1,312 research outputs found
To restore or not? A valuation of social and ecological functions of the Marais des Baux wetland in Southern France
No full textThe Marais des Baux wetland in southern France has for centuries been subject to drainage, almost causing its entire disappearance. With an increasing awareness of wetland ecosystem services, the extensive drainage is being questioned today. To guide policy-makers and landowners in their decision-making, we use a Choice Experiment to elicit the preferences of the general public for potential land use and activity changes in the Marais des Baux. These changes concern wetland restoration, the extent of tree hedges, recreational opportunities, mosquito control and biodiversity.
Acid fermentation of primary sludge at 20v C
No full textIncludes bibliography.Full scale studies on biological excess phosphrous removal plants have demonstrated the biological excess phosphorous removal can be increased by acid fermenting the settled sludge in the primary settling tank, and adding either the fermented sludge, or the acids elutriated from the sludge, to the influent of the biological phosphorous removal plant. Considerable uncertainty still exists, however, as to the mass of short chain fatty acids that can be generated and the degree of improvement in phosphorous removal that can be expected. This study was undertaken to (1) evaluate short chain fatty acid production in laboratory scale batch, single and in-series completely mixed reactor systems, (2) development of a model for acid fermentation, and (3) theoretically estimate the effect of acid addition on biological excess phosphorous removal
Use of a reciprocal transplant study to measure the rate of plant community change in a tidal marsh along a salinity gradient
No full textFreshwater reclaimed marshes along the European Atlantic coast are highly suitable for European eels (Anguilla anguilla). However, European eel stocks have declined, and the coastal marshes have been subjected to major disturbances. The objective of our study was to analyze the processes governing patterns of European eel microhabitat distribution of four eel size classes (from ,160 mm to .360 mm) in a reclaimed marsh (France). Analyses were conducted using artificial neural network (ANN) techniques and ecological profiles. Our ANN results showed that eel densities were significantly related to three major influencing variables: the width of ditch section, the silt depth, and the density of emergent plants. Such ecological profiles were significantly different between small (,240 mm) and large eels (.360 mm): small eels were more widespread than large eels. Large eels were absent or at low densities in shallow ditches with a high aquatic plant cover obstructing the water column and a large quantity of silt. These characteristics seem to define the ditches not directly connected with the main river where dredging operations were rare. Management of regular dredging operations in the channels by maintaining a mosaic of permanent aquatic habitats and avoiding the heavy silt loads in most ditches should be promoted. This dredging operation was probably one of the most promising ways for restoring inland eel stocks
European salt marshes diversity and functioning: the case study of the Mont Saint-Michel bay, France
No full textThe macrotidal Mont Saint-Michel bay has been studied intensively since 1990. The objectives of this study, supported by the European Union, was to understand various processes underlying the functioning of this hydrosystem with a special focus on organic matter and nutrient fluxes between saltmarshes and marine waters. This paper presents a synopsis of these studies. The tidal flats are unvegetated and primary production is exclusively due to microphytobenthos communities dominated by diatoms. Halophile plant communities colonize the top parts of the tidal flats. Their composition and production vary according to a maturity gradient and sheep grazing. In ungrazed saltmashes, production ranged from 1080 gDW m−2yr−1 in the lower marsh to 1990 gDW m−2yr−1 in the upper marsh whereas it was only 200 to 500 gDW m−2yr−1 in Salicornia spp. dominated pioneer zones and sheep grazed areas. Most of this organic matter (OM) was trapped in situ, processed by fungi and bacteria, and then released seaward via tidal fluxes, groundwater and runoff as particulate OM and nutrients: –497 kg N, –1200/–1000 kg P-PO4 and –9900/–4200 kg inorganic carbon). A small amount of OM was exported to the bay as macrodetritus. Fatty acids and stable isotopes, used as markers, showed that OM produced by the marsh halophytes contributed to the diet of all the tidal flats invertebrates that were studied. Transient fish species were shown to colonize the saltmarshes to forage or graze, exporting about 50 tons POM (DW)y−1. Therefore, it is assumed that the saltmarsh production enhances the production of the whole bay. But the functioning is still poorly known because the nutrient sinks have not all been identified. Part of the nutrients input was provided by precipitation (+327 kg y−1), but the contribution of the catchments was not quantified despite the fact that their influence was shown by the presence of lindane in all the compartments of the system. Dynamics of saltmarshes are mainly influenced by natural sedimentation (1.5 million m3y−1 in the bay), plant community succession, and management (i.e., reclamation and agricultural activities)
Composition of fish communities in macrotidal salt marshes of the Mont Saint-Michel bay (France)
No full textAt least 100 fish species are known to be present in the intertidal areas (estuaries, mudflats and salt marshes) of Mont Saint-Michel Bay. These and other comparable shallow marine coastal waters, such as estuaries and lagoons, play a
nursery role for many fish species. However, in Europe little attention has been paid to the value of tidal salt marshes for fishes. Between March 1996 and April 1999, 120 tides were sampled in a tidal creek. A total of 31 species were caught. This community was largely dominated by mullets (Liza ramada represent 87% of the total biomass) and sand gobies(Pomatoschistus minutus and P. lozanoi represent 82% of the total numbers). These species and also Gasterosteus aculeatus, Syngnathus rostellatus, Dicentrarchus labrax, Mugil spp., Liza aurata and Sprattus sprattus were the most frequent species (>50% of monthly frequency of occurrence). In Europe, salt marshes and their creeks are flooded only during high spring tides. So, fishes only invade this environment during short immersion periods, and no species can be considered as marsh
resident. But, the salt marsh was colonized by fish every time the tide reached the creek, and during the short time of flood, dominant fishes fed actively and exploited the high productivity. Nevertheless, this study shows that there is little interannual variation in the fish community and there are three ‘ seasons ’ in the fish fauna of the marsh. Marine straggler and marine estuarine dependent species colonize marshes between spring (recruitment period in the bay) and autumn before returning into deeper adjacent waters. Estuarine fishes are present all year round with maximum abundances in the end of summer. The presence of fishes confirms that this kind of wetland plays an important trophic and nursery role for these species. Differences in densities and stages distribution of these species into Mont Saint-Michel systems (tidal mudflats, estuaries and tidal salt marshes) can reduce the trophic competition
Developing a model to silmulate least economic cost evaluation of transmission expanison investment
No full textTransmission planning can broadly be categorized into deterministic and probabilistic reliability planning. The probabilistic approach is often preferred as it aims to reduce transmission supply costs, by sharing risk between the customer and the utility. This is done by determining the least economic cost (LEC) between the customer interruption cost (CIC) and capital investment required to improve the network reliability. However performing a LEC evaluation requires substantially more variables than deterministic evaluation. This paper analyses the LEC methodology and develops a simulation model to perform probabilistic least economic cost evaluations. © Copyright KTH 2006.Marais, Ronald ; Estment, Roy ; Zivanovic, Rastk
Notice biographique sur le F ̤. Albert Le Roy... / R ̤.L ̤. les Amis de la patrie ; par le F. A. Marais,..
No full textAvec mode text
Potamonautes mariepskoppie Daniels & Barnes & Marais & Gouws 2021, sp. nov.
No full textPotamonautes mariepskoppie sp. nov. urn:lsid:zoobank.org:act: C0AE6C3E-5460-450C-87D4-87D24DC47862 Figs 1–6 Diagnosis Measurements for the holotype as follows: CL = 19.07mm; CWW = 26.76mm; CWP = 11.56 mm; FW = 11.58 mm; PFCD = 2.89 mm; CH = 10.63mm; MCPL = 16.44 mm; MCDL = 10.14 mm; P2ML = 11.06 mm; P2MW = 4.65 mm; P5ML = 9.34 mm; P5MW = 3.61 mm. CARAPACE. Highly arched (CH /CL = 0.55) postfrontal crest well-defined, complete, lateral ends meeting anterolateral margins; epigastric crests faint, median sulcus between crests short, not forked posteriorly; exorbital, epibranchial teeth reduced to granules; anterolateral carapace margin with no tooth on epibranchial (Fig. 2A–C). THIRD MAXILLIPED. Ischium with distinct vertical sulcus; s3/s4 complete, V-shaped, deep, midpoint almost meeting anterior margin of sterno-pleonal cavity; margins of s4 low, not raised (Fig. 2B). CHELIPED. Dactylus (moveable finger) slim, highly arched, enclosing oval interspace, with three larger teeth interspersed by smaller teeth along length; propodus (fixed finger) with four larger teeth interspersed by smaller teeth along length (Fig. 2C); carpus inner margin distal tooth large, pointed, proximal tooth reduced to granules; medial inferior margin of merus lined with series of small granules terminating distally at small, low distal meral tooth, lateral inferior margin smooth. G1 TERMINAL ARTICLE. 1/3 rd length of subterminal; first third straight in line with longitudinal axis of subterminal, middle part directed outward at 45°, widened by raised rounded ventral lobe, tip curving sharply upward (Fig. 3A–B). Etymology Named after Mariepskop since it occurs in close proximity to the mountain. The specific epithet is used as a Latin noun in apposition. Material examined Holotype SOUTH AFRICA – Mpumalanga Province • ♂; Blyde Canyon Nature Reserve, lowveld section, forest wetland; 24º42′36.36″ S, 30º54′11.664″ E; 733 m a.s.l.; 21 May 2021; H. Marais leg.; SAM A-094471. Paratype SOUTH AFRICA – Mpumalanga Province • 1 ♂; same collection data as for holotype except 17 Jun. 2020; SAM A-094472. Other material SOUTH AFRICA – Mpumalanga Province • 4 juvs; same collection data as for paratype; SAM A-094473. Description Based on the adult male holotype (CWW 26.76 mm). CARAPACE. Smooth with no tooth on the anteriolateral margins; widest anteriorly, narrowest posteriorly (CWP/CL 0.60); vaulted (CH /CL 0.55) (Fig. 2A); front broad, one-third of CWW (FW/CWW 0.43); urogastric, cardiac grooves distinct, other grooves faint or missing; postfrontal crest complete, anterolateral margin posterior to epibranchial corner finely granulated, epigastric crests faint, median sulcus between crests short, forked posteriorly; exorbital, epibranchial teeth each reduced to granules; anterolateral margin between exorbital, epibranchial teeth faintly granulated, curving slightly outward, lacking intermediate tooth (Fig. 2B–C); branchiostegal wall vertical sulcus faint, meeting longitudinal sulcus, dividing branchiostegal wall into 3 parts, suborbital, dorsal pterygostomial regions granulated, hepatic region smooth; suborbital margin faintly granulated. THIRD MAXILLIPED. Filling entire buccal frame, except for respiratory openings; exopod with long flagellum, ischium with faint vertical groove (Fig. 3D). Epistomial tooth large, triangular, margins lined by large granules. MANDIBLE. Palp two-segmented; terminal simple; tuft of setae at junction between segments. STERNUM. s1, s2 fused; s2/s3 deep, completely crossing sternum; s3/s4 complete, V-shaped, deep, midpoint almost meeting anterior margin of sterno-pleonal cavity; margins of s4 low, not raised. CHELIPED. Dactylus (moveable finger) slim, arched, with two teeth interspersed by smaller teeth along length; propodus (fixed finger) with two teeth interspersed by several smaller teeth along length (Fig. 4A–B), tips of both propodus and dactylus black; carpus distal tooth large, pointed, proximal tooth small but distinct, followed by granule; both inferior margins of merus lined with series of small granules, distal meral tooth small, pointed. PEREOPODS. Walking legs slender, 3 longest, 5 shortest; dorsal margins of pereopods with fine sharp bristles, dactyli of walking legs ending in sharp point, with rows of spine-like bristles. PLEON. Outline broadly triangular with straight margins. G1 TERMINAL ARTICLE. Short (1/3 length of subterminal), curving away from midline, first third straight in line with longitudinal axis of subterminal segment, middle part directed outward at 45°, widened by low raised rounded ventral lobe, tip curving gently upward. G1 subterminal broad at base, tapering to slim junction with terminal article distally where these two parts have same width, ventral side with heavily setose margins; with setae-fringed flap covering lateral half of segment; dorsal side smooth, no flap, with broad membrane on dorsal side of suture marking junction between terminal, subterminal parts (Fig. 3A–B). G2 TERMINAL ARTICLE. Long, flagellum-like, 0.5 times length of subterminal (Fig. 3C). Size A small-bodied species, CL = 19.07 mm, and wide, CWW = 26.76 mm. Colour in life Dorsal carapace chocolate brown with a glossy shine, while the chelipeds and ventral surface are light orange in colour (Fig. 5A). Distribution Known only from the lowveld section of the Blyde Canyon Nature Reserve, east of Mariepskop, Mpumalanga Province, South Africa. However, a digital photographic record from iNaturalist (posted by Werner Conradie) suggests the species is also present around Haenertsburg, in Limpopo Province, South Africa (Fig. 5B). Surveys of the latter area are required to confirm this observation. Ecology The type locality is located 12 km southeast of Mariepskop Mountain and forms part of the Great Drakensberg Mountain escarpment. The swamp forest receives annual rainfall averaging 1500 mm on top of the mountain and 750mm at the bottom (Ngwenya et al. 2019). The swamp forests in these areas are all channelled valley-bottom wetlands with connected seeps. The wetland of the type locality is on a shallow gradient that allows the water to seep out slowly into shallow channels and forms shallow muddy puddles, which the crab species prefers. Potamonautes mariepskoppie sp. nov., occurs sympatrically with P. sidneyi sensu stricto. The soils are predominantly organic soils of 15-100cm deep (Van Rooyen et al. 2020). The presence of large water berries, Syzygium cordatum, is diagnostic of these swamp forests. There are other wetland species present, such as Carex spicata-paniculata, Commelina benghalensis, Cyperus denudatus, Cyclosorus interruptus, Cyperus dives, Isolepis fluitans, Kyllinga odorata, Leersia hexandra, Persicaria decipiens, Selaginella kraussiana, Schoenoplectus brachyceras, Setaria megaphylla, Scleria transvaalensis and Thelypteris confluens. Remarks Potamonautes mariepskoppie sp. nov., can be distinguished from its two sister species, P. ngoyensis and P. ntendekaensis, using colour when alive. Potamonautes mariepskoppie sp. nov. has a chocolate brown carapace and orange chelipeds that vary to rust brown as does the specimen from Haenertsburg, Limpopo (Fig. 5B). Potamonautes ngoyensis has a pale-white carapace and chelipeds; P. Potamonautes ntendekaensis has a chocolate-coloured carapace with red pereopods; the entire animal fades to bright orange/red when preserved in absolute ethanol (Daniels et al. 2019). In addition, P. mariepskoppie sp. nov. is a small-bodied species (CWW = 26.76mm) with a highly arched carapace (CH /CL = 0.60), while P. ngoyensis is a large-bodied (CWW = 32.8 mm) and flat species (CH /CL = 0.50). Similarly, P. ntendekaensis is a large-bodied species (CWW = 37.56 mm), that is highly arched (CH /CL = 0.55). All three species appear to be narrow-endemic forest-dwelling species and are poorly collected based on current distribution records. Potamonautes mariepskoppie sp. nov. appears to be confined to swamp forest patches east of Mariepskop and possibly at Haenertsburg, Limpopo province, while P. ntendekaensis is endemic to the Ntendeka Wilderness (Ngome forest – representing Eastern Scarp forest) area of KwaZulu-Natal, and P. ngoyensis is endemic to the Ngoye forest, part of the greater IOCB forest of KwaZulu-Natal (Daniels et al. 2019). Phylogenetically, Potamonautes mariepskoppie sp. nov. is not closely related to the five other species that occur in Mpumalanga province and can also easily be distinguished from these. Both P. unispinus and P. calcaratus have a single tooth on the anterolateral carapace margin, which is nearly spike-like in P. calcaratus. In P. unispinus the tooth on the anterolateral margin is sharp, pointed and prominent, similar to the exorbital tooth, and the species is large (CL= 49.83mm) and broad (CWW = 64.88 mm). Potamonautes unispinus is a riverine species that is widespread in southern Africa and known from South Africa, Zimbabwe and Zambia (Stewart & Cook 1998), while P. calcaratus occurs exclusively around ephemeral pans in the Kruger National Park in South Africa, where it burrows into the clay sidewalls up to 1m (Daniels et al. 2002a). The latter species is also found in Mozambique and Zimbabwe (Reed & Cumberlidge 2004). Additionally, the chelipeds of P. calcaratus are highly modified and nearly flattened for burrowing. The latter species has a vaulted carapace, indicative of its semi-terrestrial mode of life (Daniels pers. obs). In Potamonautes warreni, the dentition on the anterolateral margin of the carapace varies from a single tooth to a series of five to ten teeth (Daniels 2001). Potamonautes warreni is a riverine species widespread in South Africa, Botswana and Namibia where it occurs in the Orange River and its major tributaries such as the Vaal River. Potamonautes flavusjo, a Mpumalanga Highveld endemic, is semi-terrestrial and occurs in vlei (wetland) and lake areas, where it burrows into peat soils (Daniel et al. 2014). This species has characteristic sulphur-yellow patches on its dorsal carapace surface and the ventral surface is bright yellow and the species has a highly vaulted carapace (CH /CL = 0.61) (Daniels et al. 2014). Potamonautes sidneyi sensu stricto is generally large-bodied (CWW> 52.4 mm) and the cephalothorax is flat (CH /CL = 0.54), while the anterolateral margins of the carapace are heavily granulated. The species is common in large rivers, streams and swamp habitats throughout KwaZulu-Natal, Mpumalanga, Gauteng, Limpopo, the North-West and Northern Cape provinces of South Africa (Barnard 1950; Peer et al. 2017; Daniels unpubl). The three remaining sister species to the clade containing P. mariepskoppie sp. nov. are all found in neighboring Southern African countries. Potamonautes gorongosa occurs at Gorongosa National Park in Mozambique, P. mutariensis occurs in the Zimbabwean Highlands and P. mulanjeensis occurs on Mount Mulanje in Malawi. Phylogenetically, P. mariepskoppie sp. nov. is distantly related to the two remaining swamp forest dwelling South African freshwater crab species, P. lividus and P. isimangaliso (Fig.1), although it does bear a superficial resemblance to these two species. Potamonautes lividus occurs in swamp forest patches in Eastern Cape province, at Dwesa Nature Reserve, Mazeppa Bay and Manubi State forest, and in the IOCB forests from Amatikulu Nature Reserve, Richards Bay, Empangeni, Tugela River Mouth, the University of Zululand campus, and Mapelane Nature Reserve in KwaZulu-Natal (Gouws et al. 2001; Daniels et al. 2020a). Potamonautes isimangaliso is confined to iSimangaliso Wetland Park in northern KwaZulu-Natal (Peer et al. 2015). Potamonautes lividus was originally described from Ficus and Barringtonia dominated forests, and the carapace of the species is blue or light blue (Gouws et al. 2001). Furthermore, the cephalothorax is ovoid with no epibranchial tooth and the carapace is highly vaulted (CH /CL = 0.64), indicative of a semi-terrestrial mode of life (Gouws et al. 2001). In P. isimangaliso, the cephalothorax is also ovoid, and the carapace is highly vaulted (CH /CL = 0.57) and light brown, maroon, purple or brown–black in colour (Peer et al. 2015). The species lives in ephemeral pans in sand forest where it burrows into the soil to a depth of 30–50 cm (Peer et al. 2015). Potamonautes mariepskoppie sp. nov., is distantly related to the undescribed species from Hogsback and the four mountain-living freshwater crab species from the Cape Fold Mountains (P. brincki, P. parvicorpus, P. parvispina and P. tuerkayi), and the three Great Drakensberg Escarpment species (P. clarus, P. depressus and P. baziya sp. nov). Taxonomic note H. Milne-Edwards (1853) described Thelphusa inflata from Durban, KwaZulu-Natal (formerly Port of Natal, Natal province). Barnard (1950) was of the opinion that Potamonautes inflatus is a variant of P. perlatus. In addition to Durban, Barnard (1950) also listed P. inflatus as being present at Belfast, Haenertsburg and Mariepskop in the former Transvaal province (notably, the last two localities are also where P. mariepskoppie sp. nov. occurs). Bott (1955) recognized P. inflatus as a junior subjective synonym of P. depressus, noting that the “type” is unknown or lost. Our phylogenetic results refute a close relationship between P. mariepskoppie sp. nov. and P. depressus. A search of the digital records of the Muséum national d’Histoire naturelle, Paris, France failed to identify the type specimen of P. inflatus, suggesting the holotype is lost. Similarly, an exhaustive search of the South African Museum of Natural History, Cape Town, failed to retrieve the material from Belfast, Mariepskop and Haenertsburg that Barnard (1950) assigned to P. inflatus. Researchers consider P. inflatus as an invalid taxon (Stewart et al. 1995; Gouws & Stewart, 2001; Ng et al. 2008).A recent redescription of P. sidneyi suggests that the type material was likely originally collected from the region of Port Natal (Peer et al. 2017). The original description of P. inflatus is inadequate to differentiate it from P. sidneyi. Considering the absence of type material for P. inflatus and its confusing taxonomic status, the species name a nomen nudum. In recent years, six freshwater crab species, P. dentatus, P. lividus, P. isimangaliso, P. danielsi, P. ntendekaensis and P. ngoyensis, have been described from KwaZulu-Natal. Apart from P. sidneyi, no other species occurs in close geographic proximity to Durban (Port Natal) (Stewart et al. 1995; Peer et al. 2015, 2017; Daniels et al. 2019). The specimens from Mariepskop are recognized as P. mariepskoppie sp. nov., rather than P. inflatus, to limit any potential future confusion.Published as part of Daniels, Savel R., Barnes, Aaron, Marais, Hannes & Gouws, Gavin, 2021, Surveys of Afrotemperate forests yields two new freshwater crabs (Decapoda: Potamonautidae: Potamonautes MacLeay, 1838) from South Africa, pp. 82-107 in European Journal of Taxonomy 782 on pages 86-95, DOI: 10.5852/ejt.2021.782.1591, http://zenodo.org/record/576988
Design and control of equalization tanks.
No full textIncludes bibliography.The objective of this investigation was to develop a control strategy for the operation of an equalization tank upstream of a waste water treatment plant which utilizes the available equalization hold-up volume in such a manner that it reduces, optimally, diurnal fluctuations in both influent flow and load rates. The influent to a wastewater treatment plant generally exhibits wide diurnal variations in both flow rate and concentration, and consequently in load rate (defined as the product of flow rate and concentration). Deviations of these parameters from steady state cause plant operating problems in areas such as aeration control (due to load rate fluctuations) settling tank overloading due to flow rate fluctuations) and/or over- or under-aeration which affects settling properties, and others
Book Review: Public Administration Dictionary
No full textBook Title: Public Administration DictionaryBook Author: William Fox & Ivan H. Meyer1995. viii + 139 pp. ISBN 0 70213219 5. Juta.
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