A sensitivity analysis of Southwestern climate [abstract and conclusions]

EXTRACT (SEE PDF FOR FULL ABSTRACT): We provide here an estimate of the extent that modern climate in the southwest US is sensitive to changes in several parameters that reflect global climatic changes. For the purposes of this study, we define modern climate as mean monthly values for the months of February and August (called winter and summer, respectively) of temperature and precipitation, at points representing the average of cells of dimension 7.5' on a side. The area studied surrounds the drainage basin of Death Valley, California.

中国西南地区晚二叠世莲座蕨目植物研究

本论文应用揭膜方法（Peeling Method）对产于我国西南地区滇东黔西一带晚二叠世地层中的保存有解剖构造的莲座蕨目化石进行了较为深入的研究，包括3 种茎和一种生殖器官。3 种茎中有二种为本文首次研究，均归入辉木属Psaronius Cotta，建立了二个新种：盘县辉木P. panxianensis 和老屋基辉木P. laowujiensis；另外一个种－田氏辉木P. tianii Li（MS）为前人所建立，但未正式发表，本文做了重新研究，新发现了一些特征，并对一些已有特征做了修订。讨论了这3 个种一些重要特征的分类和系统演化意义，这些特征包括：叶迹最后分出时的维管构型、维管束鞘和边缘茎维管束内侧的厚壁组织束。通过对不同地区和不同时代辉木属已有种的特征分析，对辉木属属下分类做了尝试，根据维管束是否结成环状、叶迹维管构型、是否具维管束鞘、边缘茎维管束内侧的厚壁组织束的发育与否、边缘茎维管束是否分叉等特征将辉木属已有种（包括本文所研究的3 个种）分为5 个组：1. Blicklei 组，代表种为Psaronius blicklei Morgan，包括欧美植物区目前已知各种，可能还包括华夏植物区的一些种。它们的主要特征是：不具维管束鞘；边缘茎维管束内侧的厚壁组织束不发育。2．Panxianensis 组，代表种为盘县辉木Psaronius panxianensis He，Wang，Hilton,Tian et Zhou，包括王氏辉木、老屋基辉木、江苏辉木，可能还有八角辉木和六角辉木。最主要特征是：具维管束鞘，简单，仅由薄壁细胞构成；边缘茎维管束内侧具树枝状和伞状或锚状厚壁组织束；叶迹由3 根维管束构成。该组目前仅发现于华南地区二叠系。3. Tianii 组，以田氏辉木Psaronius tianii Li（MS）为代表，目前只有这一个种。该组的主要特征：具维管束鞘，复杂，可分为两层；边缘茎维管束内侧具菊花状厚壁组织束，且每两环维管束之间具两条厚壁组织束，其中一条连续，另一条不连续；叶迹呈歪斜的弓形或M 形；叶迹维管束与茎维管束等粗；边缘茎维管束可分叉。该组目前仅发现于华南地区二叠系。4. Brasiliensis 组，以巴西辉木Psaronius brasiliensis Brongniart 为代表，除巴西辉木外，可能还包括P. sp. Herbst。该组的最主要特征就是其维管束的一端内卷并与主体部分连接形成一个封闭的环状构造；茎中央的维管束小，形态多变，而且排列十分不规则。该组目前仅发现于南美地区二叠系。5. Sinuosus 组，以P. sinuosus Herbst 为代表，目前也只有此一个种。其最主要的特征就是叶迹具多个维管束，且排列无规则；茎维管束非常长，呈盘绕状。该组目前仅发现于南美地区二叠系。生殖器官归入虫囊蕨属Scolecopteris（Zenker）Millay，建立一新种：贵州虫囊蕨。该种仅保存有聚合囊和分散的孢子囊，生殖小羽片不明。孢子囊面向外的壁较厚，但分化，自内向外可分为三部分；孢子具三缝，较大，直径55-60μm。由于该种同时拥有Millay 认为的原始特征（大的孢子）和进化特征（即分化的孢子囊面向外的壁）。很可能Millay 的观点仅仅反映了欧美植物区虫囊蕨属的演化规律。

Age, growth and mortality of the toadfish, Halobatrachus didactylus (Schneider, 1801) (Pisces: Batrachoididae), in the Bay of Cádiz (southwestern Spain)

Age, growth and mortality of the toadfish, Halobatrachus didactylus, were determined by examination of the whole sagittal otoliths of fish sampled in the Bay of Cádiz (southwestern Spain) from March 1999 to March 2000. A total of 844 specimens (425 males, 416 females, and 3 of indeterminate sex), ranging from 95 to 470 mm in total length were examined. Eighty-nine percent of the otoliths could be read allowing an age estimation. The opaque zone was formed between April and May coincident with the maximum reproductive peak, while the translucent zone formed mainly in summer-fall (June to December). Maximum ages for males and females were 12 and 10 years, respectively. The samples were dominated by 2- to 6-year-old specimens. Males matured at an age of approximately 2 years and females at 3 years. Fish total length and otolith radius were closely related. The von Bertalanffy growth curve was used to describe growth. The parameters were derived from back-calculated length-at-age. Significant differences in the growth parameters were found between sexes. Although the growth analysis revealed that this species is slow-growing, males reached larger sizes than females. Females appeared to experience higher natural mortality rates than males.

A sudden collapse in distribution of Pacific sardine (Sardinops sagax) off southwestern Australia enables an objective re-assessment of biomass estimates

Fishery-independent estimates of spawning biomass (BSP) of the Pacific sardine (Sardinops sagax) on the south and lower west coasts of Western Australia (WA) were obtained periodically between 1991 and 1999 by using the daily egg production method (DEPM). Ichthyoplankton data collected during these surveys, specifically the presence or absence of S. sagax eggs, were used to investigate trends in the spawning area of S. sagax within each of four regions. The expectation was that trends in BSP and spawning area were positively related. With the DEPM model, estimates of BSP will change proportionally with spawning area if all other variables remain constant. The proportion of positive stations (PPS), i.e., stations with nonzero egg counts — an objective estimator of spawning area — was high for all south coast regions during the early 1990s (a period when the estimated BSP was also high) and then decreased after the mid-1990s. There was a decrease in PPS from the mid-1990s to 1999. The particularly low estimates in 1999 followed a severe epidemic mass mortality of S. sagax throughout their range across southern Australia. Deviations from the expected relationship between BSP and PPS were used to identify uncertainty around estimates of BSP. Because estimation of spawning area is subject to less sampling bias than estimation of BSP, the deviation in the relation between the two provides an objective basis for adjusting some estimates of the latter. Such an approach is particularly useful for fisheries management purposes when sampling problems are suspected to be present. The analysis of PPS undertaken from the same set of samples from which the DEPM estimate is derived will help provide information for stock assessments and for the management of purse-seine fisheries.

Movement of American lobster (Homarus americanus) in the southwestern Gulf of St. Lawrence

A total of 42,445 American lobsters (Homarus americanus) were tagged in thirty-one sites throughout the southwestern Gulf of St. Lawrence between 1980 and 1997. Results from the recapture of 8503 tagged lobsters showed small distances traveled between the release and the recapture position for animals ranging in size from 51 to 152 mm carapace length. The average distance traveled ranged from 2 km in parts of Baie des Chaleurs and western Cape Breton to 19 km in central Northumberland Strait. Lobsters moved generally along the shore (93% of the dispersion was in areas between the shore and the 20-m bathymetric contour). As a result, lobsters traveled longer distances in sites characterized by a gradually sloping bottom where the distance between the shore and the 20-m contour line was extensive in contrast to areas characterized by rapidly changing depths and by a relatively small amount of habitat shallower than 20 m. In the majority of sites (14 of 19) there was no significant difference between males and females in the average distance they traveled. In four of the five sites females moved farther than males. In general, the average distance traveled by berried females was shorter than that traveled by males or nonberried females. No relationship was observed between the distance traveled and the size of the animal. There was no strong evidence of a relationship between the average distance traveled and the number of days at liberty. In general, lobsters in the southwestern Gulf of St. Lawrence traveled short distances and dispersion was restricted to the nearshore habitat. Further, the distance traveled was not correlated to size, sex, or years at large. These findings show that there is little interaction between American lobsters from different fishing areas at the benthic level and that American lobster movements should have minimal consequences for management of the species in the southwestern Gulf of St. Lawrence.

The phytoplankton species composition and abundance of Ogun River, Abeokuta, southwestern Nigeria

The phytoplankton species composition and abundance in Ogun River, Ogun state, Southwest Nigeria was studied for a period of seven months (December, 2011 - June, 2012), a total of forty-one genera belonging to five taxonomic groups were recorded from Ogun River. The phytoplankton species composition was surpassed by Chrysophyta with 15 species consisting of 36.6% followed by Chlorophyta with 14 consisting of 34.1%. This was followed by Cyanophyta (7 species) consisting of 17.1%, Euglenophyta with 3 species consisting of 7.3% and Pyrrophyta with 2 species consisting 4.92%. Cyanophyta was the highest in abundance consisting of 41% while the lowest in abundance was Pyrrophyta consisting of 1.5%. The low nature of phytoplankton abundance and diversity observed in this study must have been caused by the polluted nature of the water due to the anthropogenic activities carried out around its shores The dominance of Cyanophyta in this river is similar to findings from Lake Victoria, Lake Bishoftu, Lake Chaohu and the temple pond of Thirupour.

The zooplankton species composition and abundance in Ogun River, Abeokuta, Ogun State, southwestern Nigeria

Investigation on the species composition and abundance of zooplankton in Ogun River, Abeokuta, Ogun state, Southwestern Nigeria was carried out for a period of seven months (December, 2011-June, 2012), Using hand trawling method, 55 µm mesh size plankton net was trawled horizontally ten times to capture zooplankton. The zooplankton samples were put into properly labeled plastic containers and preserved in 4% formalin solution. A total of sixteen genera from five taxonomic groups were recorded from Ogun River. Cladocera predominated both in terms of species composition and abundance. Five species of Cladocera was recorded consisting of 31.25%. Protozoa and Rotifera recorded four species each consisting of 25%. Copepoda recorded two species consisting of 12.5%, and Ostracoda with one species consisting of 6.25%. The low nature of zooplankton abundance and species composition observed in this study must have been caused by the polluted nature of the water due to the anthropogenic activities carried out around its shores The dominance of Cladocera in this river is similar to findings from River Echara and River Imo, Southeastern Nigeria.

Assessment of some physico-chemical parameters of River Ogun (Abeokuta, Ogun State, southwestern Nigeria) in comparison with national and international standards

This study assessed the physico-chemical quality of River Ogun, Abeokuta, Ogun state, Southwestern Nigeria. Four locations were chosen spatially along the water course to reflect a consideration of all possible human activities that are capable of changing the quality of river water. The water samples were collected monthly for seven consecutive months (December 2011 – June 2012) at the four sampling stations. pH, air temperature (℃), water temperature (℃), conductivity (µs/cm) and total dissolved solids (mg/L) were conducted in-situ with the use of HANNA Combo pH and EC multi meter Hi 98129 and Mercury-in-glass thermometer while dissolved oxygen (mg/L), nitrate (mg/L), phosphate (mg/L), alkalinity (mg/L) and hardness (mg/L) were determined ex-situ using standard methods. Results showed that dissolved oxygen, hydrogen ion concentration, total hardness and nitrate were above the maximum permissible limit of National Administration for Food, Drugs and Control (NAFDAC), Standard Organization of Nigeria (SON), Federal Environmental Protection Agency (FEPA), United States Environmental Protection Agency (USEPA), European Union (EU) and World Health Organization (WHO) for drinking water during certain months of the study period. Results also showed that water temperature and conductivity were within the permissible limits of all the standards excluding FEPA. However, total dissolved solids and alkalinity were within the permissible limits of all the standards. Adejuwon and Adelakun, (2012) also reported similar findings on Rivers Lala, Yobo and Agodo in Ewekoro local government area of Ogun state, Nigeria. Since most of the parameters measured were above the maximum permissible limits of the national and international standards, it can be concluded that the water is unfit for domestic uses, drinking and aquacultural purposes and therefore needs to be treated if it is to be used at all. The low dissolved oxygen values for the first four months was too low i.e. < 5 mg/L. This is most likely as a result of the amount of effluents discharged into the river. To prevent mass extinction of aquatic organisms due to anoxic conditions, proper regulations should be implemented to reduce the organic load the river receives.

A statistical model of climates in the southwestern United States

EXTRACT (SEE PDF FOR FULL ABSTRACT): We describe an empirical-statistical model of climates of the southwestern United States. Boundary conditions include sea surface temperatures, atmospheric transmissivity, and topography. Independent variables are derived from the boundary conditions along 1000-km paths of atmospheric circulation. ... Predictor equations are derived over a larger region than the application area to allow for the increased range of paleoclimate. This larger region is delimited by the autocorrelation properties of climatic data.