Paloma Alcorlo

Impact of an introduced Crustacean on the trophic webs of Mediterranean wetlands

Based on a review and our own data, we present an overview of the ecological impacts on the trophic web of Mediterranean wetlands by an introduced Decapod Crustacean, the red swamp crayfish (Procambarus clarkii). P. clarkii lacks efficient dispersal mechanisms but is very well adapted to the ecological conditions of Mediterranean wetlands (fluctuating hydroperiods with regular intervals of drought). As an opportunistic, omnivorous species, which adapts its ecology and life history characteristics, such as timing and size at reproduction to changing environmental conditions, it became readily established in most of the Mediterranean wetland environments. High reproductive output, short development time and a flexible feeding strategy are responsible for its success as an invader. Like most crayfish, it occupies a keystone position in the trophic web of the invaded system and interacts strongly with various trophic levels. It efficiently grazes on macrophytes and is one of the main factors, besides the impact of flamingos, cattle and introduced fish, of the change of many water bodies from a macrophyte dominated, clear water equilibrium to a phytoplankton driven turbid water balance. Juveniles feed on protein rich animal food with the corresponding impact on the macroinvertebrate community in competition with other crayfish or fish species. At the same time, it serves as a prey for mammals, birds and fish. Due to its predatory and grazing activity, it efficiently canalises energy pathways reducing food web complexity and structure. Feeding also on detritus it opens, especially in marshlands, the detritic food chain to higher trophic levels which results in an increase of crayfish predators. As a vector of diseases, it has a severe impact on the preservation and reintroduction of native crayfish. P. clarkii accumulates heavy metals and other pollutants in its organs and body tissues and transmits them to higher trophic levels. Due to the long history of its presence, the complex interactions it established within the invaded ecosystems and the socio-economic benefits it provides to humans, prevention and control seem the most promising management measures to reduce the negative impact of this crayfish species.

Analyzing the Social Factors That Influence Willingness to Pay for Invasive Alien Species Management Under Two Different Strategies: Eradication and Prevention

Biological invasions occur worldwide, and have been the object of ecological and socio-economic research for decades. However, the manner in which different stakeholder groups identify the problems associated with invasive species and confront invasive species management under different policies remains poorly understood. In this study, we conducted an econometric analysis of the social factors influencing willingness to pay for invasive alien species management under two different regimes: eradication and prevention in the Doñana Natural Protected Area (SW Spain). Controlling for the participation of local residents, tourists and conservationists, email and face-to-face questionnaires were conducted. Results indicated that respondents were more willing to pay for eradication than prevention; and public support for invasive alien species management was influenced by an individual’s knowledge and perception of invasive alien species, active interest in nature, and socio-demographic attributes. We concluded that invasive alien species management research should confront the challenges to engage stakeholders and accept any tradeoffs necessary to modify different conservation policies to ensure effective management is implemented. Finally, our willingness to pay estimates suggest the Department of Environment of Andalusian Government has suitable social support to meet the budgetary expenditures required for invasive alien species plans and adequate resources to justify an increase in the invasive alien species management budget.

Reproductive biology and life cycle of the invasive crayfi sh Procambarus clarkii (Crustacea: Decapoda) in diverse aquatic habitats of South-Western Spain: Implications for population control

Since its introduction to southern Spain 30 years ago, the red swamp crayfi sh Procambarus clarkii has established stable populations in both natural and man-made water bodies of the Lower Guadalquivir river basin, including the Donana National Park. In order to provide background data for potential management measures, we assessed the fertility, timing of and size at reproduction for this species at 11 sites differing in hydroperiod and habitat characteristics. Fecundity (in terms of the number of eggs per female) was size dependent, with reproduc- tive output per unit of weight being highest in large females from permanent water bodies, especially those from river branches. Size at reproduction was related to water temperature, population density, and the length of the hydroperiod. The smallest mature individuals were found in rice fi eld habitats, which had the highest densities ob- served, were fi lled with water throughout the summer, and had the longest dry period of all the habitats studied (6 months). In rice fi elds, recruitment peaks were observed in early summer and autumn. In permanent water bodies, most recruitment took place in late autumn and spring, whereas in water bodies that dry out in the summer, recruit- ment was mainly in the autumn or early winter. In order to reconcile confl icting interests between economy and ecology in the study area, we propose the transformation of unused rice fi elds, where crayfi sh densities are high, into crayfi sh culture grounds. Creating a hydrological cycle similar to that found in river branches would guarantee their large size at maturity.

Food-web structure in two shallow salt lakes in Los Monegros (NE Spain): energetic vs dynamic constraints

Energetic and dynamic constraints have been proposed as rival factors in determining food-web structure. Foodweb length might be controlled either by the amount of energy entering the web (energetic constraints) or by time span between consecutive disturbances relative to time needed to build up a population (dynamic constraints). Dynamic constraints are identified with processes functioning at a regional scale such as climate, lithology and hydrogeology. Energetic constraints are related with processes operating both at a regional and a local scale. We studied the contribution of energetic constraints to food-web organization in two temporary saline lakes with similar dynamic constraints. Lakes were sampled fortnightly during two hydroperiods (1994/1995 and 1995/1996). Differences in energetic constraints between lakes result in divergent assemblages of primary producers. Consumer assemblages in both lakes, however, are similar in species composition although differ in total biomass and species abundances. Food-webs are short with a high proportion of omnivores. To simulate an increase in the energy input entering to these systems, an addition of nutrients (to a final concentration of 100 μg·1−1 P-PO4 3−) was done in mesocosms placed within the lakes in order to obtain an increase in the phytoplankton biomass. No significant response to nutrient enrichment was found in food-web structure (composition, density or biomass).

Limitations of Protected Areas Zoning in Mediterranean Cultural Landscapes Under the Ecosystem Services Approach

Protected areas have been created worldwide to set apart certain areas from land-use transformation. The biodiversity and ecosystems protected by these areas deliver several ecosystem services. Recently, besides increasing global protected coverage, there has been a growing demand to assess the adequacy of protected areas management. In this study, we assessed how the management of protected areas can deal with ecosystem services taking as example the Doñana and Sierra Nevada protected areas (Spain). For that aim we analyzed the protected area management plans, mapped seven ecosystem services, and assessed how they are affected by protected area zoning and land-use intensity. We found that although provisioning and cultural services are included in the management plans of the protected areas under a different terminology, regulating services are barely addressed. Ecosystem service delivery varies depending on several factors including the protection category of the protected areas (protection intensity), land-use intensity and geomorphological factors, among others. Therefore, we discuss that integrating ecosystem services in protected area management requires dealing with complexity, necessitating the establishment of specific goals for ecosystem service delivery, which include ecosystem service synergies and trade-offs.

Ecosystem services associated with a mosaic of alternative states in a Mediterranean wetland: case study of the Doñana marsh (southwestern Spain)

Abstract Aquatic systems can flip from clear water to turbid water states. Previous research in shallow wetlands from the northern temperate zone identify clear water states as the most socially desirable based on their enhanced capacity to host biodiversity and deliver ecosystem services. However, the degree to which this model stands for Mediterranean shallow wetlands remains largely unexplored. We analyse ecosystem services associated with alternative stable states in the Doñana marsh (southwestern Spain). First, clear and turbid water states of the marsh are identified. Then, four critical ecosystem services are characterized together with the key species, and ecosystem functions on which they depend. Ecosystem service performance under the alternative stable states is assessed combining qualitative and quantitative analysis of biophysical indicators. Our results describe a patchy mosaic in which clear water and turbid water states co-exist in the marsh. All ecosystem services analysed performed better in macrophyte-dominated clear water states. Editor D. Koutsoyiannis; Guest editor M.C. Acreman Citation Gómez-Baggethun, E., Alcorlo, P. and Montes, C., 2011. Ecosystem services associated with a mosaic of alternative states in a Mediterranean wetland: case study of the Doñana marsh (southwestern Spain). Hydrological Sciences Journal, 56 (8), 1374–1387.

Effects of land use on taxonomic and functional diversity: a cross-taxon analysis in a Mediterranean landscape.

Land-use change is the major driver of biodiversity loss. However, taxonomic diversity (TD) and functional diversity (FD) might respond differently to land-use change, and this response might also vary depending on the biotic group being analysed. In this study, we compare the TD and FD of four biotic groups (ants, birds, herbaceous, woody vegetation) among four land-use types that represent a gradient of land-use intensity in a Mediterranean landscape (Mediterranean shrublands, dehesas, mixed-pine forests, olive groves). Analyses were performed separately at two different spatial scales: the sampling unit scale and the site scale. Land-use intensity effects on TD and FD were quite different and highly varied among the four biotic groups, with no single clear pattern emerging that could be considered general for all organisms. Additive partitioning of species diversity revealed clear contrasting patterns between TD and FD in the percentage of variability observed at each spatial scale. While most variability in TD was found at the larger scales, irregardless of organism group and land-use type, most variability in FD was found at the smallest scale, indicating that species turnover among communities is much greater than functional trait turnover. Finally, we found that TD and FD did not vary consistently, but rather followed different trajectories that largely depended on the biotic group and the intensity of land-use transformation. Our results highlight that the relationship of land use with TD and FD is highly complex and context-dependent.

Assessing the trophic ecology of crayfish: a case study of the invasive Procambarus clarkii

INTRODUCTIONFreshwater crayfish, among the largest invertebrate members of biologicalcommunities in non-marine ecosystems throughout the world, have a func-tional role that is tightly linked to their trophic ecology both as consumers of alarge variety of food sources and as prey for a number of vertebrate predatorsranging from fish to mammals (Hogger 1988). Although the low diversity ofcrayfishspeciesinEurope,ascomparedtothatinNorthAmerica,mightsuggesta low significance of this group to the functioning of ecosystem, the recentintroduction of several non-indigenous species has changed this view dramati-cally (Chapter 28).Severeenvironmentalimpactsatboththepopulationandtheecosystem levelfollowed those introductions. Impacts produced on other (indigenous) crayfishshould be distinguished from those impacts affecting non-crayfish species. Theformer ones are frequently related to the spread of diseases (mainly the crayfishplague, Aphanomyces astaci Schikora) and to competitive interactions; whereas

Is it possible to predict the salinity of Iberian salt lakes from their conductivity

Conductivity measures have been widely used to estimate salinity, an obvious feature of salt lakes. Regression analysis using log-log linear model provides an adequate approach to the study of the relationship between both variables. However, actual use of that kind of statistical model suffers too frequently from lack of correctness. We have studied conductivity-salinity relationships for 69 salt lakes (128 samples) on the Iberian peninsula. Despite the satisfactory fit of the data to the model (r2 = 0.88), predictive efficiency is shown to be low. This feature, which is likely to be common to this relationship anywhere, is mainly related to heterogeneity in ionic composition.