The Ligurian Sea is one of the most attractive areas for cetaceans in the Mediterranean Sea, and is now included in a Marine Protected Area, the Pelagos Sanctuary. Despite a lower species diversity than in other parts of the world, because of their abundance, cetaceans are thought to represent significant consumers in this ecosystem. Surveys were conducted within the Pelagos Sanctuary from 2001 to 2004. Densities of five species: striped dolphin (Stenella coeruleoalba); fin whale (Balaenoptera physalus); sperm whale (Physeter macrocephalus); long-finned pilot whale (Globicephala melas); and Risso’s dolphin (Grampus griseus), were estimated and converted to biomass. Total biomass density of cetaceans in the Ligurian Sea was estimated as 93kg km-2 (CV=28%) in winter (October to March) and 509kg km-2 (CV=16%) in summer (April to September). Daily predation rates by cetaceans were estimated as 2.9kg km-2 d-1 in winter, increasing to 10.4kg km-2 d-1 in summer, corresponding to a total annual ingestion of 2.4t km-2 y-1. The annual primary production required for cetaceans was estimated to be 12.6gC m-2 y-1, corresponding to 6- 15% of the net primary production known for this area. Estimated cetacean predation on fish was similar to reported fisheries landings, nevertheless, management of artisanal fisheries and accurate quantification of the resources they exploit will be necessary for the responsible management of fisheries in this Mediterranean Marine Protected Area.

Seabird and marine mammal at-sea distribution in the western Bering Sea and along the eastern Kamtchatka (Kamtsjatka) Peninsula was determined during 114 transect counts, lasting 30 min each, in September 2018. A total of 58000 seabirds were tallied, i.e. a mean value of 510 per count. The most abundant species was short-tailed shearwater: 43250 individuals representing 74% of the total. Fulmar and kittiwake represented 13% and 8% of the total. Important geographical differences were noted, concerning both the number of seabird species and their abundance. The following species were tallied mainly in the northern zone (North of 60°N): fulmar (light morphs), short-tailed shearwater, Vega (herring) gull and horned puffin. In the southern zone, including Commander (Komandorski) Islands, observed species included fulmar (dark morphs), pelagic cormorant, glaucous-winged gull, red-legged kittiwake and black guillemot. The vast majority of the 100 cetaceans and 40 pinnipeds were tallied in the southern area, mainly porpoises, killer whale and humpback whale, and Largha (spotted) seal. Citation: Joiris C R. Seabird and marine mammal at-sea distribution in the western Bering Sea and along the eastern Kamtchatka Peninsula. Adv Polar Sci, 2021, 32(1): 42-49, doi: 10.13679/j.advps.2020.0035

During the ARK-XXIII/3 expedition of icebreaking RV Polarstern in the high Arctic Ocean（partim north of 73°N） from 25 August to 10 October 2008, 550 transect counts lasting 30 min were devoted to seabird and marine mammal counts from the bridge. In the whole area, the three most numerous species, kittiwake Rissa tridactyla, fulmar Fulmarus glacialis and Brünnich’s guillemot Uria lomvia represented 90% of the total of 12000 individuals registered, followed by ivory gull Pagophila eburnea, black guillemot Cepphus grylle and Ross’ s gull Rodostethia rosea. Four geographical zones were recognized on the basis of number of species and density. Both were especially low in the deeper areas（mean depth of 3000 m）, both ice-free and heavily ice-covered: 0.3 birds per 30 min count belonging to three and four species respectively. The most numerous species was kittiwake with 0.25 per count（50 individuals） in the ice-covered area. Pinniped numbers were very low as well, the most numerous of the four species tallied being 20 harp seals Phoca groenlandica and 10 ringed seal Pusa hispida. Seven polar bears Ursus maritimus were encountered. These observations were basically confirmed during 12 helicopter flights lasting one hour each with very low numbers: 50 kittiwakes and 13 harp seals, almost none in the ice-covered deep zone. A comparison between data obtained from ship and from helicopter seems however to reflect the importance of seabird followers including for long distances. The only cetaceans were two adult belugas Delphinapterus leucas tallied from helicopter.

The main aims of our long-term study on the quantitative at-sea distribution of the “upper trophic levels”—seabirds and marine mammals—in both polar areas are to identify and quantify the primary mechanisms influencing species distribution, as well as to detect possible temporal and spatial evolutions. During the Arctic circumpolar navigation on board icebreaking RV Polarstern in autumn (ARK-XXIII/3), 840 half-hour transect counts were devoted to the study of the at-sea distribution of seabirds and marine mammals from 12 August to 17 October 2008. High concentrations of kittiwakes Rissa tridactyla in adult summer plumage were tallied on and around a few icebergs off the southwest Greenland coast: close to 14,000 on three medium size icebergs on 15 and 16 August, and fewer on a small iceberg on 18 August, between 59°N and 70°N. These observations represented by far the majority (70%) of all kittiwakes encountered during the expedition. A possible interpretation is that these numbers, high in comparison with the local breeding population, are due to an influx of new kittiwakes in autumn, e.g. coming from more southern breeding populations in Europe. On the other hand, icebergs are known to attract actively feeding seabirds and/or marine mammals in both polar areas.

Our long-term study on the quantitative at-sea distribution of the upper trophic levels—seabirds and marine mammals—in polar ecosystems aims at quantifying the factors influencing their distribution as well as detecting possible spatial and temporal evolutions, with special attention to hydrography and to global climate changes. During the PS75 (ANT-XXVI/3) expedition of icebreaking RV Polarstern in February–March 2010, 6660 seabirds belonging to 11 identified species were recorded in the Amundsen Sea Embayment and Pine Island Bay during 760 half-hour transect counts. The most numerous species were by far Antarctic petrel Thalassoica antarctica, Adélie penguin Pygoscelis adeliae and snow petrel Pagodroma nivea representing together more than 80% of the total for the whole expedition (n = 5475). Substantial seabird hotspots were concentrated on three icebergs, representing 44% of all observations: 85% of the Antarctic petrels and 40% of the snow petrels. Moreover, 35 Cape petrels Daption capense capense were noted in the immediate surrounding of another iceberg (33% of the total). The highest overall counts were tallied on two icebergs: 250 Antarctic petrels and 500 snow petrels on the first one, and 1000 Antarctic petrels on the second. These hotspots seem to be typical for autumn situations and thus probably reflect the existence of pre-migratory gatherings following the breeding season. The consequences of these high local concentrations and thus the heterogeneity and non-normal distribution of the data are discussed, calculating mean values, standard deviation and density have very questionable value.

This article is part of our long-term study on the quantitative at-sea distribution of the marine "upper trophic levels"—seabirds and marine mammals—in polar ecosystems, aiming at quantifying the factors influencing their distribution as well as detecting possible spatial and temporal changes, with special attention to hydrography and to global climate changes. During an expedition of icebreaking RV Polarstern in February 2010, along the North–South transect between New Zealand and the Ross Gyre, off the Ross Sea, 3200 seabirds belonging to 22 identified pelagic species were recorded during 338 half-hour transect counts. Four major hotspots were identified. These were in Sub-tropical Water off New Zealand（up to 300 birds per count）, and at the main Southern Ocean fronts: the Sub-Antarctic Front（up to 240 per count）, the Antarctic Front（up to 150 per count） and the Polar Front（up to 200 per count）, representing the vast majority of recorded seabirds. The most numerous species in the three frontal zones were: prions—mainly slender-billed Pachyptila belcheri—and Salvin’s albatross Thalassarche [cauta]salvini. The eight more abundant species represented 2650 birds, i.e. more than 80% of the total. A random forest clustering method identified four groups of seabird species occupying similar oceanographic niches.

The distribution, abundance, and species assemblage of top predators - seabirds and cetaceans - can be correlated to water masses as defined by hydrological parameters. In comparison to other oceans, information about the structuring effects of water masses on top predators in the Atlantic Ocean is limited. The present study aims 1) to provide baseline distributional data of top predators for future comparisons, for instance in the course of climate change, and 2) to test how water masses and seasons affect distributional patterns of seabirds and cetaceans in the temperate and tropical Atlantic. During four trans-equatorial expeditions of the RV Polarstern between 2011 and 2014, at-sea observation data of seabirds, cetaceans and other megafauna were collected. Counts of top predators were generally low in the surveyed regions. Statistical analyses for the eight most abundant seabird species and the pooled number of cetaceans revealed water masses and seasons to account for differences in counts and thus also distribution. In most cases, borders between water masses were not very distinct due to gradual changes in surface water properties. Thus, top predator counts were correlated to water masses but, in contrast to polar waters, not strongly linked to borders between water masses. Additional factors, e.g. distance to locally productive areas (upwelling), competition effects, and seabird associations to prey-accumulating subsurface predators may be similarly important in shaping distributional patterns of top predators in the tropical and temperate Atlantic, but could not be specifically tested for here.

The at-sea distribution of top predators, seabirds and marine mammals, was determined in the high Arctic pack ice on board the icebreaker RV Polarstern in July to September 2014. In total, 1,620 transect counts were realised, lasting 30 min each. The five most numerous seabird species represented 74% of the total of 15,150 individuals registered: kittiwake Rissa tridactyla, fulmar Fulmarus glacialis, puffin Fratercula arctica, Ross's gull Rhodostethia rosea, and little auk Alle alle. Eight cetacean species were tallied for a total of 330 individuals, mainly white-beaked dolphin Lagenorhynchus albirostris and fin whale Balaenoptera physalus. Five pinniped species were represented by a total of 55 individuals and the polar bear Ursus maritimus was represented by 12 individuals. Four main geographical zones were identified: from Tromsø to the outer marginal ice zone (OMIZ), the Arctic pack ice (close pack ice, CPI), the end of Lomonosov Ridge off Siberia, and the route off Siberia and northern Norway. Important differences were detected between zones, both in species composition and in individual abundance. Low numbers of species and high proportion of individuals for some of them can be considered to reflect very low biodiversity. Numbers encountered in zones 2 to 4 were very low in comparison with other European Arctic seas. The observed differences showed strong patterns.

The ivory gull Pagophila eburnea is an Arctic seabird species whose distribution is tightly coupled to the availability of sea ice. During the last decades, strong declines have been reported for breeding colonies in Canada and Greenland, which are usually located on nunataks or remote coastal islands. Here, we report the observation of a colony of ivory gulls breeding on a gravel-covered iceberg 70 km off Northeast Greenland in August 2014. It concerned approximately 60 adults, including two ringed individuals, and many chicks. This represents an unusual breeding site for the species, to be compared with a few cases of colonies on gravel-covered sea ice. Breeding on an offshore iceberg may be advantageous since it provides ultimate protection from predators. Furthermore, the proximity to the productive North East Water polynya may have been attractive to these gulls. As a consequence of this and previous observations, colony surveys should not solely focus on inland and coastal breeding habitats, but should be extended towards the ocean.

During the PS75 expedition of ice-breaking RV Polarstern in the Amundsen Sea, in February–March 2010, we studied the at-sea quantitative distribution of the “upper trophic levels,” seabirds and marine mammals. In the Amundsen Sea Embayment, 14,200 pinnipeds belonging to four species were recorded (2100 during 670 half-hour transect counts from the bridge and 12,100 during 50 h of helicopter flight). Crabeater seal Lobodon carcinophaga represented more than 97 % of the total. Two types of major aggregations of crabeaters were noted: on the one hand, very large groups hauled out on the pack ice, composed mainly of adults/bachelors and very few calves. On the other hand, swimming pods of calves were accompanied by one or two leading adults around icebergs. Our interpretation is that, after the beginning of the reproduction period with trios (cow, calf and future father) scattered on pack ice, such pods can be considered the last step of the breeding cycle.

Hydrological parameters influence the distribution of top predators - seabirds and marine mammals. In high latitudes, for example, distinct changes between water masses are often characterized by enhanced biological productivity which lead to accumulations of prey and corresponding high abundances of top predators. For tropical waters, information on distributional patterns of top predators, which may be determined by abiotic and biotic factors, is limited. The present study, thus, aims 1) to provide baseline distributional data for future comparisons, for example with respect to climate change, and 2) to test how water masses and their boundaries affect distributional patterns of seabirds in the eastern temperate and tropical Atlantic Ocean. During four trans-equatorial expeditions of RV Polarstern from 2011 to 2014, data of seabird and marine mammal distributions were acquired. Half-hour transect counts were conducted continuously from the vessel’s bridge without width limitation during daylight and travelling speed of the vessel, while environmental data (e.g. temperature and salinity) were continuously recorded by Polarstern’s navigation system. In general, abundances of top predators in temperate and tropical regions were low when compared to polar regions. A mixed effects modelling approach on the eight most abundant seabird species revealed differences in their abundances to be related to hydrological zones and seasons. In most cases, the borders between water masses and distributional ranges of seabirds were not very distinct due to gradual changes in surface water properties. Seabird abundances, therefore, were correlated to water masses but, in contrast to polar waters, not strongly linked to borders between water masses. Further factors, e.g. distance to local production areas (upwelling) and interspecific competition effects, may be similarly important in shaping the seabird’s distributional patterns in the tropical and temperate Atlantic, but were not assessed in the present study. In the context of predicted climatic changes, a further monitoring of avian top predators is essential, particularly in order to gain a better understanding about their distributional patterns and potential changes in abundance and geographical distribution.

Our long-term study on top predator (seabirds and marine mammals) distribution in polar marine ecosystems aims at detecting possible temporal and spatial population changes, especially in the context of global changes in temperature and ice cover. Quantitative data on the seabird distribution were collected in the northern Greenland Sea and Fram Strait onboard the icebreaker RV Polarstern between 1988 and 2014, applying 30-min transect counts from the bridge, without width limitation (n = 7320). A drastic decrease in numbers by a factor of seven was detected for the ivory gull Pagophila eburnea from 2007 on. These data confirm the decrease of ivory gull previously detected in North Canada and North Greenland, leading to the conclusion that the species is "endangered" or "near threatened". These changes are discussed in relation to the decreasing Arctic pack ice coverage leading to the opening of the Northwest and Northeast Passages in 2007, at the time the year with the lowest ice coverage ever recorded. On the other hand, the decrease was even stronger for Ross's gull Rhodostethia rosea after 1993, apparently reflecting changes in migratory habits. The third high Arctic gull, Sabine's gull Xema sabini, was only tallied in very low numbers, without any clear temporal evolution in numbers.

We investigated the role of hydrological features, such as water masses, fronts, eddies, and sea ice, in affecting the distribution of upper trophic level species in the Scotia Sea region during autumn. On board RV Polarstern, we performed 365 30-min strip transects recording seabirds and marine mammals along the North Scotia Ridge and the South Sandwich Trench in March—April 2013. Among the 7 identified cetacean species recorded, the humpback whale Megaptera novaeangliae was the most abundant baleen whale（40 individuals）, and noteworthy were sightings of six southern right whales Eubalaena australis. Pinnipeds（3 species, 1650 individuals） were dominated by Antarctic fur seal Arctocephalus gazella（99%）, and seabirds（36 species, 18900 individuals） by Antarctic prion Pachyptila desolata（~50%）. The distribution of these top predators was highly patchy with the majority of observations concentrated in a few counts. This heterogeneity is likely a result of prey availability, and we discuss how hydrological features may have caused the patchiness.

The at-sea summertime distribution of marine mammals between South Africa and Antarctica was determined along eight transects surveyed between December 2007 and January 2012. During 1930 30-minute transect counts, 1390 marine mammal individuals were attributed to 19 species: eight toothed whales ( Odontoceti ), six pinnipeds, and five baleen whales ( Mysticeti ). An additional two toothed-whale species were encountered ‘out of effort’. The four most numerous species accounted for 85% of the total number of individuals encountered: crabeater seal ( Lobodon carcinophagus ), humpback whale ( Megaptera novaeangliae ), Antarctic Minke whale ( Balaenoptera bonaerensis ) and fin whale ( B. physalus ). The distribution of these species was related to oceanographic features, such as water masses and fronts, pack ice and ice edge: These differences were statistically highly significant. Biodiversity was compared with other polar marine ecosystems. Citation: Joiris C R, Humphries G R W, Broyer A D. Summer distribution of marine mammals encountered along transects between South Africa and Antarctica during 2007–2012 in relation to oceanographic features. Adv Polar Sci, 2015, 26: 265-273, doi: 10.13679/j.advps.2015.4.00265

The distribution at sea of upper trophic levels—seabirds and marine mammals—is depending on their food availability: high concentrations reflect high prey abundance and thus high biological production. Polar marine ecosystems are characterized by low biodiversity and high biological patchiness. The distribution of predators, as a consequence, shows a similar patchiness. During two expeditions of icebreaking RV Polarstern in June–July 2011, biodiversity in the arctic marine zone north of 70°N was very low, with low numbers of species: 20 seabirds, eight cetaceans, five pinnipeds and polar bear. Moreover, a few species accounted for the majority in numbers: four bird species for 95 % of the total of 23,000 seabirds recorded during 700 transect counts: fulmar Fulmarus glacialis, kittiwake Rissa tridactyla, Brünnich’s guillemot Uria lomvia and little auk Alle alle. Among the marine mammals, 250 fin whales Balaenoptera physalus accounted for 80 % of the identified large cetaceans, 270 white-beaked dolphin Lagenorhynchus albirostris for 100 % of the small cetaceans and 180 harp seals Pagophilus groenlandica for 80 % of the identified pinnipeds. Their quantitative distribution was depending on water masses and oceanic fronts, large cetaceans—mainly fin whales—showing an important aggregation on the shelf slope off western Spitsbergen, as well as little auks and Brünnich’s guillemots. So that this zone, shelf slope and front of mixed Arctic/Atlantic Waters, showed unusually high seabird and cetacean concentrations. Seasonal factors possibly influencing their distribution are addressed.

The main aim of our long-term study on the at-sea distribution of the upper trophic levels in polar marine ecosystems is to deepen the understanding of the basic mechanisms affecting their distribution, i.e. hydrological factors such as water masses and fronts, pack ice and ice edge, eddies. A second goal consists in detecting spatial and temporal changes, with special attention to global climate changes, as well as possible consequences of (krill) fisheries. Seabirds and marine mammals were recorded during an autumn expedition of icebreaking RV Polarstern between Punta Arenas and the South Shetland Islands, Antarctica in March/ April 2012. During a total of 333 half-an-hour transect counts without width limitation, 113,500 seabirds were encountered, belonging to 40 species. The vast majority were southern fulmars and grey-headed albatross around the South Shetland Islands, with 76,800 and 7,000 individuals, respectively. Fin whale was by far the most abundant cetacean with 300 identified individuals in the same area, of which 100 in one count. These exceptional concentrations of fin whale seem to reflect an autumn pre-migration feeding aggregation. For most species, the majority was concentrated in very few counts, reflecting a very high patchiness and, as upper trophic levels, an important prey availability—mainly krill, nekton and small fish. Low biodiversity was reflected by both the low number of species and the fact that a few species represent the vast majority in numbers. It is suggested that the area deserves future biological studies, especially in autumn, and a special protection management.

The first aim of our long-term study on the at-sea distribution of the upper trophic levels-seabirds and marine mammals-in polar marine ecosystems is to identify the main factors affecting their distribution: water masses and pack ice, fronts and ice edge as defined on the basis of water temperature, salinity and ice overage. In this study, seabird at-sea distribution was determined in the south-eastern Atlantic Ocean in summer along four return transects between Cape Town, South Africa, and Queen Maud Land, Antarctica: two on board icebreaking MS Ivan Papanin and two on board icebreaking RV Polarstern between December 2007 and January 2012. During a total of 1,930 half-an-hour transect counts devoted to seabird recording, 69,000 individuals were encountered, belonging to 57 species (mean: 36 individuals per count, all species and expeditions pooled). In comparison, the adjacent Weddell Sea shows a lower seabird biodiversity (30 species and 150 individuals per count) than in the area covered by this study. European Arctic seas reflect an intermediate biodiversity, with 30 species and 60 individuals per count; the major difference is observed in closed pack ice, almost empty in the Arctic but showing a very high biomass in the Antarctic. On the other hand, following the same route in different years allowed to compare results: density and abundance were found to be homogenous and reproducible between years for some species, while very important patchiness was detected for others, causing large heterogeneities and differences between expeditions.

Molluscs (particularly bivalves) and fish are usually proposed as good bioindicators for environmental contamination of marine ecosystems. Different steps can be recognized when assessing such contamination. The first approach consists of comparing stable residue concentrations determined in various environments or different periods. In this chapter, this is illustrated for heavy metals in bivalves from Africa. For some of them, species differences could be detected making comparison difficult: such data can only be used for comparing orders of magnitude. More detailed discussions need the data to be first corrected (normalized) as a function of the main factor influencing accumulation, which means that the transfer, excretion and accumulation mechanisms have first to be identified and understood. Such factors vary, however, with the type of residues, mainly in their liposolubility, and also with the biota concerned: age, lipid content, sex, weight, etc. The importance of this step, as well as the difficulty of coming to clear conclusions, are illustrated for heavy metals, with emphasis on the non-essential ones—mainly mercury—in bivalves. The special case of mercury contamination of the sardine in the Mediterranean Sea is also presented. Finally, the importance of speciation and detoxification as well as the "biomass effect" of phytoplankton are discussed.