Gary Thomas Banta

Estuarine nutrient cycling: The influence of primary producers

Interactions Between Vegetation And Nutrient Dynamics In Coastal Marine Ecosystems: An Introduction by M.F. Pedersen, S.L. Nielsen and G.T. Banta Estuarine Primary Producers by K. Sand-Jensen and S.L. Nielsen Effects Of Nutrient Loading On Shallow Seagrass-Dominated Coastal Systems: Patterns And Processes by J. Hauxwell and I. Valiela Plant Bound Nutrient Transport. Mass Transport In Estuaries And Lagoons by M.R. Flindt, J. Neto, C.L. Amos, M.A. Pardal, A. Bergamasco, C.B. Pedersen and F.O. Andersen Grazing On Pelagic Primary Producers - The Role Of Benthic Suspension Feeders In Estuaries by J.K. Petersen Grazing On Benthic Primary Producers by J. Cebrian Decomposition Of Marine Primary Producers: Consequences For Nutrient Recycling And Retention In Coastal Ecosystems by G.T. Banta, M.F. Pedersen and S.L. Nielsen Burial Of Nutrient In Coastal Sediments: The Role Of Primary Producers by J.J. Middelburg, K. Soetaert, P.M.J. Herman, H.T.S. Boschker and C.R. Heip The Importance Of Primary Producers For Benthic Nitrogen And Phosphorus Cycling by K.J. McGlathery, K. Sundback and I.C. Anderson Denitrification by N. Risgaard-Petersen Attempting A Synthesis - Plant/Nutrient Interactions by S.L. Nielsen, M.F. Pedersen and G.T. Banta

Toxic effects and bioaccumulation of nano-, micron- and ionic-Ag in the polychaete, Nereis diversicolor

There is increasing concern about the toxicities and potential risks, both still poorly understood, of silver nanoparticles for the aquatic environment after their eventual release via wastewater discharges. In this study, the toxicities of sediment associated nano (<100 nm)-, micron (2-3.5 μm)- and ionic (AgNO(3))-Ag on the sediment-dwelling polychaete, Nereis diversicolor, were compared after 10 days of sediment exposure, using survival, DNA damage (comet assay) and bioaccumulation as endpoints. The nominal concentrations used in all exposure scenarios were 0, 1, 5, 10, 25, and 50 μg Ag/g dry weight (dw) sediment. Our results showed that Ag was able to cause DNA damage in Nereis coelomocytes, and that this effect was both concentration- and Ag form-related. There was significantly greater genotoxicity (higher tail moment and tail DNA intensities) at 25 and 50 μg/g dw in nano- and micron-Ag treatments and at 50 μg/g dw in the ionic-Ag treatment compared to the controls (0μg/g dw). The nano-Ag treatment had the greatest genotoxic effect of the three tested Ag forms, and the ionic-Ag treatment was the least genotoxic. N. diversicolor did accumulate sediment-associated Ag from all three forms. Ag body burdens at the highest exposure concentration were 8.56 ± 6.63, 6.92 ± 5.86 and 9.86 ± 4.94 μg/g dw for worms in nano-, micron- and ionic-Ag treatments, respectively, but there was no significant difference in Ag bioaccumulation among the three treatments.

Metabolism of pyrene by the polychaetes Nereis diversicolor and Arenicola marina.

Absorption and elimination of [(14)C-4,5,9,10]pyrene and production of water-insoluble and water-soluble pyrene metabolites by the polychaetes Nereis diversicolor and Arenicola marina were studied. Both polychaete species were capable of rapidly accumulating and eliminating pyrene. Steady state concentrations of pyrene were established in both polychaete species within 5 days of exposure to contaminated sediments, with A. marina having 5-10 times higher bioaccumulation factors than N. diversicolor. Both water-soluble and water-insoluble metabolites were detected in tissues of N. diversicolor and A. marina. After transferring worms to uncontaminated sediment, about 50% of the body burden of parent pyrene was excreted within 1.5 days, with elimination in A. marina being faster than in N. diversicolor. The only identified water-insoluble metabolite produced by N. diversicolor was 1-hydroxypyrene. Pyrene metabolites were present in A. marina, but could not be identified. Long- and short-term absorption experiments showed an increasing production of water-soluble metabolites over time in the lugworm, which strongly suggests the presence of a PAH metabolising system in A. marina.

The influence of organic matter on sorption and fate of glyphosate in soil--comparing different soils and humic substances.

Soil organic matter (SOM) is generally believed not to influence the sorption of glyphosate in soil. To get a closer look on the dynamics between glyphosate and SOM, we used three approaches: I. Sorption studies with seven purified soil humic fractions showed that these could sorb glyphosate and that the aromatic content, possibly phenolic groups, seems to aid the sorption. II. Sorption studies with six whole soils and with SOM removed showed that several soil parameters including SOM are responsible for the strong sorption of glyphosate in soils. III. After an 80 day fate experiment, approximately 40% of the added glyphosate was associated with the humic and fulvic acid fractions in the sandy soils, while this was the case for only approximately 10% of the added glyphosate in the clayey soils. Glyphosate sorbed to humic substances in the natural soils seemed to be easier desorbed than glyphosate sorbed to amorphous Fe/Al-oxides.

Benthic respiration and nitrogen release in Buzzards Bay, Massachusetts

The decomposition of organic matter and the regeneration of nitrogen in the sediments of Buzzards Bay, Massachusetts were examined by measuring benthic fluxes of oxygen and dissolved inorganic nitrogen (DIN). Benthic respiration (O 2 consumption) rates measured from one site yielded an estimate of 65-80 g C m −2 oxidized annually. Comparing the annual release of DIN with the consumption of O 2 led to an estimate of N loss from the benthicpelagic system, most likely as N 2 gas via denitrification, corresponding to 14-32% of the N remineralized from organic matter decomposition. Using path analysis, benthic flux rates of O 2 and DIN over a seasonal cycle in Buzzards Bay were determined to be related to water temperature and sediment photosynthetic pigments (chlorophyll a and phaeopigments). The rate of DIN release was also negatively related to the particulate organic N (PON) pool as well. The relationsbip of benthic fluxes to sedimentary pigment concentrations suggested that pigments were good indicators of labile organic matter input to sediments. Macrofauna appeared to have a direct negative effect, as well as a positive indirect effect on DIN release. Benthic respiration rates were not related to sedimentary particulate organic C (POC) or PON content, or macrofaunal abundances. Release rates of DIN were also unrelated to POC pools. Benthic flux rates measured at 12 sites in Buzzards Bay during August 1989 varied by less than a factor of 2 for benthic respiration and less than a factor of 3 for DIN release. The only environmental factor that emerged from path analysis as related (negatively) to the spatial pattern of benthic flux rates in August was water depth. Other factors, such as organic pools, pigment concentrations, macrofauna, and distance from the New Bedford sewage outfall were not related to the spatial patterns of benthic fluxes in Buzzards Bay. The combination of seasonal and spatial observations indicate that the processes oxidizing organic matter in Buzzards Bay sediments are controlled by temperature and the delivery of labile organic matter to the sediment surface. Benthic flux rates in Buzzards Bay were generally low, but N recycling efficiency was high, relative to similar coastal environments

Toxicity and bioaccumulation of sediment-associated silver nanoparticles in the estuarine polychaete, Nereis (Hediste) diversicolor

In this study, the toxicities of sediment-associated silver added to sediment as commercially available silver nanoparticles (Ag NPs, 20 and 80 nm) and aqueous Ag (AgNO3) to the estuarine polychaete, Nereis (Hediste) diversicolor, were investigated for both individual and subcellular endpoints after 10 d of exposure. Both Ag NP types were characterized in parallel to the toxicity studies and found to be polydispersed and overlapping in size. Burrowing activity decreased (marginally) with increasing Ag concentration and depended on the form of Ag added to sediment. All worms accumulated Ag regardless of the form in which it was added to the sediment, and worm size (expressed as dry weight) was found to significantly affect bioaccumulation such that smaller worms accumulated more Ag per body weight than larger worms. Lysosomal membrane permeability (neutral red retention time, NRRT) and DNA damage (comet assay tail moment and tail DNA intensity %) of Nereis coelomocytes increased in a concentration-dependent manner in all three Ag treatments. Ag NP treatments were more toxic than aqueous Ag for all toxicity endpoints, even though bioaccumulation did not differ significantly among Ag forms. No significant difference in toxicity was observed between the two Ag NP treatments which was attributed to their overlap in particle size.

Bioaccumulation and effects of different-shaped copper oxide nanoparticles in the deposit-feeding snail Potamopyrgus antipodarum

Copper oxide (CuO) nanoparticles (NPs) are among the most widely used engineered NPs and are thus likely to end up in the environment, predominantly in sediments. Copper oxide NPs have been found to be toxic to a variety of (mainly pelagic) organisms, but to differing degrees. In the present study, the influence of CuO NP shape on bioavailability and toxicity in the sediment-dwelling freshwater gastropod Potamopyrgus antipodarum was examined. In 2 separate studies, snails were exposed to either clean sediment or sediment spiked with either aqueous Cu or CuO NPs of different shapes (rods, spheres, or platelets) at 240 µg Cu/g dry weight of sediment (nominal). In neither of the studies was survival found to be related to Cu form (i.e., free ion vs particle) or shape, whereas snail growth was severely influenced by both form and shape. Reproduction was affected (by CuO NP spheres and aqueous Cu) only when estimated as the total number (live plus dead) of juveniles produced per snail per week. Both the aqueous and particulate forms of Cu were available for uptake by snails when mixed into sediment. However, Cu body burden was not directly related to observed effects. The present study stresses the need for both a better understanding of uptake mechanisms and internal distribution pathways of NPs and an assessment of long-term consequences of NP exposure.

Biogeochemical Processes and Marine Benthic Community Structure: Which Follows Which?

Overall rates of decomposition in sediments appear to be only weakly affected by benthic animals. Thus we predict that changes in benthic community structure would have only a small effect on decomposition although the pathways of decomposition (aerobic vs. anaerobic) might shift. The converse does not appear to be true, however; we expect the structure of benthic communities to change with a change in decomposition rates, with some communities being excluded from sediments with high rates of decomposition.

Bioaccumulation, subcellular distribution and toxicity of sediment-associated copper in the ragworm Nereis diversicolor: The relative importance of aqueous copper, copper oxide nanoparticles and microparticles.

The sediment-dwelling ragworm, Nereis diversicolor was exposed to sediment spiked with aqueous Cu (CuAq, CuCl2), CuO nanoparticles (CuONP) or CuO microparticles (CuOMicro) at 150 μg Cu g(-1) dw sediment for 10d. Exposures to CuAq and CuOMicro caused mortality (62.5 and 37.5%, respectively), whereas mean burrowing time increased during exposure to CuAq and CuONP from 0.12 h (controls) to 19.3 and 12.2 h, respectively. All Cu treatments bioaccumulated, especially CuAq (up to 4 times more than the other treatments). Cu was roughly equally distributed among the five subcellular fractions in controls and worms exposed to CuONP or CuOMicro. In contrast, ≈50% of accumulated Cu in CuAq exposed worms was found in metal rich granules and significantly more Cu was present in heat-denatured proteins and organelles than in worms exposed to CuOMicro or in controls. Our results suggest that Cu form affects its bioaccumulation and subsequent toxicity and detoxification in a polychaete like N. diversicolor.

Assessing and managing multiple risks in a changing world – The Roskilde recommendations

Roskilde University (Denmark) hosted a November 2015 workshop, Environmental Risk-Assessing and Managing Multiple Risks in a Changing World. This Focus article presents the consensus recommendations of 30 attendees from 9 countries regarding implementation of a common currency (ecosystem services) for holistic environmental risk assessment and management; improvements to risk assessment and management in a complex, human-modified, and changing world; appropriate development of protection goals in a 2-stage process; dealing with societal issues; risk-management information needs; conducting risk assessment of risk management; and development of adaptive and flexible regulatory systems. The authors encourage both cross-disciplinary and interdisciplinary approaches to address their 10 recommendations: 1) adopt ecosystem services as a common currency for risk assessment and management; 2) consider cumulative stressors (chemical and nonchemical) and determine which dominate to best manage and restore ecosystem services; 3) fully integrate risk managers and communities of interest into the risk-assessment process; 4) fully integrate risk assessors and communities of interest into the risk-management process; 5) consider socioeconomics and increased transparency in both risk assessment and risk management; 6) recognize the ethical rights of humans and ecosystems to an adequate level of protection; 7) determine relevant reference conditions and the proper ecological context for assessments in human-modified systems; 8) assess risks and benefits to humans and the ecosystem and consider unintended consequences of management actions; 9) avoid excessive conservatism or possible underprotection resulting from sole reliance on binary, numerical benchmarks; and 10) develop adaptive risk-management and regulatory goals based on ranges of uncertainty. Environ Toxicol Chem 2017;36:7-16.