As interações tróficas de 31 espécies de peixes e 2 de lulas da Baía do Araçá, São Sebastião (SP), foram investigadas por meio dos isótopos estáveis de carbono (δ13C) e nitrogênio (δ15N). Os valores de δ13C das espécies variaram entre -17,2‰ e -12,1‰, e os de δ15N, entre 10,0‰ e 14,5‰. Os valores de δ13C dos produtores e consumidores permitiram indicar que as espécies analisadas participam das teias tróficas, pelágica e bentônica, e têm como base da cadeia alimentar o fitoplâncton, os microfitobentos e a matéria orgânica dos sedimentos. Maiores valores de δ13C nos peixes e lulas foram registrados no verão, associados a valores mais altos na base. As posições tróficas das espécies variaram entre 3,18 e 4,72, indicando que atuam como consumidores secundários e terciários. A composição da dieta dos peixes, avaliada pelo modelo de mistura isotópica, apontou elevada contribuição de presas como Polychaeta, Tanaidacea e Ophiuroidea, grupos com alta abundância na Baía do Araçá e no Canal de São Sebastião. A ingestão de presas disponíveis no interior da baía e no canal evidenciou a importância desses peixes e lulas como carreadores de nutrientes, realizando tanto acoplamento pelágico-bentônico, como entre as regiões sublitoral e entremarés da Baía do Araçá. / The trophic interactions of 31 fish species and 2 squid species of the Araçá Bay, São Sebastião (São Paulo, Brazil), were investigated through carbon (δ13C) and nitrogen (δ15N) stable isotopes. The δ13C of the species ranged from -17.2‰ to -12.1‰, and the δ15N, from 10.0‰ to 14.5‰. The δ13C data of the producers and consumers indicated that the species analysed are part of the pelagic and benthic trophic webs, and have phytoplankton, microphytobenthos and organic matter from the sediment as the base of the food web. Higher values of δ13C were registered in the summer, linked to the higher values at the base. The trophic positions of the species varied between 3.18 e 4.72, an indication that they act as secondary and tertiary-quaternary consumers. The diet composition of fish, evaluated trough the isotope mixing model, showed high contribution of prey, such as Polychaeta, Tanaidacea and Ophiuroidea, groups highly abundant in the Bay and the adjacent São Sebastião Channel. The intake of available prey in the intertidal region and in the Channel revealed the importance of the fish and squid as nutrient pathway links, coupling the pelagic-benthic systems and the sublittoral and intertidal regions of the Araçá Bay.

Gegenstand der Arbeit war die Untersuchung der Rolle der Schwebegarnele Mysis relicta im pelagischen Nahrungsnetz des Breiten Luzins unter besonderer Berücksichtigung der trophischen Interaktionen zur Kleinen Maräne Coregonus albula. Schwerpunkte waren die Abundanz und räumlich-zeitliche Verteilung von M. relicta, C. albula und dem Zooplankton sowie die trophischen Beziehungen im Pelagial. Im Vergleich zu früheren Studien war M. relicta weiträumiger und mit höherer Dichte im Untersuchungsgebiet verbreitet. Dies war auf die Verbesserung der Wasserqualität zurückzuführen. Ähnliche Verteilungsmuster führten zu starken räumlichen Überlappungen von M. relicta und C. albula. M. relicta konsumierte vorwiegend abundantes Plankton. Es zeigte sich aber auch eine Präferenz für Cladocera. Aus den in vitro ermittelten Ingestionsraten wurde für die Situation im Freiland ein starker Fraßdruck von M. relicta auf das Zooplankton abgeleitet. In Kombination mit einer Überschneidung der Beutespektren führte das zur Nahrungskonkurrenz zwischen M. relicta und C. albula. Andererseits war M. relicta eine wichtige Beute für C. albula und wurde stark positiv selektiert. Die Fettsäuremuster der untersuchten Organismen waren überwiegend durch ihre Nahrung beeinflusst. Die Aufnahme von M. relicta wurde nicht durch das Auftreten spezifischer Fettsäuren bei C. albula nachgewiesen. Grundsätzlich entsprach der Energietransfer im Nahrungsnetz des Breiten Luzins allgemeinen Modellen mit 10 % Transfereffizienz zwischen benachbarten trophischen Ebenen. Im Einzelnen zeigten sich aber auch Abweichungen, die größtenteils auf M. relicta zurückzuführen waren. Durch ihre omnivore Ernährung und als Beute für C. albula schafft M. relicta zusätzliche Verbindungen zwischen den trophischen Ebenen. Insgesamt hat M. relicta einen weitreichenden Einfluss auf die Struktur und den Energietransfer des Nahrungsnetzes im Breiten Luzin, wodurch ihr Vorkommen für das Gewässer von besonderer Bedeutung ist. / The aim of the study was to investigate the role of the opossum shrimp Mysis relicta in the pelagic food web of Lake Breiter Luzin (Germany) with special focus on trophic interactions with European cisco Coregonus albula. Main aspects were the abundance and temporal and spatial distribution of M. relicta, C. albula and zooplankton as well as trophic relationships in the food web. As a result of improved water quality M. relicta showed a wider distribution and enhanced abundances in the study area than earlier investigations suggested. Due to similar diurnal vertical distributions a great spatial overlap was evident for M. relicta and C. albula. M. relicta fed mainly on highly abundant plankton. Besides, an overall preference for cladocerans was detected. By applying estimated in vitro feeding rates to field situations it could be shown that zooplankton was strongly exploited by M. relicta. This high demand combined with similar prey preferences of C. albula led to a strong food competition between M. relicta and C. albula. On the other hand M. relicta formed high amounts in the diet of C. albula and was always positively selected. Fatty acid composition of examined organisms resembled the composition found in their dietary resources. The intake of M. relicta could not be detected by a specific fatty acid composition in C. albula. Considering highest and lowest trophic levels, transfer efficiency in Lake Breiter Luzin fit into general models assuming a transfer of 10 % between neighbouring trophic levels. Transfer between intermediate trophic levels partly differed from this general pattern. This was connected to the existence of M. relicta. Being omnivorous and by providing an important food source for C. albula the mysid established additional links between trophic levels in the food web. In summary, M. relicta is a significant factor in structuring the food web of Lake Breiter Luzin and has profound impact on the entire lake ecosystem.

Cross-boundary movements of energy and material are ubiquitous. Freshwater ecosystems receive nutrients, dissolved, and particulate organic matter from adjacent terrestrial ecosystems, whereas terrestrial ecosystems mainly receive prey organisms and detritus deposited by physical processes such as floods from freshwater ecosystems. Within lakes, fish are considered as integrators between habitats due to their high mobility, although they often occupy either near-shore littoral or open-water pelagic habitats and develop habitat-specific morphologies. Such intra-population divergence in morphological traits might limit the use of multiple habitats. In this thesis, I first focused on quantity and quality of reciprocal fluxes of particulate organic matter between freshwater and terrestrial ecosystems and responses of recipient consumers. Freshwater ecosystems generally received higher amounts of externally-produced resources than terrestrial ecosystems. Despite this discrepancy, aquatic and terrestrial consumer responses were similar, likely due to the differences in resource quality. Second, I investigated the potential of particulate organic carbon (POC) supporting benthic food webs in lakes; a pathway that has largely been neglected in previous studies. I found that POC can substantially subsidize the benthic food web and that the effects on the benthic food web were transferred to the pelagic habitat, thus emphasizing the importance of benthic pathways for pelagic production. Third, I examined how water transparency can affect intra-population divergence in perch (Perca fluviatilis). I observed that increased water transparency can considerably increase morphological divergence between littoral and pelagic populations likely due to its effects on foraging. Finally, I investigated the effects of such intra-population divergence on littoral-pelagic food web coupling. I found that low morphological divergence corresponded with high overlap in resource use, whereas strong morphological divergence resulted in low overlap in resource use. Here littoral populations mainly utilized littoral resources and pelagic populations primarily utilized pelagic resources, indicating that habitat coupling might be strongly limited when intra-population divergence is high. In conclusion, although different ecosystems seem separated by distinct physical boundaries, these boundaries are often crossed. However, the development of habitat-specific adaptive traits might limit movement between apparently contiguous habitats.

Human-mediated introductions of non-indigenous species now threaten to homogenize the biota of the Globe, causing huge economic and ecological damage. This thesis studies the ecological role of 3 invasive planktonic crustaceans, the omnivorous copepod Acartia tonsa (western Atlantic and Indo-Pacific) and the predatory cladocerans, Cercopagis pengoi (Ponto-Caspian) and Bythotrephes longimanus (Eurasian). B. longimanus invaded the North American Great Lakes in 1982, C. pengoi the Baltic in 1992 and the Great Lakes in 1999, while A. tonsa has an extensive invasion history that includes the Baltic. We review current knowledge on feeding biology of the predatory cladocerans. A study of stable C and N isotope ratios indicated mesozooplankton as the main food source of C. pengoi in the northern Baltic Sea proper, with young C. pengoi also eating microzooplankton, such as rotifers. Young-of-the-year herring did eat C. pengoi and herring trophic position shifted from 2.6 before the invasion to 3.4 after, indicating that C. pengoi had been “sandwiched” into the modified food web between mesozooplankton and fish. Salinity tolerance experiments on Acartia tonsa and co-occurring Acartia clausi showed the formers euryhaline character and high grazing potential. Energy partitioning between ingestion, production and respiration was rather constant over the tested salinity range of 2 to 33, with small differences in gross growth efficiency and cost of growth, but maximum ingestion at 10-20. Egg hatching in A. tonsa was only reduced at the lowest salinity. Extreme changes in salinity were needed to cause significant mortality of A. tonsa in the field, but its feeding activity could be severely reduced by salinity changes likely to occur in estuaries. A study of a hypertrophic estuary showed that A. tonsa can sustain a population despite very high mortality rates, caused by predation, high pH and low oxygen, helping explain the success of A. tonsa as an invader of estuaries.

The thesis combines laboratory experiments and field expeditions to study production, transfer and consumption of non-enzymatic antioxidants and thiamine in an aquatic food web. In particular, I (1) documented spatial and seasonal variation of tocopherols and carotenoids in the Baltic Sea pelagic food web, and (2) examined the effects of abiotic and biotic factors on tocopherol, carotenoid and thiamine concentrations in phytoplankton, zooplankton and fish. Moderate differences in temperature and salinity affected α-tocopherol, β-carotene and thiamine production in microalgae. Furthermore, the results suggest that acute stress favors the expression of non-enzymatic antioxidants rather than enzymatic antioxidants. Because production of α-tocopherol, β-carotene and thiamine differ markedly between microalgae, the availability of non-enzymatic antioxidants and thiamine is likely to be highly variable in the Baltic Sea and is difficult to predict. The transfer of non-enzymatic antioxidants from phytoplankton to zooplankton was biomass dependent. The field expeditions revealed that phytoplankton biomass was negatively associated with α-tocopherol concentration in mesozooplankton. Thus, increased eutrophication of the Baltic Sea followed by an increase in phytoplankton biomass could decrease the transfer of essential biochemicals to higher levels in the pelagic food web. This could lead to deficiency syndromes, of the kind already observed in the Baltic Sea. Astaxanthin is synthesized from precursors provided by the phytoplankton community. Thus biomass dependent transfer of astaxanthin precursors from phytoplankton to zooplankton could be responsible for astaxanthin deficiency in zooplanktivorous herring. Astaxanthin in herring consists mostly of all-Z-isomers, which are characterized by low bioavailability. Therefore, astaxanthin deficiency in salmon could be explained by the low concentration of this substance and its isomeric composition in herring.

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As comunidades mudam no tempo e espaço em função de pressões decorrentes da estrutura do habitat e disponibilidade de recursos. O entendimento das relações ecológicas e interações das comunidades são essenciais para o manejo com objetivo de melhorar a qualidade da água através de interferências na cadeia trófica aquática e na dinâmica do ecossistema através de modelagem ecológica. O presente estudo foi desenvolvido em dois sistemas límicos subtropicais no extremo sul do Brasil: banhados temporários (‘campos de cultivo de arroz’) e um grande lago raso, lagoa Mangueira. O objetivo do trabalho nos banhados temporários constituiu-se em avaliar a dinâmica das comunidades planctônicas e íctica durante o desenvolvimento desses ecossitemas (um ciclo produtivo de cultivo de arroz). Nossos resultados evidenciaram um claro gradiente temporal direcionado pela disponibilidade de nutrientes no banhado temporário. Entretanto, as variáveis limnológicas não apresentaram nenhuma tendência espacial entre as estações amostrais. Através de regressão linear verificou-se correlação positiva entre clorofila a, nutrientes, biomassa zooplanctônica e, em especial, biomassa de copépodos. Por outro lado, biomassa de peixes e, particularmente, peixes planctívoros foram inversamente relacionados à concentração de clorofila a. Relações significativas entre o DOC com nutrientes, biomassa de plâncton e peixes foram igualmente identificadas ao longo do ciclo produtivo do arroz. Na lagoa Mangueira, sistema raso (zmed 3m), de 90 km de comprimento, o objetivo foi avaliar a distribuição espacial e temporal de plâncton e peixes em função da presença da macrófita emergente Zizaniopsis bonariensis. Além disso, foi verificada a existência de um gradiente longitudinal na lagoa e a estrutura da teia trófica do sistema. Análise de componentes principais e análise de redundância evidenciaram a presença de gradientes espacial (Norte/Sul) e temporal (sazonal) durante o estudo. Análise de similaridade (ANOSIM) aplicada às variáveis ambientais evidenciou diferenças significativas entre os extremos da lagoa (Norte e Sul). Transparência Secchi, DOC e clorofila a foram significativamente diferentes entre os pontos amostrais do Norte e Sul. Através de ANOVA verificou-se que os efeitos temporais sazonais são mais intensos no Norte da lagoa Mangueira. Com relação à estrutura da comunidade na lagoa Mangueira, a biomassa do bacterioplâncton, clorofila a, biomassa zooplanctônica e captura de peixes foram diferentes sazonalmente após a extração do efeito da estrutura de habitat, enquanto que no Sul apenas a clorofila a apresentou variação sazonal significativa. A estrutura de habitat (junto à Z. bonariensis e em água aberta) induziu diferenças significativas na concentração de clorofila a tanto no Norte como no Sul da lagoa Mangueira, após a extração dos efeitos decorrentes da sazonalidade. A captura de peixes também foi influenciada pela estrutura de habitat no Norte, após a extração do efeito sazonal. Análise de similaridade (ANOSIM) aplicada à comunidade de peixes também demonstrou diferenças significativas entre o Norte e o Sul da lagoa Mangueira, embora diferenças entre as áreas vegetadas e águas abertas não tenham sido verificadas. Biomassa dos peixes, número de capturas e riqueza específica foram diferentes entre os pontos amostrais. Baseado nas razões de δ13C and δ15N identificou-se a estrutura trófica da lagoa, bem como a posição trófica de espécies de peixes e as fontes de carbono do sitema. Análise de isótopos estáveis de nitrogênio permitiu a identificação de dois níveis tróficos de peixes na lagoa Mangueira. Macrófitas emergentes e perifíton foram identificadas como importantes fontes de carbono que sustentam a estrutura trófica do sistema. Análise de grupamento a partir de dados de δ13C e δ15N e de conteúdo estomacal identificou um arranjo perfeitamente filogenético entre as espécies de peixes analisadas, refletindo que, em sentido amplo, nichos alimentares são compartilhados por espécies taxonomicamente relacionadas. A dinâmica trófica da espécie de peixe dominante na lagoa, Oligosarcus jenynsii foi também analisada. Foram identificadas mudanças sazonais e ontogenéticas na dinâmica alimentar da espécie, evidenciando a grande plasticidade trófica associada com uma estratégia oportunista, característica de espécies carnívoras generalistas. As informações obtidas neste estudo permitiram identificar grande heterogeneidade espacial e claro gradiente longitudinal na lagoa Mangueira, tanto de fatores bióticos quanto abióticos, com reflexos na distribuição e abundância de plâncton e peixes. De posse destas informações foi possível alcançar um entedimento sobre a estrutura atual do sistema, bem como os direcionadores da sua dinâmica. A abordagem direcionada neste trabalho sobre o entendimento da estrutura atual de um lago raso subtropical possibilita futuros estudos na área da modelagem ecológica. A dinâmica das comunidades abordadas neste estudo vem subsidiar a parametrização de um modelo ecológico, com capacidade de estabelecer prognósticos, tendo como contorno, estressores naturais e antrópicos. / Biological communities change in time and space following driving pressures from differences in habitat structure and resource availability. Understanding the ecological role and interactions within aquatic community is essential for any management action trying to improve water quality by interferences in lake food web, ecosystem dynamics and modeling. The present study was carried out in two freshwater systems in Southern Brazil: an irrigated rice field and in a large shallow system, Mangueira Lake. The goal of this study in temporary wetlands was to evaluate the plankton and fish dynamics during a productive cycle. Our results evidenced a temporal gradient by nutrients availability in the temporary wetland studied. However, the limnological variables did not display any horizontal pattern among sampling stations. Linear regression showed a positive relationship between chlorophyll a and nutrients, zooplankton biomass and copepod biomass. In contrast, fish biomass and planktivorous fish biomass were inversely related to chlorophyll a. Statistically significant relationships between DOC with nutrients, plankton and fish biomass were also identified during the rice production cycle. In Mangueira Lake, a shallow system (zmed 3m) and 90 km long, the goal was to evaluate the spatial and temporal distribution of plankton and fish biomass as a function of the presence of the emergent macrophytes Zizaniopsis bonariensis. We also analyzed the existence of longitudinal gradient in lake and the food web structure in system. The PCA and RDA analyses showed the temporal (seasonal) and spatial (North/South) gradient during the study. Analysis of similarity (ANOSIM) applied to environmental variables showed significant differences between sampling sites (North and South). Secchi transparency, DOC and chlorophyll a were significantly different in North and South sampling sites. ANOVA results showed that season effects are stronger in the Northern sampling site. Concerning the community structure in the Mangueira Lake, bacterioplankton biomass, chlorophyll a, zooplankton biomass and fish captures were different seasonally after extracting the habitat structure effect, while in the Southern sampling site only chlorophyll a presented a seasonal significant variation. Habitat structure (by Z. bonariensis stands and open water samples) induced significant differences in chlorophyll a both in North and South samples after extracting seasonal effect. Fish captures do also responded to habitat structure in the North, after extracting the season effect. Analysis of similarity (ANOSIM) applied to fish community also showed significant differences between North and South, although no significant differences between vegetated and open water zones was observed. Fish biomass, number of captures, and richness were different between sampling sites. Based on the δ13C and δ15N ratios and analysis of stomach content of fish species, we provide also a description of food web structure, trophic positions of fish species and primary producers of system. Analysis of nitrogen isotope ratios yielded two fish trophic levels in Mangueira Lake. Emergent macrophytes and periphyton were important carbon source that sustain the food web structure of the system. Cluster analysis of δ13C and δ15N values and stomach content yielded a perfect phylogenetic arrangement of species. This result reflects that major feeding niches are shared by taxonomically related species. The feeding dynamics of the dominant fish species, Oligosarcus jenynsii was analysed by using analyses of stomach contents and stable isotopes signature. Seasonal and ontogenetic change in the feeding biology of O. jenynsii was identified, showing the high feeding plasticity, in addition to an opportunistic strategy of this generalist carnivore species. This study allows identifying a large spatial heterogeneity and clear longitudinal gradient both in biotic and abiotic factors, reflecting fish and plankton distribution and abundance. The evaluated parameters are intended to feed a mathematical model for the Mangueira Lake, looking for predictable scenarios from natural and anthropogenic stressors.

As comunidades mudam no tempo e espaço em função de pressões decorrentes da estrutura do habitat e disponibilidade de recursos. O entendimento das relações ecológicas e interações das comunidades são essenciais para o manejo com objetivo de melhorar a qualidade da água através de interferências na cadeia trófica aquática e na dinâmica do ecossistema através de modelagem ecológica. O presente estudo foi desenvolvido em dois sistemas límicos subtropicais no extremo sul do Brasil: banhados temporários (‘campos de cultivo de arroz’) e um grande lago raso, lagoa Mangueira. O objetivo do trabalho nos banhados temporários constituiu-se em avaliar a dinâmica das comunidades planctônicas e íctica durante o desenvolvimento desses ecossitemas (um ciclo produtivo de cultivo de arroz). Nossos resultados evidenciaram um claro gradiente temporal direcionado pela disponibilidade de nutrientes no banhado temporário. Entretanto, as variáveis limnológicas não apresentaram nenhuma tendência espacial entre as estações amostrais. Através de regressão linear verificou-se correlação positiva entre clorofila a, nutrientes, biomassa zooplanctônica e, em especial, biomassa de copépodos. Por outro lado, biomassa de peixes e, particularmente, peixes planctívoros foram inversamente relacionados à concentração de clorofila a. Relações significativas entre o DOC com nutrientes, biomassa de plâncton e peixes foram igualmente identificadas ao longo do ciclo produtivo do arroz. Na lagoa Mangueira, sistema raso (zmed 3m), de 90 km de comprimento, o objetivo foi avaliar a distribuição espacial e temporal de plâncton e peixes em função da presença da macrófita emergente Zizaniopsis bonariensis. Além disso, foi verificada a existência de um gradiente longitudinal na lagoa e a estrutura da teia trófica do sistema. Análise de componentes principais e análise de redundância evidenciaram a presença de gradientes espacial (Norte/Sul) e temporal (sazonal) durante o estudo. Análise de similaridade (ANOSIM) aplicada às variáveis ambientais evidenciou diferenças significativas entre os extremos da lagoa (Norte e Sul). Transparência Secchi, DOC e clorofila a foram significativamente diferentes entre os pontos amostrais do Norte e Sul. Através de ANOVA verificou-se que os efeitos temporais sazonais são mais intensos no Norte da lagoa Mangueira. Com relação à estrutura da comunidade na lagoa Mangueira, a biomassa do bacterioplâncton, clorofila a, biomassa zooplanctônica e captura de peixes foram diferentes sazonalmente após a extração do efeito da estrutura de habitat, enquanto que no Sul apenas a clorofila a apresentou variação sazonal significativa. A estrutura de habitat (junto à Z. bonariensis e em água aberta) induziu diferenças significativas na concentração de clorofila a tanto no Norte como no Sul da lagoa Mangueira, após a extração dos efeitos decorrentes da sazonalidade. A captura de peixes também foi influenciada pela estrutura de habitat no Norte, após a extração do efeito sazonal. Análise de similaridade (ANOSIM) aplicada à comunidade de peixes também demonstrou diferenças significativas entre o Norte e o Sul da lagoa Mangueira, embora diferenças entre as áreas vegetadas e águas abertas não tenham sido verificadas. Biomassa dos peixes, número de capturas e riqueza específica foram diferentes entre os pontos amostrais. Baseado nas razões de δ13C and δ15N identificou-se a estrutura trófica da lagoa, bem como a posição trófica de espécies de peixes e as fontes de carbono do sitema. Análise de isótopos estáveis de nitrogênio permitiu a identificação de dois níveis tróficos de peixes na lagoa Mangueira. Macrófitas emergentes e perifíton foram identificadas como importantes fontes de carbono que sustentam a estrutura trófica do sistema. Análise de grupamento a partir de dados de δ13C e δ15N e de conteúdo estomacal identificou um arranjo perfeitamente filogenético entre as espécies de peixes analisadas, refletindo que, em sentido amplo, nichos alimentares são compartilhados por espécies taxonomicamente relacionadas. A dinâmica trófica da espécie de peixe dominante na lagoa, Oligosarcus jenynsii foi também analisada. Foram identificadas mudanças sazonais e ontogenéticas na dinâmica alimentar da espécie, evidenciando a grande plasticidade trófica associada com uma estratégia oportunista, característica de espécies carnívoras generalistas. As informações obtidas neste estudo permitiram identificar grande heterogeneidade espacial e claro gradiente longitudinal na lagoa Mangueira, tanto de fatores bióticos quanto abióticos, com reflexos na distribuição e abundância de plâncton e peixes. De posse destas informações foi possível alcançar um entedimento sobre a estrutura atual do sistema, bem como os direcionadores da sua dinâmica. A abordagem direcionada neste trabalho sobre o entendimento da estrutura atual de um lago raso subtropical possibilita futuros estudos na área da modelagem ecológica. A dinâmica das comunidades abordadas neste estudo vem subsidiar a parametrização de um modelo ecológico, com capacidade de estabelecer prognósticos, tendo como contorno, estressores naturais e antrópicos. / Biological communities change in time and space following driving pressures from differences in habitat structure and resource availability. Understanding the ecological role and interactions within aquatic community is essential for any management action trying to improve water quality by interferences in lake food web, ecosystem dynamics and modeling. The present study was carried out in two freshwater systems in Southern Brazil: an irrigated rice field and in a large shallow system, Mangueira Lake. The goal of this study in temporary wetlands was to evaluate the plankton and fish dynamics during a productive cycle. Our results evidenced a temporal gradient by nutrients availability in the temporary wetland studied. However, the limnological variables did not display any horizontal pattern among sampling stations. Linear regression showed a positive relationship between chlorophyll a and nutrients, zooplankton biomass and copepod biomass. In contrast, fish biomass and planktivorous fish biomass were inversely related to chlorophyll a. Statistically significant relationships between DOC with nutrients, plankton and fish biomass were also identified during the rice production cycle. In Mangueira Lake, a shallow system (zmed 3m) and 90 km long, the goal was to evaluate the spatial and temporal distribution of plankton and fish biomass as a function of the presence of the emergent macrophytes Zizaniopsis bonariensis. We also analyzed the existence of longitudinal gradient in lake and the food web structure in system. The PCA and RDA analyses showed the temporal (seasonal) and spatial (North/South) gradient during the study. Analysis of similarity (ANOSIM) applied to environmental variables showed significant differences between sampling sites (North and South). Secchi transparency, DOC and chlorophyll a were significantly different in North and South sampling sites. ANOVA results showed that season effects are stronger in the Northern sampling site. Concerning the community structure in the Mangueira Lake, bacterioplankton biomass, chlorophyll a, zooplankton biomass and fish captures were different seasonally after extracting the habitat structure effect, while in the Southern sampling site only chlorophyll a presented a seasonal significant variation. Habitat structure (by Z. bonariensis stands and open water samples) induced significant differences in chlorophyll a both in North and South samples after extracting seasonal effect. Fish captures do also responded to habitat structure in the North, after extracting the season effect. Analysis of similarity (ANOSIM) applied to fish community also showed significant differences between North and South, although no significant differences between vegetated and open water zones was observed. Fish biomass, number of captures, and richness were different between sampling sites. Based on the δ13C and δ15N ratios and analysis of stomach content of fish species, we provide also a description of food web structure, trophic positions of fish species and primary producers of system. Analysis of nitrogen isotope ratios yielded two fish trophic levels in Mangueira Lake. Emergent macrophytes and periphyton were important carbon source that sustain the food web structure of the system. Cluster analysis of δ13C and δ15N values and stomach content yielded a perfect phylogenetic arrangement of species. This result reflects that major feeding niches are shared by taxonomically related species. The feeding dynamics of the dominant fish species, Oligosarcus jenynsii was analysed by using analyses of stomach contents and stable isotopes signature. Seasonal and ontogenetic change in the feeding biology of O. jenynsii was identified, showing the high feeding plasticity, in addition to an opportunistic strategy of this generalist carnivore species. This study allows identifying a large spatial heterogeneity and clear longitudinal gradient both in biotic and abiotic factors, reflecting fish and plankton distribution and abundance. The evaluated parameters are intended to feed a mathematical model for the Mangueira Lake, looking for predictable scenarios from natural and anthropogenic stressors.