Microplastics are a major environmental challenge, being ubiquitous and persistent as to represent a new component in all marine environments. As any biogenic particle, microplastics provide surfaces ...for microbial growth and biofilm production, which largely consists of carbohydrates and proteins. Biofilms influence microbial activity and modify particle buoyancy, and therefore control the fate of microplastics at sea. In a simulated 'plastic ocean', three mesocosms containing oligotrophic seawater were amended with polystyrene microbeads and compared to three control mesocosms. The evolution of organic matter, microbial communities and nutrient concentrations was monitored over 12 days. The results indicated that microplastics increased the production of organic carbon and its aggregation into gel particulates. The observed increase of gel-like organics has implications on the marine biological pump as well as the transport of microplastics in the ocean.
The effects of the abrupt input of high quantities of dissolved inorganic nitrogen and phosphorus on prokaryotic and eukaryotic microbial plankton were investigated in an attempt to simulate the ...nutrient disturbances caused by eutrophication and climate change. Two nutrient levels were created through the addition of different quantities of dissolved nutrients in a mesocosm experiment. During the developed blooms, compositional differences were found within bacteria and microbial eukaryotes, and communities progressed towards species of faster metabolisms. Regarding the different nutrient concentrations, different microbial species were associated with each nutrient treatment and community changes spanned from the phylum to the operational taxonomic unit (OTU) level. Network analyses revealed important differences in the biotic connections developed: more competitive relationships were established in the more intense nutrient disturbance and networks of contrasting complexity were formed around species of different ecological strategies. This work highlights that sudden disturbances in water column chemistry lead to the development of entirely different microbial food webs with distinct ecological characteristics.
•Bacterial and microbial eukaryotic communities changed after addition of high quantities of dissolved inorganic N and P.•Composition changes were obvious at the phylum level; Actinobacteria, Chlorophytes, Cryptophytes differentiated treatments.•Succession of plankton populations was similar under different nutrient conditions.•Few differentiations were found in the succession of the micro-eukaryotes: Bacillariophyta, Cilliophora and Dinoflagellata.•Different nutrient quantities caused changes in the ecological connections among OTUs.•Low nutrient addition resulted in more positive relationships between same trophic groups; high addition in negative ones.
Ecotoxicity of silver nanoparticles on plankton organisms: a review Kalantzi, Ioanna; Mylona, Kyriaki; Toncelli, Claudio ...
Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology,
03/2019, Letnik:
21, Številka:
3
Journal Article
Engineered silver nanoparticles (Ag-NPs) are ubiquitous in many commercial products due to their antibacterial and antifungal properties. Due to the different properties of NPs from their homolog ...bulk materials, the inevitable leaching of nanosilver from commercial products into the aquatic environment is raising concern about possible effects on aquatic organisms. This review aims at elucidating the inherent ecotoxicity of Ag-NPs for planktonic organisms that produce and transfer energy in the food web and play a key role in nutrient recycling. The current knowledge was gathered through laboratory studies on planktonic organisms, such as bacteria and algae. However, it has already been proven for other pollutants that the ecotoxicological response is strikingly different when simulating more realistic environmental conditions, as in the microcosm and mesocosm studies. Abiotic and biotic factors strongly contribute to altering the toxicity of Ag-NPs and of their released silver ions. The dilemma of the nano or ion effects of Ag-NP toxicity is hereby debated. As a general outlook, we observe that most of the studies were carried out at concentrations much higher than would ever be expected in the environment, and over time periods much shorter which would be typical for the environment. Furthermore, most of the research was focused on freshwater ecosystems and little information exists about the marine environment. It seems that Ag-NPs are less toxic than silver ions. Moreover, the Trojan Horse effect of Ag-NPs in the presence of other pollutants is poorly investigated. This review highlights these research gaps and recommends further research on the Ag-NP ecotoxicity in aquatic environments under more realistic conditions in large-scale experiments and their recovery from chemical stress.
Graphical abstract
Introduction
Marine viruses regulate microbial population dynamics and biogeochemical cycling in the oceans. The ability of viruses to manipulate hosts’ metabolism through the expression of viral ...auxiliary metabolic genes (AMGs) was recently highlighted, having important implications in energy production and flow in various aquatic environments. Up to now, the presence and diversity of viral AMGs is studied using -omics data, and rarely using quantitative measures of viral activity alongside.
Methods
In the present study, four depth layers (5, 50, 75, and 1,000 m) with discrete hydrographic features were sampled in the Eastern Mediterranean Sea; we studied lytic viral community composition and AMG content through metagenomics, and lytic production rates through the viral reduction approach in the ultra-oligotrophic Levantine basin where knowledge regarding viral actions is rather limited.
Results and Discussion
Our results demonstrate depth-dependent patterns in viral diversity and AMG content, related to differences in temperature, nutrients availability, and host bacterial productivity and abundance. Although lytic viral production rates were similar along the water column, the virus-to-bacteria ratio was higher and the particular set of AMGs was more diverse in the bathypelagic (1,000 m) than the shallow epipelagic (5, 50, and 75 m) layers, revealing that the quantitative effect of viruses on their hosts may be the same along the water column through the intervention of different AMGs. In the resource- and energy-limited bathypelagic waters of the Eastern Mediterranean, the detected AMGs could divert hosts’ metabolism toward energy production, through a boost in gluconeogenesis, fatty-acid and glycan biosynthesis and metabolism, and sulfur relay. Near the deep-chlorophyll maximum depth, an exceptionally high percentage of AMGs related to photosynthesis was noticed. Taken together our findings suggest that the roles of viruses in the deep sea might be even more important than previously thought as they seem to orchestrate energy acquisition and microbial community dynamics, and thus, biogeochemical turnover in the oceans.
Climate change driven by human activities encompasses the increase in atmospheric CO
concentration and sea-surface temperature. Little is known regarding the synergistic effects of these phenomena on ...bacterial communities in oligotrophic marine ecosystems that are expected to be particularly vulnerable. Here, we studied bacterial community composition changes based on 16S rRNA sequencing at two fractions (0.1-0.2 and >0.2 μm) during a 10- day fully factorial mesocosm experiment in the eastern Mediterranean where the pH decreased by ~0.3 units and temperature increased by ~3 °C to project possible future changes in surface waters. The bacterial community experienced significant taxonomic differences driven by the combined effect of time and treatment; a community shift one day after the manipulations was noticed, followed by a similar state between all mesocosms at the third day, and mild shifts later on, which were remarkable mainly under sole acidification. The abundance of
increased in response to warming, while the
clade immediately benefited from the combined acidification and warming. The effect of the acidification itself had a more persistent impact on community composition. This study highlights the importance of studying climate change consequences on ecosystem functioning both separately and simultaneously, considering the ambient environmental parameters.
Viruses interfere with their host's metabolism through the expression of auxiliary metabolic genes (AMGs) that, until now, are mostly studied under large physicochemical gradients. Here, we focus on ...coastal marine ecosystems and we sequence the viral metagenome (virome) of samples with discrete levels of human-driven disturbances. We aim to describe the relevance of viromics with respect to ecological quality status, defined by the classic seawater trophic index (TRIX). Neither viral (family level) nor bacterial (family level, based on 16S rRNA sequencing) community structure correlated with TRIX. AMGs involved in the Calvin and tricarboxylic acid cycles were found at stations with poor ecological quality, supporting viral lysis by modifying the host's energy supply. AMGs involved in "non-traditional" energy-production pathways (3HP, sulfur oxidation) were found irrespective of ecological quality, highlighting the importance of recognizing the prevalent metabolic paths and their intermediate byproducts. Various AMGs explained the variability between stations with poor vs. good ecological quality. Our study confirms the pivotal role of the virome content in ecosystem functioning, acting as a "pool" of available functions that may be transferred to the hosts. Further, it suggests that AMGs could be used as an ultra-sensitive metric of energy-production pathways with relevance in the vulnerable coastal zone and its ecological quality.
Pollution of the marine environment is an emerging threat. Nowadays, engineered nanoparticles (<100 nm) such as zinc, copper and silver are widely used as antimicrobial agents, therefore often ...present in daily-life products. Consequently, the demand and production of nanoparticles are expected to increase. Here, we specifically focus on silver nanoparticles (AgNP). Once released into the environment, AgNPs pose an obvious ecotoxicological risk, potentially affecting ecosystem structure and functioning. For instance, phytoplankton-derived exudates, rich in acidic polysaccharides and amino acids, can abiotically aggregate into microgels such as transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP). Hence, microgels can bridge dissolved and particulate size fractions and facilitate aggregate formation with organic and mineral particles. Both physical and chemical properties make TEP and CSP attractive nutrient hotspots for heterotrophic bacterioplankton. Bacteria, in turn, utilize extracellular enzymes to access these carbon and nitrogen pools. However, knowledge about the mechanisms by which AgNPs might interact with and affect the biogeochemical cycling of TEP and CSP is still insufficient. Therefore, we conducted a mesocosm experiment in the Eastern Mediterranean Sea and investigated the effects of environmentally relevant concentrations of silver ions (Ag+) and AgNP on the properties of TEP and CSP (i.e., area and abundance) along with enzymatic activity measurements. Our results showed that cyanobacteria were likely the primary source of CSP in the ultra-oligotrophic Mediterranean Sea. Also, CSP contributed more to the microgel pool than TEP, as indicated by a strong relationship between CSP and heterotrophic microbial dynamics. While silver (i.e., Ag+ or AgNP) had overall only marginal effects, both species affected the relationships between cell-specific LAPase activity and CSP and cell-specific APase activity and phosphate levels. Thus, Ag+ and AgNP have the potential to regulate microgel dynamics. However, future studies are needed to derive a robust understanding of the effects of silver pollution on the coupling of microgel formation and degradation and the follow-on effect on biogeochemical cycles.
The release of silver into the marine environment is of growing concern as its impact on marine life is not fully understood. Despite previous experiments that have shown toxic effects of silver as ...nanoparticles (AgNPs) and as free ions (Ag
+
) on microbial organisms, the impact on important biogeochemical processes, such as marine nitrogen fixation, remains relatively unexplored. The present study investigated the impact of AgNPs and Ag
+
on nitrogen fixation activity in oligotrophic coastal ecosystems. Nine mesocosm enclosures were set-up in Crete, Greece, for twelve days during May 2019. Three mesocosms were left unamended at ambient light and temperature; three were manipulated with 50 ng AgNPs L
-1
d
-1
and three were amended with 50 ng Ag
+
L
-1
d
-1
. Over the duration of the experiment, mean nitrogen fixation rates proved higher in treated waters; 0.28 ± 0.24 nmol N L
-1
d
-1
and 0.21 ± 0.19 nmol N L
-1
d
-1
in AgNP and Ag
+
which were 2.2 (p< 0.001) and 1.6 (not significant) times higher than control rates of 0.13 ± 0.07 nmol N L
-1
d
-1
respectively. Changes in nitrogen fixation rates were paralleled by significantly higher concentrations of phosphate and silicate in treated versus control mesocosms, suggesting an inhibition of the uptake of these nutrients by non-diazotrophic groups. Sequencing of 16S and 18S rRNA genes showed shifts in community composition over time but only very minor changes could be linked to the Ag treatments. Decreases to the relative abundance of three diatom species were observed in the Ag treatments but these were considered insufficient to support the relative differences in nutrient concentration. It is therefore speculated that there was physiological disruption of nutrient uptake mechanisms of the non-diazotrophic community. A number of potential diazotrophs were detected and the relative sequence abundance of a number of known nitrogen fixing taxa, including
Burkholderiaceae
,
Oceanospirillales
and
Pseudomonadales
correlated with measured nitrogen fixation rates. Phosphorus limitation of diazotrophic activity was therefore lowered relative to other microbial groups in silver amended treatments and significant increases in particulate nitrogen for both Ag treatments indicate an enhancement in cellular N for the nitrogen fixing communities.
A Corrigendum on The presence of silver nanoparticles reduces demand for dissolved phosphorus to the benefit of biological nitrogen fixation in the coastal eastern Mediterranean Sea by Rees AP, ...Faraggiana E, Tait K, Celussi M, Dafnomilli E, Manna V, Manning AJ, Pitta P, Tsiola A and Živanović S (2022). The correct author contributions section appears below: AR planned the experimental procedures, supervised EF, provided quality control to nitrogen fixation data and wrote the manuscript. Andrew P. Rees1*†, Eleonora Faraggiana1,2†, Karen Tait1, Mauro Celussi3, Eleni Dafnomilli4, Vincenzo Manna3, Andrew Manning2, Paraskevi Pitta5, Anastasia Tsiola5 and Snežana Živanović4 * 1Plymouth Marine Laboratory, Plymouth, United Kingdom * 2School of Biological and Marine Sciences, University of Plymouth, Plymouth, United Kingdom * 3Oceanography Division, Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste, Italy * 4Hellenic Centre for Marine Research, Institute of Marine Biology, Biotechnology and Aquaculture, Heraklion, Greece * 5Hellenic Centre for Marine Research, Institute of Oceanography, Heraklion, Greece
Recent estimates of nutrient budgets for the Eastern Mediterranean Sea (EMS) indicate that atmospheric aerosols play a significant role as suppliers of macro- and micro- nutrients to its Low Nutrient ...Low Chlorophyll water. Here we present the first mesocosm experimental study that examines the overall response of the oligotrophic EMS surface mixed layer (Cretan Sea, May 2012) to two different types of natural aerosol additions, “pure” Saharan dust (SD, 1.6 mg l-1) and mixed aerosols (A - polluted and desert origin, 1 mg l-1). We describe the rationale, the experimental set-up, the chemical characteristics of the ambient water and aerosols and the relative maximal biological impacts that resulted from the added aerosols. The two treatments, run in triplicates (3 m3 each), were compared to control-unamended runs. Leaching of approximately 2.1-2.8 and 2.2-3.7 nmol PO4 and 20-26 and 53-55 nmol NOx was measured per each milligram of SD and A, respectively, representing an addition of approximately 30% of the ambient phosphate concentrations. The nitrate/phosphate ratios added in the A treatment were twice than those added in the SD treatment. Both types of dry aerosols triggered a positive change (25-600% normalized per 1 mg l-1 addition) in most of the rate and state variables that were measured: bacterial abundance (BA), bacterial production (BP), Synechococcus (Syn) abundance, chlorophyll-a (chl-a), primary production (PP) and dinitrogen fixation (N2-fix), with relative changes among them following the sequence BP>PP≈N2-fix>chl-a≈BA≈Syn. Our results show that the ‘polluted’ aerosols triggered a relatively larger biological change compared to the SD amendments (per a similar amount of mass addition), especially regarding BP and PP. We speculate that despite the co-limitation of P and N in the EMS, the additional N released by the A treatment may have triggered the relatively larger response in most of the rate and state variables as compared to SD. An implication of our study is that a warmer atmosphere in the future may increase dust emissions and influence the intensity and length of the already well stratified water column in the EMS and hence the impact of the aerosols as a significant external source of new nutrients.
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