Parallel adaptive evolution of Atlantic cod on both sides of the Atlantic Ocean in response to temperature

Despite the enormous economic and ecological importance of marine organisms, the spatial scales of adaptation and biocomplexity remain largely unknown. Yet, the preservation of local stocks that possess adaptive diversity is critical to the long-term maintenance of productive stable fisheries and ecosystems. Here, we document genomic evidence of range-wide adaptive differentiation in a broadcast spawning marine fish, Atlantic cod (Gadus morhua), using a genome survey of single nucleotide polymorphisms. Of 1641 gene-associated polymorphisms examined, 70 (4.2%) tested positive for signatures of selection using a Bayesian approach. We identify a subset of these loci (n = 40) for which allele frequencies show parallel temperature-associated clines (p < 0.001, r² = 0.89) in the eastern and western north Atlantic. Temperature associations were robust to the statistical removal of geographic distance or latitude effects, and contrasted ‘neutral’ loci, which displayed no temperature association. Allele frequencies at temperature-associated loci were significantly correlated, spanned three linkage groups and several were successfully annotated supporting the involvement of multiple independent genes. Our results are consistent with the evolution and/or selective sweep of multiple genes in response to ocean temperature, and support the possibility of a new conservation paradigm for non-model marine organisms based on genomic approaches to resolving functional and adaptive diversity.     

Long-term declining trend of zooplankton biomass in the Tropical Atlantic

We report evidences that the zooplankton biomass in the tropical Atlantic has declined with an almost 10-fold drop from the 1950s to 2000. The results of the multiple regression analysis showed that the decline in zooplankton biomass was positively related to the NAO-index and to phosphate concentration. We also found that the depth of the thermocline has decreased over the period of our investigation. Thus, the decline we report in zooplankton biomass may be related to the combined effect of two phenomena driven by global temperature increase: (1) the widening of the distributional range of tropical species due to the expansion of the ‘tropical belt’ and (2) a decrease in primary production resulting from the thinning of the thermocline. The decline of zooplankton biomass we report suggests that global warming of the ocean may be altering tropical food webs, and through them, it may also indirectly impact tropical oceans biogeochemical cycles. Handling editor: S. I. Dodson     

Diversity of isopods (Crustacea): new data from the Arctic and Atlantic Oceans

New data on the diversity pattern of isopods (Crustacea) from the northern most part of the North Atlantic and the Arctic Oceans is presented. The pattern of diversity with depth is similar at depths <1000m, but differs considerably below about 1000m. In the Arctic the diversity of isopods (expressed both as numbers of species per sled and expected number of species) increased with increased depth to a maximum at depths of about 320 to 1100m, but then declined towards deeper waters. There was a significant increase in numbers per sled and in the expected number of species with increased depth in the northernmost part of the North Atlantic Ocean. Additionally, changes occurred in the relative composition of the shallow and deep water fauna, with asellote isopods being relatively larger part of the isopod fauna in the Arctic than in the northern most part of the North Atlantic. This indicates major faunistic changes occurring at the Greenland-Iceland-Faeroe Ridge, possibly caused by rapid changes in the temperature. Furthermore, that the low diversity of the Arctic deep-sea is a regional phenomenon, and not a part of a large scale latitudinal pattern in the North Atlantic.     

Spatial distributions of copepod genera along the Atlantic Meridional Transect

The distribution of copepod taxa at a basin scale was analysed using three Atlantic transects (U.K. – Malvinas 1997, Malvinas – U.K. 1997, and South Africa – U.K. 1998). Integrated 200 m to surface zooplankton samples were taken daily, using WP2 nets (200-m mesh). The zooplankton were size-fractionated and sub-samples taken for carbon analysis. The remainder of the samples was preserved for taxonomic analysis of copepod genera. Multidimensional scaling (MDS) was used to identify zoogeographic regions from the copepod genera. Seven regions were identified: northern temperate, northern subtropical, equatorial, southern tropical, southern sub-tropical, southern temperate and Benguela upwelling. Analysis of similarity showed that most regions were significantly different from each other except: northern temperate and southern temperate, northern temperate and southern subtropical, and northern subtropical and southern subtropical. The genera significant in determining the regions were identified. These regions were compared to other schemes of biological and hydrographic areas. The MDS also showed that the copepod composition in the tropical and subtropical regions was less variable than the temperate and Benguela stations. Latitudinal trends in diversity and size were also investigated. Copepod genera showed a reduction in richness at higher latitudes. Copepod size did not show any substantial or consistent change with latitude along these transects, as demonstrated by both the numerical abundances in each size category, and the carbon biomass per individual. The proportion in each size fraction was quite uniform over the transect.     

Cetacean sightings near South Georgia islands,South Atlantic Ocean

The information about cetacean occurrence around the Island of South Georgia is scarce. With the main goal of gathering information on a feeding ground of humpback whales (Megaptera novaeangliae) that winter in Brazilian waters, we conducted an expedition to South Georgia. We present here the information regarding cetacean sightings during the expedition. From 28 January to 2 March, 2006 we carried out 13 research cruises, covering 700 nautical miles and 110 h of observation. We registered 10 sightings, in 7 h of ad libitum observations, of the following species: Megaptera novaeangliae, Eubalaena australis, Balaenoptera physalus, Mesoplodon layardii, Orcinus orca and Lagenorhynchus cruciger. We present data on location, depth, group size, structure, and behavior for this geographical area of essential importance for cetacean conservation.     

Lower Devonian Chonetoidean Brachiopods From Bac Bo, North Viêt Nam

Recent investigations of the Lower Devonian fauna of North Viêt Nam have provided abundant invertebrates, among which chonetoidean brachiopods are especially common. Their good preservation has allowed the revision of eight of the nine species described in the literature. The North Vietnamese chonetoidean fauna is mainly characterized by the diversity of representatives of the Family Strophochonetidae (strophochonetines and parachonetines), which includes nine species. Three new genera, namely TulynetesBacbonetesCyrtochonetes, and two species, namely Bacbonetes janvieriChlupacina nariensis, are described. The occurrence of Perichonetes mirabilisChlupacina nariensis, and plicanoplitid brachiopods establishes the extension of the south-west China pelagic Nandan Facies to eastern Bac Bo. The Lower Devonian chonetoidean fauna of eastern Bac Bo is closely allied to that of south-west and central China belonging to the Yangtzé microcontinent, whilst the fauna of western Bac Bo appears to be more closely allied with that of the northern Gondwanaland margin. One new additional chonetoidean genus, Orthochonetes, is described in a note added to the systematic section.     

Brachiopods of the family Linoproductidae from the Kasimovian Stage of the Moscow Region

Brachiopods from the Kasimovian Stage of the Moscow Region that for more than 70 years were referred to the genus Linoproductus (family Linoproductidae) are revised and redescribed. New characters connected with the ornamentation and inner structure of the dorsal valve are used for the first time in the analysis of the taxonomic structure of the group. Six species from three genera are described; four of them are new: one species of Linispinus Lazarev, 2006, three species of Linipalus Lazarev, 2007, and two species of Sublinoproductus gen. nov. The new genus is considered to be transitional between the genera Linispinus and Linoproductus.     

Brachiopods from the Jurassic (Callovian) of Hamakhtesh Hagadol (Kurnub Anticline), Southern Israel

The Callovian Zohar and Matmor formations in the Negev, southern Israel, consisting of marls, shales and limestones, have yielded 13 brachiopod species (2 rhynchonellids, 11 terebratulids), referred to 12 genera, of which one genus and five species are new: Apatecosia inornata, Bihenithyris mediocostata, Digonella boylani sp. nov., Dissoria bretti sp. nov., Burmirhynchia jirbaensis, Kutchithyris landeri sp. nov., Pleuraloma triangulatum, Polyplectella debriani gen. et sp. nov., Ptyctothyris daghaniensis, Somalirhynchia africana, Striithyris saudiarabica, S. telemi sp. nov., and Zeilleria sp. The brachiopods described herein from Hamakhtesh Hagadol (Kurnub Anticline) comprise a fauna located at the northernmost part of the Indo-African Faunal Realm within the Jurassic Ethiopian Province.     

Climate-driven range expansion of a critically endangered top predator in northeast Atlantic waters

Global climate change is driving rapid distribution shifts in marine ecosystems; these are well established for lower trophic levels, but are harder to quantify for migratory top predators. By analysing a 25-year sightings-based dataset, we found evidence for rapid northwards range expansion of the critically endangered Balearic shearwater Puffinus mauretanicus in northeast Atlantic waters. A 0.6 degrees C sea surface temperature increase in the mid-1990s is interpreted as an underlying controlling factor, while simultaneous northward shifts of plankton and prey fish species suggests a strong bottom-up control. Our results have important conservation implications and provide new evidence for climate-driven regime shift in Atlantic ecosystems.     

Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic

Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.     

Allozyme differentiation within and between red drum (Sciaenops ocellatus) from the Gulf of Mexico and Atlantic Ocean

Nine polymorphic nuclear-gene (allozyme) loci were surveyed among 491 red drum ( Sciaenops ocellatus ) sampled in 1988 and 1989 from nearshore localities in the northern Gulf of Mexico (Gulf) and the Atlantic coast of the southeastern United States (Atlantic). Data were combined with those from a previous study to generate a data set of 762 individuals representing 11 sample localities in the Gulf and 175 individuals representing five sample localities in the Atlantic. The combined data set included individuals from the 1986 and 1987 year classes and permitted rigorous testing of both temporal and spatial genetic heterogeneity. Average heterozygosity-per-locus values (estimated using 33 assumed monomorphic loci) were 0·048 (Gulf red drum) and 0·046 (Atlantic red drum). Tests of heterogeneity in allele frequencies between year classes at individual localities and across regions (Gulf and Atlantic) were non-significant. Tests of spatial (geographic) heterogeneity indicated that red drum are weakly subdivided: genetically-differentiated subpopulations occur in the northern Gulf and along the south-eastern Atlantic coast. Genetic data were consistent with the hypothesis that red drum within the Gulf and along the Atlantic coast comprise singie subpopulalions. Genetic differences between Gulf and Atlantic red drum seem likeiy to stem from historical or recent interactions between dispersal and impediments to gene flow.     

基于贝叶斯Schaefer模型的阿根廷滑柔鱼资源评估与管理

利用基于贝叶斯统计方法的Schaefer模型对西南大西洋阿根廷滑柔鱼资源量进行评估,并对评估结果进行风险分析.结果表明:正态分布方案和基准方案两个模型参数的预测值及估算的生物学参考点接近,但均大于对数正态分布方案.3种方案下,2001-2010年的捕捞死亡率都远低于限制参考点F0.1,2001-2010年的渔获量也小于最大可持续产量(MSY),表明西南大西洋阿根廷滑柔鱼资源目前处于良好开发状况,没有遭受过度捕捞.决策分析表明,在相同的收获率情况下,对数正态分布方案得到的2025年资源量最低、资源崩溃的概率最大.3种方案下2025年渔获量最大时的收获率均为0.6,但是若将管理策略定为收获率0.6,则2025年以后资源量存在一定风险,因此较为保守的管理策略应将收获率控制在0.4左右,渔获量在55万t左右.     

Variation in spatial distribution of juvenile loggerhead turtles in the eastern Atlantic and western Mediterranean Sea

Loggerhead sea turtles (Caretta caretta) originating from the Western Atlantic carry out one of the largest marine migrations, reaching the eastern Atlantic and Mediterranean Sea. It has been proposed that this transatlantic journey is simply a consequence of drifting, with the lack of a target destination and a passive dispersal with oceanic currents. This predicts that the size of the source populations and geographic distance to the feeding grounds should play important roles in defining stock composition in the eastern Atlantic and Mediterranean Sea. Under this scenario, near pelagic stocks would have no genetic structure, and would be composed of similar cohorts from regional rookeries. To address this question, we sampled individuals from one important eastern Atlantic feeding ground, the Canary Islands, and sequenced a fragment of the mitochondrial DNA control region. We compared the composition of this feeding stock with published data of other proximal areas: Madeira, Azores and Andalusia. “Rookery-centric” mixed stock analysis showed that the distribution of loggerhead sea turtles along the eastern Atlantic feeding grounds was in latitudinal accordance to their natal origin: loggerhead turtles from Florida were significantly more abundant in Azores (30%) than in Canary Islands (13%), while those from Mexico had a poor representation in Azores (13%) but were more prevalent in Canary Islands (34%). Also, genetic stability in temporal and size analyses of the Canary Island aggregation was found, showing a long period of residency. These results indicate a non-random distribution of loggerhead juveniles in oceanic foraging grounds. We discuss possible explanations to this latitudinal variation.     

Cyclic changes in Turonian to Coniacian planktic foraminiferal assemblages from the tropical Atlantic Ocean

Abundance patterns of planktic and benthic foraminifera from a tropical Atlantic drill site (Ocean Drilling Program Site 1259, Demerara Rise, Suriname margin) display a pronounced 400 kyr cyclicity, uninterrupted throughout our  87.8–92 Ma record, between two clearly distinguishable assemblages: (1) a pelagic foraminifer fauna, which represents a deep oxygen minimum zone, and (2) another assemblage representing a shallow oxygen minimum zone where the foraminifer fauna is dominated by a higher diversity population of mostly small clavate and biserial species common in epicontinental seas. The cyclic changes in the long eccentricity band (400 kyr) between these two assemblages are proposed to reflect changes in the mean latitudinal position of the Intertropical Convergence Zone (ITCZ). Associated fluctuations in precipitation and trade wind strength may have influenced the upwelling regime at Demerara Rise leading to the observed cyclicity of planktic foraminiferal assemblages. The severe Turonian to Coniacian paleoclimatic and paleoceanographic changes in the Atlantic Ocean (e.g., gateway opening, cooling, and glaciation), however, seem to have no influence on the composition of tropical planktic foraminiferal faunas. There is no apparent relationship between foraminifer abundances and a major deflection in the stable isotope record interpreted elsewhere as a sign of the growth and decay of a large polar ice sheet.     

Links between viruses and prokaryotes throughout the water column along a North Atlantic latitudinal transect

Viruses are an abundant, diverse and dynamic component of marine ecosystems and have a key role in the biogeochemical processes of the ocean by controlling prokaryotic and phytoplankton abundance and diversity. However, most of the studies on virus–prokaryote interactions in marine environments have been performed in nearshore waters. To assess potential variations in the relation between viruses and prokaryotes in different oceanographic provinces, we determined viral and prokaryotic abundance and production throughout the water column along a latitudinal transect in the North Atlantic. Depth-related trends in prokaryotic and viral abundance (both decreasing by one order of magnitude from epi- to abyssopelagic waters), and prokaryotic production (decreasing by three orders of magnitude) were observed along the latitudinal transect. The virus-to-prokaryote ratio (VPR) increased from ∼19 in epipelagic to ∼53 in the bathy- and abyssopelagic waters. Although the lytic viral production decreased significantly with depth, the lysogenic viral production did not vary with depth. In bathypelagic waters, pronounced differences in prokaryotic and viral abundance were found among different oceanic provinces with lower leucine incorporation rates and higher VPRs in the North Atlantic Gyre province than in the provinces further north and south. The percentage of lysogeny increased from subpolar regions toward the more oligotrophic lower latitudes. Based on the observed trends over this latitudinal transect, we conclude that the viral–host interactions significantly change among different oceanic provinces in response to changes in the biotic and abiotic variables.