Smaller fish species in a warm and oxygen-poor Humboldt Current system

Climate change is expected to result in smaller fish size, but the influence of fishing has made it difficult to substantiate the theorized link between size and ocean warming and deoxygenation. We reconstructed the fish community and oceanographic conditions of the most recent global warm period (last interglacial; 130 to 116 thousand years before present) by using sediments from the northern Humboldt Current system off the coast of Peru, a hotspot of small pelagic fish productivity. In contrast to the present-day anchovy-dominated state, the last interglacial was characterized by considerably smaller (mesopelagic and goby-like) fishes and very low anchovy abundance. These small fish species are more difficult to harvest and are less palatable than anchovies, indicating that our rapidly warming world poses a threat to the global fish supply.

Fossil leaf wax hydrogen isotopes reveal variability of Atlantic and Mediterranean climate forcing on the southeast Iberian Peninsula between 6000 to 3000 cal. BP

Many recently published papers have investigated the spatial and temporal manifestation of the 4.2 ka BP climate event at regional and global scales. However, questions with regard to the potential drivers of the associated climate change remain open. Here, we investigate the interaction between Atlantic and Mediterranean climate forcing on the south-eastern Iberian Peninsula during the mid- to late Holocene using compound-specific hydrogen isotopes from fossil leaf waxes preserved in marine sediments. Variability of hydrogen isotope values in the study area is primarily related to changes in the precipitation source and indicates three phases of increased Mediterranean sourced precipitation from 5450 to 5350 cal. BP, from 5150 to 4300 cal. BP including a short-term interruption around 4800 cal. BP, and from 3400 to 3000 cal. BP interrupted around 3200 cal. BP. These phases are in good agreement with times of prevailing positive modes of the North Atlantic Oscillation (NAO) and reduced storm activity in the Western Mediterranean suggesting that the NAO was the dominant modulator of relative variability in precipitation sources. However, as previously suggested other modes such as the Western Mediterranean Oscillation (WeMO) may have altered this overall relationship. In this regard, a decrease in Mediterranean moisture source coincident with a rapid reduction in warm season precipitation during the 4.2 ka BP event at the south-eastern Iberian Peninsula might have been related to negative WeMO conditions.

An oceanic perspective on Greenland's recent freshwater discharge since 1850

Instrumental data evidence an accelerating freshwater release from Arctic sea ice export and the Greenland Ice Sheet over the past three decades causing cooling and freshening in the subpolar North Atlantic region. However, evaluating the observed acceleration on a historical oceanic and climatic perspective remains challenging given the short available instrumental time series. Here we provide a marine perspective on the freshwater releases to the ocean since 1850 as reflected in the northern limb of the Subpolar Gyre. Our reconstructions suggest that the recent acceleration tracks back to the 1940s/50s and is unprecedented since 1850. The melting, initiated by the 1920s natural rise in solar irradiance, accelerated in response to a combined effect of natural and anthropogenic forcing factors. We find that Greenland’s freshwater discharge has contributed to a nutrient-driven fertilization of the upper ocean and consequently increased the marine primary productivity since the 1940s/50s.

Climate induced human demographic and cultural change in northern Europe during the mid-Holocene

The transition from hunter-gatherer-fisher groups to agrarian societies is arguably the most significant change in human prehistory. In the European plain there is evidence for fully developed agrarian societies by 7,500 cal. yr BP, yet a well-established agrarian society does not appear in the north until 6,000 cal. yr BP for unknown reasons. Here we show a sudden increase in summer temperature at 6,000 cal. yr BP in northern Europe using a well-dated, high resolution record of sea surface temperature (SST) from the Baltic Sea. This temperature rise resulted in hypoxic conditions across the entire Baltic sea as revealed by multiple sedimentary records and supported by marine ecosystem modeling. Comparison with summed probability distributions of radiocarbon dates from archaeological sites indicate that this temperature rise coincided with both the introduction of farming, and a dramatic population increase. The evidence supports the hypothesis that the boundary of farming rapidly extended north at 6,000 cal. yr BP because terrestrial conditions in a previously marginal region improved.

Pteropods are excellent recorders of surface temperature and carbonate ion concentration

Pteropods are among the first responders to ocean acidification and warming, but have not yet been widely explored as carriers of marine paleoenvironmental signals. In order to characterize the stable isotopic composition of aragonitic pteropod shells and their variation in response to climate change parameters, such as seawater temperature, pteropod shells (Heliconoides inflatus) were collected along a latitudinal transect in the Atlantic Ocean (31° N to 38° S). Comparison of shell oxygen isotopic composition to depth changes in the calculated aragonite equilibrium oxygen isotope values implies shallow calcification depths for H. inflatus (75 m). This species is therefore a good potential proxy carrier for past variations in surface ocean properties. Furthermore, we identified pteropod shells to be excellent recorders of climate change, as carbonate ion concentration and temperature in the upper water column have dominant influences on pteropod shell carbon and oxygen isotopic composition. These results, in combination with a broad distribution and high abundance, make the pteropod species studied here, H. inflatus, a promising new proxy carrier in paleoceanography.

155,000 Years of West African Monsoon and Ocean Thermal Evolution

A detailed reconstruction of West African monsoon hydrology over the past 155,000 years suggests a close linkage to northern high-latitude climate oscillations. Ba/Ca ratio and oxygen isotope composition of planktonic foraminifera in a marine sediment core from the Gulf of Guinea, in the eastern equatorial Atlantic (EEA), reveal centennial-scale variations of riverine freshwater input that are synchronous with northern high-latitude stadials and interstadials of the penultimate interglacial and the last deglaciation. EEA Mg/Ca-based sea surface temperatures (SSTs) were decoupled from northern high-latitude millennial-scale fluctuation and primarily responded to changes in atmospheric greenhouse gases and low-latitude solar insolation. The onset of enhanced monsoon precipitation lags behind the changes in EEA SSTs by up to 7000 years during glacial-interglacial transitions. This study demonstrates that the stadial-interstadial and deglacial climate instability of the northern high latitudes exerts dominant control on the West African monsoon dynamics through an atmospheric linkage.

Climatic controls on central African hydrology during the past 20,000 years

Past hydrological changes in Africa have been linked to various climatic processes, depending on region and timescale. Long-term precipitation changes in the regions of northern and southern Africa influenced by the monsoons are thought to have been governed by precessional variations in summer insolation. Conversely, short-term precipitation changes in the northern African tropics have been linked to North Atlantic sea surface temperature anomalies, affecting the northward extension of the Intertropical Convergence Zone and its associated rainbelt. Our knowledge of large-scale hydrological changes in equatorial Africa and their forcing factors is, however, limited. Here we analyse the isotopic composition of terrigenous plant lipids, extracted from a marine sediment core close to the Congo River mouth, in order to reconstruct past central African rainfall variations and compare this record to sea surface temperature changes in the South Atlantic Ocean. We find that central African precipitation during the past 20,000 years was mainly controlled by the difference in sea surface temperatures between the tropics and subtropics of the South Atlantic Ocean, whereas we find no evidence that changes in the position of the Intertropical Convergence Zone had a significant influence on the overall moisture availability in central Africa. We conclude that changes in ocean circulation, and hence sea surface temperature patterns, were important in modulating atmospheric moisture transport onto the central African continent.

Vigorous exchange between the Indian and Atlantic oceans at the end of the past five glacial periods

The magnitude of heat and salt transfer between the Indian and Atlantic oceans through 'Agulhas leakage' is considered important for balancing the global thermohaline circulation. Increases or reductions of this leakage lead to strengthening or weakening of the Atlantic meridional overturning and associated variation of North Atlantic Deep Water formation. Here we show that modern Agulhas waters, which migrate into the south Atlantic Ocean in the form of an Agulhas ring, contain a characteristic assemblage of planktic foraminifera. We use this assemblage as a modern analogue to investigate the Agulhas leakage history over the past 550,000 years from a sediment record in the Cape basin. Our reconstruction indicates that Indian-Atlantic water exchange was highly variable: enhanced during present and past interglacials and largely reduced during glacial intervals. Coherent variability of Agulhas leakage with northern summer insolation suggests a teleconnection to the monsoon system. The onset of increased Agulhas leakage during late glacial conditions took place when glacial ice volume was maximal, suggesting a crucial role for Agulhas leakage in glacial terminations, timing of interhemispheric climate change and the resulting resumption of the Atlantic meridional overturning circulation.

Nursing disease in mink: clinical and postmortem findings

One hundred fifty lactating mink on one ranch in southern Ontario were monitored over the lactation period in 1989 for evidence of clinical disease, and serial blood samples were collected for biochemical analysis. Antemortem blood samples were collected and necropsies performed on the 17 females that developed nursing disease and on 17 controls matched to the same stage of lactation and on ten nonlactating controls. Twenty-two additional nursing disease cases were selected from seven ranches in the following year and processed similarly. The clinical signs typically observed in affected females were sudden onset lethargy and anorexia followed by dehydration, ataxia, and a reluctance to move. The major clinical-pathologic findings were a marked increase in serum osmolality and total protein, urea nitrogen, creatinine, phosphorus, glucose, and potassium concentrations and a decrease in sodium and chloride concentration. In addition, the animals were acidotic, there was a reduction in the urine specific gravity, and the hemogram was consistent with a stress response. Emaciation and dehydration were the only pathologic changes consistently present in cases of nursing disease and not in controls. In almost all cases, bacteria were not cultured from the liver, spleen, and mammary gland, but Campylobacter jejuni was cultured from the intestinal contents of 15/17 affected mink and 2/5 controls. Aleutian disease virus antibody was not present in any of the affected mink. Lipid vacuoles in hepatocytes and renal tubular epithelium, hypertrophy of cells in the adrenal cortex, and pulmonary congestion and atelectasis were present in both diseased females and controls, as were various sporadic inflammatory lesions. Nursing disease may result from energy depletion due to lactation. All lactating females are affected by this process; clinical disease reflects the terminal physiologic decompensation of the most susceptible individuals.

Mortality in mink kits from birth to weaning

In 1988, a necropsy survey of the pattern and major causes of mortality in mink kits from birth to weaning was undertaken. The overall preweaning mortality rate was 20%. Mortalities occurring within the first three days after birth accounted for 91% of submissions, and 78% of the kits in this age group had no lesions or bacterial isolates. The average weight of kits which died within one day of birth (7.9 g) was significantly lower than the average birthweight of healthy kits (10.7 g). In kits under four days of age and with lesions, the most common diagnoses were dystocia (12%), systemic infection (4%), anasarca (2%), and congenital defects (1%). In unweaned kits four days of age or older, the most common diagnoses were systemic infection (19%), external trauma (6%), dystocia (5%), and cervical adenitis (2%).

A survey of the causes of mortality in adult mink, with emphasis on the lactation period

A study of the pattern and relative frequency of diseases in adult female mink during the lactation period was undertaken. All adult females that died between parturition (April/May) and July 1, 1990, from 48 farms in southern Ontario were selected for study, and the cause of death was determined by gross necropsy. In addition, the cause of death was determined by gross necropsy for all adults and weaned kits that died on one farm between April 1988 and March 1989.The mortality rate among farms in the 1990 study, for adult females during the lactation period, ranged from 0.2% to 10.1%, with a median of 1.9%. Nursing disease (56%) was the most common diagnosis, followed by mastitis (11%), metritis (8%), and dystocia (7%). Escherichia coli and Staphylococcus spp. were the most frequent isolates from the cases of mastitis. In the 1988/1989 study, the mortality rate was highest from May to July, with a large increase in June as a result of nursing disease.

A descriptive study of mortality at the Kortright Waterfowl Park: 1982-1986

A five year survey of mortality in an Ontario waterfowl park was conducted. The highest mortality rate was in birds under seven weeks of age, with infectious disease most frequently diagnosed. In older birds, amyloidosis and gout were most common. Associations were found between the presence of amyloid and the diagnoses of gout, enteritis, and arthritis. Specific data collection requirements for studies of this type, and the difficulties involved, are outlined. Recommendations for increasing productivity, including the implementation of sanitation programs, and improvements to the record-keeping system, are made.

Clinical use of oral verapamil in chronic and paroxysmal atrial fibrillation

We evaluated the effectiveness of oral verapamil therapy for control of ventricular rate in digitalized patients with atrial fibrillation (AF) with three clinical problems: chronic AF with rapid rate at rest (four patients), chronic AF with accelerated rate during modest exercise (five patients), and rapid rates during paroxysmal AF (four patients). Patients in the first two categories were evaluated both by open-label dosage titration and by a randomized, double-blind, cross-over protocol. In chronic AF with rapid rate of rest, there was a significant reduction in resting heart rate (from 125 +/- 7 to 87 +/- 14, P less than 0.01) and in peak exercise heart rate (from 162 +/- 33 to 126 +/- 25, P less than 0.01). In chronic AF with rapid rate during exercise, there was also a significant decrease in resting heart rate (from 90 +/- 7 to 66 +/- 4, P less than 0.01) and in peak exercise heart rate (from 126 +/- 19 to 101 +/- 15, P less than 0.01). These effects continued during longterm follow-up of one to 12 months (mean seven months). In patients with paroxysmal AF, verapamil slowed the ventricular response from 16- +/- 24 to 72 +/- 4 P less than 0.01) with only some amelioration of symptoms. Therapy was well tolerated despite a high prevalence (seven of 13 patients) of radiographic cardiomegaly (cardiothoracic ratio greater than 0.55). We conclude that verapamil is a safe and useful drug for control of ventricular rate in digitalized patients with chronic and paroxysmal AF.

Asymptomatic idiopathic syndrome of prolonged Q-T interval in a 45-year-old woman. Ventricular tachyarrhythmias precipitated by hypokalemia and therapy with amitriptyline and prephenazine

Recurrent ventricular tachyarrhythmias required multiple resuscitative efforts with electrical countershock in a 45-year-old woman with previously undiagnosed asymptomatic congenital prolongation of the Q-T interval. This patient represents the oldest person with symptoms relating to idiopathic prolongation of the Q-T interval found in the literature. Exacerbating factors, including diuretic-induced hypokalemia and the concomitant administration of perphenazine, were present. In such cases, initially refractory to therapy with antiarrhythmic agents, insertion of a transvenous pacemaker with overdrive suppression of the ventricular tachyarrhythmias may be lifesaving, allowing for the institution of therapy with agents that can selectively shorten the Q-T interval.