Microbial sulfate reduction with acetate: process performance and composition of the bacterial communities in the reactor at different salinity levels

Microbial sulfate reduction with acetate as carbon source and electron donor was investigated at salinity levels between 0.53 and 1.48%. The experiment was carried out in a 2.3-1 upflow anaerobic sludge blanket reactor inoculated with granular methanogenic sludge. A pH of 8.3, a temperature of 32 +/- 1 degrees C and a chemical oxygen demand (COD)/SO4(2-)-S ratio of 2 were maintained in the reactor throughout the experiment. Sulfate reduction and the composition of the dominant bacterial communities in the reactor were monitored. The results showed that a maximal conversion rate for SO4(2-)-S of 14 g l(-1) day(-1) and a conversion efficiency of more than 90% were obtained at a salinity level of 1.26-1.39%. A further increase in the salinity level led to reactor instability. Denaturant gradient gel electrophoresis of 16S rDNA fragments amplified by PCR from total bacterial DNA extracted from the inoculum and reactor sludge showed that salinity level had an impact on the composition of the bacterial communities in the reactor. However, no clear relationship was found between reactor performance and the composition of the dominant bacterial communities in the reactor.     

The structuring role of microhabitat type in coral degradation zones: a case study with marine nematodes from Kenya and Zanzibar

Nematode genus assemblages were identified from four locations in coral degradation zones (CDZs) along the African east coast: Watamu and Tiwi Beach (Kenya) and Matemwe and Makunduchi (Zanzibar). Three microhabitat types were distinguished: coralline sediment, coral gravel and coral fragments. Nematode community composition was comparable to that of other studies dealing with the same habitat. The presence of a common genus pool in CDZs was reflected in the considerable similarities between samples. The addition of coral fragments as a habitat for nematodes resulted in an increased importance of taxa typical for coarse sediments and large substrata. Local and regional turnover were of the same order of magnitude. The structuring effect of microhabitat type clearly overrode the effect on a local and regional scale. Differences in sediment characteristics were more important in structuring the nematode assemblages than differences between the coralline sediment and coral fragments. No effect related to the three-dimensional structure of coral fragments was found. Differences between nematode assemblages in the coralline sediment and on coral fragments were attributed to the exposed nature of the latter habitat, its large surface area and its microbial or algal cover. Differences in available food sources were reflected in nematode trophic composition.     

Nematode Community Structure along the Continental Slope off the Kenyan Coast,Western Indian Ocean

Metazoan meiofauna and in particular nematode densities, diversity, community structure were studied in relation to water depth (20 m, 50 m, 500 m, 1000 m and 2000 m) along four bathymetric transects in the Western Indian Ocean off the Kenyan coast. Nematode densities ranged between 276–944 ind./10 cm², which is comparable to values from other oligotrophic areas in the world. Densities was correlated with oxygen concentrations in the overlying water, since they were lowest at mid‐depth (500–1000 m) coinciding with the minimum oxygen level. Nematode community structure (at genus level) resembles communities found in temperate slope regions, which are also characterized by a low productivity. The community structure showed correlations with sediment composition, water depth and oxygen levels in the overlying water. Sediment composition was mainly important at the shelf where nematodes separated into a silty sediment‐dwelling community with high abundances of Daptonema, Dorylaimopsis, Terschellingia and Halalaimus, and a sandy sediment‐dwelling community characterised by high abundances of Microlaimus and Halalaimus. The genera Monhystera, Acantholaimus, Sabatieria, Molgolaimus and Halalaimus dominated the slope communities. The characteristic deep‐sea taxa, the monhysterids and Acantholaimus increased in relative abundance with increasing depth, to become dominant at the lower slope (2000 m). The upper (500 m) and mid‐slope (1000 m), which coincided with the lowest oxygen concentrations, were colonised by Sabatieria, a genus that is known to inhabit suboxic sediments. Diversity at the level of the genera showed an unimodal trend along the sampled gradient, with highest values at mid‐depth (500 m). Although the oxygen minimum at mid depths is much less pronounced than in adjacent areas, the results of this study suggest an impact on the present communities.     

Deep-sea nematodes from the Indian Ocean: new and known species of the family Comesomatidae

Twelve new and known species of the genera Sabatieria,Cervonema, Paramesonchium, Hopperia and Dorylaimopsis and one new genus, Kenyanema aredescribed from the Indian Ocean and S. pisinna Vitiello,1970 from the Mediterranean Sea. Sabatieria lucia sp. n.is characterised by short but distinct inner and setiformouter labial sensilla and long (4–5 µm or 30–33% hd)cephalic sensilla; S. conicauda Vitiello, 1970, ischaracterised by tiny inner and outer labial sensilla andsetiform cephalic ones and short and thick cylindrical tail;Sabatieria pisinna is characterised by short innerand outer labial sensilla, setiform (3µm long) cephalicsensilla, multispiral amphids with 3.25–3.5 turns and a tailwhich is conical in the anterior 2/3 and posterior 1/3cylindrical; Cervonema tenuicauda Schuurmans Stekhoven,1950, is characterised by anterior sensilla in twocircles which are equal in length (3µm long), multispiralamphids with 3–4 turns and located at 1.5 times hd from theanterior end, simple spicules one abd long and 6–7 fineprecloacal supplements; Cervonema minutus sp. n.characterised by an extremely attenuated anterior end,spiral amphids with 4–5 turns (80–90% cbd) and short,simple spicules (0.8 abd long); Cervonema gourbaulti sp.n. characterised by long (4–5 µm) labialand cephalic sensilla, spiral amphids with 5–6 turns(73–88% cbd) and an elongate crenate terminal pharyngealbulb; Paramesonchium mombasi sp. n. characterised bylong labial (5 µm) and cephalic (21 µm) sensilla thatare close together and wide amphids (80–90% cbd); Kenyanema monorchis gen. et sp. n. characterised bya head region narrower than the rest of the body, fourcephalic sensilla (3 µm long) and spiral amphids with1.5–2 turns; Hopperia indiana sp. n. characterised byshort conical anterior sensilla, arcuatespicules that have a velum and a gubernaculum with a longand sharp pointed apophysis; Dorylaimopsis coomansi sp.n. characterised by long (8–10µm) cephalic setae,cuticular punctation with lateral differention of irregularlyarranged dots at the pharyngeal region and 1–3longitudinal rows of dots posterior of the pharynx; spiculeswith a unique shape; Dorylaimopsis gerardi sp. n.characterised by short setiform labial and long (6–7 µm)cephalic sensilla, punctated cuticle with lateraldifferentiation of irregularly arranged dots at firstthen three or four irregularly arranged longitudinal rows atthe pharyngeal and tail regions and two regularly arrangedlongitudinal rows of dots on the rest of the body, aconico-cylindrical tail with a distinctly swollen tip;Dorylaimopsis variabilis sp. n. is characterised byshort labial and setiform cephalic sensilla (33–58% hd),multispiral amphids with three turns, cuticular punctationswith lateral differentiation of three longitudinalrows at the pharyngeal and tail regions and two longitudinalrows on the rest of the body, spicules that are thin andslightly arcuate. The position of S. pisinna accordingto the grouping of Platt, 1985 of Sabatieriaspp. is also discussed. Kenyanema monorchis representsthe first monorchic species in the family.     

Papillonema danieli gen. et sp.n. and Papillonema clavatum (Gerlach, 1957) comb.n. (Nematoda,Desmodoridae) from the Ceriops mangrove sediments of Gazi Bay,Kenya

A new genus, Papillonema gen.n., is erected to accomodate the two species P. danieli gen. et sp. n. and P. clavatum (Gerlach, 1957) comb.n. from intertidal sediments of a tropical mangrove. Papillonema gen.n. is characterized by prominent papilliform labial sensillae, an elongate muscular terminal bulb (up to 60% of pharyngeal length), and three precloacal supplements. Comments are given on the use of the terms head capsule, head region, and cervical setae.Abbreviations a: body length divided by maximum body diameter - abd: anal body diameter - amph %: diameter of the amphid as a percentage of the corresponding head diameter - aw: amphidial width - b: body length divided by pharyngeal length - bdcs: body diameter at level of the cephalic setae - bdnr: body diameter at level of nerve ring - c: body length divided by tail length - cs: length of cephalic setae - da: distance from anterior to anus - dcs: distance from anterior edge to cephalic setae - dnr: distance from anterior edge to nerve ring - dv: distance from anterior to vulva - gub: length of the gubernaculum - hw: head width - L: body length - Isp: length of sperm cells - mbd: maximum body diameter - mbd ph: body diameter at level of pharynx - ph: pharyngeal length - spic: length of spicules measured along the arc - t: tail length - tmr: length of non-annulated tail end - V: position of vulva as a percentage of the total body length from anterior - wsp: width of sperm cells     

Acantholaimus (chromadoridae:nematoda) from the Indian Ocean: description of seven species

Seven species of the Acantholaimus aredescribed. Acantholaimus vermeuleni sp.n. ischaracterised by labial and cephalic sensilla thatare located at the same level, two post amphidialsetae on the dorso-lateral side and a poorlydeveloped stoma without distinct teeth. Acantholaimus verscheldi sp.n. is characterised bya narrow elongate pharyngeal region, a long stomawith distinct teeth and short (4–7 µm) cephalicsensilla. Acantholaimus heipi sp.n. ischaracterised by a narrow elongate pharyngealregion, well developed teeth in the stoma and longcephalic sensilla (11–13 µm). Acantholaimuselegans Jensen 1988 has a narrow anteriorpharyngeal region that increases in lengthposteriorly, it has setae before and after theamphids on both sides and stoma with well developedteeth. Acantholaimus gathumai sp.n. ischaracterised by long cephalic (10–15 µm) andsomatic (8–10 µm) setae and lateraldifferentiation with fine dots (5–7 µm inwidth). Acantholaimus geraerti sp.n. has longcephalic sensilla (15–19 µm) and narrow (4–6 µm)distinct lateral differentiation. Acantholaimusinvaginatum sp.n. is characterised byvery long cephalic setae (16–21 µm), severalsetae at the pharyngeal region and wide lateraldifferentiation with fine dots, often the stoma isinvaginated. Distribution of the different species of Acantholaimus encoutered in the four transectsstudied is also described.     

Chromadoridae (Chromadorida: Nematoda) from the Indian Ocean: Description of new and known species

Hydrobiologia - Seventeen new and known species of the familyChromadoridae are described. The genus Dichromadora is represented by five species. Dichromadora longicaudata sp.n. is characterised bya...     

Chromadoridae (Chromadorida: Nematoda) from the Indian Ocean: Difficulties in morphological identification of Actinonema Cobb, 1920 and Rhips Cobb, 1920.

The diagnostic characteristics of ActinonemaCobb, 1920 and Rhips Cobb, 1920 are reviewed andtheir importance for genera diagnosis assessed. Threespecies of Actinonema and one species of Rhips are described. Actinonema longicaudatumSteiner, 1918 is characterised by short (2–3 µmlong) anterior sensilla, cylindrical body with arather narrow anterior end, lateral alae with invertedV-patterns, wide (70–75 of cbd) double amphids andaccessory pieces composed of only the telamon which isbroad anteriorly and tapers on the posterior and along tail. Actinonema paraceltica ischaracterised by long (4–5 µm) anterior sensilla,large amphids (83–88% of cbd), lateraldifferentiation of V pattern on each annule andaccessory pieces with telamons that have shortextensions. Actinonema smolae sp. n. ischaracterised by long and thin body, large amphidslocated close to the anterior end and six solid cones.Rhips reginae n.sp. is characterised by sixsolid cones, large (90% cbd) amphids, lateraldifferentiation of two longitudinal rows of dots anddouble jointed spicules.