Zooplankton distribution in four ponds of different salinity: a seasonal study in the solar salterns of Sfax (Tunisia)

The seasonal distribution of metazooplankton and large-sized ciliates was studied in four ponds of different salinity in the solar salterns of Sfax (Tunisia). Total zooplankton abundance varied from 1 × 10³ to 4.7 × 10⁶ ind m^–3. Salinity had a negative effect on the abundance of copepods and rotifers which were absent in the pond with the highest salt concentration (180) in which the number of taxa was low and Artemia or the ciliate Fabrea largely dominated the zooplankton community. Temperature and the presence of Dunaliella salina as prey appeared as key factors in controlling the abundance of Artemia, while organic detritus appeared as important in the diet of Fabrea. Change in zooplankton species composition along the hypersaline gradient (40–90) was primarily related to salinity. However, our data suggest the importance of both the abundance and composition of food in the spatial and temporal variations of some zooplankton species.     

Branchipus cortesi n. sp.: a new anostracan from western Spain (Crustacea,Branchiopoda)

Branchipus cortesi, n. sp. (Anostraca, Branchipodidae) is characterized by the broadly enlarged distal segments of male antenna 2, and a combination of morphological features concerning thoracic limbs, abdominal segments and egg morphology. The species occurs in temporary fresh water bodies in flatlands with temperate Mediterranean climate; it is distributed in the south-western part of Spain. Our study includes a morphological analysis using optical and scanning electronic microscopes. Questions about ecology and distribution of the new species are also discussed.     

Redescription of Branchinecta granulosa Daday, 1902 from Argentina (Crustacea: Branchiopoda)

The species Branchinecta granulosa Daday 1902, is redescribed on the basis of adult material from near Facundo (Chubut Province, Argentina). Its relationship to its regional congeners is outlined.     

Fuelling rates of garganey ( Anas querquedula) staging in the Camargue, southern France, during spring migration

Most species of long-distance migratory birds put on energy stores to fuel their travels. However, recent studies have highlighted the potential costs associated with carrying too much fuel, either through increased predation risk or decreased flight efficiency. Consequently, it is now widely accepted that migratory birds should carry optimal rather than maximum fuel loads. Information from 372 garganey (Anas querquedula) ringed and recaptured at least once during the same spring in the Camargue, southern France, was used to document fuelling rates of individual ducks in relation to environmental variation and individual variation in condition. On average, garganey added very little fuel stores in the Camargue (mean gain per day=0.33 g, less than 0.5% of mean body-mass in total over an average stay of 5 days). Fuelling rates were negatively correlated with body mass at capture, but it cannot be excluded that this pattern was a statistical artefact. Given their body-mass at ringing, garganey could potentially still fly long distances when they stop in the Camargue. It is therefore likely that the aim of their stay in southern France is more for resting than refuelling, a finding that may have implications for the proper management of stop-over sites.Communicated by F. Bairlein     

A test of the wintering strategy hypothesis with teal (Anas crecca) ringed in the Camargue, southern France.

Body mass changes in wintering ducks have been considered as the consequence of their wintering strategy, i.e. low mass after autumn migration, active foraging leading to body mass restoration, then pairing leading to low body mass again. This pattern is supported by weights of hunter-killed birds, but this is not enough to rule out potential alternative hypotheses linked to the existence of different populations with different body masses. The use of data collected at ringing and subsequent recaptures of known birds demonstrates that teal (Anas crecca) gain and lose body mass from September to March.     

苏州工业园区水体浮游甲壳动物群落特征及其与环境因子的关系

于2012年6月至2013年5月,对苏州工业园区湖泊和河流水体的浮游甲壳动物组成及群落结构进行了研究,分析了浮游甲壳动物的密度和生物量的年度变化,探讨其分布与水体理化因子间的关系.结果表明：园区水体有枝角类6科12属24种,桡足类7科13属18种,其中短尾秀体溞、长额象鼻溞、汤匙华哲水蚤及近邻剑水蚤在不同水体中不同季节均为优势种.在湖泊水体和河流水体中,浮游甲壳动物的密度和生物量表现为夏、秋季较高,冬、春季较低,且在夏、秋季分别具有2个峰值.枝角类平均密度和生物量在河流水体中均高于湖泊水体,两者间均具有显著差异;桡足类的平均密度在河流水体和湖泊水体间差异不显著,而平均生物量要显著高于湖泊水体.湖泊水体和河流水体在溶解氧、pH、透明度、总溶解固体、盐度、总磷、总氮及铵氮含量上均存在显著差异;冗余分析表明无论是湖泊水体还是河流水体,多数浮游甲壳动物的分布与水温、盐度、化学需氧量(COD_Mn)和总磷等指数呈正相关,只有枝角类中的溞属、船卵溞属种类的分布与水体溶解氧、pH值及透明度呈正相关.     

Spatial and temporal variations of Penilia avirostris and Evadne tergestina (Crustacea,Branchiopoda) in a Tropical Bay,Brazil

We analysed monthly samples collected in Guanabara Bay, with a conical net of 200 m mesh during 1985. The bay was divided into three areas: an outer region (area A), influenced by oceanic waters; an inner region (area C), influenced by fluvial inflow; and a transition region (area B) with intermediate features. Penilia avirostris and Evadne tergestina were observed in the three areas, with greatest densities, however, in the outermost region, which had the highest salinities and lowest temperatures. Penilia avirostris was more abundant in summer (March), a period with the greatest relative densities of nanoplankton. Evadne tergestina was also abundant in summer, but its peak fell in November, a period with a relative increase in microphytoplankton density in the bay. The two species disappeared in winter: Penilia avirostris was absent from May to August, whereas Evadne tergestina disappeared in August and September.     

First record of the family Thamnocephalidae (Crustacea: Anostraca) from Southeast Asia and description of a new species of Branchinella

During a two-year investigation of freshwater microcrustaceans in Thailand, an undescribed species of fairy shrimp of the genus Branchinella Sayce, 1903 in the family Thamnocephalidae, was discovered. This is the first record of the genus and the family from Southeast Asia and the second anostracan reported from Thailand. The new species, Branchinella thailandensis n. sp. appears to be morphologically intermediate between B. kugenumaensis (Ishikawa, 1895) from Japan and east China, and B. madurai Raj, 1951 from India and Pakistan. B. thailandensis n. sp. was collected from several temporary ponds in 11 provinces of the northeast and the central Thailand, often co-occurring with Streptocephalus sirindhornae Sanoamuang, Murugan, Weekers & Dumont, 2000.     

不同营养模式下内蒙古沙漠小型盐湖卤虫种群特征与环境负载力

通过对桑根达莱淖尔卤虫的养殖实验与卵囊解剖,研究了内蒙古沙漠小型盐湖投饵、施肥与自然状态3种营养模式下卤虫的生境、种群动态、生殖特征,分析了环境对卤虫资源的负载力。结果表明:1在起始种群相同的情况下,不同营养模式对种群结构与密度有显著影响;2不同营养模式对个体生长速度影响存在差异,投饵对加快个体生长速度效果最明显,但在性成熟速度方面不同营养模式没有出现统计学显著差异;3不同营养模式对卤虫的怀卵量、卵生/卵胎生比例有显著影响;与空白组相比,投饵组平均怀卵量提高了35.52%—72.71%,施肥组提高了11.34%—26.15%;4卤虫资源的环境负载力为0.3—0.4 kg/m3,加以补充肥料,可提高到0.45 kg/m3,在投喂饲料的情况下可以达到0.5 kg/m3;5卤虫蛋白可开发量按环境负载力的1/3估计,对照组、施肥组和投饵组的相应年开发量分别为2.61—2.98 kg/m3、4.5—5.4 kg/m3和7.51—8.67 kg/m3,滞育卵产量分别为0.73、1.10 g/m3和1.17 g/m3。     

Response of Juniperus phoenicea on sandy dunes in the Camargue (France) to water and saline constraint in summer

The ‘Bois des Rièges’ woodland occurs on the relic littoral dunes in the National Reserve of the Camargue. Although surrounded by brackish ponds and saline lands with very salt groundwater close to the surface, the dunes are covered with non-halophytic vegetation of herbaceous shrubs and trees, including the dominant shrub Juniperus phoenicea. This is due to the presence of a freshwater lens beneath the dunes supplied by rains, and floating in hydrodynamic equilibrium upon the saline aquifer. The importance and duration of the freshwater stock depends on the precipitation-evapotranspiration balance as well as on the size of the dune. From the end of the spring to the autumn rain period this freshwater stock is considerably reduced, while the capillary potential in the zone of aeration of soil and the osmotic potential of the soil solution, influenced by capillary rise of the brackish groundwater, decrease. In summer the vegetation is thus subjected to severe drought caused by lack of water or salt excess, to which it must adjust its biological activity. The water relationships in the soil-plant system have been studied along a transect between the top and the borders of a dune surrounded by saline lands. Using simultaneous water potential measurements of the sunny and shady sides of Juniperus trees daily and seasonal transpiration regulations were studied. The preliminary results indicate that trees on the border of the dune as well as on tops are absorbing water from the same freshwater lens in the middle of the dune.     

Diversity, distinctiveness and conservation status of the Mediterranean coastal dung beetle assemblage in the Regional Natural Park of the Camargue (France)

The Mediterranean region as a whole has the highest dung beetle species richness within Europe. Natural coastal habitats in this region are among those which have suffered severe human disturbance. We studied dung beetle diversity and distinctiveness within one of the most important coastal protected areas in the west Euro‐Mediterranean region (the regional Park of Camargue, southern France) and made comparisons of dung beetle assemblages with other nearby Mediterranean localities, as well as with other coastal protected area (Doñana National Park, Spain). Our finding showed that: (1) The species richness of coastal habitats in the Camargue is low and only grasslands showed a similar level of species richness and abundance to inland habitats of other Mediterranean localities. The unique habitats of the coastal area (beaches, dunes and marshes) are largely colonized by species widely distributed in the hinterland. (2) In spite of their low general distinctiveness, dune and marsh edges are characterized by the occurrence of two rare, vulnerable, specialized and large roller dung beetle species of the genus Scarabaeus. As with other Mediterranean localities, current findings suggest a recent decline of Scarabaeus populations and the general loss of coastal dung beetle communities in Camargue. (3) The comparison of dung beetle assemblages between the Camargue and Doñana shows that, in spite of the low local dung beetle species richness in the Camargue, the regional dung beetle diversity is similar between both protected areas. Unique historical and geographical factors can explain the convergence in regional diversity as well as the striking divergence in the composition of dung beetle assemblages between both territories.     

Responses of the planktonic diatom Asterionella formosa Hassall to abiotic environmental factors in a reservoir complex (south-eastern France)

The River Durance and its main tributary, the Verdon, are both highly regulated rivers flowing in south-eastern France. The course of both rivers is interrupted by a series of reservoirs with quite different geographical, morphometric, climatic, hydrodynamic and chemical characteristics. The planktonic diatom Asterionella formosa Hassall, which has undesirable cyclic effects from the water management point of view, was studied in this complex of reservoirs located in the Mediterranean region. The results indicate that only the monomictic calcareous reservoirs show a bimodal pattern of Asterionella formosa abundance. The population dynamics of this algal species was found to depend on both the morphometric features and the hydraulic mode of management (retention time) used at each reservoir, as well as on the physical (temperature, suspended matter) and chemical (nitrogen, silica, calcium) characteristics of the water.     

The co-occurrence of Artemia parthenogenetica and Branchinella spinosa (Branchiopoda: Anostraca) in a saline pond of south eastern Italy

The co-occurrence of Artemia parthenogenetica Bowen & Sterling, 1978 and Branchinella spinosa Milne-Edwards, 1840, was previously only supposed, on the basis of finding their cysts in the same lagoon, but active stages were never recorded together. In a saline lake in south eastern Italy, populations of the two species were observed for two years. A. parthenogenetica was typical of the early wet season (October–January), while B. spinosa, even if it was present before, developed in the late part of the wet season (February–May). Adult A. parthenogenetica were recorded only in the season 1999–2000. The seasonal distribution of A. parthenogenetica is probably controlled by abiotic conditions (i.e., photoperiod, temperature, conductivity, and rainfall); however, competition between specimens of similar body size (e.g., adults of A. parthenogenetica, and juveniles of B. spinosa) could explain the lower numbers of B. spinosa population in winter. The discovery of cysts of both species deep in the sediment of the lake suggests a long-lasting co-occurrence of these two Anostraca.     

Effect of water-borne copper on respiratory and cardiac function during the early ontogeny of the brine shrimp,Artemia franciscana Kellogg 1908 (Branchiopoda: Anostraca)

There was no direct effect of copper on the ontogeny or function of the heart of the brine shrimp Artemia franciscana in sea water (salinity= 36 mg·ml^-1, 25°C). There was, however, an indirect effect as an increase in copper concentration resulted in a reduced growth rate. There was no difference between the critical O₂ tensions of newly hatched (stage 0/1) nauplii of control and treated (<0.32 and 10.11 mol·l^-1 copper, respectively) individuals. However by developmental stages 4–6, when both the heart and thoracic gills are in the process of differentiating, respiratory performance had improved (i.e. critical O₂ tension decreased from 6.27±0.45 to 4.69±0.24 kPa) in control but not in copper-treated individuals. It is suggested that respiratory impairment of stages 4–6 individuals is unlikely to be related to differences in cardiac performance or cellular respiration. Instead it may be related to metal-related damage to newly differentiating gill tissue and/or by copper in some way compromising the normal ontogenic shift in haemoglobin O₂ affinity. Copper-related respiratory impairment develops at a critical point in brine shrimp organogenesis when a good supply of O₂ is essential for normal development and if compromised may reduce the ability of this species to survive copper exposure.Abbreviations BL body length - BW body weight - HR heart rate - HM heavy metals - SW sea water - P _c critical oxygen tension     

Dynamics of a subtropical plankton community,with emphasis on the copepod Mesocyclops edax

The zooplankton community of a subtropical, eutrophic lake was studied over an annual cycle. Mesocyclops edax, the numerically dominant crustacean, exhibited a stationary age distribution for most of the year (July–March). Per capita growth rates (r) of M. edax approximated zero throughout most of the study, indicating a close correspondence between birth and death rates. High death rates in the spring and summer probably were due to intense predation, since physiological mortality was low and predators were abundant. Multiple regression analyses indicated that much of the variation in M. edax birth rates could be explained by abundance of their animal prey. Other plankton in this lake exhibited considerable seasonality, but not to the marked degree characteristic of temperate populations. The number of zooplankton species was low and cladocerans were scarce, as is characteristic of many eutrophic Florida Lakes.     

Composition of a molluscan assemblage associated with macrophytes in Menzel Jemil (Bizerte lagoon,SW Mediterranean Sea)

The molluscan species composition and diversity associated with macrophytes was studied throughout 1 year at Menzel Jemil station (Bizerte lagoon, north‐west of Tunisia). A total of 7,539 individuals belonging to 13 species were collected. The molluscan assemblage was mainly composed of gastropods (98.12%, nine species), followed by bivalves (1.88%, four species). Hydrobia acuta ranked first with 49.97% of total abundance, followed by Bittium reticulatum (17.97%), Tritia mutabilis (11.38%), Haminoea navicula (8.98%), Phorcus articulatus (5.17%) and Cerithium vulgatum (3.94%). The large number of juvenile molluscs collected confirms the importance of macroalgae and seagrass for mollusc recruitment. Significant temporal variations of species richness, density and diversity indices of the mollusc assemblage have been observed during the year. Multivariate analyses applied to our data revealed significant relationships between the macrophyte composition and associated molluscan assemblage. The BIOENV analysis indicated that water temperature, phosphates concentration and macrophyte biomass were environmental variables most closely associated with the temporal variation of molluscan assemblage.     

Distribution and population dynamics of Porphyra (Bangiales, Rhodophyta) in the southern Western Cape, South Africa

Although Porphyra is commercially farmed in many countries, in South Africa only small harvests of wild populations for sale as nori have been carried out. The discovery that Porphyra improves growth of South African abalone (Haliotis midae) farmed inland-based tanks has led to increased pressure to harvest wild populations. This paper reports on a survey of the distribution and seasonality of Porphyra in the southern Western Cape. Porphyrawas present at all sites surveyed, and showed considerable temporal variation. A significant amount of the Porphyra present is in reserves and therefore protected from harvesting. Close rexamination of one site revealed seasonal populations of Porphyra that occupied different niches dependent on season. Recruitment peaked in spring and autumn, leading to dense summer and winter populations. Summer populations generally grew lower in the eulittoral than winter populations. No pattern in the mortality of larger thalli wasde tected, though sporeling mortality was high following recruitment peaks. Although it seems that most sites in the southern Western Cape are suitable for harvesting, the taxonomy of the genus in the region urgently needs revision if populations are to be appropriately managed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Population dynamics of two small cichlid fish species in a tropical man-made lake (Lake Kariba)

The population dynamics of two small cichlid fishes (Pharyngochromis darlingi andPseudocrenilabrus philander) were studied in Lake Kariba, a very large African man-made lake. They are of no economic importance but make up about 14% and 7% respectively of the inshore fish population and are the major components of the diet of fish-eating birds on the lake.P. darlingi isthe larger species (L = 156.5 mm) and is found on both shelving and steep, eroding shores. Its mortality rate differs in each habitat (Z = 0.44 and 0.72 month^–1 respectively), only 0.79% survive for 12 months and its % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaiaac+% cadaqdaaqaaiaadkeaaaaaaa!384D!\[P/\overline B \] ratio is 5.45 (on shelving shores).Ps. philander is smaller (L = 83.9 mm) and is restricted to shelving areas with abundant vegetation. Its monthly mortality rate was high (Z = 7.69), only 0.05% survive to 12 months whilst its % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiuaiaac+% cadaqdaaqaaiaadkeaaaaaaa!384D!\[P/\overline B \] ratio was very high (7.69). The estimates of growth obtained forP. darlingi differ considerably from those given in an earlier study in Lake Kariba and some possible reasons for this are discussed. In suitable habitats, the combined production of both species could be 40 kg ha^–1 yr^–1 which indicates their potential importance to the ecology of the lake.     

International study on Artemia XLIX. Salinity effects on survival,maturity, growth,biometrics, reproductive and lifespan characteristics of a bisexual and a parthenogenetic population of Artemia

Two Artemia populations, a bisexual from San Francisco Bay (California, USA) and a parthenogenetic from Tanggu area (Tianjin province, People's Republic of China) are assayed for their tolerance and fitness in various salinity levels. This study was carried out under laboratory conditions where salinity effects upon special characteristics of the two Artemia populations, such as survival, growth rate, maturation, morphology, fecundity and life duration, were recorded. This evaluation revealed that the two populations examined exhibits significant differences in their response against elevated salinity levels. Furthermore, specific biometric parameters can be a useful tool for the discrimination and/or determination of their distribution in a mixed population, which, in fact, is the case in Tanggu salt works. Artemia franciscana seems to be a more effective colonizer at higher salinities. The data presented in this study may generate useful suggestions for proper management of the solar saltworks at Tanggu although further experimentation is needed.International interdisciplinary study on Artemia populations coordinated by the Laboratory of Aquaculture & Artemia Reference Center, University of Ghent, Belgium.