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O R I G I N A L P A P E R

Oil exposure in a warmer Arctic: potential impacts

on key zooplankton species

Morten Hjorth•Torkel Gissel Nielsen

Received: 17 December 2010 / Accepted: 21 February 2011 / Published online: 11 March 2011 Ó Springer-Verlag 2011

Abstract Oil exploration activities are rapidly increasing in Arctic marine areas with potentially higher risks of oil spills to the environment. Water temperatures in Arctic marine areas are simultaneously increasing as a result of global warming. Potential effects of a combination of increased water temperature and exposure to the PAH pyrene were investigated on fecal pellet and, egg produc-tion and hatching success of two copepod species, Calanus finmarchicus and Calanus glacialis, sampled in Disko Bay, Greenland on 23–25 April 2008. The two species were exposed daily to nominal pyrene concentrations of 0-0.01-0.1-1-10-100 nM at water temperatures of 0.5, 5 and 8°C for 9 and 7 days, respectively. Daily measurements of faecal pellet production, egg production and hatching showed different responses of the two species to the applied stressors. When temperature increased, low con-centrations of pyrene caused a decrease in faecal pellet production by C. finmarchicus, whereas C. glacialis faecal pellet production showed no negative response to pyrene exposure when temperatures increased. Pyrene exposure decreased egg production of C. finmarchicus at all tem-peratures, but the species was more sensitive at 0.5 and 8°C. A lag period of 1 day before egg production began

was prolonged with several days when warmer water was combined with pyrene exposure. Egg production by C. glacialis was only negatively affected by pyrene in a dose-dependent manner at 0.5°C. Hatching success in both species was not affected by pyrene, where increased water temperatures led to a higher hatching success. In conclu-sion, C. glacialis seemed to be the less sensitive of the two species to the stress combination of increased water tem-perature and pyrene exposure. As a consequence of the differential responses of the two species, their competition can be impaired with a consequent impact on energy transfer between trophic levels.

Introduction

Increasing sea and air temperatures (Holland et al. 2008) and reduced sea ice coverage and thickness (Parkinson and Cavalieri 2008) put the arctic under severe environmental stress with serious implications for the marine ecosystem. Interests in exploration of oil and gas reserves in the arctic are increasing (AMAP 2007) as a consequence of the reduced ice cover and pose a threat to the fragile arctic food web (ACIA2005). Increased oil production activities present higher risks of oil spills as well as increased diffuse contamination with harmful effects on the marine ecosys-tem. Petroleum hydrocarbons from oil spills and diffuse leakage, especially the polycyclic aromatic hydrocarbons (PAHs), will enter the marine ecosystems and attach to organic matter in the water (Dachs et al.1996).

Copepods of the genus Calanus dominate the zoo-plankton in Arctic waters during spring (Hirche 1991; Niehoff et al. 2002; Madsen et al. 2008), and many fish (Kaartvedt 2000), seabirds (Karnovsky et al. 2008,2010) and marine mammals (Laidre et al.2007) are dependent on

Communicated by S. A. Poulet. M. Hjorth (&)

Department of Marine Ecology, National Environmental Research Institute, Aarhus University,

Frederiksborgvej 399, 4000 Roskilde, Denmark e-mail: moh@dmu.dk

T. G. Nielsen

National Institute of Aquatic Resources, Section of Oceanecology and Climate,

Technical University of Denmark, Kavalerga˚rden 6, 2920 Charlottenlund, Denmark

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copepod prey. In the coastal waters of West Greenland, three different species of Calanus co-exist. C. hyperboreus and C. glacialis are arctic species while C. finmarchicus is a temperate species associated with Atlantic waters, but it is widely spread along the coast of Greenland (Hirche

1991; Nielsen and Hansen 1995; Arendt et al.2010). The species exhibit large differences in lipid content, where the arctic C. glacialis contain 1.4 lg lipid lg C-1, whereas the temperate C. finmarchicus only have 0.3 lg lipid lg C-1 (Scott et al.2000). Lipids are central as energy storages in Arctic ecosystems and assumed to be the primary reasons for the large stocks of fish, birds and mammals in Arctic waters (Falk-Petersen et al.2006).The simultaneous bind-ing of PAHs in storage lipids and cell membranes may dilute and postpone any effect compared to organisms with lower lipid reserves. PAHs bind strongly to lipids due to their lipophilic nature with values of log Kowranging from 3.4 to 7. Consequently, an effect will occur faster in organisms with low lipid content (Lotufo1998). Modes of action of PAHs in copepods have been suggested to include narcotisation or immobilisation and reduced grazing activity (Jensen et al. 2008). Different tolerance to increasing water temperature and PAH exposure can strengthen the competition between Calanus spp. and thereby the energy source available for the higher trophic levels, both in the pelagic and benthic part of the system. The true arctic species of Calanus (e.g. C. glacialis) are likely to be more sensitive to stress from climate change because of their high affinity to their habitat, and they seem less sensitive to oil contamination (Jensen et al. 2008), which is in opposition to the more climate change resilient C. finmarchicus.

Here, we investigate the combined effects of climate change and oil and gas activities in the Arctic. Specifically, the combined effects of exposure to oil compounds (here represented by the PAH pyrene) and increasing water temperature on faecal pellet production and egg production of two Calanus species in Disko Bay, Greenland, were determined.

Materials and methods Sampling

Sampling of copepods was conducted from 23 to 25 April 2008, in Disko Bay near Qeqertarsuaq, Greenland approximately 1 nautical mile off the coast onboard RV Porsild (Arctic Station, Copenhagen University). The site is a monitoring station which has been used during numerous studies (Nielsen and Hansen 1995; Levinsen et al. 2000; Madsen et al.2001; Juel-Pedersen et al. 2006) (69°150N, 53°330W) with a depth of 300 m (Fig.1). A Niskin 30-l

water bottle was used to fetch water from 100 m, which was filtered through a 0.2-lm filter and used in laboratory exposure experiments and as medium to grow phyto-plankton cultures.

Females of Calanus finmarchicus and C. glacialis were obtained from plankton tows with a WP-2 nylon net (200 lm mesh with a 1-l non-filtering cod-end) from 250 m to the surface. After collection, the content of the cod-end was immediately diluted with surface seawater and kept dark in a thermo box at approximately 0°C, while being transported back to the laboratory. In the laboratory adult female, copepods were sorted out in 1-l glass bottles containing 0.2-lm filtered seawater with 10 individuals of C. glacialis and 15 C. finmarchicus in each. Sorting was done under a dissecting microscope in ice-chilled condi-tions. The bottles were kept dark at their respective expo-sure temperature after sorting and all the time through the experiments.

Exposure experiments

Exposure experiments were performed at three tempera-tures 0.5, 5 and 8°C. Bottles at 0.5°C were kept on ice, bottles at 5 and 8°C were in climate-regulated rooms. At each temperature, copepods were exposed to pyrene in nominal concentrations of 0-0.01-0.1-1-10-100 nM by daily additions of a pyrene solution mixed with the diatom Thalassiosira weissflogii as food algae (15 lg Chl a l-1) with one bottle per combination of temperature and pyrene concentration in a repeated measurement design. Pyrene (EGA Chemie, Germany) was dissolved in acetone (Merck KGaA, Germany). Effects of the solvent on the same variables have previously been tested on Calanus finmar-chicus and C. glacialis at the dilution factor used in this study (10,000) with no harmful effects (Jensen et al.2008). The lowest exposure concentration (0.01 nM pyrene) is within the limits of the provisional ecotoxicological assessment criteria (*2.5 nM) set by the Oslo and Paris Commission, OSPAR (Bignert et al. 2004) and below the criteria for pyrene in seawater set by the USA (Buchmann

1999). In all incubations, copepods were provided excess food from a culture of the diatom T. weissflogii grown in 15-l algal plastic bags filled with 0.2-lm filtered seawater (salinity 33 ± 2) spiked with B1 medium and silicate (Hansen 1989). The cultures were diluted daily and kept in exponential growth phase with a light source (2 pcs. Osram L, 36 W/840, Lumilux Cod white) placed 40 cm from the culture at 20 ± 2°C with constant aeration and a dark:light cyclus of 12:12 h. Ingestion was estimated indirectly by faecal pellet production, and together with egg production, it was monitored daily for 7–9 days by collecting eggs and faecal pellets on a 45-lm filter. Immediately after filtering, the copepods were gently

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transferred to their respective bottles refilled with fresh 0.2-lm filtered surface seawater, and the pyrene-food algae mix was administered. Eggs and faecal pellets were kept in fresh filtered seawater in darkness at 5°C for 4 days, after which the samples were fixated in lugol for later counting under stereo microscope. Hatching success was estimated as the fraction of nauplii of the total number of eggs and nauplii in a sample.

Data analysis

The faecal pellet and egg production were quantified as proxies for grazing and growth daily in every treatment, by counting faecal pellets and eggs and larvae under micro-scope. Both proxies were determined specifically in carbon units as fractions of female carbon content with the unit lg C (lg female C)-1. Specific faecal pellet production (SPP) was calculated using number of pellets, the mean pellet volume for pellets produced at each date, and the pellet volume to carbon conversion factor (Swalethorp et al.

2011). Specific egg production (SEP) was calculated using number of eggs, a mean egg volume for the entire period, and the egg volume to carbon conversion factor (Swale-thorp et al.2011). Table 1lists the conversion factors used in the calculations.

Effects of pyrene exposure and temperature increase on SPP and SEP were analysed by obtaining cumu-lated rates for each pyrene exposure and temperature combination through linear regression. A lag time was

sometimes observed, especially in egg production where rates did not increase above zero until a few days after start. In such cases, rates were predicted using an iter-ative nonlinear model, which fitted two linear regressions to the data. The intercept between the two lines defines the lag phase and the slope of the second line from the end of the lag phase until the end of the experiment was used as the rate estimate. The experimental set-up was a repeated measures design with pyrene concentrations as treatments, temperature as subjects and time as the repeated measures factor (Quinn and Keough 2002). Analyses of variance (ANOVA) with Dunnett’s two-tailed t test as a post hoc test, where pyrene treatments were compared to controls, were used to analyse dif-ferences in SPP and SEP. All calculations were per-formed in SAS 9.1 software.

Fig. 1 Location of sampling site in Disko Bay on the west coast of Greenland

Table 1 Size, carbon and lipid content of adult females of Calanus finmarchicus and C. glacialis and carbon content of eggs and pellets from the two species

C. finmarchicus C. glacialis Length (mm) 2.73 ± 0.15 3.69 ± 0.25 Carbon content (lg C female-1) 109 ± 22 406 ± 177 Total lipid content (lg female-1) 51 ± 26 164 ± 134 Egg carbon (lg C egg-1) 0.21 ± 0.04 0.33 ± 0.06 Pellet carbon (lg C lm-3) 4.3 9 10-8 4.3 9 10-8 From Swalethorp et al. (2011)

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Results

The time of sampling (22nd April 2008) and performance of the experiments (23rd April to 2nd May 2008) coincided with the onset of the spring bloom triggered by the break-up of sea ice. The development and dynamics of the spring bloom and the Calanus community are described else-where (Du¨nweber et al. 2010; Swalethorp et al. 2011). Suffice to say, the copepods were sampled at the time of the highest primary production of the season, and the fit-ness and productivity of C. finmarchicus and C. glacialis should be expected to peak at the beginning and culmina-tion of the spring bloom, respectively (Madsen et al.2008; Swalethorp et al. 2011). On the 22nd of April (date of sampling), water temperature was 2.5°C at 200 m depth decreasing to -1.3°C in the upper 50 m. The upper 50 m had a mean chlorophyll a concentration of 0.94 lg Chl a l-1, and in this strata, half of the total biomass of C. finmarchicus and C. glacialis were found (Swalethorp et al.2011).

Faecal pellet production

Increasing water temperature and pyrene exposure had different effects on the food uptake of the two copepod species. Higher water temperature increased pellet pro-duction in all pyrene treatments. As temperature increased

from 0.5 to 8°C, the average increase in cumulated specific pellet production at the end of the experiment across pyr-ene treatments was 0.80 ± 0.47 and 0.45 ± 0.13 lg C lg C-1 (±SD, N = 6) for C. finmarchicus and C. glacialis, respectively (Fig.2). In control treatments of C. finmarchicus, pellet production was only significantly different between 0.5 and 8°C (Tukeys test F24= 3.54, P = 0.004). Pyrene exposure did not elicit a linear dose-dependent response pattern in any of the species at any temperature. However, exposure to 100 nM pyrene reduced pellet production significantly (Dunnett’s t test t40 = 2.62, P \ 0.0028) in C. finmarchicus at all temper-atures (Fig.2a–c). On the other hand, 0.1 nM exposure led to a significant increase (Dunnett’s t test t40= 2.62, P = 0.02) in specific pellet production at 5°C. Exposure to the lowest pyrene concentrations, 0.01 and 0.1 nM led to significantly (Dunnett’s t test t40 = 2.62, P \ 0.024) lower pellet production of C. finmarchicus at the highest tem-perature (Fig.2c).

Control treatments of C. glacialis were not significantly different between temperatures. Pyrene exposure did not have any significantly negative effect on pellet production of C. glacialis. In contrast, exposure to low pyrene con-centrations increased cumulated pellet production rates at all the investigated temperatures, although not in a dose-dependent pattern. There was a significant increase (Dunnett’s t test t30 = 2.66, P \ 0.0001) in cumulated

a b c

f e

d

Fig. 2 Cumulated specific faecal pellet production (SPP) in C. finmarchicus (a–c) and C. glacialis (d–f) during exposure to six concentrations of pyrene at three temperatures (from left to right: 0.5, 5 and 8°C). Asterisks denote a significant different (P \ 0.05) development from control

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pellet production in C. glacialis exposed to 0.01 nM pyr-ene and 10 nM (Dunnett’s t test t30= 2.66, P \ 0.0014) at all temperatures. Additionally, 1 nM pyrene exposure led to significantly increased (Dunnett’s t test t28= 2.68, P = 0.002) pellet production at 5°C. At 8°C, significant increased pellet production was observed in C. glacialis exposed to 0.1 nM pyrene (Dunnett’s t test t30= 2.66, P = 0.007).

Egg production

The response of cumulated specific egg production in the two species to increased water temperature and pyrene exposure is shown in Fig.3. As temperature increased from 0.5 to 5°C, maximum cumulated egg production by C. finmarchicus in control treatments increased with 44% from 0.09 to 0.13 lg C lg C-1 and with 23% from 5 to 8°C (0.16 lg C lg C-1) (Fig.3a–c). At 0.5°C, C. finmar-chicus reacted to pyrene exposure in a dose-dependent pattern (Fig.3a), where 100 nM pyrene exposure signifi-cantly (Dunnett’s t test t40 = 2.62, P \ 0.001) reduced specific egg production with 63% from 0.08 lg C lg C-1 in control to 0.03 lg C lg C-1. At water temperatures of 5°C, only copepods exposed to 10 nM pyrene decreased egg production significantly (Dunnett’s t test t40= 2.62, P\ 0.003) from 0.13 to 0.08 lg C lg C-1 (38%) com-pared to the control group. In 8°C water, all pyrene exposures except 1 nM led to significantly (Dunnett’s t test

t40 = 2.62, P \ 0.005) reduced egg production in C. finm-archicus (Fig.3c), although not in a dose-dependent pat-tern. A lag period of 1 day was observed at 0.5°C in C. finmarchicus before egg production started (Fig.3a). Pyrene exposure combined with temperature increase prolonged this lag period with several days to a maximum of 5 days at 10 and 100 nM pyrene at 8°C (Fig.3c).

Cumulated egg production of C. glacialis in control treatments was constant or slightly decreasing (0.09–0.11 lg C lg C-1) as water temperature increased (Fig.3d–f). Pyrene exposure did not affect egg production in C. glacialis in the same manner as in C. finmarchicus. At 0.5°C, egg production decreased significantly (Dunnett’s t test t30= 2.66, P \ 0.0007) at all pyrene concentrations, except 100 nM (Fig.3d). In water temperatures of 5 and 8°C, 0.01 and 0.1 nM pyrene concentrations had a signif-icant (Dunnett’s t test t28= 2.68, P \ 0.004) positive effect on egg production of C. glacialis compared to con-trol treatments (Fig.3e–f). Only 10 nM pyrene exposure affected egg production negatively at 5°C. Data from C. glacialis exposed to 100 nM pyrene at 5°C were only obtained until day 5.

Hatching success

Hatching success in both species did not display any sig-nificant changes related to pyrene exposure at any of the three water temperatures. Figure4 displays hatching

a b c

f e

d

Fig. 3 Cumulated specific egg production (SEP) in C. finmarchicus (a–c) and C. glacialis (d–f) during exposure to six concentrations of pyrene at three temperatures (from left to right: 0.5, 5 and 8°C). Asterisks denote a significant different (P \ 0.05) development from control

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success of eggs laid by females exposed to pyrene in var-ious concentrations during 3, 5, 7 and 9 days at the three experimental temperatures. Hatching success did not change significantly with increased exposure time of the females. If all data within each temperature treatment were pooled across pyrene exposure times and concentrations, hatching success was significantly higher in 8°C than in 0.5°C in both species (Fig.5). Eggs from C. finmarchicus

at 0.5°C had a 44 ± 9% (95% confidence limit) hatching success, which increased to 66 ± 9% at 8°C (Tukeys test F130= 3.36, P = 0.005). Similarly, C. glacialis at 0.5°C displayed a hatching success of 58 ± 8%, which rose to 74 ± 8% at 8°C (Tukeys test F104= 3.36, P = 0.01).

Discussion

In a future warmer climate, where access to arctic oil fields gets easier and oil exploration increase, the plankton-based food web may be strongly impacted by oil spills. Here, we document a differentiated response by two key arctic copepod species to a combination of increased water temperature and pyrene exposure. The two species of Calanus showed different responses in food uptake and egg production, which can have implications for the succession and sensitivity of arctic plankton systems in a warmer future. In this study, parallel treatments without food addition were omitted in all pyrene and temperature com-binations, as it has previously been showed that pyrene need to be ingested together with food to have an effect on copepods (Jensen et al.2008).

The effects of a temperature increase alone in this study can be investigated through the response of control treat-ments, where no pyrene exposure took place. An analysis

a b c

f e

d

Fig. 4 Hatching per cent (4 days incubation) of eggs from C. finmarchicus (a–c) and C. glacialis (d–f) exposed to pyrene over 3, 5, 7 and 9 days at three water temperatures

Fig. 5 Hatching data from Fig.4, for each species at the three water temperatures, pooled across pyrene treatments and exposure times

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of variance of these data demonstrated that C. finmarchicus increased food uptake significantly, but not egg production when temperatures were increased from 0.5 to 8°C. Data on C. glacialis showed no significant different responses on food uptake or egg production to temperature increases. When another stressor in the form of exposure to the PAH pyrene is forced on the copepods, the response changes. At the three investigated temperatures, C. finmarchicus decreased food uptake, when exposed to 100 nM pyrene and at the highest temperature (8°C), low concentrations of pyrene also reduced food uptake. In contrast, C. glacialis did not decrease its food uptake significantly when exposed to pyrene, only at higher water temperatures did high pyrene concentrations (100 nM) cause a slight reduction in pellet production (Fig.2f). Even though elevated water temperature increased food uptake in C. finmarchicus, our data suggest its food uptake is more sensitive to a combi-nation of pyrene exposure and temperature increase than C. glacialis. Food uptake by C. finmarchicus was affected by pyrene exposure and the sensitivity increased with increasing temperatures. When temperature increased, low concentration of pyrene was sufficient in causing an effect. Egg production is closely linked to food uptake in this species (Hirche1991), which also was corroborated in the present study. Decreased food uptake in C. finmarchicus after exposure to PAHs has also been reported in a study with crude oil exposure (Jensen and Carroll 2010). Egg production rates were most sensitive to pyrene at the highest temperature in line with the response pattern from pellet production. Pyrene exposure and higher water tem-peratures may inhibit food uptake and consequently reduce egg production. There might be direct effects of pyrene on oogenesis, but they cannot be identified separately in this study. Egg production in C. glacialis is only partly coupled to food uptake (Niehoff et al.2002), as they can start egg production based on lipid energy stores and produce eggs without food access (Hirche1991). Therefore, the lack of response to pyrene exposure observed in food uptake does not necessarily have to be observed in egg production, which also was the case. In water temperatures of 0.5°C, egg production decreased significantly in C. glacialis. At 5 and 8°C, the response to pyrene was not in a dose-depen-dent pattern, as low concentrations of pyrene significantly increased egg production. The reason for this positive reaction to pyrene exposure in low concentrations in war-mer water is unclear, but it is known that slight stress impacts from contaminants can promote positive responses in organisms, a process known as hormesis (Forbes2000). Lipid content of the copepods may be another issue involved. As PAHs enter the organism through food uptake, it is accumulated in lipid stores until metabolised or excreted (Berrojalbiz et al. 2009; Cailleaud et al. 2009). The size of lipid stores can influence how much is

accumulated internally or transferred out of the organism through pellets or eggs. The lack of response in C. glacialis can be linked to its larger lipid content (Table 1). Com-pared to C. finmarchicus, whose low lipid content forces its metabolism to deal with pyrene sooner, C. glacialis may deposit more pyrene in its lipid stores before a threshold level is reached and an effect is triggered.

The percentage of hatched eggs did not show any responses related to pyrene exposure. Jensen et al. (2008) also investigated hatching success in eggs from pyrene-exposed females and found only a decreased hatching in 10 nM pyrene exposed C. finmarchicus. They contribute the results to less uptake of pyrene as a consequence of a reduced grazing activity by the females during the expo-sure, and the eggs investigated were produced from earlier energy reserves. Both causes might be valid here as well, even though but this study included a 24-h acclimatisation period to prevent interference from earlier energy reserves. Madsen et al. (2008) report of unaffected egg production after 6–8 days of starvation in both species sampled at the same study site 3 year previously. Increasing temperatures from 0.5 to 8°C led to a higher hatching success regardless of pyrene exposure level, which adds to the notion that 9 days of pyrene exposure to female Calanus copepods does not affect the hatching of their produced eggs. If pyrene is accumulated in lipids and transferred to eggs, our data do not suggest any effects on hatching from that accumulation. If it has later implications for the hatching larvae, their further development remains to be seen and should be investigated further. A study on the effects of crude oil exposure on feeding and reproduction of C. finmarchicus and C. glacialis from the Barents Sea observed a decrease in hatching success of eggs from C. glacialis (Jensen and Carroll2010), which they to some degree contribute to transfer of PAHs to the eggs.

Some information is available concerning effects of PAH exposure to pelagic copepods (Barata et al. 2005; Bellas and Thor 2007; Hansen et al. 2008; Hjorth and Dahllo¨f2008; Jensen et al.2008; Jensen and Carroll2010). Some effects are believed to arise from narcotisation. Our data in control treatments with no pyrene exposure were within the range of other studies in regard to specific faecal pellet production and specific egg production for the same species in a previous study in the same region and tem-perature regimes (Swalethorp et al.2011). The use of one or more PAHs as a proxy for complex crude oil mixtures, as they would occur in oil spills, is possible as PAHs are considered the most toxic compounds in crude oil (Hylland

2006), and toxic effects of certain PAHs have been shown to be additive (Barata et al.2005). The range of crude oil concentrations (sum of PAHs) used by Jensen and Carroll (2010) was within the concentration range of pyrene in this study, and they observed comparable data. Regardless,

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crude oil exposure is a more realistic scenario, but with inherent difficulties in terms of controllable concentrations, homogeneity in exposure regimes and practical issues.

In association with the reduction in ice cover and war-mer sea water temperature, the Atlantic C. finmarchicus will increase in abundance in the arctic (Hirche and Kos-obokova 2007). If it is more sensitive to stress from oil exposure, oil spill events in a future warmer arctic can potentially have serious effects on the zooplankton com-position and thus also on the ecological function of this trophic level in arctic marine areas subject to climate change and oil spills. Calanus species in the arctic are highly dependent on timing their life cycle with the phy-toplankton spring bloom (Falk-Petersen et al. 2009). Oil spills, which occur at the crucial time of spring blooms, can inflict serious damage on the arctic plankton system not only directly on phytoplankton but also on energy uptake and reproduction of the Calanus species and through them the higher trophic levels.

The energy flow through a food web based on C. finm-archicus will be more impacted by exposure to oil than a food web based on C. glacialis. Consequently, the future planktonic food web in arctic areas like Disko Bay will, in addition to contain less energy, be more vulnerable to impacts from oil spills than the present.

Conclusion

Calanus finmarchicus was the most affected by pyrene exposure and the sensitivity to pyrene increased when water became warmer. Both food uptake and egg produc-tion were affected in contrast to the larger C. glacialis which was not affected in food uptake and only to some degree in egg production. In this species, there was no apparent effect enhancement of higher water temperature and pyrene exposure, which may be partly due to buffering from lipid stores.

As a consequence of the differential responses of the two species to PAH exposure and higher water temperature, the competition between them can be impaired. Temperature stimulates C. finmarchicus more than C. glacialis, but the exposure to oil may eliminate the advantage of higher tem-perature for C. finmarchicus, so the less sensitive C. glacialis may do better in an oil-polluted warmer future. This may in turn impact then transfer of energy between trophic levels, as total copepod biomass will decrease.

Acknowledgments This study was financed by the National Environmental Research Institute (NERI), Carlsberg Foundation, ECOGREEN and the Danish Natural Sciences Research Council. We would like to thank Arctic station in Qeqertarsuaq and the scientific leader Outi Tervo, University of Copenhagen, who provided us with

excellent laboratory facilities and logistical support. At sea, RV Porsild and crew provided a great working platform.

References

ACIA (Arctic Climate Impact Assessment) (2005) Arctic climate impact assessment. Cambridge University Press, Cambridge AMAP (2007) Arctic oil and gas 2007. Arctic monitoring and

assessment programme, Oslo. xiii ? 40 p

Arendt KE, Nielsen TG, Rysgaard S, To¨nnesson K (2010) Differences in plankton community structure along the Godtha˚bsfjord, from the Greenland Ice Sheet to offshore waters. Mar Ecol Prog Ser 401:49–62

Barata C, Calbet A, Saiz E, Ortiz L, Bayona JM (2005) Predicting single and mixture toxicity of petrogenic polycyclic aromatic hydrocarbons to the copepod Oithona davisae. Environ Toxicol Chem 24(11):2992–2999

Bellas J, Thor P (2007) Effects of selected PAHs on reproduction and survival of the calanoid copepod Acartia tonsa. Ecotoxicol 16:465–474

Berrojalbiz N, Lacorte S, Calbet A, Saiz E, Barata C, Dachs J (2009) Accumulation and cycling of polycyclic aromatic hydrocarbons in zooplankton. Environ Sci Technol 43(7):2295–2301 Bignert A, Cossa D, Emmerson R, Fryer R and others (2004) OSPAR/

ICES workshop on the evaluation and update of background reference concentrations (B/RCs) and ecotoxicological assess-ment criteria (EACs) and how these assessassess-ment tools should be used in assessing contaminants in water, sediment, and biota. Workshop, The Hague, 9–13 February 2004. Final Report. OSPAR Commission

Buchmann MF (1999) NOAA screening quick reference tables, NOAA HAZMAT report 99–1, Coastal Protection and Restora-tion Division, NaRestora-tional Oceanic and Atmospheric Administra-tion, Seattle, WA

Cailleaud K, Budzinski H, Le Menach K, Souissi S, Forget-Leray J (2009) Uptake and elimination of hydrophobic organic contam-inants in estuarine copepods: an experimental study. Environ Toxicol Chem 28(2):239–246

Dachs J, Bayona JM, Fowler SW, Miquel J-C, Albaige´s J (1996) Vertical fluxes of polycyclic aromatic hydrocarbons and organo-chloringe compounds in the western Alboran Sea (southwestern Mediterranean). Mar Chem 52:75–86

Du¨nweber M, Swalethorp R, Kjellerup S, Nielsen TG, Others (2010) Succession and fate of the spring diatom bloom in Disko Bay, western Greenland. Mar Ecol Prog Ser 419:11–29

Falk-Petersen S, Timofeev S, Pavlov V, Sargent JR (2006) Climate variability and the effect on arctic food chains. The role of Calanus. In: Orbaek JB et al (eds) Arctic-alpine ecosystems and people in a changing environment. Springer Verlag, Berlin Falk-Petersen S, Mayzaud P, Kattner G, Sargent JR (2009) Lipids and

life strategy of Arctic Calanus. Mar Biol Res 5:18–39 Forbes VE (2000) Is hormesis an evolutionary expectation? Funct

Ecol 14(1):12–24

Hansen PJ (1989) The red tide dinoflagellate Alexandrium tamarense: effect on behaviour and growth of a tintinnid ciliate. Mar Ecol Prog Ser 53:105–116

Hansen BH, Altin D, Vang S-H, Nordtug T, Olsen AJ (2008) Effects of naphtalene on gene transcription in Calanus finmarchicus (Crustacea: Copepoda). Aquat Toxicol 86:157–165

Hirche H-J (1991) Distribution of dominant calanoid copepod species in the Greenland sea during late fall. Polar Biol 11:351–362 Hirche H-J, Kosobokova K (2007) Distribution of Calanus

finmar-chicus in the northern north Atlantic and Arctic ocean–expatri-ation and potential colonizocean–expatri-ation. Deep-Sea Res II 54:2729–2747

(9)

Hjorth M, Dahllo¨f I (2008) A harpacticoid copepod Microsetella spp. from sub-arctic coastal waters and its sensitivity towards the polyaromatic hydrocarbon pyrene. Polar Biol 31(12):1437–1443 Holland DM, Thomas RH, Young BD, Ribergaard MH, Lyberth B (2008) Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters. Nature Geosci 1:659–664

Hylland K (2006) Polycyclic aromatic hydrocarbon (PAH) ecotoxi-cology in marine ecosystems. J Toxicol Environ Health 69:109–123

Jensen LK, Carroll J (2010) Experimental studies of reproduction and feeding for two Arctic-dwelling Calanus species exposed to crude oil. Aquat Biol 10:261–271

Jensen MH, Nielsen TG, Dahllo¨f I (2008) Effects of pyrene on grazing and reproduction of Calanus finmarchicus and Calanus glacialis from Disko Bay, West Greenland. Aquat Toxicol 87:99–107

Juel-Pedersen T, Nielsen TG, Michel C, Møller EF, Others (2006) Sedimentation following the spring bloom in Disko Bay, West Greenland, with special emphasis on the role of copepods. Mar Ecol Prog Ser 314:239–255

Kaartvedt S (2000) Life history of Calanus finmarchicus in the Norwegian Sea in relation to planktivorous fish. ICES J Mar Sci 57:1819–1824

Karnovsky NJ, Hobson KA, Iverson S, Hunt GL Jr (2008) Seasonal changes in diets of seabirds in the North Water Polynya: a multiple-indicator approach. Mar Ecol Prog Ser 357:291–299 Karnovsky NJ, Harding A, Walkusz W, Kwasniewski S, Goszczko I,

others (2010) Foraging distributions of little auks Alle alle across the Greenland Sea: Implications of present and future Arctic climate change. Mar Ecol Prog Ser 415:283–293

Laidre KL, Heide-Jørgensen MP, Nielsen TG (2007) Role of the bowhead whale as a predator in West Greenland. Mar Ecol Prog Ser 346:285–297

Levinsen H, Nielsen TG, Hansen BW (2000) Annual Succession of marine protozoans in the arctic with emphasis on winter dynamics. Mar Ecol Prog Ser 206:119–134

Lotufo GR (1998) Lethal and sublethal toxicity of sediment-associated fluoranthene to benthic copepods: application of the critical-body-residue approach. Aquat Toxicol 44:17–30 Madsen SD, Nielsen TG, Hansen BW (2001) Annual population

development and production by Calanus finmarchicus, C. glacialis and C. hyperboreus in Disko Bay, western Greenland. Mar Biol 139:75–93

Madsen SJ, Nielsen TG, Tervo OM, So¨derkvist J (2008) Importance of feeding for egg production in Calanus finmarchicus and C. glacialis during the Arctic spring. Mar Ecol Prog Ser 353:177–190 Niehoff B, Madsen SD, Hansen BW, Nielsen TG (2002)

Reproduc-tive cycles of three dominant Calanus species in Disko Bay, West Greenland. Mar Biol 140:567–576

Nielsen TG, Hansen BW (1995) Plankton community structure and carbon cycling on the western coast of Greenland during and after the sedimentation of a diatom bloom. Mar Ecol Prog Ser 125:239–257

Parkinson CL, Cavalieri DJ (2008) Arctic sea ice variability and trends, 1979–2006. J Geophys Res 113:C07003

Quinn GP, Keough MJ (2002) Experimental design and data analysis for biologists. Cambridge University Press, Cambridge 573 p Scott CL, Kwasniewski S, Falk-Petersen S, Sargent JR (2000) Lipids

and life strategies of Calanus finnmarchicus, Calanus glacialis and Calanus hyperboreus in late autumn, Kongsfjorden, Sval-bard. Polar Biol 23:510–516

Swalethorp R, Kjellerup S, Du¨nweber M, Nielsen TG, Møller EF, Rysgaard S, Hansen BW (2011) Grazing, production and biochemical evidence of differences in the life strategies of Calanus finmarchicus, C. glacialis and C. hyperboreus in Disko Bay, Western Greenland. Mar Ecol Prog Ser (in press)

Figure

Fig. 1 Location of sampling site in Disko Bay on the west coast of Greenland
Fig. 2 Cumulated specific faecal pellet production (SPP) in C. finmarchicus (a–c) and C
Fig. 3 Cumulated specific egg production (SEP) in C. finmarchicus (a–c) and C. glacialis (d–f) during exposure to six concentrations of pyrene at three temperatures (from left to right: 0.5, 5 and 8°C)
Fig. 4 Hatching per cent (4 days incubation) of eggs from C. finmarchicus (a–c) and C

References

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