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Semivolatile and persistent organic pollutants (POPs) undergo atmospheric transport before being deposited to the oceans, where they partition to phytoplankton organic matter. The goal of this study was to determine the toxicity of naturally occurring complex mixtures of organic pollutants to temperate and polar phytoplankton communities from the Mediterranean Sea, the North East (NE) Atlantic, and Southern Oceans. The cell abundance of the different phytoplankton groups, chlorophyll a concentrations, viability of the cells, and growth and decay constants were monitored in response to addition of a range of concentrations of mixtures of organic pollutants obtained from seawater extracts. Almost all of the phytoplankton groups were significantly affected by the complex mixtures of non-polar and polar organic pollutants, with toxicity being greater for these mixtures than for single POPs or simple POP mixtures. Cocktails' toxicity arose at concentrations as low as tenfold the field oceanic levels, probably due to a higher chemical activity of the mixture than of simple POPs mixtures. Overall, smaller cells were the most affected, although Mediterranean picophytoplankton was significantly more tolerant to non-polar POPs than picophytoplankton from the Atlantic Ocean or the Bellingshausen Sea microphytoplankton., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Volatile methyl siloxanes (VMS) are high-production synthetic compounds, ubiquitously found in the environment of source regions. Here, we show for the first time the occurrence of VMS in soils, vegetation, phytoplankton, and krill samples from the Antarctic Peninsula region, which questions previous claims that these compounds are "flyers" and do not significantly reach remote ecosystems. Cyclic VMS are the predominant compounds, with concentrations ranging from the limits of detection to 110 ng/g in soils. Concentrations of cyclic VMS in phytoplankton are negatively correlated with sea surface salinity, indicating a source from ice and snow melting and consistent with snow depositional inputs. After the summer snow melting, VMS accumulate in the Southern Ocean and Antarctic biota. Therefore, once introduced into the marine environment, VMS are eventually trapped by the biological pump and, thus, behave as "single hoppers". Conversely, VMS in soils and vegetation behave as "multiple hoppers" due to their high volatility.

The Southern Ocean is one of the most pristine environments in the world, but is nonetheless affected by inputs of persistent organic pollutants (POPs). In the present work, we report the concentrations of hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), and 26 polychlorinated biphenyl (PCBs) congeners in seawater and phytoplankton from samples obtained during three Antarctic cruises in 2005, 2008, and 2009. The levels of PCBs, HCHs, and HCB are low in comparison to the few previous reports for this region and studies from other oceans. The long-term decline of POP concentrations in the Southern Ocean seawater since early 1980 is consistent with half-lives of 3.4 and 5.7 years for HCHs and PCBs, respectively. There is a large variability of PCBs, HCHs, and HCB concentrations in water and phytoplankton within the Bransfield Strait, South Scotia, Weddell, and Bellingshausen Seas that masks the differences between the studied Seas. However, the variability of PCBs concentrations in phytoplankton is significantly correlated with phytoplankton biomass, with lower concentrations in the most productive waters. This trend is more apparent for the more hydrophobic congeners, consistent with the role of settling fluxes of organic matter decreasing the concentrations of hydrophobic POPs in productive waters. The present work reports the most extensive data set on concentrations in seawater and phytoplankton for the Southern Ocean, and points to the important biogeochemical drivers, such as settling and degradation, influencing the occurrence of POPs in the ocean.

Hydroxyl radical (OH), the main atmospheric oxidant at the global scale, is believed to play an important role in the dynamics of dissolved organic matter in the sea. Herein, we provide evidence, on the basis of seven experiments performed in contrasting ecosystems (subtropical NE Atlantic and Antarctic waters), of high fluxes of atmospheric OH into the surface oceanic layer, particularly during afternoon events. The experiments demonstrated a tight negative relationship between phytoplankton abundance and the concentration of OH in surface seawater, with acute cell death during afternoon atmospheric OH influx events. The effect of OH radical was higher for picophytoplankton organisms, with Prochlorococcus showing the highest decay rate and the shortest half-life among the phytoplankton populations habiting the ocean surface layers. Our results provide evidence for a high toxicity of atmospheric-derived OH radical to phytoplankton of the surface layer of the ocean., (© 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2012 The American Society of Photobiology.)

The goal of this study was to experimentally assess the coupling between primary producer biomass dynamics and the distribution and fate of persistent organic pollutants (POPs) in a lake pelagic ecosystem. This was done by following the short-term evolution of polychlorinated biphenyl (PCB) concentrations in water and biota (phytoplankton and zooplankton) and the variability of bioconcentration (BCF), biomagnification (BMF), and bioaccumulation (BAF) factors during the development of a typical spring ecological progression in which the phytoplankton bloom is followed by a peak in the zooplankton abundance. The bulk of compounds with log K(OW) > 6.5 in the lake epilimnion was mainly associated with primary producer biomass. The phytoplankton biological pump was a major driver of POP export from the epilimnion, causing the decline of dissolved-phase concentrations. The BCF of phytoplankton for the more hydrophobic PCBs showed minima during the period of biomass climax. The concentration in the zooplankton of all selected PCBs sharply declined from March to May, with BAFs having minima in the post algal bloom phase. Biomagnification occurred during the pre algal bloom and algal bloom phases but appeared to be absent during the post algal bloom. This study highlights the occurrence of a prompt and complex response in the fate and distribution of POPs to dynamic biogeochemical control. Within the frame of the ecological succession, phytoplankton and zooplankton biomass dynamics produced bioaccumulation metrics varying over 1-2 orders of magnitude in the time frame of a few weeks and resulted in reduced trophic web exposure.

Polycyclic Aromatic Hydrocarbons' (PAHs) toxicity is enhanced by the presence of ultraviolet radiation (UVR), which levels have arisen due to the thinning of the ozone layer. In this study, PAHs' phototoxicity for natural marine phytoplankton was tested. Different concentrations of a mixture of 16 PAHs were added to natural phytoplankton communities from the Mediterranean Sea, Atlantic, Arctic and Southern Oceans and exposed to natural sunlight received in situ, including treatments where the UVR bands were removed. PAHs' toxicity was observed for all the phytoplankton groups studied in all the waters and treatments tested, but only for the pico-sized group a synergetic effect of the mixture and UVR was observed (p=0.009). When comparing phototoxicity in phytoplankton from oligotrophic and eutrophic waters, synergy was only observed at the oligotrophic communities (p=0.02) where pico-sized phytoplankton dominated. The degree of sensitivity was related to the trophic degree, decreasing as Chlorophyll a concentration increased., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Long range atmospheric transport and deposition is a significant introduction pathway of organic pollutants to remote oceanic regions, leading to their subsequent accumulation in marine organisms. Persistent organic pollutants (POPs) bioconcentrate in planktonic food webs and these exert a biogeochemical control on the regional and global cycling of POPs. Therefore, an important issue is to determine whether the anthropogenic chemical perturbation of the biosphere introduced by the myriad of organic pollutants present in seawater influences phytoplankton abundance and productivity. The results reported here from five sets of experiments performed in the NE Atlantic Ocean show that there is a toxic effect induced by trace levels of complex mixtures of organic pollutants on phytoplankton oceanic communities. The levels of single pollutant, such as phenanthrene and pyrene, at which lethality of phytoplankton is observed are high in comparison to field levels. Complex mixtures of organic pollutants, however, have an important toxic effect on phytoplankton abundances, viability and concentrations of Chlorophyll a at pollutant concentrations 20-40 folds those found in the open ocean. The toxicity of these complex mixtures of organic pollutants exceeds by 10(3) times the toxicity expected for a single pollutant. Therefore, our results point out the need for a systematic investigation of the influence of complex mixtures of organic hydrophobic pollutants to oceanic phytoplankton communities, a perturbation not accounted for on previous assessments of anthropogenic pressures in the marine environment., ((c) 2010 Elsevier Ltd. All rights reserved.)

The toxicity of pyrene and phenanthrene to phytoplankton was studied by analyzing the effect on the growth, abundance and cell viability of cultured species and natural communities of the Atlantic Ocean and the Mediterranean Sea. A decrease in cell abundance, and growth rate was observed as concentration of PAHs increased, with catastrophic cell mortality induced at the highest PAH concentration tested. A strong positive linear relationship was observed between the LC50 (the PAH concentration at which cell population will decline by a half), and the species cell volume, for both phenanthrene and pyrene. Natural communities were however significantly more sensitive to PAHs than cultured phytoplankton, as indicated by the lower slope (e.g. 0.23 and 0.65, respectively, for pyrene) of the relationship LC50 vs. cell volume. The results highlight the importance of cell size in determining the phytoplankton sensitivity to PAHs identifying the communities from the oligotrophic ocean to be more vulnerable.

Phytoplankton and bacteria play an important role on the biogeochemical cycles of persistent organic pollutants (POPs). However, experimental data and quantitative knowledge of the kinetics of uptake and depuration of most POPs by bacteria and phytoplankton are scarce. In the present paper, a procedure to predict the sorption kinetics to bacteria and phytoplankton is developed. The prediction method is the combination of a mechanistic model for sorption and quantitative structure-activity relationships relating bioconcentration factors and membrane permeability to the chemical physical-chemical properties. The model consists of two compartments where the first compartment is the cellular surface and the second compartment is the cell biomass or matrix. Equations for estimating uptake and depuration rate constants into the matrix and adsorption and desorption rate constants onto the surface are obtained. These expressions depend on the physical-chemical properties of the chemical, the environmental temperature, the microorganism size, and species-specific quality of organic matter. While microorganism shape has a secondary influence on uptake dynamics, microorganism size and chemical hydrophobicity arise as the key factors controlling the kinetics of POP incorporation into bacteria and plankton. Uptake, depuration, adsorption, and desorption rate constants are reported for POPs such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated dioxins and furans (PCDD/Fs), and POPs of emerging concern, such as polybrominated diphenyl ethers (PBDEs). Finally, implications of uptake and depuration dynamics on the biogeochemical cycling of POPs are discussed.

A diel (24-h) cycle with daytime atmospheric concentrations higher than nighttime concentrations by a factor of 1.5-3 was observed for several low molecular weight polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in remote areas of the tropical South Atlantic during a cruise in October--November 2005. In contrast, high molecular weight PCBs and PAHs did not display diurnal variability. A model which has successfully explained diel variability of persistent organic pollutants (POPs) over land could not reproduce the observed diel cycle by considering variability in temperature, atmospheric OH radical concentrations, atmospheric boundary layer height and wind speed as causal factors. We used the model to conduct two bounding scenarios to explore the possibility that phytoplankton biomass turn-over in the surface ocean drives the observed variability in air concentrations. The model could only qualitatively reproduce the field observations of diel variability for low chlorinated PCB congeners when the ocean acts as a source of pollutants to the atmosphere, and when variability in biomass drives variability in the capacity of the surface ocean. [ABSTRACT FROM AUTHOR]

During the last decade the number of seawater dimethylsulfide (DMS) concentration measurements has increased substantially. The importance this gas, emitted from the ocean to the atmosphere, may have in the cloud microphysics and hence in the Earth albedo and radiation budget, makes it necessary to accurately reproduce the global distribution. Recently, the monthly global DMS climatology has been updated taking advantage of the threefold increased size and better resolved distribution of the observations available in the DMS database. Here, the emerging patterns found with the previous versions of the database and climatology are explored with the updated versions. The statistical relationships between the seasonalities of DMS concentrations and other variables are re-examined. The positive correlation previously found between surface seawater DMS and the daily-averaged climatological solar radiation dose in the upper mixed layer of the open ocean is confirmed with both the updated DMS database and climatology. Re-examination of the latitudinal match-mismatch between the seasonalities of DMS and phytoplankton, represented by the chlorophyll a concentration, reveals that they are highly positively correlated in latitudes higher than 40°, but anti-correlated in the 20°-40° latitudinal bands of both hemispheres. Overall, these global emerging patterns provide key information to further understanding the factors that control the emission of volatile sulfur from the ocean. The large uncertainties associated with the methodologies used in global computations, however, call for caution in using these emerging patterns as predictive tools, and prompt to the design of time series and process-oriented studies aimed at testing the validity of the observed relationships. [ABSTRACT FROM AUTHOR]

Examines the effect of air-water and water-phytoplankton exchange processes in persistent organic pollutants (POPs). Factors affecting air-water exchange; Comparison between air-water and water-phytoplankton exchange; Influence of phytoplankton on POPs concentration; Reaction of water-phytoplankton fluxes in different water concentration.

Persistent organic pollutants (POPs) reach Antarctica through atmospheric transport, oceanic currents, and to minor extent, by migratory animals. The Southern Ocean is a net sink for many POPs, with a key contribution of the settling fluxes of POPs bound to organic matter (biological pump). However, little is known about POP transfer through the food web in the Southern Ocean and Antarctic waters, where krill is an important ecological node. In this study, we assessed the occurrence of polychlorinated dibenzo- p -dioxins and furans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) in Antarctic krill ( Euphausia superba ) from the Bellingshausen, South Scotia and Weddell Seas around the Antarctic Peninsula. The concentrations of PCDD/Fs, PBDEs and PCBs in krill showed a large variability and the average were higher (generally within a factor 3) than those previously reported for eastern Antarctica. This result highlights regional differences related to atmospheric transport and deposition, and also probable regional sources due to human activities. Bioaccumulation and biomagnification factors for PCBs in krill were estimated using previously reported phytoplankton and seawater concentrations for this region. These suggested a near water-krill equilibrium for PCBs, which was not observed for water-phytoplankton partitioning. The estimated removal settling fluxes of PCBs due to the biological pump were several orders of magnitude higher than the estimated fluxes of PCBs transferred from phytoplankton to krill. [ABSTRACT FROM AUTHOR]

Planktonic food webs play an important role driving the environmental fate of persistent organic pollutants, and POP accumulation in phytoplankton has been previously studied for its importance as a first step in the aquatic food webs. However, little is known about the accumulation and cycling of organic pollutants between zooplankton and water. The present study shows the results of laboratory experiments on the bioconcentration (by passive uptake) of polycyclic aromatic hydrocarbons in phytoplankton (Rhodomonas sauna) and accumulation in copepods (Paracartia(acartia) grani), by ingestion and diffusion. Both bioconcentration (BCF) and bioaccumulation (BAF) factors show significant correlation with the octanol-water partition coefficient (Kow) for phytoplankton and zooplankton. The BCF values for phytoplankton were 2 orders of magnitude higherthanthose for copepods. The analysis of fecal pellets shows that elimination by defecation is mainly significantfor PAHs taken up from ingested phytoplankton but not due to passive uptake. However, the dominant elimination mechanisms are by far metabolism and diffusive depuration. Indeed, the mass balance suggests that metabolism of PAHs by copepods is a significant process that could play a role in the fate of PAHs in the water column. Uptake, depuration, eggestion, and ingestion rates increased with hydrophobicity of the chemical, while the metabolism rate was slightly higher for the less hydrophobic compounds. Passive partitioning dominated the accumulation of POPs in zooplankton. The derivation of all the uptake and loss rate constants for PAHs opensthe doorto future modeling studies of the role of zooplankton in PAH cycling in the marine environment. [ABSTRACT FROM AUTHOR]

Ship-board air samples collected between The Netherlands and South Africa in January-February 2001 were analyzed for PCBs and selected organochlorine compounds. Broad latitudinal trends in compound concentrations were influenced by proximity to source areas, land, and air mass origin. Lowest concentrations were observed in the remote south Atlantic (1-32° 5), where LPCB concentrations were ∼10 pg m-3. Here, a diurnal cycle was noted for some PCB congeners, with the daytime concentrations higher than the nighttime concentrations, typically by a factor of 1.5-2.5. The data are consistent with a close coupling of air-open ocean concentrations, which has important implications for future rates of POP removal from the global "recyclable pool". The observations are discussed in the context of the potential controlling variables. Interactions between the phytoplankton and the dissolved phase are implicated in controlling the observations made here and a hypothesis to explain the cycling trends is presented. However, the precise mechanisms remain unclear; further studies are urgently required to elucidate them. [ABSTRACT FROM AUTHOR]