Short‐term variation in the ecological status of a Mediterranean coastal lagoon (NE Iberian Peninsula) after a man‐made change of hydrological regime

• 1. The Ter Vell (NE Iberian Peninsula) is a eutrophic coastal lagoon that has been mostly flooded by excessive irrigation water during recent decades. During 2001 and 2002 the lagoon was subject to several water management actions, the main consequence of which was a change in the hydrological regime due to drastically reduced irrigation water inputs to the lagoon.
• 2. In order to comply with the Water Framework Directive, all the management actions in an ecosystem should be focused on protecting and, where necessary, improving its ecological status.
• 3. The aims of this study were (1) to analyse whether the hydrological change caused by management actions have affected the ecological status of the lagoon, and (2) to discuss the suitability of several physicochemical and biological indicators for the assessment of the ecological status in this kind of coastal ecosystem.
• 4. After the change in the hydrological regime, a general improvement of the ecological status was observed mainly as a result of the significant decrease in the nitrogen Trophic State Index and in the abundance of rotifer indicative of eutrophy, and in turn by the significant increase in the water quality index QAELS, based on crustaceans and insect assemblages.
• 5. Contradictory results emerged with regard to some of the indicators used. After the hydrological change, the increase in the phosphorus Trophic State Index was related with the fact that Mediterranean confined coastal ecosystems are typically P‐enriched. In contrast with general assumptions, low diversity and richness of the zooplankton and the dominance of a few species have been related with an improvement of the ecological status after the hydrological change, when freshwater inputs were reduced and the lagoon became more confined.

Copyright © 2008 John Wiley & Sons, Ltd.     

Distribution and environmental requirements of stream habitat with Ranunculion fluitantis and Callitricho‐Batrachion vegetation in lower Belgium (Flanders)

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Time‐related changes in nutrient digestibility and faecal bile acid loss of rainbow trout (Oncorhynchus mykiss) as affected by dietary fat level and non‐starch polysaccharide level

Time‐related changes in apparent digestibility coefficients (ADC) and faecal bile acid loss as affected by dietary fat level and non‐starch polysaccharide (NSP) level were studied in rainbow trout (Oncorhynchus mykiss). Low‐Fat versus High‐Fat and Low‐NSP versus High‐NSP diets were formulated. Fish were fed for 6 weeks to apparent satiation and faeces were sampled in week 2, 4 and 6. Most nutrient ADC increased with time and increases were consistently larger for the High‐Fat and High‐NSP diets. Nevertheless, time of adaptation was equal between diets/nutrients and steady‐state digestion was reached at week 3. Although faecal bile acid loss was affected by diet, the observed time‐related decrease in faecal bile acid loss was mainly driven by a decrease in feed intake and faeces production. Fat ADC improved over time regardless of NSP level, which does not support the hypothesis that enhanced faecal bile acid loss (related to satiation feeding of high‐NSP diets) causes a depletion of the total body bile acid pool size that is critical for proper fat digestion. The high‐fat diets consistently resulted in the lowest Fat ADC, which might have been related to a lower availability of bile acids relative to the level of dietary fat.