Contaminant concentrations in ivory gull (Pagophila eburnea) eggs from Svalbard and the Russian Arctic (2006-2007)

We found high levels of contaminants, in particular organochlorines, in eggs of the ivory gull Pagophila eburnea, a high Arctic seabird species threatened by climate change and contaminants. An 80% decline in the ivory gull breeding population in the Canadian Arctic the last two decades has been documented. Because of the dependence of the ivory gull on sea ice and its high trophic position, suggested environmental threats are climate change and contaminants. The present study investigated contaminant levels (organochlorines, brominated flame retardants, perfluorinated alkyl substances, and mercury) in ivory gull eggs from four colonies in the Norwegian Svalbard) and Russian Arctic (Franz Josef Land and Severnaya Zemlya). The contaminant levels presented here are among the highest reported in Arctic seabird species, and we identify this as an important stressor in a species already at risk due to environmental change.

Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population, link to supplementary material

Dinoflagellates are a major cause of harmful algal blooms, with consequences for coastal marine ecosystem functioning and services. Alexandrium tamarense is one of the most abundant and widespread toxigenic species in the temperate northern and southern hemisphere, and produces paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive compounds may support the success of A. tamarense and its ability to form blooms. Here we investigate the impact of grazing on monoclonal and mixed set-ups of highly (Alex2) and moderately (Alex4) allelochemically active A. tamarense strains and on a non-allelochemically active conspecific (Alex5) by the heterotrophic dinoflagellate Polykrikos kofoidii. While Alex4 and particularly Alex5 were strongly grazed by P. kofoidii when offered alone, both strains grew well in the mixed assemblages (Alex4+Alex5 and Alex2+Alex5). Hence, the allelochemical active strains facilitated growth of the non-active strain by protecting the population as a whole against grazing. Based on our results, we argue that facilitation among clonal lineages within a species may partly explain the high genotypic and phenotypic diversity of Alexandrium populations. Populations of Alexandrium may comprise multiple cooperative traits that act in concert with intraspecific facilitation, and hence promote the success of this notorious harmful algal bloom species.

(Table 1) Egg size, clutch asymmetry, hatch date and breeding success in south polar skua, brown skua and mixed pairs on King George Island

We studied how environmental conditions affect reproduction in sympatric skua species that differ in their reliance on marine resources: the exclusively marine foraging south polar skua Catharacta maccormicki, the terrestrially foraging brown skua C. antarctica lonnbergi and mixed species pairs with an intermediate diet. Egg size, clutch asymmetry and hatching dates varied between species and years without consistent patterns. In the south polar skuas, 12 to 38% of the variation in these parameters was explained by sea surface temperature, sea ice cover and local weather. In mixed species pairs and brown skuas, the influence of environmental factors on variation in clutch asymmetry and hatching date decreased to 10-29%, and no effect on egg size was found. Annual variation in offspring growth performance also differed between species with variable growth in chicks of south polar skuas and mixed species pairs, and almost uniform growth in brown skuas. Additionally, the dependency on oceanographic and climatic factors, especially local wind conditions, decreased from south polar skuas to brown skua chicks. Consistent in all species, offspring were more sensitive to environmental conditions during early stages; during the late chick stage (>33 d) chick growth was almost independent of environmental conditions. The net breeding success could not be predicted by any environmental factor in any skua species, suggesting it may not be a sensitive indicator of environmental conditions. Hence, the sensitivity of skuas to environmental conditions varied between species, with south polar skuas being more sensitive than brown skuas, and between breeding periods, with the egg parameters being more susceptible to oceanographic conditions. However, during offspring development, local climatic conditions became more important. We conclude that future climate change in the Maritime Antarctic will affect reproduction of skuas more strongly through changes in sea ice cover and sea surface temperature (and the resulting alterations to the marine food web) than through local weather conditions.

Tab.1: Tabulation of pinguin population within the Antarctic Peninsula region

Six species of penguins breed on the Antarctic continent, the Antarctic Peninsula, the South Shetland and South Orkney Islands. Their breeding populations within the Antarctic Peninsula, and the South Orkney and South Shetland Is., and estimates of global populations are given. Typical breeding seasons are also presented, but it must be noted that these will vary inter-annually and intra-annually under the influence of factors such as sea-ice extent and ENSO (interannual) and the location of each breeding colony (southerly localities will be later than northerly localities, as their breeding season is "compressed" within the shorter summer). Their foraging strategies (categorized as near-shore or offshore) and typical durations of foraging trips are also tabulated. As with breeding season events, foraging behaviour will vary intra-seasonally and inter-seasonally (in terms of dive duration, dive depth, foraging location, etc). The distribution of known penguin breeding colonies is circum-continental, with Emperor and Adelie penguins predominant on approximately 75 % of the coast, with two major concentrations in the Ross Sea and in Prydz Bay. The third concentration is in the Antarctic Peninsula region, where some of the largest penguin colonies are present. All six species breed within the area (predominantly Chinstrap Penguins), and the Peninsula region has a greater diversity than the remainder ofthe Antarctic with respect to penguins. The distribution at sea of nonbreeding penguins is less cIear. Non-breeding individuals of all six species move throughout the Southern Ocean, and in many cases, to areas well north of the winter pack-ice zone. However, it is not possible to estimate densities of penguins at sea as there are no estimates of non-breeding penguin populations the extent of their travels.

(Table 1) Breeding parameters for 60 male Adélie penguins (Pygoscelis adeliae) at station Dumont d'Urville (Antarctica) depending on treatment (control vs. CORT)

Corticosterone, the main stress hormone in birds, mediates resource allocation, allowing animals to adjust their physiology and behaviour to changes in the environment. Incubation is a time and energy-consuming phase of the avian reproductive cycle. It may be terminated prematurely, when the parents' energy stores are depleted or when environmental conditions are severe. In this study, the effects of experimentally elevated baseline corticosterone levels on the parental investment of incubating male Adelie penguins were investigated. Incubation duration and reproductive success of 60 penguins were recorded. The clutches of some birds were replaced by dummy eggs, which recorded egg temperatures and rotation rates, enabling a detailed investigation of incubation behaviour. Corticosterone levels of treated birds were 2.4-fold higher than those of controls 18 days post treatment. Exogenous corticosterone triggered nest desertion in 61% of the treated birds; consequently reducing reproductive success, indicating that corticosterone can reduce or disrupt parental investment. Regarding egg temperatures, hypothermic events became more frequent and more pronounced in treated birds, before these birds eventually abandoned their nest. The treatment also significantly decreased incubation temperatures by 1.3 °C and lengthened the incubation period by 2.1 days. However, the number of chicks at hatching was similar among successful nests, regardless of treatment. Weather conditions appeared to be particularly important in determining the extent to which corticosterone levels affected the behaviour of penguins, as treated penguins were more sensitive to severe weather conditions. This underlines the importance of considering the interactions of organisms with their environment in studies of animal behaviour and ecophysiology.

Abundance and size composition of ctenophore Mnemiopsis leidyi population in the Caspian Sea on 2001-06-24 to 2001-07-01

Abundance and size distribution of ctenophore Mnemiopsis leidyi in different parts of the Caspian Sea were studied in summer 2001 in relation to environmental conditions. In general, principal differences were found in M. leidyi abundance and population reproduction activity in northern-, middle- and southern Caspian waters. Ctenophore was practically absent in the northern Caspian. In the west of the middle Caspian Sea it penetrated far to the north demonstrating low reproduction activity. In the east the first single comb jellies were pointed out only in the most south of the region. In the warmest and most productive southern part of the Caspian Sea several zones of M. leidyi active breeding were found with total abundance exceeding 6000 #/m**2. Breeding activity and abundance of ctenophores increased here from the east to the west exceeding maximum values along the western coast of the southern Caspian Sea in regions of intensive sprat catching. Dependence of M. leidyi population development on temperature conditions was mentioned. On the base of remote sensed surface temperature, chlorophyll, and suspended mater distribution analysis possible ctenophore settling mechanisms by mesoscale dynamic structures were examined. Practical applications of obtained results are discussed for using effective biological methods to prevent catastrophic consequences of M. leidyi invasion to the Caspian Sea.

(Table 2) Protein and fibre content of important food plants of barnacle geese (Branta leucopsis) in Adventdalen

Goose grazing on arctic tundra vegetation has shown both positive and negative effects on subsequent foraging conditions. To understand the potential of a density-dependent feedback on herbivore population size, the relation between grazing pressure and future foraging conditions is essential. We studied the effect of increasing grazing pressure of barnacle geese (Branta leucopsis) on Spitsbergen. During the establishment of a breeding colony in the period 1992-2004, the proportion of graminoids decreased in the diet of wild geese, while the percentage of mosses increased. Grazing trials with captive geese in an unexploited area showed a similar shift in diet composition. High-quality food plants were depleted within years and over years. Intake rate declined too and as consequence, metabolisable energy intake rate (MEIR) decreased rapidly with increasing grazing pressure. During three successive years of experimental grazing, MEIR decreased at all levels of grazing pressure and declined below minimal energetic requirements when grazing exceeded natural levels of grazing pressure. This suggests that foraging conditions rapidly decline with increasing grazing pressure in these low-productive habitats. The potential for density-dependent feedbacks on local population increase is discussed.

(Table 1) Characteristics of breeding male Adélie penguins (Pygoscelis adeliae) treated with varying degrees of corticosterone, Adélie land, Antarctica

Breeding individuals enter an emergency life-history stage when their body reserves reach a minimum threshold. Consequently, they redirect current activity toward survival, leading to egg abandonment in birds. Corticosterone (CORT) is known to promote this stage. How and to what extent CORT triggers egg abandonment when breeding is associated with prolonged fasting, however, requires further investigation. We manipulated free-living male Adelie penguins with CORT-pellets before their laying period. We then examined their behavioral response with respect to nest abandonment in parallel with their prolactin levels (regulating parental care), and the subsequent effects of treatment on breeding success in relieved birds. Exogenous CORT triggered nest abandonment in 60% of the treated penguins -14 days after treatment and induced a concomitant decline in prolactin levels. Interestingly, prolactin levels in treated penguins that did not abandon their nest were higher at the point of implantation and also after being relieved by females, when compared with abandoning penguins. Among successful birds, the treatment did not affect the number of chicks, nor the brood mass. Our results show the involvement of CORT in the decision-making process regarding egg abandonment in Adelie penguins when incubation is associated with a natural long fast. However, we suggest that CORT alone is not sufficient to trigger nest abandonment but that 1) prolactin levels need to reach a low threshold value, and 2) a rise in proteolysis (i.e. utilization of protein as main energy substrate) seems also to be required.