Skip to main content
Article thumbnail
Location of Repository

Ecologia e selecção de habitat em crustáceos zooplanctónicos de lagos pouco profundos

By Bruno Branco Castro

Abstract

Apesar das evidências de que os lagos Mediterrânicos pouco profundos possuem características ecológicas distintas, o conhecimento sobre estes sistemas é limitado. Este facto é agravado pela invasão globalizada de peixes alienígenas em lagos mais quentes, cujos efeitos sobre as interacções tróficas são praticamente desconhecidos. Com o intuito de diminuir o grau de incerteza associado à ecologia destes sistemas em Portugal, foi estudada a ecologia do zooplâncton na Lagoa da Vela (Quiaios, Figueira da Foz), um lago natural pouco profundo e eutrófico que apresenta dominância de peixes alienígenas. O objectivo da investigação foi compreender os mecanismos que moldam a comunidade zooplanctónica, com particular enfoque nas suas interacções com os peixes planctívoros, dada a importância deste elo trófico de charneira. Numa primeira fase, foram caracterizadas as comunidades de zooplâncton e peixes durante um ano. A lagoa revelou ser altamente produtiva e turva, exibindo níveis elevados de sólidos em suspensão, nutrientes e clorofila a. Foi observado um contraste evidente entre o período de água transparente, dominado por Daphnia, e o resto do ano, dominado por zooplanctontes de pequenas dimensões, incapazes de controlar o crescimento algal. A pressão predatória revelou ser uma força determinante do funcionamento da lagoa, a par com o nível de partículas em suspensão. Os peixes alienígenas exibiram um grau substancial de omnivoria, com o zooplâncton a constituir um dos principais componentes da dieta. A perca-sol (Lepomis gibbosus) foi o principal peixe planctívoro, exibindo populações muito densas, sobretudo no Verão, como resultado de um recrutamento contínuo de Julho a Setembro. A predação exercida por perca-sol e outros planctívoros contribuiu para o colapso da população de Daphnia (e consequente redução da transparência), mas o desaparecimento dos dafníideos durante o Verão e Outono não pode ser explicado sem recurso a outras variáveis ambientais para além da predação. A segunda fase do estudo pretendeu avaliar as estratégias utilizadas pelos zooplanctontes para minimizar a pressão predatória a que estão sujeitos. Na Lagoa da Vela, o zooplâncton exibiu uma distribuição espacial heterogénea (no plano horizontal e vertical) dependente da transparência da água. Os padrões observados são consistentes com o evitamento de predadores visuais (i.e. peixes). A amplitude reduzida do refúgio no plano vertical e a ausência de refúgio proporcionada pela vegetação aquática tornam os zooplanctontes (sobretudo Daphnia) particularmente susceptíveis à predação. Em ambiente laboratorial, Daphnia reagiu a sinais químicos de duas espécies de peixes alienígenas presentes na lagoa através de incremento reprodutivo e redução do tamanho corporal, evidenciando uma estratégia que maximiza o seu desempenho ante predadores selectivos, conforme documentado para outras espécies de peixes planctívoros.Few studies have focused on Mediterranean shallow lakes, although there is evidence of their distinctive features. This is particularly aggravated by the widespread invasion of alien fish predators in warmer lakes, whose effects on the trophic interactions largely remain unknown. To address the uncertainty associated with the ecology of these systems in Portugal, we studied the zooplankton ecology in a shallow polymictic lake (Lake Vela, Figueira da Foz), which is dominated by alien fish species and suffers from high nutrient loading (eutrophication). The purpose of the research was to understand the mechanisms shaping the zooplanktonic community, with particular emphasis on its interactions with planktivorous fish, given the importance of this pivotal trophic link. In a first stage, surveys on the zooplankton and fish assemblages were conducted for a one-year period. Lake Vela was highly productive and turbid, displaying high levels of suspended solids, nutrients and chlorophyll a. An evident contrast was observed between a clear water phase, dominated by Daphnia, and the rest of the year, dominated by small-sized zooplankters, unable to control algal biomass. Predatory pressure was found to be a key determinant of the lake’s condition and function, along with the level of suspended particles. Alien fish displayed a substantial degree of omnivory, where zooplankton was a main component in the diet. Pumpkinseed sunfish (Lepomis gibbosus) was the main planktivore, attaining very dense populations, mostly in the summer, as a consequence of continuous recruitment from July to September. Predation exerted by pumpkinseed and other planktivores contributed to the population collapse of Daphnia (and consequent reduction in transparency), but the disappearance of the daphniids during summer and autumn cannot be explained unless environmental variables other than predation are considered. The second stage of this work intended to study how zooplankters cope with high predation pressure from the alien benthi-planktivorous fish. Zooplankton displayed a heterogeneous spatial distribution (both horizontal and vertically) in Lake Vela, which was directly dependent on transparency. The observed patterns were consistent with avoidance of visual predators (i.e. fish). The reduced amplitude of refuge in the vertical plane and the absence of refuge in aquatic vegetation make zooplankters particularly susceptible to predation. Under laboratorial environment, Daphnia responded to chemical cues from two alien fish species present in the lake by maximizing reproduction and reducing body size, as an anti-predator defence mechanism against size-selective predation, as reported for most fish taxa.Doutoramento em BiologiaFCT - SFRH/BD/6417/2001FS

Topics: Biologia, Peixes de água doce, Habitat, Zooplâncton, Interacções tróficas, Ecologia aquática, Lagos, Dafnídeos
Publisher: Universidade de Aveiro
Year: 2007
OAI identifier: oai:ria.ua.pt:10773/4668

Suggested articles

Citations

  1. (1992). A short history of eighty years of Limnology in Spain.
  2. (1993). Alternative equilibria in shallow lakes. doi
  3. (1998). Alternative stable states. doi
  4. (2001). Behavioural response of Daphnia to olfactory clues from food, competitors and predators. doi
  5. (1997). Biomanipulation in the shallow lakes: state of the art. doi
  6. (1995). Changes in light intensity and diel vertical migration - a comparison of marine and freshwater environments. doi
  7. (2003). Chemically induced anti-predator defences in plankton: a review. Hydrobiologia 491:221-239. doi
  8. (2003). Chronic responses of different clones of Daphnia longispina (field and ephippia) to different food levels. Acta Oecologica 24:S325-S332. doi
  9. (1961). Demonstration of the effect of the fish stock on the species composition of zooplankton and the intensity of metabolism of the whole plankton association. Verhandlungen Internationale Vereinigung für Theoretische und Angewandte Limnologie 14:192-195.
  10. (1999). Depth selection behaviour, fish kairomones, and the life histories of Daphnia hyalina ´ galeata hybrid clones. doi
  11. (2002). Diel horizontal migration of zooplankton: costs and benefits of inhabiting the littoral. doi
  12. (1998). Ecology of Shallow Lakes. doi
  13. (1972). Ecosystem alteration by mosquitofish (Gambusia affinis) predation. doi
  14. (2004). Effects of infochemicals released by gapelimited fish on life history traits of Daphnia: a maladaptive response? doi
  15. (1997). Effects of neonate size and food concentration on the life history responses of a clone of the hybrid Daphnia hyalina x galeata to fish kairomones. doi
  16. (1995). Effects of predator-released chemicals on some life-history parameters of Daphnia pulex. doi
  17. (1986). Estimating uncertainty in population growth rates: jackknife vs. bootstrap techniques. doi
  18. (2005). European Daphnia Species (EDS) - Taxonomic and genetic keys (Build 2006-01-12 beta). CD-ROM distributed by the authors.
  19. (2002). Experimental Design and Data Analysis for Biologists. doi
  20. (1992). Family planning in Daphnia: resistance to starvation in offspring born to mothers grown at different food levels. doi
  21. (2006). First step for an ecological risk assessment to evaluate the impact of diffuse pollution in Lake Vela (Portugal). Environmental Monitoring and Assessment doi
  22. (2003). Fish communities and food web interactions in some shallow Mediterranean lakes. doi
  23. (2004). Fish faeces as the primary source of chemical cues inducing fish avoidance diapause in Daphnia magna. doi
  24. (1995). Fish Species and Varieties Introduced into Portuguese Inland Waters. Museu Nacional de História Natural,
  25. (2001). Fish-induced life-history shifts in the cladocerans Daphnia and Simocephalus: are they positive or negative responses? doi
  26. (2000). Food of introduced pumpkinseed sunfish: ontogenic diet shift and seasonal variation. doi
  27. (2004). Genetic identification of Hyalodaphnia species and interspecific hybrids. doi
  28. (1998). Genetic markers, genealogies and biogeographic patterns in the cladocera. doi
  29. (1998). Impact of submerged macrophytes on fishzooplankton interactions in lakes. doi
  30. (2003). Impact on indigenous species biodiversity caused by the globalisation of alien recreational freshwater fisheries. doi
  31. (2003). Inducible defences in Daphnia depend on latent alarm signals from conspecific prey activated in predators. doi
  32. (2004). Inter-clonal variation in phototactic behaviour and key life-history traits in a metapopulation of the cyclical parthenogen Daphnia ambigua: the effect of fish kairomones. doi
  33. (2001). Interactions between predator kairomone and food level complicate the ecological interpretation of Daphnia laboratory results. doi
  34. (2005). Introduction pathways and establishment rates of invasive aquatic species in Europe. doi
  35. (2005). Life history strategy and depth selection behavior as alternative antipredator defenses among natural Daphnia hyalina populations. doi
  36. (2000). Macrophyte and fish chemicals suppress Daphnia growth and alter life-history traits. doi
  37. (1992). Metabolic costs during predator-induced diel vertical migration of Daphnia. doi
  38. (1999). Modelação e simulação nas lagoas de Quiaios.
  39. (2003). More than one 'fish kairomone'? Perch and stickleback kairomones affect Daphnia life history traits differently.
  40. (1999). Morphological evolution and genetic differentiation in Daphnia species complexes. doi
  41. (1997). Plano de ordenamento e gestão das lagoas das
  42. (1998). Plasticity of Daphnia magna life history traits in response to temperature and information about a predator. doi
  43. (1965). Predation, body size, and composition of plankton. doi
  44. (2006). Predator-mediated life history shifts in Daphnia: enrichment and preliminary chemical characterisation of a kairomone exuded by fish. doi
  45. (1998). Predator-mediated plasticity in morphology, life history, and behavior of Daphnia: the uncoupling of responses. doi
  46. (1997). Predators can induce swarming behaviour and locomotory responses in Daphnia. doi
  47. (2002). Relationship between fish kairomone concentration in a lake and phototactic swimming by Daphnia. doi
  48. (1994). Relative significance of direct and indirect effects of predation by planktivorous fish on zooplankton. doi
  49. (1990). Reproductive strategy of Daphnia magna affects the sensitivity of its progeny in acute toxicity tests. doi
  50. (2003). Response of Daphnia to substances released from crowded congeners and conspecifics. doi
  51. (2003). Seasonal variation of the abiotic parameters and the cladoceran assemblage of Lake Vela: comparison with previous studies. doi
  52. (2002). Swimming behaviour of Daphnia clones: differentiation through predator infochemicals. doi
  53. (1989). The adaptive significance of diel vertical migration on zooplankton. doi
  54. (1997). The change in phototactic behaviour of a Daphnia magna clone in the presence of fish kairomones: the effect of exposure time. doi
  55. (1988). The ecological role of chemical stimuli for the zooplankton: predator-avoidance behavior doi
  56. (1989). The long-term maintenance of Daphnia magna Straus for use in ecotoxicity tests: problems and prospects.
  57. (2001). The presence of chemicals exuded by fish affects the lifehistory response of Ceriodaphnia cf. dubia to chemicals with different mechanisms of action. doi
  58. (1992). The scope for biomanipulation for improving water quality. In Eutrophication: Research and Application to Water Supply. Edited by D.W. Sutcliffe
  59. (1992). To grow or not to grow - optimal resource allocation for Daphnia. doi
  60. (1997). Top-down control in freshwater lakes: the role of nutrient state, submerged macrophytes and water depth. doi
  61. (1994). Trade-offs in diel vertical migration by zooplankton: the costs of predator avoidance. doi
  62. (2000). Trimethylamine does not trigger antipredatory life history shifts doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.