Mean Annual Abundance Research Articles

Salinity Tolerance, Seasonal and Multiyear Dynamics of Biting Midges (Diptera, Ceratopogonidae) in Macrozoobenthos Communities of Saline Rivers (the Lake Elton Basin, Russia)

The results of long-term studies of biting midges (Diptera, Ceratopogonidae) in macrozoobenthos communities of five saline rivers of the hyperhaline Lake Elton basin are presented. The fauna of Ceratopogonidae includes 5 halophilic and euryhaline species, among which representatives of the tribe Palpomyiinae predominate. Taxonomic composition of the family differs in rivers with different levels of salinity. Species Sphaeromias miricornis and Culicoides riethi are widely distributed in mesohaline the Khara, the Lantsug and the Bolshaya Samoroda rivers, and P. schmidti widely distributed in polyhaline the Chernavka and the Solyanka rivers. Two generations of S. miricornis and three generations of P. schmidti were recorded. Departure of the first generation of P. schmidti occurs in mid-May, S. miricornis in late May–early June. There is an increase in mean annual abundance and biomass of biting midges in polyhaline rivers compared to mesohaline rivers.

Seasonal Changes in Vertical Distribution and Population Structure of the Dominant Hydrozoan Aglantha digitale in the Western Subarctic Pacific

Hydrozoans are numerically dominant taxa in gelatinous zooplankton communities of the worldwide oceans and play an energy transfer role connecting primary producers and higher trophic level organisms. In the western subarctic Pacific, St. K2 has been established as a long-term time-series monitoring station. Various studies on zooplankton have been conducted, while hydrozoans have not been treated. This study presents the abundance, vertical distribution, and population structure of the dominant hydrozoan species (Aglantha digitale) at St. K2. Samples collected by vertical stratification samplings from eight layers of 0–1000 m both day and night during four seasons in one year. Hydrozoans occur throughout the year. The annual mean abundance of A. digitale was 198.4 ind. m−2 and composed of 91.9% of hydrozoans. The vertical distribution of A. digitale was concentrated for the epipelagic layer (0–200 m), both day and night of the most season. The bell height (BH) of A. digitale ranged between 2.4–18.9 mm. Most of the mature individuals, with gonad length larger than 10% of BH, occurred only in July. The BH of mature individuals ranged from 4.7 to 17.6 mm, with the BH of most mature individuals were larger than >10 mm. Through observation on BH at each sampling layer, small individuals with BH < 6 mm were distributed below 300 m depths throughout the seasons, expanding their vertical distribution to the deeper layers. Inter-region comparison of abundance, maturation body size, and generation length of A. digitale revealed that these parameters are varied with the region and depend on the marine ecosystem structures.

Diel, seasonal and vertical changes in the abundance, biomass and community structure of pelagic polychaetes at the subtropical station S1 in the western North Pacific: comparison with the results from the subarctic station K2.

Information on pelagic polychaete community structure in the western North Pacific is available for the subarctic region (Station K2) but not for the subtropical region. Hence, we analyzed day-night vertically stratified samples collected in eight layers within the first 1000m of the water column during four seasons in 1year, using the same sampling method as St. K2, at the subtropical region (Station S1). At St. S1, 27 species of pelagic polychaetes belonging to 13 genera and six families were identified. The annual mean abundance was 35.0 ind. 1000m-3 and the biomass was 17.3mg WW 1000m-3. At St. S1, the numbers of genera and species were higher and the annual mean abundance and biomasses were much lower than St. K2. The pelagic polychaetes often peaked in the mesopelagic layer at St. K2, with the carnivores and particle feeders peaking in the epipelagic and mesopelagic layers, respectively. At St.S1, the carnivorous species predominated throughout the entire water column, and were most abundant in the epipelagic layer. Thus, In the western Pacific Ocean, the subarctic pelagic polychaete community structure changed vertically with feeding ecology. On the other hand, the subtropical community may be adapted to conditions of high irradiance and light transmission.

Demographic response of a high-Arctic polar bear (Ursus maritimus) subpopulation to changes in sea ice and subsistence harvest

Climate change is a long-term threat to polar bears. However, sea-ice loss is hypothesized to provide transient benefits in high latitudes, where thick multiyear ice historically limited biological productivity and seal abundance. We used joint live-recapture and dead-recovery mark-recapture models to analyze data for one of the most northerly polar bear subpopulations, Kane Basin. The data consisted of 277 initial live captures and genetic identifications (1992-1997 = 150, 2012-2014 = 127), 89 recaptures or re-identifications (1992-1997 = 53, 2012-2014 = 36), and 24 harvest returns of research-marked bears during 1992-2014. We estimated mean annual abundance of 357 bears (95% CI: 221-493) for 2013-2014. This suggests a likely increase relative to our estimate of 224 (95% CI: 145-303) bears in the mid-1990s and relative to a previously published estimate of 164 (95% CI: 94-234) bears in the mid-1990s that used some of the same data. This is also supported by an apparent increase in the density of bears in eastern Kane Basin during 2012-2014. Estimates of total survival for females ≥3 yr old (mean ± SE: 0.95 ± 0.04) and their dependent offspring were similar to previous estimates from the 1990s, and estimates of unharvested survival for females ≥3 yr (0.96 ± 0.04) appear sufficient for positive population growth. Estimates of total survival were lower for males ≥3 yr (0.87 ± 0.06). We documented a reduction in mortality associated with subsistence harvest, likely attributable to implementation of a harvest quota by Greenland in 2006. Our findings, together with evidence for increased range sizes, improved body condition for all sex and age classes, and stable reproductive metrics, show that this small high-Arctic polar bear subpopulation remains productive and healthy. These benefits are likely temporary given predictions for continued climate change.

Spatial and Temporal Changes of Planktonic Microcrustaceans (Cladocera, Copepoda) and their Relationship with Physicochemical Parameters in Kırklareli Reservoir (Kırklareli-Türkiye)

The present study focused on monthly densities and abundances of planktonic microcrustaceans (Cladocera and Copepeda) in Kırklareli reservoir, as well as their relationship with some physicochemical parameters at three stations for the period from May 2018 to April 2019. In the present study, a total of 26 planktonic microcrustaceans species, 14 from Cladocera and 12 from Copepoda were identified. The mean annual microcrustacean abundance recorded during the study was 24076 ind/m3, 67% of which was Cladocera (16054 ± 12414 ind/m3) and 33% was Copepoda (8022 ± 5564 ind/m3). The maximum abundance of planktonic microcrustaceans were found in September (51521 ind/m3) and the minimum was found in January (2919 ind/m3). The most common species in the reservoir were Bosmina longirostris, Daphnia pulex, Daphnia cucullata, Daphnia galeata, Daphnia longispina and Diaphanosoma brachyurum from Cladocera and Cyclops abyssorum, Cyclops vicinus, Eudiaptomus vulgaris and Arctodiaptomus wierzejskii from Copepoda. The environmental parameter values measured in the reservoir were acceptable to support aquatic life, especially the zooplankton community. The total density and abundance of zooplanktonic microcrustaceans showed positive correlation with the water temperature and Chlorophyll-a. According to these results, we concluded that Kırklareli reservoir has a mesotrophic character in terms of the microcrustacean fauna and the physicochemical parameters.

Structure and heterogeneity of habitat determine diet of predators despite prey abundance: Similar response in Long-eared, Short-eared Owls and Common Kestrels

According to one of the theses of optimal foraging theory, main prey species abundance in the hunting area is the main factor determining the diet and habitat choices of birds of prey. However other factors can also be important. The habitat structure influences the predators' diets as well. In this study we examined the influence of habitat structure on diet compositions of three species of birds: Long-eared Owl (Asio otus), Short-eared Owl (A. flammeus) and Common Kestrel (Falco tinnunculus). The study was carried out from 2007 to 2019 in a 48 ​km2 area of the Crane's Homeland Reserve, Moscow Region, Russia. The habitat structures of model species' hunting territories (ratio of different types of landscape elements) were classified in module “Semi-Automatic Classification Plugin” based on the QGIS. A boosted regression tree analysis identified that the share of the main prey species in the diet is primarily determined by the landscape structure of hunting territories. The largest share of Common Vole (Microtus arvalis) in birds' diet was determined by the shrubs area (15% of hunting area), the meadow area (75%), the habitat heterogeneity (70%) and the arable land area (5%). The same predictors determined the largest share of Root Vole (Microtus oeconomus): the shrubs area 25%, the meadow area 70%, and the arable land area 3%. The annual mean abundance of prey species did not determine their importance in the diet of birds of prey. Thus, the main prey abundance in the hunting area is not a determining factor for the formation of diet composition of birds of prey.

Population fluctuations of long-tailed voles (Microtus longicaudus) in managed forests: site-specific disturbances or a long-term pattern?

Abstract We investigated population responses of Microtus longicaudus to cumulative clear-cutting of coniferous forests and to enhanced understory vegetation in young, fertilized pine stands near Summerland, British Columbia, Canada. We explored if there was a threshold level of habitat quality arising from a given forest disturbance for M. longicaudus to increase to high population levels and potentially fluctuate in abundance over time. Secondly, we asked if these outbreaks were site-specific or part of a long-term pattern. We tested three hypotheses (H) that populations of M. longicaudus would increase in abundance and potentially fluctuate owing to (H1) the availability of early seral postharvest habitats associated with cumulative clear-cut harvesting; (H2) woody debris piles on clear-cuts; and (H3) have higher mean abundance, reproduction, and survival in fertilized forest sites with enhanced understory vegetation. Mean annual and peak abundances of M. longicaudus were significantly different across the four Periods of cumulative forest harvesting with numbers being highest in the first two Periods. Thus, H1, that long-tailed voles would increase in abundance on new clear-cuts, was partially supported for the first two Periods but not in the later Periods. Constant cattle (Bos taurus) grazing during summer periods over the four decades may have reduced vegetative productivity for voles and damped out population responses on these clear-cut sites, at least in the last two Periods. Woody debris piles on clear-cuts may have increased abundance and generated a population fluctuation, thereby supporting H2. Enhanced abundance of understory vegetation had no effect on mean abundance, reproduction, or survival of M. longicaudus, and hence did not support H3. We conclude that it is site-specific disturbances, particularly in forest management, that generate occasional outbreaks of M. longicaudus, and there does not appear to be any long-term pattern to these discordant fluctuations.

Seasonal and Interannual Dynamics of Pelagic Rotifers in a Tropical, Saline, Deep Lake

This is the first long-term study (monthly samples at two 4-year intervals: 1998 to 2001 and 2013 to 2016) on rotifers in a saline, deep lake. The pelagic rotifer assemblage of Lake Alchichica is simple and comprised by two species, both new and most likely endemic: Brachionus sp. Mexico (related to B. plicatilis) and Hexarthra sp. (related to H. jenkinae). Similar low species richness and composition are found in other saline lakes associated with salinity. Rotifers in Lake Alchichica were an irregular component of the zooplankton community. Rotifers’ overall abundance (471 ± 1211 ind m−2) and biomass (24 ± 63 mg DW m−2) were low; Brachionus sp. Mexico and Hexarthra sp. contributed similarly to the annual mean abundance (54% and 46%, respectively) and biomass (53% and 47%, respectively). Abundance and biomass were tightly coupled, but there was no regular pattern in their seasonal dynamics. When co-existing, Brachionus sp. Mexico showed a higher abundance than Hexarthra sp. The dominant (≈80%) phytoplankton biomass in Lake Alchichica, the large (35–63 µm) diatom Cyclotella alchichicana, is inedible for rotifers, thus rotifers most probably relied only on nanophytoplankton (≤20 µm). Seasonal and interannual differences in rotifers seem related to food availability (oligotrophy) and probably to biotic interactions (e.g., competition). Rotifer abundance and biomass values in 1998–2001 went down to 12.5% in 2013–2016. Climate change and stochastics events leading to pulses of the rotifers’ food, and biotic interactions seem to be the most plausible explanation.

Planktonic communities in a small post-peat reservoir (Ustka Forest District, Poland)

Abstract The aim of this study was to evaluate the present state of a small (area of 0.2 ha), shallow (mean depth of 2 m) and approximately 30-year-old post-peat reservoir located in Bruskowskie Bagno, a Baltic raised mire in northern Poland. The study was conducted during all seasons of the year (August 2019–July 2020). The reservoir was characterised by a yellow to brown water colour, low pH (5.4) and quite low conductivity (40.4 μS cm-1), which are the main features of dystrophic water bodies. Similar to natural, dystrophic lakes and ponds, the phytoplankton was mainly composed of mixotrophic species like Dinobryon sp. and Gonyostomum semen. The only numerous non-flagellate group within the phytoplankton was desmids, which indicated that the water was influenced by the mire. The reservoir was characterised by a high abundance of ciliates (annual mean of 55.6 cells ml-1) and a very high abundance of rotifers (annual mean of 3.72 ind. ml-1). Among ciliates, the most important were prostomatids, accounting for 53% of the mean annual ciliate abundance. The results of our study indicate that artificial, approximately 30-year-old, post-peat reservoir resembled a natural dystrophic water body.

<p class="ZootaxaTitle"><strong>Community structure and seasonal changes in population structure of pelagic polychaetes collected by sediment traps moored in the subarctic and subtropical western North Pacific Ocean</strong></p>

Community structure and seasonal changes in the population structure of pelagic polychaetes were studied based on zooplankton samples collected by sediment traps moored at 200 m depth in the subarctic and subtropical western North Pacific throughout the year. Eight species belonging to seven genera and seven families occurred at the subarctic station, while twelve species belonging to ten genera and seven families were identified at the subtropical station. Polychaete abundance was 5.37 ± 0.44 ind. m-2 day-1 (annual mean ± standard error) at the subarctic station, and 1.36 ± 0.15 ind. m-2 day-1 at the subtropical station. Polychaete abundance at the subarctic station was high from May to August, but no seasonal patterns were observed at the subtropical station. The dominant species in the subarctic was Tomopteris septentrionalis, which accounted for 62.9% of annual mean abundance; at the subtropical station, the dominant species was Pelagobia sp. (22.8%). In the subarctic, small specimens of T. septentrionalis (<3 mm in body length) occurred only in winter (December-March). No clear seasonal changes in population structure of the subtropical Pelagobia sp. were detected. The latitudinal patterns we observed in the polychaete communities of the western North Pacific were similar to those previously observed in the eastern North Pacific. Changes in the population structure of T. septentrionalis suggest that the life cycle of this species is seasonal in the subarctic region.

Macrobenthic communities in the tidal channels around the Gulf of Gabès, Tunisia

A yearlong seasonal survey was carried out during 2016–2017 at 26 stations representing four tidal channels of the north-western part of the Gulf of Gabès (Tunisia). The area studied (characterized by a maximum tidal range of 2.3 m) was subjected to diverse anthropogenic pressures: from the phosphate industry and its metallic pollution, unauthorized bottom trawling in shallow water (known locally as ‘Kiss’), and organic pollution from the nearby urbanized areas. A total of 23,506 invertebrates representing 311 taxa were collected. Dominant taxa were the polychaetes with 51.4% of the individuals collected and 39.3% of the taxa, the amphipods (18.6% and 15.5%), the tanaids (12.3% and 2.6%), and the molluscs (11.5% and 18.3%). The mean annual abundances varied widely from one channel to another: from 300 to 3700 ind·m−2. The stations located in deeper waters exhibited greater variability. Measurements of abundance revealed seasonal changes with maximum values in winter, spring, and lower numbers in summer. Each tidal channel was characterized by specific features in the fauna. The macrofauna were dominated by the polychaete Cirratulus cirratus (mainly in spring) and the amphipod Microdeutopus anomalus (mainly in winter), whilst both of the tanaids, Apseudopsis gabesi (the first sighting reported for the area) and A. mediterraneus, were found to be abundant in winter in at least one of the four channels. Species are mainly deposit feeders, herbivorous and omnivorous. The analyses on spatial and temporal changes of the macrofauna population revealed variations according to the composition of the fauna increasing or falling along the channels and as a function of seasonal changes. In spite of a high level of anthropogenic activities, the Ecological Status (ES) assessment (applying the AMBI and M-AMBI indices) attributed High or Good ES for 10 stations, Moderate ES for 11 stations and five stations showed a poor ES at least during one season. Sampling subtidal stations in the future to survey long-term degradation of such ecosystems of the coastal environment of the Gulf of Gabès in Tunisia is proposed.

Meiofauna in stream habitats: temporal dynamics of abundance, biomass and secondary production in different substrate microhabitats in a first-order stream

Meiofaunal abundance, biomass and secondary production were investigated over 13 months in an unpolluted first-order stream. Four microhabitats were considered: sediment and the biofilms on dead wood, macrophytes and leaf litter. The relative contribution of the microhabitats to secondary production and the influence of environmental factors on meiofaunal density distribution were estimated. We expected (1) meiofaunal abundance and biomass to exhibit seasonal patterns, with more pronounced seasonal fluctuations on macrophytes and leaf litter than in the other microhabitats, (2) annual secondary production to be highest in sediment; however, the relative contribution of the microhabitats to monthly secondary production would change during the year, and (3) a bottom-up driven influence on meiofaunal density distribution in the microhabitats. Meiofaunal annual mean abundance, biomass and secondary production were 7–14 times higher in sediment and on dead wood than on macrophytes and leaf litter. Significant seasonal patterns described the meiofaunal abundance in sediment and on leaf litter as well as the biomass in sediment, on macrophytes and leaf litter. Organisms in sediment and on dead wood contributed 48 and 43%, respectively, to secondary production m−2, but in regard to the stream area covered by the microhabitats, sediment had the highest share (80%). Significant determinants of the density distribution were AFDM, protozoans, bacteria and Chl-a, which influenced all meiofaunal groups. Our study clearly indicates that meiofaunal organisms in sediment and on dead wood have a remarkable share on total secondary production of lotic systems which is especially relevant for forested low-order streams.

Sharp-tailed Grouse (<i>Tympanuchus phasianellus</i>) population dynamics and restoration of fire-dependent northern mixed-grass prairie

Case studies of Sharp-tailed Grouse (Tympanuchus phasianellus) population dynamics before and during re-introduction of fire to northern mixed-grass prairies that lacked fire for multiple decades are unavailable. At a 108-km2 northern mixed-grass prairie refuge in North Dakota, fire was suppressed from the early 1900s through late 1970s. Nine management units (total area 16.8 km2, 15.7% of the refuge) received initial prescribed fire treatments during 1979–1984. The mean annual density of male Sharp-tailed Grouse attending leks on these units during 1981–1985 (9.0 males/km2) was twice that on the same units during 1961–1965 (4.2 males/km2), amid the fire exclusion era; nonoverlap of 90% CIs encompassing the means suggested a significant treatment effect. However, densities of males on units managed without prescribed fire during 1961–1965 and 1981–1985 did not change between the two periods. By 1987, fire had been re–introduced to >50% of the refuge overall. Mean annual abundance (i.e., total numbers) of lekking males on the entire refuge did not differ between 1961–1965 and 1981–1985 but was significantly greater during 1989–1993 than during 1961–1965 and 1981–1985. Changes in density and abundance of lekking males coincided with fire-induced reductions in woody cover and increases in herbaceous cover. Our study illustrates the marked capacity of Sharp-tailed Grouse to respond to reductions of tree and shrub cover resulting from prescribed fire in northern mixed-grass prairie and the species’ attraction to habitat disturbance in general.

Seasonal and annual segregation of liquid water and ice clouds in Iran and their relation to geographic components and precipitation

Efficient and proper understanding of the state of the clouds regarding different seasons of the year will have profound effects on different economic and environmental sectors. The purpose of this study is to determine the hourly dissociation of ice and liquid clouds in Iran. To this end, cloud optical thickness (COT) data, as well as optical depth of clouds in two phases of liquid and ice were obtained and processed from 31 synoptic meteorological stations (1960–2015), MODIS data from Terra satellite during the years 2001 to 2011, and they were processed then. Next, using the RegCM4 model, the cloud fraction (clt) was simulated to accurately identify the cloud cover situation in Iran. The results showed that the maximum annual mean abundance of liquid and ice clouds was 18.95 days for the time 15:00 and 3.99 days for the time 06:00, respectively. Climatic zones of the Caspian and Persian Gulf coasts at 15 o’clock had the highest decreasing trend of liquid clouds. Ice clouds in all parts of Iran’s climate, with the exception of the eastern plateau, also declined. From south to north and east to west of Iran, the occurrence of ice and liquid clouds is increasing. Therefore, the spatio-temporal distribution of liquid and ice clouds in the country was also dependent on spatial components and latitude had the greatest impact. From the satellite and modeled data, the RegCM4 model has been able to detect the Monsoon phenomenon in southeastern Iran during the summer. CLT simulation in Iran has also shown that cloud cover in Iran fluctuates between 28 and 65% on average, with 81.5% of Iranian stations having a significant change in the amount of annual cloud cover. Correlation of liquid and ice clouds with precipitation showed that liquid clouds in summer and ice clouds in spring had higher correlation with precipitation in Iran. Northern coasts of Iran due to greater ascent mechanisms such as coastal compressors, north latitude atmospheric circulation systems, and maximum winds in the north and west of Iran due to the location of western systems entry and sufficient thermal gradient, had maximum ice clouds in the last half century. Also, south of Iran, despite having extended and great water-bodies, is less cloudy due to descending air in Hadley’s circulation (Hadley cell) of air.

A new approach to recruitment overfishing diagnosis based on fish condition from survey data

A new approach to recruitment overfishing diagnosis is presented. We hypothesize that condition of recruits should increase when recruitment failures are caused by fishing activity. This would be a consequence of the increase in trophic resource availability, because the population is smaller than that which the ecosystem could support. Temporal series of hake recruit condition were calculated from MEDITS survey data collected in Mediterranean geographical sub-areas (GSAs) 1, 6, 17 and 19 from 1994 to 2015. Multiple linear regressions were used to analyse the relationship between mean annual condition and abundance of recruits and climatic indices in each GSA. Significant correlations were only detected in GSA 6, where 69% of condition variability was explained by the negative correlation with recruit abundance, and with two climatic indices, the Western Mediterranean Oscillation and the standardized air temperature anomaly at surface from the Gulf of Lions. Despite the differences in recruit abundance among GSAs, their mean annual condition oscillated around the same basal value during most of the time series, pointing to density-dependent mortality rates as an important mechanism stabilizing hake recruitment to levels close to the carrying capacity when populations do not suffer recruitment overfishing. This pattern changed when the decreasing recruit abundance trend drove GSA 6 condition values persistently above those of the rest of the GSAs. According to our hypothesis, hake in GSA 6 is in recruitment overfishing.

Stability of chewing louse (Phthiraptera: Amblycera and Ischnocera) populations infesting great horned owls (Aves: Strigidae)

AbstractThe annual abundance of chewing lice (Phthiraptera) was recorded on great horned owls (Bubo virginianus(Gmelin), Aves: Strigidae) from 1994 to 2015 in Manitoba, Canada.Kurodaia magnaEmerson (Amblycera: Menoponidae) had a mean annual abundance about half that forStrigiphilus oculatus(Rudow) (Ischnocera: Philopteridae). Mean intensity, rather than prevalence, explained the variation in annual abundance. Temporal variation (measured as population variability) in abundance and mean intensity were high and similar (0.62–0.67), but lower for nymph to female ratio (0.36–0.38). Temporal variation of prevalence and sex ratio were higher forK. magna(0.34–0.35) than forS. oculatus(0.21–0.22), and typical for other louse species. The high temporal variability for abundance and mean intensity suggest lower year-to-year stability than exhibited by other chewing lice, but over 80% of this variability was due to sampling error resulting from small sample sizes in some years and extreme intensities in the aggregated distributions of intensity. The remaining variation, < 20%, revealed no significant differences in annual abundance or mean intensity among years, and therefore stable populations over 22 years. Populations of 12 species of chewing lice show lower temporal variability and therefore greater stability than three other insect taxa.

Episodic recruitment of young Prochilodus lineatus (Valenciennes, 1836) (Characiformes: Prochilodontidae) during high discharge in a floodplain lake of the River Paraná, Argentina

AbstractProchilodus lineatus (Val.) is one of the main target species of South American freshwater fisheries. The following null hypotheses regarding juvenile recruitment of P. lineatus were tested: (a) recruitment is not determined by variations in larval abundance and (b) recruitment is not determined by variations in discharge. For this purpose, variations in abundance of larvae in main channel drift and monthly captures of juveniles in a floodplain lake of the River Paraná were examined weekly between 2009 and 2016. Mean annual abundances of larval densities and CPUE of juveniles were correlated with a set of hydrometric variables. A positive correlation was found between the abundance of juveniles with high and persistent flood pulses. By contrast, larval abundance was not correlated with juvenile abundance. Pronounced contrast was found in the recruitment of P. lineatus between years of high and low discharge, which supports the hypothesis that floods are the main determining factor for recruitment of this species.

Changes in the phytoplankton community structure of the Backshore Wetland of Expo Garden, Shanghai from 2009 to 2010

Phytoplankton community structure, abundance, and species' spatial and temporal distributions were examined for the Backshore Wetland of Expo Garden in Shanghai from September 2009 to August 2010. A total of 371 phytoplankton species were identified from 109 genera 8 phyla. There were 18 dominant species in total, and Phormidium tenue was dominant during four seasons. The mean annual abundance and biomass were 711.11 × 104 cells/L and 5.70 mg/L, respectively. The seasonal changing trend of existing stocks was bimodal, with main peaks of density and biomass occurring in the winter and a secondary peaks occurring in the summer. The Shannon–Wiener diversity index (H′), the Margalef species richness index (D), and Pielou's species evenness index (J) showed a clear seasonal trend. All of the indices showed a changing pattern, with the highest recorded values from the summer to autumn and the lowest recorded values from the winter to spring. The canonical correspondence analysis (CCA) showed that environmental factors, including water temperature, nitrate nitrogen, and pH were the main influencing factors to the change of phytoplankton community structure in the Backshore Wetland of Expo Garden in Shanghai.

Spatio-temporal distribution of demersal fish species in the northern Alboran sea and Gulf of Vera

Spatio-temporal distribution of demersal fish species in the northern Alboran sea and Gulf of Vera

Population dynamics of ticks infesting horses in north-west Tunisia.

A preliminary study was carried out to examine the population dynamics of ticks on 24 pure Arabian horses. The horses were monitored monthly over one year in the Ghardimaou region of north-west Tunisia. A total of 120 adult ticks were collected and identified, leading to the estimation of different parasitological indicators. The ticks belonged to a single genus (Hyalomma) and three species: H. scupense (59%), H. marginatum (28%) and H. excavatum (13%) (p < 0.001). The mean infestation prevalence was 29.5%; the highest prevalence was observed for H. scupense (41.7%) (p < 0.05). The mean overall intensity of infestation was0.3 ticks/horse. The highest mean intensity was observed with H. scupense (0.6 ticks/horse) and the highest individual intensity measurement was observed for H. scupense (1.1 ticks/animal). The mean annual abundance of ticks was 0.1 ticks/animal. There was no significant correlation between a horse's age and the number of ticks (p > 0.05), but the proportion of ticks on mares was significantly higher than that on males: 65.0% and 35.0%, respectively (p < 0.05). To the authors' knowledge, this is the first longitudinal study of tick dynamics in North African horses.