The Relationship between Phytoplankton Diversity and Community Function in a Coastal Lagoon

The decrease of biodiversity related to the phenomena of global climate change is stimulating the scientific community towards a better understanding of the relationships between biodiversity and ecosystem functioning. In ecosystems where marked biodiversity changes occur at seasonal time scales, it is easier to relate them with ecosystem functioning. The objective of this work is to analyse the relationship between phytoplankton diversity and primary production in St. André coastal lagoon – SW Portugal. This lagoon is artificially opened to the sea every year in early spring, exhibiting a shift from a marine dominated to a low salinity ecosystem in winter. Data on salinity, temperature, nutrients, phytoplankton species composition, chlorophyll a (Chl a) concentration and primary production were analysed over a year. Modelling studies based on production-irradiance curves were also conducted. A total of 19 taxa were identified among diatoms, dinoflagellates and euglenophyceans, the less abundant group. Lowest diversities (Shannon–Wiener index) were observed just before the opening to the sea. Results show a negative correlation (p<0.05) between diversity and chlorophyll a (Chl a) concentration (0.2–40.3 mg Chl a m⁻³). Higher Chl a values corresponded to periods when the community was dominated by the dinoflagellate Prorocentrum minimum (>90% of cell abundance) and production was maximal (up to 234.8 mg C m⁻³ h⁻¹). Maximal photosynthetic rates (P_max) (2.0–22.5 mg C mg Chl a⁻¹ h⁻¹) were higher under lower Chl a concentrations. The results of this work suggest that decreases in diversity are associated with increases in biomass and production, whereas increases correspond to opposite trends. It is suggested that these trends, contrary to those observed in terrestrial and in some benthic ecosystems, may be a result of low habitat diversity in the water column and resulting competitive pressure. The occurrence of the highest photosynthetic rates when Chl a is low, under some of the highest diversities, suggests a more efficient use of irradiance under low biomass–high diversity conditions. Results suggest that this increased efficiency is not explained by potential reductions in nutrient limitation and intraspecific competition under lower biomasses and may be a result of niche complementarity.     

Considerations for the development of a terrestrial index of ecological integrity

Ecological systems are composed of complex biological and physical components that are difficult to understand and to measure. However, effective management actions and policy decisions require information on the status, condition, and trends of ecosystems. Multiple levels of information are needed to make effective decisions and the ideal indicators for measuring ecosystem integrity will incorporate information from multiple dimensions of the ecosystem. A terrestrial index of ecological integrity would be a useful tool for ecosystem managers and decision makers. The ideal requirements of the terrestrial index of ecosystem integrity (TIEI) are that it be comprehensive and multi-scale, grounded in natural history, relevant and helpful, able to integrate concerns from aquatic and terrestrial ecology, and that it be flexible and measurable.The objective of this research is to investigate if an index, or indices, could be developed that would summarize the condition of ecosystems so that changes can be tracked over time and this information utilized as a tool to support environmental decision making.     

Ecosystem health assessment on the hill and gully area of loess Plateau in Inner Mongolia, China

Maintenance of ecosystem health is the primary focus of a sound ecological restoration. Yet methods involved in quantifying and assessing the health level remain a challenge to the ecological community. In this study, we selected the hill and gully area of Loess Plateau, Inner Mongolia, China, as our study area. The soil and water erosions in this area continue to be responsible for many environmental problems in northern China because of its fragility and long disturbance history. In this study, we developed an assessment method of indicator system (AMIS) based on analytical hierarchy process (AHP), fuzzy mathematics, and the theory of net-hierarchy. At ecosystem or catchment scale, three sample areas, that is (1) intact vegetation (i.e., Aguimiao Natural Reserve, 110°45′E, 39°28′N), (2) reconstructed vegetation (Wufendigou Soil and Water Conservation Experimental Area, 111°07′E, 39°45′N), and (3) severely degraded vegetation (Yangquangou Catchment, 111°06′E, 39°45′N) in the hill and gully area of Loess Plateau in Inner Mongolia, China, were selected to examine ecosystem vigor, organizational structure, service function, and soil health. We applied the AMIS for all three landscapes by categorizing each ecosystem into five health levels. We found that the health index for reconstructed vegetation were at levels of IV, II, IV, and III, while those of degraded vegetation were ranked at V, IV, V, and IV. Overall, the comprehensive ecosystem health index of reconstructed vegetation was lower than that of intact vegetation but higher than that of degraded vegetation. The health index for reconstructed vegetation was at level III, and that of degraded vegetation was still at level IV. The contributing values were: organization structure > soil health > vigor > service function. Based on our results and assessments, we proposed several management recommendations and methods for restoring the regional ecosystems. __________ Translated from Acta Ecologica Sinica, 2005, 25(5): 1048–1056 [译自: 生态学报, 2005, 25(5): 1048–1056]     

Variability of nutrients and phytoplankton biomass in a shallow brackish water ecosystem (Chilika Lagoon, India)

Seasonal and spatial variations in water quality parameters, such as nutrients [NH₄ ⁺–N, NO₂⁻–N, NO₃⁻–N, PO₄³⁻–P, total nitrogen (TN) and total phosphorus (TP)], Secchi disc depth, salinity, dissolved oxygen, chlorophyll a, primary productivity and phytoplankton standing stock, were studied in Chilika Lagoon (from 27 sampling locations) during 2001–2003 to assess the present ecological status. The study was undertaken after a major hydrological intervention in September 2000, which connected the lagoon body and the Bay of Bengal via a manmade opening (new mouth). Current and old data on water quality were also compared to establish the changes that had occurred after the hydrological intervention. Multivariate techniques and gridding methods were used to investigate the spatial and seasonal variability of the data and to characterize the trophic evolution of the basin. Results of principal component analysis (PCA) indicated that the 27 stations can be classified into five groups based on similarities in the temporal variation of nutrients, chlorophyll a concentration, salinity, and other physicochemical parameters. The tributaries and the exchange of lagoon water with the Bay of Bengal most probably determine the water quality and the dynamics of the ecosystem. Hydrodynamics of the lagoon, weed coverage, input of urban sewage through tributaries and agricultural runoff are probably the key factors controlling the trophic conditions of the lagoon. An increase in salinity and total phosphorus was noted after the new mouth was opened, while the total suspended sediment load, the water column depth, and nitrogenous nutrients decreased. The new mouth opening also brought changes in the phytoplankton species composition.     

A genetically modified solvent-tolerant bacterium for optimized production of a toxic fine chemical

The aim of the study was to investigate whether toxic fine chemical production can be improved using the solvent-tolerant Pseudomonas putida S12 in a two-liquid-phase system consisting of aqueous media and a water-immiscible octanol phase with production of 3-methylcatechol from toluene as the model conversion. For this purpose the genes involved in this conversion, todC1C2BAD from P. putida F1, were introduced into P. putida S12 with high stable expression. Production of 3-methylcatechol was monitored in batch incubations with different media using a single medium and a two-liquid medium–octanol system. The maximum concentration of 3-methylcatechol increased two-fold using the two-liquid medium–octanol system, irrespective of the selected medium. Received: 29 December 1999 / Received revision: 29 February 2000 / Accepted: 6 March 2000     

A trait-based approach to species’ roles in stream ecosystems: climate change,community structure,and material cycling

The sustained decline in habitat quality and community integrity highlights the importance of understanding how communities and environmental variation interactively contribute to ecosystem services. We performed a laboratory experiment manipulating effects of acclimation temperature (5, 15, 25, and 35°C) on resource acquisition, assimilation and subsequent ecosystem services provided by eight freshwater mussel species. Our results suggest that although freshwater mussels are broadly categorized as filter feeders, there are distinct nested functional guilds (thermally tolerant and sensitive) associated with their thermal performance. At 35°C, thermally tolerant species have increased resource assimilation and higher rates of contributed ecosystem services (nutrient excretion, benthic–pelagic coupling). Conversely, thermally sensitive species have decreased assimilation rates and display an array of functional responses including increased/decreased benthic–pelagic coupling and nutrient excretion. Although thermally sensitive species may be in poorer physiological condition at warmer temperatures, their physiological responses can have positive effects on ecosystem services. We extrapolated these results to real mussel beds varying in species composition to address how shifts in community composition coupled with climate change may shift their contributed ecological services. Comparative field data indicate that two co-existing, abundant species with opposing thermal performance (Actinonaias ligamentina, Amblema plicata) differentially dominate community biomass. Additionally, communities varying in the relative proportion of these species differentially influence the magnitude (benthic–pelagic coupling) and quality (N:P excretion) of ecosystem services. As species are increasingly threatened by climate change, greater emphasis should be placed on understanding the contribution of physiological stress to the integrity and functioning of ecosystems. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Similarities between predator mite populations (Acari: Gamasina) from natural forests in the Bucegi Massif,Romania

Ecological research of gamasid mites was carried out in three natural forest ecosystems with Picea abies (1350 m a.s.l.), Abies alba (950–1000 m a.s.l.) and Fagus sylvatica (1200 m a.s.l.) situated in the Bucegi Massif, Southern Carpathians, Romania during 2001–2003. In the studied forest ecosystems, the taxonomic structure of gamasids was represented by 11 families (Epicriidae, Parasitidae, Veigaiidae, Ameroseiidae, Aceosejidae, Rhodacaridae, Macrochelidae, Pachylaelapidae, Laelapidae, Eviphididae and Zerconidae), with 39 genera and 97 species. The maximum number of species was recorded in the ecosystem with Abies alba (80), followed by the ecosystem with Fagus sylvatica (73), while the minimum in the ecosystem with Picea abies (68). 2,016 samples, 97 species with 23,441 individuals were analysed. In order to show similarities between predator mite populations from these areas, the vegetation and some abiotic parameters of the soil (temperature, humidity, pH) were analysed and described. Similarities between gamasid mite populations from the investigated ecosystems were analysed using the Jaccard index (q). The highest similarity index (q = 0.706) was recorded between gamasids identified in Picea abies and Abies alba forests, at soil level, in comparison with those from Abies alba and Fagus sylvatica forests (q = 0.656). Based on the similarity index, it is discussed that the gamasid population structure was influenced by the type of soil, the specific composition of the herbaceous, shrub and tree layers, the microclimatic factors, all characteristic for each studied ecosystem.     

Distribution of the oriental weatherloach, Misgurnus anguillicaudatus, in paddy fields and its implications for conservation in Sado Island, Japan

The distribution of the oriental weatherloach, Misgurnus anguillicaudatus, together with related environmental factors were surveyed at 185 paddy field locations on Sado Island in Japan. This was associated with the reintroduction of the Japanese crested ibis, Nipponia nippon, which prefers to feed on the loach. Loach were found to be present at 90 locations (49%). Analysis with GIS, GLM and AIC revealed that positive factors for the loach distribution included the presence of an earth ditch, the connections at outlets and the proportion of paddy field area within an 800 m radius. Conversely, pumping-up water irrigation and flow irrigation affected loach distribution negatively. In an interview survey that was conducted concurrently, older farmers in the area recalled that the loach had once been distributed over almost the entire island (89/96, 93%) about half a century ago. The farmers also suggested that the impact of agricultural chemicals was one of the main reasons for loach reduction or local extinction. A map of the current potential loach distribution was made using the best fit model from GIS variables. The loach was expected to be distributed in the Kuninaka region with high probability (60–100%) and in patches in the Osado and Kosado regions with low–medium probability (10–50%). As a feasible scenario for the conservation of the loach, another predictive map of the loach distributions was made using a model fit based on the GIS variables and outlet connection, in which the all of the outlets were presumed to be connected to the ditches without gaps. In this case, the loach were expected to be distributed almost throughout the paddy fields with medium–high probability (40–100%). In another scenario that presumed the complete land consolidation of all the paddy fields, the probability of loach occurrence was low (0–30%) throughout the island with the exception of the island’s center in the Kuninaka region.     

Implications of global change for the maintenance of water quality and ecological integrity in the context of current water laws and environmental policies

There is both a fundamental and applied need to define expectations of changes in aquatic ecosystems due to global changes. It is clear that programs using biological indicators and reference-based comparisons as the foundation for assessments are likely to make increasingly erroneous decisions if the impacts of global change are ignored. Global changes influence all aspects of water resource management decisions based on comparisons to reference conditions with impacts making it increasingly problematic to find an “undisturbed” water body to define acceptable conditions of ecological integrity. Using a more objective scale for characterizing reference conditions that is anchored in expectations for what would be attainable under undisturbed conditions, such as the Biological Condition Gradient (BCG) is one approach that maintains consistent definitions for ecosystem conditions. In addition, protection of reference stations and of unique or undisturbed aquatic resources is imperative, though the scope of protection options is limited. Projections indicate that encroaching land use will affect 36–48% of current reference surface waters by the year 2100. The interpretation of biological indicators is also at risk from global changes. Distinguishing taxonomic attributes based on temperature or hydrologic preferences can be used to enhance the ability to make inferences about global change effects compared to other stressors. Difficulties arise in categorizing unique indicators of global changes, because of similarities in some of the temperature and hydrologic effects resulting from climate change, land use changes, and water removal. In the quest for biological indicators that might be uniquely sensitive to one global stressor as an aid in recognizing probable causes of ecosystem damage, the potential similarities in indicator responses among global and landscape-scale changes needs to be recognized as a limiting factor. Many aspects of global changes are not tractable at the local to regional scales at which water quality regulations are typically managed. Our ability to implement water policies through bioassessment will require a shift in the scale of assessment, planning, and adaptations in order to fulfill our ultimate regulatory goals of preserving good water quality and ecological integrity. Providing clear expectations of effects due to global change for key species and communities in freshwater ecosystems will help water quality programs achieve their goals under changing environmental conditions.     

Galling by Rhopalomyia solidaginis alters Solidago altissima architecture and litter nutrient dynamics in an old-field ecosystem

Plant–insect interactions can alter ecosystem processes, especially if the insects modify plant architecture, quality, or the quantity of leaf litter inputs. In this study, we investigated the interactions between the rosette gall midge Rhopalomyia solidaginis and tall goldenrod, Solidago altissima, to quantify the degree to which the midge alters plant architecture and how the galls affect rates of litter decomposition and nutrient release in an old-field ecosystem. R. solidaginis commonly leads to the formation of a distinct apical rosette gall on S. altissima and approximately 15% of the ramets in a S. altissima patch were galled (range: 3–34%). Aboveground biomass of galled ramets was 60% higher and the leaf area density was four times greater on galled leaf tissue relative to the portions of the plant that were not affected by the gall. Overall decomposition rate constants did not differ between galled and ungalled leaf litter. However, leaf-litter mass loss was lower in galled litter relative to ungalled litter, which was likely driven by modest differences in initial litter chemistry; this effect diminished after 12 weeks of decomposition in the field. The proportion of N remaining was always higher in galled litter than in ungalled litter at each collection date indicating differential release of nitrogen in galled leaf litter. Several studies have shown that plant–insect interactions on woody species can alter ecosystem processes by affecting the quality or quantity of litter inputs. Our results illustrate how plant–insect interactions in an herbaceous species can affect ecosystem processes by altering the quality and quantity of litter inputs. Given that S. altissima dominates fields and that R. solidaginis galls are highly abundant throughout eastern North America, these interactions are likely to be important for both the structure and function of old-field ecosystems.     

Effects of Urbanization-Induced Environmental Changes on Ecosystem Functioning in the Phoenix Metropolitan Region,USA

Abstract Urban ecosystems are profoundly modified by human activities and thereby provide a unique “natural laboratory” to study potential ecosystem responses to anthropogenic environmental changes. Because urban environments are now affected by urban heat islands, carbon dioxide domes, and high-level nitrogen deposition, to some extent they portend the future of the global ecosystem. Urbanization in the metropolitan region of Phoenix, Arizona (USA) has resulted in pronounced changes in air temperature (T _air), atmospheric CO₂ concentration, and nitrogen deposition (N_dep). In this study, we used a process-based ecosystem model to explore how the Larrea tridentata dominated Sonoran Desert ecosystem may respond to these urbanization-induced environmental changes. We found that water availability controls the magnitude and pattern of responses of the desert ecosystem to elevated CO₂, air temperature, N deposition and their combinations. Urbanization effects were much stronger in wet years than normal and dry years. At the ecosystem level, aboveground net primary productivity (ANPP) and soil organic matter (SOM) both increased with increasing CO₂ and N_dep individually and in combinations with changes in T _air. Soil N (N_soil) responded positively to increased N deposition and air temperature, but negatively to elevated CO₂. Correspondingly, ANPP and SOM of the Larrea ecosystem decreased along the urban–suburban–wildland gradient, whereas N_soil peaked in the suburban area. At the plant functional type (FT) level, ANPP generally responded positively to elevated CO₂ and N_dep, but negatively to increased T _air. C₃ winter annuals showed a greater ANPP response to higher CO₂ levels (>420 ppm) than shrubs, which could lead over the long term to changes in species composition, because competition among functional groups is strong for resources such as soil water and nutrients. Overall, the combined effects of the three environmental factors depended on rainfall variability and nonlinear interactions within and between plant functional types and environmental factors. We intend to use these simulation results as working hypotheses to guide our field experiments and observations. Experimental testing of these hypotheses through this process should improve our understanding of urban ecosystems under increasing environmental stresses.     

Stable isotopic structure of aquatic ecosystems

Isotopic, biogeochemical and ecological structure can provide a new dimension for understanding material flows, and the simultaneous function and structure of an ecosystem. Distributions ofδ ¹³C andδ ¹⁵N for biogenic substances in the Nanakita river estuary involving Gamo lagoon in Japan were investigated to construct isotope biogeochemical and ecological structure for assessing fate and transfer of organic matter, and food web structure. The isotopic framework of the ecosystem was successfully described in aδ ¹⁵N–δ ¹³C map. In this estuary the variations of isotope ratios of biogenic substances were clearly explained by the mixing of land-derived organic matter, and marine-derived organic matter. A trophic-level effect of¹⁵N enrichment was clearly observed. Organisms were classified into three groups depending upon the contribution of land-derived organic matter in a food chain. Almost all biota except mollusca in the lagoon depend on organic matter of marine origin. The contributions of both land and marine organic matter were comparable for mollusca in the lagoon.     

基于土壤线虫群落成熟度指数的拉沙山土壤生态系统稳定性评价及可行性研究

土壤生态系统被誉为是生物圈的能量储存介质,稳定健康的土壤生态系统是维持陆地生态系统生产力的关键,但系统内部各种生物作用和复杂过程很难直接观测,很难利用陆地生态系统的评价体系评价其稳定性。近年来土壤线虫群落成熟度指数作为土壤生态系统稳定性的指示类群被广泛认可和利用,拟通过拉沙山区域13个固定大样地中的52个样方的土壤线虫成熟度指数对区域土壤生态系统稳定性进行评价,并对评价的可行性进行验证。采用宏基因技术共获取线虫扩增子序列变体(Amplicon Sequence Variant, ASV)963个,隶属于2纲10目41科67属,群落结构以食细菌线虫和捕食-杂食类线虫为主,群落以K-策略者(c-p 3-5)生活类群为主导。研究结果表明,土壤线虫的成熟度指数均值为3.24±0.32,评价结果认为拉沙山区域土壤生态系统整体较为稳定,且土壤线虫成熟度指数在空间上不存在统计差异(P>0.05)。通过利用样地监测获得的人为干扰强度与利用土壤线虫成熟度指数所评价出的结果呈现显著的负相关关系(P<0.05),表明稳定性较低的样地其人类活动干扰也较大;同时对土壤线虫成熟度指数的评价结果与样地地表生态系统现状验证结果显示,在中海拔的区域主要因其河谷较深,同时两侧山体陡峭且时有塌方发生导致土壤生态系统的不稳定且土壤线虫成熟度指数偏低,评价结果与实际地表生境状态相符,所以利用土壤线虫成熟度指数评价区域大样地是可行的,该研究为未来区域的土壤生态系统健康评价完善提供了新的指标。     

Patterning limnological characteristics of the Chilika lagoon (India) using a self-organizing map

In this study, a self-organizing map (SOM) was utilized to classify habitats in the Chilika lagoon located in India, the largest lagoon ecosystem in Asia (maximum length, 64.3 km; mean width, 20.1 km). The lagoon was marginally eutrophic (nitrate, 0.25 ± 0.22 mg L⁻¹; orthophosphate, 0.26 ± 0.22 mg L⁻¹; n = 1,980, respectively) for six years (1999–2004), and it used to be warm, shallow, turbid and predominantly brackish. The SOM model successfully identified the changing patterns of limnology in the lagoon using the monthly limnological dataset from 30 study sites (July 1999–December 2004). Comparative re-sectoring evaluation of current monitoring sites was accomplished based on the outcome of the modeling. The new site clustering that emerged from the model was similar to conventional ones, and several sites were reorganized. Water physicochemistry was affected by freshwater inflow during monsoon and the new lagoon mouth constructed in September 2000, which resulted in variations in site characteristics in terms of limnology. The results of this study may provide information on the limnological patterns in Chilika lagoon, and they leave room for further study into functional changes in the lagoon ecology with respect to changes in climatic factor, freshwater flow and lagoon morphology.     

Distribution of ten antibiotic resistance genes in <Emphasis Type="Italic">E. coli</Emphasis> isolates from swine manure,lagoon effluent and soil collected from a lagoon waste application field

The prevalence of ten antibiotic resistance genes (ARGs) was evaluated in a total of 616 Escherichia coli isolates from swine manure, swine lagoon effluent, and from soils that received lagoon effluent on a commercial swine farm site in Sampson County, North Carolina (USA). Isolates with ARGs coding for streptomycin/spectinomycin (aadA/strA and strB), tetracycline (tetA and tetB), and sulfonamide (sul1) occurred most frequently (60.6–91.3%). The occurrence of E. coli isolates that carried aadA, tetA, tetB, and tetC genes was significantly more frequent in soil samples (34.0–97.2%) than in isolates from lagoon samples (20.9–90.6%). Furthermore, the frequency of isolates that contain genes coding for aadA and tetB was significantly greater in soil samples (82.6–97.2%) when compared to swine manure (16.8–86.1%). Isolates from the lagoon that carried tetA, tetC, and sul3 genes were significantly more prevalent during spring (63.3–96.7%) than during winter (13.1–67.8%). The prevalence of isolates from the lagoon that possessed the strA, strB, and sul1 resistance genes was significantly more frequent during the summer (90.0–100%) than during spring (66.6–80.0%). The data suggest that conditions in the lagoon, soil, and manure may have an impact on the occurrence of E. coli isolates with specific ARGs. Seasonal variables seem to impact the recovery isolates with ARGs; however, ARG distribution may be associated with mobile genetic elements or a reflection of the initial numbers of resistant isolates shed by the animals.     

Invasion of <Emphasis Type="Italic">Spartina alterniflora</Emphasis> Enhanced Ecosystem Carbon and Nitrogen Stocks in the Yangtze Estuary,China

Whether plant invasion increases ecosystem carbon (C) stocks is controversial largely due to the lack of knowledge about differences in ecophysiological properties between invasive and native species. We conducted a field experiment in which we measured ecophysiological properties to explore the response of the ecosystem C stocks to the invasion of Spartina alterniflora (Spartina) in wetlands dominated by native Scirpus mariqueter (Scirpus) and Phragmites australis (Phragmites) in the Yangtze Estuary, China. We measured growing season length, leaf area index (LAI), net photosynthetic rate (Pn), root biomass, net primary production (NPP), litter quality and litter decomposition, plant and soil C and nitrogen (N) stocks in ecosystems dominated by the three species. Our results showed that Spartina had a longer growing season, higher LAI, higher Pn, and greater root biomass than Scirpus and Phragmites. Net primary production (NPP) was 2.16 kg C m⁻² y⁻¹ in Spartina ecosystems, which was, on average, 1.44 and 0.47 kg C m⁻² y⁻¹ greater than that in Scirpus and Phragmites ecosystems, respectively. The litter decomposition rate, particularly the belowground decomposition rate, was lower for Spartina than Scirpus and Phragmites due to the lower litter quality of Spartina. The ecosystem C stock (20.94 kg m⁻²) for Spartina was greater than that for Scirpus (17.07 kg m⁻²), Phragmites (19.51 kg m⁻²) and the mudflats (15.12 kg m⁻²). Additionally, Spartina ecosystems had a significantly greater N stock (698.8 g m⁻²) than Scirpus (597.1 g m⁻²), Phragmites ecosystems (578.2 g m⁻²) and the mudflats (375.1 g m⁻²). Our results suggest that Spartina invasion altered ecophysiological processes, resulted in changes in NPP and litter decomposition, and ultimately led to enhanced ecosystem C and N stocks in the invaded ecosystems in comparison to the ecosystems with native species.     

Influence of environmental parameters on growth pattern and population structure of Carassius auratus gibelio in Eastern Ukraine

Population structure and growth parameters of Prussian carp (Carassius auratus gibelio) were studied in 12 freshwater ecosystems of the Donbass region (Eastern Ukraine). These ecosystems differed significantly with respect to their surface area, water transparency and annual concentrations of phosphorus and nitrogen. Amongst the studied ecosystems, diploid males and females as well as a smaller percentage of triploid females were found. The population structure of C. a. gibelio varied significantly in terms of the percentage of triploids and sex ratio amongst diploids. A considerable proportion of triploid females (>10%) was found in four ecosystems with intermediate surface area (38–50 ha) and relatively high growth rate of specimens. The sex ratio amongst diploids was significantly female-biased in seven of 12 ecosystems, including those where triploids were present in considerable numbers. The growth parameters of Prussian carp were significantly correlated with ecosystem characteristics, but the growth patterns of diploids and triploids were not significantly different from each other. The restricted distribution of triploid specimens suggests that the triploid form might counter diverse environmental challenges, whereas the diploid form of Prussian carp seems to be efficiently adapted to a wide range of ecosystem conditions.     

Water and Values: Ecological Research as the Basis for Water Management and Nature Management

Over the past 50 years ecology has developed into a mature branch of the natural sciences, comprising firm concepts (e.g. for rivers River Continuum Concept and Flood Pulse Concept) and extensive empirical surveys (sophisticated lab and field experiments, simulation models, GIS). Estuaries and rivers are continuously threatened ecosystems, considering the massive expansion of man’s economic activities. I focus on rivers and estuaries in the Netherlands (W. Europe), where recent public interest has mainly been determined by two flooding disasters (mega-disaster in 1953; near-disaster in 1995). The measures taken to enhance the safety of the human population were adequate: building of large closure dams, and storm surge barriers in the estuaries, and heightening of levees along the rivers. Eventually these measures were detrimental for what was left of the dynamic river ecosystems from the past. This paper focuses on two ecosystem studies. (1) An ecosystem study in Grevelingen lagoon, a large embanked estuary that changed into a brackish water lagoon. Predictive ecological models (e.g. for the wax and wane of Eelgrass, Zostera marina) were inadequate because of the exceptional characteristics of the lagoon: the ecosystem appeared to be instable, and not resilient. (2) An ecosystem study at Afferdensche and Deestsche Waarden, a floodplain area along the river Waal, strongly affected by toxicants deposited before 1980. We studied the functioning and eco-toxicology of floodplain food webs, deteriorated by pollutants. Fine-tuned spatial components were introduced in ecological risk assessment models of several trophic levels (e.g. a top predator, the Little Owl, Athena noctua). Safety for the human population, living below sea level, and below the level of the main rivers, must be improved, but overhasty technocratic measures deteriorating the remaining semi-natural, highly appreciated landscapes, should be avoided. Stakeholder interests must be adapted to sustainable ecological river management, and not the other way round, as has been done for the past ten centuries.     

Spatio-temporal variations of the zooplankton abundance and composition in a West African tropical coastal lagoon (Grand-Lahou,Côte d’Ivoire)

Zooplankton constitutes a sensitive tool for monitoring environmental changes in coastal lagoons; however, the available information on zooplankton communities is not sufficient to optimize their rational management. The relationships between zooplankton distribution and environmental factors were studied in a tropical lagoon to test whether the indicator properties of zooplankton assemblages could be used to monitor water quality, in a context of expected eutrophication provoked by an increasing anthropogenic activity. Twenty-one (21) stations were sampled monthly from January to December 2004. The community was composed of 65 taxa including Copepoda, Rotifera, and Cladocera. Copepoda was the most abundant group (81% of total numbers). The main zooplankton species were Oithona brevicornis, Acartia clausi, and Brachionus plicatilis. The highest zooplankton abundance (171–175 ind. l⁻¹) was recorded during the long, dry season (February–April) and the lowest (40–45 ind. l⁻¹) during the rainy and the flood periods (June–July). At a spatial level, the lowest abundance was observed in the estuarine zone. During the dry seasons (December–April and August–September), marine zooplankton taxa were abundant near the channel of Grand-Lahou, and brackish water taxa dominated in the other sites. Multivariate analyses (Co-inertia) showed that the composition of zooplanktonic communities and their spatio-temporal variations were mainly controlled by salinity variations closely linked to the climatic and hydrological context. The role of the trophic state on zooplankton communities could not be clearly evidenced. Our results and a comparison with previous studies in the neighboring, highly polluted Ebrié Lagoon suggest that the ratio between Oithona and Acartia abundance could be used as biological indicator for the water quality. Handling editor: S. I. Dodson