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4 resultados encontrados para: TEMA: Meiofauna
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Resumen en: Inglés |
Resumen en inglés

Variable hydrology of rivers strongly affects biophysical factors that influence primary production and population densities, thereby affecting the relative influence of bottom-up and top-down processes in trophic networks. Many tropical floodplain rivers have sustained seasonal flood pulses driven by precipitation patterns of the Intertropical Convergence Zone. These changes in flow alter concentrations of dissolved nutrients, aquatic primary productivity, and per-unit-area densities of aquatic organisms. Therefore, one would predict that the strength of top-down effects of animals on basal resources should shift as the annual flood pulse progresses. We conducted a series of field experiments in a Neotropical lowland river to test for effects of hydrologic phase, habitat (in-channel vs. floodplain aquatic habitat), and benthic feeding fish and meiofauna on particulate organic matter, chlorophyll, and benthic microalgae. Net ecosystem productivity of this oligotrophic river is higher during the low phase of the annual flood cycle, which is also when resident fishes are at highest densities and there is a seasonal influx of migratory benthic feeding fish. We therefore hypothesized that top-down effects of benthic-feeding fish would fluctuate temporally, with strongest effects during low water levels. We found that fish controlled the abundance of particulate organic matter and algae on solid substrates, but not on sand, during falling- and low-water phases within both channel and floodplain habitats.

Except for diatom assemblages, which responded to fish exclusion, the taxonomic structure of algal and meiofauna assemblages was not significantly influenced by fish exclusion treatments, but varied in relation to habitat type and hydrologic phase. Meiofauna densities were highest during the low-water period; experimental exclusion of meiofauna during this period had a significant effect on accumulation of particulate organic matter in sand. By controlling abundance of important basal resources, fishes and meiofauna have large potential to influence other components of this tropical ecosystem. Our findings emphasize the predictable, gradual, changes in consumer-resource interactions associated with the seasonal flood pulse in tropical river systems.

Meiobenthology: the microscopic motile fauna of aquatic sediments / Olav Giere
Giere, Olav (autor) ;
Hamburg, Germany : Springer-Verlag Berlin Heidelberg , c2009
Clasificación: 578.77 / G5
Bibliotecas: Chetumal
SIBE Chetumal
ECO030007690 (Disponible)
Disponibles para prestamo: 1
Resumen en: Español |
Resumen en español

Meiobenthology is the science of the tiny animals that live in huge numbers in all aquatic sediments. This fully revised and enlarged second edition emphasizes new discoveries and developments in this field. Major progress has been made in three general areas: - Systematics, diversity and distribution, - Ecology, food webs, and energy flow, - Environmental aspects, including studies of anthropogenic impacts. The meiobenthos of polar and tropical regions, deep-sea bottoms and hydrothermal vents are now studied in more detail. The high number of species found to survive under such extreme conditions puts them at the forefront of biodiversity studies. Molecular screening methods enable large numbers to be analyzed upon applying reasonable effort. The aim of this book is to synthesize these modern scientific achievements such that meiobenthology can play a key role in aquatic research and in assessing the health of our environment.

Resumen en: Inglés |
Resumen en inglés

From a conservation point of view, it is essential to know how fast an ecosystem can recover after physical disturbance. Meiofauna and especially harpacticoid copepods are abundant in seagrass beds and are therefore useful to study ecosystem recovery after disturbance. In the western Caribbean coast, a fragmented Thalassia testudinum seagrass bed was selected to conduct a colonization field experiment by means of plastic seagrass mimics. Meiofauna colonization, with special emphasis on harpacticoid copepods, was followed in relation to: (1) colonization time (2, 4, 6, 10, 14 and 21 days); (2) distance to source of colonizers (close and far series) and (3) leaf surface area to colonize (small, medium, large). Colonization was recorded after 2 days with average meiofauna densities of 480 ind/100 cm2 (close) and 1350 ind/100 cm2 (far) of leaf surface area, while on average 400 ind/100 cm2 were collected from the natural seagrass plants. In this early phase, the meiofauna diversity was high, with on average 8 taxa. A longer period of colonization (21 days) showed an increased meiofaunal density and diversity (average density: 3220 ind/100 cm2, 13 taxa).

Increasing meiofauna colonization with time is probably related to the development of a biofilm making the leaf more attractive for meiofauna. The effect of distance was not so pronounced as that of time. Total absolute densities were highest in the far series (5 m away from natural seagrass patch), mainly because of nematode densities. Meiofauna diversity was lower in the far series than in the close series (at the border of the natural seagrass patch). A larger individual leaf surface area did not affect the overall meiofauna densities but had a significant positive effect on copepod densities. Larger surface areas promoted the presence of epiphytic copepod families such as Tegastidae and Dactylopusiidae. Overall, we found a rapid recovery of meiofauna in fragmented seagrass beds with primary colonizers (both nematodes and benthic opportunistic copepods) originating from the sediment and later colonizers as epiphytic copepods and their nauplii from the local seagrass regeneration pool.