Transport and accumulation of bloom-forming cyanobacteria in a large, mid-latitude lake: the gyre-Microcystis hypothesis

 Toxic cyanobacterial blooms have occurred in the near-shore waters of the North Basin of Lake Biwa, Japan, since 1994, and have been attributed to deterioration of water quality in the enriched littoral zone of the lake. From 1997 onwards, the bloom-forming cyanobacteria have been observed with increasing frequency in the deep offshore waters of the North Basin. In the present study, we examined the mechanisms responsible for these bloom populations in the main body of the lake. Specifically, we addressed the hypothesis that buoyant, nutrient-replete colonies of cyanobacteria are generated inshore, are advected offshore by large-scale horizontal transport processes, and subsequently accumulate in the downwelling center of large surface gyres that characterize the overall circulation pattern in the epilimnion of the North Basin. Diel variations of Microcystis biomass at the center and the edge of the Lake Biwa gyre were monitored at 6-h intervals on August 23–24, 2000, and the horizontal distribution of buoyant Microcystis was determined on October 6. The hydrodynamic structure of the first gyre was determined over the preceding 2 days by an on-board Acoustic Doppler Current Profiler (ADCP). The gyre was characterized by a counterclockwise horizontal current that could potentially advect material large distances offshore, a downwelling current near the center of the gyre, and an upwelling current at the edge of the gyre, caused by the radial pressure gradients. The biomass of Microcystis near the water surface was greater at the center than at the edge of the gyre, and the biomass at 5 m depth at the edge of the gyre was greater than that at the water surface or at the thermocline near the edge of the gyre. The results are consistent with the gyre-Microcystis hypothesis, and show the potential for accumulation of large concentrations of cyanobacteria in deep offshore lake environments that are normally considered unsuitable for cyanobacterial blooms. Received: July 16, 2001 / Accepted: March 6, 2002     

Estimation of coancestry in Iberian pigs using molecular markers

Genetic markers provide a useful tool toestimate pairwise coancestry betweenindividuals in the absence of a known pedigree. Inthe present work 62 pigs from two relatedstrains of Iberian breed, Guadyerbas andTorbiscal, belonging to a conservationprogramme with completely known pedigrees since1945, have been genotyped for 49microsatellites. Four coefficients thatsummarise molecular resemblance betweenindividuals together with eightestimators of coancestry have been calculatedfrom this information. Their values werecompared with the genealogical coancestry,calculated from the complete or partialpedigree. The eight estimations obtained usingmolecular information substantiallyunderestimate the coancestry calculated usingthe genealogical analysis. The correlationbetween the estimates and the genealogicalvalues was also calculated. This correlationwas high, between 0.78 and 0.93 for differentestimators, when all pairwise comparisons amongthe 62 animals were considered. However, thecorrelation decreases remarkably to 0.49–0.69and 0.37–0.47 for the Guadyerbas and Torbiscalpopulations respectively, when they wereanalysed separately. All the correlations weresimilar to those obtained when using simplecoefficients of molecular resemblance such asmolecular coancestry or similarity indexes.Finally, simulations were carried out tofurther explore the results obtained. It isconcluded that lack of information on theallele frequencies in the base population mayexplain the bias of these estimators inpopulations with complex pedigrees.     

Test for positional candidate genes for body composition on pig chromosome 6

One QTL affecting backfat thickness (BF), intramuscular fat content (IMF) and eye muscle area (MA) was previously localized on porcine chromosome 6 in an F₂ cross between Iberian and Landrace pigs. This work was done to study the effect of two positional candidate genes on these traits: H-FABP and LEPR genes. The QTL mapping analysis was repeated with a regression method using genotypes for seven microsatellites and two PCR-RFLPs in the H-FABP and LEPR genes. H-FABP and LEPR genes were located at 85.4 and 107 cM respectively, by linkage analysis. The effects of the candidate gene polymorphisms were analyzed in two ways. When an animal model was fitted, both genes showed significant effects on fatness traits, the H-FABP polymorphism showed significant effects on IMF and MA, and the LEPR polymorphism on BF and IMF. But when the candidate gene effect was included in a QTL regression analysis these associations were not observed, suggesting that they must not be the causal mutations responsible for the effects found. Differences in the results of both analyses showed the inadequacy of the animal model approach for the evaluation of positional candidate genes in populations with linkage disequilibrium, when the probabilities of the parental origin of the QTL alleles are not included in the model.     

Fermentative Production of Succinic Acid from n-Paraffin by Candida brumptii IFO 0731

An investigation of succinic acid production from n-paraffin under various culture conditions was carried out with Candida brumptii IFO 0731. Ammonium nitrogen was required for both cell growth and succinic acid production. Favorable culture conditions for succinic acid production were ascertained. The productivity was markedly increased by the additions of CaCO₃ and organic nutrients. Under the best condition, the largest quantity of succinic acid production, 23.6 mg/ml, was obtained in a 67% yield from super heavy n-paraffin after 8 days cultivation.     

Aeronian (Llandovery, Lower Silurian) palynomorphs and graptolites from the Lipeón Formation, Eastern Cordillera, north-west Argentina

The lower levels of the Lipeón Formation, in the Eastern Cordillera, north-west Argentina, yield a marine-dominated palynomorph assemblage, together with graptolites of mid to late mid Llandovery age (Demirastrites convolutus and probably Stimulograptus sedgwickii zones). The palynomorph assemblage is dominated by acritarchs, but also contains algae and terrestrial cryptospores. Crassiangulina variacornuta, considered a potentially good global biostratigraphical marker for the Upper Llandovery is recovered for the first time from the Silurian of Argentina. The occurrence of this species in strata not younger than late Aeronian, and independently dated by graptolites, indicates an early first appearance for Crassiangulina variacornuta, in the Lipeón Formation, below the Aeronian/Telychian boundary. The lower part of the unit corresponds to a quiet marine environment; thus supporting that Crassiangulina variacornuta is a facies-sensitive acritarch.     

Regulation of oxygen sensing by ion channels.

O(2) sensing is of critical importance for cell survival and adaptation of living organisms to changing environments or physiological conditions. O(2)-sensitive ion channels are major effectors of the cellular responses to hypoxia. These channels are preferentially found in excitable neurosecretory cells (glomus cells of the carotid body, cells in the neuroepithelial bodies of the lung, and neonatal adrenal chromaffin cells), which mediate fast cardiorespiratory adjustments to hypoxia. O(2)-sensitive channels are also expressed in the pulmonary and systemic arterial smooth muscle cells where they participate in the vasomotor responses to low O(2) tension (particularly in hypoxic pulmonary vasoconstriction). The mechanisms underlying O(2) sensing and how the O(2) sensors interact with the ion channels remain unknown. Recent advances in the field give different support to the various current hypotheses. Besides the participation of ion channels in acute O(2) sensing, they also contribute to the gene program developed under chronic hypoxia. Gene expression of T-type calcium channels is upregulated by hypoxia through the same hypoxia-inducible factor-dependent signaling pathway utilized by the classical O(2)-regulated genes. Alteration of acute or chronic O(2) sensing by ion channels could participate in the pathophysiology of human diseases, such as sudden infant death syndrome or primary pulmonary hypertension.