Seasonal and inter-annual zooplankton dynamics in temporary pools with different hydroperiods

Abstract

The results of a research carried out in 2001 on nine temporary mountain pools (Northern Apennines, Italy) underlined a major role of hydroperiod in shaping zooplankton communities of temporary habitats. In 2002, the same pools were studied to assess inter-annual differences in zooplankton seasonal patterns. Data on precipitations (both snow and rainfalls) were collected to evaluate the influence of precipitation regimes on hydroperiod and concurrently on hydrochemical features and zooplankton dynamics.Mean annual snow and rainfall abundances were highly similar in both years but precipitation patterns were different. Moreover, different air temperatures were measured in the 2 years of study. These factors influenced water persistence and dry and wet cycles in the pools: in 2001, three pools dried out in summer and remained dry until autumn rainfalls (type A pools), in five pools (type B pools) the summer dry period was interrupted by re-filling due to storms in July and only in one pool water did remain for the entire research period (C1). In 2002, type A and B pools underwent only one dry phase (June-July) while C1 showed a hydroperiod similar to the one that occurred in the previous year. Overall, type A and B pools can be classified as 'seasonal' and C1 as 'near-permanent or permanent'.Principal component analysis and paired t-tests did not show significant differences between years in the hydrochemical features of the pools. However, the seasonal pools showed a wide range of variation in their hydrochemical parameters while water features of the permanent pool presented less variability.Within the pools, divergences in the number and in the type of zooplankton taxa between the 2 years were limited. Rotifer and copepod density of the seasonal pools were comparable over years and only cladocerans exhibited distinct density dynamics. Cladoceran appeared to be associated with ionic content and influenced by the occurrence of icemelting and by the wet phase length of the pools.On the contrary, the permanent pool showed diverse zooplankton seasonal patterns in 2001 compared to 2002. Over years, different pH values were measured; pH and conductivity varied with changing water volume, which in turn explained a significant amount of the observed variation in zooplankton densities in

Estado del conocimiento y principales amenazas de los humedales boscosos de agua dulce de Chile

“…Las variaciones en el nivel del agua, tanto en humedales permanentes como temporales, teóricamente son el resultado de la interacción de un conjunto de complejos procesos hidrológicos, geológicos y biológicos, tales como precipitación, infiltración, evaporación y transpiración vegetal ( Fig. 1; Fisher , Arle 2002, Mitsh & Gosselink 2007, Tavernini 2008, y de las recargas y fl ujos de aguas subterráneas y superfi ciales (Siegel 1988, Roulet 1991, Devitoa et al 1996.…”

“…Al respecto, la comunidad bacteriana sería entonces la principal encargada del reciclaje de los nutrientes de estos ambientes, sin embargo, en Chile aún son inexistentes los estudios respecto a la dinámica de los descomponedores en relación al procesamiento de la materia orgánica de esto s sistemas acuáticos altamente dependientes del bosque que sustenta. El régimen hídrico determina además muchas de las variables fi sicoquímicas del agua, determinantes en los patrones de distribución de las comunidades biológicas, entre las cuales destacan particularmente el pH y la conductividad (Nicolet et al 2004), esta última presenta un aumento antes y después de la recarga de los humedales temporales, lo cual no es solo resultado del cambio en la concentración por efecto del decrecimiento del volumen de agua, sino que además de la redilución de las sales minerales presentes en el sustrato que son resuspendidas después de periodos de precipitaciones o mediante su escorrentía desde las laderas adyacentes (Arle 2002, Tavernini et al 2005, Tavernini 2008). Sin embargo, este proceso puede manifestarse de una manera menos acentuada en estos ambientes, por efecto de la protección generada por el estrato arbóreo dominante, la cual intercepta y disminuye la velocidad de caída de las gotas, permitiendo su escur rimiento a través de las distintas estructuras vegetales (Huber & Oyarzún 1990, Huber & López 1993, Echeverría et al 2007).…”

Salinity and depth as structuring factors of cryptic divergence in Moina brachiata (Crustacea: Cladocera)

“…Hydroperiod, i.e. the length of the inundated period, is known to structure invertebrate communities (Wellborn et al 1996, Jenkins et al 2003, Frisch et al 2006, Medley & Havel 2007, Tavernini 2008. In a set of floodplain ponds, habitat depth was found to be a significant local variable influencing species richness and zooplankton community structure (Medley & Havel 2007) and the effect of water depth on species richness has also been shown for ostracods and cladocerans (Eitam et al 2004).…”

Spatial Distribution of Zooplankton Diversity across Temporary Pools in a Semiarid Intermittent River

“…Furthermore, studies have shown that the zooplankton community is sensitive to extreme variation in flow; thus species composition is changed and the succession of taxa is redirected after flow recession [20]. This results in different timing for the emergence of rotifers, cladocerans, and copepods from the inundated dry river beds [21].…”