Responses of resources and consumers to experimental flow pulses in a temporary Mediterranean stream.

Determining the resistance and resilience of resources and benthic invertebrates connected to instream refuges and species re-colonization in post-flood periods may help to elucidate mechanisms behind community recovery. This experiment simulated flow pulses in a small temporary stream in an extremely wet year, using upstream control and downstream flooded reaches at three sites in order to assess community resistance and resilience (benthos and drift), and analyse resources (periphyton and benthic organic matter) and invertebrates at pre- and post-flood time periods. The hyporheos was sampled in order to explore species exchanges with benthos. Fewer resources and benthic invertebrates at the beginning of the experiment were found than in previous studies when base flow conditions prevailed. Resource stocks and benthic invertebrates showed high resistance to the flow pulse. Interestingly, there was low resilience of benthic organic matter to natural seasonal flooding. Chlorophyll a did not recover after experimental floods; instead, it was reduced after floods, despite the more benign flow conditions and non-limiting irradiance levels, pointing to top-down control by consumers. Additionally, the experimental flood significantly disturbed only the invertebrate composition in the groundwater-fed stream, which was inhabited by the fewest adapted-to-flood-disturbances macroinvertebrates. Despite the low resilience observed, richness and densities of benthos increased during the study, evidencing progressive colonization. Around 50-60% of macroinvertebrates were present in both benthos and hyporheos. Richness increased after flooding, suggesting that the hyporheic zone could be the main source of colonizers. Three species traits characterized the hyporheos: small size, cocoons and feeders of microorganisms within the fine sediment matrix. The main results indicate that longer-than-normal flood periods in early spring may constrain invertebrate succession before the next summer drought in temporary streams. This study underscores the importance of hyporheic fauna as a significance source of colonizers, highlighting the importance of connectivity to the groundwater.

Suspended sediment, carbon and nitrogen transport in a regulated Pyrenean river.

Regulation alters the characteristics of rivers by transforming parts of them into lakes, affecting their hydrology and also the physical, chemical, and biological characteristics and dynamics. Reservoirs have proven to be very effective retaining particulate materials, thereby avoiding the downstream transport of suspended sediment and the chemical substances associated with it (e.g. Carbon, C, or Nitrogen, N). The study of fluvial transport of C and N is of great interest since river load represents a major link to the global C and N cycles. Moreover, reservoirs are the most important sinks for organic carbon among inland waters and have a potential significance as nitrogen sinks. In this respect, this paper investigates the effects of a Pyrenean reservoir on the runoff, suspended sediment, C and N derived from the highly active Ésera and Isábena rivers. Key findings indicate that the reservoir causes a considerable impact on the Ésera-Isábena river fluxes, reducing them dramatically as almost all the inputs are retained within the reservoir. Despite the very dry study year (2011-2012), it can be calculated that almost 300,000 t of suspended sediment were deposited into the Barasona Reservoir, from which more than 16,000 were C (i.e. 2200 t as organic C) and 222 t were N. These values may not be seen as remarkable in a wider global context but, assuming that around 30 h m(3) of sediment are currently stored in the reservoir, figures would increase up to ca. 2.6×10(6) t of C (i.e. 360,000 t of organic C) and 35,000 t of N. Nevertheless, these values are indicative and should be treated with caution as there is incomplete understanding of all the processes which affect C and N. Further investigation to establish a more complete picture of C and N yields and budgets by monitoring the different processes involved is essential.

Esterases activities and lipid peroxidation levels in muscle tissue of the shanny Lipophrys pholis along several sites from the Portuguese Coast.

This study is part of a project aiming to validate the use of the intertidal shanny Lipophorys pholis as a sentinel species in pollution monitoring in NW European marine ecosystems. To this end, a characterisation of acethylcholin (AChE), butyrylcholin (BChE) and propionylcholin (PrChE) esterases in L. pholis muscle was performed and the results indicated that AChE was predominant. Furthermore, the use of eserine sulphate and BW284c51 (0.64-800 microM), and iso-OMPA (0.08-16 mM), confirmed the measurement of true cholinesterases (ChEs) as well as the presence of pseudocholinesterases. The field application of these markers to L. pholis, sampled in seven locations along the Portuguese coast, revealed that fish were likely to be affected by neurotoxic compounds. This was indicated by the significant depletion of AChE (p<0.05) in animals collected at urban and industrialised sites, compared with those from reference locations. The inclusion of a marker of effect, measured as lipid peroxidation levels in muscle tissue, also revealed the existence of site differences. Overall, the study further validates the utility of L. pholis in pollution monitoring studies.