THE INFLUENCE OF P-RETENTION BY SOILS AND SEDIMENTS ON THE WATER QUALITY OF THE LIONS RIVER

SUMMARY

The soils of Midmar dam catchment and the sediments of the Lions river are shown to have high P-retention properties. Present conditions result in little leaching of PO₄ ^?4 from the soils and favour a net transport of P from overlying water to the sediments. P levels in the water are likely to remain low even if the loading rate of P were increased substantially. It is postulated however that other factors may induce a release of P from the sediments and adversely affect the load carried by the water.     

AN HOLISTIC APPROACH TO THE MANAGEMENT OF WATER QUALITY IN FALSE BAY,CAPE TOWN,SOUTH AFRICA

Summary

An overview of the water quality status of False Bay identified the bacterial/viral water quality of stormwater and rivers discharging near contact recreation beaches to be the management concern of highest priority. A second water quality concern is the potential impact of nutrients being discharged into False Bay on the surf zone and bay ecosystems. Heavy metals, hydrocarbons and industrial chemical discharges into the Bay are not regarded as a serious water quality threat. Much of the future development planned for Metropolitan Cape Town will impact on the volume and water quality of rivers, groundwater, stormwater and wastewater flowing into False Bay; hence the need for an integrated catchment management approach to the management of the bay.

An assessment of the constraints facing the holistic management of the bay and catchment concludes that the four main concerns are: (1) a lack of key research information on the options for stormwater management, and on the loading and potential impacts of nutrients being discharged into the surf zone and bay ecosystems; (2) jurisdictional fragmentation, and the lack of coordinated policy and planning between different local and government authorities and other users; (3) legislative fragmentation; and (4) a lack of private sector and public consultation by authorities. Preliminary ideas on the structure of a management body for False Bay and its catchment which address the concerns listed above are presented.     

Ontogenetic structure and distribution patterns of ichthyoplankton in the confluence zone of two river systems in the Eastern Amazon

The ontogenetic structure and longitudinal variability of ichthyoplankton in a confluence zone of two river systems in the Eastern Amazon were evaluated between December 2018 and April 2019, at the time 137 eggs and 7,687 larvae of fish were captured. Ichthyoplankton proved to be heterogeneous between sections of rivers with differences in the number of taxa and abundance. The assemblages were distinguished by a NMDS Analysis, a ANOSIM, a SIMPER and a CCA, they presented a spatial zonation pattern with strong distinction and variability in the composition of the species between the river systems, under strong influence of limnological variables. The assemblages were mainly represented by larvae of Clupeiformes and Perciformes in the clear waters of the Tapajós river and Characiformes and Siluriforms in the cloudy waters of the Amazon river, influenced by the existence of a limnological gradient. Larvae in more advanced development stages were predominant in the Tapajós river while early stages were dominant in the Amazon river. The confluence zone does not seem to be a spawning area, but it is an important transport site for the larvae to reach the nursery areas in the lower stretch of the Amazon river. The encounter of these two river systems seems to guarantee the survival and biological recruitment of several fish species.     

Improved genetic identification of acipenseriform embryos with application to the endangered pallid sturgeon Scaphirhynchus albus

We produced pallid sturgeon Scaphirhynchus albus embryos at five pre-hatch developmental stages and isolated and quantified genomic DNA from four of the stages using four commercial DNA isolation kits. Genomic DNA prepared using the kit that produced the largest yields and concentrations were used for microsatellite DNA analyses of 10–20 embryos at each of the five developmental stages. We attempted to genotype the hatchery-produced embryos at 19 microsatellite loci and confirmed reliable genotyping by comparing the microsatellite genotypes to those of known parents. Embryos at stages 5 and 8 did not produce reliable genotyping while those at stages 14, 24 and 33 did. We used the same DNA isolation method on 262 wild-caught acipenseriform embryos collected from the lower Yellowstone River. A total of 200 of the wild embryos were successfully identified to stages 8 to 34 and the rest could not be staged. Using a combination of single nucleotide polymorphism and microsatellite markers, 249 of the wild-caught embryos were genetically identified as paddlefish Polyodon spathula, five were identified as shovelnose sturgeon Scaphirhynchus platorynchus and eight failed to amplify. None were identified as pallid sturgeon. This study demonstrates that early-stage wild-spawned acipenseriform embryos can be genetically identified less than 24 h post-spawn. This methodology will be useful for recovery efforts for endangered pallid sturgeon and can be applied to other acipenseriform species.     

Does migration promote or inhibit diversification? A case study involving the dominant radiation of temperate Southern Hemisphere freshwater fishes

Although theory predicts that dispersal has a pivotal influence on speciation and extinction rates, it can have contradictory effects on each, such that empirical quantification of its role is required. In many studies, dispersal reduction appears to promote diversification, although some comparisons of migratory and nonmigratory species suggest otherwise. We tested for a relationship between migratory status and diversification rate within the dominant radiation of temperate Southern Hemisphere freshwater fishes, the Galaxiidae. We reconstructed a molecular phylogeny comprising >95% of extant taxa, and applied State-dependent Speciation Extinction models to estimate speciation, extinction, and diversification rates. In contrast to some previous studies, we revealed higher diversification rates in nonmigratory lineages. The reduced gene flow experienced by nonmigratory galaxiids appears to have increased diversification under conditions of allopatry or local adaptation. Migratory galaxiid lineages, by contrast, are genetically homogeneous within landmasses, but may also be rarely able to diversify by colonizing other landmasses in the temperate Southern Hemisphere. Apparent contradictions among studies of dispersal-diversification relationships may be explained by the spatial context of study systems relative to species dispersal abilities, by means of the “intermediate dispersal” model; the accurate quantification of dispersal abilities will aid in the understanding of these proposed interactions.     

皇甫川流域中小型土壤动物对不同水土治理措施的响应

2007年9月至2008年9月,选择皇甫川流域人工松树林、人工杨树林、人工锦鸡儿灌木林、人工沙打旺草地和撂荒地等不同水土治理措施植被为采样地,以耕作农田为对照,研究了中小型土壤动物对不同水土治理措施的响应。结果表明,共捕获中小型土壤动物14 747只,隶属于5门7纲10类。优势类群为线虫,占群落总个体数的比例为95.53%,常见类群为螨类和弹尾类。不同水土治理措施样地中,中小型土壤动物群落个体数较农田有提高趋势,但无显著差异（P >0.05）;螨类和弹尾类个体数显著提高（P<0.05）;线虫个体数在人工沙打旺草地中显著高于农田（P<0.05）;中小型土壤动物垂直分布的表聚性较农田增强,并以地表凋落物覆盖显著的人工林最为明显。RDA分析表明,中小型土壤动物群落、螨类和弹尾类个体数与凋落物厚度、树（草）高和土壤有机质的变化之间呈显著正相关。以上结果说明,研究地区采取的几种水土治理植被均有利于中小型土壤动物群落的恢复;相比较,地表凋落物层显著的人工松树林、人工杨树林更加有益于螨类和弹尾类的恢复。     

Northern richness and southern poverty: contrasting genetic footprints of glacial refugia in the relictual tree Sciadopitys verticillata (Coniferales: Sciadopityaceae)

Sciadopitys verticillata is amongst the most relictual of all plants, being the last living member of an ancient conifer lineage, the Sciadopityaceae, and is distributed in small and disjunct populations in high rainfall regions of Japan. Although mega‐fossils indicate the persistence of the species within Japan through the Pleistocene glacial–interglacial cycles, how the species withstood the colder and drier climates of the glacials is not well known. The present study utilized phylogeography and palaeodistribution modelling to test whether the species survived within pollen‐based coastal temperate forest glacial refugia or within previously unidentified refugia close to its current range. Sixteen chloroplast haplotypes were found that displayed significant geographical structuring. Unexpectedly, northern populations in central Honshu most distant from coastal refugia had the highest chloroplast diversity and were differentiated from the south, a legacy of glacial populations possibly in inland river valleys close to its current northern range. By contrast, populations near putative coastal refugia in southern Japan, harboured the lower chloroplast diversity and were dominated by a single haplotype. Fragment size polymorphism at a highly variable and homoplasious mononucleotide repeat region in the trnT‐trnL intergenic spacer reinforced the contrasting patterns of diversity observed between northern and southern populations. The divergent histories of northern and southern populations revealed in the present study will inform the management of this globally significant conifer. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 263–277.     

Life history and production of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) in the lower Ebro river: a comparison after 18 years

The life history of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) was studied during spring and summer 2005 in the lower Ebro river (Catalonia) and compared to a previous study performed in 1987 (Ibáñez, Escosa, Muñoz and Prat 1991). The results showed an advancement of Ephoron virgo life cycle and an increase of production estimates. In 2005 larval development reached the maximum size one month earlier than in 1987, and adult emergence peak began three weeks earlier. Comparing adult sex ratios (F:M), there was a major presence of females in 2005 (1:4), while the opposite was observed in 1987 (2:1). Secondary production was higher in 2005 than in 1987, obtaining 950 mg dry weight/m²/year with the increment summation method and 1080 mg dry weight/m²/year using the removal summation method. Higher water temperatures were measured for the entire 2005 larval growth period, which were related to higher air temperatures. Therefore, that temperature increment was likely the main cause of changes observed in the Ephoron virgo life cycle.     

基于大型底栖动物群落的上海市河道水质生物学评价

2011年夏秋季,在上海市全境83个河道断面开展了河道底栖动物采样,共获取底栖动物20个分类单位（种）。9个极严重污染断面未采集到活体生物,生境基本丧失。其余74个有活体生物断面,采用三种常用生物指数：Shannon-Wiener多样性指数、Hilsenhoff耐污指数、Goodnight修正指数分别进行计算及评价。Shannon-Wiener多样性指数判别为25个严重污染和49个重污染断面;Hilsenhoff耐污指数划分38个重污染、5个中污染和31个轻污染断面;Goodnight修正指数划分33个重污染、2个中污染和39个轻污染断面。与典型河道断面的水质理化指标监测值进行对照,Shannon-Weiner多样性指数对河道水质评价的准确度较低,Hilsenhoff生物指数和Goodnight修正指数的水质评价效率及准确度均较高,断面污染等级与水质理化指标基本对应。     

Changes in diatom-dominated biofilms during simulated improvements in water quality: implications for diatom-based monitoring in rivers

Although benthic diatoms are used to assess river water quality, there are few data on the rate at which diatom assemblages react to changes in water quality. The aim of this study was to assess the reaction time of diatoms and to discuss the changes occurring during water quality improvement on the basis of their autecological characteristics. In order to simulate this improvement, diatom-dominated biofilms grown on artificial sandstone substrata were transferred from several polluted rivers to an unpolluted river. They were sampled three times: before transfer and 1 and 2 months after transfer. The ecology and growth-forms of the taxa explained most of the changes in species composition observed during the experiment. Adnate diatoms gradually replaced motile and stalked taxa. Gomphonema parvulum, a stalked diatom positioned vertically in the biofilm, is adapted for light and space competition in high-density algal biofilms. When transferred to an unpolluted site, this growth-form is less competitive and does not tolerate the high grazing pressure. Fistulifera saprophila is a single celled motile diatom, living in organic matrices. When the artificial substrata were transferred to the unpolluted site, this particular ecological niche disappeared quickly. On the other hand, Achnanthidium minutissimum, which is considered to be cosmopolitan and an early colonizer, increased during the first month of transfer and then decreased. It was gradually replaced by A. biasolettianum, which was the taxon best suited to this pristine stream. The changes observed differed between treatments depending on the species composition and architecture of the biofilms. In particular, biofilms dominated by stalked and motile diatoms were more quickly modified than those dominated by small motile diatoms. The diatom index reflects these changes, and its values showed that about 60 days following a water quality improvement were necessary for transferred diatom assemblages to reach diatom index values similar as those at the unpolluted river.