Detritus Food Chain Research Articles

基于生态通道模型的长江口水域生态系统结构与能量流动分析

PDF HTML阅读 XML下载 导出引用 引用提醒 基于生态通道模型的长江口水域生态系统结构与能量流动分析 DOI: 10.5846/stxb201501150129 作者: 作者单位: 中国科学院生态环境研究中心,南京水利科学研究院,中国水产科学研究院东海水产研究所,南京水利科学研究院,三峡大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（51425902，51409242）；国家重点基础研究发展计划973项目（2010CB429000） Analysis of the ecosystem structure and energy flow of the Yangtze River estuary and adjacent seas, based on the Ecopath model Author: Affiliation: RCEES,NHRI,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用Ecopath with Ecosim在前期研究的基础上构建了3个时期（2000年秋、2006年秋、2012年秋）长江口水域生态系统的生态通道模型，分析对比了三峡工程蓄水前中后期，长江口水域生态系统结构与能量流动特征。模型将长江口水域生态系统划分为鱼类、虾类、蟹类、头足类、底栖动物、浮游动物、浮游植物、碎屑等17个功能组，基本覆盖了长江口生态系统能量流动的主要途径。模型结果分析表明：蓄水前中后期，长江口水域生态系统各功能组营养级组成和分布相近，但由于长江口渔业过度捕捞，蓄水中后期多数功能组的生态营养转换率被动提高。长江口渔获物的组成未发生明显变化，但渔获物的平均营养级降低，渔获量减少。蓄水中后期，生态系统中牧食食物链的重要性增加，碎屑食物链的重要性降低，这与蓄水之后长江入海径流改变、泥沙量减少、陆源污染增加关系密切。结果表明，蓄水前中后期，生态系统均处于不成熟阶段，蓄水后生态系统总生物量、初级生产量及流向碎屑的能量呈降低趋势，但系统的净效率和再循环率升高。 Abstract:The cumulative impacts of water conservancy projects in the Yangtze River basin, especially the Three Gorges Reservoir, have had a significant effect on the biological and ecological integrity of the Yangtze River estuarine ecosystem. This research establishes three ecopath models of the Yangtze River estuary and adjacent seas before (the autumn of 2000), during (the autumn of 2006), and after (the autumn of 2012) the impoundments of the Three Gorges Reservoir, using Ecopath and Ecosim software to characterize and compare the estuarine ecosystem's food web structure and energy flow. Sensitivity analyses were carried out to evaluate the uncertainty levels of the models. The three models consisted of 17 functional groups covering the main paths of the ecosystem food web, including piscivorous fishes, generalist predators, shrimp predators, zooplanktivores, crab predators, other pelagic fishes, other demersal fishes, other benthic fishes, shrimp, crabs, jellyfish, cephalopods, macrobenthos, meiobenthos, zooplankton, phytoplankton, and detritus. The simulated results showed that the values of trophic levels (TL) ranged from 1.000 to 3.802 in 2000 (before the impoundments), from 1.000 to 4.058 in 2006 (during the impoundments), and from 1.000 to 4.019 in 2012 (after the impoundments). This indicates that the TLs distributions of the functional groups were similar under all three conditions. However, the ecotrophic efficiencies of commercial species, such as Pseudosciaena polyactis, were elevated because of the increased fishing intensity in the Yangtze River estuary. The structure of catches did not change noticeably during this period, but the mean trophic level of the catch decreased from 3.406 to 3.369, as did the number of catches (from 1.026 t km-2 a-1 to 0.719 t km-2 a-1). Meanwhile, after the impoundments the role of the detritus food chain became less important to the energy transfer process than that of the grazing food chain, and over 90% of the energy flows were assembled in TL I and II, most of which flow into detritus and could be a source of internal pollution. The total transfer efficiency of the Yangtze River estuary ecosystem was 10.2% in 2000, 10.0% in 2006 and 9.4% in 2012. All of these negative effects are likely to be closely related to reductions in freshwater and sediment discharges, as well as the increase of land-based pollution in the Yangtze River Basin. Furthermore, the result also showed that the parameters of total biomass, total primary production, and the sum of all flows into detritus gradually decreased; however, the gross efficiency, Finn cycling index, Finn's mean path length, and system omnivory index increased. The ecosystems (before, during, and after impoundments) were found to remain in the immature stage. 参考文献 相似文献 引证文献

Bioaccumulation of dioxin-like PCBs and PBDEs by detritus-feeding fish in the Rio de la Plata estuary, Argentina.

A comparative analysis of bioaccumulation behavior of dioxin-like polychlorinated biphenyls (dlPCBs) and polybrominated biphenyl ethers (PBDEs) was conducted involving simultaneous measurements in settling particles and a detritivorous fish (Sabalo, Prochilodus linneatus) collected in the sewage impacted Buenos Aires coastal area. Focalization of dlPCBs and PBDEs along the detritus food chain is reflected by a 30-40-fold increase of dry weight PBDE and dlPCB concentrations from settling particles to fish (1.8 ± 1.0 to 58 ± 31 and 6.8 ± 3.9 to 281 ± 155 ng g(-1) dry weight (dw), respectively). In this transference, dlPCB congeners presented more conservative patterns than those of PBDEs, basically due to debromination of BDE 99 and 153 to BDE 47 in fish. Lipid/organic carbon-based biota-sediment accumulation factors (BSAFs) ranged between 5 and 20 (7.3 ± 3.0 and 16 ± 8.0 for PBDEs and dlPCBs). Congener-specific BSAF of dlPCBs suggested a lower bioavailability of more planar non-ortho-PCB versus mono-ortho-PCB suggesting higher affinity to organic matter. BSAFs of PBDEs differed markedly among bromine homolog groups, supporting the biotransformation-formation from higher brominated to lighter congeners. The log BSAFs-log K OW relationship of dlPCBs and PBDEs presented a parabolic pattern maximizing at log K OW 6-7, but PBDE curve differs reflecting biotransformation processes.

Net ecosystem carbon balance of an apple orchard

Fruit tree ecosystems represent an important land use type in Southern Europe. Nevertheless, limited information and large uncertainty currently exist about their potential role as a sink of atmospheric CO2, which is measured through an index that accounts for all inputs and outputs of C, namely the net ecosystem carbon balance (NECB). In this paper, we studied the fluxes of C assimilation, the C release and the lateral C and their contribution to the NECB in an apple orchard at different time scales. Data of net ecosystem productivity (NEP) were recorded by eddy covariance and converted into ecosystem respiration and gross primary productivity (GPP). The net primary productivity (NPP) and the C partitioning among tree organs were also biometrically assessed. The study was carried out in the period 2009–2012 in a commercial apple orchard located in an intensive fruit production district of South Tyrol, Italy. We found a positive NEP from March to October and yearly NEP values of 403gCm−2. GPP (1346gCm−2year−1 on average) was highest between May and September, when leaves intercepted the highest amount of PPFD. Tree growth accounted for more than 90% of the total new biomass produced in the orchard, the remaining part being represented by the herbaceous vegetation covering the orchard floor. Trees allocated to fruits approximately half of the yearly NPP, while they increased only to a limited extent their standing biomass. A significant fraction of NPP was also allocated to organs (leaves, pruned woody organs, etc.,) that feed the detritus cycle. The NECB was on average positive (69gCm−2) but showed high variation among years, and in the year when fruit yields was very high (74t fruits/ha), the NECB was even negative. NECB was accounted to a greater extent by the yearly increase of tree woody organs and to a minor extent by the C transfer to the soil from the decomposing litter. The most relevant agronomical suggestion of this study is that tree vegetative growth resulting into either increasing standing biomass and/or increasing tree litter should not be reduced if we aim at maintaining the CO2 sink capacity of the apple orchard.

Contrasting patterns of allochthony among three major groups of crustacean zooplankton in boreal and temperate lakes.

The importance of terrestrial-derived organic matter for lake zooplankton communities remains debated, partly because little is known about the basic pathways by which allochthonous carbon is transferred to zooplankton, and whether these vary among the major taxonomic and functional groups. We quantified allochthony of three zooplankton groups (Cladocera, Calanoida, and Cyclopoida) across 18 lakes in Quebec, spanning broad gradients of dissolved organic matter (DOM) and lake trophy, using a multi-isotope (delta2H + delta13C), multi-source (terrestrial, phytoplanktonic, benthic) approach. All three zooplankton groups had significant levels of allochthony, but differed greatly in their respective patterns across lakes. Allochthony in Calanoida and Cyclopoida was linked to detrital food chains based on particulate organic matter (POM) and on DOM, respectively, whereas in Cladocera it appeared related to both pathways; not surprisingly this latter group had the highest mean allochthony (0.31; compared to 0.18 in Cyclopoida and 0.16 in Calanoida). This study highlights the complexity of the pathways of delivery and transfer of terrestrial organic matter in freshwaters, and underscores the role that microbial food webs play in this transfer.

Biological proliferation of cesium-137 through the detrital food chain in a forest ecosystem in Japan

Radionuclides, including 137Cs, were released from the disabled Fukushima Daiichi Nuclear Power Plant and had been deposited broadly over forested areas of north-eastern Honshu Island, Japan. In the forest, 137Cs was highly concentrated on leaf litters deposited in autumn 2010, before the accident. Monitoring of the distribution of 137Cs among functional groups clearly showed the role of the detrital food chain as the primary channel of 137Cs transfer to consumer organisms. Although many studies have reported the bioaccumulation (or dilution) of radioactive materials through trophic interactions, the present results highlight the importance of examining multiple possible pathways (e.g., grazing vs. detrital chains) in the proliferation of 137Cs through food webs. These results provide important insight into the future distribution and transfer of 137Cs within forest ecosystems.

Net primary productivity, allocation pattern and carbon use efficiency in an apple orchard assessed by integrating eddy covariance, biometric and continuous soil chamber measurements

Abstract. Carbon use efficiency (CUE), the ratio of net primary production (NPP) over gross primary production (GPP), is a functional parameter that could possibly link the current increasingly accurate global GPP estimates with those of net ecosystem exchange, for which global predictors are still unavailable. Nevertheless, CUE estimates are actually available for only a few ecosystem types, while information regarding agro-ecosystems is scarce, in spite of the simplified spatial structure of these ecosystems that facilitates studies on allocation patterns and temporal growth dynamics. We combined three largely deployed methods, eddy covariance, soil respiration and biometric measurements, to assess monthly values of CUE, NPP and allocation patterns in different plant organs in an apple orchard during a complete year (2010). We applied a measurement protocol optimized for quantifying monthly values of carbon fluxes in this ecosystem type, which allows for a cross check between estimates obtained from different methods. We also attributed NPP components to standing biomass increments, detritus cycle feeding and lateral exports. We found that in the apple orchard, both net ecosystem production and gross primary production on a yearly basis, 380 ± 30 g C m−2 and 1263 ± 189 g C m−2 respectively, were of a magnitude comparable to those of natural forests growing in similar climate conditions. The largest differences with respect to forests are in the allocation pattern and in the fate of produced biomass. The carbon sequestered from the atmosphere was largely allocated to production of fruit: 49% of annual NPP was taken away from the ecosystem through apple production. Organic material (leaves, fine root litter, pruned wood and early fruit falls) contributing to the detritus cycle was 46% of the NPP. Only 5% was attributable to standing biomass increment, while this NPP component is generally the largest in forests. The CUE, with an annual average of 0.71 ± 0.12, was higher than the previously suggested constant values of 0.47–0.50. Low nitrogen investment in fruit, the limited root apparatus, and the optimal growth temperature and nutritional condition observed at the site are suggested to be explanatory variables for the high CUE observed.

Diets of fan shells (Pinna nobilis) of different sizes: fatty acid profiling of digestive gland and adductor muscle

Pinna nobilis is a large bivalve, endemic to the Mediterranean Sea that was shown in a previous study to ingest significantly different proportions of different food items according to its shell height. Fatty acid profiling of total lipids was used to examine these differences in diet in relation to shell size. Small (shell height 23.0 ± 3.3 cm), medium (SH 41.5 ± 5.5 cm) and large (SH 62.7 ± 4.8 cm) P. nobilis were collected from Mali Ston Bay, Adriatic Sea, in March 2010, and fatty acid analysis was performed on digestive gland and adductor muscle tissues. Based on the analysis of the digestive gland, small P. nobilis were associated with a detrital food chain, characterized by saturated and branched-chain fatty acids, while the diets of medium and large individuals had a greater proportion of polyunsaturated fatty acids. This likely reflects the fact that smaller individuals feed within the benthic boundary layer where the detritus concentrations are high. Fatty acid incorporation into the adductor muscle, likely representative of food taken up over a longer time period, was reversed, that is, larger individuals had lower levels of polyunsaturated fatty acids. This most probably reflects energy expenditure, which typically increases with increasing organism size.

Impact of Tributyltin on Immune Response and Life History Traits of Chironomus riparius: Single and Multigeneration Effects and Recovery from Pollution

Chironomids play an important role in the detritus cycle and as a component in brackish- and freshwater benthic and terrestrial food webs. If TBT is present in their environment, then they may accumulate tributyltin (TBT) during their juvenile period, which negatively affects many of their life history characteristics. The aim of this experiment is to test the effects of three TBT sediment concentrations (nominal 30, 90, and 180 μg/kg) on life history traits (development time, survival, fecundity, and weight) and immune response (number of hemocytes and phenoloxidase activity) of the nonbiting midge, Chironomus riparius. These responses were recorded immediately after one generation of TBT exposure, and in the long run during five consecutive generations. We also assessed recovery from pollution after four generations of TBT exposure. In a single generation, TBT affected all measured parameters, except phenoloxidase activity, when compared to the control. Long-term-effects of TBT lead to extinction of all treatments after the fifth generation. Again, all measured variables significantly differ from the control, although TBT had varying effects on the measured variables. Most of the effects of TBT on population viability were not evident during recovery, once TBT was removed from the sediment. The effect of previous TBT contamination was observed only in delayed larval development, suggesting that TBT has only limited maternal/epigenetic effects on individual condition. However, altered schedules in the life-cycle can have unexpected ecological impacts. TBT decreases the viability of Chironomus riparius and the effect will become stronger if exposure to TBT continues for many generations. Yet, the harmful effect of TBT disappears quickly as the TBT is removed from the environment.

Sediment organic tin contamination promotes impoverishment of non-biting midge species communities in the Archipelago Sea, S-W Finland

Chironomid species are a vital component in many benthic and terrestrial food webs; they have an important role in the detritus cycle, and are an important source of food for many species. We studied how tributyltin (TBT) in brackish water sediments affect the composition of chironomid species communities. Emergence traps were used at selected sites on a TBT gradient in the Archipelago Sea, S-W Finland. Increased sediment TBT concentration was associated with significant chironomid species turnover, which in turn was related to decreased species diversity (number of species and genera). However, the overall number of individuals did not decrease markedly with increasing TBT contamination. This suggests that the ecological role of chironomids in the food web may be preserved even under severe impoverishment of the chironomid community due to organic tin contamination. The increased prevalence of more TBT tolerant species can potentially lead to a transport of organic tin compounds between aquatic and terrestrial food webs. Furthermore, the reduced diversity of an ecologically influential group might lower the resistance of the entire food web to other environmental hazards and perturbations.

Stratified distribution of nutrients and extremophile biota within freshwater ice covering the surface of Lake Baikal

Biological entities and gradients of selected chemicals within the seemingly barren ice layers covering Lake Baikal were investigated. Ice cores 40-68 cm long were obtained from in shore and offshore sites of Southern Lake Baikal during the cold period of a year (March-April) in 2007 and 2008. In microscopic observations of the melted ice, both algae and bacteria were found in considerable numbers (>10(3) cells/L and >10(4) cells/ml, respectively). Among all organisms found, diatom was generally the most predominant taxon in the ice. Interestingly, both planktonic and benthic algae were present in considerable numbers (2-4×10(4) cells/L). Dominant phototrophic picoplankton were comprised of small green algae of various taxa and cyanobacteria of Synechococcus and Cyanobium. The bacterial community consisted mostly of short rod and cocci cells, either free-living or aggregated. Large numbers of yeast-like cells and actinomycete mycelium were also observed. Concentrations of silica, phosphorus, and nitrate were low by an order of magnitude where biota was abundant. The profile of the ice could be interpreted as vertical stratification of nutrients and biomass due to biological activities. Therefore, the organisms in the ice were regarded to maintain high activity while thriving under freezing conditions. Based on the results, it was concluded that the freshwater ice covering the surface of Lake Baikal is considerably populated by extremophilic microorganisms that actively metabolize and form a detritus food chain in the unique large freshwater ecosystem of Lake Baikal.

Modelling the impact of mangroves on fish population dynamics of Hooghly - Matla estuarine system, West Bengal, India

Breakdown of mangrove litter, adjacent to Hooghly-Matla estuarine ecosystem, plays a major role in regulating the fish population of the estuary. For last several decades, there has been a gradual decline in fish population due to over exploitation of resource but the exact cause of this decrease in production is still not known. To know this cause, an eleven compartment holistic model of nutrient source to estuary and grazing food chain is constructed. Model results depict the role of mangroves in regulating fish population dynamics of the estuary and predation rate of carnivorous fish on detritivorous fish is sensitive parameter in maintaining the balance between grazing food chain and detritus food chain.

Mangrove litter fall: Extrapolation from traps to a large tropical macrotidal harbour

Mangrove litter is a major source of organic matter for detrital food chains in many tropical coastal ecosystems, but scant attention has been paid to the substantial challenges in sampling and extrapolation of rates of litter fall. The challenges arise due to within-stand heterogeneity including incomplete canopy cover, and canopy that is below the high tide mark. We sampled litter monthly for three years at 35 sites across eight mapped communities in the macrotidal Darwin Harbour, northern Australia. Totals were adjusted for mean community canopy cover and the occurrence of canopy below the high tide mark. The mangroves of Darwin Harbour generate an estimated average of 5.0 t ha −1 yr −1 of litter. This amount would have been overestimated by 32% had we not corrected for limited canopy cover and underestimated by 11% had we not corrected for foliage that is below the high tide mark. Had we made neither correction, we would have overestimated litter fall by 17%. Among communities, rates varied 2.6-fold per unit area of canopy, and 3.9-fold among unit area of community. Seaward fringe mangroves were the most productive per unit of canopy area but the canopy was relatively open; Tidal creek forest was the most productive per unit area of community. Litter fall varied 1.1-fold among years and 2.0-fold among months though communities exhibited a range of seasonalities. Our study may be the most extensively stratified and sampled evaluation of mangrove litter fall in a tropical estuary. We believe our study is also the first such assessment to explicitly deal with canopy discontinuities and demonstrates that failure to do so can result in considerable overestimation of mangrove productivity.

Fingerprints of lagoonal life: Migration of the marine flatfish Solea solea assessed by stable isotopes and otolith microchemistry

The commercially important marine flatfish common sole (Solea solea) facultatively uses NW Mediterranean lagoons as nurseries. To assess the imprint left by the lagoonal passage, muscle carbon (C) and nitrogen (N) isotope values of S. solea juveniles caught in Mauguio lagoon in spring (shortly after arrival from the sea) and in autumn (before the return to the sea) were compared with values of juveniles from adjacent coastal marine nurseries. In addition, in the lagoon, sole otolith stable isotope (C and oxygen (O)) and elemental (11 elements) composition in spring and autumn, and the stable isotope composition (C and N) of organic matter sources in autumn, were determined. Overall, our data indicate that a distinct lagoonal signature existed. Specifically, lagoon soles showed a strong enrichment in muscle tissue 15N (>6‰) compared to their coastal relatives, likely linked to sewage inputs (see below), and a depletion in 13C (1–2‰), indicative of higher importance of 13C depleted terrestrial POM in the lagoon compared to coastal nurseries. In addition, over the time spent in the lagoon, sole otolith δ13C and δ18O values and otolith elemental composition changed significantly. Analysis of the lagoon sole foodweb based on C and N isotopes placed sediment particulate organic matter (POM) at the base. Seagrasses, formerly common but in decline in Mauguio lagoon, played a minor role in the detritus cycle. The very strong 15N enrichment of the entire foodweb (+7 to +11‰) compared to little impacted lagoons and coastal areas testified of important human sewage inputs. Regarding the S. solea migration, the analysis of higher turnover and fast growth muscle tissue and metabolically inert and slower growth otoliths indicated that soles arrived at least several weeks prior to capture in spring, and that no migrations took place in summer. In the autumn, the high muscle δ15N value acquired in Mauguio lagoon would be a good marker of recent return to the sea, whereas altered otolith δ18O values and elemental ratios hold promise as long-term markers. The combination of several complementary tracers from muscle and otoliths may present the chance to distinguish between fish from specific lagoons and coastal nurseries in the future.

Summertime tidal flushing of Barataria Bay: Transports of water and suspended sediments

the edges of the inlet. The net flux of total suspended sediment out of the bay was determined to be 8800 t of which 20% was organic matter, demonstrating a significant source of organic matter to the base of the coastal ocean detrital food chain. The time evolution and net fluxes of water, and suspended sediments showed that the net flow resembles conventional estuarine circulation patterns with net outward flow on the surface and shallow ends of the inlet and with net inward flow in the center and at the bottom of the center of the inlet. The west side has a much larger outward flow than the east side while the east side is fresher. These differences suggest that the Louisiana Coastal Current from around the Bird’s Foot Delta derived from the mixing of shelf water with the Mississippi River freshwater may have entered the bay. This must have been mostly from the east side during the survey, which resulted in a smaller outward flow on the eastern side. A numerical experiment further confirmed this assumption and the model was verified by field observations on 5 May 2010.

Which prey sustains cold-adapted invertebrate generalist predators in arable land? Examining prey choices by molecular gut-content analysis

Summary 1. Generalist predators such as carabid and cantharid beetles form an important component within natural enemy communities in arable land. Usually, predator–prey interactions are examined during the vegetation period, largely ignoring food web interactions occurring in the cold season. This is, however, when the larval stages of many polyphagous beetles develop whose survival critically depends on the availability of suitable prey. 2. In this study, we examined intra- and extraguild feeding links in larval Cantharis spp. (Coleoptera: Cantharidae) and Nebria brevicollis (Coleoptera: Carabidae), both abundant cold-adapted invertebrate predators in European arable land. As these immature beetles are fluid feeders, which impedes a microscopic analysis of their gut content, multiplex polymerase chain reaction assays were developed to examine trophic linkages in the field. 3. Collembolan DNA was detected in 49% and 54% of cantharid and carabid larvae, respectively. Earthworms were consumed by 34% of cantharid and 24% of carabid larvae. Significant differences in lumbricid and collembolan prey detection rates occurred between sampling dates in Cantharis spp. and N. brevicollis larvae, respectively, suggesting that these predators utilized different feeding strategies. In both predator taxa, however, only few individuals (0·2–1%) tested positive for DNA of intraguild prey, indicating that predator–predator trophic interactions were scarce in this community. 4. Synthesis and applications. We present conclusive evidence that cold-adapted predatory beetle larvae are strongly linked to the detrital food chain by feeding on collembolans and earthworms. By improving the habitat conditions for detritivores in arable land by mulching, compost applications, or provision of plant cover during winter, their densities can be increased easily. Applying these measures year round will retain and sustain predatory beetles during their whole life cycle in arable land. Ultimately, we expect that these measures will enhance the ability of polyphagous beetle predators to provide their fundamental ecosystem service as regulators of agricultural pests.

Characteristics of the Fatty Acid Composition of a Deep‐Sea Vent Gastropod, Ifremeria nautilei

Neutral and polar lipids in the soft parts of a gastropod species, Ifremeria nautilei, collected from deep-sea hydrothermal vents, were examined to assess the trophic relationships in hydrothermal vents. The vent gastropod obtains many of its lipids from symbiotic chemosynthetic microorganisms. The major polyunsaturated fatty acids (PUFA) both in the triacylglycerols and phospholipids of the gastropod consist of a limited number of n-3 and n-6 PUFA: arachidonic acid (20:4n-6), icosapentaenoic acid (20:5n-3), and docosapentaenoic acid (22:5n-3), without docosahexaenoic acid (DHA, 22:6n-3). Noticeable levels of various n-6 PUFA, such as 18:2n-6,9, 20:2n-6,9, 20:3n-6,9,12, and 20:3n-6,9,15 with significant levels of 16:1n-6 and 18:1n-6 indicate the biosynthetic characteristic of the endosymbionts. The lack of DHA in all specimens suggests a limitation of its lipid biosynthesis ability with its symbionts. This finding with regard to the lipids is unusual for a marine animal in the grazing or detrital food chain because many marine animal lipids evidently contain high levels of DHA with low levels of n-6 fatty acids. Such contradictory findings lead to some new insights into the absence of a biosynthetic pathway for DHA in I. nautilei, and provide evidence that DHA in this species is dispensable. Similar to herbivorous gastropods, the lack of DHA with significant levels of n-6 PUFA in this species also indicates its selective assimilation of specific microorganisms, such as chemosynthetic bacteria in hydrothermal vents, because significant levels of DHA were found in carnivorous mollusk lipids.

Trophic position of bottom-feeding fish in the Upper Paraná River floodplain

The delta15N composition of bottom-feeding fish (iliophagous = Apareiodon affinis, Cyphocharax nagelii, Prochilodus lineatus, Steindachnerina brevipinna and S. insculpta; detritivorous = Loricariichthys platymetopon and Liposarcus anisitsi; benthophagous = Satanoperca pappaterra and Hoplosternum littorale) and their primary food sources were investigated in the upper Paraná River floodplain during rainy seasons in different environments (lotic and lentic). Two hypotheses were tested: i) that the trophic position and isotopic values of the investigated organisms (fish and food resources) vary spatially; and ii) that trophic position and isotopic compositions differ among iliophagous, detritivorous and benthophagous fish. C4 macrophytes, periphyton and phytoplankton were isotopically different in sites analyzed. Significant isotopic differences occurred in the species of each trophic category. Spatial differences were observed in the isotopic composition of P. lineatus and L. platymetopon, whose values were more enriched in the Paraná River and Pau Véio Lake. Significant spatial differences in trophic position were observed for L. platymetopon and H. littorale, which presented the highest values in the Paraná and Baía rivers, respectively. Trophic positions were significantly different among the species that composed each trophic category. These findings demonstrate that in energy-flow studies in detrital food chains generalizations concerning the grouping of fish into trophic categories and/or habitats should only be carried out after careful investigations of the local/specific trophic dynamics of the organisms.

Biochemical composition of a dominant detritivorous fish Prochilodus lineatus along pollution gradients in the Paraná‐Río de la Plata Basin

The biochemical composition of muscle, liver and stomach contents of a detritivorous fish Prochilodus lineatus was analysed and compared to settling particles and sediments along pollution gradients over 1500 km of the Río de la Plata Basin to evaluate the effects of anthropogenic discharges in a detritus food chain. The stomach contents of P. lineatus collected in the polluted Metropolitan Buenos Aires coast were enriched in proteins, carbohydrates and lipids, similar to settling particulates collected in the sewer area, and two to five times higher than underlying sediments, supporting the interpretation that P. lineatus feeds on unconsolidated organic flocs freshly decanted from mixed industrial and sewage outfalls. Fish from Buenos Aires had consistently higher standard length (L(S)) and mass (M(T)) slopes (b = 3.5), condition indexes (K = 3.01 +/- 0.47, mean +/-s.d.) and muscle fat content (fat = 23.8 +/- 13.8% wet mass, mean +/-s.d.) relative to northern fish (b = 2.7, K = 2.22 +/- 0.39, fat = 3.4 +/- 3.2% wet mass, respectively), suggesting that sewage-derived organic matter was an enriched diet, which allowed an enhanced body mass gain and fat accumulation compared to organic-poor vegetal detritus in the north Paraná area. Buenos Aires fish also showed higher hepato-somatic indices (mean +/-s.d. I(H) 1.41 +/- 0.49 v. 0.70 +/- 0.32, respectively), which correlated with their two to three orders of magnitude higher hydrocarbon and polychlorinated biphenyl (PCB) loads, suggesting an enhanced detoxifying metabolism. The northward migration of fatty P. lineatus was evidenced by the presence of clear outliers in the L(S) and M(T) relationship, K and fat content along the Paraná River.

Analysis of trophic networks and carbon flows in south-eastern Baltic coastal ecosystems

Carbon flows in five south-eastern Baltic coastal ecosystems (Puck Bay, Curonian Lagoon, Lithuanian coast, Gulf of Riga coast and Pärnu Bay) were compared on the basis of ECOPATH models using 12 common functional groups. The studied systems ranged from the hypertrophic Curonian Lagoon to the mesotrophic Gulf of Riga coast. Interestingly, we found that macrophytes were not consumed by grazers, but rather channelled into the detritus food chain. In all ecosystems fisheries had far reaching impacts on their target species and on the food-web in general. In particular, benthic food-webs were partly affected by indirect fisheries effects. For example, fisheries tend to change the biomass of piscivorous fish, causing a cascading effect on benthivorous fish and macrozoobenthos. These cascades are ecosystem specific and need to be considered when using benthic invertebrates as productivity and eutrophication indicators. Odum’s maturity attributes allowed a ranking of costal ecosystems according to their maturity. Namely, the community development decreased in the following order: Pärnu Bay > Gulf of Riga coast > Lithuanian coast > Puck Bay > Curonian Lagoon.

F. Schiemer, D. Simon, U.S. Amarasinghe & J. Moreau (eds): Aquatic ecosystems and development: comparative Asian perspectives

This publication is the result of fruitful collaborative project FISHSTRAT funded by the EU’s INCO-DC programme. This project may be regarded as the continuation of an earlier tropical limnology project, the famous Parakrama Samudra reservoir project (Schiemer 1983), which studied this beautiful, ancient reservoir in the north-east of Sri Lanka more than 25 years ago. The results of this study and hypotheses emerging from these, inspired a whole generation of tropical limnologists. As for the Parakrama Samudra project, the idea for FISHTRAT project came from three prominent members of the earlier Pakrama Samudra team: Nan Duncan (Holloway College, UK), Fritz Schiemer (University of Vienna, Austria) and Upali Amarasinghe (Kellaniya University, Sri Lanka). They originally wanted to limit the project to Sri Lanka, but because the EU rules stipulated three countries in the same region, they included Thailand and Philippines as well. The book is dedicated to late Annie (Nan) Duncan, who coordinated the FISHSTRAT project until she became ill. This ambitious project had the aim to gain via multi-disciplinary and system-oriented research a better insight into the complex interrelationships in freshwater systems for formulating sustainable development policy recommendations for tropical water bodies. Research was carried out during 1998–2002 in five water bodies (four reservoirs and one lake) and their catchment areas in Sri Lanka, Thailand and the Philippines. This system-oriented approach integrated, limnology, fish ecology, fisheries, aquaculture and socio-economics conditions of the riparian fishing communities. To facilitate comparisons, the same methods, tools, gear and research strategy were used for all water bodies. This north– south partnership involved researchers from five European and three Asian countries. In total, 33 authors from 16 institutions were involved in writing the 23 book chapters. Limnology, including fish ecology, dominates 14 chapters, whereas fisheries and socio-economics are each represented by three chapters. Aquaculture with one chapter is clearly under represented. The whole effort is remarkable, taking into account the huge difficulties of coordinating the large number of people with different cultures and perceptions. This 23-chapter book has six sections. The first section (chapters 2–4) provides a general description of physical, hydrological and catchment characteristics of the water bodies. The second section (chapters 5–9) compares different aspects of the ecosystems. It focuses on phytoplankton community structure and factors governing phytoplankton primary production. Role of bacterial activity in the detrital food chain, seasonality, biomass and production of zooplankton populations are also discussed. The third section (chapters 10–14) focuses on fish ecology, use of hydro-acoustics for assessing fish stocks, feeding R. D. Gulati (&) Centre for Limnology, Nieuwersluis, The Netherlands e-mail: R.Gulati@nioo.knaw.nl