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1.
R. Fisher  M.J. Sheaves 《Hydrobiologia》2003,495(1-3):143-158
The spatial variability in the community structure of infaunal free-living marine nematodes of pioneer seagrass (Halophilaand Halodule) meadows within a deltaic mangrove estuarine system and a bay mangrove system in tropical north-eastern Australia were examined. Nematode mean densities were intermediate ranging from 609 to 2744 inds./10 cm2. A total of 152 putative species from 94 genera and 22 families were found across the four sites. The communities exhibited a high degree of dominance by Terschellingia longicaudata, Catanema sp 1, Terschellingia sp 2 and Metalinhomoeus insularis.Non-metric multi-dimensional scaling (nMDS) revealed that intra-site variability was low. This was reinforced by 1-way MANOVA, showing no significant inter-station differences between the six most dominant species at each site. The main system difference was reflected by a greater percentage of the Desmodoridae combined with a reduction of the Linhomoeidae in the bay system. At a species level system differences were manifested by a stenohaline, brackish water nematode assemblage in the deltaic system (M. insularis, Terschellingoidessp 1, Pseudolellasp 1) and, by a stenohaline, marine nematode assemblage in the bay system (Catanema sp 1, Spirinia parasitifera, Actinonemasp 1). These communities represent `hotspots' of diversity within a wider, mangrove-influenced depauperate fauna. The high degree of dominance found in each community was countered by moderate diversity and this, combined with the high number and speciation of deposit-feeding species, suggests that nematodes were more abundant in the meadows due to the abundance of microbial food. Notwithstanding the different salinity/CaCO3 regimes, these communities exhibit both intra- and inter-site homogeneity with dominance by a conservative, deep-dwelling guild. The fact that this homogeneity exists suggests that these small-bladed seagrass species may play a greater role (sediment stability, fine particle settlement, organic detritus) in influencing the infaunal nematode community than was previously thought.  相似文献   
2.
1. The effects of eutrophication on phytoplankton, zooplankton and fish in lakes are well known. By contrast, little is known about the response of the zoobenthos to nutrient enrichment, while smaller organisms, such as the meiofauna, have for the most part been neglected. 2. In a long‐term (16 months) microcosm experiment, we assessed the effects of five levels of nutrients [total phosphorus (TP), 7–250 μg L?1; nitrate, 2–8 mg L?1] on a freshwater meiofaunal assemblage and on nematode diversity in particular. 3. Within the first 8 months, meiofaunal succession was only weakly affected, whereas, during the last 4 months, nutrient addition influenced most of the main taxa, with a concomitant change in the assemblage structure. 4. The density of the numerically dominant nematodes decreased upon nutrient enrichment, whereas ostracods became more numerous. Other taxa, including copepods, reached a maximum at intermediate nutrient levels or, in case of oligochaetes, were almost unaffected by nutrient enrichment. However, the changes in the density of the main taxa were usually insufficient to alter their biomass. Consequently, meiofaunal biomass was remarkably unresponsive to nutrient addition, while meiofaunal density displayed a unimodal relationship, with a peak at a TP concentration of 30 μg L?1. In addition, nematode species richness decreased significantly with increasing nutrient concentrations. 5. We hypothesise that the response of meiofaunal taxa to nutrients is attributable to the development of primary producers, which shifted with enrichment from low densities of edible diatoms and unicellular green algae to large standing stocks of inedible forms, such as Lemna minor and Cladophora spp.  相似文献   
3.
  1. This model of stream epilithic biofilm biomass dynamics is based on the system of equations from Uehlinger et al. ( 1996 ) and the term for autogenic detachment of biofilm from Boulêtreau et al. ( 2006 ). Its new features are (i) a mathematical term based on estimated feeding activity of biofilm‐dwelling invertebrates, (ii) local hydrodynamics considered as the principal factor governing algal traits and biofilm structure and (iii) a variable degree of parameterisation that was adjusted to biofilm biomass conditions.
  2. Biofilm biomass was monitored over a one‐year period in the Garonne river in France (September 2008–2009). An allometric approach was used to estimate the feeding activity of biofilm‐dwelling invertebrates based on their energetic requirements. Diatom functional diversity was also monitored to find how it varied with overall biofilm growth patterns. The one‐year monitoring period was divided into six biofilm biomass cycles, with each cycle consisting of a phase of biofilm growth as the main process, followed by detachment.
  3. This model reproduced the observed data as a complex of biofilm growth/detachment cycles using different sets of empirical parameters which allowed (i) the dominant processes involved in each biofilm cycle to be evaluated and (ii) the six cycles of biofilm growth/detachment to be reproduced. This accounted for the observed patterns more effectively than a parameterisation using a single set of empirical parameters.
  4. High flow had a severe effect on biofilm dynamics through chronic and catastrophic detachment. Presumably as a result, assemblages of diatoms shifted towards species that were firmly attached and protected by mucilage.
  5. During low flow (and when temperature was high), biofilm dynamics was mainly affected by autogenic detachment and grazer activity. The grazing pressure of the dominant biofilm‐dwelling invertebrates (Nematoda and larvae of Chironomidae and Trichoptera) was fairly low (a maximum of 6% of biofilm biomass ingested daily); nevertheless, their presence in the biofilm seemed to favour biofilm autogenic detachment.
  相似文献   
4.
Aim Pockmarks are craters on the sea floor formed by sub‐sea‐floor fluid expulsions, which occur world‐wide at all ocean depths. These habitats potentially host a highly specialized fauna that can exploit the hydrocarbons released. Pockmarks at relatively shallow depths can be easily destroyed by human activities, such as bottom trawling. In the present study, we investigated the combined effects of sea‐floor heterogeneity, rate of fluid emission and trophic conditions of different pockmarks on the biodiversity of the deep‐sea assemblages. Location Continental slope of the Gulf of Lions, western Mediterranean Sea, at water depths from 265 to 434 m. Methods We investigated the biodiversity associated with sea‐floor pockmarks that are both inactive and that have active gas emissions. Control sites were selected on the sea floor outside the influence of the gas seepage, both within and outside the pockmark fields. We examined the combined effects of: (i) sea‐floor heterogeneity; (ii) variable levels of fluid (gas) emissions; and (iii) trophic characteristics of the meiofaunal assemblage structure and nematode diversity. Results Sediments within the pockmark fields had lower meiofaunal abundance and biomass when compared with the surrounding sediments that were not influenced by the gas seepage. Although several higher taxa were absent in the pockmarks (e.g. Turbellaria, Tardigrada, Cumacea, Isopoda, Tanaidacea, Nemertina and Priapulida, which were present in the control areas), the richness of the nematode species within all of these pockmarks was very high. About 25% of the total species encountered in the deep‐sea sediments of the investigated areas was exclusively associated with these pockmarks. Main conclusions We conclude that both active and inactive pockmarks provide significant contributions to the regional (gamma) diversity of the continental slope in the western Mediterranean Sea, and thus the protection of these special and fragile habitats is highly relevant to the conservation of deep‐sea biodiversity.  相似文献   
5.
Janet W. Reid 《Hydrobiologia》1987,153(2):121-138
Eight species of cyclopoid copepods were recorded from 1979–1983 in the complex microhabitats of a wet campo (campo úmido) marsh in central Brazil. Ectocyclops herbsti and Paracyclops fimbriatus occurred most often in areas with water covering the soil; Muscocyclops therasiae n. sp. occurred mainly in soils with no surface water; while Metacyclops campestris n. sp. showed no distinct microhabitat preference. Occurrence of the remaining four species was too sporadic to determine microhabitat preference. Paracyclops carectum n. sp., Metacyclops campestris n. sp., Muscocyclops therasiae n. sp., Muscocyclops bidentatus n. sp. and Ponticyclops boscoi n. g. n. sp. are described. A key to the New World species of Metacyclops s. str. is provided.  相似文献   
6.
Creer S  Sinniger F 《Molecular ecology》2012,21(5):1033-1035
Deep sea environments cover more than 65% of the earth’s surface and fulfil a range of ecosystem functions, yet they are also amongst the least known habitats on earth. Whilst the discovery of key geological processes, combined with technological developments, has focused interest onto geologically active areas such as hydrothermal vents, most abyssal biodiversity remains to be discovered ( Danovaro et al. 2010 ). However, as for terrestrial reservoirs of biodiversity, the world’s largest biome is under threat from anthropogenic activities ranging from environmental change to the exploitation of minerals and rare‐earth elements ( Kato et al. 2011 ). It is therefore important to understand the magnitude, nature and composition of deep sea biological communities to inform us of levels of local adaptation, functionality and resilience with respect to future environmental perturbation. In this issue of Molecular Ecology, Bik et al. utilize 454 Roche metagenetic environmental sequencing to assess microbial metazoan community composition and phylogenetic identity across deep sea depth gradients and between ocean basins. The analyses suggest that although the majority of microbial eukaryotic taxa are regionally restricted, a small percentage might maintain cosmopolitan deep sea distributions, and an even smaller fraction appear to be eurybathic (live across depth gradients).  相似文献   
7.
Diel temperature patterns are changing because of global warming, with higher temperatures being predicted to be more pronounced at night. Biological reactions are temperature dependent, with some occurring only during the daylight hours (e.g., light photosynthesis) and other during the entire day (e.g., respiration). Consequently, we expect the modification of daily temperature cycles to alter microbial biological reactions in stream sediments. Here, we aimed to study the effect of warming and changes of the diel temperature patterns on stream sediment biofilm functions tied to organic carbon decomposition, as well as on biofilm meiofaunal community structure. We performed an eight‐week experiment with 12 artificial streams subjected to three different diel temperature patterns: warming, warmer nights and control. Significant effects of warming on biofilm function and structure were mainly detected in the long term. Our results showed that warming altered biofilm function, especially in the warmer nights’ treatment, which enhanced β‐glucosidase enzyme activity. Interestingly, clear opposite diel patterns were observed for dissolved organic carbon and β‐glucosidase activity, suggesting that, at night, sediment bacteria quickly consume the input of photosynthetic dissolved organic carbon labile compounds created during light‐time. The biofilm structure was also altered by warming, as both warming and warmer night treatments enhanced copepod abundance and diminished abundances of turbellaria and nematodes, which, in turn, controlled bacterial, algal and ciliate communities. Overall, we conclude that warming has strong effect on sediment biofilm structure and enhanced microbial organic matter degradation which might, consequently, affect higher trophic levels and river carbon cycling.  相似文献   
8.
于2015年4月(春季)、2015年6月(夏季)、2015年10月(秋季)、2016年1月(冬季),在海南东寨港红树林保护区潮间带进行多次采样,分选小型底栖动物,并测定沉积物中有机质和叶绿素a含量,分析不同季节东寨港红树林小型底栖动物丰度与有机质、Chla的相关性。研究结果,沉积物中小型底栖动物主要包括自由生活线虫、桡足类、涡虫、多毛类、寡毛类,线虫为优势类群;有机质含量为25.22%—93.41%,平均值为46.6%; Chla含量为0.188—6.303μg/g,平均值为1.731μg/g。相关性分析显示,春季小型底栖动物的丰度和Chla含量呈显著正相关(Pearson's r=0.684; P0.05),夏季小型底栖动物的丰度与有机质含量呈显著负相关(Pearson's r=-0.518; P0.05)。  相似文献   
9.
Macrodasyidan gastrotrichs are hermaphrodites with complex reproductive organs that function in sperm transfer and receipt, but homology among the organs of members of different clades remains undetermined, as does a broader understanding of evolutionary trends in the reproductive biology of macrodasyidans. In this study, we investigate the evolution of reproduction in Urodasys, a clade of 15 macrodasyidan species that shows variability in reproductive mode (hermaphroditic and parthenogenetic) and sexual anatomy. We use partial 18S rDNA sequence data from 30 specimens representing five described species, sequence data from one undescribed species in GenBank, and sequence data from a potentially new species found at Capron Shoal, Florida, to gain insight into the phylogeny of the clade and clarify evolutionary trends in reproductive modality. Based on a total of 33 specimens of seven potential species, we found that members of Urodasys can be separated into three clades reflective of different reproductive modalities: Clade I, species with paired male and female gonads but without accessory sexual organs; Clade II, species with a single left testis, paired ova, and accessory organs including a sclerotic stylet; and Clade III, parthenogenetic species without testes or accessory organs. In addition, we find that the potentially new species from Florida can form spermatophores, a condition shared with another species in Clade I. Herein, we describe this novel spermatophore‐bearing species and discuss the significance of spermatophore formation in the genus.  相似文献   
10.
A new species of marine Gastrotricha from Brazil is described and discussed. Ptychostomella lamelliphora sp. n. is one of the several new taxa that were found during an extensive survey of the gastrotrich fauna carried out in 2002 and 2003 along the coastline of the State of São Paulo. The new species is unique in that it possesses cuticular ornamentations in the form of plate-like structures (scales) along the lateral borders of the body and two massive clusters of densely packed adhesive tubes on the ventral surface, near the ano-genital opening. Both these features appear to be adaptations to challenge the high energy waters that characterize the species’ microhabitat: the coarse sublittoral sand in the channel between the mainland and the largest island in the State, Ihlabela. Additionally, a key to the described Ptychostomella species of the world is provided.  相似文献   
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