Search Results (2)

Estuarine benthos, among other lifeforms of interest to water quality, can be sensitive to size-distributed suspended cohesive flocs. In such a context, tide-dependent floc mass distributions in the Tamar Estuary in the UK are revisited. At the field site close to maximum turbidity, time-series of the water level, current velocity, salinity, and suspended sediment concentration (SSC) were recorded in 1998 over several tidal cycles. Concurrently, at selected times and elevation, floc mass distributions were derived from in situ observations of the SSC, floc diameters, and settling velocities. A previously developed time-dependent model, revised to account for both multiclass floc aggregation/disaggregation and bed sediment exchange by erosion and deposition, is applied to simulate mass distributions during ebb/flood cycles on 24 June and 5 August. Although the model does not account for the density effects of salinity or sediment advection, limited comparisons between simulated and observed mass distributions indicate generally good agreement in median diameter prediction on both days. This concurrence is due to the primary role of suspended floc dynamics and only a secondary contribution from bed sediment exchange in governing floc properties. For a better prediction of the SSC variation with the tide, the effects of salinity and advection can be incorporated by coupling the modeled floc dynamics with a suitable multi-dimensional hydrodynamic code. Full article

Diadromous fish are declining across their Atlantic distribution, and the status of their future is very worrying with the additional threat posed by climate change right now. European stakeholders and policy makers know very well the benefits provided by these species, from uses such as selling fish. However, in addition to that, the diadromous fish populations provide other lesser known benefits to society, known as ecosystem services (ESs), that are now in danger. In this research, developed under the framework of the INTERREG Atlantic Area DiadES Project, ESs linked to diadromous fish are identified by reviewing existing evidence and considering ESs provided in a set of case studies across the AA (from the Gipuzkoa rivers in Spain and Loire and Mondego rivers in France and Portugal, to the Rivers Tamar, Frome and Taff in the UK). ESs identified to be related to diadromous fish populations include food provision (provisioning service), nutrient exchanges between coastal and inland habitats (regulating service) and recreational fishing and tourism linked to the societal interest for diadromous fish (cultural service). The contribution of diadromous species to supporting gastronomic festivals, brotherhoods, the knowledge systems (environmental education and research), the local identity, traditional know-how or even to the natural heritage around diadromous fish also relates to cultural ESs. Potential trade-offs are identified between services provided by diadromous fish populations and other services provided in AA rivers that support alternative benefits (i.e., flood control; electricity production; agriculture (pollution); sand extraction). By providing this list and a monetary assessment of ESs derived from diadromous fishes, DiadES wants to convey to stakeholders and policy makers the importance of these ESs, as they must consider them as part of the decision-making process. Enhancing the assessment of ESs related to diadromous fish species, including the full diversity of ESs the species contribute to (across provisioning, regulating and cultural ESs) and the health of the habitats that support them, is a major necessity to advance towards an ecosystem approach to diadromous fishes’ management. Full article