• [12] Hernán G., M.J. Ortega, J. Henderson, J. Alós, K. Boyer, S. Cimon, V. Combes, M. Cusson, C.M. Hereu, M. Hessing-Lewis, K. Hovel, P. Jorgensen, S. Kiriakopolos, N. Kollars, M.I. O ́Connor, J. Olsen, P.L. Reynolds, J. Ruesink, E. Voigt, F. Tomas (2020): Latitudinal variation in plant defence against herbivory in a marine foundation species does not follow a linear pattern: The importance of resource availability. Global Ecol Biogeogr. doi:https://doi.org/10.1111/geb.13217 Link
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    Abstract: Aim: Studies on latitudinal patterns in plant defence have traditionally overlooked the potential effect that resource availability may have in shaping plant defence. Likewise, latitudinal patterns of tolerance traits have rarely been studied, yet they can be a critical component of plant defence. Therefore, the aim of our study was to examine latitudinal variation in the production of tolerance and resistance traits against her- bivory along a latitudinal range and a natural gradient of resource availability from upwelling conditions. Location: Canada, North America and Mexico. Time period: Summer months of 2015. Major taxa used: The seagrass Zostera marina. Methods: We conducted experiments simulating macroherbivore (e.g., bird, fish) dam- age on the seagrass Z. marina at 10 sites across the Eastern Pacific coast (Canada– Mexico) and Quebec and analysed several traits related to resistance and tolerance strategies against herbivory. In addition, we examined the effects of potential sea- grass changes in defence strategies by performing a series of feeding experiments with mesoherbivores in a subset of sites. Results: We found that eelgrass resistance defences did not follow a linear latitudinal pattern but rather followed a bell-shaped curve which correlated with bottom-up control. In sites with higher nutrient availability, plants allocated resources to tol- erance strategies and had lower resistance traits. Furthermore, seagrasses did not respond linearly to increased herbivory pressure; while they tolerated moderate lev- els of herbivory, they underwent a significant reduction in tolerance and resistance under high herbivory levels, which also made them more susceptible to consumers in feeding experiments. Main conclusions: Our results highlight the importance that nutrient availability has in shaping latitudinal patterns of plant defence against herbivory and show how these defences may not respond linearly to increased herbivory pressure in seagrasses.

  • [11] Máñez-Crespo,J., Tuya, F., Fernández-Torquemada, Y., Royo, L., Pilar-Ruso, Y., Espino, F., Manet, P., Antich, L., Castejón,I., Curbelo, L., de la Ossa, J.A., Hernán, G., Mateo-Ramírez, A., Pereda-Briones, L., Procaccini, G., Terrados, J., Tomas, F. (2020). Seagrass Cymodocea nodosa across biogeographical regions and times: differences in meadow structure and sexual reproduction. Mar. Env. Res. 162 : 105159. https://doi.org/10.1016/j.marenvres.2020.105159 Link
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    Abstract: Seagrasses are key habitat-forming species of coastal areas. While previous research has demonstrated considerable small-scale variation in seagrass abundance and structure, studies teasing apart local from large-scale variation are scarce. We determined how different biogeographic scenarios, under varying environmental and genetic variation, explained variation in the abundance and structure (morphology and biomass allocation), epiphytes and sexual reproduction intensity of the seagrass Cymodocea nodosa. Regional and local-scale variation, including their temporal variability, contributed to differentially explain variation in seagrass attributes. Structural, in particular morphological, attributes of the seagrass leaf canopy, most evidenced regional seasonal variation. Allocation to belowground tissues was, however, mainly driven by local-scale variation. High seed densities were observed in meadows of large genetic diversity, indicative of sexual success, which likely resulted from the different evolutionary histories undergone by the seagrass at each region. Our results highlight that phenotypic plasticity to local and regional environments need to be considered to better manage and preserve seagrass meadows.

  • [10] Lester, S.E., Dubel, A., Hernán, G., McHenry, J. and Rassweiler A., (2020): Spatial planning principles for marine ecosystem restoration. Accepted in Frontiers in Marine Science
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    Abstract: Coastal and marine ecosystems characterized by foundation species, such as seagrass beds, coral reefs, salt marshes, oyster reefs, and mangrove forests, are rich in biodiversity and support a range of ecosystem services including coastal protection, food provisioning, water filtration, carbon sequestration, recreational opportunities, cultural value, among others. These ecosystems have experienced degradation and a net loss of total area in regions around the world due to a host of anthropogenic stressors, resulting in declines in the associated ecosystem services they provide. Because of the extensive degradation in many locations, increasing attention has turned to ecosystem restoration of these marine habitats. Restoration techniques for marine and coastal ecosystems are generally more expensive when compared to terrestrial ecosystems, highlighting the importance of carefully selecting locations that will provide the largest return on investment, not only for the probability and magnitude of restoration success, but also for ecosystem service outcomes. However, site selection and spatial planning for marine ecosystem restoration receive relatively little attention in the scientific literature, suggesting a need to better study how spatial planning tools could be incorporated into restoration practice. To the degree that site selection has been formally evaluated in the literature, the criteria have tended to focus more on environmental conditions beneficial for the restored habitat, and less on ecosystem service outcomes once the habitat is restored, which may vary considerably from site to site, or with more complex landscape dynamics and spatial patterns of connectivity. Here we 1) review recent (2015-2019) scientific peer-reviewed literature for several marine ecosystems (seagrass beds, salt marshes, and mangrove forests) to investigate how commonly site selection or spatial planning principles are applied or investigated in scholarly research about marine ecosystem restoration at different spatial scales, 2) provide a conceptual overview of the rationale for applying spatial planning principles to marine ecosystem restoration, and 3) highlight promising analytical approaches from the marine spatial planning and conservation planning literatures that could help improve restoration outcomes. We argue that strategic site selection and spatial planning for marine ecosystem restoration, particularly applied at larger spatial scales and accounting for ecosystem service outcomes, can help support more effective restoration.

  • [9] Rassweiler, A., Dubel, A., Hernán, G., Kushner, J.D., Caselle, J.E., Sprague, J.L., Kui, L., Lamy,T., Lester, S.E., Miller. R.J., (2020): Roving divers surveying fish in fixed areas capture similar patterns in biogeography but different estimates of density when compared with belt transects. Accepted in Frontiers in Marine Science
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    Abstract: Fish abundance and diversity are core measurements taken by many nearshore marine monitoring projects. The most common approaches for counting fish include belt transects and timed counts by roving divers, each with its own limitations. Here we evaluate a fish counting method developed by the Channel Islands National Park’s Kelp Forest Monitoring Program (KFMP), in which roving observers make fish counts that are standardized both by the time taken (30 min) and the area sampled (2000 m2 21 ). This method is potentially very useful because it combines an advantage of simple timed counts – the ability to rapidly sample a large area – with the potential to calculate area-specific density of fish, not just their relative abundance. However, the method has not been comprehensively evaluated and it is uncertain whether fish can effectively be counted in such a large target area within the allotted time. Fortunately, many sites surveyed with this method are also sampled with a more standard fish counting approach of belt transects, both by the KFMP and by the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO). Here we compare estimates of fish density obtained through the area-standardized roving diver method and belt transect methods. In paired samples we find substantial and species-specific differences in densities estimated by each method. Considering all fish taxa together we find that roving divers are likely under-sampling the target area. Despite considerable species-level variation, the different methods produce similar estimates of average diversity and find similar regional and temporal patterns in fish abundance, demonstrating that they can successfully be used in parallel even if the datasets cannot be easily combined. These analyses can guide the interpretation of roving diver data for basic research and management decisions.

  • [8] Hernán G., I. Castejón, J. Terrados and F. Tomas, (2019): Herbivory and resource availability shift plant defense and herbivore feeding choice in a seagrass system. Oecologia, pp 1-14, doi.org/10.1007/s00442-019-04364-6 Link
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    Abstract: Numerous hypotheses have been posited to explain the observed variation in plant defense strategies against herbivory. Under resource-rich environments, plants are predicted to increase their tolerance (limiting resource model; LRM) and, while the resource availability hypothesis (RAH) predicts a decrease in constitutive resistance in plant species growing in resource-rich environments, at the intraspecific level, plants are predicted to follow an opposite pattern (intraspecific RAH). Furthermore, the effect of multiple factors in modulating plant defense strategies has been scarcely explored and is more difficult to predict. Our aim was to understand how plant defense traits respond to herbivory, resource availability and their interactions, and to assess the effects on plant palatability. To this end, we performed an in situ factorial experiment at two sites simulating three herbivory levels and two nutrient availability conditions with the seagrass Posidonia oceanica. Additionally, we performed a series of feeding experiments with its two main herbivores. While plants decreased their constitutive resistance under nutrient fertilization (contrary to intraspecific RAH but in accordance to the RAH), and did not increase allocation to tolerance (likely due to resource limitation, LRM), simulated herbivory induced resistance traits. However, we found no interactive effects of nutrient fertilization and herbivory simulation on plant defense. Both herbivores responded similarly to changes in plant palatability, strongly preferring nutrient-enriched plants and non-clipped plants. This work highlights the need to better understand the drivers of plant defense intraspecific variability in response to resources, particularly in habitat-forming species where changes in plant traits and abundance will cascade onto associated species.

  • [7] Galbán-Malagón, C., G. Hernan, E. Abad, J. Dachs, (2017): Persistent Organic Pollutants in Krill from the Bellingshausen, South Scotia, and Weddell Seas. STOTEN 610-611, 1487-1495 Link
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    Abstract: Persistent organic pollutants (POPs) reach Antarctica through atmospheric transport, oceanic currents, and to minor extent, by migratory animals. The Southern Ocean is a net sink for many POPs, with a key contribution of the settling fluxes of POPs bound to organic matter (biological pump). However, little is known about POP transfer through the food web in the Southern Ocean and Antarctic waters, where krill is an important ecological node. In this study, we assessed the occurrence of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) in Antarctic krill (Euphausia superba) from the Bellingshausen, South Scotia and Weddell Seas around the Antarctic Peninsula. The concentrations of PCDD/Fs, PBDEs and PCBs in krill showed a large variability and the average were higher (generally within a factor 3) than those previously reported for eastern Antarctica. This result highlights regional differences related to atmospheric transport and deposition, and also probable regional sources due to human activities. Bioaccumulation and biomagnification factors for PCBs in krill were estimated using previously reported phytoplankton and seawater concentrations for this region. These suggested a near water-krill equilibrium for PCBs, which was not observed for water-phytoplankton partitioning. The estimated removal settling fluxes of PCBs due to the biological pump were several orders of magnitude higher than the estimated fluxes of PCBs transferred from phytoplankton to krill.

  • [6] Hernan, G., M.J. Ortega, A.M. Gandara, I. Castejon, J. Terrados and F. Tomas, (2017): Future warmer seas: increased stress and susceptibility to grazing in seedlings of a marine habitat-forming species. Glob. Chang. Biol. 00:1-14. https://doi.org/10.1111/gcb.13768 Link
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    Abstract: Increases in seawater temperature are expected to have negative consequences for marine organisms. Beyond individual effects, species-specific differences in thermal tolerance are predicted to modify species interactions and increase the strength of top-down effects, particularly in plant-herbivore interactions. Shifts in trophic interactions will be especially important when affecting habitat-forming species such as seagrasses, as the consequences on their abundance will cascade throughout the food web. Seagrasses are a major component of coastal ecosystems offering important ecosystem services, but are threatened by multiple anthropogenic stressors, including warming. The mechanistic understanding of seagrass responses to warming at multiple scales of organization remains largely unexplored, especially in early-life stages such as seedlings. Yet, these early-life stages are critical for seagrass expansion processes and adaptation to climate change. In this study, we determined the effects of a 3 month experimental exposure to present and predicted mean summer SST of the Mediterranean Sea (25°C, 27°C, and 29°C) on the photophysiology, size, and ecology (i.e., plant-herbivore interactions) of seedlings of the seagrass Posidonia oceanica. Warming resulted in increased mortality, leaf necrosis, and respiration as well as lower carbohydrate reserves in the seed, the main storage organ in seed- lings. Aboveground biomass and root growth were also limited with warming, which could hamper seedling establishment success. Furthermore, warming increased the susceptibility to consumption by grazers, likely due to lower leaf fiber content and thickness. Our results indicate that warming will negatively affect seagrass seedlings through multiple direct and indirect pathways: increased stress, reduced establishment potential, lower storage of carbohydrate reserves, and increased susceptibly to consumption. This work provides a significant step forward in understanding the major mechanisms that will drive the capacity of seagrass seedlings to adapt and survive to warming, highlighting the potential additive effects that herbivory will have on ultimately determining seedling success.

  • [5] Hernan, G., L. Ramajo, L. Basso, A. Delgado, J. Terrados, C.M. Duarte and F. Tomas, (2016): Seagrass (Posidonia oceanica) seedlings in a high-CO2 world: from physiology to herbivory. Scientific Reports 6, doi:10.1038/srep38017 Link [PDF]
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    Abstract: Under future increased CO2 concentrations, seagrasses are predicted to perform better as a result of increased photosynthesis, but the eects in carbon balance and growth are unclear and remain unexplored for early life stages such as seedlings, which allow plant dispersal and provide the potential for adaptation under changing environmental conditions. Furthermore, the outcome of the concomitant biochemical changes in plant-herbivore interactions has been poorly studied, yet may have important implications in plant communities. In this study we determined the eects of experimental exposure to current and future predicted CO2 concentrations on the physiology, size and defense strategies against herbivory in the earliest life stage of the Mediterranean seagrass Posidonia oceanica. The photosynthetic performance of seedlings, assessed by uorescence, improved under increased pCO2 conditions after 60 days, although these dierences disappeared after 90 days. Furthermore, these plants exhibited bigger seeds and higher carbon storage in belowground tissues, having thus more resources to tolerate and recover from stressors. Of the several herbivory resistance traits measured, plants under high pCO2 conditions had a lower leaf N content but higher sucrose. These seedlings were preferred by herbivorous sea urchins in feeding trials, which could potentially counteract some of the positive eects observed.

  • [4] Tomas, F., B. Martínez-Crego, G. Hernan and R. Santos, (2015): Responses of seagrass to anthropogenic and natural disturbances do not equally translate to its consumers. Glob. Chang. Biol., 21(11), 4021-4030, doi:10.1111/gcb.13024 Link
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    Abstract: Coastal communities are under threat from many and often co-occurring local (e.g., pollution, eutrophication) and global stressors (e.g., climate change), yet understanding the interactive and cumulative impacts of multiple stressors in ecosystem function is far from being accomplished. Ecological redundancy may be key for ecosystem resilience, but there are still many gaps in our understanding of interspecific differences within a functional group, particularly regarding response diversity, that is, whether members of a functional group respond equally or differently to anthropogenic stressors. Herbivores are critical in determining plant community structure and the transfer of energy up the food web. Human disturbances may alter the ecological role of herbivory by modifying the defense strategies of plants and thus the feeding patterns and performance of herbivores. We conducted a suite of experiments to examine the independent and interactive effects of anthropogenic (nutrient and CO2 additions) and natural (simulated herbivory) disturbances on a seagrass and its interaction with two common generalist consumers to understand how multiple disturbances can impact both a foundation species and a key ecological function (herbivory) and to assess the potential existence of response diversity to anthropogenic and natural changes in these systems. While all three disturbances modified seagrass defense traits, there were contrasting responses of herbivores to such plant changes. Both CO2 and nutrient additions influenced herbivore feeding behavior, yet while sea urchins preferred nutrient-enriched seagrass tissue (regardless of other experimental treatments), isopods were deterred by these same plant tissues. In contrast, carbon enrichment deterred sea urchins and attracted isopods, while simulated herbivory only influenced isopod feeding choice. These contrasting responses of herbivores to disturbance-induced changes in seagrass help to better understand the ecological functioning of seagrass ecosystems in the face of human disturbances and may have important implications regarding the resilience and conservation of these threatened ecosystems.

  • [3] Morales,L., J. Dachs, B. González-Gaya, G. Hernan, M. Abalos and E. Abad, (2014): Background Concentrations of Polychlorinated Dibenzo-p-Dioxins, Dibenzofurans, and Biphenyls in the Global Oceanic Atmosphere. Environ. Sci. Technol., 48 (17), 10198–10207, doi:10.1021/es5023619 Link
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    Abstract: The remote oceans are among the most pristine environments in the world, away from sources of anthropogenic persistent organic pollutants (POP), but nevertheless recipients of atmospheric deposition of POPs that have undergone long-range atmospheric transport (LRAT). In this work, the background occurrence of gas and aerosol phase polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin like polychlorinated biphenyls (dl-PCB) is evaluated for the first time in the atmosphere of the tropical and subtropical Atlantic, Pacific, and Indian oceans. Thirty-nine air samples were collected during the eight-month Malaspina circumnavigation cruise onboard the R/V Hespérides. The background levels of dioxins and dl-PCBs remained very low and in many cases very close to or below the limit of detection. Expectedly, the levels of PCBs were higher than dioxins, PCB#118 being the most abundant compound. In the particular case of dioxins, octachlorodibenzo-p-dioxin (OCDD) was the most abundant PCDD/F congener. Distribution of dl-PCB is dominated by the gas phase, while for PCDD/F the aerosol phase concentrations were higher, particularly for the more hydrophobic congeners. The Atlantic Ocean presented on average the highest PCDD/F and dl-PCB concentrations, being lower in the southern hemisphere. The assessment of air mass back trajectories show a clear influence of continental source regions, and lower concentrations when the air mass has an oceanic origin. In addition, the samples affected by an oceanic air mass are characterized by a lower contribution of the less chlorinated dioxins in comparison with the furans, consistent with the reported higher reaction rate constants of dibenzo-p-dioxins with OH radicals than those of dibenzofurans. The total dry atmospheric deposition of aerosol-bound ∑PCDD/F and ∑dl-PCB to the global oceans was estimated to be 354 and 896 kg/year, respectively.

  • [2] F. Varela, A. Peluzzo, F. Berrio, L. De La Rosa, A. Ruano, A. Meana, D. Gomez, R.M. García, J.R. Larreina, E. Diaz, T. Marcos, G. Hernán, D. Sanchez de Ron, H. Pascual. El Centro de Recursos Fitogenéticos - INIA: Variedades tradicionales de plantas cultivadas recolectadas en Andalucía (1929-2009). Actas de Horticultura. 55: 39-40. pdf
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    Abstract: El Centro de Recursos Fitogenéticos del INIA tiene como principal objetivo contribuir a evitar la pérdida de diversidad genética de las especies cultivadas y silvestres emparentadas, cuyo potencial genético sea susceptible de ser utilizado en agricultura y alimentación. En el presente trabajo se exponen los resultados de la conservación de variedades locales y especies silvestres emparentadas con las cultivadas, conservadas por diferentes instituciones, recolectadas en la Comunidad Autónoma de Andalucía entre los años 1929 y 2009. En los bancos españoles, se conservan un total de 5691 muestras de 10 familias, 48 géneros y 70 especies.

  • [1] M.A. Cases, P. Navarrete, D. Pérez-Mao, G. Hernán, P. Lopez-Cepero, D. Sánchez, P. Varela. Recursos genéticos y caracterización química de plantas aromáticas y medicinales en las Islas Pitiusas. Actas de Horticultura. 55: 29-30 pdf
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    Introduction: Este estudio es fruto de un Convenio de Colaboración (2009-2010) entre el INIA y la empresa Destilerías Marí Mayans C.B., financiado por el Gobern Balear, para la “Catalogación de los recursos genéticos de plantas aromáticas presentes en las Islas Pitiusas, selección y obtención de plantas madre de especies con interés comercial”. El área de prospección del Convenio se corresponde con las islas de Ibiza y Formentera (Islas Baleares, España).

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