Dry Deposition of Sulphur at a High-Altitude Background Station in South Africa

Water, Air, &; Soil Pollution - The inferential method is applied to estimate dry deposition rates of sulphur at a remote rural site on the South African south-eastern escarpment. Two 2-week...     

Thermoluminescence dates and palaeoenvironmental information of the late Quaternary sand deposits, Tierra de Pinares, Central Spain

A large amount of Quaternary palaeo-environmental evidence lies within the terrestrial aeolian sediments filling the Duero basin in central Spain. Previous work has identified a number of stratigraphical units although the absolute age and origin of some of these is equivocal. The uppermost unit, the focus of this paper, is a widely distributed sand which covers most of the Tierra de Pinares, north of Segovia. Detailed investigations of an exposure at Burgomillodo reveal over 35 m of laminated and cross-bedded sand from which seven thermoluminescence dates were obtained. The bedding structures indicate a northwesterly palaeowind direction, different from the present dominating westerly winds. Two phases of sand deposition are identified at the site with evidence of erosion and reactivation phases. An upper unit of ca. 7 ka during the warm-aridity of the Atlantic period and a lower unit between 12.5–11 ka coinciding with the cold-aridity of the Younger Dryas event. The latter, in which at least 25 m of sand were deposited at the site, is the dominant phase and is coincident with what has been identified elsewhere in Spain from biological data as a period which was both cold and dry. The Burgomillodos site, therefore, represents the first sedimentological evidence for this arid phase in the Younger Dryas in central Spain.     

西澳州桉树林地土壤菌根菌剂接种潜力研究(英文)

对澳大利亚西澳州桉树人工林菌根类型及其形成情况进行了调查 ,并采用生物测定法 (Bioas saymeasurement)研究了桉树林地土壤菌根菌剂的接种潜力 .根系菌根检查和生物测定法试验均表明 ,在自然条件下桉树可以和不同真菌共生而形成三种类型的菌根 ,即外生菌根、VA菌根和混合菌根 ;林分成熟程度与菌根形成有一定的相关性 ,与共生体的类型也有一定影响 .在幼林中 ,桉树根系主要与内囊霉菌共生形成VA菌根 ,而成熟林主要与担子菌共生形成外生菌根 ,混合菌根表现为一种中间类型 .在收集的林地土壤中移植的菌根诱饵植物 (三叶草和蓝桉 )分别检测出土壤中存在有一定量的VA菌根菌和外生菌根菌 ,但菌根菌繁殖体数量及接种潜力相对较小 ,并且也揭示了按树年龄对土壤菌剂的相对接种潜力影响较大 .本文对桉树人工林土壤菌剂接种潜力进行了评价 ,并就引进优良菌根菌对桉树人工林生产的重要性进行讨论     

Quantifying contributions to tournament catches among resident,stocked and hybrid black basses (Micropterus spp.)

Millions of Florida bass, Micropterus floridanus Lesueur, are stocked annually into populations of largemouth bass, Micropterus salmoides Lacepède, to increase trophy fish abundance. However, little effort has related the role that resultant hybrids make to angler catches. Largemouth bass were sampled from an important recreational fishery subject to extensive Florida bass stocking to address the hypothesis that anglers capture Florida bass, largemouth bass and hybrids at rates equivalent to their overall abundance in the population. Fin clips obtained from tournament angling events (n = 348) and boat‐mounted electrofishing sampling (n = 219) were screened at 38 species‐diagnostic markers and individuals were assigned to genealogical classes using Bayesian clustering algorithms. No significant differences were identified between angler and electrofishing catches providing evidence that hybridised individuals stemming from a long‐term stocking programme may constitute an important contribution to tournament angling catch.     

Vertebral fusions in farmed Chinook salmon (Oncorhynchus tshawytscha) in New Zealand

Vertebral fusions are an established economic concern in farmed Atlantic salmon, but have not been studied in detail in farmed Chinook salmon. Two radiographic studies of vertebral fusions were performed in farmed Chinook salmon. Sixteen of 1,301 (1.2%) smolt and 201 of 2,636 (7.6%) harvest fish had fusions. There were no significant differences in the number of fused vertebrae/fusion in smolt compared with harvest fish. Secondly, tagged fish were repeatedly radiographed to determine the progression of the fusions. Nineteen (4.4%), 23 (5.3%) and 39 (9.0%) fish had fusions as smolt, after 129 days in sea water, and at harvest, respectively. There were no significant differences in the average number of vertebra/fusion between the three time points. Of the fusions that were observed in smolt, additional vertebra did not become fused in 81% of the lesions. Within the rare fusions that did progress due to the involvement of adjacent vertebra, an average of 1.6 vertebrae were added per year. Fish with fusions were significantly lighter than non‐affected fish at harvest. Fusions are common in farmed Chinook salmon; however, they are typically stable after development. As fish with fusions were lighter at harvest, reducing fusions may have an economic benefit.     

Octopus as predators of abalone on a sea ranch

This study examined the occurrence of octopus across an abalone, Haliotis laevigata, Donovan, sea ranch in south‐western Australia, to understand how octopus may be impacting abalone production. Commercial divers removed 654 octopus and 17,666 empty abalone shells during regular, 2 to 4‐weekly surveys over 27 months. A negative binomial generalised linear model estimated a 78% increase in empty shells per artificial abalone habitat per day, when octopuses were present, after adjusting for location and season. Of the 408 shells examined for evidence of predation, 19% had a small, slightly ovoid hole consistent with those made by octopus. The mean (± 1 SE) length of shells with boreholes (70.3 ± 2.2 mm) was significantly longer than those without (59.8 ± 0.5 mm), and boreholes were concentrated over the adductor, respiratory organs and heart. This study provides important insights into the adaptable feeding regimes of octopus and their potential to impose strong top‐down controls on sea ranching operations.     

Model of trawlable area using benthic terrain and oceanographic variables—Informing survey design and habitat maps in the Gulf of Alaska

Bottom trawl surveys provide fishery‐independent data on relative abundance and life history parameters for a wide range of marine taxa. Survey data are used to assess species distribution, biological interactions, and ecosystem structure and to manage marine resources. Not all bottom types or oceanographic conditions accommodate this survey method. We applied National Ocean Service hydrographic smooth sheets to evaluate physical attributes associated with habitat available to surveys. Random forests were used to evaluate the relative influence of benthic terrain and oceanographic predictors in determining accessibility to bottom trawl gear. We examined the marginal importance of each predictor, quantified the response gradient, and applied piecewise regression to determine threshold breakpoint values. Thresholds were used to develop predictive maps and distinguish untrawlable habitat at the scale of discrete towpaths and survey stations. Untrawlable habitat was associated with increased complexity in terrain, roughness, slope, surface curvature, substrate coarseness, current, and aspect. Maps of critical thresholds suggest different variables constrain the probability of a successful trawl in the nearshore, shelf, and continental slope. Overlay analysis of the model projection demonstrates the utility of archived smooth sheet data and identifies areas where higher resolution data might improve results. The model and maps produced in this analysis might be used to identify habitats available to and impacted by commercial trawl fisheries, inform the relative availability of various species and habitat types to bottom trawl surveys, evaluate bias in assessment indices and ecosystem metrics derived from survey data, and advance habitat‐specific biomass estimates.     

Spatial variability in ocean‐mediated growth potential is linked to Chinook salmon survival

Early ocean survival of Chinook salmon, Oncorhynchus tshawytscha, varies greatly inter‐annually and may be the period during which later spawning abundance and fishery recruitment are set. Therefore, identifying environmental drivers related to early survival may inform better models for management and sustainability of salmon in a variable environment. With this in mind, our main objectives were to (a) identify regions of high temporal variability in growth potential over a 23‐year time series, (b) determine whether the spatial distribution of growth potential was correlated with observed oceanographic conditions, and (c) determine whether these spatial patterns in growth potential could be used to estimate juvenile salmon survival. We applied this method to the fall run of the Central Valley Chinook salmon population, focusing on the spring and summer period after emigration into central California coastal waters. For the period from 1988 to 2010, juvenile salmon growth potential on the central California continental shelf was described by three spatial patterns. These three patterns were most correlated with upwelling, detrended sea level anomalies, and the strength of onshore/offshore currents, respectively. Using the annual strength of these three patterns, as well as the overall growth potential throughout central California coastal waters, in a generalized linear model we explained 82% of the variation in juvenile salmon survival estimates. We attributed the relationship between growth potential and survival to variability in environmental conditions experienced by juvenile salmon during their first year at sea, as well as potential shifts in predation pressure following out‐migration into coastal waters.     

Insecticidal properties of benzofuran-2-carboxylic acid derivatives

A series of amides and esters of substituted benzo[b]furan-2-carboxylic acids have been synthesised, and their activity against adult sweet potato weevils, Cylas formicarius elegantulus (Summer) studied. The topical insecticidal potency of these compounds was compared in acetone solution and in a mixture of piperonyl butoxide (PB) and acetone (0·05+99·95 by volume). The compounds were much more active when administered in the acetone/PB mixture, and exhibited 48-h LD₅₀ values ranging from 1·7 to 26·6 μg per insect. The most active compound, 2-(3,5-dimethylpyrazol-1-ylcarbonyl)-6-methoxy-3-methylbenzofuran, was equiactive with technical grade dimethoate (in acetone/PB) on a weight basis. © 1998 SCI