ALBERT

Description: Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. Maximum aridity and lowest lake level occurred in the early and middle Holocene (8000 to 5500 cal yr B.P.) during a time of low summer insolation. Today, rising levels of Lake Titicaca and wet conditions in Amazonia are correlated with anomalously cold sea-surface temperatures in the northern equatorial Atlantic. Likewise, during the deglacial and Holocene periods, there were several millennial-scale wet phases on the Altiplano and in Amazonia that coincided with anomalously cold periods in the equatorial and high-latitude North Atlantic, such as the Younger Dryas.

Description: Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcusgroup). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.

Description: In vertebrates, genes of the major histocompatibility complex (MHC), with their pronounced polymorphism, potentially represent outstanding examples for the selective advantages of genetic diversity (1). Theoretical models predicted that, within an individual, MHC alleles can be subjected to two opposing selective forces, resulting in an optimal number of genes at intermediate individual MHC diversity (2, 3). Diversifying selection increases heterozygosity and enables wider recognition of pathogens (4). This process is opposed by the need to delete T cells that react with self peptide–MHC combinations (5) from the repertoire, which has been proposed as a possible mechanism constraining expansion of MHC genes. Because too high MHC diversity might delimit T cell diversity, it might also impose limitations on the efficiency of pathogen recognition. However, empirical evidence demonstrating fitness benefits in terms of parasite resistance caused by this type of optimal MHC diversity has been lacking. Therefore, we tested whether three-spined sticklebacks (Gasterosteus aculeatus L.) carrying an intermediate level of individual MHC diversity also displayed the strongest level of resistance against parasite infection. Sticklebacks are particularly suited to test MHC optimality, because MHC class II genotypes can differ markedly in the number of MHC class IIB alleles (6). We caught fish from an outbred population and used these to breed six sibships of immunologically naïve fish (i.e., they had no previous contact to parasites). Immunogenetic diversity ranged from three to nine MHC class IIB alleles found in reverse-transcribed messenger RNA (mRNA) [see (6) for details on genotyping]. The MHC genotypes within these sibships segregated above and below the hypothesized optimal number of ∼5 MHC class IIB alleles, which had previously been estimated in an epidemiological field survey (7). In individual infection treatments, fish from all sibships were simultaneously exposed to three of the most abundant parasite species identified in the field (Fig. 1A) (8). After two rounds of infection, separated by an interval of 8 weeks, we found a significant minimal mean infection rate at an intermediate number of individual MHC class IIB variants [i.e., 5.82 expressed alleles (Fig. 1B)]. This result was also confirmed when sibships were considered separately [i.e., 4.96 alleles (Fig. 1C)] (9). The strong pattern only appeared when infection with all three parasites was accounted for simultaneously. This may not be surprising, because single alleles are expected to correlate with single diseases and multiple alleles can contribute to resistance against several infectious agents (2).

Description: In vertebrates, genes of the major histocompatibility complex (MHC), with their pronounced polymorphism, potentially represent outstanding examples for the selective advantages of genetic diversity (1). Theoretical models predicted that, within an individual, MHC alleles can be subjected to two opposing selective forces, resulting in an optimal number of genes at intermediate individual MHC diversity (2, 3). Diversifying selection increases heterozygosity and enables wider recognition of pathogens (4). This process is opposed by the need to delete T cells that react with self peptide–MHC combinations (5) from the repertoire, which has been proposed as a possible mechanism constraining expansion of MHC genes. Because too high MHC diversity might delimit T cell diversity, it might also impose limitations on the efficiency of pathogen recognition. However, empirical evidence demonstrating fitness benefits in terms of parasite resistance caused by this type of optimal MHC diversity has been lacking. Therefore, we tested whether three-spined sticklebacks (Gasterosteus aculeatus L.) carrying an intermediate level of individual MHC diversity also displayed the strongest level of resistance against parasite infection. Sticklebacks are particularly suited to test MHC optimality, because MHC class II genotypes can differ markedly in the number of MHC class IIB alleles (6). We caught fish from an outbred population and used these to breed six sibships of immunologically naïve fish (i.e., they had no previous contact to parasites). Immunogenetic diversity ranged from three to nine MHC class IIB alleles found in reverse-transcribed messenger RNA (mRNA) [see (6) for details on genotyping]. The MHC genotypes within these sibships segregated above and below the hypothesized optimal number of ∼5 MHC class IIB alleles, which had previously been estimated in an epidemiological field survey (7). In individual infection treatments, fish from all sibships were simultaneously exposed to three of the most abundant parasite species identified in the field (Fig. 1A) (8). After two rounds of infection, separated by an interval of 8 weeks, we found a significant minimal mean infection rate at an intermediate number of individual MHC class IIB variants [i.e., 5.82 expressed alleles (Fig. 1B)]. This result was also confirmed when sibships were considered separately [i.e., 4.96 alleles (Fig. 1C)] (9). The strong pattern only appeared when infection with all three parasites was accounted for simultaneously. This may not be surprising, because single alleles are expected to correlate with single diseases and multiple alleles can contribute to resistance against several infectious agents (2).

Description: Study of Nautilus belauensis i its natural habitat in Palau, West Caroline Islands, shows that growth is slow (0.1 millimeter of shell per day on the average) and decreases as maturity is approached and that individuals may live at least 4 years beyond maturity. Age estimates for seven animals marked and recaptured between 45 and 355 days after release range from 14.5 to 17.2 years. These data indicate that the life-span of Nautilus may exceed 20 years and that its life strategy is very different from that of other living cephalopods.

Description: Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. The oceanic sink accounts for ∼48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO2 to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential.

Description: Large euhedral crystals of calcium carbonate hexahydrate were recovered from a shelf basin of the Bransfield Strait, Antarctic Peninsula, at a water depth of 1950 meters and sub-zero bottom water temperatures. The chemistry, mineralogy, and stable isotope composition of this hydrated calcium carbonate phase, its environment of formation, and its mode of precipitation confirm the properties variously attributed to hypothetical precursors of the glendonites and thereby greatly expand their use in paleoceanographic interpretation.

Description: A tomographic image of the upper mantle beneath central Tibet from INDEPTH data has revealed a subvertical high-velocity zone from ~ 100- to ~ 400- kilometers depth, located approximately south of the Bangong-Nujiang Suture. We interpret this zone to be downwelling Indian mantle lithosphere. This additional lithosphere would account for the total amount of shortening in the Himalayas and Tibet. A consequence of this downwelling would be a deficit of asthenosphere, which should be balanced by an upwelling counterflow, and thus could explain the presence of warm mantle beneath north-central Tibet.

Description: Recent insights into bacterial genome organization and function have improved our understanding of the nature of pathogenic bacteria and their ability to cause disease. It is becoming increasingly clear that the bacterial chromosome constantly undergoes structural changes due to gene acquisition and loss, recombination, and mutational events that have an impact on the pathogenic potential of the bacterium. Even though the bacterial genome includes additional genetic elements, the chromosome represents the most important entity in this context. Here, we will show that various processes of genomic instability have an influence on the many manifestations of infectious disease

Description: Kimberlite eruptions bring exotic rock fragments and minerals, including diamonds, from deep within the mantle up to the surface. Such fragments are rapidly absorbed into the kimberlite magma so their appearance at the surface implies rapid transport from depth. High spatial resolution Ar-Ar age data on phlogopite grains in xenoliths from Malaita in the Solomon Islands, southwest Pacific, and Elovy Island in the Kola Peninsula, Russia, indicate transport times of hours to days depending upon the magma temperature. In addition, the data show that the phlogopite grains preserve Ar-Ar ages recorded at high temperature in the mantle, 700°C above the conventional closure temperature.

Description: The Alpine Iceman provides a unique window into the Neolithic-Copper Age of Europe. We compared the radiogenic (strontium and lead) and stable (oxygen and carbon) isotope composition of the Iceman's teeth and bones, as well as 40Ar/39Ar mica ages from his intestine, to local geology and hydrology, and we inferred his habitat and range from childhood to adult life. The Iceman's origin can be restricted to a few valleys within ∼60 kilometers south(east) of the discovery site. His migration during adulthood is indicated by contrasting isotopic compositions of enamel, bones, and intestinal content. This demonstrates that the Alpine valleys of central Europe were permanently inhabited during the terminal Neolithic.

Description: Measurements of the age difference between coexisting benthic and planktic foraminifera from western equatorial Pacific deep-sea cores suggest that during peak glacial time the radiocarbon age of water at 2-kilometers depth was no greater than that of today. These results make unlikely suggestions that a slowdown in deep-ocean ventilation was responsible for a sizable fraction of the increase of the ratio of carbon-14 (14C) to carbon in the atmosphere and surface ocean during glacial time. Comparison of 14C ages for coexisting wood and planktic foraminifera from the same site suggests that the atmosphere to surface ocean 14C to C ratio difference was not substantially different from today's.

Description: The North Atlantic Oscillation (NAO) dictates climate variability from the eastern seaboard of the United States to Siberia and from the Arctic to the subtropical Atlantic, especially during winter. It strongly affects agricultural yields, water management, fish inventories, and terrestrial ecology. In their Perspective, Hurrell, Kushnir, and Visbeck report recent research into the NAO discussed at an American Geophysical Union Chapman Conference at the end of 2000. Much remains to be learned about the NAO, but it seems increasingly less likely that natural variability is the cause for the recent upward NAO trend.

Description: Overexploitation threatens the future of many large vertebrates. In the ocean, tunas and sea turtles are current conservation concerns because of this intense pressure. The status of most shark species, in contrast, remains uncertain. Using the largest data set in the Northwest Atlantic, we show rapid large declines in large coastal and oceanic shark populations. Scalloped hammerhead, white, and thresher sharks are each estimated to have declined by over 75% in the past 15 years. Closed-area models highlight priority areas for shark conservation, and the need to consider effort reallocation and site selection if marine reserves are to benefit multiple threatened species.

Description: The Redfield ratio [carbon:nitrogen:phosphorus (C:N:P)] of particle flux to the deep ocean is a key factor in marine biogeochemical cycling. Changes in oceanic carbon sequestration have been linked to variations in the Redfield ratio on geological time scales, but this ratio generally is assumed to be constant with time in the modern ocean. However, deep-water Redfield ratios in the northern hemisphere show evidence for temporal trends over the past five decades. The North Atlantic Ocean exhibits a rising N:P ratio, which may be related to increased deposition of atmospheric nitrous oxides from anthropogenic N emissions. In the North Pacific Ocean, increasing C:N and C:P ratios are accompanied by rising remineralization rates, which suggests intensified export production. Stronger export of carbon in this region may be due to enhanced bioavailability of aeolian iron. These findings imply that the biological part of the marine carbon cycle currently is not in steady state.

Description: In the Campeche Knolls, in the southern Gulf of Mexico, lava-like flows of solidified asphalt cover more than 1 square kilometer of the rim of a dissected salt dome at a depth of 3000 meters below sea level. Chemosynthetic tubeworms and bivalves colonize the sea floor near the asphalt, which chilled and contracted after discharge. The site also includes oil seeps, gas hydrate deposits, locally anoxic sediments, and slabs of authigenic carbonate. Asphalt volcanism creates a habitat for chemosynthetic life that may be widespread at great depth in the Gulf of Mexico.

Description: During an almost yearlong period of observations made with a current meter in the fracture zone between the Falkland Islands (Islas Malvinas) and South Georgia, several overflow events were recorded at a depth of 3000 meters carrying cold bottom water from the Scotia Sea into the Argentine Basin. The outflow bursts of Scotia Sea bottom water, a mixing product of Weddell Sea and eastern Pacific bottom water, were associated with typical speeds of more than 28 centimeters per second toward the northwest and characteristic temperatures below 0.6°C. The maximum 24-hour average speed of 65 centimeters per second, together with a temperature of 0.29°C, was encountered on 14 November 1980 at a water depth of 2973 meters, 35 meters above the sea floor.

Description: The last glacial period was far from quiet. During so-called Heinrich events, large armadas of icebergs were shed from the ice sheet that covered much of North America. The tracks of debris left by the melting icebergs can still be seen in sediment cores from the North Atlantic. In their Perspective, Broecker and Hemming report from a recent miniconference that attempted to chart the climatic impacts of these events.

Description: During the Medieval Warm Period (800 to 1200 A.D.), the Vikings colonized Greenland. In his Perspective, Broecker discusses whether this warm period was global or regional in extent. He argues that it is the last in a long series of climate fluctuations in the North Atlantic, that it was likely global, and that the present warming should be attributed in part to such an oscillation, upon which the warming due to greenhouse gases is superimposed.

Description: Two hypotheses have been put forward to explain the large and abrupt climate changes that punctuated glacial time. One attributes such changes to reorganizations of the ocean's thermohaline circulation and the other to changes in tropical atmosphere-ocean dynamics. In an attempt to distinguish between these hypotheses, two lines of evidence are examined. The first involves the timing of the freshwater injections to the northern Atlantic that have been suggested as triggers for the global impacts associated with the Younger Dryas and Heinrich events. The second has to do with evidence for precursory events associated with the Heinrich ice-rafted debris layers in the northern Atlantic and with the abrupt Dansgaard-Oeschger warmings recorded in the Santa Barbara Basin.

Description: We have reconstructed the glacial-age distribution of carbonate ion concentration in the deep waters of the equatorial ocean on the basis of differences in weight between glacial and Holocene foraminifera shells picked from a series of cores spanning a range of water depth on the western Atlantic's Ceara Rise and the western Pacific's Ontong Java Plateau. The results suggest that unlike today's ocean, sizable vertical gradients in the carbonate ion concentration existed in the glacial-age deep ocean. In the equatorial Pacific, the concentration increased with depth, and in the Atlantic, it decreased with depth. In addition, the contrast between the carbonate ion concentration in deep waters produced in the northern Atlantic and deep water in the Pacific appears to have been larger than in today's ocean.

Description: Climate policy needs to address the multidecadal to centennial time scale of climate change. Although the realization of short-term targets is an important first step, to be effective climate policies need to be conceived as long-term programs that will achieve a gradual transition to an essentially emission-free economy on the time scale of a century. This requires a considerably broader spectrum of policy measures than the primarily market-based instruments invoked for shorter term mitigation policies. A successful climate policy must consist of a dual approach focusing on both short-term targets and long-term goals

Description: There was no difference in weight between diploid and triploid landlocked Atlantic salmon (Salmo saiar) measured over a 9-mo period, but triploids were consistently longer (FL) and thus had a lower condition factor than diploids. The gonadosomatic index (GSI) of triploid females was only 7.7% that of diploid females, while the GSI of triploid males was 52% that of diploid males. Triploid ovaries had the external appearance of undeveloped gonads, but every triploid female did in fact produce a small number of oocytes (from 1 to 12, versus several hundred oocytes in each diploid female). Triploid testes were well developed but contained few spermatids and no spermatozoa. Diploid testes, on the other hand, were in advanced stages of spermiogenesis. None of the triploid males reached spermiation.

Description: Nodularia Mertens ex Bornet & Flahault originally established in 1822, has had a total of 28 taxa described. It is restricted in distribution primarily to brackish coastal waters and inland lakes and ponds. In British Columbia (Canada) these lakes and ponds have extreme ranges of salinity (4–400‰) and temperature (0–35 °C). Laboratory studies of 16 isolates indicated maximum growth at 5–10‰, salinity (range 1–60‰), 25–30 °C, pH 10.0–10.5 (range 7.0–10.5) at light intensity of 6000 lx. No preference was shown for dominant anions (Na+, Mg2+) or cations (Cl−, CO32−, S42−). Sheath and akinete characteristics were variable, whereas vegetative cell shape, heterocyst location, and akinete formation were more stable. Investigation of field-collected material, laboratory-grown cultures, and study of herbarium specimens indicate that all the described taxa belong to either N. harveyana [Thwaites] Thuret ex Bornet & Flahault 1886 or N. spumigena Mertens ex Bornet & Flahault 1886. The latter is named the syntype and lectotype material is designated.

Description: The recovery of sagittal fish otoliths and cephalopod beaks from fecal samples is an important source of information about the diets of marine mammals. Nevertheless, diet reconstructions are biased to some extent because of the partial and complete digestion of these prey structures. Although some authors have used correction factors to account for partial digestion of otoliths, none to date have corrected for the number of otoliths and cephalopod beaks that are completely digested, termed number correction factors (NCFs). Data from nine studies of captive pinnipeds show that corrections for the complete digestion of otoliths and cephalopod beaks range from 1.0 to 25.0 in the 28 prey species. Correction factors ranged from 1.0 to 10.0 in cases where seals could exercise by swimming during the experiment. In several species, NCFs vary inversely with prey length. The effect of applying NCFs will depend on the relative proportion of prey species in the diet and the NCFs of these species. Nevertheless, estimates of the species composition of marine mammal diets will benefit from the use of NCFs. Finally, standardization of experimental protocols and attention to the estimation of variability are needed to provide more reliable NCFs.

Description: For goal-directed arm movements, the nervous system generates a sequence of motor commands that bring the arm toward the target. Control of the octopus arm is especially complex because the arm can be moved in any direction, with a virtually infinite number of degrees of freedom. Here we show that arm extensions can be evoked mechanically or electrically in arms whose connection with the brain has been severed. These extensions show kinematic features that are almost identical to normal behavior, suggesting that the basic motor program for voluntary movement is embedded within the neural circuitry of the arm itself. Such peripheral motor programs represent considerable simplification in the motor control of this highly redundant appendage.

Description: Growth modeling in squid has been hampered by a paucity of raw growth data on live individuals. We reared wild juvenile squid Loligo pealeii, for up to 97 days post capture, to determine the form of growth and to test the hypothesis that a 5°C difference in temperature would significantly affect growth rates. Precapture growth rates (the instantaneous relative growth rate or percent increase in body mass per day (IRGR)) of 8-11% were estimated using statolith age data. Laboratory growth rates over a maximum of 97 experimental days fell into two phases in which most L. pealeii grew exponentially, albeit at a slower rate in phase 2. In both phases, the values of IRGR were significantly higher for L. pealeii reared at 20°C than for those reared at 15°C, being respectively, 4.36 and 2.69 in phase 1 and 2.57 and 1.63 in phase 2. This study provides strong evidence of phase-specific temperature sensitivity in squid growth. The IRGR values obtained were used to simulate the growth of squid hatched in nature from May to September in a simple predictive model. The growth simulations indicated that, by the end of phase-1 growth, squid hatched in June and July were two and three times the weight, respectively, at the same age, as squid hatched in May, owing to their exposure to warmer temperatures.

Description: The Gully submarine canyon off eastern Canada has been designated a pilot marine protected area largely because of the northern bottlenose whales (Hyperoodon ampullatus) found there. Studies of this species' diet elsewhere in the North Atlantic Ocean have suggested specialization on the deep-sea squid Gonatus fabricii. We found a high proportion of the congener Gonatus steenstrupi in the stomachs of two bottlenose whales stranded in eastern Canada. In 1997, we collected remote biopsy samples from free-ranging bottlenose whales off Nova Scotia; fatty acids were determined from blubber samples and stable isotopes (carbon and nitrogen) from skin samples. Although fatty-acid stratification throughout the depth of the blubber layer was present (determined from blubber samples of stranded animals), the magnitude of stratification was less pronounced than in many other cetaceans, allowing some qualitative inferences to be made from shallow biopsy samples. Fatty-acid patterns and stable-isotope values from whales were compared with those in samples of G. fabricii from the Norwegian Sea. Blubber fatty acid composition was similar in characteristics to that of adult G. fabricii but was markedly distinct from that of juvenile G. fabricii and other recorded prey species. Nitrogen-isotope values implied that bottlenose whales (mean 15.3‰) and adult G. fabricii (mean 13.7‰) occupy high trophic levels. Overall, the results of these techniques concurred in suggesting that squid of the genus Gonatus may form a major part of the diet of bottlenose whales in the Gully.

Description: Two cohorts of Loligo gahi recruit to the fishery around the Falkland Islands, the first in summer and the second in autumn-winter. We investigated factors affecting recruitment to these cohorts using 13 years of data (1987-1999). The first evidence for density-dependent effects on recruitment in a squid population is reported, with very high spawning stock biomass leading to a reduction in recruitment in both cohorts. October sea surface temperature was negatively correlated with recruitment to the second cohort 6 months later, and a linear model explained 66% of the variance in recruitment strength. A model combining sea surface temperature and spawning stock size explained 77% of the variance. Thus, low October temperatures and moderate stock sizes lead to higher recruitment the following year than high October temperatures and high stock sizes. A strong negative relationship was also found between sea surface temperature in May and the timing of recruitment to the first cohort the following January-February, suggesting that higher temperatures lead to faster development of embryos or paralarvae and earlier recruitment to the fishery. A predictive model of recruitment size and timing should enable better management of L. gahi.

Description: Atlantic climate variability is an important driving force of climate in the surrounding land areas. In his Perspective, Visbeck explores recent advances toward understanding and predicting climate variability in the tropical Atlantic and the North Atlantic, and elucidating the role played by the ocean's circulation.

Description: Bernard, F. 1981. Canadian west coast flying squid experimental fishery. Can. Ind. Re. Fish. Aquat. Sci. 122: 23p. This report covers the experimental drift net fishery for the flying squid Ommastrephes bartramii (Lesuer) on the high seas off the west coast of Vancouver Island in the summer of 1980. Ctaches were commercial, but development of a fishery is not imminent because of a lack of suitable large vesels and shore-based processing facilities. Further constraints are the large amount of manpower required to run gear and process catch and the volatile prices and deman for squid.

Description: Evidence is presented that North Atlantic climate change since 1950 is linked to a progressive warming of tropical sea surface temperatures, especially over the Indian and Pacific Oceans. The ocean changes alter the pattern and magnitude of tropical rainfall and atmospheric heating, the atmospheric response to which includes the spatial structure of the North Atlantic Oscillation (NAO). The slow, tropical ocean warming has thus forced a commensurate trend toward one extreme phase of the NAO during the past half-century.

Description: Due to the recent development of well-integrated surveying techniques of the sea floor, significant improvements were achieved in mapping and describing the morphology and architecture of submarine mass movements. Except for the occurrence of turbidity currents, the aquatic environment (marine and fresh water) experiences the same type of mass failure as that found on land. Submarine mass movements, however, can have run-out distances in excess of 100 km, so their impact on any offshore activity needs to be integrated over a wide area. This great mobility of submarine mass movements is still not very well understood, particularly for cases like the far-reaching debris flows mapped on the Mississippi Fan and the large submarine rock avalanches found around many volcanic islands. A major challenge ahead is the integration of mass movement mechanics in an appropriate evaluation of the hazard so that proper risk assessment methodologies can be developed and implemented for various human activities offshore, including the development of natural resources and the establishment of reliable communication corridors.