Browsing by Author "Marba, Nuria"
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- Decreasing carbonate load of seagrass leaves with increasing latitudePublication . Mazarrasa, Ines; Marba, Nuria; Krause-Jensen, Dorte; Kennedy, Hilary; Santos, Rui; Lovelock, Catherine E.; Duarte, Carlos M.Seagrass meadows play a significant role in the formation of carbonate sediments, serving as a substrate for carbonate-producing epiphyte communities. The magnitude of the epiphyte load depends on plant structural and physiological parameters, related to the time available for epiphyte colonization. Yet, the carbonate accumulation is likely to also depend on the carbonate saturation state of seawater (Omega) that tends to decrease as latitude increases due to decreasing temperature and salinity. A decrease in carbonate accumulation with increasing latitude has already been demonstrated for other carbonate producing communities. The aim of this study was to assess whether there was any correlation between latitude and the epiphyte carbonate load and net carbonate production rate on seagrass leaves. Shoots from 8 different meadows of the Zostera genus distributed across a broad latitudinal range (27 degrees S to up to 64 degrees N) were sampled along with measurements of temperature and Omega. The Omega within meadows significantly decreased as latitude increased and temperature decreased. The mean carbonate content and load on seagrass leaves ranged from 17% DW to 36% DW and 0.4-2.3 mg CO3 cm(-2), respectively, and the associated mean carbonate net production rate varied from 0.007 to 0.9 mg CO3 cm(-2) d(-1). Mean carbonate load and net production rates decreased from subtropical and tropical, warmer regions towards subpolar latitudes, consistent with the decrease in Omega. These results point to a latitudinal variation in the contribution of seagrass to the accumulation of carbonates in their sediments which affect important processes occurring in seagrass meadows, such as nutrient cycling, carbon sequestration and sediment accretion.
- Differentiation in fitness-related traits in response to elevated temperatures between leading and trailing edge populations of marine macrophytesPublication . Mota, Catarina; Engelen, Aschwin; Serrao, Ester; Coelho, Márcio; Marba, Nuria; Krause-Jensen, Dorte; Pearson, GarethThe nature of species distribution boundaries is a key subject in ecology and evolution. Edge populations are potentially more exposed to climate-related environmental pressures. Despite research efforts, little is known about variability in fitness-related traits in leading (i.e., colder, high latitude) versus trailing (i.e., warmer, low latitude) edge populations. We tested whether the resilience, i.e. the resistance and recovery, of key traits differs between a distributional cold (Greenland) and warm (Portugal) range edge population of two foundation marine macrophytes, the intertidal macroalga Fucus vesiculosus and the subtidal seagrass Zostera marina. The resistance and recovery of edge populations to elevated seawater temperatures was compared under common experimental conditions using photosynthetic efficiency and expression of heat shock proteins (HSP). Cold and warm edge populations differed in their response, but this was species specific. The warm edge population of F. vesiculosus showed higher thermal resistance and recovery whereas the cold leading edge was less tolerant. The opposite was observed in Z. marina, with reduced recovery at the warm edge, while the cold edge was not markedly affected by warming. Our results confirm that differentiation of thermal stress responses can occur between leading and trailing edges, but such responses depend on local population traits and are thus not predictable just based on thermal pressures.
- Glacial vicariance drives phylogeographic diversification in the amphi-boreal kelp Saccharina latissimaPublication . MACHADO, JOÃO NEIVA; Paulino, Cristina; Nielsen, Mette M.; Krause-Jensen, Dorte; Saunders, Gary W.; Assis, Jorge; Barbara, Ignacio; Tamigneaux, Eric; Gouveia, Licínia; Aires, Tânia; Marba, Nuria; Bruhn, Annette; Pearson, Gareth; Serrao, Ester A.Glacial vicariance is regarded as one of the most prevalent drivers of phylogeographic structure and speciation among high-latitude organisms, but direct links between ice advances and range fragmentation have been more difficult to establish in marine than in terrestrial systems. Here we investigate the evolution of largely disjunct (and potentially reproductively isolated) phylogeographic lineages within the amphi-boreal kelp Saccharina latissima s.l. Using molecular data (COI, microsatellites) we confirm that S. latissima comprises also the NE Pacific S. cichorioides complex and is composed of divergent lineages with limited range overlap and genetic admixture. Only a few genetic hybrids were detected throughout a Canadian Arctic/NW Greenland contact zone. The degree of genetic differentiation and sympatric isolation of phylogroups suggest that S. latissima s.l. represents a complex of incipient species. Phylogroup distributions compared with paleo-environmental reconstructions of the cryosphere further suggest that diversification within S. latissima results from chronic glacial isolation in disjunct persistence areas intercalated with ephemeral interglacial poleward expansions and admixture at high-latitude (Arctic) contact zones. This study thus supports a role for glaciations not just in redistributing pre-existing marine lineages but also as a speciation pump across multi-glacial cycles for marine organisms otherwise exhibiting cosmopolite amphi-boreal distributions.
- Global analysis of seagrass restoration: the importance of large-scale plantingPublication . van Katwijk, Marieke M.; Thorhaug, Anitra; Marba, Nuria; Orth, Robert J.; Duarte, Carlos M.; Kendrick, Gary A.; Althuizen, Inge H. J.; Balestri, Elena; Bernard, Guillaume; Cambridge, Marion L.; Cunha, Alexandra; Durance, Cynthia; Giesen, Wim; Han, Qiuying; Hosokawa, Shinya; Kiswara, Wawan; Komatsu, Teruhisa; Lardicci, Claudio; Lee, Kun-Seop; Meinesz, Alexandre; Nakaoka, Masahiro; O'Brien, Katherine R.; Paling, Erik I.; Pickerell, Chris; Ransijn, Aryan M. A.; Verduin, Jennifer J.In coastal and estuarine systems, foundation species like seagrasses, mangroves, saltmarshes or corals provide important ecosystem services. Seagrasses are globally declining and their reintroduction has been shown to restore ecosystem functions. However, seagrass restoration is often challenging, given the dynamic and stressful environment that seagrasses often grow in. From our world-wide meta-analysis of seagrass restoration trials (1786 trials), we describe general features and best practice for seagrass restoration. We confirm that removal of threats is important prior to replanting. Reduced water quality (mainly eutrophication), and construction activities led to poorer restoration success than, for instance, dredging, local direct impact and natural causes. Proximity to and recovery of donor beds were positively correlated with trial performance. Planting techniques can influence restoration success. The meta-analysis shows that both trial survival and seagrass population growth rate in trials that survived are positively affected by the number of plants or seeds initially transplanted. This relationship between restoration scale and restoration success was not related to trial characteristics of the initial restoration. The majority of the seagrass restoration trials have been very small, which may explain the low overall trial survival rate (i.e. estimated 37%). Successful regrowth of the foundation seagrass species appears to require crossing a minimum threshold of reintroduced individuals. Our study provides the first global field evidence for the requirement of a critical mass for recovery, which may also hold for other foundation species showing strong positive feedback to a dynamic environment.Synthesis and applications. For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration.For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration.
- Marine forests of the Mediterranean-Atlantic Cystoseira tamariscifolia complex show a southern Iberian genetic hotspot and no reproductive isolation in parapatryPublication . Bermejo, Ricardo; Chefaoui, Rosa M.; Engelen, Aschwin H.; Buonomo, Roberto; Neiva, J.; Ferreira-Costa, Joana; Pearson, Gareth; Marba, Nuria; Duarte, Carlos M.; Airoldi, Laura; Hernandez, Ignacio; Guiry, Michael D.; Serrao, Ester A.Climate-driven range-shifts create evolutionary opportunities for allopatric divergence and subsequent contact, leading to genetic structuration and hybrid zones. We investigate how these processes influenced the evolution of a complex of three closely related Cystoseira spp., which are a key component of the Mediterranean-Atlantic seaweed forests that are undergoing population declines. The C. tamariscifolia complex, composed of C. tamariscifolia s.s., C. amentacea and C. mediterranea, have indistinct boundaries and natural hybridization is suspected. Our aims are to (1) infer the genetic structure and diversity of these species throughout their distribution ranges using microsatellite markers to identify ancient versus recent geographical populations, contact zones and reproductive barriers, and (2) hindcast past distributions using niche models to investigate the influence of past range shifts on genetic divergence at multiple spatial scales. Results supported a single, morphologically plastic species the genetic structure of which was incongruent with a priori species assignments. The low diversity and low singularity in northern European populations suggest recent colonization after the LGM. The southern Iberian genetic hotspot most likely results from the role of this area as a climatic refugium or a secondary contact zone between differentiated populations or both. We hypothesize that life-history traits (selfing, low dispersal) and prior colonization effects, rather than reproductive barriers, might explain the observed genetic discontinuities.