Search

Adaptation in and around estuaries, to ensure the future resilience of both the natural environment and the communities that are located alongside is an increasingly pressing need. As part of an adaptation planning program for the Basque estuaries (northern Spain, south-eastern Bay of Biscay), a modelling system to simulate the morphological response of the Oka estuary to climate change has been developed. Existing knowledge was used as the basis to frame this pilot modelling examining both the short-term change (storm, seasonal, annual) and the longer-term changes (decades to eons). In this paper, we focus on the long-term response and consideration of the output from the process model is limited to the data that was extracted to help parameterize the long-term model. The latter was then used to examine the response of the estuary to the past changes over a historical time scale, where observations from foraminiferal analysis and saltmarsh response were used to establish the predictive validity of the model. Forcing the model with a linear rate of sea level rise representative of the 20th century, the estuary keeps pace with sea level rise in agreement with the observations. An 18.6-year periodic variability was identified over the saltmarshes, by including the effect of the nodal tide, with the last deposition maximum occurring in 2020. The effect of the opening of a saltmarsh that was drained at the beginning of the 18th century was investigated using a simplified schematization and showed sedimentation rates of up to one order of magnitude larger than in natural marsh, in general agreement with the rates obtained in previous studies. To predict the future response of the estuary, simulations with an exponential sea level rise were performed using scenarios obtained from the latest IPCC projections. The estuary fails to keep pace with sea level rise in any of the scenarios considered. The attendant increase in the hydroperiod over the saltmarshes is also likely impact to saltmarsh species productivity and distribution. Despite the simplifications inherent to the model, and the simplifications made in the representation of the estuary and forcing conditions, the methods presented here provide additional insights into long-term behaviour that complement information obtained from more detailed, but short-term, process models. The combined modelling approach allows adaptation measures to climate change to be considered over longer timescales. • Adaptation to climate change is a problem faced by estuaries around the world. • An approach to study adaptation options for the Basque coast (Spain) is proposed. • With a linear rate of sea level rise, the Oka estuary keeps pace with sea level rise. • The Oka estuary fails to keep pace with future projections of sea level rise. • Saltmarsh enclosure and re-opening change the morphological response of the estuary. [ABSTRACT FROM AUTHOR]

Abstract: Coastal zones are widely recognised as being particularly vulnerable to future environmental change. Although a significant number of previous papers warn of an increasing tendency in the appearance of eutrophication processes in such systems, very few papers have evaluated the influence of global climate change on eutrophication. In the Mar Menor lagoon (SE Spain), the high biomass of the main primary producer, Caulerpa prolifera Forsskal (Lamououx), covers most of the bottom, and has probably increased the resistance of the lagoon to eutrophication processes through the high uptake of nutrients from the water column and their retention in the sediments, avoiding high phytoplankton densities. Nevertheless, if climate change predictions become true, the current status of the lagoon is likely to collapse, since future environmental conditions could make C. prolifera unable to reach values of net photosynthesis greater than zero, and eutrophication processes are expected to appear. [Copyright &y& Elsevier]

Abstract: Following the principles of the European Water Framework Directive, the current Spanish water management legislation requires the definition of the environmental flow regimes for all water bodies, including estuaries. The scientific community has tried to answer the question of how much freshwater an estuary needs since the mid-1970s, resulting in the development of several methodologies and approaches in different parts of the world. However the ability to reproduce most of these approaches is difficult due to the scarcity of required data and also to the differences between the studied estuaries. In this paper, we present a methodology to calculate environmental flow regimes in well-mixed estuaries based on the numerical modelling of salinity and which takes into account the seasonal climatic and hydrologic pattern of the catchment. The approach follows three sequential steps: 1) Definition of reference conditions based on the unaltered salinity patterns and zoning of the estuary, 2) definition of salinity thresholds and 3) calculation of the minimum flows required to satisfy these thresholds. The application of the methodology to five estuaries on the northern coast of Spain has highlighted the importance of considering the hydrological variability and the division of the estuary into homogeneous zones. Moreover, the studies carried out demonstrate the ineffectiveness of river specific methodologies when used to define environmental flow regimes in several estuaries and periods, and the need to apply specific methodologies. The methodology is based on the principles defined by other already tested approaches, but its greatest advantage lies in the ability to be applied to large scales, when physical and biological data is scarce. [Copyright &y& Elsevier]

Abstract: The Ebro river flows to the Mediterranean coast of Spain. During its final stretch, the Ebro behaves in a similar way to a highly stratified estuary. This paper describes the transport of nutrients to the Ebro estuary, evaluates the general movement of nutrients in the estuarine region, using a mass balance approach, and estimates the amounts of nutrients discharged to the coastal environment. Given the strong saline stratification, this study only includes the surface layer that contains the continental freshwater. The annual nutrient budget for the Ebro estuary shows a net excess for nitrogen and phosphorus, while silicate almost attains equilibrium between addition and removal. There are several reasons for gains in nitrogen and phosphorous: a contribution of dissolved and particulate compounds in the freshwater (some of which are mineralized); a lower uptake of phytoplankton indicated by chlorophyll reduction in the estuary; an entrainment of the nutrient-rich upper part of the salt wedge; and, to a lesser extent, the impact of wastewater and agricultural water use. The biggest load discharged into the Mediterranean Sea by the Ebro is nitrogen, followed by silicate with over 10 000 tons of each deposited annually. Phosphorus is discharged at relatively low concentrations and with an annual load of about 200tyr−1. [Copyright &y& Elsevier]

Abstract: Environmental variables have been measured and sampling for ichthyoplankton has been conducted monthly, since April 2001, at three stations, located at the inner (1), middle (2) and outer (3) shelf of the central Cantabrian Sea. This paper presents the results of the study of the ichthyoplankton collected from July 2001 to June 2004. Fish larvae from 99 species, belonging to 37 families, were identified. Families with higher number of species were Gadidae, Sparidae and Labridae. The larval fish assemblage was dominated by pelagic fish species, with Sardina pilchardus, as the most abundant. There was a pronounced spring peak in larval abundance, dominated by S. pilchardus. A smaller peak, dominated by S. pilchardus and Micromesistius poutassou, was recorded in late winter at Stns 2 and 3. This pattern was evident for the three-year study. Results also indicate that this study was limited to the coastal larval fish assemblage inhabiting the central Cantabrian Sea shelf. This assemblage was temporally structured into other three assemblages: winter, late winter–spring and summer–autumn. Temperature was apparently a key factor in larval fish assemblage succession. In a scenario of global warming, this study constitutes a basis to evaluating the ongoing changes in the pelagic coastal ecosystem of the central Cantabrian Sea. [Copyright &y& Elsevier]