Analysis of phosphorus in two humic acid fractions of intensively cropped lowland rice soils by 31P‐NMR

The organic forms of phosphorus in the soil appear to be changing as rice growing intensifies and the soil is flooded for longer in tropical Asia. To examine these changes, we extracted the labile mobile humic acid (MHA) and more recalcitrant calcium humate (CaHA) fractions from soils supporting long‐term field trials in the Philippines and analysed them by solution ³¹P‐nuclear magnetic resonance (NMR) spectroscopy. Diester P and sugar‐diester P accumulated moderately with increasing intensity of irrigated rice cropping, reaching a combined 42% of all MHA‐P for a triple‐cropped irrigated field compared with 28% for fully aerated fields growing dryland crops. The mono‐ to diester P ratio decreased by 43% for the MHA and CaHA from the aerated fields to the triple‐cropped field. Smaller effects on forms of P were noted for the rates and type of N, P and K fertilizer and site effects. The effects of treatment and site were more noticeable in the MHA than in the CaHA. The proportions in the NMR spectra were tightly correlated with visible light absorption, concentrations of organic free radicals and H, and ¹⁵N‐NMR spectral proportions, which indicate the degree of humification. The MHA and CaHA accounted for only 0.6–8.3% and 0.9–5.7%, respectively, of total P; most of the P is inorganic.     

Using allometry with fish size to estimate production to biomass (P/B) ratios of salmonid populations

Abstract – The ratio of annual production rate to average biomass ( P / B ) is sometimes used as a shortcut method of estimating production if biomass is known. P / B ratios vary among salmonid populations in different areas depending on the species, fish size and growing conditions. The hypothesis that annual P / B ratios for salmonid populations can be predicted from the allometric equation: P / B  =  a W ^−0.35 was investigated in this study. The allometric coefficient (−0.35) was obtained from the literature, and W was the average weight (g) of fish in the population. Plots of P / B versus fish weight for three species of salmonids, Salvelinus fontinalis , Salmo trutta and Salmo salar , showed a declining trend, with a slope consistent with the hypothesis. The coefficient a of the allometric equation was species and habitat dependent. The efficacy of using the allometric formula to estimate the P / B ratio of specific salmonid populations is examined.     

Florida manatees, Trichechus manatus latirostris, respond to approaching vessels

Florida manatees inhabit shallow coastal and estuarine waters of the southeast US, a range that brings them into frequent contact with vessels. More than 30% of documented annual mortalities are attributed to vessel collisions, and most living animals bear the scars of multiple, non-lethal encounters. To document the behavior of manatees in the presence of vessels, we recorded their movements with an overhead video system. We scored six aspects of behavior during 170 vessel approaches, and compared their behavior with 187 control segments when no boats were present. Manatees in shallow waters and at the edge of the channel responded to approaches by orienting towards the nearest deep water, a boat channel, and increasing their swimming speed. Close boat approaches and shallow water depths exacerbated these responses. Our results indicate that manatees detect and respond to approaching vessels with an apparent flight response, a response which includes movement towards deeper water. If given sufficient time, i.e., approached or passed slowly, the manatees may then be able to reach deeper water and safe depths.     

Impact of anthropogenic CO2 on the CaCO3 system in the oceans

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell-forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO3 dissolution rate for the global oceans is approximately 0.5 +/- 0.2 petagrams of CaCO3-C per year, which is approximately 45 to 65% of the export production of CaCO3.     

Experimental and Practical Diet Evaluations with Juvenile Hybrid Striped Bass1

Culture of hybrid striped bass has been expanding in the United States and further growth has been predicted, however, several problem areas exist, including a lack of nutritional information. This series of studies offered reciprocal cross juvenile hybrids several of the commercially available feeds and several different types of purified experimental diets. Weight gain and feed efficiency of fish fed the commercially available feeds formulated to meet the general requirements of salmonids were better than fish fed feeds formulated to meet the nutritional requirements of catfish. Experimental diets containing casein as the primary protein source were unpalatable regardless of the level of fish oil added (6 or 12%) but were accepted if 10% menhaden fish meal was added. Addition of lower levels of fish meal resulted in decreasing degrees of acceptance. Thus, the minimum level of fish meal that elicited a feeding response appeared to be between 510% of the dry diet. A crystalline amino acid test diet was palatable, and weight gain of fish fed that diet was 65–91% of the weight gain recorded for fish fed the positive control diets. Addition of L-arginine, L-methionine or L-cystine to a purified diet containing casein did not result in dietary acceptance. Whole-body proximate composition offish revealed a general trend toward increased lipid levels with increasing levels of dietary lipid. All fish exhibited microvessicular hepatopathy, regardless of diet fed. Hepatocytes contained both glycogen and lipid in the cytoplasm.     

Sympathetic outflows from cervical spinal cord in the dog

In some dogs there are preganglionic fibers leaving the cervical spinal cord through the ventral roots of the lower cervical nerves. When these fibers are stimulated electrically in the anesthetized dog with skeletal muscle paralysis (induced by decamethonium), the effects are vasoconstriction in the front footpad, cardiac acceleration and augmentation, and a rise in arterial blood pressure.     

Conserved structure for single-stranded telomeric DNA recognition

The essential Cdc13 protein in the yeast Saccharomyces cerevisiae is a single-stranded telomeric DNA binding protein required for chromosome end protection and telomere replication. Here we report the solution structure of the Cdc13 DNA binding domain in complex with telomeric DNA. The structure reveals the use of a single OB (oligonucleotide/oligosaccharide binding) fold augmented by an unusually large loop for DNA recognition. This OB fold is structurally similar to OB folds found in the ciliated protozoan telomere end-binding protein, although no sequence similarity is apparent between them. The common usage of an OB fold for telomeric DNA interaction demonstrates conservation of end-protection mechanisms among eukaryotes.