Habitat diversity and fish assemblages in an African river basin (Nyagui River, Zimbabwe)

Little is known about the ecology of stream fishes in Zimbabwe and this study investigated fish communities in the Nyagui River basin and is one of the first to examine the relationship between fish assemblages and habitat diversity in Zimbabwe. Fourteen sampling stations were, for convenience, divided into three groups; upper (>1400 m above sea level), middle (1000–14000 m) and lower stations (<1000 m). A total of 24 species were collected, four of which were introduced, and the species composition differed according to the location of the stations. Species that favoured running water and/or rocks were generally absent from the upper stations, reflecting the fact that they were mostly sandy‐bottomed and still. Diversity and relative abundance increased in the mid‐ and low‐altitude stations, which were rockier and faster flowing. Both species diversity and relative abundance increased with the catchment area above each station, which was attributed to increased habitat diversity in larger streams. This view was supported by a strong correlation between habitat diversity and catchment area, and between habitat diversity and species richness and relative abundance. At present, the Nyagui system is relatively unregulated but the Kunzvi Dam, presently under construction, will change this situation and species diversity is likely to decrease owing to the loss of rheophilic species while other groups, notably cichlids and introduced species will increase.     

Temporal and spatial structure in the suprabenthic community of a shallow estuary (western Portugal: Mondego river estuary)

The suprabenthic fauna of the Mondego river estuary (western Portugal) was sampled monthly between June 1996 and June 1997. Quantitative samples were taken, with a suprabenthic 500-μm mesh size net, at regularly spaced stations covering the entire south arm of the estuary. The diversity of the samples and the distribution of the species were assessed. Suprabenthic communities were identified using a divisive multivariate statistical technique and species composition, density and biomass of the dominant species of each community were compared among communities. Diversity was highest in the mouth of the estuary where density and biomass were lowest. Diversity decreased upstream and was lowest in the mid and inner estuary where density and biomass reached maximal values. Suprabenthic animals, mainly the mysid Mesopodopsis slabberi, reached high densities in inner and upstream stations, whereas the more seaward stations had lower densities but a higher number of species. The spatial patterns dominated over the temporal patterns.     

Preliminary study of fish community structure in Amanos Mountain streams (Hatay-Turkey)

Fish diversity and distributions in 33 streams of the Amanos Mountains were investigated between December 2002 and November 2003. Some physical and chemical parameters, such as water temperature, dissolved oxygen, electrical conductivity, pH, and velocity of the streams were measured periodically at each site. The study area was grouped into three regions: AS (Asi Basin), IS (?skenderun Gulf) and CE (Çevlik region). Fish abundance and Shannon Diversity Index were computed for each region. CE region was the poorest compared to the others in terms of fish abundance and diversity. A total of nine species in four families (Cyprinidae, Balitoridae, Anguillidae, Blenniidae) were recorded and all species collected were found to be indigenous. Capoeta barroisi (42.2%) and Garra rufa (33.3%) were the most common and abundant species and Salaria fluviatilis (0.4%), Carasobarbus luteus (0.9%), Anguilla anguilla (1.0%) and Alburnus sellal (1.2%) were the most rarely encountered species in the Amanos Mts. The endangered species Alburnus orontis is also rarely found. Fish diversity was greater in perennial streams (0.62) than in intermittent streams (0.27). There are many adverse human impacts on fish fauna in the Amanos Mountain streams; however, numbers of intermittent streams impose the greatest threat to fish in the Amanos Mts.     

Spatial and temporal abundance,substrate partitioning and species co-occurrence in a guild of Neotropical blackflies (Diptera: Simuliidae)

Blackfly larvae were sampled monthly from two smallNeotropical mountain streams 500 m apart from each other in northernVenezuela during a 15-month period, and ten habitat variables weremeasured at two altitudes (800 and 900 m) to determine local spatialand temporal variations in abundance, stream variables, speciesco-occurrence, and substrate preference within the blackflyguild. The blackfly species composition of each stream was the same,with five species (in order of abundance): Simulium ochraceumWalker s.l., S. paynei Vargas, S. metallicum Bellardicytospecies E, Simulium sp., and S. horacioi Okazawa &Onishi. There were clear differences in community structurebetween streams (not among altitudes), although S. ochraceums.l. was the most abundant species in both habitats. Principal component andcorrelation analyses revealed that structural (great depth, width,flow, and discharge) and chemical (low conductivity) factors werethe stream variables best associated to the spatial distribution ofmost blackfly species. Blackfly abundance was greater in the largerstream. Larvae were most abundant on submerged rocks and fallenleaves, although the patterns of substrate use within the guildrevealed substrate partitioning among most blackfly species.There was one general annual peak of abundance at the end of therainy season. We suggest that blackfly community structure in theseNeotropical headwaters streams, over the small spatial scaleexamined here, is largely influenced by interactions among streamsize and velocity-related factors (width, streamflow, discharge andsubstrate availability-stability) and the rainfall regime.     

Seasonal distribution and prevalence of dung beetles (Coleoptera: Scarabaeidae) in Kurukshetra,Northern India

A total of 8306 individuals as 29 species from 3 subfamilies (Hybosorinae, Aphodiinae, Scarabaeinae) were trapped by pitfall bait trapping. The maximum number of species of Scarabaeinae (68.97%) and number of individuals of Aphodiinae (56.84%) take part in the formation of a community. The number of species, number of individuals, diversity and dominance changes throughout the season. Seasonal prevalence of 82.76% of species and 50.81% of individuals was found in June. Aphodius campestris was found to be more attracted to the pitfall bait traps. The beetle community found in May shows the maximum Shannon's Diversity Index (2.46) but Margalef's Diversity Index was highest in August (3.06). Environmental factors play an important role in the occurrence and abundance of dung beetles. In the present study non-significant but positive correlations between temperature and species richness, abundance and diversity were found. Percent relative humidity showed a positive correlation with abundance only, and negative correlations with species richness and diversity.     

The relationship between the exotic predators Micropterus salmoides and Serranochromis robustus and native stream fishes in Zimbabwe

Samples of fish were collected from 42 stations in streams around Harare, Zimbabwe. The total abundance of fish was lower by 50% or more at stations where the exotic predators Micropterus salmoides and Serranochromis robustus were present compared with stations where they were absent. The greatest differences in density occurred among small Barbus species, whose populations were 86% lower ( S. robustus alone) and 99% lower ( M. salmoides alone). Populations of small rock and sand catlets were less dense when S. robustus , but not M. salmoides , was present probably because the latter did not enter the riffles where the catlets live. These predators apparently did not affect densities of certain other species in the system that were either cryptic, bottom-dwelling forms or too large. Low Barbus diversity and abundance in streams containing exotic predators is of concern because this group of fluvial fishes is threatened throughout southern Africa by dam-building, pollution, and other factors.     

Peracarid composition,diversity and species richness in the area of the Northeast Water polynya,East Greenland (Crustacea,Malacostraca)

During the ARK XI-2 expedition with RV Polarstern in September/October 1995, a transect of epibenthic sledge (EBS) samples was taken in the area of the Northeast Water Polynya off the Greenland coast, from the shelf down into the deep sea. A total of 85,304 specimens of Peracarida were collected at seven stations. These individuals comprised 45 families, 103 genera and 180 species. With regard to abundance, Cumacea occurred with highest numbers, 31,269, followed by Isopoda, Amphipoda, Mysidacea and Tanaidacea. Species richness was highest in Amphipoda with 94 species, followed by Isopoda with 43 species, Cumacea with 20 species, Tanaidacea with 15 and Mysidacea with 8 species. Species richness was highest at the shallowest station 37-016 and lowest at the deepest station 37-021, whereas the opposite pattern was found for abundance. Diversity and eveness were highest at the southernmost station and lowest at the deepest station. Amphipoda occurred more frequently at the shallower stations, while Cumacea were very frequent at the deepest station. Numbers of species were lowest for Cumacea at the deepest station, while Amphipoda and Isopoda generally occurred with high species richness at all stations. On the basis of the species composition stations were compared.     

Community structure and species diversity of Harpacticoida (Crustacea: Copepoda) at two sites in the deep sea of the Angola Basin (Southeast Atlantic)

The aim of this study was to evaluate compositional differences between harpacticoid (Crustacea, Copepoda) assemblages at two widely separated abyssal locations. During the DIVA 1 cruise of RV METEOR (July/August 2000) to the Angola Basin (Southeast Atlantic), two deep-sea stations, approximately 300 nautical miles apart (Stations 325 and 346), were sampled repeatedly by Multicorer (MUC). For quantitative analyses, 5 MUC samples were selected at random from each of 15 deployments at both stations, totalling 75 cores. Across the study, 7,081 Harpacticoida specimens were encountered and of these 31.4 % were adults and could be analysed to species level: 682 species were identified, with 99.3 % new to science. At northern Station 346, a total of 600 species were recorded—the highest harpacticoid species number ever recorded for a single deep-sea locality. Most species (56 %) were represented by singletons. Multivariate tests identified significant differences between community compositions at the two stations. Diversity, species richness and species density were higher at Station 346, whilst taxonomic distinctness, evenness, and rarefaction were similar between stations. Regression and correlation analyses showed that the difference in species diversity was best explained by species densities rather than species richness. Under-sampling due to low densities was an issue at the southern Station 325. Nevertheless, our study demonstrated significant differences in regional-scale harpacticoid community structures within a single deep-sea basin that would usually be considered a uniform and stable habitat. These observed differences are thought to reflect differences in food availability at the two stations.     

Some distributional characteristics of small zooplankton at two stations in the Otranto Strait (Eastern Mediterranean)

The qualitative composition, numerical abundance and vertical distribution of protozoan and microcopepod communities were studied in the Otranto Strait at two stations during five cruises from August 1986 to May 1990. The samples were collected with a plankton net of 53-m mesh size equipped with a closing system in six or seven vertical layers. The principal component analysis (PCA) was used to analyse the spatial and temporal variability of small zooplanktonic assemblages. Data are presented for 36 species of radiolarians, 46 tintinnines and for 22 oncaeid copepods. Differences between the eastern shore and the western shore were not significant, according to the PC analysis of the total density values for all assemblages. However, on the basis of the distribution of PC loadings, it was possible to distinguish three vertical layers whose variability contributes in different amounts to the total variability in the small zooplankton community at both stations. The water masses have crucial significance for the spatial and seasonal distribution of all assemblages. Each type of water mass is connected by the presence of characteristic species.     

Diversity and distribution of Odonata (Insecta) larvae along an altitudinal gradient in Coalcomán mountains, Michoacán, Mexico

Evaluating components of landscape diversity is essential for the implementation of efficient conservation strategies. We evaluated the diversity of Odonata larval assemblages from the Coalcomán mountains (CM), Michoacán, Mexico, and related it to local (site-level) habitat variables. Larvae were collected from shores, riffles and pools in five streams, counted and identified to species, twice per season during 2005. The Shannon Diversity Index (H'), Margalef's Richness Index (R), Simpson's Index as a dominance measure (D) and Pielou's Equitability (J) were used to describe the assemblages, and Renyi's Diversity Profiles were used to order diversity. A Bray-Curtis Similarity Index (BC) was used to evaluate beta diversity. Theoretical richness was estimated using non-parametric and parametric methods. A Canonical Correspondence Analysis (CCA) was applied to explore the relationships of species with site-level environmental variables. A total of 12 245 larvae from 75 species, 28 genera and 8 families were recorded. Over all sites, the dominant species were Erpetogomphus elaps, Macrothemis pseudimitans and Argia pulla. The number of species per locality ranged from 18 to 36, and a high number of species (76%) occurred with relative abundances lower than 1%. A differential distribution of species and abundance in streams, time and strata was observed. Renyi's diversity profiles showed diversity was higher in spring and on shores. Most BC similarity values were smaller than 25%, indicating a high turnover rate in the CM. The high turnover rate reflects a differential distribution of the species along the altitudinal gradient, supporting the hypothesis of Mexico as a betadiverse country. According to the slope of Clench's curve, a reliable list of species was gathered. The CM larval assemblage is currently the largest reported for Mexico, and our results support previous proposals of the CM as a species-rich area for conservation.     

Fragilariopsis cylindrus (Grunow) Krieger: The most abundant diatom in water column assemblages of Antarctic marginal ice-edge zones

Summary Planktonic diatoms were sampled in the ice-edge zone of the Bellingshausen Sea during the early austral spring of 1990 and of the Weddell Sea during the late spring of 1983, the autumn of 1986, and the winter of 1988. The four cruises in the Antarctic marginal ice edge zones, combined with the summer cruise in Prydz Bay during a brief ice-free period (1988) provided us with opportunities for spatial and seasonal studies of diatom abundance and distribution in the water column. Cells from discrete water samples from 73 stations near the marginal ice-edge zones during all seasons were counted to gain quantitative information on the composition, abundance, and distribution of diatoms. Diatom abundance was dominated by the pennate diatom, usually nanoplanktonic, Fragilariopsis cylindrus (Grunow) Krieger, during all five cruises. The highest integrated numbers of F. cylindrus were found during the summer cruise with 7.9 × 10¹⁰ cells m^–2 and the lowest numbers were found during the winter cruise with 1.1 × 10⁸ cells m^–2. The average integrated abundance of F. cylindrus from the five cruises was about 35% of the total diatom abundance. The overall spatial pattern of F. cylindrus near the marginal ice-edge zones during the five seasonal cruises were similar with the highest number of cells in open waters compared to ice-covered waters. When all 73 stations during the five cruises were included in the correlation analysis, the abundance of total diatoms was positively correlated with the abundance of F. cylindrus, suggesting that the ice-edge pulses of diatom assemblages in the water column largely reflected its abundance. Cluster analysis revealed that the stations in marginal ice-edge zones were not only separated by seasons and locations, but they also separated based on location of stations in relation to the ice edge (open water stations vs. ice-covered stations).     

Diversity and similarity of butterfly communities in five different habitat types at Tam Dao National Park, Vietnam

Diversity and similarity of butterfly communities were assessed in five different habitat types (from natural closed forest to agricultural lands) in the mountains of Tam Dao National Park, Vietnam for 3 years from 2002 to 2004. The line transect count was used to record species richness and abundance of butterfly communities in the different habitat types. For each habitat, the number of species and individuals, and indices of species richness, evenness and diversity of butterfly communities were calculated. The results indicated that species richness and abundance of butterfly communities were low in the natural closed forest, higher in the disturbed forest, highest in the forest edge, lower in the shrub habitat and lowest in the agricultural lands. The indices of species richness, evenness and diversity of butterfly communities were low in agricultural lands and natural closed forest but highest in the forest edge and shrub habitats. The families Satyridae and Amathusiidae have the greatest species richness and abundance in the natural closed forest, with a reduction in their species richness and abundance from the natural closed forest to the agricultural lands. Species composition of butterfly communities was different among five different habitat types (40%), was similar in habitats outside the forest (68%) and was similar in habitats inside the forest (63%). Diversity and abundance of butterfly communities are not different between the natural closed forest and the agriculture lands, but species composition changed greatly between these habitat types. A positive correlation between the size of species geographical distribution range and increasing habitat disturbance was found. The most characteristic natural closed forest species have the smallest geographical distribution range.     

The distribution of ciliates on Ecology Glacier (King George Island, Antarctica): relationships between species assemblages and environmental parameters

Ciliates are important consumers of pico- and nano-sized producers, are nutrient regenerators, and are an important food source for metazoans. To date, ecological research on ciliates has focused on marine ecosystems rather than on glacier habitats. This paper presents the first major study on ciliates from the Ecology Glacier (South Shetland Islands, Antarctica). The objective of the study was to investigate the structure and spatial distribution of ciliate communities and to identify the environmental factors determining the structure of the assemblages. Microbial communities were collected from three habitats: surface snow, cryoconite holes, and glacier streams. Sampling was carried out every 3–4 days from January 17 to February 24, 2012. A total of 18 ciliate taxa were identified. The species richness, abundance, and biomass of protozoa differed significantly between the stations studied with the lowest numbers in streams on the glacier surface and the highest numbers in cryoconite holes. The RDA performed to specify the direct relationships between the abundance of ciliate taxa and environmental variables showed obvious differences between studied habitats. The analysis showed that all variables together explained 62.4 % of total variance. However, variables that significantly explained the variance in ciliate communities in cryoconite holes, snow, and surface streams were temperature, conductivity, and total nitrogen. Further research is required to explain the impact of biotic factors influencing the presence of ciliates, including the abundance of bacteria, microalgae, and small Metazoa.     

Patterns of Ant (Hymenoptera: Formicidae) Richness and Relative Abundance along an Aridity Gradient in Western Venezuela

In xeric ecosystems, ant diversity response to aridity varies with rainfall magnitude and gradient extension. At a local scale and with low precipitation regimes, increased aridity leads to a reduction of species richness and an increased relative abundance for some ant species. In order to test this pattern in tropical environments, ant richness and relative abundance variation were evaluated along 35 km of an aridity gradient in the Araya Peninsula, state of Sucre, Venezuela. Three sampling stations comprising five transects each were set up. Pitfall traps and direct collecting from vegetation were assessed per transect. Overall, 52 species, 23 genera, and 7 subfamilies of ants were recorded in the peninsula. The total number of species and genera recorded by both sampling stations and transects decreased linearly with increasing aridity. Total relative abundance was highest in the most arid portion of the peninsula, with Crematogaster rochai (Forel) and Camponotus conspicuus zonatus (Emery) (Hymenoptera: Formicidae) being the numerically dominant species. Spatial and multivariate analyses revealed significant changes in ant composition every 11 km of distance, and showed a decrease of ant diversity with the increase of harsh conditions in the gradient. Here, we discuss how local geographic and topographic features of Araya originate the aridity gradient and so affect the microhabitat conditions for the ant fauna.     

Composition and distribution of the peracarid crustacean fauna along a latitudinal transect off Victoria Land (Ross Sea,Antarctica) with special emphasis on the Cumacea

The following study was the first to describe composition and structure of the peracarid fauna systematically along a latitudinal transect off Victoria Land (Ross Sea, Antarctica). During the 19th Antarctic expedition of the Italian research vessel “Italica” in February 2004, macrobenthic samples were collected by means of a Rauschert dredge with a mesh size of 500 μm at depths between 85 and 515 m. The composition of peracarid crustaceans, especially Cumacea was investigated. Peracarida contributed 63% to the total abundance of the fauna. The peracarid samples were dominated by amphipods (66%), whereas cumaceans were represented with 7%. Previously, only 13 cumacean species were known, now the number of species recorded from the Ross Sea increased to 34. Thus, the cumacean fauna of the Ross Sea, which was regarded as the poorest in terms of species richness, has to be considered as equivalent to that of other high Antarctic areas. Most important cumacean families concerning abundance and species richness were Leuconidae, Nannastacidae, and Diastylidae. Cumacean diversity was lowest at the northernmost area (Cape Adare). At the area off Coulman Island, which is characterized by muddy sediment, diversity was highest. Diversity and species number were higher at the deeper stations and abundance increased with latitude. A review of the bathymetric distribution of the Cumacea from the Ross Sea reveals that most species distribute across the Antarctic continental shelf and slope. So far, only few deep-sea records justify the assumption of a shallow-water–deep-sea relationship in some species of Ross Sea Cumacea, which is discussed from an evolutionary point of view.     

Investigations on the meiofauna and sediment of the Shatt Al-Arab near Basrah (Iraq)

SUMMARY. Sediment quality and meiofauna distribution were investigated in the Shatt Al-Arab near Basrah (Iraq). Four stations were fixed in a transect reaching from the eulittoral to the main channel of the river. The sediment was investigated with respect to wet mud density, dry mud density, water content, organic matter, calcareous substances, and allochthonous inorganic materials. There were no major differences between the sediments taken at the different stations. Sediment quality was not a limiting factor for the distribution of meiofauna; important factors were water current, light penetration and temperature. The current has a great influence on sediment structure, the main channel of the river had harder sediment consisting of clay. Because of high turbidity, light can reach the bottom only in shallow water at stations I and II; macrophytes were present only at these two stations. The highest numbers of invertebrates were found at station II (0.5 m depth). As water depth increased, the abundance of meiofauna decreased. Nevertheless, the number of individuals at station I (0.05 m) in the tidal zone was lower than at station II. This fact can be explained by the magnitude of changes of the environmental conditions, especially temperature and insolation. There were very large diurnal temperature fluctuations, fluctuating between 10 and 25°C on a single day. Many meiofauna species cannot tolerate such fluctuations and colonize mainly the deeper reaches of the river, which are continuously covered by water. Stronger currents in the middle of the river prevent the settlement of large numbers of animals in this area.     

Microscopy- or DNA-based analyses: Which methodology gives a truer picture of stream-dwelling decomposer fungal diversity?

We assessed aquatic hyphomycete diversity in autumn and spring on oak leaves decomposing in five streams along a gradient of eutrophication in the Northwest of Portugal. Diversity was assessed through microscopy-based (identification by spore morphology) and DNA-based techniques (Denaturing Gradient Gel Electrophoresis and 454 pyrosequencing). Pyrosequencing revealed five times greater diversity than DGGE. About 21% of all aquatic hyphomycete species were exclusively detected by pyrosequencing and 26% exclusively by spore identification. In some streams, more than half of the recorded species would have remained undetected if we had relied only on spore identification. Nevertheless, in spring aquatic hyphomycete diversity was higher based on spore identification, probably because many species occurring in this season are not yet connected to ITS barcodes in genetic databases. Pyrosequencing was a powerful tool for revealing aquatic hyphomycete diversity on decomposing plant litter in streams and we strongly encourage researchers to continue the effort in barcoding fungal species.     

胶州湾西部海域大型底栖动物多样性的研究

为了揭示胶州湾最近几年底栖动物多样性的变化, 作者于2003年9月到2004年9月在胶洲湾西部海域5个测站每2个月1次共进行了7个航次采样, 以种类组成、生物量和栖息密度为基础, 对大型底栖动物多样性进行了分析。使用PRIMER软件计算得到以下变量: 群落的物种数(S)、丰富度(D)、Shannon-Wiener物种多样性指数(H')和均匀度指数(J')。结果表明: 位于大沽河口的D站和水道中央的S站的多样性最低; 养殖区内外站位的多样性差异显著; 丰度/生物量曲线表明, 养殖区内的底栖动物群落已经受到了一定程度的扰动。群落物种数(S)和丰富度(D)的季节性变化明显, 春季和秋季较低, 夏季和冬季较高。分析菲律宾蛤仔(Ruditapes philippinarum)增养殖区的站位(D)发现, 多样性指数和丰富度与次级生产力有着负相关的关系。物种多样性指数和丰度/生物量曲线的分析显示, 该研究海域处于一个轻度人为扰动的状态。     

Bryozoan assemblages on hard substrata: species abundance distribution and competition for space

Bryozoans are colonial invertebrates that often dominate epibenthic assemblages on the lower surfaces of hard substrata. Competition among neighbouring organisms is usually a critical process regulating biodiversity, and hard substrata have proved to be a suitable model habitat to analyse spatial interactions. We explored the relationships among abundance, species richness, diversity, competitive ability, coverage, available surface, depth and substratum size in an assemblage of bryozoans encrusting pebbles and cobbles in a bank off the eastern mouth of the Strait of Magellan. We also tested whether overgrowth competition can be regarded as hierarchical, and whether the species abundance distribution shows a mode of rare species and a decreasing frequency of increasingly abundant species. Abundance, species richness, diversity and overgrowth competition were highest on the largest substrata. Smaller pebbles tended to be encrusted by the commonest bryozoans, while the rarest species were mainly found on relatively larger clasts. A high proportion of the lower surfaces of most substrata was available for growth. Diversity values of relatively shallow stations were lower than expected under Caswell’s neutral model. Interspecific competition was hierarchical, but the abundance of colonies was not related to the competitive ability of each species. The species abundance distribution was bimodal, with a main mode of rare species and a second one partly composed of relatively abundant bryozoans with poor competitive abilities. This study shows that even in an encrusting assemblage where competition is hierarchical, the weakest competitors persist and the dominant species are far from being capable of monopolizing space.     

Bionomy of Macrobenthic Molluscs in Evros Delta (North Aegean Sea)

The composition and distribution of the macrobenthic molluscs in Evros Delta (North Aegean Sea) were investigated by quantitative sampling. The molluscan distribution shows a zonation mainly related to the degree of “confinement”. Based on similarity in distribution among stations, 2 groups of species were distinguished. One group includes marine species (Tellina tenuis, Bittium reticulatum) found only in coastal stations and the second group is typical of estuarine species (Hydrobia acuta, Abra ovata and Cerastoderma glaucum) distributed in almost all stations. Spatial fluctuations of the 3 estuarine species reflect their preferences in the various parameters (“confinement”, salinity, grain size and organic matter of sediment). The most isolated stations support the highest values of total mollusc abundance and biomass.