Bathypelagic Fish Association with the Mid-Atlantic Ridge

The bathypelagic zone, Earth’s largest living space, is essentially boundless in three dimensions for most of its extent, structured only by fluid features (e.g., salinity, temperature) of the seawater itself. However, near certain topographic features this zone intersects the seafloor. The mid-ocean ridge system is by far the largest of these features. Unlike the ecosystems of the continental margins, the mid-ocean ridge systems do not receive terrigenous nutrient inputs. Thus, the deep-water fauna associated with mid-ocean ridges ultimately depend on the generally limited local surface production. Despite this limited surface production, there is evidence that near-ridge demersal fish biomass is increased above the mid-Atlantic Ridge (MAR). Two processes by which organic matter can be transferred to the benthic boundary layer include: 1) sinking of aggregates and the carcasses of larger animals, and 2) vertical migration of living animals. To understand the dynamics of the latter process, deep-pelagic and demersal fishes were studied during the 2004 G.O. Sars Expedition, a field campaign of MAR-ECO. MAR-ECO, a Census of Marine Life project, is an international study of the animals inhabiting the northern Mid-Atlantic. Utilizing multiple technologies the water column (to 3500 m) and benthic realms were sampled. Taxonomic analysis to date has revealed over 300 fish species, with ongoing analysis expected to reveal more species, some new to science. Pelagic sampling collected 207 species, with typical orders dominating. Bottom trawling collected ca. 175 species, with typical demersal families, but also pelagic families occurring in numbers higher than would be expected by contamination alone. Discrete, near-bottom pelagic trawls confirmed this observation. In all, 84 species were caught in both pelagic and bottom trawls, with some species showing enhanced abundances in the near-bottom boundary layer, suggesting that overlap of deep-pelagic and demersal faunas is likely a key process regulating mid-ocean ridge community structure

Threat-sensitive anti-predator defence in precocial wader, the northern lapwing Vanellus vanellus

Birds exhibit various forms of anti-predator behaviours to avoid reproductive failure, with mobbing—observation, approach and usually harassment of a predator—being one of the most commonly observed. Here, we investigate patterns of temporal variation in the mobbing response exhibited by a precocial species, the northern lapwing (Vanellus vanellus). We test whether brood age and self-reliance, or the perceived risk posed by various predators, affect mobbing response of lapwings. We quantified aggressive interactions between lapwings and their natural avian predators and used generalized additive models to test how timing and predator species identity are related to the mobbing response of lapwings. Lapwings diversified mobbing response within the breeding season and depending on predator species. Raven Corvus corax, hooded crow Corvus cornix and harriers evoked the strongest response, while common buzzard Buteo buteo, white stork Ciconia ciconia, black-headed gull Chroicocephalus ridibundus and rook Corvus frugilegus were less frequently attacked. Lapwings increased their mobbing response against raven, common buzzard, white stork and rook throughout the breeding season, while defence against hooded crow, harriers and black-headed gull did not exhibit clear temporal patterns. Mobbing behaviour of lapwings apparently constitutes a flexible anti-predator strategy. The anti-predator response depends on predator species, which may suggest that lapwings distinguish between predator types and match mobbing response to the perceived hazard at different stages of the breeding cycle. We conclude that a single species may exhibit various patterns of temporal variation in anti-predator defence, which may correspond with various hypotheses derived from parental investment theory

Eggs in the Freezer: Energetic Consequences of Nest Site and Nest Design in Arctic Breeding Shorebirds

Birds construct nests for several reasons. For species that breed in the Arctic, the insulative properties of nests are very important. Incubation is costly there and due to an increasing surface to volume ratio, more so in smaller species. Small species are therefore more likely to place their nests in thermally favourable microhabitats and/or to invest more in nest insulation than large species. To test this hypothesis, we examined characteristics of nests of six Arctic breeding shorebird species. All species chose thermally favourable nesting sites in a higher proportion than expected on the basis of habitat availability. Site choice did not differ between species. Depth to frozen ground, measured near the nests, decreased in the course of the season at similar non-species-specific speeds, but this depth increased with species size. Nest cup depth and nest scrape depth (nest cup without the lining) were unrelated to body mass (we applied an exponent of 0.73, to account for metabolic activity of the differently sized species). Cup depth divided by diameter2 was used as a measure of nest cup shape. Small species had narrow and deep nests, while large species had wide shallow nests. The thickness of nest lining varied between 0.1 cm and 7.6 cm, and decreased significantly with body mass. We reconstruct the combined effect of different nest properties on the egg cooling coefficient using previously published quantitative relationships. The predicted effect of nest cup depth and lining depth on heat loss to the frozen ground did not correlate with body mass, but the sheltering effect of nest cup diameter against wind and the effects of lining material on the cooling coefficient increased with body mass. Our results suggest that small arctic shorebirds invest more in the insulation of their nests than large species

Demersal Fish Assemblages and Spatial Diversity Patterns in the Arctic-Atlantic Transition Zone in the Barents Sea

Direct and indirect effects of global warming are expected to be pronounced and fast in the Arctic, impacting terrestrial, freshwater and marine ecosystems. The Barents Sea is a high latitude shelf Sea and a boundary area between arctic and boreal faunas. These faunas are likely to respond differently to changes in climate. In addition, the Barents Sea is highly impacted by fisheries and other human activities. This strong human presence places great demands on scientific investigation and advisory capacity. In order to identify basic community structures against which future climate related or other human induced changes could be evaluated, we analyzed species composition and diversity of demersal fish in the Barents Sea. We found six main assemblages that were separated along depth and temperature gradients. There are indications that climate driven changes have already taken place, since boreal species were found in large parts of the Barents Sea shelf, including also the northern Arctic area. When modelling diversity as a function of depth and temperature, we found that two of the assemblages in the eastern Barents Sea showed lower diversity than expected from their depth and temperature. This is probably caused by low habitat complexity and the distance to the pool of boreal species in the western Barents Sea. In contrast coastal assemblages in south western Barents Sea and along Novaya Zemlya archipelago in the Eastern Barents Sea can be described as diversity “hotspots”; the South-western area had high density of species, abundance and biomass, and here some species have their northern distribution limit, whereas the Novaya Zemlya area has unique fauna of Arctic, coastal demersal fish. (see Information S1 for abstract in Russian)

Northward range extensions of some mesopelagic fishes in the Northeastern Atlantic

In a period mainly from 1995 to 1998, 19 species of southern temperate and subtropical mesopelagic fish have been caught in Norwegian blue whiting, Micromesistius poutassou (Risso), surveys in the Rockall Trough area. Six of the species have not previously been recorded that far north, and the other 13 only rarely in adjacent waters. The species were of the following families: Stomiidae (four species), Microstomatidae (one species), Bathylagidae (one species), Opisthoproctidae (one species), Myctophidae (four species), Evermannellidae (one species), Nemichthyidae (one species), Derichthyidae (two species), Melanonidae (one species), Melamphaidae (one species), and Chiasmodontidae (two species). We discuss whether these range extensions are real and attributable to the recent ocean warming, or only apparent, caused by increased sampling effort

Dispersal and age at first breeding in Norwegian Northern Lapwings (Vanellus vanellus)

Dispersal and age at first breeding were studied in Northern Lapwings from south Norway. In total, 40 adult birds (twomales) and 114 chicks were colour-ringed. Therewere no sex differences in returning rates of birds ringed as chicks (n = 10males and 14 females). Norwere there sex differences in natal and breeding dispersal distances.When sexes were pooled, natal dispersal was longer than breeding dispersal (median distances 160 m and 62 m, respectively). Also, colour-ringed females were more likely than males to breed in their second calendar year. Analyses of a separate data set of regular ring recoveries largely confirmed the relatively low degree of natal dispersal in Norwegian Northern Lapwings. In total, 72% of birds reported during the breeding season (total n = 104) were found within 10 kmfrom their natal site.Dispersal distances observed inNorway are similar to those reported from a comprehensive British study, and from Europe in general

Pruning the Pearlsides: Reconciling Morphology and Molecules in Mesopelagic Fishes (Maurolicus: Sternoptychidae)

The genus Maurolicus comprises extremely abundant vertically-migrating fishes that have considerable biomass in a number of regions worldwide. The genus was generally considered monotypic, with a single species, M. muelleri (Gmelin, 1789), inhabiting all world oceans. Based on differences in combinations of a limited number of morphometric characters, 15 separate species have been proposed, mostly associated with different ocean basins and seamounts. However, due to similarities in external morphology and overlap in ranges of morphometric characteristics, there remains a need for further validation of these species. Here, we present results of a multi-gene analysis, together with morphological data, for five putative Maurolicusspecies from multiple locations in the northern and southern hemispheres. Sampling encompasses described species from the North and South Atlantic, Mediterranean Sea, south-east Indian Ocean and the western South Pacific. Mitochondrial (16S and COI) and nuclear (ITS-2) gene sequences for 120 specimens were used in Maximum Parsimony and Bayesian Inference analyses as well as creation of haplotype networks. Morphological character analyses were based on data from 279 adult individuals. Several clear groupings emerge, conflicting with previously recognised species: (1) a ‘northern’ clade comprising Maurolicus muelleri and M. amethystinopunctatus, (2) a ‘southern’ clade comprising M. australis, M. walvisensis (also M. japonicus) and (3) eastern Equatorial and western North Atlantic M. weitzmani. The southern clade taxa are genetically indistinguishable and not well defined morphologically and present a clear case for synonymisation as M. australis. Synonymisation is also proposed for M. muelleri and M. amethystinopunctatus, with limited morphological variation likely to reflect physical and biological differences experienced north / south of the sub-polar front. Maurolicus weitzmani is clearly differentiated from all other Maurolicus species on both a molecular and morphological basis. Studies of genetic and morphological diversity in Maurolicus will further contribute to the question of ‘what constitutes a species in the open ocean?’, where a complex picture is emerging of both unexpected variation, as well as the unexpectantly absent genetic variation, in cosmopolitan taxa