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Large-ccale prediction of seagrass distribution integrating landscape metrics and environmental factors: The case of cymodocea nodosa (Mediterranean-Atlantic)

Publication . Chefaoui, Rosa M.; Assis, J.; Duarte, Carlos M.; Serrão, Ester

Understanding the factors that affect seagrass meadows encompassing their entire range of distribution is challenging yet important for their conservation. Here, we predict the realized and potential distribution for the species Cymodocea nodosa modelling its environmental niche in the Mediterranean and adjacent Atlantic coastlines. We use a combination of environmental variables and landscape metrics to perform a suite of predictive algorithms which enables examination of the niche and find suitable habitats for the species. The most relevant environmental variables defining the distribution of C. nodosa were sea surface temperature (SST) and salinity. We found suitable habitats at SST from 5.8 A degrees C to 26.4 A degrees C and salinity ranging from 17.5 to 39.3. Optimal values of mean winter wave height ranged between 1.2 and 1.5 m, while waves higher than 2.5 m seemed to limit the presence of the species. The influence of nutrients and pH, despite having weight on the models, was not so clear in terms of ranges that confine the distribution of the species. Landscape metrics able to capture variation in the coastline enhanced significantly the accuracy of the models, despite the limitations caused by the scale of the study. We found potential suitable areas not occupied by the seagrass mainly in coastal regions of North Africa and the Adriatic coast of Italy. The present study describes the realized and potential distribution of a seagrass species, providing the first global model of the factors that can be shaping the environmental niche of C. nodosa throughout its range. We identified the variables constraining its distribution as well as thresholds delineating its environmental niche. Landscape metrics showed promising prospects for the prediction of coastal species dependent on the shape of the coast. By contrasting predictive approaches, we defined the variables affecting the distributional areas that seem unsuitable for C. nodosa as well as those suitable habitats not occupied by the species. These findings are encouraging for its use in future studies on climate-related marine range shifts and meadow restoration projects of these fragile ecosystems.

2016-07Journal article

Restricted access

Accounting for uncertainty in predictions of a marine species: Integrating population genetics to verify past distributions

Publication . Chefaoui, Rosa; Serrao, Ester

We develop a new perspective on the uncertainties affecting the predictions of coastal species distributions using patterns of genetic diversity to assess the congruence of hindcasted distribution models. We model the niche of the subtidal seagrass Cymodocea nodosa, for which previous phylogeographic findings are used to contrast hypotheses for the Last Glacial Maximum (LGM) in the Mediterranean and adjacent Atlantic coastal regions. We focus on amelioration of sampling bias, and explore the influence of other sources of uncertainty such as the number of variables, Ocean General Circulation Models (OGCMs), and thresholds used. To do that, we test geographical and environmental filtering of presences, and a species-specific weighted filter related to political boundaries for background data. Contrary to our initial hypothesis that reducing sampling bias by means of geographical, environmental or background filtering would enhance predictive power and reliability of the models, none of these approaches consistently improved performance. These counter-intuitive results might be explained by the higher relative occurrence area (ROA) inherent to linear coastal study areas in relation to terrestrial regions, which may cause worse predictions and, thus, higher variability among models. We found that the Ocean General Circulation Models (OGCMs), the threshold and, to a smaller extent, the number of variables used, conditioned greatly the variability of the predictions in both accuracy and geographic range. Despite these uncertainties, all models achieved the goal of identifying long-term persistence regions (glacial refugia) where the highest genetic diversity for Cymodocea nodosa is found nowadays. However, only the CCSM corroborated the hypothesis, raised in previous studies, of a vicariant process in shaping the species' genetic structure. (C) 2017 Elsevier B.V. All rights reserved.

2017-09Journal article

Open access

Abandonment of traditional saltworks facilitates degradation of halophytic plant communities and Carpobrotus edulis invasion

Publication . Chefaoui, Rosa; Chozas, Sergio

Aims In Mediterranean countries, traditional salt exploitation has been practiced over centuries. However, there is a progressive reduction of active saltworks, causing changes in the adjacent halophytic communities and, ultimately, the invasion by opportunistic plant species. Assessing the impact of land use change is key to understanding and protecting these fragile wetland ecosystems. Here, we explore how the abandonment of saltworks is impacting plant communities. We assess if the reduction in saltworks activity alters the composition of protected halophytic communities and favours the invasion by Carpobrotus edulis, an invasive species in many coastal regions throughout the world. Location The Natural Park of Ria Formosa (Algarve, Portugal). Methods We studied variations in the structure of halophytic communities affected to different degrees by C. edulis over three saltworks land use regimes in the Ria Formosa. Plant cover and soil salinity were estimated in a total of 60 transects pertaining to two saltworks complexes harbouring different land use and hydrologic regimes. We performed a non-metric multidimensional scaling ordination of saltworks based on plant cover and identified the indicator species of each saltworks class. Results We found that plant communities significantly varied among types of saltworks according to the pattern of soil salinity and hydrologic regime. We identified C. edulis as the main indicator species of the abandoned saltworks' communities, characterized by less saline soils and being desiccated in summer. Conclusions Land-use change caused by the abandonment of salinas facilitated the transition of halophytic into psammophytic communities and the invasiveness of C. edulis. The maintenance of traditional saltworks activities is vital for the preservation of this fragile wetland ecosystem.

2019-06Journal article

Open access

Integrating reproductive phenology in ecological niche models changed the predicted future ranges of a marine invader

Publication . Chefaoui, Rosa; Serebryakova, Alexandra; Engelen, Aschwin; Viard, Frédérique; Serrao, Ester

Aim Phenology of a wide diversity of organisms has a dependency on climate, usually with reproductive periods beginning earlier in the year and lasting longer at lower latitudes. Temperature and day length are known environmental drivers of the reproductive timing of many species. Hence, reproductive phenology is sensitive to warming and is important to be considered for reliable predictions of species distributions. This is particularly relevant for rapidly spreading non-indigenous species (NIS). In this study, we forecast the future ranges of a NIS, the seaweed Sargassum muticum, including its reproductive phenology. Location Coastal areas of the Northern Hemisphere (Pacific and Atlantic oceans). Methods We used ecological niche modelling to predict the distribution of S. muticum under two scenarios forecasting limited (RCP 2.6) and severe (RCP 8.5) future climate changes. We then refined our predictions with a hybrid model using sea surface temperature constraints on reproductive phenology. Results Under the most severe climate change scenario, we predicted northward expansions which may have significant ecological consequences for subarctic coastal ecosystems. However, in lower latitudes, habitats currently occupied by S. muticum will no longer be suitable, creating opportunities for substantial community changes. The temperature constraints imposed by the reproductive window were shown to restrict the modelled future species expansion strongly. Under the RCP 8.5 scenario, the total range area was expected to increase by 61.75% by 2100, but only by 1.63% when the reproductive temperature window was considered. Main conclusions Altogether these results exemplify the need to integrate phenology better to improve the prediction of future distributional shifts at local and regional scales.

2019-05Journal article

Open access

Environmental drivers of distribution and reef development of the Mediterranean coral Cladocora caespitosa

Publication . Chefaoui, Rosa; Casado-Amezua, Pilar; Templado, Jose

Cladocora caespitosa is the only Mediterranean scleractinian similar to tropical reef-building corals. While this species is part of the recent fossil history of the Mediterranean Sea, it is currently considered endangered due to its decline during the last decades. Environmental factors affecting the distribution and persistence of extensive bank reefs of this endemic species across its whole geographic range are poorly understood. In this study, we examined the environmental response of C. caespitosa and its main types of assemblages using ecological niche modeling and ordination analysis. We also predicted other suitable areas for the occurrence of the species and assessed the conservation effectiveness of Mediterranean marine protected areas (MPAs) for this coral. We found that phosphate concentration and wave height were factors affecting both the occurrence of this versatile species and the distribution of its extensive bioconstructions in the Mediterranean Sea. A set of factors (diffuse attenuation coefficient, calcite and nitrate concentrations, mean wave height, sea surface temperature, and shape of the coast) likely act as environmental barriers preventing the species from expansion to the Atlantic Ocean and the Black Sea. Uncertainties in our large-scale statistical results and departures from previous physiological and ecological studies are also discussed under an integrative perspective. This study reveals that Mediterranean MPAs encompass eight of the ten banks and 16 of the 21 beds of C. caespitosa. Preservation of water clarity by avoiding phosphate discharges may improve the protection of this emblematic species.

2017-12Journal article

Open access