Publications by authors named "Marco Fusi"

29 Publications

  • Page 1 of 1

Compartmentalization of bacterial and fungal microbiomes in the gut of adult honeybees.

NPJ Biofilms Microbiomes 2021 May 7;7(1):42. Epub 2021 May 7.

Biological and Environmental Sciences and Engineering Division (BESE), Red Sea Research Center (RSRC), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia.

The core gut microbiome of adult honeybee comprises a set of recurring bacterial phylotypes, accompanied by lineage-specific, variable, and less abundant environmental bacterial phylotypes. Several mutual interactions and functional services to the host, including the support provided for growth, hormonal signaling, and behavior, are attributed to the core and lineage-specific taxa. By contrast, the diversity and distribution of the minor environmental phylotypes and fungal members in the gut remain overlooked. In the present study, we hypothesized that the microbial components of forager honeybees (i.e., core bacteria, minor environmental phylotypes, and fungal members) are compartmentalized along the gut portions. The diversity and distribution of such three microbial components were investigated in the context of the physico-chemical conditions of different gut compartments. We observed that changes in the distribution and abundance of microbial components in the gut are consistently compartment-specific for all the three microbial components, indicating that the ecological and physiological interactions among the host and microbiome vary with changing physico-chemical and metabolic conditions of the gut.
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http://dx.doi.org/10.1038/s41522-021-00212-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8105395PMC
May 2021

Introducing the Mangrove Microbiome Initiative: Identifying Microbial Research Priorities and Approaches To Better Understand, Protect, and Rehabilitate Mangrove Ecosystems.

mSystems 2020 Oct 20;5(5). Epub 2020 Oct 20.

Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA

Mangrove ecosystems provide important ecological benefits and ecosystem services, including carbon storage and coastline stabilization, but they also suffer great anthropogenic pressures. Microorganisms associated with mangrove sediments and the rhizosphere play key roles in this ecosystem and make essential contributions to its productivity and carbon budget. Understanding this nexus and moving from descriptive studies of microbial taxonomy to hypothesis-driven field and lab studies will facilitate a mechanistic understanding of mangrove ecosystem interaction webs and open opportunities for microorganism-mediated approaches to mangrove protection and rehabilitation. Such an effort calls for a multidisciplinary and collaborative approach, involving chemists, ecologists, evolutionary biologists, microbiologists, oceanographers, plant scientists, conservation biologists, and stakeholders, and it requires standardized methods to support reproducible experiments. Here, we outline the Mangrove Microbiome Initiative, which is focused around three urgent priorities and three approaches for advancing mangrove microbiome research.
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http://dx.doi.org/10.1128/mSystems.00658-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7577295PMC
October 2020

Hydrolytic Profile of the Culturable Gut Bacterial Community Associated With .

Front Microbiol 2020 12;11:1965. Epub 2020 Aug 12.

Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente (DeFENS), Università degli Studi di Milano, Milan, Italy.

Larvae of the black soldier fly (BSF) (L.) convert organic waste into high valuable insect biomass that can be used as alternative protein source for animal nutrition or as feedstock for biodiesel production. Since insect biology and physiology are influenced by the gut microbiome, knowledge about the functional role of BSF-associated microorganisms could be exploited to enhance the insect performance and growth. Although an increasing number of culture-independent studies are unveiling the microbiota structure and composition of the BSF gut microbiota, a knowledge gap remains on the experimental validation of the contribution of the microorganisms to the insect growth and development. We aimed at assessing if BSF gut-associated bacteria potentially involved in the breakdown of diet components are able to improve host nutrition. A total of 193 bacterial strains were obtained from guts of BSF larvae reared on a nutritious diet using selective and enrichment media. Most of the bacterial isolates are typically found in the insect gut, with major representatives belonging to the Gammaproteobacteria and Bacilli classes. The hydrolytic profile of the bacterial collection was assessed on compounds typically present in the diet. Finally, we tested the hypothesis that the addition to a nutritionally poor diet of the two isolates HI169 and HI121, selected for their complementary metabolic activities, could enhance BSF growth. HI169 positively influenced the larval final weight and growth rate when compared to the control. Conversely, the addition of HI121 to the nutritionally poor diet did not result in a growth enhancement in terms of larval weight and pupal weight and length in comparison to the control, whereas the combination of the two strains positively affected the larval final weight and the pupal weight and length. In conclusion, we isolated BSF-associated bacterial strains with potential positive properties for the host nutrition and we showed that selected isolates may enhance BSF growth, suggesting the importance to evaluate the effect of the bacterial administration on the insect performance.
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http://dx.doi.org/10.3389/fmicb.2020.01965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7434986PMC
August 2020

Sea urchin chronicles. The effect of oxygen super-saturation and marine polluted sediments from Bagnoli-Coroglio Bay on different life stages of the sea urchin Paracentrotus lividus.

Mar Environ Res 2020 Jul 27;159:104967. Epub 2020 Mar 27.

Department of Integrative Marine Ecology, Ischia Marine Centre, Stazione Zoologica Anton Dohrn, Punta San Pietro, 80077, Ischia, (Naples), Italy. Electronic address:

In marinas and harbours, the accumulation of pollutants in sediments, combined with poor exchange of water with the open sea, poses a major environmental threat. The presence of photosynthetic organisms and the related oxygen production, however, may alleviate the negative effects of environmental contamination on heterotrophic organisms, enhancing their physiological defences. Furthermore, possible transgenerational buffer effects may increase the ability of natural populations to face environmental stress. Here we tested the occurrence of transgenerational effects on larvae of the sea urchin Paracentrotus lividus, whose parents were exposed, during the gametogenesis, to contaminated sediments subject to two temporal patterns of water re-suspension events and normal- (90%) vs. super-saturated (200%) levels of O. The study site was Bagnoli-Coroglio (Gulf of Naples, southern Tyrrhenian Sea), a historically polluted brownfield and Site of National Interest for which environmental restoration options are currently under exploration. Larvae from different adult populations were significantly, although not linearly, affected by the interaction of all factors to which parents were exposed, at both 24h and 48h post fertilization. Specifically, the exposure of larvae to elutriates from contaminated sediments determined a developmental delay, a reduction in size and an increased percentage of abnormalities in all larval populations independently of their parental exposure. On the contrary, larvae from parents exposed to contaminated sediments, when reared in clean filtered sea water, succeeded in developing until the echinopluteus stage after 48h, with size and abundance comparable to those of larvae from control parents. Pre-exposure of parents to contaminated sediments did not successfully buffer the negative effects of elutriates on their offspring, and no positive effects of 'super-saturated' levels of O in response to contaminants were observed, suggesting that the Bagnoli-Coroglio area is currently not suitable for the re-stocking or re-introduction of this species.
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http://dx.doi.org/10.1016/j.marenvres.2020.104967DOI Listing
July 2020

A horizon scan of priorities for coastal marine microbiome research.

Nat Ecol Evol 2019 11 21;3(11):1509-1520. Epub 2019 Oct 21.

Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, Victoria, Australia.

Research into the microbiomes of natural environments is changing the way ecologists and evolutionary biologists view the importance of microorganisms in ecosystem function. This is particularly relevant in ocean environments, where microorganisms constitute the majority of biomass and control most of the major biogeochemical cycles, including those that regulate Earth's climate. Coastal marine environments provide goods and services that are imperative to human survival and well-being (for example, fisheries and water purification), and emerging evidence indicates that these ecosystem services often depend on complex relationships between communities of microorganisms (the 'microbiome') and the environment or their hosts - termed the 'holobiont'. Understanding of coastal ecosystem function must therefore be framed under the holobiont concept, whereby macroorganisms and their associated microbiomes are considered as a synergistic ecological unit. Here, we evaluate the current state of knowledge on coastal marine microbiome research and identify key questions within this growing research area. Although the list of questions is broad and ambitious, progress in the field is increasing exponentially, and the emergence of large, international collaborative networks and well-executed manipulative experiments are rapidly advancing the field of coastal marine microbiome research.
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http://dx.doi.org/10.1038/s41559-019-0999-7DOI Listing
November 2019

Oxygen supersaturation protects coastal marine fauna from ocean warming.

Sci Adv 2019 09 4;5(9):eaax1814. Epub 2019 Sep 4.

King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC), Thuwal 23955-6900, Saudi Arabia.

Ocean warming affects the life history and fitness of marine organisms by, among others, increasing animal metabolism and reducing oxygen availability. In coastal habitats, animals live in close association with photosynthetic organisms whose oxygen supply supports metabolic demands and may compensate for acute warming. Using a unique high-frequency monitoring dataset, we show that oxygen supersaturation resulting from photosynthesis closely parallels sea temperature rise during diel cycles in Red Sea coastal habitats. We experimentally demonstrate that oxygen supersaturation extends the survival to more extreme temperatures of six species from four phyla. We clarify the mechanistic basis of the extended thermal tolerance by showing that hyperoxia fulfills the increased metabolic demand at high temperatures. By modeling 1 year of water temperatures and oxygen concentrations, we predict that oxygen supersaturation from photosynthetic activity invariably fuels peak animal metabolic demand, representing an underestimated factor of resistance and resilience to ocean warming in ectotherms.
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http://dx.doi.org/10.1126/sciadv.aax1814DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6726443PMC
September 2019

Developmental stages and gut microenvironments influence gut microbiota dynamics in the invasive beetle Popillia japonica Newman (Coleoptera: Scarabaeidae).

Environ Microbiol 2019 11 21;21(11):4343-4359. Epub 2019 Oct 21.

Dipartimento di Scienze Agrarie e Ambientali (DiSAA), Università degli Studi di Milano, 20133, Milan, Italy.

Popillia japonica Newman (Coleoptera: Scarabaeidae) is a highly polyphagous invasive beetle originating from Japan. This insect is highly resilient and able to rapidly adapt to new vegetation. Insect-associated microorganisms can play important roles in insect physiology, helping their hosts to adapt to changing conditions and potentially contributing to an insect's invasive potential. Such symbiotic bacteria can be part of a core microbiota that is stably transmitted throughout the host's life cycle or selectively recruited from the environment at each developmental stage. The aim of this study was to investigate the origin, stability and turnover of the bacterial communities associated with an invasive population of P. japonica from Italy. Our results demonstrate that soil microbes represent an important source of gut bacteria for P. japonica larvae, but as the insect develops, its gut microbiota richness and diversity decreased substantially, paralleled by changes in community composition. Notably, only 16.75% of the soil bacteria present in larvae are maintained until the adult stage. We further identified the micro-environments of different gut sections as an important factor shaping microbiota composition in this species, likely due to differences in pH, oxygen availability and redox potential. In addition, P. japonica also harboured a stable bacterial community across all developmental stages, consisting of taxa well known for the degradation of plant material, namely the families Ruminococcacae, Christensenellaceae and Lachnospiraceae. Interestingly, the family Christensenallaceae had so far been observed exclusively in humans. However, the Christensenellaceae operational taxonomic units found in P. japonica belong to different taxonomic clades within this family.
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http://dx.doi.org/10.1111/1462-2920.14797DOI Listing
November 2019

Phenomics and Genomics Reveal Adaptation of Strain 21D to Its Origin of Isolation, the Seawater-Brine Interface of the Mediterranean Sea Deep Hypersaline Anoxic Basin Discovery.

Front Microbiol 2019 12;10:1304. Epub 2019 Jun 12.

Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente (DeFENS), Università degli Studi di Milano, Milan, Italy.

The adaptation of sporeformers to extreme environmental conditions is frequently questioned due to their capacity to produce highly resistant endospores that are considered as resting contaminants, not representing populations adapted to the system. In this work, in order to gain a better understanding of bacterial adaptation to extreme habitats, we investigated the phenotypic and genomic characteristics of the halophile sp. 21D isolated from the seawater-brine interface (SBI) of the MgCl-saturated deep hypersaline anoxic basin Discovery located in the Eastern Mediterranean Sea. Vegetative cells of strain 21D showed the ability to grow in the presence of high concentrations of MgCl such as 14.28% corresponding to 1.5 M. Biolog phenotype MicroArray (PM) was adopted to investigate the strain phenotype, with reference to carbon energy utilization and osmotic tolerance. The strain was able to metabolize only 8.4% of 190 carbon sources provided in the PM1 and PM2 plates, mainly carbohydrates, in accordance with the low availability of nutrients in its habitat of origin. By using DNA-DNA hybridization the analysis of strain 21D genome, assembled in one circular contig, revealed that the strain belongs to the species . The genome presented compatible solute-based osmoadaptation traits, including genes encoding for osmotically activated glycine-betaine/carnitine/choline ABC transporters, as well as ectoine synthase enzymes. Osmoadaptation of the strain was then confirmed with phenotypic assays by using the osmolyte PM9 Biolog plate and growth experiments. Furthermore, the neutral isoelectric point of the reconstructed proteome suggested that the strain osmoadaptation was mainly mediated by compatible solutes. The presence of genes involved in iron acquisition and metabolism indicated that osmoadaptation was tailored to the iron-depleted saline waters of the Discovery SBI. Overall, both phenomics and genomics highlighted the potential capability of 21D vegetative cells to adapt to the environmental conditions in Discovery SBI.
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http://dx.doi.org/10.3389/fmicb.2019.01304DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6581673PMC
June 2019

Bacterial endophytes of mangrove propagules elicit early establishment of the natural host and promote growth of cereal crops under salt stress.

Microbiol Res 2019 Jun - Aug;223-225:33-43. Epub 2019 Mar 26.

Institute of Applied Microbiology, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 26-32, 35392, Giessen, Germany; Department of Biological and Environmental Sciences and Technologies, University of Salento, via Prov.le Lecce-Monteroni, 73100, Lecce, Italy. Electronic address:

Mangroves, dominating tropical intertidal zones and estuaries, are among the most salt tolerant plants, and propagate through reproductive units called propagules. Similarly to plant seeds, propagules may harbor beneficial bacteria. Our hypothesis was that mangroves, being able to grow into seawater, should harbor bacteria able to interact with the host and to exert positive effects under salt stress, which could be exploited to improve crop production. Therefore, we isolated bacterial endophytes from mangrove propagules with the aim to test whether these bacteria have a beneficial potential on their natural host and on different crops such as barley and rice, cultivated under salt stress. The 172 bacterial isolates obtained were screened for plant growth promotion (PGP) activities in vitro, and the 12 most promising isolates were tested on barley under non-axenic conditions and salt stress. Gordonia terrae KMP456-M40 was the best performing isolate, increasing ear weight by 65%. Based on the in vivo PGP activity and the root colonization ability, investigated by fluorescence in situ hybridization and confocal microscopy, three strains were additionally tested on mangrove propagule germination and on rice growth. The most effective strain was again G. terrae KMP456-M40, which enhanced the root length of mangrove seedlings and the biomass of salt-stressed rice under axenic conditions up to 65% and 62%, respectively. We demonstrated that propagules, the reproductive units of mangroves, host beneficial bacteria that enhance the potential of mangrove seedlings establishment and confer salt tolerance to cereal crops.
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http://dx.doi.org/10.1016/j.micres.2019.03.008DOI Listing
July 2019

The role of fungi in heterogeneous sediment microbial networks.

Sci Rep 2019 05 17;9(1):7537. Epub 2019 May 17.

King Abdullah University of Science and Technology, Red Sea Research Center, Thuwal, 23955-6900, Saudi Arabia.

While prokaryote community diversity and function have been extensively studied in soils and sediments, the functional role of fungi, despite their huge diversity, is widely unexplored. Several studies have, nonetheless, revealed the importance of fungi in provisioning services to prokaryote communities. Here, we hypothesise that the fungal community plays a key role in coordinating entire microbial communities by controlling the structure of functional networks in sediment. We selected a sediment environment with high niche diversity due to prevalent macrofaunal bioturbation, namely intertidal mangrove sediment, and explored the assembly of bacteria, archaea and fungi in different sediment niches, which we characterised by biogeochemical analysis, around the burrow of a herbivorous crab. We detected a high level of heterogeneity in sediment biogeochemical conditions, and diverse niches harboured distinct communities of bacteria, fungi and archaea. Saprotrophic fungi were a pivotal component of microbial networks throughout and we invariably found fungi to act as keystone species in all the examined niches and possibly acting synergistically with other environmental variables to determine the overall microbial community structure. In consideration of the importance of microbial-based nutrient cycling on overall sediment ecosystem functioning, we underline that the fungal microbiome and its role in the functional interactome cannot be overlooked.
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http://dx.doi.org/10.1038/s41598-019-43980-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6525233PMC
May 2019

Consistent bacterial selection by date palm root system across heterogeneous desert oasis agroecosystems.

Sci Rep 2019 03 11;9(1):4033. Epub 2019 Mar 11.

King Abdullah University of Science and Technology (KAUST), Biological and Environmental Sciences and Engineering Division (BESE), Thuwal, 23955-6900, Saudi Arabia.

Highly productive conventional agroecosystems are spatially embedded in resource-homogeneous systems and count on generally nutrient-rich soils. On the contrary, desert oases are isolated, the soil is relatively poor, but yet productivity is similar to conventional agroecosystems. Soil dominates over plant as the main factor shaping root-associated microbiomes in conventional agroecosystems. We hypothesize that in desert oasis, the environmental discontinuity, the resource paucity and limited microbial diversity of the soil make the plant a prevailing factor. We have examined the bacterial communities in the root system of date palm (Phoenix dactylifera), the iconic keystone species of the oases, grown in heterogeneous soils across a broad geographic range (22,200 km surface area) of the Sahara Desert in Tunisia. We showed that, regardless of the edaphic conditions and geographic location, the plant invariably selects similar Gammaproteobacteria- and Alphaproteobacteria-dominated bacterial communities. The phylogeny, networking properties and predicted functionalities of the bacterial communities indicate that these two phyla are performing the ecological services of biopromotion and biofertilization. We conclude that in a desert agroecosystem, regardless of the soil microbial diversity baseline, the plant, rather than soil type, is responsible of the bacterial community assembly in its root systems, reversing the pattern observed in conventional agroecosystem.
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http://dx.doi.org/10.1038/s41598-019-40551-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412053PMC
March 2019

Fiddler crab bioturbation determines consistent changes in bacterial communities across contrasting environmental conditions.

Sci Rep 2019 03 6;9(1):3749. Epub 2019 Mar 6.

King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal, 23955-6900, Saudi Arabia.

Ecosystem functions are regulated by compositional and functional traits of bacterial communities, shaped by stochastic and deterministic processes. Biogeographical studies have revealed microbial community taxonomy in a given ecosystem to change alongside varying environmental characteristics. Considering that stable functional traits are essential for community stability, we hypothesize that contrasting environmental conditions affect microbial taxonomy rather than function in a model system, testing this in three geographically distinct mangrove forests subjected to intense animal bioturbation (a shared deterministic force). Using a metabarcoding approach combined with sediment microprofiling and biochemistry, we examined vertical and radial sediment profiles of burrows belonging to the pantropical fiddler crab (subfamily Gelasiminae) in three contrasting mangrove environments across a broad latitudinal range (total samples = 432). Each mangrove was environmentally distinct, reflected in taxonomically different bacterial communities, but communities consistently displayed the same spatial stratification (a halo effect) around the burrow which invariably determined the retention of similar inferred functional community traits independent of the local environment.
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http://dx.doi.org/10.1038/s41598-019-40315-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6403291PMC
March 2019

Rhizosheath microbial community assembly of sympatric desert speargrasses is independent of the plant host.

Microbiome 2018 12 4;6(1):215. Epub 2018 Dec 4.

King Abdullah University of Science and Technology (KAUST), Biological and Environmental Sciences and Engineering Division (BESE), Thuwal, 23955-6900, Saudi Arabia.

Background: The rhizosheath-root system is an adaptive trait of sandy-desert speargrasses in response to unfavourable moisture and nutritional conditions. Under the deserts' polyextreme conditions, plants interact with edaphic microorganisms that positively affect their fitness and resistance. However, the trophic simplicity and environmental harshness of desert ecosystems have previously been shown to strongly influence soil microbial community assembly. We hypothesize that sand-driven ecological filtering constrains the microbial recruitment processes in the speargrass rhizosheath-root niche, prevailing over the plant-induced selection.

Methods: Bacterial and fungal communities from the rhizosheath-root compartments (endosphere root tissues, rhizosheath and rhizosphere) of three Namib Desert speargrass species (Stipagrostis sabulicola, S. seelyae and Cladoraphis spinosa) along with bulk sand have been studied to test our hypothesis. To minimize the variability determined by edaphic and climatic factors, plants living in a single dune were studied. We assessed the role of plant species vs the sandy substrate on the recruitment and selection, phylogenetic diversity and co-occurrence microbial networks of the rhizosheath-root system microbial communities.

Results: Microorganisms associated with the speargrass rhizosheath-root system were recruited from the surrounding bulk sand population and were significantly enriched in the rhizosheath compartments (10 and 10 of bacterial 16S rRNA and fungal ITS copies per gram of sand to up to 10 and 10 copies per gram, respectively). Furthermore, each rhizosheath-root system compartment hosted a specific microbial community demonstrating strong niche-partitioning. The rhizosheath-root systems of the three speargrass species studied were dominated by desert-adapted Actinobacteria and Alphaproteobacteria (e.g. Lechevalieria, Streptomyces and Microvirga) as well as saprophytic Ascomycota fungi (e.g. Curvularia, Aspergillus and Thielavia). Our results clearly showed a random phylogenetic turnover of rhizosheath-root system associated microbial communities, independent of the plant species, where stochastic factors drive neutral assembly. Co-occurrence network analyses also indicated that the bacterial and fungal community members of the rhizosheath-root systems established a higher number of interactions than those in the barren bulk sand, suggesting that the former are more stable and functional than the latter.

Conclusion: Our study demonstrates that the rhizosheath-root system microbial communities of desert dune speargrasses are stochastically assembled and host-independent. This finding supports the concept that the selection determined by the desert sand prevails over that imposed by the genotype of the different plant species.
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http://dx.doi.org/10.1186/s40168-018-0597-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6280439PMC
December 2018

Interference competition as a key determinant for spatial distribution of mangrove crabs.

BMC Ecol 2018 02 15;18(1). Epub 2018 Feb 15.

Department of Biology, University of Florence, via Madonna del Piano 6, 50019, Sesto Fiorentino, Italy.

Background: The spatial distribution of mangrove crabs has been commonly associated with tree zonation and abiotic factors such as ground temperature and soil granulometry. Conversely, no studies were designed to investigate the role of competition for resources and predation in shaping crab distribution in mangroves, despite these biotic factors are recognised as key determinants for spatial patterns observed in the communities colonising rocky and sandy intertidal habitats.We studied floral and faunal assemblages in two zones of a Sri Lankan mangrove, a man-made upper intertidal level and a natural eulittoral, mid-shore one. Leaf choice experiments were designed to study both feeding rate and intra and inter-specific interactions for food of sesarmid crabs in the two habitats in order to better understand crab spatial distribution.

Results: The two intertidal belts differed in terms of floral composition and crab species abundance. The eulittoral zone was strongly dominated by Neosarmatium smithi, while within the elevated littoral fringe four sesarmids (N. smithi, N. asiaticum, N. malabaricum and Muradium tetragonum) were more evenly distributed. At both levels, all sesarmids showed to collect significantly more Bruguiera spp. and Rhizophora apiculata leaves than Excoecaria agallocha ones. There was no temporal segregation in feeding activity among the four species, resulting in a high interference competition for leaves. Regardless of the habitat, N. smithi was always successful in winning inter-specific fights.

Conclusions: Our results showed that the elevated littoral fringe was more crowded with crabs, but was less favourable in terms of food availability and environmental conditions. The dominance of N. smithi in gathering mangrove leaves suggests that this species may segregate the other sesarmids into less favourable habitats. The present data strongly suggest for the first time that interference competition for food can contribute to shape mangrove crab spatial distribution.
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http://dx.doi.org/10.1186/s12898-018-0164-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5815208PMC
February 2018

The stage of soil development modulates rhizosphere effect along a High Arctic desert chronosequence.

ISME J 2018 05 15;12(5):1188-1198. Epub 2018 Jan 15.

Department of Food, Environmental and Nutritional Sciences, University of Milan, Milan, 20133, Italy.

In mature soils, plant species and soil type determine the selection of root microbiota. Which of these two factors drives rhizosphere selection in barren substrates of developing desert soils has, however, not yet been established. Chronosequences of glacier forelands provide ideal natural environments to identify primary rhizosphere selection factors along the changing edaphic conditions of a developing soil. Here, we analyze changes in bacterial diversity in bulk soils and rhizospheres of a pioneer plant across a High Arctic glacier chronosequence. We show that the developmental stage of soil strongly modulates rhizosphere community assembly, even though plant-induced selection buffers the effect of changing edaphic factors. Bulk and rhizosphere soils host distinct bacterial communities that differentially vary along the chronosequence. Cation exchange capacity, exchangeable potassium, and metabolite concentration in the soil account for the rhizosphere bacterial diversity. Although the soil fraction (bulk soil and rhizosphere) explains up to 17.2% of the variation in bacterial microbiota, the soil developmental stage explains up to 47.7% of this variation. In addition, the operational taxonomic unit (OTU) co-occurrence network of the rhizosphere, whose complexity increases along the chronosequence, is loosely structured in barren compared with mature soils, corroborating our hypothesis that soil development tunes the rhizosphere effect.
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http://dx.doi.org/10.1038/s41396-017-0026-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931989PMC
May 2018

Grapevine rootstocks shape underground bacterial microbiome and networking but not potential functionality.

Microbiome 2018 01 3;6(1). Epub 2018 Jan 3.

King Abdullah University of Science and Technology (KAUST), Biological and Environmental Sciences and Engineering Division (BESE), Thuwal, 23955-6900, Saudi Arabia.

Background: The plant compartments of Vitis vinifera, including the rhizosphere, rhizoplane, root endosphere, phyllosphere and carposphere, provide unique niches that drive specific bacterial microbiome associations. The majority of phyllosphere endophytes originate from the soil and migrate up to the aerial compartments through the root endosphere. Thus, the soil and root endosphere partially define the aerial endosphere in the leaves and berries, contributing to the terroir of the fruit. However, V. vinifera cultivars are invariably grafted onto the rootstocks of other Vitis species and hybrids. It has been hypothesized that the plant species determines the microbiome of the root endosphere and, as a consequence, the aerial endosphere. In this work, we test the first part of this hypothesis. We investigate whether different rootstocks influence the bacteria selected from the surrounding soil, affecting the bacterial diversity and potential functionality of the rhizosphere and root endosphere.

Methods: Bacterial microbiomes from both the root tissues and the rhizosphere of Barbera cultivars, both ungrafted and grafted on four different rootstocks, cultivated in the same soil from the same vineyard, were characterized by 16S rRNA high-throughput sequencing. To assess the influence of the root genotype on the bacterial communities' recruitment in the root system, (i) the phylogenetic diversity coupled with the predicted functional profiles and (ii) the co-occurrence bacterial networks were determined. Cultivation-dependent approaches were used to reveal the plant-growth promoting (PGP) potential associated with the grafted and ungrafted root systems.

Results: Richness, diversity and bacterial community networking in the root compartments were significantly influenced by the rootstocks. Complementary to a shared bacterial microbiome, different subsets of soil bacteria, including those endowed with PGP traits, were selected by the root system compartments of different rootstocks. The interaction between the root compartments and the rootstock exerted a unique selective pressure that enhanced niche differentiation, but rootstock-specific bacterial communities were still recruited with conserved PGP traits.

Conclusion: While the rootstock significantly influences the taxonomy, structure and network properties of the bacterial community in grapevine roots, a homeostatic effect on the distribution of the predicted and potential functional PGP traits was found.
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http://dx.doi.org/10.1186/s40168-017-0391-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5751889PMC
January 2018

Measuring the role of seagrasses in regulating sediment surface elevation.

Sci Rep 2017 09 20;7(1):11917. Epub 2017 Sep 20.

School of Applied Sciences, Edinburgh Napier University, Edinburgh, UK.

Seagrass meadows provide numerous ecosystem services and their rapid global loss may reduce human welfare as well as ecological integrity. In common with the other 'blue carbon' habitats (mangroves and tidal marshes) seagrasses are thought to provide coastal defence and encourage sediment stabilisation and surface elevation. A sophisticated understanding of sediment elevation dynamics in mangroves and tidal marshes has been gained by monitoring a wide range of different sites, located in varying hydrogeomorphological conditions over long periods. In contrast, similar evidence for seagrasses is sparse; the present study is a contribution towards filling this gap. Surface elevation change pins were deployed in four locations, Scotland, Kenya, Tanzania and Saudi Arabia, in both seagrass and unvegetated control plots in the low intertidal and shallow subtidal zone. The presence of seagrass had a highly significant, positive impact on surface elevation at all sites. Combined data from the current work and the literature show an average difference of 31 mm per year in elevation rates between vegetated and unvegetated areas, which emphasizes the important contribution of seagrass in facilitating sediment surface elevation and reducing erosion. This paper presents the first multi-site study for sediment surface elevation in seagrasses in different settings and species.
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http://dx.doi.org/10.1038/s41598-017-12354-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5605501PMC
September 2017

Bacteria Associated to Plants Naturally Selected in a Historical PCB Polluted Soil Show Potential to Sustain Natural Attenuation.

Front Microbiol 2017 25;8:1385. Epub 2017 Jul 25.

Department of Food, Environmental and Nutritional Sciences, University of MilanMilan, Italy.

The exploitation of the association between plants and microorganisms is a promising approach able to boost natural attenuation processes for soil clean-up in vast polluted areas characterized by mixed chemical contamination. We aimed to explore the selection of root-associated bacterial communities driven by different plant species spontaneously established in abandoned agricultural soils within a historical polluted site in north Italy. The site is highly contaminated by chlorinated persistent organic pollutants, mainly constituted by polychlorobiphenyls (PCBs), together with heavy metals and metalloids, in variable concentrations and uneven distribution. The overall structure of the non-vegetated and root-associated soil fractions bacterial communities was described by high-throughput sequencing of the 16S rRNA gene, and a collection of 165 rhizobacterial isolates able to use biphenyl as unique carbon source was assayed for plant growth promotion (PGP) traits and bioremediation potential. The results showed that the recruitment of specific bacterial communities in the root-associated soil fractions was driven by both soil fractions and plant species, explaining 21 and 18% of the total bacterial microbiome variation, respectively. PCR-based detection in the soil metagenome of bacterial gene, encoding for the biphenyl dioxygenase α subunit, indicated that the soil in the site possesses metabolic traits linked to PCB degradation. Biphenyl-utilizing bacteria isolated from the rhizosphere of the three different plant species showed low phylogenetic diversity and well represented functional traits, in terms of PGP and bioremediation potential. On average, 72% of the strains harbored the gene and/or displayed catechol 2,3-dioxygenase activity, involved in aromatic ring cleavage. PGP traits, including 1-aminocyclopropane-1-carboxylic acid deaminase activity potentially associated to plant stress tolerance induction, were widely distributed among the isolates according to assays. PGP tested on tomato plants using eleven selected bacterial isolates, confirmed the promotion and protection potential of the rhizosphere bacteria. Different spontaneous plant species naturally selected in a historical chronically polluted site showed to determine the enrichment of peculiar bacterial communities in the soil fractions associated to the roots. All the rhizosphere communities, nevertheless, hosted bacteria with degradation/detoxification and PGP potential, putatively sustaining the natural attenuation process.
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http://dx.doi.org/10.3389/fmicb.2017.01385DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524726PMC
July 2017

Salicornia strobilacea (Synonym of Halocnemum strobilaceum) Grown under Different Tidal Regimes Selects Rhizosphere Bacteria Capable of Promoting Plant Growth.

Front Microbiol 2016 22;7:1286. Epub 2016 Aug 22.

Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, ThuwalSaudi Arabia; Department of Food, Environmental and Nutritional Sciences, University of Milan, MilanItaly.

Halophytes classified under the common name of salicornia colonize salty and coastal environments across tidal inundation gradients. To unravel the role of tide-related regimes on the structure and functionality of root associated bacteria, the rhizospheric soil of Salicornia strobilacea (synonym of Halocnemum strobilaceum) plants was studied in a tidal zone of the coastline of Southern Tunisia. Although total counts of cultivable bacteria did not change in the rhizosphere of plants grown along a tidal gradient, significant differences were observed in the diversity of both the cultivable and uncultivable bacterial communities. This observation indicates that the tidal regime is contributing to the bacterial species selection in the rhizosphere. Despite the observed diversity in the bacterial community structure, the plant growth promoting (PGP) potential of cultivable rhizospheric bacteria, assessed through in vitro and in vivo tests, was equally distributed along the tidal gradient. Root colonization tests with selected strains proved that halophyte rhizospheric bacteria (i) stably colonize S. strobilacea rhizoplane and the plant shoot suggesting that they move from the root to the shoot and (ii) are capable of improving plant growth. The versatility in the root colonization, the overall PGP traits and the in vivo plant growth promotion under saline condition suggest that such beneficial activities likely take place naturally under a range of tidal regimes.
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http://dx.doi.org/10.3389/fmicb.2016.01286DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4992691PMC
September 2016

Ecological status and sources of anthropogenic contaminants in mangroves of the Wouri River Estuary (Cameroon).

Mar Pollut Bull 2016 Aug 6;109(2):723-33. Epub 2016 Jul 6.

The Swire Institute of Marine Science and The School of Biological Sciences, The University of Hong Kong, Hong Kong; Department of Biology, University of Florence, Via Madonna del Piano 6, Sesto Fiorentino, Italy.

Mangroves are critically threatened by human activities, despite the important ecosystem functions and services they provide. Mangroves in Cameroon represent no exception to the worldwide trend of mangrove destruction, especially around Douala, on the Wouri river estuary. In two sites around Douala, we assessed the presence of sterols, PAHs, PCBs, DEHP, DDT and its metabolite p,p'-DDE and potentially toxic metals in sediment samples. As a proxy of ecological quality, we measured the diversity and abundance of macrobenthos assemblages. We detected p,p'-DDE contamination, with concentrations higher than 3μgkg(-1) in 16 out of 26 samples which were attributed to recent widespread use of DDT. The detection of sterols revealed faecal contamination. Significant sensitivity of the macrobenthos to contaminants was revealed, with possible implications on the overall mangrove vulnerability to climate change and on the provision of ecosystem services to local populations.
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http://dx.doi.org/10.1016/j.marpolbul.2016.06.104DOI Listing
August 2016

The trade-off between heat tolerance and metabolic cost drives the bimodal life strategy at the air-water interface.

Sci Rep 2016 Jan 13;6:19158. Epub 2016 Jan 13.

Department Integrative Ecophysiology, Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven, Germany.

The principle of oxygen and capacity limitation of thermal tolerance in ectotherms suggests that the long-term upper limits of an organism's thermal niche are equivalent to the upper limits of the organism's functional capacity for oxygen provision to tissues. Air-breathing ectotherms show wider thermal tolerances, since they can take advantage of the higher availability of oxygen in air than in water. Bimodal species move from aquatic to aerial media and switch between habitats in response to environmental variations such as cyclical or anomalous temperature fluctuations. Here we tested the prediction that bimodal species cope better with thermal stress than truly aquatic species using the crab Pachygrapsus marmoratus as a model species. When in water, oxygen consumption rates of P. marmoratus acutely rise during warming. Beyond a temperature threshold of 23 °C the crab's aerobic metabolism in air remains lower than in water. In parallel, the haemolymph oxygen partial pressure of submerged animals progressive decreases during warming, while it remains low but constant during emersion. Our results demonstrate the ability of a bimodal breathing ectotherm to extend its thermal tolerance during air-breathing, suggesting that there are temperature-related physiological benefits during the evolution of the bimodal life style.
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http://dx.doi.org/10.1038/srep19158DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4725839PMC
January 2016

Bacterial Diversity and Bioremediation Potential of the Highly Contaminated Marine Sediments at El-Max District (Egypt, Mediterranean Sea).

Biomed Res Int 2015 27;2015:981829. Epub 2015 Jul 27.

Genetic Engineering and Biotechnology Research Institute (GEBRI), City for Scientific Research and Technology Applications (SRTA City), New Burg El-Arab City, Universities and Research Institutes District, Alexandria 21934, Egypt.

Coastal environments worldwide are threatened by the effects of pollution, a risk particularly high in semienclosed basins like the Mediterranean Sea that is poorly studied from bioremediation potential perspective especially in the Southern coast. Here, we investigated the physical, chemical, and microbiological features of hydrocarbon and heavy metals contaminated sediments collected at El-Max bay (Egypt). Molecular and statistical approaches assessing the structure of the sediment-dwelling bacterial communities showed correlations between the composition of bacterial assemblages and the associated environmental parameters. Fifty strains were isolated on mineral media supplemented by 1% crude oil and identified as a diverse range of hydrocarbon-degrading bacteria involved in different successional stages of biodegradation. We screened the collection for biotechnological potential studying biosurfactant production, biofilm formation, and the capability to utilize different hydrocarbons. Some strains were able to grow on multiple hydrocarbons as unique carbon source and presented biosurfactant-like activities and/or capacity to form biofilm and owned genes involved in different detoxification/degradation processes. El-Max sediments represent a promising reservoir of novel bacterial strains adapted to high hydrocarbon contamination loads. The potential of the strains for exploitation for in situ intervention to combat pollution in coastal areas is discussed.
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http://dx.doi.org/10.1155/2015/981829DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4530241PMC
May 2016

Contrasting environments shape thermal physiology across the spatial range of the sandhopper Talorchestia capensis.

Oecologia 2015 Dec 1;179(4):1067-78. Epub 2015 Aug 1.

Coastal Research Group, Department of Zoology and Entomology, Rhodes University, Grahamstown, South Africa.

Integrating thermal physiology and species range extent can contribute to a better understanding of the likely effects of climate change on natural populations. Generally, broadly distributed species show variation in thermal physiology between populations. Within their distributional ranges, populations at the edges are assumed to experience more challenging environments than central populations (fundamental niche breadth hypothesis). We have investigated differences in thermal tolerance and thermal sensitivity under increasing/decreasing temperatures among geographically separated populations of the sandhopper Talorchestia capensis along the South African coasts. We tested whether the thermal tolerance and thermal sensitivity of T. capensis differ between central and marginal populations using a non-parametric constraint space analysis. We linked thermal sensitivity to environmental history by using historical climatic data to evaluate whether individual responses to temperature could be related to natural long-term fluctuations in air temperatures. Our results demonstrate that there were significant differences in the thermal response of T. capensis populations to both increasing/decreasing temperatures. Thermal sensitivity (for increasing temperatures only) was negatively related to temperature variability and positively related to temperature predictability. Two different models fitted the geographical distribution of thermal sensitivity and thermal tolerance. Our results confirm that widespread species show differences in physiology among populations by providing evidence of contrasting thermal responses in individuals subject to different environmental conditions at the limits of the species' spatial range. When considering the complex interactions between individual physiology and species ranges, it is not sufficient to consider mean environmental temperatures, or even temperature variability; the predictability of that variability may be critical.
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http://dx.doi.org/10.1007/s00442-015-3404-5DOI Listing
December 2015

Oasis desert farming selects environment-specific date palm root endophytic communities and cultivable bacteria that promote resistance to drought.

Environ Microbiol Rep 2015 Aug;7(4):668-78

Laboratoire de Microbiologie et Biomolécules Actives, Département de Biologie, Faculté des Sciences de Tunis, Campus Universitaire, Tunis, 2092, Tunisia.

Oases are desert-farming agro-ecosystems, where date palm (Phoenix dactylifera L.) plays a keystone role in offsetting the effects of drought and maintaining a suitable microclimate for agriculture. At present, abundance, diversity and plant growth promotion (PGP) of date palm root-associated bacteria remain unknown. Considering the environmental pressure determined by the water scarcity in the desert environments, we hypothesized that bacteria associated with date palm roots improve plant resistance to drought. Here, the ecology of date palm root endophytes from oases in the Tunisian Sahara was studied with emphasis on their capacity to promote growth under drought. Endophytic communities segregated along a north-south gradient in correlation with geo-climatic parameters. Screening of 120 endophytes indicated that date palm roots select for bacteria with multiple PGP traits. Bacteria rapidly cross-colonized the root tissues of different species of plants, including the original Tunisian date palm cultivar, Saudi Arabian cultivars and Arabidopsis. Selected endophytes significantly increased the biomass of date palms exposed to repeated drought stress periods during a 9-month greenhouse experiment. Overall, results indicate that date palm roots shape endophytic communities that are capable to promote plant growth under drought conditions, thereby contributing an essential ecological service to the entire oasis ecosystem.
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http://dx.doi.org/10.1111/1758-2229.12304DOI Listing
August 2015

Improved heat tolerance in air drives the recurrent evolution of air-breathing.

Proc Biol Sci 2014 May 11;281(1782):20132927. Epub 2014 Mar 11.

Section of Integrative Ecophysiology, Alfred-Wegener-Institute for Polar and Marine Research, , Am Handelshafen 12, Bremerhaven 27570, Germany, DeFENS, Department of Food, Environmental and Nutritional Sciences, University of Milan, , Via Mangiagalli 25, Milan 20133, Italy, Department of Biology, University of Florence, , Via Madonna del Piano 6, Sesto Fiorentino 50019, Italy, Environmental Systems Analysis Laboratory, Department of Industrial Engineering, University of Padua, , via Marzolo 9, Padua 35131, Italy, Department of Zoology and Entomology, Rhodes University, , PO Box 94, Grahamstown 6140, South Africa.

The transition to air-breathing by formerly aquatic species has occurred repeatedly and independently in fish, crabs and other animal phyla, but the proximate drivers of this key innovation remain a long-standing puzzle in evolutionary biology. Most studies attribute the onset of air-breathing to the repeated occurrence of aquatic hypoxia; however, this hypothesis leaves the current geographical distribution of the 300 genera of air-breathing crabs unexplained. Here, we show that their occurrence is mainly related to high environmental temperatures in the tropics. We also demonstrate in an amphibious crab that the reduced cost of oxygen supply in air extends aerobic performance to higher temperatures and thus widens the animal's thermal niche. These findings suggest that high water temperature as a driver consistently explains the numerous times air-breathing has evolved. The data also indicate a central role for oxygen- and capacity-limited thermal tolerance not only in shaping sensitivity to current climate change but also in underpinning the climate-dependent evolution of animals, in this case the evolution of air-breathing.
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http://dx.doi.org/10.1098/rspb.2013.2927DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3973256PMC
May 2014

Plant growth promotion potential is equally represented in diverse grapevine root-associated bacterial communities from different biopedoclimatic environments.

Biomed Res Int 2013 26;2013:491091. Epub 2013 Jun 26.

Department of Food, Environment, and Nutritional Sciences, University of Milan, Via Celoria 2, 20133 Milan, Italy.

Plant-associated bacteria provide important services to host plants. Environmental factors such as cultivar type and pedoclimatic conditions contribute to shape their diversity. However, whether these environmental factors may influence the plant growth promoting (PGP) potential of the root-associated bacteria is not widely understood. To address this issue, the diversity and PGP potential of the bacterial assemblage associated with the grapevine root system of different cultivars in three Mediterranean environments along a macrotransect identifying an aridity gradient were assessed by culture-dependent and independent approaches. According to 16S rRNA gene PCR-DGGE, the structure of endosphere and rhizosphere bacterial communities was highly diverse (P = 0.03) and was associated with a cultivar/latitudinal/climatic effect. Despite being diverse, the bacterial communities associated with Egyptian grapevines shared a higher similarity with the Tunisian grapevines than those cultivated in North Italy. A similar distribution, according to the cultivar/latitude/aridity gradients, was observed for the cultivable bacteria. Many isolates (23%) presented in vitro multiple stress resistance capabilities and PGP activities, the most frequent being auxin synthesis (82%), insoluble phosphate solubilisation (61%), and ammonia production (70%). The comparable numbers and types of potential PGP traits among the three different environmental settings indicate a strong functional homeostasis of beneficial bacteria associated with grape root.
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http://dx.doi.org/10.1155/2013/491091DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3708380PMC
February 2014

Biomonitoring study of an estuarine coastal ecosystem, the Sacca di Goro lagoon, using Ruditapes philippinarum (Mollusca: Bivalvia).

Environ Pollut 2013 Jun 6;177:82-9. Epub 2013 Mar 6.

Università Cattolica del Sacro Cuore, Institute of Agricultural and Environmental Chemistry, Via Emilia Parmense 84, 29100 Piacenza, Italy.

Coastal lagoons are constantly subjected to releases of chemical pollutants, and so organisms may be exposed to such toxicants. This study investigated through a multivariate approach the physiological status of bivalve Ruditapes philippinarum, farmed in Sacca di Goro lagoon. Biomarkers at different levels of biological organization (catalase, superoxide dismutase, genotoxicity, reburrowing behavior) were evaluated at three sites exposed to different environmental conditions. A seasonal trend was observed, and micronucleus frequency was significantly lowest at the relatively pristine reference site. Enzymatic activity toward oxyradicals be quite efficient since variations in responsiveness were not consistent. However, behavioral impairment was observed in reburrowing rates. Sediment concentrations showed low PAH levels and high natural levels of trace metals Cr and Ni. DistLM statistical analysis revealed a non-significant relationship between selected biomarkers and xenobiotics. Therefore other potentially toxic compounds in admixture at low doses may be involved in driving differing spatial distribution of physiological impairment.
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http://dx.doi.org/10.1016/j.envpol.2013.01.042DOI Listing
June 2013

The effect of sewage discharge on the ecosystem engineering activities of two East African fiddler crab species: consequences for mangrove ecosystem functioning.

Mar Environ Res 2011 Feb 16;71(1):53-61. Epub 2010 Oct 16.

Dipartimento di Biologia Evoluzionistica, Università degli Studi di Firenze, via Romana 17, I-50125 Firenze, Italy.

A number of studies have suggested that mangrove forests and their faunal components may be pre-adapted to the impact of organic waste discharge, making them possible natural wastewater treatment wetlands. However, the results from recent research are contradictory. Some studies have shown that negative effects, sometimes subtle and difficult to observe, can be detected on specific biotic components of forests subjected to organic pollution. Therefore, the aim of the present study was to investigate possible alterations in the ecosystem engineering activities of a fiddler crab community dominating the landward belts of Kenyan mangrove forests. The total processed sediment produced by burrowing and foraging activities in a population from a peri-urban mangrove area receiving untreated domestic sewage was compared with that from a forest not affected by urban wastewater. The results showed how the peri-urban site hosted a higher biomass of crabs, which produced a significantly lower amount of processed sediment compared with the pristine site, resulting in a lower total top sediment mixing activity of the crabs. Thus, the present study showed a link between sewage exposure and top sediment reworking by crabs, which is potentially beneficial for mangrove growth and ecosystem functioning. This represents a possible example of cryptic ecological degradation in mangal systems.
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http://dx.doi.org/10.1016/j.marenvres.2010.10.002DOI Listing
February 2011

Physiological effects of temperature and a herbicide mixture on the soft-shell clam Mya arenaria (Mollusca, Bivalvia).

Environ Toxicol Chem 2011 Jan;30(1):132-41

Università Cattolica del Sacro Cuore, Agricultural and Environmental Chemistry Institute, Piacenza, Italy.

The aim of the current study was to investigate effects of temperature and a mixture of herbicides on the physiological status of the bivalve Mya arenaria. Bivalves acclimated to two temperatures (7 and 18°C) were exposed for 28 d to 0.01 mg/L of a pesticide formulation containing dichlorophenoxyacetic acid (2,4-D), 2-(2-methyl-4-chlorophenoxy) propionic acid (mecoprop), and 3,6-dichloro-2-methoxybenzoic acid (dicamba). At days 7, 14, and 28, mortality, immune parameters (hemocyte number, phagocytic activity, and efficiency), biomarkers of oxidative stress (catalase [CAT] and superoxide dismutase [SOD] activities and malondialdehyde [MDA] content), the metabolic enzyme cytochrome C oxidase (CCO), a biomarker of pesticide exposure (acetylcholinesterase [AChE]), and the activity of an enzyme related to gametogenesis (aspartate transcarbamylase [ATCase]) were monitored in clam tissues. Gonadosomatic index (GSI), condition factor (CF), and sex were also assessed. In clams acclimated to 7°C, exposure to pesticide enhanced CCO activity and CF and decreased MDA content, hemocyte number, CAT, and SOD activities. In clams kept at 18°C, pesticide effects appeared minor compared with samples kept at 7°C. In bivalves acclimated to 18°C, CCO, SOD, and ATCase activity and MDA content were enhanced, and hemocyte number, CAT, and AchE activities and phagocytosis were suppressed. In samples exposed to pesticides, increased temperature enhanced MDA content and CCO and SOD activity and suppressed hemocyte number and CAT and AchE activity. A gradual sexual maturation was observed in both sexes through experimental time, but females had a higher sensitivity to temperature and pesticides compared to males. Increased temperature altered the ability of the sentinel species Mya arenaria to respond to pesticide exposures. Further work is needed to understand the impacts of increasing temperature on the whole St. Lawrence estuary ecosystem.
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http://dx.doi.org/10.1002/etc.359DOI Listing
January 2011