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1.
Yale J Biol Med ; 91(4): 375-389, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30588205

RESUMO

The development of a theory to underpin the obligate mutualist interactions that appear to be ubiquitous in nature has not proceeded at the same pace as the development of theory to support competition and predation. A constraint may be that obligate mutualism appears unable to be presented in the simple linear models that have so successfully served as heuristics for the other interactions. A number of simple nonlinear models have been used to propose explanations of obligate mutualism, but these solutions are often predicated on careful choices of functional forms. We present a theory of obligate mutualism in an explicit mass-conserving framework using simple models that are robust to choices of functional forms.


Assuntos
Simbiose , Modelos Lineares , Modelos Biológicos
2.
Bull Math Biol ; 2018 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-30209744

RESUMO

Pollination interactions are common, and their maintenance is critical for many food crops upon which human populations depend. Pollination is a mutualism interaction; together with predation and competition, mutualism makes up the triumvirate of fundamental interactions that control population dynamics. Here we examine pollination interactions (nectar reward for gamete transport service) using a simple heuristic model similar to the Lotka-Volterra models that have underpinned our understanding of predation and competition so effectively since the 1920s. We use a genetic algorithm to simulate the eco-evolutionary interactions of the plant and pollinator populations and examine the distributions of the parameter values and zero isoclines to infer the relative ubiquity of the various eco-evolutionary outcomes possible in the model. Our results suggest that trade-offs between costs and benefits for the pollinator may be a key component of obligate pollination systems in achieving adaptive success creating and stably occupying mutualist niches.

3.
Sci Rep ; 8(1): 14048, 2018 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-30232386

RESUMO

It is proposed that emissions of volatile sulfur compounds by coral reefs contribute to the formation of a biologically-derived feedback on sea surface temperature (SST) through the formation of marine biogenic aerosol (MBA). The direction and strength of this feedback remains uncertain and constitutes a fundamental constraint on predicting the ability of corals to cope with future ocean warming. We investigate the effects of elevated SST and irradiance on satellite-derived fine-mode aerosol optical depth (AOD) throughout the Great Barrier Reef, Australia (GBR) over an 18-year time period. AOD is positively correlated with SST and irradiance and increases two-fold during spring and summer with high frequency variability. As the influence of non-biogenic and distant aerosol sources are found to be negligible, the results support recent findings that the 2,300 km stretch of coral reefs can be a substantial source of biogenic aerosol and thus, influence local ocean albedo. Importantly however, a tipping point in the coral stress response is identified, whereby thermal stress reaches a point that exceeds the capacity of corals to influence local atmospheric properties. Beyond this point, corals may become more susceptible to permanent damage with increasing stress, with potential implications for mass coral bleaching events.

4.
Ambio ; 47(6): 671-681, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29397545

RESUMO

We investigate the correlation between stress-related compounds produced by corals of the Great Barrier Reef (GBR) and local atmospheric properties-an issue that goes to the core of the coral ecosystem's ability to survive climate change. We relate the variability in a satellite decadal time series of fine-mode aerosol optical depth (AOD) to a coral stress metric, formulated as a function of irradiance, water clarity, and tide, at Heron Island in the southern GBR. We found that AOD was correlated with the coral stress metric, and the correlation increased at low wind speeds, when horizontal advection of air masses was low and the production of non-biogenic aerosols was minimal. We posit that coral reefs may be able to protect themselves from irradiance stress during calm weather by affecting the optical properties of the atmosphere and local incident solar radiation.


Assuntos
Aerossóis , Mudança Climática , Recifes de Corais , Animais , Antozoários , Austrália
5.
Environ Sci Technol ; 52(5): 3195-3201, 2018 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-29397707

RESUMO

The discarding of plastic products has led to the ubiquitous occurrence of microplastic particles in the marine environment. The uptake and depuration kinetics of ingested microplastics for many marine species still remain unknown despite its importance for understanding bioaccumulation potential to higher trophic level consumers. In this study, Antarctic krill ( Euphausia superba) were exposed to polyethylene microplastics to quantify acute toxicity and ingestion kinetics, providing insight into the bioaccumulation potential of microplastics at the first-order consumer level. In the 10 day acute toxicity assay, no mortality or dose-dependent weight loss occurred in exposed krill, at any of the exposure concentrations (0, 10, 20, 40, or 80% plastic diet). Krill exposed to a 20% plastic diet for 24 h displayed fast uptake (22 ng mg-1 h-1) and depuration (0.22 h-1) rates, but plastic uptake did not reach steady state. Efficient elimination also resulted in no bioaccumulation over an extended 25 day assay, with most individuals completely eliminating their microplastic burden in less than 5 days post exposure. Our results support recent findings of limited acute toxicity of ingested microplastics at this trophic level, and suggest sublethal chronic end points should be the focus of further ecotoxicological investigation.

6.
Glob Chang Biol ; 24(4): 1500-1510, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29284198

RESUMO

Southern hemisphere humpback whales (Megaptera novaeangliae) rely on summer prey abundance of Antarctic krill (Euphausia superba) to fuel one of the longest-known mammalian migrations on the planet. It is hypothesized that this species, already adapted to endure metabolic extremes, will be one of the first Antarctic consumers to show measurable physiological change in response to fluctuating prey availability in a changing climate; and as such, a powerful sentinel candidate for the Antarctic sea-ice ecosystem. Here, we targeted the sentinel parameters of humpback whale adiposity and diet, using novel, as well as established, chemical and biochemical markers, and assembled a time trend spanning 8 years. We show the synchronous, inter-annual oscillation of two measures of humpback whale adiposity with Southern Ocean environmental variables and climate indices. Furthermore, bulk stable isotope signatures provide clear indication of dietary compensation strategies, or a lower trophic level isotopic change, following years indicated as leaner years for the whales. The observed synchronicity of humpback whale adiposity and dietary markers, with climate patterns in the Southern Ocean, lends strength to the role of humpback whales as powerful Antarctic sea-ice ecosystem sentinels. The work carries significant potential to reform current ecosystem surveillance in the Antarctic region.


Assuntos
Comunicação Animal , Ecossistema , Jubarte/fisiologia , Camada de Gelo , Animais , Regiões Antárticas , Mudança Climática , Estações do Ano
7.
Environ Sci Technol ; 51(23): 13929-13937, 2017 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-29120176

RESUMO

In the first multiyear sampling effort for POPs in the eastern Antarctic atmosphere, 32 PCBs and 38 organochlorine pesticides were targeted in air collected with a high-flow-through passive sampler. Agricultural chemicals were found to dominate atmospheric profiles, in particular HCB and endosulfan-I, with average concentrations of 12 600 and 550 fg/m3, respectively. HCB showed higher concentrations in the austral summer, indicative of local, temperature-dependent volatilisation, while endosulfan-I appeared to show fresh, late-austral-summer input followed by temporally decreasing levels throughout the year. The current-use herbicide, trifluralin, and the legacy pesticides mirex and toxaphene, were detected in Antarctic air for the first time. Trifluralin was observed at low but increasing levels over the five-year period. Its detection in the Antarctic atmosphere provides evidence of its persistence and long-range environmental transport capability. While a time frame of five years exceeds the duration of most Antarctic air monitoring efforts, it is projected that continuous monitoring at the decadal scale is required to detect an annual 10% change in atmospheric concentrations of key analytes. This finding emphasizes the importance of continuous, long-term monitoring efforts in polar regions, that serve a special role as sentinel environments of hemispheric chemical usage trends.


Assuntos
Poluentes Atmosféricos , Monitoramento Ambiental , Regiões Antárticas , Atmosfera , Hidrocarbonetos Clorados , Praguicidas , Bifenilos Policlorados
8.
Environ Sci Technol ; 51(16): 8944-8952, 2017 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-28715890

RESUMO

Complementary sampling of air, snow, sea-ice, and seawater for a range of organochlorine pesticides (OCPs) was undertaken through the early stages of respective spring sea-ice melting at coastal sites in northeast Greenland and eastern Antarctica to investigate OCP concentrations and redistribution during this time. Mean concentrations in seawater, sea-ice and snow were generally greater at the Arctic site. For example, α-HCH was found to have the largest concentrations of all analytes in Arctic seawater and sea-ice meltwater samples (224-253 and 34.7-48.2 pg·L-1 respectively compared to 1.0-1.3 and <0.63 pg·L-1 respectively for Antarctic samples). Differences in atmospheric samples were generally not as pronounced however. Findings suggest that sea-ice OCP burdens originate from both snow and seawater. The distribution profile between seawater and sea-ice showed a compound-dependency for Arctic samples not evident with those from the Antarctic, possibly due to full submersion of sea-ice at the former. Seasonal sea-ice melt processes may alter the exchange rates of selected OCPs between air and seawater, but are not expected to reverse their direction, which fugacity modeling indicates is volatilisation in the Arctic and net deposition in the Antarctic. These predictions are consistent with the limited current observations.


Assuntos
Hidrocarbonetos Clorados , Praguicidas , Regiões Antárticas , Regiões Árticas , Monitoramento Ambiental , Groenlândia , Gelo , Água do Mar
9.
Environ Sci Technol ; 50(15): 8001-9, 2016 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-27348023

RESUMO

This study contributes new data on the spatial variability of persistent organic pollutants in the Indian-Pacific sector of the Southern Ocean and represents the first empirical data obtained from this region in 25 years. Paired high-volume atmospheric and seawater samples were collected along a transect between Australia and Antarctica to investigate the latitudinal dependence of the occurrence and distribution of legacy organochlorine pesticides (OCPs) and the current use pesticide chlorpyrifos in the Southern Ocean. Dissolved ΣHCH and dieldrin concentrations decreased linearly with increasing latitude from 7.7 to 3.0 and from 1.0 to 0.6 pg·L(-1), respectively. There was no consistent trend observed in the latitudinal profile of atmospheric samples; however, some compounds (such as dieldrin) showed reduced concentrations from 7.5-3.4 to 2.7-0.65 pg·m(-3) at the highest latitudes south of the Polar Front. Chlorpyrifos was found in samples from this area for the first time. Estimated air-seawater fugacity ratios and fluxes indicate a current net deposition between -3600 and -900, -6400 and -400, and -1400 and -200 (pg·m(-2)·d(-1)) for γ-HCH, dieldrin, and chlorpyrifos, respectively. These findings suggest that, under current climatic conditions, the Southern Ocean reservoir in the Indian-Pacific sector serves as an environmental sink rather than a source of OCPs to the atmosphere.


Assuntos
Poluentes Atmosféricos , Hidrocarbonetos Clorados , Monitoramento Ambiental , Oceanos e Mares , Praguicidas , Água do Mar
10.
Environ Toxicol Chem ; 35(9): 2182-91, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-26889639

RESUMO

Multimedia models based on chemical fugacity, solved numerically, play an important role in investigating and quantifying the environmental fate of chemicals such as persistent organic pollutants. These models have been used extensively in studying the local and global distribution of chemicals in the environment. The present study describes potential sources of error that may arise from the formulation and numerical solution of environmental fugacity models. The authors derive a general fugacity equation for the rate of change of mass in an arbitrary volume (e.g., an environmental phase). Deriving this general equation makes clear several assumptions that are often not articulated but can be important for successfully applying multimedia fugacity models. It shows that the homogeneity of fugacity and fugacity capacity in a volume (the homogeneity assumption) is fundamental to formulating discretized fugacity models. It also shows that when using the fugacity rather than mass as the state-variable, correction terms may be necessary to accommodate environmental factors such as varying phase temperatures and volume. Neglecting these can lead to conservation errors. The authors illustrate the manifestation of these errors using heuristic multimedia fugacity models. The authors also show that there are easily avoided errors that can arise in mass state-variable models if variables are not updated appropriately in the numerical integration scheme. Environ Toxicol Chem 2016;35:2182-2191. © 2016 SETAC.


Assuntos
Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Modelos Teóricos , Simulação por Computador , Poluentes Ambientais/química , Previsões , Modelos Químicos , Volatilização
11.
Environ Sci Technol ; 49(1): 103-12, 2015 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-25478728

RESUMO

This study investigated the role of a permanently manned Australian Antarctic research station (Casey Station) as a source of contemporary persistent organic pollutants (POPs) to the local environment. Polybrominated diphenyl ethers (PBDEs) and poly- and perfluoroalkylated substances (PFASs) were found in indoor dust and treated wastewater effluent of the station. PBDE (e.g., BDE-209 26-820 ng g(-1) dry weight (dw)) and PFAS levels (e.g., PFOS 3.8-2400 ng g(-1) (dw)) in dust were consistent with those previously reported in homes and offices from Australia, reflecting consumer products and materials of the host nation. The levels of PBDEs and PFASs in wastewater (e.g., BDE-209 71-400 ng L(-1)) were in the upper range of concentrations reported for secondary treatment plants in other parts of the world. The chemical profiles of some PFAS samples were, however, different from domestic profiles. Dispersal of chemicals into the immediate marine and terrestrial environments was investigated by analysis of abiotic and biotic matrices. Analytes showed decreasing concentrations with increasing distance from the station. This study provides the first evidence of PFAS input to Polar regions via local research stations and demonstrates the introduction of POPs recently listed under the Stockholm Convention into the Antarctic environment through local human activities.


Assuntos
Monitoramento Ambiental , Éteres Difenil Halogenados/análise , Substâncias Perigosas/análise , Hidrocarbonetos Fluorados/análise , Anfípodes/química , Animais , Regiões Antárticas , Briófitas/química , Poeira/análise , Meio Ambiente , Sedimentos Geológicos/análise , Halogenação , Líquens/química , Perciformes , Fitoplâncton/química , Pesquisa , Poluentes do Solo/análise , Águas Residuárias/análise
12.
Environ Toxicol Chem ; 33(7): 1638-49, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24733631

RESUMO

Humpback whales are iconic mammals at the top of the Antarctic food chain. Their large reserves of lipid-rich tissues such as blubber predispose them to accumulation of lipophilic contaminants throughout their lifetime. Changes in the volume and distribution of lipids in humpback whales, particularly during migration, could play an important role in the pharmacokinetics of lipophilic contaminants such as the organochlorine pesticide hexachlorobenzene (HCB). Previous models have examined constant feeding and nonmigratory scenarios. In the present study, the authors develop a novel heuristic model to investigate HCB dynamics in a humpback whale and its environment by coupling an ecosystem nutrient-phytoplankton-zooplankton-detritus (NPZD) model, a dynamic energy budget (DEB) model, and a physiologically based pharmacokinetic (PBPK) model. The model takes into account the seasonal feeding pattern of whales, their energy requirements, and fluctuating contaminant burdens in the supporting plankton food chain. It is applied to a male whale from weaning to maturity, spanning 20 migration and feeding cycles. The model is initialized with environmental HCB burdens similar to those measured in the Southern Ocean and predicts blubber HCB concentrations consistent with empirical concentrations observed in a southern hemisphere population of male, migrating humpback whales. Results show for the first time some important details of the relationship between energy budgets and organochlorine pharmacokinetics.


Assuntos
Migração Animal , Jubarte/fisiologia , Hidrocarbonetos Clorados/metabolismo , Poluentes Químicos da Água/metabolismo , Animais , Regiões Antárticas , Feminino , Cadeia Alimentar , Hexaclorobenzeno/análise , Hexaclorobenzeno/metabolismo , Hidrocarbonetos Clorados/análise , Metabolismo dos Lipídeos , Masculino , Modelos Biológicos , Praguicidas/análise , Praguicidas/metabolismo , Poluentes Químicos da Água/análise
13.
J Hazard Mater ; 263 Pt 2: 458-66, 2013 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-24231322

RESUMO

Antibiotics, including members of the tetracycline and fluoroquinolone families, are emerging organic environmental contaminants. Uptake from soil by plants is a means for antibiotics to enter terrestrial food chains. Chemical exchange between plant and the soil/water matrix occurs simultaneously with degradation in the soil/water matrix. In this study, the comparative temporal behaviour of rice (Oryza sativa L.) towards the zwitterionic antibiotics oxytetracycline, chlortetracycline and norfloxacin at initial soil/water concentrations of 10, 20 and 30 µg g(-1) (dry weight) is investigated. This is accomplished within the framework of an activity-based mass-conserving dynamic model. Plant antibiotic concentrations are observed to increase to a maximum then decline. Maximum concentrations in rice are compound-dependent linear functions of initial soil/water concentrations, but the relationships are not related to the compound octan-1-ol/water distribution ratio (DOW). The times required to attain maximal concentrations are independent of initial soil/water levels for a given antibiotic, but again vary between antibiotics and are not related to DOW values. Translocation from root to other tissues is not observed. The magnitudes of Root Concentration Factors (RCFs), the ratio of root and soil/water concentrations, are consistent with significant sorption to soil and consequent relatively low concentrations in interstitial water.


Assuntos
Antibacterianos/metabolismo , Oryza/metabolismo , Poluentes do Solo/metabolismo , Adsorção , Clortetraciclina/metabolismo , Poluição Ambiental , Fluoroquinolonas/metabolismo , Contaminação de Alimentos , Interações Hidrofóbicas e Hidrofílicas , Modelos Teóricos , Norfloxacino/metabolismo , Oxitetraciclina/metabolismo , Raízes de Plantas/metabolismo , Solo , Água/química , Poluentes Químicos da Água/metabolismo
14.
J Theor Biol ; 294: 1-8, 2012 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-22051566

RESUMO

We synthesize the generic properties of ecologically realistic multi-trophic level models and define criteria for ecological realism. We define an "ecospace" in which all ecologically realistic dynamics are confined, and construct "resource rays" that define the resources available to each species at every point in the ecospace. Resource rays for a species are lines from a vertex of maximum resource to the opposite boundary where no resources are available. The growth functions of all biota normally decrease along their resource rays, and change sign from positive to negative. This property prescribes that each species must have a zero isosurface within the ecospace. We illustrate our conditions on a highly cited three trophic level model from population dynamics, showing how to extend this system biologically consistently to a closed ecological system. Our synthesis extends the concept of carrying capacity of population models to explicitly include exhaustion of limiting resources, and so allows for population biology models to be considered as ecologically closed systems with respect to a key limiting nutrient. This approach unifies many theoretical and applied models in a common biogeochemical framework, facilitates better understanding of the key structures of complex ecologies, and suggests strategies for efficient design of experiments.


Assuntos
Ecossistema , Modelos Biológicos , Plâncton/crescimento & desenvolvimento , Animais , Sistemas Ecológicos Fechados , Dinâmica Populacional , Comportamento Predatório
15.
Bull Environ Contam Toxicol ; 85(5): 525-9, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21069277

RESUMO

Analytic expressions for maximum chemical concentration attained in plants, and time this takes for uptake from surrounding soil were derived from a simple two-compartment soil/water-plant model. To illustrate, for the antibiotic norflxacin undergoing first order loss in the soil/water phase with a rate constant of 0.544 days⁻¹, maximum concentration in soybean P(MAX) is predicted to occur after 2.79 days exposure and be independent of initial soil/water concentration SW0 of 52.5 mg kg⁻¹ dry weight. For soybean, the relationship between P(MAX) and SW0 is P(MAX) = 0.047SW0, resulting in predicted maximum levels of 2.20 mg kg⁻¹ dry weight. Modelled plant concentrations agreed well with experimental data (R² = 0.91).


Assuntos
Monitoramento Ambiental/métodos , Compostos Orgânicos/metabolismo , Poluentes do Solo/metabolismo , Poluição Ambiental/estatística & dados numéricos , Previsões , Modelos Químicos , Plantas/metabolismo
16.
J Colloid Interface Sci ; 300(2): 704-12, 2006 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-16777127

RESUMO

Extensive experimental investigation of the wetting processes of fibre/liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment or flow of drops from fibres as airflow velocity increases. A detailed experimental study of the aforementioned processes was conducted using glass filter fibres and H(2)O aerosol, which coalesce on the fibre to form barrel droplets with small contact angles. The droplets were predominantly observed in the Reynolds transition (or unsteady laminar) flow region. The droplet oscillation appears to be induced by the onset of vortexes in the flow field around the droplet as the increasing droplet size increases the Reynolds number. Flow in this region is usually modelled using the classical two-dimensional Karman vortex street, and there exist no 3D equivalents. Therefore to model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and inhibiting such oscillation. The agreement between the model and experimental results is acceptable for both the radial and transverse oscillations.

17.
J Colloid Interface Sci ; 284(1): 245-54, 2005 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-15752809

RESUMO

Extensive experimental investigation of the wetting processes of fibre-liquid systems during air filtration (when drag and gravitational forces are acting) has shown many important features, including droplet extension, oscillatory motion, and detachment of drops from fibres as airflow velocity increases, and also movement or flow of droplets along fibres. A detailed experimental study of the processes was conducted using stainless steel filter fibres and H2O aerosol, which coalesce on the fibre to form clamshell droplets. The droplets were predominantly observed in the Reynolds transition flow region, since this is the region where most of the above features occur. The droplet oscillation is believed to be induced by the onset of the transition from laminar to turbulent flow as the increasing droplet size increases Reynolds number for the flow around the droplet. Two-dimensional flow in this region is usually modelled using the classical Karman vortex street, however there exist no 3D equivalents. Therefore to model such oscillation it was necessary to create a new conceptual model to account for the forces both inducing and preventing such oscillation. The agreement between the model and experimental results is very good for both the radial and transverse oscillations.

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