Impact of Pyrene Exposure during Overwintering of the Arctic Copepod Calanus glacialis.

While ongoing warming and sea ice decline threaten unique Arctic ecosystems, they improve the prospect of exploiting fossil fuels in the seafloor. Arctic Calanus copepods can accumulate oil compounds in the large lipid reserves that enable them to cope with highly seasonal food availability characteristic of the Arctic. While spending a significant part of their lives overwintering at depth, their vulnerability to oil contamination during winter remains unknown. We investigated effects of the hazardous crude oil component pyrene on overwintering Calanus glacialis, a key species in Arctic shelf areas. Females were exposed from December to March and then transferred to clean water and fed until April. We showed that long-term exposure during overwintering reduced survival and lipid mobilization in a dose-dependent manner at concentrations previously considered sublethal. After exposure, strong delayed effects were observed in lipid recovery, fecal pellet, and egg production. We showed that 50% lethal threshold concentrations were at least 300 times lower than expected, and that 50% effect thresholds for pellet and egg production were at least 10 times lower than previously documented. Our study provides novel insights to the effects of oil contamination during winter, which is essential to evaluate ecological impacts of Arctic oil pollution.

Effects of pyrene exposure and temperature on early development of two co-existing Arctic copepods.

Oil exploration is expected to increase in the near future in Western Greenland. At present, effects of exposure to oil compounds on early life-stages of the ecologically important Calanus spp. are unknown. We investigated the effects of the oil compound pyrene, on egg hatching and naupliar development of the calanoid copepods Calanus glacialis and C. finmarchicus, two key species in the Disko Bay, Western Greenland. At low temperature the nauplii of C. glacialis experienced reduced growth when exposed to pyrene, and survival in both species decreased. Naupliar mortality increased with temperature at high pyrene concentration in C. finmarchicus. Both Calanus species were affected by pyrene exposure but C. finmarchicus was more sensitive compared to C. glacialis. Lowered growth rate and increased mortality of the naupliar stages entail reduced recruitment to copepod populations. Exposure to pyrene from an oil spill may reduce the standing stock of Calanus, which can lead to less energy available to higher trophic levels in the Arctic marine food web.

Ecotoxicological mechanisms and models in an impact analysis tool for oil spills.

In an international collaborative effort, an impact analysis tool is being developed to predict the effect of accidental oil spills on recruitment and production of Atlantic cod (Gadus morhua) in the Barents Sea. The tool consisted of three coupled ecological models that describe (1) plankton biomass dynamics, (2) cod larvae growth, and (3) fish stock dynamics. The discussions from a series of workshops are presented in which variables and parameters of the first two ecological models were listed that may be affected by oil-related compounds. In addition, ecotoxicological algorithms are suggested that may be used to quantify such effects and what the challenges and opportunities are for algorithm parameterization. Based on model exercises described in the literature, survival and individual growth of cod larvae, survival and reproduction of zooplankton, and phytoplankton population growth are denoted as variables and parameters from the ecological models that might be affected in case of an oil spill. Because toxicity databases mostly (67%) contain data for freshwater species in temperate environments, parameterization of the ecotoxicological algorithms describing effects on these endpoints in the subarctic marine environment is not straightforward. Therefore, it is proposed that metadata analyses be used to estimate the sensitivity of subarctic marine species from available databases. To perform such analyses and reduce associated uncertainty and variability, mechanistic models of varying complexity, possibly aided by new experimental data, are proposed. Lastly, examples are given of how seasonality in ecosystems may influence chemical effects, in particular in the subarctic environment. Food availability and length of day were identified as important characteristics as these determine nutritional status and phototoxicity, respectively.

Delayed effects of pyrene exposure during overwintering on the Arctic copepod Calanus hyperboreus.

Calanus hyperboreus is the largest copepod and a key species in the Arctic food web. During the spring bloom, C. hyperboreus builds up large lipid reserves, which enable it to survive and produce eggs during overwintering. The ecological effects of oil exposure on overwintering C. hyperboreus are unknown. The present study empirically tested if exposure to the polycyclic aromatic hydrocarbon (PAH) pyrene from crude oil affects the survival, egg production, and hatching success of overwintering C. hyperboreus. We also tested the delayed effects on faecal pellet production and lipid recovery in clean seawater. Direct exposure did not reduce survival and egg production, but reduced hatching success 3-18 times by the end of the exposure period. Remarkably, we documented strong delayed effects of pyrene on faecal pellet production and the recovery of lipid reserves. The current study reveals a high vulnerability of this key species of Arctic zooplankton to oil exposure during winter. Together with our previous study on C. glacialis, we complete the picture of the impact of oil on the largest and most lipid-rich copepod C. hyperboreus, which potentially can have huge ecological consequences for the fragile Arctic marine food web.

Effects of oil spill response technologies on marine microorganisms in the high Arctic.

We studied how exposure to oil spill response technologies affect marine microorganisms during Arctic winter and spring. Microorganisms were exposed to chemically dispersed oil (DISP), in situ burnt oil (ISB), and natural attenuated oil (NATT) in mesocosms from February to May. We subsampled the mesocosms and studied the effects of oil in laboratory incubations as changes in biomass of the major functional groups: bacteria, heterotrophic-nanoflagellates, dinoflagellates, ciliates, pico- and nanophytoplankton, and diatoms over two 14-day periods. In winter, the majority of polycyclic aromatic hydrocarbons (PAHs) remained encapsulated in the ice, and the low concentrations of PAHs in water led to minute changes in biomass of the investigated groups. In spring, however, when the PAHs were partially released from the melting ice, the biomass of many functional groups in DISP and NATT decreased significantly, while the changes in ISB were less pronounced. The overall biomass reduction, as observed in this study, could lead to a disrupted transfer of energy from the primary producers to the higher trophic levels in oil affected areas.

How including ecological realism impacts the assessment of the environmental effect of oil spills at the population level: The application of matrix models for Arctic Calanus species.

For oil spill responses, assessment of the potential environmental exposure and impacts of a spill is crucial. Due to a lack of chronic toxicity data, acute data is used together with precautionary assumptions. The effect on the Arctic keystone (copepod) species Calanus hyperboreus and Calanus glacialis populations is compared using two approaches: a precautionary approach where all exposed individuals die above a defined threshold concentration and a refined (full-dose-response) approach. For this purpose a matrix population model parameterised with data from the literature is used. Population effects of continuous exposures with varying durations were modelled on a range of concentrations. Just above the chronic No Observed Effect Concentration (which is field relevant) the estimated population recovery duration of the precautionary approach was more than 300 times that of the refined approach. With increasing exposure concentration and duration, the effect in the refined approach converges to the maximum effect assumed in the precautionary approach.

Effects of oil spill response technologies on the physiological performance of the Arctic copepod Calanus glacialis.

A mesocosm study with oil in ice was performed in Van Mijenfjorden in Svalbard to compare effects of the oil spill responses (OSR) in situ burning, chemical dispersion and natural attenuation on the physiological performance of the Arctic copepod Calanus glacialis. Seawater collected from the mesocosms in winter and spring was used in laboratory incubation experiments, where effects on fecal pellet production, egg production and hatching success were investigated over a period of 14 days. Polycyclic aromatic hydrocarbon (PAH) seawater concentrations were lowest in winter. Brine channel formation in spring resulted in an 18 times increase in PAH concentration in the chemical dispersion treatment (1.67 µg L-1), and a 3 fold increase in the natural attenuation (0.36 µg L-1) and in situ burning (0.04 µg L-1) treatments. The physiological performance of female C. glacialis was unaffected by the PAH seawater concentrations. However, a higher mortality and deformity of nauplii was observed in the chemical dispersion treatment, highlighting the importance of considering secondary effects on next generation in future environmental risk assessment of OSR. This study shows that during the ice-covered period, chemical dispersion of oil spills leads to higher PAH exposure than natural attenuation and in situ burning, with potential consequences for recruitment of Arctic copepods.

The use of (14)C tracer technique to assess the functional response of zooplankton community grazing to toxic impact.

The use of functional endpoints in risk assessment of pollutants for marine pelagic communities is scarce, especially for the function of zooplankton communities. This work presents a rapid, inexpensive and ecologically relevant technique to assess the effect of toxic compounds on the grazing rates of zooplankton communities. The combination of a (14)C-tracer labelling technique with a fast (< 3 h) and representative sub-sampling and handling makes it possible to measure changes in food uptake of freshly collected natural zooplankton communities in a short-term assay. The methodology is described and its validity is determined by a full account of the fate of isotope tracers (up to 15% taken up by zooplankton). Egg production of Acartia tonsa cultures exposed to DCOI yielded EC(50) values of 118+/-33 nM DCOI after three days, where EC(50) values from grazing of natural zooplankton communities was 136+/-29 nM DCOI, indicating that grazing was the more sensitive variable. Finally the method was tested in a mesocosm experiment designed to evaluate the toxicity of the antifouling compound zinc pyrithion (ZPT) with an EC(50) value of 17 nM ZPT (SD=3.3 nM, n=3). The method was found to be reproducible both at the community (CV=8-39%) and individual level (CV=23-53%), and could detect small changes in response to a toxicant in a natural pelagic system. The use of natural communities in combination with the fast and cost-effective procedure makes this technique a powerful tool in risk assessment, where lack of ecological relevance or reproducible results often results in unwanted high uncertainties.

Towards a renewed research agenda in ecotoxicology.

New concerns about biodiversity, ecosystem services and human health triggered several new regulations increasing the need for sound ecotoxicological risk assessment. The PEER network aims to share its view on the research issues that this challenges. PEER scientists call for an improved biologically relevant exposure assessment. They promote comprehensive effect assessment at several biological levels. Biological traits should be used for Environmental risk assessment (ERA) as promising tools to better understand relationships between structure and functioning of ecosystems. The use of modern high throughput methods could also enhance the amount of data for a better risk assessment. Improved models coping with multiple stressors or biological levels are necessary to answer for a more scientifically based risk assessment. Those methods must be embedded within life cycle analysis or economical models for efficient regulations. Joint research programmes involving humanities with ecological sciences should be developed for a sound risk management.