Fish assemblage shifts and species declines in Alabama, USA streams

Abstract –  Recognition of faunal changes requires long-term monitoring, which is lacking for all but a very few streams. Fish surveys are often focused on single, often imperiled, species. While such studies meet the goals of monitoring single species, assemblage-based data are required for detection of assemblage change and declines in common species, and yet these studies are relatively rare. Assemblage-based data may be important in identifying potential ecosystem problems before the loss of ecosystem function that results from catastrophic biodiversity decline. In 2005–2006, we sampled fishes in three streams in the Chattahoochee River drainage, Alabama in order to assess fish assemblage persistence and individual species declines. To achieve these comparisons we used historic data from two time periods, 1970s and 1995. Although comparisons to historical collections were used conservatively, we found dramatic assemblage shifts over time, even using conservative metrics. Examination of individual species persistence over time in these watersheds uncovered species losses at both the site and stream scale. Metrics of similarity, persistence, and Spearman's rank correlation indicated low similarity of fish assemblages and high species turnover over time. Specifically, cyprinid species have been lost and have been replaced with more cosmopolitan species. Comparison of three time periods allowed the estimation of when assemblages changed through time. Changes in land use, increases in the human population and less overall water availability may be agents of habitat degradation partially responsible for fish faunal changes.     

Ethyl formate,formic acid and ethanol in air,wheat, barley and sultanas: analysis of natural levels and fumigant residues

Ethyl formate and ethanol in air, eg in fumigant studies, were readily detected by gas chromatography (GC) (flame ionisation). Residues in wheat, barley and sultanas were analysed by GC, after extraction in polar solvents (eg methanol, aqueous propanol). Both natural levels and levels resulting from fumigation with ethyl formate were measured. Formic acid was extracted from commodities with polar solvents (eg methanol, water) and analysed by GC after esterification. Solvent extracts of commodities were concentrated after addition of disodium hydrogen orthophosphate, and an aliquot added to acidified alcohols (several combinations of acids and alcohols were tested) in a sealed container. Formic acid esters were determined by GC, from headspace sampling over the esterification solvent. Esterification was faster with strong acids than with boric acid. However, esterification with boric acid/butanol gave the least interference of all tested methods. Product identity was confirmed by GC/mass spectrometry. High natural levels of formic acid, and low natural levels of ethyl formate and ethanol, presented problems in identifying residues arising from fumigation. These natural levels are relevant to food regulations for ethyl formate, especially those based on ‘total formic acid, free and combined’. Polar columns (eg FFAP, carbowax) were useful for measurement of formic acid esters, which eluted before the alcohols used for esterification or extraction, whereas elution followed the molecular mass on non-polar columns, such as GS-Q or DB-624. © 1999 Society of Chemical Industry     

Stability of Native Folate and Added Folic Acid in Micronutrient‐Fortified Corn Masa and Tortillas

Degradation of added folic acid and native folates in micronutrient‐fortified corn masa and tortillas was evaluated using masa prepared from either nixtamalized corn flour or fresh nixtamal. Variations in masa pH, masa holding time at an elevated temperature, and iron source failed to show significant differences in folate loss in corn flour masa prepared in the laboratory. Masa was subsequently prepared from fresh nixtamal in a commercial mill in Mexico, and fortified with one of two different micronutrient premixes containing iron, zinc, B‐vitamins, and either unencapsulated or lipid‐encapsulated folic acid. Folate loss in commercial masa increased significantly with prebake masa holding time for both premixes. Unencapsulated folic acid showed a 73% loss after 4 hr of holding, compared to 60% loss for encapsulated. The difference was statistically significant, indicating a protective effect from the lipid coating. No significant differences in folate levels were found between prebake masa and baked tortillas. Holding baked tortillas for up to 12 hr also had no effect on folate levels. Native folate showed no significant losses throughout the process. Results from the commercial tortilla mill indicate that most of the loss in added folic acid occurs during prebake holding of masa, possibly from microbial degradation.     

Pasting Properties and Surface Characteristics of Starch Obtained from an Enzymatic Corn Wet‐Milling Process

Recently, we reported the development of an enzymatic corn wet‐milling process that reduces or eliminates sulfur dioxide requirements during steeping, considerably reduces steep time, and produces starch yields comparable to that of conventional corn wet‐milling. The best results so far, using the enzymatic corn wet‐milling procedure, were achieved when a particular protease enzyme (bromelain) was used. In this study, pasting properties and surface characteristics of starch obtained from six different enzyme treatments (three glycosidases [β‐glucanase, cellulase, and xylanase] and three proteases [pepsin, acid protease, and bromelain]) using the enzymatic corn wet‐milling procedure were evaluated and compared with those from starch obtained using the conventional corn wet‐milling procedure. Significant effects from enzymatic milling were observed on all the three starch pasting properties (peak, shear thinning, and setback). The setback viscosities of starch from all enzyme treatments were significantly lower compared with those of the control sample, indicating that starch polymers from enzymatic corn wet‐milling do not reassociate to the same extent as with the control. Comparison between bromelain treatment and the control sample showed that starch samples obtained from bromelain treatment are very similar to control starch in water‐binding capacity, molecular breakdown, and time to swell when cooked in water. Significant effects from enzymatic milling were observed on the surface characteristics of starch granules. The glycosidase treatments, especially the β‐glucanase samples, showed holes in the starch granules. No visual differences were observed in starch granules between bromelain and control samples.