INHABIT project

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Home Themes & Results Innovative measures (I3) Habitat - biota relationship

Rivers – Detail analyses on habitat-biota relationships

The first important consideration that can be obtained from the analysis carried out in the Mediterranean area, is that it is difficult to separate the individual effects of the various factors that contribute to the definition of environmental quality gradient, in terms of impact on aquatic organisms. Regarding biological metrics, one of the most important factors in determining the variability of the metrics can be associated to the alteration gradient, although it cannot be separated in the individual factors determining the overall anthropogenic alteration. As already highlighted, the lentic – lotic character (LRD) also clearly affects biological metrics and, in this case, its effect is easily discernible from that of other environmental descriptors expressing more specifically anthropogenic alteration (water quality, morphology, land use, etc.). By comparing the response of different biological metrics (i.e. over 50 selected) to the considered disturbance factors, it was possible to identify two main groups of metrics. The first group is strongly related to alteration gradient, the second is mostly related to lentic - lotic (LRD) gradient. The group of metrics related to the quality gradient confirms literature information and includes (among others) the following metrics: ASPT, N_EPT, EPTD , GOLD (all included into STAR_ICMi index, formally used for quality assessment). Other metrics are: Sel OLICHI_SA , DipAb , sel_TRI_GN , and LEPab (details on individual metrics can be found in INHABIT Deliverables).

Using more detailed regression approaches, for pool and riffle mesohabitats separately, some metrics responding to specific impacts have been identified, such as: habitat alterations 1 -GOLD (pool), log(SelEPTD) (pool) , DIPB_Siph_G (pool) and MTS (riffle); water pollution Sel_OLICHI_SA (pool) and MTS (pool).
Among the biological metrics potentially useful to detect problems related to the water level, number of Odonata, Coleoptera and Heteroptera (nOCH, positively correlated to LRD), LIFE index, ratio LIFE Baetis / BAETIDAE (Baetis_BAE, negatively correlated with LRD) have been identified with particular reference to the pool mesohabitat. Pool mesohabitats seem more adequate in separating alteration gradient from LRD gradient. If in presence of water abstraction it is also possible the evaluation of its effects by means of LRD.