Outputs

Carreiras et al 2021

Land salinization, resulting from the ongoing climate change phenomena, is having an increasing impact on coastal ecosystems like salt marshes. Although halophyte species can live and thrive in high salinities, they experience differences in their salt tolerance range, being this a determining factor in the plant distribution and frequency throughout marshes. Furthermore, intraspecific variation to NaCl response is observed in high-ranging halophyte species at a population level. The present study aims to determine if the environmental history, namely heavy metal preconditioning, can have a meaningful influence on salinity tolerance mechanisms of Spartina patens, a highly disperse grass invader in the Mediterranean marshes. For this purpose, individuals from pristine and heavy metal contaminated marsh populations were exposed to a high-ranging salinity gradient, and their intraspecific biophysical and biochemical feedbacks were analyzed. When comparing the tolerance mechanisms of both populations, S. patens from the contaminated marsh appeared to be more resilient and tolerant to salt stress, this was particularly present at the high salinities. Consequently, as the salinity increases in the environment, the heavy metal contaminated marsh may experience a more resilient and better adapted S. patens community. Therefore, the heavy metal pre-conditioning of salt mash populations appears to be able to create intraspecific physiological variations at the population level that can have a great influence on marsh plant distribution outcome.

Carvalho et al 2021

The invasion of natural communities by non-indigenous species represents one of the most serious threats to biodiversity. Understanding the ecophysiology of invasive species can provide insights into potential physiological handicaps relative to native species. By doing so, we can leverage the development of ecoengineering solutions for the removal of non-indigenous species, preferably using non-chemical methods. Spartina patens is a known invasive species of cordgrass aggressively proliferating in Mediterranean salt marshes, producing impenetrable monospecific stands. As its occurrence is delimited by the upper high tide water level, we hypothesized that S. patens is intolerant to waterlogging. Therefore, we developed a field experimente where strands of S. patens were kept waterlogged over the entire tidal cycle for 30 days. At the end of the experimental period, plants in the trial plots exhibited severe stress symptoms at different physiological levels compared with control plots (no intervention). At the photobiological level, intervened plants exhibited lower efficiency in producing chemical energy from light, whilst at the biochemical level waterlogging impaired the antioxidant system and increased lipid peroxidation products. Furthermore, the application of chlorophyll a pulse amplitude modulated (PAM) fluorometry, a non-invasive technique, allowed us to evaluate the effectiveness of the implemented measures, being the tool that provided the best separation between the control and intervened population. Considering the physiological traits observed here, ecoengineering solutions based on increased waterlogging of S. patens stands, can be a low-cost and efficient measure to reduce the spreading and growth of this invasive species in the Mediterranean and other salt marshes worldwide with little disturbance.

Borges et al 2021

Coastal areas host some of the planet’s most productive ecosystems, providing life sustaining ecological services and several benefits to humankind, while also being some of the most threatened areas (e.g., by globalization, climate change, and biological invasion). Salt marshes are coastal habitats with a key role in food and shelter provisioning, sediment deposition, nutrient cycling and carbon storage. Spartina spp. is a genus of grass halophytes which occurs in salt marshes worldwide, and includes species with different invasive potential. We evaluated the effect of climate change in the distribution and invasion potential of five Spartina species (S. anglica, S. alterniflora, S. densiflora, S. patens, and S. maritima) at a global scale. Species distribution models (SDMs) were applied on species occurrence data and atmospheric environmental predictors (WorldClim 2.1) to project potential changes in habitat suitability and associated changes in distribution and species co-occurrence until the end of the century, across four Shared Socioeconomic Pathway scenarios (i.e., SSP1-2.6 to SSP5-8.5). Projections showed a global trend for increasing species co-occurrence, with a general range expansion potentiated by increasing pathway severity. This study suggests that Spartina species can potentially benefit from climate change, predicting
poleward expansions in the Northern Hemisphere for most species, with results pointing at increased conflict and invasion potential in Northern Europe and East Asian shorelines, already under strong invasive pressure. S. anglica is projected to remain a successful invader, with more severe scenarios likely favoring greater expansions. S. alterniflora exhibits very low expansion comparatively, despite exhibiting the same
northward distribution shift. SSP1-2.6 produced the smallest change to species cooccurrence, suggesting a smaller potential for invasion-related conflicts, although still registering a potential net expansion for the Genus. Despite their limitations, SDMs can help establish general trends in climate change ecology and inform policymakers and environmental agents to ensure the correct management of these habitats and, ultimately, ecosystems.

Duarte et al 2021

Salt marshes are valuable ecosystems, as they provide food, shelter, and important nursery areas for fish and macroinvertebrates, and a wide variety of ecosystem services for human populations. These ecosystem services heavily rely on the floristic composition of the salt marshes with different species conferring different service values and different adaptation and resilience capacities towards ecosystem stressors. Blue carbon, nitrogen, and phosphorous stocks are no exception to this, and rely on the interspecific differences in the primary production metabolism and physiological traits. Furthermore, these intrinsic physiological characteristics also modulate the species response to any environmental stressor, such as the ones derived from ongoing global changes. This will heavily shape transitional ecosystem services, with significant changes of the ecosystem value of the salt marshes in terms of cultural, provisioning, regulating, and supporting ecosystem services, with a special emphasis on the possible alterations of the blue carbon, nitrogen, and phosphorous stocks retained in these key environments. Thus, the need to integrate plant physiological characteristics and feedbacks towards the expected climate change‐driven stressors becomes evident to accurately estimate the ecosystem services of the salt marsh community, and transfer these fundamental services into economic assets, for a fluid communication of the ecosystems value to stakeholders, decision and policy makers, and environmental management entities.

Bortolus et al 2019

In 2014, a DNA-based phylogenetic study confirming the paraphyly of the grass subtribe Sporobolinae proposed the creation of a large monophyletic genus Sporobolus, including (among others) species previously included in the genera Spartina, Calamovilfa, and Sporobolus. Spartina species have contributed substantially (and continue contributing) to our knowledge in multiple disciplines, including ecology, evolutionary biology, molecular biology, biogeography, experimental ecology, biological invasions, environmental management, restoration ecology, history, economics, and sociology. There is no rationale so compelling to subsume the name Spartina as a subgenus that could rival the striking, global iconic history and use of the name Spartina for over 200 yr. We do not agree with the subjective arguments underlying the proposal to change Spartina to Sporobolus. We understand the importance of both the objective phylogenetic insights and of the subjective formalized nomenclature and hope that by opening this debate we will encourage positive feedback that will strengthen taxonomic decisions with an interdisciplinary perspective. We consider that the strongly distinct, monophyletic clade Spartina should simply and efficiently be treated as the genus Spartina.

Human et al 2020

Within the Tejo Estuary, non-indigenous species (NIS) Spartina patens colonizes the upper middle marsh competing with the native Halimione portulacoides for space and resources. Due to the very different root system and metabolism between both species, this invasion can have significant biogeochemical implications, namely in terms of metal speciation and availability. In the present study, we evaluate the biogeochemical modifications in terms of metal speciation introduced by the colonization of the NIS S. patens. Total metals Cu, Zn, Pb and As within the rhizosediment varied between the two study species but was generally higher in the rhizosediment of H. portulacoides. These differences could be attributed to the higher organic content and smaller sand fraction found in the rhizosediment of H. portulacoides. Zinc was found to have highest concentration in the rhizosediments while Cu and As were least concentrated metals.
Considering the bioavailable fractions (F1 and F2) Cu, Zn and As were more readily available in the sediment beneath NIS S. patens than in H. portulacoides and Pb presented no significance. Overall, H. portulacoides rhizosediments had higher total metal concentration, whilst the rhizosediments of NIS S. patens presented a higher percentage of bioavailable metals. Thus, the bioinvasion and expansion of NIS S. patens may have implications for metal biogeochemistry and the natural remediation capacity of salt marshes in estuaries along the Mediterranean and North-eastern Atlantic coasts, as well as ensuing biodiversity and potential trophic web contamination consequences.

Carreiras et al 2020

Salt marshes are worldwide recognized for their unique and important ecological role. According to the Intergovernmental Panel on Climatic Change (IPCC), the frequency and intensity of warming events will rise due to global changes. Halophyte plants, inhabiting salt marshes are known for being highly tolerant to various abiotic stresses, nonetheless, although it has been acknowledged that the tolerance response is species specific there could also be differences at the population level. The present work aims to determine if the life history of two halophytes (Halimione portulacoides and Spartina patens), namely in terms of contaminant exposure, influences inter-populational heat tolerance. For this purpose, individuals from both species collected at pristine and contaminated sites were exposed to normal and increased temperature conditions, and its physiological fitness evaluated throughout biochemical and biophysical analysis. The photobiological traits, pigment and fatty acid profiles and oxidative stress biomarkers analyses of warming treated individuals, indicate that chronic heavy metal pre-conditioning significantly influences the heat stress tolerance of the native halophyte plants. Halimione portulacoides individuals collected at heavy metal contaminated salt marsh appeared more tolerant to heat stress. On the other hand, the invasive S. patens from the pristine site showed higher tolerance to heat stress. Thus, the pre-conditioning influences the tolerance mechanisms can affect the way in which salt marsh communities will evolve in the future, possibly being different through salt marshes. The contaminated marsh can be more resilient to invasion than the non-contaminated marsh, since the native species has benefited from this pre-conditioning. Moreover, and from the ecophysiological point the set of biophysical and biochemical indicators were tested, show a high efficiency in describing the ecophysiological traits, both between species and populations, facing different pre-conditioning histories.

Fonseca et al 2019

Estuaries are renown sinks or repositories of contaminants and reflect historical pollution of persistent compounds. In particular, mercury (Hg) contamination is widespread in coastal environments and occurs in both inorganic (THg) and highly toxic organic forms (OHg) with high bioaccumulation potential. Trophic magnification factors have been increasingly used to quantify biomagnification and represent the average rate of change in contaminant concentration throughout a food web. Here, we assessed small scale
spatial variation in THg and OHg concentrations, as well as variations in local trophic magnification factors in three segregated areas of the Tejo estuary. Selected sites covered a gradient of contamination from industrial Hg hotspots to a natural reserve area, and are key nursery areas for multiple fishes. We analyzed concentrations in sediment and biota, representing the entire local food webs. Samples included sediments, primary producers (salt marsh plants), primary consumers (microbenthic invertebrates) and top consumers (fish muscle and liver), and the trophic web structure was characterized via SIAR mixed-modeling of nitrogen and carbon isotopic ratios. Spatial variation in Hg concentrations was observed in sediment and biota (but not for all species), with highest concentrations in the area near historical mercury input. Hg concentrations increased with trophic level, and so did the OHg fraction (% of OHg relative to THg), with mean maximum values up to 48.7 and 94.9% in invertebrates and fish, respectively. Trophic magnification factors were positive for all sites (p < 0.05 for all regressions), ranging between 1.56 to 1.76 and 1.78 to 2.47 for THg and OHg, respectively. Overall, rates of mercury bioaccumulation were similar across sites with variations in biota Hg concentrations reflecting baseline differences in site environmental levels. Understanding mercury bioaccumulation and magnification in estuarine biota is critical to safeguard the multiple ecologic functions and economic benefits estuaries provide.

Duarte et al 2018

The invasion of natural communities by non-indigenous species (NIS) represents one of the most serious threats to biodiversity. While these invasive processes are rather well studied in river corridors and riparian communities, the invasiveness of non-indigenous aquatic plants in wetlands has received far less attention. Many NIS plants have been introduced more than 100 years ago, while others are more recent arrivals, with most of the introductions occurring at the end of the 19th and at the beginning of the 20th centuries. The Spartina genus (the cordgrasses) is one of the most successful among halophytes (species that can survive and complete their life cycle under saline conditions), being present in a wide range of latitudes across the globe. Typically, Mediterranean systems are inhabited by the endemic small cordgrass Spartina maritima, native from the Atlantic African and European Atlantic coasts. Alongside, and with very similar geographical distribution ranges, two invasive species from the Spartina genus have been detected in Mediterranean systems. Spartina versicolor was first described in the Mediterranean region during the 19th century. This taxon is considered to be originated in America, and was introduced to Europe in the 19th century. It is probable that this species was introduced as packing material in crates to various ports around the Mediterranean Sea. Denseflower cordgrass Spartina densiflora is an invasive grass species of South American origin that has colonized salt marshes in the Gulf of Cadiz in the southwestern Iberian Peninsula,
Africa and North America. This is a facultative halophyte species (plants that avoid the effects of high salt even though they live in a saline environment) with an amazing physiological and morphological flexibility, enabling it to cope with a very wide range of environment constraints (salinity, tidal submergence, soil types, drainage and nutrient availability). Having this knowledge in mind becomes important to review the history of the introduction of these NIS along with their current colonization status and physiological characteristics. In the present chapter, this approach will be integrated with future scenarios of global change and increased anthropogenic pressures to achieve a better understanding of the impact of these NIS in Mediterranean estuarine systems.

Baumel et al 2016

Intercontinental introductions are widespread in the genus Spartina, with important ecological and evolutionary consequences. The native or introduced status of Spartina species is then critical with regard to biodiversity assessment, especially for vulnerable Mediterranean coastline ecosystems. Spartina versicolor was first recorded in southern France in 1849, then successively in various places on the European and North-African Mediterranean and Atlantic coasts. This species is considered to be either a European native or an invasive species introduced from North America which has a high morphological similarity to the Atlantic American species Spartina patens. We performed extensive sampling of S. versicolor in Europe and North Africa (from natural populations and herbarium collections) and compared
these samples to other European and American Spartina species (including S. patens). Chromosome counts were reported for the first time and revealed that S. versicolor is tetraploid (2n = 4x = 40). Phylogenetic analyses based on chloroplast and nuclear ribosomal DNA sequences did not reveal any molecular variation within S. versicolor. In this species, a single haplotype, that is identical to one haplotype of S. patens, was found in the four chloroplast and the nuclear ribosomal ITS regions investigated. In addition, simple sequence repeat markers were used and revealed a low level of genetic diversity within S. versicolor, suggesting that the introduction of S. versicolor occurred from a narrow genetic pool of S. patens from North America.

Duarte et al 2016

The recent IPCC WG2 5th Assessment Report (IPCC 2014), notes an increase in the frequency and duration of extreme climatic events, especially for the Mediterranean region. Together with climate change, the invasion of natural communities by non-indigenous species (NIS) constitutes a serious threat to biodiversity. One of these NIS is the American Spartina patens, now present in Western European marshes. The present study aims to understand the biochemical and photochemical responses of S. patens compared with S. maritima under extreme temperature events. Under normal and extreme heat conditions, S. patens had a higher photosynthetic efficiency (a), compared with coldwave events, where the native S. maritima was far more efficient. This reduced photosynthetic efficiency was mostly due to a decrease in the connectivity between photosystem II (PSII) antennae. This was accompanied by severe damage to the oxygen evolving complex of PSII. On the other hand, S. patens oxygen evolving complexes (OECs) seem to be temperature insensitive. The light absorption capacity was maintained due to a higher net rate of reaction centre (RC) closure as a counteractive measure of the reduced number of RC, especially in S. maritima. The loss of connectivity between PSII antennae and damage in OECs under heat stress leads to a severe reduction in the maximum yield for photochemistry enhanced by the low probability of each absorbed quanta to produce electronic work. However, while S. maritima presents high energy losses under heat stress, S. patens developed efficient quenching mechanisms under thermal stress, through auroxanthin. In S. patens, cold wave-treated individuals also displayed a very active line of enzymatic defences for reactive oxygen species scavenging. In fact, only cold treated individuals of this species presented higher activities of anti-oxidant enzymes, revealing some degree of adaptation to this new environment. In contrast, in S. maritima the exposure to extreme heat periods led, in most cases, to a decrease in the enzymatic defences, leaving the cell prone to oxidative damage. In summary, S. patens appears to have a higher fitness for the incoming climatic scenarios, being more tolerant to heat stress, while S. maritima will have its photobiological fitness decreased. This will impose a shift in the salt marsh biodiversity, favouring the non-indigenous S. patens expansion.

Duarte et 2015

Salt marshes are facing a new threat: the invasion by non-indigenous species (NIS), Although its introduction time is not established yet, in 1999 Spartina versicolor was already identified as a NIS in the Mediterranean marshes, significantly spreading its area of colonization. Using the Mediterranean native Spartina maritima as a reference, the present research studied the ecophysiological fitness of this NIS in its new environment, as a tool to understand its potential invasiveness. It was found that Spartina versicolor had a stable photobiological pattern, with only minor fluctuations during an annual cycle, and lower efficiencies comparated to S. maritima. The NIS seems to be rather insensitive to the observed abiotic factors fluctuations (salinity and pH of the sediment), and thus contrasts with the native S. maritima, known to be salinity dependent with higher productivity values in higher salinity environments. Most of the differences observed between the photobiology of these species could be explained by their nitrogen nutrition (here evaluated by the δ15N stable isotope) and directly related with the Mediterranean climate. Enhanced by a higher N availability during winter, the primary production of S. maritima which lead to dilution of the foliar δ15N concentration in the newly formed biomass, similarly to what is observed along a rainfall gradient. On the other hand, S. versicolor showed an increased δ15N in its tissues along the annual rainfall gradient, probably due to a δ15N concentration effect during low biomass production periods (winter and autumn). Together with the photobiological traits, these isotopic data point out to a climatic misfit of S. versicolor to the Mediterranean climate compared to the native S. maritima. This appears to be the major constrain shaping the ecophysiological fitness of this NIS, its primary production and consequently, its spreading rate along the Mediterranean marshes.

Metal induced cross-tolerance to abiotic stresses in halophytes

Climate change is having an increasing effect worldwide, causing weighty disturbances in virtually all ecosystems thru arising abiotic variations. Salt marshes ecosystems, although highly resilient, are no exception to the climate shift consequences. Considering halophyte communities resistence and tolerance to abiotic alterations, climate change still makes them vulnerable to dire consequences in their productivity, ending up upsetting the distribution and biodiversity of marsh vegetation, compromising their economic, social and ecological services and unique role as the "Kidneys of the planet". This project aimed to determine heavy metal cross-tolerance thru pre-conditioning to abiotic stresses in halophyte plants. Analyzing the influence that adaptations to local conditions have in tolerance and resistance mechanisms and if this will be relevant in the stress response to the abiotic variations predicted in the future climate change and what could this mean for the shifting ecosystems. For this, it was studied the physiological responses to abiotic stresses in two different populations of the wide spread halophyte species, the native C3 Halimione portulacoides and the invasive C4 Spartina patens, from nearby salt marshes in the Tagus estuary, with the major difference between them being heavy metal soil content. Firstly, on the basis that the frequency and intensity of warming events will rise, in duration and frequency, due to global warming, the halophyte plant groups where exposed to a warming event and then analyzed photobiologically and biochemically. The cross-tolerance results shown that heavy metal pre-condition enhanced the heat resistance mechanisms in H. portulacoides and worsened S. patens ability to cope with these changes, when compared to their non-pre-conditioned counterparts. This can have important consequences in the way the non-contaminated and heavy metal contaminated salt marshes will react to environmental changes, that can lead to possibly different ecological consequences. Considering the predicted climate change scenarios, it can be claimed that the contaminated marsh can be more resistant to invasion than the pristine marshes, were the warming events will benefit the exotic S. patens in relation to the native H. portulacoides. Secondly and taking in to consideration that land salinization is an increasing problem around the world and climate change will intensify this phenomenon especially in coastal lands, due to tidal surges, storm surges and sea level rise coupled with the increasing evaporation because of global warming, the halophyte species from both the studied salt marshes were exposed to a variety of salt treatments. When analyzed, the results exposed a noteworthy influence that the heavy metal pre-conditioned has in the salinity stress responses. In view of the future changes, it can be argued that heavy metal contaminated marshes are less resistant to the S. patens increasing colonization when exposed intermediate salt concentrations and in high salinities both H. portulacoides and S. patens have overall better salinity tolerance than their counterparts from the non-contaminated marsh. Concluding, this work shows that the heavy metal pre-conditioning has a complex and considerable influence in the plants tolerance and resistance mechanisms to several abiotic stresses, presenting an intraspecific physiological variation that can impact how the halophyte communities will respond to the upcoming environmental changes. According to our research it can be said that the heavy metal contaminated salt marsh will present significantly different ecological damages than their neighboring salt marsh.