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Ecological assessment of an intermitent Mediterranean river using community structure and function: evaluating the role of different organism groups
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Resumo(s)
1. Reliable lotic ecological monitoring requires knowledge of river typology, environmental
factors, the effect of stressors known here as ‘pressures’ and appropriate indicators
of anthropogenically induced change. We sampled benthic macroinvertebrate, fish, bird
and macrophyte communities along an intermittent Mediterranean river and analysed
community structure (relative abundance) and function (metrics) relative to environmental
and pressure gradients in order to identify suitable indicator group(s) for future
monitoring and mitigation programmes.
2. Principal components analysis revealed that scale-dependent longitudinal differences in
valley form separated narrower higher lying sites and tributaries with good quality
habitats from more open degraded sites lower down the river continuum on a small
floodplain and large scale pressures describing changes in land use related to agriculture
with associated physical bankside and channel impacts.
3. Forward selection of variables in redundancy analysis (RDA) showed that reach scale
environmental variables were selected more frequently than pressure variables for each
organism group. Altitude and pH were highly redundant within and between groups,
indicating essentially longitudinal structural and functional distribution patterns. Redundancy
was far lower between selected pressure variables, but single or no pressure
variables were retained for some organism groups indicating poor association of
functional data, in particular, with the identified pressures. All RDA results indicated a
longitudinal pH gradient, highlighting the combined effect of multiple environmental and
pressure based mechanisms on organism groups.
4. Large, mobile organisms such as fish and birds provided a reliable link between
organism structure and function, environmental factors and physical disturbance of the
channel, bankside and wider river corridor. Benthic macroinvertebrate and macrophyte
structural data revealed distribution patterns in relation to water velocity, a key parameter
for developing appropriate compensation measures.
5. Results clearly show the importance of assessing patterns of both functional and
structural change across multiple organism groups in order to identify typologically appropriate links with complex environmental and pressure gradients and develop and
implement appropriate monitoring systems
Descrição
Palavras-chave
bioassessment birds fish macroinvertebrates macrophytes Mediterranean rivers structure
Contexto Educativo
Citação
"Freshwater Biology". ISSN 0046-5070. 54 (2009) 2383-2400
Editora
Blackwell