A new species of Halicyclops (Copepoda,Cyclopoida, Cyclopidae) from a lagoon system of the Caribbean coast of Colombia

Plankton samples obtained from the lagoon system Laguna Navío Quebrado, in northern Colombia, yielded male and female specimens of an undescribed cyclopoid copepod of the genus Halicyclops. The new species belongs to the highly diverse and widely distributed thermophilus-complex. It closely resembles Halicyclops clarkei Herbst, 1982 from Louisiana and Halicyclops bowmani Rocha & Iliffe, 1993 from Bermuda. These species share the same armature of P1-P4EXP3, with a 3443 spine formula and the terminal antennary segment with 5 setae. However, Halicyclops gaviriai sp. n. can be separated from both Halicyclops clarkei and Halicyclops bowmani by the morphology of the anal pseudoperculum, the proportions of the fourth antennulary segment, the length of the inner basipodal spine of P1, the P1EXP/inner basipodal spine inner length ratio and the length/width ratio of the caudal rami. This is the third species of Halicyclops recorded from Colombia and the first one described from this country. With the addition of Halicyclops gaviriai sp. n., the number of species of Halicyclops known from the Neotropics increases to 19. The regional diversity of the genus is probably underestimated.     

Seasonal and areal features of the lagoonal environment in Lake Nakanoumi,a shallow coastal lagoon in Japan

Lake Nakanoumi is a shallow coastal lagoon connected with the Japan Sea by a narrow channel. Over the past decade, land reclamation resulted in a 33% reduction of the lagoon's surface area. The remaining water basin of Lake Nakanoumi is scheduled to be artificially freshened to supply irrigation water for the newly reclaimed lands. This paper deals with the seasonal and areal features of the lagoonal environment prior to the beginning of the artificial desalinization.     

Relationship between current velocity,depth and the invertebrate community in a stable river system

The relationship between invertebrate densities, current velocity and water depth was studied in the Dan River, northern Israel. Maximum current preferences ranged from 5–120 cm sec^–1, and depth preferences ranged from 5–60 cm. Thirty-five taxa of invertebrates were collected by means of colonization cages. Larval and adult stages of 3 Elmidae (Coleoptera) species were treated separately: Limnius letourneuxi, Grouvellinus caucasicus and Elmis rioloides. Differences in current preference were observed between larval and adult stages of the same species of Elmidae. Taxa were also grouped according to preference for turbulence. Wide ranges of depth and current velocity preferences were observed. Most of the taxa were found at between 80–100 cm sec^–1 and at depths of less than 30 cm. A correlation between species diversity and current velocity was established. Velocities of 60–80 cm sec^–1 contained the greatest overlap of faunal preference. The sensitivity of selected species to stream flow reduction is discussed.IES Laboratory, Department of Zoology, Hebrew University; and the Nature Reserves Authority     

Influence of environmental conditions on the distribution of Amphipoda,Talitridae, in the lagoon complex of Ghar El Melh (north‐east of Tunisia)

The study of the spatiotemporal distribution of talitrid amphipods was carried out along a transect in three stations belonging to the lagoon complex of Ghar El Melh, namely the supralittoral zones of the old harbour of Ghar El Melh, the opposite to Boughaz and Sidi Ali Mekki lagoon. Four species belonging to Talitridae family with two different genera were identified at all stations. These species are Orchestia gammarellus, Orchestia mediterranea, Orchestia stephenseni and Platorchestia platensis. The first two species were collected during the four seasons. The study of the density showed that the most important global mean density in talitrid was found in the supralittoral zone of opposite to Boughaz. In addition, statistical analysis showed a significant difference in the seasonal distribution of amphipods based on plant associations. Furthermore, the highest diversity of talitrid was observed in the winter in the supralittoral zone of opposite to Boughaz and in summer in the supralittoral zones of Sidi Ali Mekki lagoon and the old harbour of Ghar El Melh. Results showed that at all stations, a highly significant correlation of amphipod community with Cymodocea banquette was observed. Moreover, principal component analysis showed that the distribution of the different species depends on climatic and edaphic factors.     

Tufa deposition and periphyton overgrowth as factors affecting the ciliate community on travertine barriers in different current velocity conditions

A characteristic of aquatic systems in karstic region is the formation of tufa – the product of calcium carbonate precipitation. Artificial substrata (glass slides) were used to investigate the influence of tufa deposits at two different current velocities (5 cm s^–1 and 50 cm s^–1) on the ciliate assemblages in periphyton. After two-month exposure periods, periphyton biomass and tufa deposit were c. three times greater at 50 cm s^–1 than at 5 cm s^–1. Ciliate population density was also higher on artificial substrata exposed in a lotic than in a lentic microhabitat (the overall mean number of ciliates at 5 cm s^–1 was 122 ind. cm^–2, and at 50 cm s^–1 497 ind. cm^–2). At each of the two observed current velocities, a Principal Components (PCA) ordination of the colonized ciliate associations showed a spatial separation of the associations that developed under two different conditions of tufa deposition. During the period of greater tufa deposit, associated with greater periphyton overgrowth rate, the ciliate communities had higher species diversity (a higher number of species and a lower number of individuals). Species diversity of ciliates had a positive nonlinear relation to tufa deposition rate. These results suggest that artificial surfaces covered by a rough tufa layer associated with greater periphyton biomass offer diverse conditions for colonization by ciliates.     

Seasonal distribution of phytoplankton in the Aby lagoon system,Ivory Coast,West Africa

Seasonal variability of phytoplankton species composition, abundance and physical and chemical factors influencing phytoplankton dynamics were investigated in the Aby lagoon system, south-eastern Ivory Coast, covering the main climatic seasons in 2006–2007. Seasonal and spatial variability of nutrient concentrations in the system were influenced by freshwater inflow from the Bia and Tanoé rivers. The decrease in the salinity gradient in Aby Lagoon, which is permanently stratified during the long dry season, increased the bottom inputs of soluble reactive phosphate and soluble reactive silicate which, in combination with good light penetration during the long dry season, enhanced phytoplankton production in the system. During the rainy seasons, water discharges into the system washed phytoplankton biomass out, preventing the development of blooms. Overall, 192 taxa from eight phyla were recorded: Bacillariophyta (32%), Chlorophyta (31%), Cyanobacteria (23%), Euglenophyta (12%), Dinophyta (0.5%), Xanthophyta (0.5%), Chrysophyta (0.5%) and Rhodophyta (0.5%). During the long dry season, Cyanobacteria cells comprised >50% of the phytoplankton abundance. The main phytoplankton taxa responsible for this high abundance were Microcystis aeruginosa, Oscillatoria princeps, Pseudanabaena limnetica, Aphanizomenon sp. 2 and Anabaena planctonica.     

Modifications in habitat use patterns and trophic interrelationships in the fish fauna of an oligotrophic artificial lake: Sainte Croix (Provence,France)

Lake Sainte-Croix is a hydro-electric reservoir on the river Verdon that came into operation about 16 years ago. The area of the lake is about 22 km² and the volume about 767 Mm³. The water level drops by as much as 16 m in winter. Sainte-Croix is a warm monomictic oligotrophic lake. The indigenous fish fauna of the Verdon originally included 8 species. Successive stocking has raised this number to 17. In catches made in 1976–1977 with 27 mm mesh nets, 80 to 90% of the fish with a body size of between 15 and 25 cm were of the four main species indigenous to the river before the dam was built: Leuciscus cephalus, Barbus fluviatilis, Chondrostoma toxostoma, Salmo trutta. Catches made at same period with 14 mm mesh nets gave only Chondrostoma toxostoma and Leuciscus cephalus.Changes in the fish fauna were apparent from catches made in 1984 and 1987 with nets of the same mesh size. There was a marked demographic increase of roach, and more recently of bleak and gudgeon, all three species introduced after the construction of the dam. At the same time, there was a decrease in catch frequency of Ch. toxostoma, L. cephalus and B. fluviatilis in the downstream area of the lake. Stomach content analysis carried out in different seasons on the six most abundant species of the lake (roach, toxostome, chub, bleak, perch and gudgeon) provided evidence on the trophic organisation of the fish fauna. We have measured niche breadth for each species by the Simpson diversity index and niche overlap by the Pianka index. Bleak is the only species to feed on zooplankton in open water. Roach is a particularly opportunistic feeder, sometimes taking plankton, but at Sainte-Croix it is exclusively herbivorous and benthophagous. Niche overlap between these two species is slight or null, depending on the season. On the other hand, there is a high degree of overlap between roach and chub and between roach and toxostome. The decrease in toxostome and chub frequency in the downstream area of the lake, where roach is most abundant, would appear to be a competitive exclusion phenomenon. There is high niche overlap between bleak and young perch, which partly explains the low abundance of the latter species; other contributory factors are the scarcity of zooplankton inshore, and the scarcity of zoobenthos resulting from the drop in the water level in winter.     

Size-assortative pairing in the lotic amphipod <Emphasis Type="Italic">Gammarus zaddachi</Emphasis>, an examination of hypotheses and the influence of current speed

Three main hypotheses have been put forward to explain size-assortative pairing in gammarid amphipods: microhabitat separation, sexual selection and loading constraint. In order to determine which hypothesis best explains this phenomenon in the estuarine species Gammarus zaddachi, I first measured the body lengths and dry weights of precopula pairs collected from two field sites with substantially different current speeds. Second, I performed three laboratory experiments in order to estimate the importance of the following processes: (1) male choice; (2) male–male competition and (3) male–female acceptability. The loading constraint hypothesis seemed best supported by the data in that field-collected male G. zaddachi size correlated well with female size in precopula pairing in both fast and slow flowing water. In the laboratory, males preferred females of their same size group (large versus small), and ‘won’ them in the male–male competition experiments. Size-assortative pairing is thus likely a consequence of the loading constraints imposed upon these males by virtue of them having to carry and manoeuvre their partners through flowing water, while attempting to maintain station in an optimal microhabitat. Males may therefore forego the largest, most fecund females, in favour of a practicable payload (small male–large female pairings were rare). However, there seems to be a lower limit to this selection, indicated by the high degree of cannibalism on small females by large males.     

Effects of the halocline on water quality and phytoplankton composition in a shallow brackish lake (Lake Obuchi, Japan)

The relationships of the halocline to both water quality and phytoplankton composition in Lake Obuchi, a shallow brackish lake in northern Japan, were investigated from April 2001 to December 2004. The halocline in this lake became stronger in summer (July–September, mean maximum density gradient 4.3–5.8 ρ_tm⁻¹) but weaker in spring, fall, and winter (1.9–3.3 ρ_tm⁻¹). Although the difference in water quality between the upper and lower layers separated by the halocline was high in summer, nutrients (PO₄³⁻-P and NH₄⁺-N) were eluted from the bottom sediment as levels of dissolved oxygen decreased in the bottom layer because of the strong stratification caused by the halocline formed over the long term. Moreover, phytoplankton taxa composition also differed between the upper and lower layers in summer, but was similar in other seasons. The dominant phytoplankton taxa in the upper layer in summer were Skeletonema costatum and Cyclotella spp., whereas in the lower layer, Gymnodinium spp. (Dinophyceae) and Chlorophyceae, which prefer eutrophic and low dissolved oxygen conditions, dominated. This suggests that the halocline was related to differentiations in both water quality and ecosystem components between the upper and lower layers in the brackish lake water.     

The structure,diversity and somatic production of the fish community in an estuarine coastal lagoon,Ria de Aveiro (Portugal)

The present study aims to determine biological fish production of a lagoon and relate this to the commercial fisheries yield. The fish community of an estuarine lagoon in the west coast of Portugal was sampled between November 1998 and November 2000 to estimate the production ecology of the community, including somatic production, population size, species richness, species diversity, and biomass. Using the Allen curve method of determination, the total annual fish production of all fish species in the lagoon was calculated at 90.3 tonnes or 2.1 g m⁻² year⁻¹ in the first year and 106.7 tonnes or 2.5 g m⁻² year⁻¹ in the second year. The marine seasonal migrant species, sardine, Sardina pilchardus, which colonises the lagoon during the juvenile period of its life stages, produced more than 35 tonnes in each year and accounted for >39 and >33%, in the first and second year respectively, of the total fish production in this lagoon. Sardine was numerically more abundant (18,217 specimens) but due to their small size contributed only 13% to the total biomass. Sardine was thus the most important fish species in terms of the consumption and production processes of the whole fish community in this system. Commercial fisheries’ records indicate that approximately 300 tonnes per annum of fish are taken from the lagoon, which corresponds to three times more than the estimated production in the lagoon. Thus, if it exists, the sustainability of the fishery appears to depend on the immigration of fish from the adjacent coastal area and it is questioned whether the fishery is sustainable in the long-term. The findings indicate that careful and effective management of the lagoon is required to ensure a long-term healthy aquatic environment and sustainable catches in the future.     

The effect of water temperature,current velocity and suspended solids on the distribution,growth and seasonality of Lemanea fluviatilis (C. Ag.), Rhodophyta,in the river Usk and other South Wales rivers

Two surveys of Lamanea in South Wales rivers have given details of its distribution, seasonality and range of tolerance to various environmental parameters, with particular reference to temperature, current velocity and suspended solids.Temperature, current velocity and suspended solids had most effect. Such findings were confirmed by principal component and correlation coefficient analysis.These investigations also suggest that abundant growths of Lemanea may be used in a limited manner as indicative of oligotrophic and metal free waters especially during Spring.In addition, transplants of Lemanea from the upper to the lower reaches of the River Usk and vice versa were studied to clarify the effect of suspended solids in nature.Using the ¹⁴C technique for primary production proved to be a successful method with Lamanea for comparison with chlorophyll a extraction and phycoerythrin. The importance of the latter in energy transfer for photosynthesis was revealed for this genus. A combination of various simple and cheap methods for the extraction of the pigment phycoerythrin was used successfully for the first time in red algal studies.Procedures for estimating percentage cover, standing crop and the presence/absence of the plant are given and the statistical reliability of the methods is evaluated.     

Twentyfive years of changes in the distribution and biomass of eelgrass,Zostera marina,in Grevelingen lagoon,The Netherlands

The wax and wane of the eelgrass (Zostera marina L.) population in Grevelingen lagoon (East Atlantic; The Netherlands) has been documented for over 25 years, together with quantitative and semi-quantitative data on environmental variables. The population expanded after the closure of the Grevelingen estuary in 1971, but declined from 4600 ha surface area in 1978 to less than 100 ha in 1993. There is little causal evidence which factors are responsible for the observed dynamics of the population. The incomplete picture emerging from the data is that of an extremely impoverished eelgrass population, living under constant oligo-mesotrophic marine conditions. Both the sexual and the vegetative modes of reproduction are severely stressed by environmental variables, most likely a combination of low temperatures, high salinity, low dissolved silicate and low ammonium concentrations. Survival of the population asks for the restoration of moderate estuarine conditions.Contribution No. 2180 of the Netherlands Institute of Ecology, Nieuwersluis, The Netherlands.     

Population structural changes in single species of flour beetles with ozone as an environmental factor

1. Although a 5 hour monthly exposure for 16 months to 45.0 ppm O₃ at 0.3l/min. reduced the numbers of individuals in single-species populations of T. confusum and T. castaneum, it did not result in elimination or a significant decrease in numbers which would be useful in a control program for these flour beetle species.
2. During the first 5 months of culture, ozone had a stimulating effect on productivity of T. confusum; a similar effect was not noted for T. castaneum.
3. Control of flour beetles by ozone in stored-products seems unlikely; however, ozone in an integrated control program with ionizing radiation might prove beneficial.
4. Biological interpretations are offered to explain the responses of these species to ozone exposures.
5. Further research is warranted to define ozone modifications in pest control programs and on stored-products per se.

     

Ethoxyresorufin O-deethylase (EROD) activity and fluctuating asymmetry (FA) in Zosterisessor ophiocephalus (Teleostei, Gobiidae) as indicators of environmental stress in the Venice lagoon

The impact of environmental stress on the grassgoby, Zosterisessor ophiocephalus, wasstudied at both biochemical and morphologicallevels, by comparing three sites in the Venicelagoon (the Northern, Central and Southernbasins) which differ in terms of the degree ofanthropogenic disturbance, in particular withregard to organic sediment contamination. At abiochemical level, the hepatic ethoxyresorufinO-deethylase (EROD) enzyme activity wasmeasured as a biomarker of the degree oforganic pollution (in particular regardingcontamination by PCBs and Dioxins). At amorphological level, the amount of fluctuatingasymmetry (FA) with regard to four bilateraltraits (postorbital length; otolith area;minimum otolith diameter; maximum and minimumotolith radii) was measured as a long termindicator of developmental stress. The ERODactivity was higher in grass gobies from theCentral basin, whereas the amount of FA washigher in the gobies collected from theNorthern basin. Both measurements indicatedthat the Southern basin was affected by lowlevels of environmental stress (low ERODinduction and a lower amount of FA). Theresults were discussed in the light of both theenvironmental differences among the threebasins and the different levels of biologicalorganisation at which the two indicators act.     

Water footprint and irrigation use efficiency of important crops in Northern Cyprus from an environmental,economic and dietary perspective

Availability of freshwater is currently one of the most important limiting factors for crop production and food security throughout the world. Northern Cyprus is one of the world’s most important countries that has been facing drought and salinization problems since the 1970 s. The present study aimed to determine the irrigation use efficiency (IUE), irrigation economic productivity (IEP), irrigation economic efficiency (IEE) and irrigation dietary efficiency (IDE) of some major crops in Northern Cyprus to ensure better planning for sustainable water management, not only for Northern Cyprus but also for all countries facing similar problems. The results of the present study showed that both carob and fig crops require the least amount (24 L) of irrigation to produce 1 kg of fruit, and “open field” lettuce and “greenhouse” eggplant require the least amount (10 and 16 L) of irrigation to produce 1 kg of vegetables in Northern Cyprus. The irrigation economic productivity (IEP) and irrigation dietary efficiency (IDE) of crops were also found to be significantly different and meaningful for different crops. Our results showed that reshaping the distribution of crops based on their water consumption would reduce the use of water resources while continuing to feed the population.     

云南横断山区蚤类物种多样性的地理分布趋势与重要环境因素的关系

根据云南横断山区具代表性的7个山系共9个样区山地蚤类及其宿主动物的垂直分布调查结果,并参考以往的部分调查资料,对所获数据进行统计学处理,应用不同山系样区各垂直带蚤类物种多样性的平均值作为指标,就云南横断山区蚤类物种多样性的地理分布趋势和规律,与宿主动物和重要环境因素的关系等问题进行了分析和探讨。结果显示,蚤类物种多样性的地理分布趋势是由西北→南→东→北呈递减的趋势。与变化趋势密切相关的重要因素是水湿条件,其次是经度的影响。另外还与蚤类的丰富度、地理环境、垂直带和人们的生产活动等因素有关。研究认为,形成蚤类与宿主动物间多样性地理分布趋势上的差异的主要原因是对环境的适应性不同,其中水湿条件就是很重要的因素之一。研究还发现,横断山蚤类在我国蚤类区系中是多样性最高的地区,它充分地反映了横断山区栖息地异质性对物种数的重要影响,并说明栖息地异质性对物种—面积关系起着重要作用。     

Ecophysiological responses of the larch species in northern Japan to environmental changes as a basis for afforestation

For sustainable use and suitable management of larch plantations, we must clarify the ecophysiological responses of larch species to environmental changes. The physical environment has been changing dramatically, e.g., increase in atmospheric CO₂ concentration ([CO₂]), nitrogen (N) deposition, and atmospheric ozone concentration ([O₃]), and these changes may negatively affect growth of larch species. This review summarizes the previous experimental studies on the ecophysiological responses of larch species to elevated [CO₂], soil acidification, elevated [O₃], and N load. Based on the advanced studies, although elevated [CO₂] will stimulate the productivity of larch, increase of [O₃] and severe soil acidification will reduce it. Increase of N deposition, at least, will not negatively affect larch productivity. Finally, we propose the future direction for investigation to understand the mechanism of the responses of larch species and to predict the associated risk.     

Long-term change in water transparency before and after the loss of eelgrass beds in an estuarine lagoon,Lake Nakaumi,Japan

Long-term changes in Secchi disk transparency in Lake Nakaumi, Japan, from 1932 to the present, which includes the periods before and after the loss of eelgrass (Zostera marina L.) beds, were compiled from previous reports. During the first (July 1932–February 1934) and the second (January 1949–November 1950) periods, the mean transparency was greater than 3 m at all observed stations. Data during the third period (July 1954–March 1956) are only available for the station at the center of the lake. The mean transparency during the third period was significantly lower than that of the second period but higher than the mean during the fourth period. This observation suggests that the decrease of transparency occurred during the third period. Because the decline of eelgrass beds in Lake Nakaumi occurred in the mid-1950s, the decrease of transparency most likely resulted from the shift in primary producers from submerged macrophytes to phytoplankton. Although the maximum transparency sometimes exceeded 3 m, mean transparencies during the fourth period (May 1975–December 2003) were less than 2 m at all stations, significantly lower than those during the first and second periods. The shift in the chief primary producer, from benthic macrophytes to phytoplankton, caused a subsequent shift in secondary producers. The opportunistic filter-feeding bivalve Musculista senhousia, regarded as a biofouling species of local fisheries, increased in Lake Nakaumi. The long-term monitoring data of transparency suggested that restoration of submerged aquatic vegetation may be indispensable for the remediation of the lake environment in this shallow eutrophic lagoon.     

Artificial mussels as indicators of metal pollution in freshwater systems: A field evaluation in the Koekemoer Spruit,South Africa

There has been a recent increase in water quality problems in South Africa. The monitoring of water resources is important for the continued management of water resources. The use of artificial mussels (AMs) as passive sampling devices in the monitoring of metals within a freshwater system was evaluated in a recent field study. Correlation testing was conducted between the AMs and Melanoides tuberculata for As, Cd, Cr, Co, Cu, Pb, Mn, Ni, U, V and Zn. It was found that a positive significant correlation exists between AMs and M. tuberculata with regards to As, U, and Co accumulations. The trend of metal accumulation between AMs and M. tuberculata were found to be similar for all of the metals tested. Site 2 which is located close to a gold mine, was found to have the highest metal concentrations in this study. This study confirms the hypothesis that AMs can be used as a useful tool for monitoring metals in freshwater.     

Factors affecting the distribution of benthic and littoral rotifers in a large marine lagoon,together with the description of a new species

Diffusion plays an important role in the exchange processes between lake sediments and the overlying water. Compounds entering the sediments usually have to penetrate through a certain mud thickness, where a reaction may then occur, while compounds being released have to diffuse through the interstitial water before escaping into the lake water.In this article mathematical functions are given which describe certain cases. They are all based on the differential diffusion equation of Fick, but for different boundary conditions different mathematical solutions of partial differential equations are needed. Four of these are presented in this paper, covering the cases of a compound diffusing into the sediments, with or without a chemical reaction occurring in the sediments, combined with either a constant or a non-constant concentration in the water.Furthermore a numerical approach is proposed in which the calculations are made by an iteration process over time and space. The results are presented as a series of concentrations as a function of time and depth in the sediment layer. It is shown in the first place that the time and the space steps must be sufficient small in agreement with the dimensions and time scale of the processes studied in order to obtain a satisfactory precision. The results can be fitted to a simplified exponential equation of the form (A · e^{–·t b} – B), which can be used for a quick assessment of special cases, depends on porosity, ratio between water and mud height; b 0.667. Furthermore this equation can be used to extrapolate from laboratory experiments with the sediments of a specific lake to results valid for the lake itself.The numerical model has also been used to describe the backward diffusion of an eventual product of a chemical reaction, which will diffuse further downward, but also upward. This is e.g. the case for the N₂O production during denitrification experiments when acetylene is applied as an inhibitor.Finally, the application of so called peepers and benthic chambers is discussed, while many of their disadvantages are explained.