia in metal contaminated soils, Science of The Total Environment 625,1615-1627,

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    • Zinc pollution of our rivers: shrimp on alertby Lucille Baron and Macha Joanin

      Published by Charlotte Recapet the August 12, 2019 on 10:03 AM

      No, we will not make an exhaustive catalog of the pollutants that affect our streams and boredom will not settle in your heads by reading us. Instead, we have chosen to discuss the effect of one of the very present emerging pollutants zinc on Gammarus pulex, through the study of Maltby and Naylor (1990).

      At present, world zinc production is over 13,000 kilotons (2018). Zinc is commonly used in metal corrosion coatings and for the manufacture of fertilizers and pesticides (European Commission, 2008b). Thanks to its physico-chemical properties, zinc melts particularly in fresh water, and it is absorbed on suspended solids and sediments (INERIS, 2014). All organisms living in these ecosystems are therefore exposed to this pollution and therefore, indirectly, we too, human.

      Thus, it is important to measure the risks of this exposure on organisms and especially to know the effects of zinc on populations in the long term. For this, researchers have studied, experimentally, the energy deployed in the reproductive mechanisms by aquatic organisms exposed to zinc at different concentrations. In additions, they sought to know if exposing females during a first brood (called current) could have an effect on their second brood unexposed (called subsequent).

      Gammarus pulex is a sentinel species, not only because this shrimp is abundant in fresh waters of England, but in addition it is fed with particulate matter which constitutes, in the natural environment, a large zinc stock. To measure the risks of maintaining the species and the genetic heritage of each individual under the effect of zinc, it is sufficient to study the offspring of females exposed to this compound at different concentrations. The number of individuals which hatched, and the size of each one give some indication of the energy allocated to reproduction. That's what researchers at the British Ecological Society did. If you haven’t understood anything about our attempt to explain the methods used to carry out the study experience, here is a summary diagram that you may be clearer!

      The results they obtained are surprising and show that exposure to zinc (even at low concentrations) significantly increases the number of broods aborted. This result is related to the decline of foods assimilated by females when they are exposed to zinc. The total energy drawn from food is no longer sufficient to sustain metabolic needs while maintaining the mechanisms of maturation and reproduction. Nevertheless, when exposed females carry her brood to term, the number of offspring of each does not seem to vary, despite of the difference in duration of exposure. So, a small criticism of the Figure which represent the percentage of broods aborted in function of the concentration of zinc (Figure 3) can be realize : we found in the control situation (not exposed to zinc), a great variability between the two categories tested. So, in science when the" control "already has significant variability, the results should be interpreted with caution thus it is difficult to conclude to a difference between the current and the subsequent.

      The results concerning the size variation of the descendants, bring a complementarity to this analysis because the researchers observe a reduction of the size in the generations following the exposure. It is the reduction of the available energy (females stopping feedings) which as a consequence the reduction of the size of the individuals of the next brood. Also, on this point, it is unfortunate that the study does not take into account the size of the female that could have an impact on the size of the offspring (Taïr-Abbaci K., 2016).

      The increase of the number of broods aborted and the decrease of the size can have a negative impact on the fitness of populations as exposure to zinc increases abortion. Also, the smallest offspring will take longer time to mature and under stress conditions, this phenomenon may be aggravated over generations and the snowball effect may strongly decreased fitness of individuals. Ultimately, these effects can have a profound impact on the entire population.

      The study seems relatively far from reality since it remains experimental, in the laboratory, and is not carried out in a natural environment and therefore with real conditions of experimentation and exposure to zinc. Thus, the adaptations set up or not by the organisms and the cocktail effects (potential combined effect of different compounds) are not taken into account.

      Nevertheless, the study above begins to be old, the latter dating back to 1990.Today, techniques allow to observe the embryonic development precisely and it turns out that during the different embryonic stages aberrations can appear (Bach et al., 2010). Then, it is difficult to think that abortion is the only response implemented by females when exposed to these chemical compounds. 

      In addition, reproductive success does not depend solely on embryonic development. It is important to consider the energy allocated to ovocyte development and the search for sexual partners to define the impact of zinc on the Gammarus pulex cohorts.

      It’s possible to reduce the production of zinc with recycling it.  However, the recycling of metals can sometimes be too expensive for small industries or privates companies. So, there are other ways than the installation of water decontamination mechanisms. Thus, bio-decontamination can be considered for these companies or industry but can also be useful to large industry in addition to their mechanisms for an exhaustive decontaminations and better water quality. Agriculture is also a source of metal pollution, so it is important to carry out hedgerows planting campaigns near fresh water since they have the function of absorbing a large part of the contaminants resulting from the leaching of flooded soils.

      Cited study: Maltby L. and Naylor C. (1990) Preliminary observations on the ecological relevance of the Gammarus ‘scope for growth’ assay: effect of zinc on reproduction, Functional Ecology. 4, 393-397.

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    • Pesticides and the power of earthwormsby Orane Becheler

      Published by Charlotte Recapet the May 10, 2019 on 6:04 PM

      We know that our current high use of some pesticides is harmful for the environment. For example, the controversy begun several years ago (National Geographic News, 2013 and Actu Environnement, 2018), about the disappearance of bees and the use of pesticides. Many of us have heard about this. In this context, assessing a priori the impacts of pesticides on environment can be helpful. This is why, five UK scientists have developed a model to anticipate the impacts of pesticides on the physiology of one species of earthworm, Eisenia fetida (A.S.A. Johnston and al., 2014).

      Why is it important?

                    The impact of pesticides on the growth and the reproduction of earthworms can lead to a huge decrease of their density and maybe to their disappearance. However, these organisms are very important for the soil quality. They provide good aeration and mixing of soil (call bioturbation) making it easier to absorb and keep water. Moreover, they greatly contribute to the degradation of organic matter making it accessible to other organisms. Indeed, a study of Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA, 2010) shows that, in a month, 1.5kg of earthworms (approximately 7,500 worms) can consume 30 days’ worth of a two-person household. In this way, plants growth better on a soil with earthworms than one without. This can be a great axis of reflexion about our way to produce vegetables. So, simulated impact of a pesticides on an area before destroy its ecosystem is a really good thing. Furthermore, we can see the importance of earthworms through their utilisation to evaluate the biodiversity in a participatory protocol (OPVT).

      In the video below, we can see the mix of soil by the earthworm’ displacements. Earthworms played a significant role in bioturbation.

      How did they do it?

                    These five UK scientists built complex model, call an energy-budget driven ABM. It consists of an interlocking of two model types: a huge one, an ABM (Agent Based Model), which contain many simple energy budget models. The first one allows to model how the population will progress, in other words the population’s dynamic. The second type allows to model life cycle processes for each earthworm from specified local conditions. Maybe the following picture can help you to understand.

      What did they found?

                    The main results are a decrease of growth and reproduction for the use of two pesticides.

      Modelling dose-response curves of two pesticides on the growth and the reproduction of Eisenia fetida. Adapted from the article.

                   Pesticides tested in this study are copper oxychloride and chlorpyrifos. The first one is widely used as fungicide and repellent, is not biodegradable and is “toxic to mammals and most biodiversity” (IUPAC, 2018). The second one is a current insecticide, “moderately persistent in soil systems, […] is highly toxic to mammals, […] birds, fish[es], aquatic invertebrates and honey bees” and “is classified as a reproduction toxicant, an acetyl cholinesterase inhibitor and a neurotoxicant” (IUPAC, 2018). So, the use of these pesticides can have large consequences not only on earthworms’ populations and so modelling consequences on others species is great.

                    Another study, presented by the Institut National de la Recherche Agronomique (INRA, 2014), shows also a decrease of earthworm populations when the quantity of used pesticides increases and vice versa (Pelosi C. et al., 2013).

      They have input local conditions of experimental data from literature. Their outputs fit great with the literature’s results, for non-toxic environments and for toxic ones, both individual life cycle processes and population dynamics.

      What is good and what is not?

                    Their model seems extremely complete because they incorporate varying food availability, use three steps of life with different parameters, for the adult stage they consider each step of processes under different feeding conditions and they consider interactions between individuals.

      In the ABM, they use a model landscape of 0.01 m2 patches of soil. It’s 10 cm2. I find this very small for a model which would simulate what it’s happening in the field. Moreover, further work is required to apply this approach to others species, maybe more ecologically relevant, and to implement the “heterogeneous distribution of chemicals in the soil and their degradation with time”. But this model can be useful to help to extrapolate data from laboratory to field or from species to species.

      Cited study: A.S.A. Johnston, M.E. Hodson, P. Thorbek and al. (2014) An energy budget agent-based model of earthworm populations and its application to study the effects of pesticides. Ecological Modelling 280, 5-17.

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    • High throughput screening methods to assess pollutants effects: A relevant technique?by Alexandre Bijaye and Melody Fernandez

      Published by Charlotte Recapet the March 12, 2019 on 6:43 PM

      The purpose of the paper written by Miller et al. in 2016 is to assess the effectiveness of HTS (High Throughput Screening) techniques to predict the effects of metal nanoparticles on a population of Isochrysis Galbana, a common species of phytoplankton. 

      High Throughout Screening is one of the newest techniques used in toxicology and which is planned to be implemented in biological and chemical sciences in the near future. Their technology is based on the analyzes of chemical compounds to be conducted in a short time. The affinity of biological structures which is related to the toxicity to be defined. 

      In this article, we’ll focus on nanoparticles: Engineered nanoparticles (ENPs) are actually an emerging form of metal contamination. These particles are widely used in biochemistry, engineering,… Four elements are studied in this paper: Ag, ZnO, CeO2 and CuO. The studied concentrations of each compound chosen were known to affect phytoplankton populations.

      Silver nanoparticules (T. Theivasanthi/Wikimedia)

      The results showing a decline of the photosynthetic activity (PSII) are compared to the HTS tests results. DEBtox models are energycally and toxycodynamically balanced modelling techniques (DEBtox and TD) and are here used to evaluate the impact of ENPs.

      First, the decline in photosynthetic activity is a good predictor. Phytoplankton are vulnerable to pollution, particularly because of their aptitude to accumulate contaminants. As a result, such a bioaccumulation can impact food webs integrity.

      Isochrysis Galbana populations were cultured at 20°C in sterile seawater (at 34 per thousand of salinity). In these conditions, HTS techniques measured cellular lesions responding to a toxic agent, permitting here to measure the potential impacts of ENPs on organisms. 

      Four HTS tests were undertaken (based on the mitochondrial membrane potential, ROS occurence, (3) cellular efflux pump action and cell membranes permeability). These tests are based on fluorescence and cell health. The impact of metallic nanoparticles was also measured. However, the results obtained were not consistent enough to highlight responses to ENP exposure:

      Non-HTS tests were performed by the measurement of the impact on photosynthetic efficiency. The metal concentrations were measured using the graphite furnace atomic absorption.

      Fluorescence kinetics of chlorophyll was also measured with an amplitude modulated pulsed fluorometer. Then the maximum fluorescence yield was computed using WinControl Software. This  the maximum fluorescence variation is assumed to be a measurement of the potential quantum yield of the PSII.

      A clear decrease in the performance of the PSII was observed for all the ENP’s:

      1. A greater decrease was observed for ZnO
      2. Also, a notable decrease was measured for CuO, at low concentrations
      3. Finally, the presence CeO and Ag decreased the performances as well even though the decrease was the smoothest.

      According to the authors, these results linked with the different dissolution rates that are specific to each compound. In this direction, Zn has a high dissolution rate, CuO and Ag dissolve very slowly and CeO has an undetectable dissolution rate. 

      As a conclusion by the authors, HTS methods can not be used to measure the impacts of metal particles because of their poor predictive power. So far, traditional ecotoxicological methods must be used.

      With such results in mind, we also agree on this statement: the four tests led by the authors all brought different conclusions. As HTS methods rely on the affinity of biological structures which is often related to toxicity to be defined, the presence of cellular compensatory mechanisms could have masked cellular responses to ENPs expositions.

      In conclusion, although HTS methods offer promising opportunities in the biological sciences (such as ecotoxicology), there are need for further investigation in this area before these techniques can be commonly adopted and used.

      Cited study: Miller, Robert J., et al. (2016) Photosynthetic efficiency predicts toxic effects of metal nanomaterials in phytoplankton, Aquatic toxicology 183, 85-93.

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    • Time and concentration dependency in the potentially affected fraction of species: The case of hydrogen peroxide treatment of ballast waterby Marie-Adèle Dutertre and Maud Hautier

      Published by Charlotte Recapet the December 10, 2018 on 4:32 PM

      Globalization and international trade made natural gates easier to cross for species. As a consequence, few species were able to travel long distance and settled in new habitats where they become invasive species.

      More than 80% of industrialized goods in the world are transported by the oceans in container ships. In many cases, container ships is discharged in the destination port and go back empty. Whereas, the structure of this kind of ship does not allow them to travel empty and with stability. This is for a problem of stability  that ballast exists. Since the 19th century, ballast with rocks was substitute with water. Before ships leave the port , water is loading in tank and at the destination port tanks are discharged.

      Ballast water transport contribute to invasive species spreading. In order to fight against exotics species, waters ballast are treated with Hydrogen Peroxide (H2O2). But there is  a question : how to be sure that ballast water is effective and is not toxic for the marine environment ? In order to evaluate the environmental impact of the treatment, a study has been conducted. Three taxa has been chosen, among them, two crustacean, two algae and one rotifera : C. volutator, A. salina, E. costatum, D. teriolecta,  B. plicatilis. The authors of the study consider three dimensions : Hydrogen Peroxyde concentration, the effect of the Peroxide Hydrogen on organism and Hydrogen Peroxide exposure time. In the experiment, they made the tree dimensions varied and they considered as the final aim, the mortality, the immobility and the inactivation of the organism. The results are used in a mechanistic model which is based on the description of  Dynamic Energy Budget theory. The DEB theory consists of a simple set of rules that specifies how organisms acquire energy and building blocks from their environment to fuel their life cycle. It is used to rely the observed effects and the hydrogen peroxide concentration in the experiments. The DEB-tox model allows to determine ECx — Effect Concentration — : the concentration which induces a response of x% between the baseline and maximum after a specified exposure time ; and the HCx — Hazardous Concentration — : the concentration which is dangerous for x% of the population. Thanks to this values, it is possible to determine the PAF — Potentially Affected Population— with means the part of an ecosystem potentially affected by a drug concentration. The results show an interspecific response variability with means different interspecific H2O2 sensibility. Sensibility is a combination between time exposure and the concentration. The conclusion of the study is that the hydrogen peroxide is effective for treating ballast water.

      Concentrations, effects and time exposure were studied there. The choice of the five species is a wise choice as a result of the representativeness of a wide selection of sensibility which allows to extrapolate this results to other species and then estimate the effect of hydrogen peroxide treatment on other species present in water ballast. Whereas the aim of the study was to assess environmental risks of hydrogen peroxide treatment, and the obtained results here cannot be used to conclude regarding as the environmental risks.

      To assess more precisely the risk, it is important to consider the hydrogen peroxide degradation and its potential impact on marine ecosystem. The H2O2 is oxygenated water which would rapidly be decomposed : 2H2O2 => 2H2O + O2. In this case, the hydrogen peroxide would not impact the environment.

      Furthermore, sub-lethal effects are sufficient to reduce the viability of the organisms and for that, lower concentration of H2O2 and lower time exposure are sufficient. The purpose is to neutralize exotic species with lower environmental and economic costs. Moreover, in order to reduce again the hydrogen peroxide used quantity, other studies show the efficiency of using UV, Ozone, and ultrasound for neutralizing species. The hydrogen peroxide treatment can also be used with alkaline water which allows to obtain the same result with lower concentration and time exposure.

      An other option is to establish regulated areas for discharging and to filter and to purify ballast water before discharging in the environment.

      Cited study: Smit, M. G., Ebbens, E., Jak, R.G., and Huijbregtst, M.A. (2008). Time and concentration dependency in the potentially affected fraction of species: The case of hydrogen peroxide treatment of ballast water. Environmental Toxicology and Chemistry 27(3), 746-753.

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