Browsing by Author "Bouma, Tjeerd J."
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- Acclimation of seagrass Zostera noltii to co-occurring hydrodynamic and light stressesPublication . de los Santos, Carmen B.; Brun, Fernando G.; Bouma, Tjeerd J.; Vergara, Juan J.; Pérez-Lloréns, J. LucasSeagrasses may frequently experience a combination of velocity and light stresses, as elevated hydrodynamics often enhances turbidity and the subsequent light reduction. The objective of this study was to investigate the effects that these stressors induce on morphometric and dynamic seagrass features depending on the initial biomass partitioning. For this purpose, a factorial mesocosm experiment was conducted on plants of Zostera noltii subjected to combinations of 2 contrasting light levels (2.5 ± 0.6 and 15.6 ± 2.5 mol photons m–2 d–1) and 3 unidirectional flow velocities (0.35, 0.10 and 0.01 m s–1). No interactive effects between the 2 variables were recorded, except on plant survival and leaf length, and generally, light effects prevailed over hydrodynamic ones. Plants responded to light reduction regardless of the flow velocity treatments, showing low survival rates (which improved at high velocity), high aboveground/belowground biomass ratios (AG/BG) and a poorly developed root-rhizome system compared to plants under saturating light conditions. Plant morphometry only responded to hydrodynamic stress under saturating light: at high current velocity, plants preferentially allocated biomass into BG structures, bearing short leaves and displaying high internode and root appearance rates. Overall, light reduction promoted similar responses in plants with different AG/BG biomass ratios, but dissimilarities were recorded for current velocity. Thus, it can be concluded that, under simultaneous light and hydrodynamic stresses, light effects prevailed over hydrodynamic ones in Z. noltii, while acclimation to hydrodynamics only occurred under saturating light
- Biomechanical response of two fast-growing tropical seagrass species subjected to in situ shading and sediment fertilizationPublication . La Nafie, Yayu A.; de los Santos, Carmen B.; Brun, Fernando G.; Mashoreng, Supriadi; van Katwijk, Marieke M.; Bouma, Tjeerd J.Although seagrasses experience strong hydrodynamic forces, little is known about their biomechanical response in spite of the potential importance for their ecological success. We investigated how light reduction and sediment-nutrient enrichment affect biomechanical and morphological properties of two short-lived tropical seagrass species: Halophila ovalis and Halodule uninervis. A 50-day manipulative field experiment of shading and sediment-nutrient enrichment versus a natural population (control) showed that both shading and nutrient enrichment made the leaves of Halophila ovalis weaker (lower FTS) and more elastic (lower ET). As the absolute breakability of leaves (FMAX) was not affected by either of the treatments, this implies that these changes in strength and stiffness resulted from the increase in leaf dimensions under nutrient enrichment (i.e., longer, wider and thicker leaves) and shading conditions (i.e., thicker leaves). In contrast, the biomechanical properties of H. uninervis leaves were less responsive and only became more extensible under shading while their biomechanics did not change under sediment nutrient enrichment. This limited response of H. uninervis might be due to the lack of morphological response in this species since leaves only became longer under nutrient enrichment. When comparing both species across treatments under shading (after normalizing them with their controls), H. ovalis became significantly weaker compared to H. uninervis, and the latter became more extensible. Under nutrient enrichment, H. ovalis became significantly more elastic compared H. uninervis. Overall we found that (i) biomechanical properties can be affected by environmental conditions, (ii) the responses were species specific, and (iii) seagrass morphology (leaf thickness and width) affected by environmental conditions will influence seagrass biomechanical properties. Further experimental studies on seagrass biomechanics are needed as present understandings of the acclimation of these properties and the consequences for species functioning are only starting to emerge.
- A comprehensive analysis of mechanical and morphological traits in temperate and tropical seagrass speciesPublication . de los Santos, Carmen B.; Onoda, Yusuke; Vergara, J.J.; Pérez-Lloréns, J. Lucas; Bouma, Tjeerd J.; La Nafie, Yayu A.; Cambridge, Marion L.; Brun, Fernando G.Knowledge of plant mechanical traits is important in understanding how plants resist abiotic and biotic forces and in explaining ecological strategies such as leaf lifespan. To date, these traits have not been systematically evaluated in seagrasses. We analysed mechanical (breaking force and tensile strength) and associated traits (thickness, width, length, fibre content, mass area, and lifespan) of leaves in 22 seagrass species (around one-third of all known seagrass species) to examine (1) the inter-specific variation of these traits in relation to growth form and bioregions, (2) the contribution of morphology to leaf breaking force, (3) how breaking force scales to leaf dimensions, and (4) how mechanical and structural traits correlate to leaf longevity. We also compared our seagrass dataset with terrestrial plant databases to examine similarities between them. Large variation in leaf breaking force was found among seagrass species but, on average, temperate species resisted higher forces than tropical species. Variation in leaf breaking force was largely explained by differences in leaf width rather than thickness, likely due to the benefits in leaf reconfiguration and light interception. Species of large dimensions (long leaves) typically had high leaf breaking force, plausibly to tolerate the drag forces they may experience, which are proportional to the leaf area. Leaves of long-lived species typically had high mass per leaf area and fibre content and they supported high breaking forces. Compared to terrestrial plants, seagrasses are short-lived species with moderately strong fibre-reinforced leaves, which probably evolved to withstand the hydrodynamic forces occurring in the sea, and in response to other environmental factors. Overall, our analysis provides new insights into the physical performance of seagrasses in the marine environment.
- Global dataset of soil organic carbon in tidal marshesPublication . Maxwell, Tania L.; Rovai, André S.; Adame, Maria Fernanda; Adams, Janine B.; Álvarez-Rogel, José; Austin, William E. N.; Beasy, Kim; Boscutti, Francesco; Böttcher, Michael E.; Bouma, Tjeerd J.; Bulmer, Richard H.; Burden, Annette; Burke, Shannon A.; Camacho, Saritta; Chaudhary, Doongar R.; Chmura, Gail L.; Copertino, Margareth; Cott, Grace M.; Craft, Christopher; Day, John; de los Santos, Carmen B.; Denis, Lionel; Ding, Weixin; Ellison, Joanna C.; Ewers Lewis, Carolyn J.; Giani, Luise; Gispert, Maria; Gontharet, Swanne; González-Pérez, José A.; González-Alcaraz, M. Nazaret; Gorham, Connor; Graversen, Anna Elizabeth L.; Grey, Anthony; Guerra, Roberta; He, Qiang; Holmquist, James R.; Jones, Alice R.; Juanes, José A.; Kelleher, Brian P.; Kohfeld, Karen E.; Krause-Jensen, Dorte; Lafratta, Anna; Lavery, Paul S.; Laws, Edward A.; Leiva-Dueñas, Carmen; Loh, Pei Sun; Lovelock, Catherine E.; Lundquist, Carolyn J.; Macreadie, Peter I.; Mazarrasa, Inés; Megonigal, J. Patrick; Neto, Joao M.; Nogueira, Juliana; Osland, Michael J.; Pagès, Jordi F.; Perera, Nipuni; Pfeiffer, Eva-Maria; Pollmann, Thomas; Raw, Jacqueline L.; Recio, María; Ruiz-Fernández, Ana Carolina; Russell, Sophie K.; Rybczyk, John M.; Sammul, Marek; Sanders, Christian; Santos, Rui; Serrano, Oscar; Siewert, Matthias; Smeaton, Craig; Song, Zhaoliang; Trasar-Cepeda, Carmen; Twilley, Robert R.; Van de Broek, Marijn; Vitti, Stefano; Antisari, Livia Vittori; Voltz, Baptiste; Wails, Christy N.; Ward, Raymond D.; Ward, Melissa; Wolfe, Jaxine; Yang, Renmin; Zubrzycki, Sebastian; Landis, Emily; Smart, Lindsey; Spalding, Mark; Worthington, Thomas A.Tidal marshes store large amounts of organic carbon in their soils. Field data quantifying soil organic carbon (SOC) stocks provide an important resource for researchers, natural resource managers, and policy-makers working towards the protection, restoration, and valuation of these ecosystems. We collated a global dataset of tidal marsh soil organic carbon (MarSOC) from 99 studies that includes location, soil depth, site name, dry bulk density, SOC, and/or soil organic matter (SOM). The MarSOC dataset includes 17,454 data points from 2,329 unique locations, and 29 countries. We generated a general transfer function for the conversion of SOM to SOC. Using this data we estimated a median (+/- median absolute deviation) value of 79.2 +/- 38.1 Mg SOC ha-1 in the top 30 cm and 231 +/- 134 Mg SOC ha-1 in the top 1 m of tidal marsh soils globally. This data can serve as a basis for future work, and may contribute to incorporation of tidal marsh ecosystems into climate change mitigation and adaptation strategies and policies.
- Harnessing positive species interactions as a tool against climate-driven loss of coastal biodiversityPublication . Bulleri, Fabio; Eriksson, Britas Klemens; Queiros, Ana; Airoldi, Laura; Arenas, Francisco; Arvanitidis, Christos; Bouma, Tjeerd J.; Crowe, Tasman P.; Davoult, Dominique; Guizien, Katell; Ivesa, Ljiljana; Jenkins, Stuart R.; Michalet, Richard; Olabarria, Celia; Procaccini, Gabriele; Serrao, Ester; Wahl, Martin; Benedetti-Cecchi, LisandroHabitat-forming species sustain biodiversity and ecosystem functioning in harsh environments through the amelioration of physical stress. Nonetheless, their role in shaping patterns of species distribution under future climate scenarios is generally overlooked. Focusing on coastal systems, we assess how habitat-forming species can influence the ability of stress-sensitive species to exhibit plastic responses, adapt to novel environmental conditions, or track suitable climates. Here, we argue that habitat-former populations could be managed as a nature-based solution against climate-driven loss of biodiversity. Drawing from different ecological and biological disciplines, we identify a series of actions to sustain the resilience of marine habitat-forming species to climate change, as well as their effectiveness and reliability in rescuing stress-sensitive species from increasingly adverse environmental conditions.
- Leaf-fracture properties correlated with nutritional traits in nine Australian seagrass species: implications for susceptibility to herbivoryPublication . de los Santos, Carmen B.; Brun, F. G.; Onoda, Yusuke; Cambridge, Marion L.; Bouma, Tjeerd J.; Vergara, Juan J.Seagrasses are exposed to the constant risk of structural damage due to abiotic factors, such as waves and currents, and biotic factors, e.g. herbivory. Leaf mechanical resistance is therefore essential in protecting plants from structural failure and may also have ecological consequences. For example, mechanical traits of seagrass leaves may play an important role in plant− herbivore interactions and food-preferences of herbivores in these ecosystems, as widely reported for terrestrial plants. However, little is known about leaf mechanical resistance against structural damage in seagrasses and how it varies with other traits such as their nutritional value. We analysed the correlation between fracture properties relevant to herbivory and the nutritional value of seagrass leaves, testing the general assumption that species that invest heavily in mechanical resistance (toughening of the leaves) will present low nitrogen and high carbon and fibre contents. Direct measurements of leaf traits were conducted on 9 seagrass species from south-western Australia: (1) leaf-fracture properties from shearing and tearing tests, (2) nutritional values (carbon to nitrogen ratio and fibre content) and (3) morphological and structural traits (specific leaf area and leaf thickness). Results showed that leaf-fracture properties in seagrasses were tightly correlated to their C:N ratio, which reflects their nutritional value, thus supporting the general assumption that C investment is inversely correlated to N content. This close correlation suggested that patterns of seagrass consumption may be influenced not only by the C:N ratio but also by the leaf-fracture properties. Among co-existing seagrasses, we found a continuous spectrum of mechanical and nutritional traits across species, which provides fundamental information about species assembly, herbivore behaviour and ecosystem functions.
- Ontogenic variation and effect of collection procedure on leaf biomechanical properties of Mediterranean seagrass Posidonia oceanica (L.) DelilePublication . de los Santos, Carmen B.; Vicencio-Rammsy, Bárbara; Lepoint, Gilles; Remy, François; Bouma, Tjeerd J.; Gobert, SylvieLeaf mechanical traits are important to understand how aquatic plants fracture and deform when subjected to abiotic (currents or waves) or biotic (herbivory attack) mechanical forces. The likely occurrence of variation during leaf ontogeny in these traits may thus have implications for hydrodynamic performance and vulnerability to herbivory damage, and may be associated with changes in morphologic and chemical traits. Seagrasses, marine flowering plants, consist of shoot bundles holding several leaves with different developmental stages, in which outer older leaves protect inner younger leaves. In this study we examined the long-lived seagrass Posidonia oceanica to determine ontogenic variation in mechanical traits across leaf position within a shoot, representing different developmental stages. Moreover, we investigated whether or not the collection procedure (classical uprooted shoot versus non-destructive shoot method: cutting the shoot without a portion of rhizome) and time span after collection influence mechanical measurements. Neither collection procedure nor time elapsed within 48 h of collection affected measurements of leaf biomechanical traits when seagrass shoots were kept moist in dark cool conditions. Ontogenic variation in mechanical traits in P. oceanica leaves over intermediate and adult developmental stages was observed: leaves weakened and lost stiffness with aging, while midaged leaves (the longest and thickest ones) were able to withstand higher breaking forces. In addition, younger leaves had higher nitrogen content and lower fiber content than older leaves. The observed patterns may explain fine-scale within-shoot ecological processes of leaves at different developmental stages, such as leaf shedding and herbivory consumption in P. oceanica.
- Waves and high nutrient loads jointly decrease survival and separately affect morphological and biomechanical properties in the seagrassZostera noltiiPublication . La Nafie, Yayu A.; de los Santos, Carmen B.; Brun, Fernando G.; van Katwijk, Marieke M.; Bouma, Tjeerd J.In an 8-week aquarium experiment, we investigated the interactive effects of waves (present vs. absent) and water-column nutrient level (high vs. low) on the survival, growth, morphology, and biomechanics of the seagrass, Zostera noltii. Survival was reduced when plants were exposed to both waves and high nutrient levels. Wave and nutrient interaction significantly reduced aboveground biomass and leaf lengths, whereas waves independently reduced growth rate, internode abundance, elongation, and appearance rates. Nutrient supply significantly reduced the strength of the leaves. Wave and nutrient interaction was the main driving force affecting survival and morphological properties of seagrass, whereas dynamical characteristics were independently affected by waves, and nutrient supply affected mainly biomechanical properties. In conclusion, this experiment revealed that the combination of exposure to waves and high nutrient levels was detrimental for Z. noltii, which indicates that this could be an important unexplored force involved in seagrass declines.