Browsing by Author "Horta, Paulo A."
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- Bottom trawling threatens future climate refugia of rhodoliths globallyPublication . Fragkopoulou, Eliza; Serrao, Ester; Horta, Paulo A.; Koerich, Gabrielle; Assis, J.Climate driven range shifts are driving the redistribution of marine species and threatening the functioning and stability of marine ecosystems. For species that are the structural basis of marine ecosystems, such effects can be magnified into drastic loss of ecosystem functioning and resilience. Rhodoliths are unattached calcareous red algae that provide key complex three-dimensional habitats for highly diverse biological communities. These globally distributed biodiversity hotspots are increasingly threatened by ongoing environmental changes, mainly ocean acidification and warming, with wide negative impacts anticipated in the years to come. These are superimposed upon major local stressors caused by direct destructive impacts, such as bottom trawling, which act synergistically in the deterioration of the rhodolith ecosystem health and function. Anticipating the potential impacts of future environmental changes on the rhodolith biome may inform timely mitigation strategies integrating local effects of bottom trawling over vulnerable areas at global scales. This study aimed to identify future climate refugia, as regions where persistence is predicted under contrasting climate scenarios, and to analyze their trawling threat levels. This was approached by developing species distribution models with ecologically relevant environmental predictors, combined with the development of a global bottom trawling intensity index to identify heavily fished regions overlaying rhodoliths. Our results revealed the importance of light, thermal stress and pH driving the global distribution of rhodoliths. Future projections showed poleward expansions and contractions of suitable habitats at lower latitudes, structuring cryptic depth refugia, particularly evident under the more severe warming scenario RCP 8.5. Our results suggest that if management and conservation measures are not taken, bottom trawling may directly threaten the persistence of key rhodolith refugia. Since rhodoliths have slow growth rates, high sensitivity and ecological importance, understanding how their current and future distribution might be susceptible to bottom trawling pressure, may contribute to determine the fate of both the species and their associated communities.
- Calcification in free-living coralline algae is strongly influenced by morphology: implications for susceptibility to ocean acidificationPublication . Schubert, Nadine; Hofmann, Laurie C.; Almeida Saá, Antonella C.; Moreira, Anderson Camargo; Arenhart, Rafael Güntzel; Fernandes, Celso Peres; de Beer, Dirk; Horta, Paulo A.; Silva, JoãoRhodolith beds built by free-living coralline algae are important ecosystems for marine biodiversity and carbonate production. Yet, our mechanistic understanding regarding rhodolith physiology and its drivers is still limited. Using three rhodolith species with different branching morphologies, we investigated the role of morphology in species' physiology and the implications for their susceptibility to ocean acidification (OA). For this, we determined the effects of thallus topography on diffusive boundary layer (DBL) thickness, the associated microscale oxygen and pH dynamics and their relationship with species' metabolic and light and dark calcification rates, as well as species' responses to short-term OA exposure. Our results show that rhodolith branching creates low-flow microenvironments that exhibit increasing DBL thickness with increasing branch length. This, together with species' metabolic rates, determined the light-dependent pH dynamics at the algal surface, which in turn dictated species' calcification rates. While these differences did not translate in species-specific responses to short-term OA exposure, the differences in the magnitude of diurnal pH fluctuations (~ 0.1-1.2 pH units) between species suggest potential differences in phenotypic plasticity to OA that may result in different susceptibilities to long-term OA exposure, supporting the general view that species' ecomechanical characteristics must be considered for predicting OA responses.
- Corrigendum to “Golden carbon of Sargassum forests revealed as an opportunity for climate change mitigation” [Sci. Total Environ., 729 (2020) Start page – End page/ 138745]Publication . Gouvêa, Lidiane P.; Assis, J.; Gurgel, Carlos F.D.; Serrao, Ester; Silveira, Thiago C.L.; Santos, Rui; Duarte, Carlos M.; Peres, Leticia M.C.; Carvalho, Vanessa; Batista, Manuela; Bastos, Eduardo; Sissini, Marina N.; Horta, Paulo A.
- Editorial: coralline algae: globally distributed ecosystem engineersPublication . Schubert, Nadine; Schoenrock, Kathryn M.; Aguirre, Julio; Kamenos, Nicholas A.; Silva, João; Horta, Paulo A.; Hofmann, Laurie C.From the early days of phycology, coralline algae (CA) have been considered the most formidable and widely distributed algae (Woelkerling, 1988). They compose an abundant and highly diverse group, divided into geniculate (articulated) and non-geniculate species (crusts and rhodolith/maërl forms). CA are present in almost every coastal ecosystem around the world, from the intertidal to mesophotic zones (Johansen et al., 1981; Steneck, 1986; Foster, 2001). They are important ecosystem engineers that provide hard, three-dimensional substrates for a highly diverse fauna and flora (Nelson, 2009), building habitats like the globally distributed rhodolith (or maërl) beds (Foster, 2001), and the large algal bioconstructions that abound in the Mediterranean (coralligenous assemblages, intertidal rims; Ingrosso et al., 2018). In addition, the CaCO3 precipitation within cell walls leads to a high fossilization potential of CA, which are considered the best fossil record among macrobenthic autotrophs since they first appeared in the Lower Cretaceous (Aguirre et al., 2000). It also makes CA major carbonate producers (van der Heijden and Kamenos, 2015), which, considering their abundance and wide distribution, gives them an important role in oceanic carbon cycling and reef building (Adey, 1998; Chisholm, 2003; Martin et al., 2006; Perry et al., 2008) and makes them a group of significant economic interest (Coletti and Frixa, 2017). Like many other marine ecosystems, CA habitats will be negatively affected by future climate change, e.g., due to reduced CA calcification/growth (Martin andHall-Spencer, 2017; Cornwall et al., 2019) that may eventually lead to ecosystem degradation and reduction of habitat complexity and biodiversity.
- Effects of ocean warming and pollution on Sargassum forestsPublication . Peres, Letícia M. Costa; Gouvêa, Lidiane; Hayden, Juliana; Burle, Giulia; Bastos, Eduardo; Carneiro, Alessandra; Horta, Paulo A.The combined effects of climate change and ocean pollution have resulted in a noteworthy decline of canopyforming species, impacting marine biodiversity and ecosystem functioning significantly. In this context, Sargassum cymosum, which is widely distributed along the southwestern Atlantic Ocean, serves as an excellent model among canopy-forming species to investigate these impacts on populations in different regions and environmental conditions. Here, we evaluate the ecophysiological responses of two populations of S. cymosum, from Florianopolis (warm-temperate province; WTP) and Fernando de Noronha (tropical province, TP), through of interaction of temperatures and nutrient concentrations, representing marine heatwaves and acute pollution levels. Our findings revealed a decrease in biomass in both populations, highlighting the significance of nutrient enrichment as an anthropogenic filter that might potentially inhibit the expansion of the populations from tropical regions and temperature for WTP ones. These stressors directly impacted the physiological performance of S. cymosum populations, including relative growth rates, photosynthesis, chlorophylls, carotenoids and phenolic compound levels. Although there was an increase in both parameters for the TP population, a significant loss of biomass was observed, with growth rates reaching -1.5% per day. Our results highlight the need for urgent actions to manage the eutrophication process due to its negative association with global warming, which can enhance the impacts and preclude the settlement and survival of Sargassum in warm-temperate areas considering the observed and predicted tropicalization process.
- Environmental drivers of rhodolith beds and epiphytes community along the South Western Atlantic coastPublication . Carvalho, Vanessa F.; Assis, Jorge; Serrao, Ester; Nunes, Jose M.; Anderson, Antonio B.; Batista, Manuela B.; Barufi, Jose B.; Silva, João; Pereira, Sonia M. B.; Horta, Paulo A.Environmental conditions shape the occurrence and abundance of habitat-building organisms at global scales. Rhodolith beds structure important hard substrate habitats for a large number of marine benthic organisms. These organisms can benefit local biodiversity levels, but also compete with rhodoliths for essential resources. Therefore, understanding the factors shaping the distribution of rhodoliths and their associated communities along entire distributional ranges is of much relevance for conservational biology, particularly in the scope of future environmental changes. Here we predict suitable habitat areas and identify the main environmental drivers of rhodoliths' variability and of associated epiphytes along a large-scale latitudinal gradient. Occurrence and abundance data were collected throughout the South-western Atlantic coast (SWA) and modelled against high resolution environmental predictors extracted from Bio-Oracle. The main drivers for rhodolith occurrence were light availability and temperature at the bottom of the ocean, while abundance was explained by nitrate, temperature and current velocity. Tropical regions showed the highest abundance of rhodoliths. No latitudinal pattern was detected in the variability of epiphytes abundance. However, significant differences were found between sampled sites regarding the composition of predominant taxa. The predictors influencing such differences were temperature and nitrate. The Tropical region is abundant in species with warm-water affinities, decreasing toward warm temperate region. The expressive occurrence of tropical species not referred before for warm temperate beds indicate a plausible tropicalization event.
- Global impacts of projected climate changes on the extent and aboveground biomass of mangrove forestsPublication . Gouvêa, Lidiane; A, Serrão; Cavanaugh, Kyle; Gurgel, Carlos F. D.; Horta, Paulo A.; Assis, JorgeAim: Over the past 50 years, anthropogenic activities have led to the disappearance of approximately one-third of the world's mangrove forests and their associated ecosystem services. The synergetic combined effect of projected climate change is likely to further impact mangroves in the years to come, whether by range expansions associated with warming at higher latitudes or large-scale diebacks linked to severe droughts. We provide an estimate of future changes in the extent and aboveground biomass (AGB) of mangrove forests at global scales by considering contrasting Representative Concentration Pathway scenarios (decade 2090-2100 under RCP 2.6 in line with the Paris Agreement expectations, and RCP 8.5 of higher emissions). Location: Global. Methods: Boosted regression trees fitted occurrence and AGB of mangroves against high-resolution biologically meaningful data on air temperature, precipitation, wave energy, slope and distance to river Deltas. Results: On the global scale, models produced for present-day conditions retrieved high accuracy scores and estimated a total area of 12,780,356 ha and overall biomass of 2.29 Pg, in line with previous estimates. Model projections showed poleward shifts along temperate regions, which translated into comparable gains in total area, regardless of the RCP scenario (area change RCP 2.6: 17.29%; RCP 8.5: 15.77%). However, biomass changes were dependent on the emission scenario considered, remaining stable or even increasing under RCP 2.6, or undergoing severe losses across tropical regions under RCP 8.5 (overall biomass change RCP 2.6: 12.97%; RCP 8.5: -11.51%). Such losses were particularly aggravated in countries located in the Tropical Atlantic and Eastern Pacific, and the Western and Eastern Indo-Pacific regions (regions with losses above similar to 20% in overall biomass). Conclusions: Our global estimates highlight the potential effect of future climate changes on mangrove forests and how broad compliance with the Paris Agreement may counteract severe trajectories of loss. The projections made, also provided at the country level, serve as new baselines to evaluate changes in mangrove carbon sequestration and ecosystem services, strongly supporting policy-making and management directives, as well as to guide restoration actions considering potential future changes in niche availability.
- Golden carbon of Sargassum forests revealed as an opportunity for climate change mitigationPublication . Gouvêa, Lidiane P.; Assis, Jorge; Gurgel, Carlos F. D.; A, Serrão; Silveira, Thiago C.L.; Santos, Rui; Duarte, Carlos M.; Peres, Leticia M. C.; Carvalho, Vanessa F.; Batista, Manuela; Bastos, Eduardo; Sissini, Marina N.; Horta, Paulo A.Marine climate change mitigation initiatives have recently attracted a great deal of interest in the role of natural carbon sinks, particularly on coastal systems. Brown seaweeds of the genus Sargassum are the largest canopyforming algae in tropical and subtropical environments, with a wide global distribution on rocky reefs and as floating stands. Because these algae present high amounts of biomass, we suggest their contribution is relevant for global carbon stocks and consequently for mitigating climate change as CO2 remover. We modelled global distributions and quantified carbon stocks as above-ground biomass (AGB) with machine learning algorithms and climate data. Sargassum AGB totaled 13.1 Pg C at the global scale, which is a significant amount of carbon, comparable to other key marine ecosystems, such as mangrove forests, salt marshes and seagrass meadows. However, specific techniques related to bloom production and management, or the utilization of biomass for biomaterials, should be fostered.
- Levelling-up rhodolith-bed science to address global-scale conservation challengesPublication . Tuya, Fernando; Schubert, Nadine; Aguirre, Julio; Basso, Daniela; Bastos, Eduardo O.; Berchez, Flávio; Bernardino, Angelo F.; Bosch, Néstor E.; Burdett, Heidi L.; Espino, Fernando; Fernández-Gárcia, Cindy; Francini-Filho, Ronaldo B.; Gagnon, Patrick; Hall-Spencer, Jason M.; Haroun, Ricardo; Hofmann, Laurie C.; Horta, Paulo A.; Kamenos, Nicholas A.; Le Gall, Line; Magris, Rafael A.; Martin, Sophie; Nelson, Wendy A.; Neves, Pedro; Olivé, Irene; Otero-Ferrer, Francisco; Peña, Viviana; Pereira-Filho, Guilherme H.; Ragazzola, Federica; Rebelo, Ana Cristina; Ribeiro, Cláudia; Rinde, Eli; Schoenrock, Kathryn; Silva, João; Sissini, Marina N.; Tâmega, Frederico T. S.Global marine conservation remains fractured by an imbalance in research efforts and policy actions, limiting progression towards sustainability. Rhodolith beds represent a prime example, as they have ecological importance on a global scale, provide a wealth of ecosystem functions and services, including biodiversity provision and potential climate change mit-igation, but remain disproportionately understudied, compared to other coastal ecosystems (tropical coral reefs, kelp for-ests, mangroves, seagrasses). Although rhodolith beds have gained some recognition, as important and sensitive habitats at national/regional levels during the last decade, there is still a notable lack of information and, consequently, specific conservation efforts. We argue that the lack of information about these habitats, and the significant ecosystem services they provide, is hindering the development of effective conservation measures and limiting wider marine conservation success. This is becoming a pressing issue, considering the multiple severe pressures and threats these habitats are exposed to (e.g., pollution, fishing activities, climate change), which may lead to an erosion of their ecological function and eco-system services. By synthesizing the current knowledge, we provide arguments to highlight the importance and urgency of levelling-up research efforts focused on rhodolith beds, combating rhodolith bed degradation and avoiding the loss of associated biodiversity, thus ensuring the sustainability of future conservation programs.
- Multi-level phenotypic plasticity and the persistence of seagrasses along environmental gradients in a subtropical lagoonPublication . Bercovich, Manuel Vivanco; Schubert, Nadine; Almeida Saa, Antonella C.; Silva, Joao; Horta, Paulo A.As seagrasses decline worldwide, determining their phenotypic variability in response to human altered environmental factors becomes important to better understand their acclimation strategies. Many studies have reported seagrass responses to environmental gradients of single parameters, using either single or multiple metrics. However, studies of species' phenotypic variations along environmental gradients that include several environmental factors are rather scarce. In this study, we evaluated and compared the responses of Halodule wrightii and Ruppia maritima at different organizational levels (meadow/shoot, leaf and biochemical level) to key environmental factors, such as urbanization, light availability, salinity and sediment characteristics in a subtropical Brazilian coastal lagoon. Both species tolerated the variable environmental conditions across the lagoon, but showed species-specific differences in the adjustments at certain organizational levels. Halodule wrightii, an opportunistic species, expressed phenotypic responses mostly at the meadows/shoot and biochemical level, while the colonizer R. maritima exhibited phenotypic variability mostly constrained to the biochemical level. Also, determinations on a few selected meadows showed species-specific photosynthetic responses to environmental conditions. These differences might be related to the species' life history, with R. maritima performing adjustments at organizational levels with a fast response time, while the longer life span of H. wrightii makes also investments in modifications at the shoot and meadow level useful. Thus, this study demonstrates differences in seagrass acclimation strategies in response to environmental variability and, as a first study in this region, it also provides useful baseline data that will allow detecting potential changes and/or deterioration of the habitat.