Range Shifts in the Worldwide Expansion of Oenothera drummondii subsp. drummondii, a Plant Species of Coastal Dunes

Oenothera drummondii is a coastal dunes plant species from the North American continent that has affected the natural structure and dynamics of Spanish, Israeli, and Chinese shores as an invasive species. In South Africa, Australia, New Zealand, and France, it is reported as a naturalized species. Ecological niche and species distribution modeling has been widely used as a tool to find potential global invasions and assess invasion effects. Herein, we modeled the ecological niche and the potential distribution of Oenothera drummondii, using the Köppen–Geiger climate classification, bioclimatic variables and occurrence records that have been validated in their native and non-native distribution. In the native area, the temperature and precipitation values are higher compared to non-native zones, where the low temperatures and the absence of humidity are the main climatic limitations for the species. In the environmental space, new distribution areas were identified and a partial overlap between the native and non-native niches detected. This suggests that climate matching is not occurring for the species, and that the potential invasion of coastal dune areas seems to be higher than previously observed. Therefore, new potential invasion areas, where the species is not yet distributed, were also identified. Our predictions could be used to establish ecosystem management measures to mitigate the invasion of Oenothera drummondii, helping to prevent possible negative impacts on fragile coastal ecosystems.Mexican Centre for Innovation in Ocean Energy FSE-2014-06-249795Ministerio de Economía y Competitividad CGL2015-65058-

Efecto del manejo de un Área Natural Protegida en el paisaje del bosque de manglar en la Península de Yucatán

Natural Protected Areas (NPAs) are one of the main conservation tools used to maintain biodiversity. Due to the limitations on the anthropogenic activities that are generally associated with these tools, it is important to determine their efficiency in order to justify and/or modify their operation. This study evaluates the effect of the management of the El Palmar state reserve, which was established 23 years ago, by comparing the landscape characteristics of the mangrove forest of the Natural Protected Area (NPA) and the adjacent area that has no historical conservation status. A Geographic InformationSystem (GIS) was used, as well as remote sensing techniques, based on the hierarchical analysis of quantitative characteristics of the habitat, the spectral similarity, contextual edition and the supervised classification of a multispectral Spot 5 image, to compare the area, fragmentation and compactness of ten types of mangrove habitats between the NPA and the adjacent area. The contrasted regions present the same general fragmentation pattern (p>0.05). However, when comparing the types of habitat, significant differences were observed (p<0.05) in the fragmentation, the area and the compactness of certain types of habitat. The observed differences do not indicate a clear effect of the protected area management strategies in the structure of the landscape and are possibly more related to the local conditions, ecologicalprocesses, and the natural and/or anthropogenic disturbances. Our results highlight the importance of adjusting the management strategies of the NPA in such a manner that they have a positive effect in the integrity of the mangroves forest.Las Áreas Naturales Protegidas (ANPs) son una de las principales herramientas de conservación utilizadas para mantener la biodiversidad. Debido a las limitaciones sobre las actividades antropogénicas generalmente asociadas con estas herramientas, es fundamental determinar su efectividad para justificar y/o ajustar su operación. Este estudio evalúa el efecto del manejo en la Reserva Estatal El Palmar, la cual tiene ~25 años de haber sido establecida, al comparar características del paisaje del bosque de manglar entre el Área Natural Protegida (ANP) y el área adyacente sin esquema histórico de conservación. Se utilizó un Sistema de Información Geográfica (SIG) y técnicas de percepción remota, basadas en el análisis jerárquico de características cuantitativas del hábitat, similitud espectral, edición contextual y clasificación supervisada de una imagen multiespectral Spot 5, para comparar el área, fragmentación y compactación de diez tipos de hábitat de manglar entre el ANP y área adyacente. De manera general, las regiones contrastadas presentaron el mismo patrón general de fragmentación (p>0.05). Sin embargo, al hacer una comparación por tipo de hábitat se observaron diferencias significativas (p<0.05) en la fragmentación, área y compactación de algunos tipos de hábitat. Las diferencias encontradas no indican un efecto claro de las estrategias utilizadas en el ANP en la estructura del paisaje y posiblemente estén más relacionadas con condiciones y procesos ecológicos locales y perturbaciones naturales y/o antropogénicas.Nuestros resultados resaltan la importancia de ajustar las medidas de manejo en el ANP de tal manera que éstas si tengan un efecto positivo en la integridad del bosque de manglar

Landscape ecology and conservation of the Cozumel Reefs National Park, Mexico

This thesis describes firstly the construction and use of a GIS to understand the marine landscape ecology of the Cozumel Reefs National Park, one of Mexico's most important MPAs. The thesis develops this GIS by a novel 'blend' of aerial photography and Landsat imagery. A Landsat 7 TM image was used to extend the coverage and improve the georeferencing of the high resolution aerial photography, while ground truthed polygons based on the latter were utilized to perform a supervised classification on the satellite image. A thematic map with J5 significant habitat classes was produced. Local Ecological Knowledge from diving operators was utilized to identify and characterise diving sites within the MPA and the unmanaged area to either side of it. All coral reef sites were shown to be heavily utilized and most of them are considered to be in a good condition. No relationship was found between habitat perceived condition and intensity of use. As further use is forecast and additional management is needed, three sites located on the southwest of the MPA are proposed to be designated as strict no-access areas. The GIS was then used to analyse, classify and evaluate both the MPA and then the effect of management strategies on the MPA, by comparing the p-diversity, area, fragmentation and size distribution of habitat polygons in managed and unmanaged regions. It is clear that the GIS is capable of providing clear and useful ecological measures, and was also used to show that management strategies which limit physical impact to marine habitats are having a positive effect on the integrity of some of the habitats, in particular for seagrass meadows and algae beds. During the study, Hurricane Emily struck Cozumel, so the opportunity was taken to examine differences this made to the· full set of benthic substrates of the area. Damage was variable and not all substrates were affected, suggesting that changes caused by the hurricane were related to the depths location and local characteristics ofthe island. Recommendations are made to improve the management of the MPA based on the results, and future priorities are suggested.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Mass density assessment : comparison of three methods using Oikopleura dioica (Appendicularia) as a model system

Individual and environmental mass densities have an important effect on the dynamics of suspended particulate material in the water column. We used Oikopleura dioica as a model system to compare the accuracy of mass density estimates (rho(s)) using three methods. The first one was based on a morphometric analysis which allowed the construction of a three-dimensional geometric model of the organism to estimate individual body volumes (IBV), while weight was directly measured to calculate density. The second method was derived from Stokes Law, using the settling velocity of Oikopleura houses. Finally, the actual mass density of organisms was measured using a single-density gradient column calibrated with known-density glass floats. Mean h, estimates ranged from 1.0314 g.cm(-3) to 1.0846 g(.)cm(-3), and did not differ significantly among the three methods. Nevertheless, the greatest accuracy was attained with the single-density gradient column. The methodological approach presented in this paper is useful to assess the mass density of small plankton organisms and contribute to the generation of data on the rate at which energy transfer occurs in aquatic ecosystems

Spatiotemporal variation in mangrove chlorophyll concentration using Landsat 8

There is a need to develop indicators of mangrove condition using remotely sensed data. However, remote estimation of leaf and canopy biochemical properties and vegetation condition remains challenging. In this paper, we (i) tested the performance of selected hyperspectral and broad band indices to predict chlorophyll concentration (CC) on mangrove leaves and (ii) showed the potential of Landsat 8 for estimation of mangrove CC at the landscape level. Relative leaf CC and leaf spectral response were measured at 12 Elementary Sampling Units (ESU) distributed along the northwest coast of the Yucatan Peninsula, Mexico. Linear regression models and coefficients of determination were computed to measure the association between CC and spectral response. At leaf level, the narrow band indices with the largest correlation with CC were Vogelmann indices and the MTCI (R2 > 0.5). Indices with spectral bands around the red edge (705–753 nm) were more sensitive to mangrove leaf CC. At the ESU level Landsat 8 NDVI green, which uses the green band in its formulation explained most of the variation in CC (R2 > 0.8). Accuracy assessment between estimated CC and observed CC using the leave-one-out cross-validation (LOOCV) method yielded a root mean squared error (RMSE) = 15 mg·cm−2, and R2 = 0.703. CC maps showing the spatiotemporal variation of CC at landscape scale were created using the linear model. Our results indicate that Landsat 8 NDVI green can be employed to estimate CC in large mangrove areas where ground networks cannot be applied, and mapping techniques based on satellite data, are necessary. Furthermore, using upcoming technologies that will include two bands around the red edge such as Sentinel 2 will improve mangrove monitoring at higher spatial and temporal resolutions

Local Drivers Associated to Temporal Spectral Response of Chlorophyll-a in Mangrove Leaves

The pigment content in leaves has commonly been used to characterize vegetation condition. However, few studies have assessed temporal changes of local biotic and abiotic factors on leaf pigments. Here, we evaluated the effect of local environmental variables and tree structural characteristics, in the chlorophyll-a leaf concentration (Chl-a) associated with temporal change in two mangrove species. Rhizophora mangle (R. mangle) and Avicennia germinans (A. germinans) trees of a fringe mangrove forest (FMF) and lower basin mangrove forest (BMF) were visited over a period of one year, to obtain radiometric readings at leaf level to estimate Chl-a. Measurements on tree characteristics included diameter at breast height (DBH), basal area (BA), and maximum height (H). Environmental variables included soil interstitial water temperature (Ti), salinity (Si), and dissolved oxygen (Oi), flood level (fL), ambient temperature (Tamb), and relative humidity (Hrel). Generalized linear models and covariance analysis showed that the variation of Chl-a is mainly influenced by the species, the interaction between species and mangrove forest type, DBH, seasonality and its influence on the species, soil conditions, and fL. Studies to assess spatial and temporal change on mangrove forests using the spectral characteristics of the trees should also consider the temporal variation of leave chlorophyll-a concentration

Effects of hurricanes on the stability of reef-associated landscapes [Efectos de los huracanes sobre la estabilidad de paisajes asociados con arrecifes coralinos]

The effects of Hurricane Emily (July 2005, Category 4) on nine different benthic substrates in the reef-associated landscape along the west coast of Cozumel (Mexico) were evaluated by comparing the cover of nine types of substrate on ground-truthed sites before (ten months) and after (two months) the hurricane. Four substrates showed significant differences (Wilcoxon signed-rank test, P < 0.05). Coverage of sand and sand over rock increased, while that of seagrass and hard corals decreased. The effects of the hurricane on soft corals diminished below 10 m depth. Sites between 0.5 and 5.5 m were less affected towards the southwest of the island, where the reefs are more developed. Algal cover was similar to pre-hurricane values after two months, which suggests fast algal recolonization. Cozumel reefs are considered to be healthy; however, a possible increase in the abundance of macroalgae as a result of hurricanes coupled with poorly regulated tourism activities could eventually favor a phase shift in the system

Changements saisonniers de la résilience des plages le long d'une île-barrière urbanisée

International audienceBeach width, dune height, and vegetation coverage are key parameters to assess beach resistance and resilience to storms. However, coastal development often causes beach ecosystem degradation due to poor coastal management. We propose a Coastal Resilience Index from Remote Sensors (CRIfRS) for urbanized coasts based on aerial photogrammetry. The study area, located along a 7.8 km stretch of coast on a barrier island, is characterized by persistent alongshore sediment transport and the presence of coastal structures and beach-front houses. Contrary to previous studies, we focus on anthropogenic perturbations (coastal urbanization and coastal structures), instead of hydrodynamic conditions (storms), since erosion in this region is mainly associated with alongshore sediment transport gradients induced by coastal structures. Thus, the CRIfRS is based on the relation of three indicators that affect the beach functionality for coastal protection: beach width, coastal structure influence area, and vegetation coverage. The CRIfRS was divided into five categories: Very Low resilience (VL), Low resilience (L), Medium resilience (M), High resilience (H), and Very High resilience (VH). The CRIfRS presented an important spatial and temporal variability due to changing environmental conditions and the deployment of new coastal structures. For the study period, the percentage of the coast within the VL and L resilience classification increased, whereas the percentage of the coast classified as M, H, and VH resilience decreased. During the winter storm season, the resilience increased mainly due to the cross-shore transport whilst during mean wave conditions (i.e., sea-breeze conditions) the long-shore transport becomes more persistent and thus the coastal structures play an important role interrupting the sediment flux. Additionally, the CRIfRS trajectory shows an overall increase of the L resilience and an overall decrease of the H resilience values. This study highlights the important role of anthropogenic perturbations on the assessment of coastal resilience for highly urbanized coasts. The CRIfRS can help to improve the coastal management by assessing the coastal protection capability of beaches considering both natural and anthropogenic factors

Spatiotemporal Variation in Mangrove Chlorophyll Concentration Using Landsat 8

There is a need to develop indicators of mangrove condition using remotely sensed data. However, remote estimation of leaf and canopy biochemical properties and vegetation condition remains challenging. In this paper, we (i) tested the performance of selected hyperspectral and broad band indices to predict chlorophyll concentration (CC) on mangrove leaves and (ii) showed the potential of Landsat 8 for estimation of mangrove CC at the landscape level. Relative leaf CC and leaf spectral response were measured at 12 Elementary Sampling Units (ESU) distributed along the northwest coast of the Yucatan Peninsula, Mexico. Linear regression models and coefficients of determination were computed to measure the association between CC and spectral response. At leaf level, the narrow band indices with the largest correlation with CC were Vogelmann indices and the MTCI (R2 &gt; 0.5). Indices with spectral bands around the red edge (705–753 nm) were more sensitive to mangrove leaf CC. At the ESU level Landsat 8 NDVI green, which uses the green band in its formulation explained most of the variation in CC (R2 &gt; 0.8). Accuracy assessment between estimated CC and observed CC using the leave-one-out cross-validation (LOOCV) method yielded a root mean squared error (RMSE) = 15 mg·cm−2, and R2 = 0.703. CC maps showing the spatiotemporal variation of CC at landscape scale were created using the linear model. Our results indicate that Landsat 8 NDVI green can be employed to estimate CC in large mangrove areas where ground networks cannot be applied, and mapping techniques based on satellite data, are necessary. Furthermore, using upcoming technologies that will include two bands around the red edge such as Sentinel 2 will improve mangrove monitoring at higher spatial and temporal resolutions