Abstract
AbstractSeagrasses are marine flowering plants that have important roles in the ecological and physical processes of many coastal areas. Seagrass modeling to date has mostly assumed that seagrasses have uniform biomechanical traits in space and time. In this study we compare the biomechanical traits of Zostera marina blades collected in late summer and spring from a lagoon in southern Denmark. Then, we describe how biomechanics vary depending on (i) seasonality, (ii) storage in laboratory conditions with high nutrient levels, (iii) blade rank and (iv) position along blades. The data collected with these direct measurements are fed into a numerical structural model that simulates seagrass response to an idealized flow and accounts for plant nonuniformity. The model is used to assess the effects of temporal variability and within‐plant heterogeneity in blade biomechanics on flow‐seagrass interactions. Results show that seagrass biomechanics are affected considerably by seasonality and laboratory storage. This biomechanical variability has a key role in defining flow‐seagrass interactions, enhancing light availability in summer and reducing potential drag force in spring. Significant within‐plant heterogeneity associated with both blade rank and along‐blade position is reported. Compared to temporal variability, within‐plant heterogeneity has a secondary role in determining flow‐seagrass interactions; however, blade rank is associated with a consistent reduction in the drag force. The results presented improve the understanding of flow‐seagrass interactions by clarifying the importance of variations in seagrass blade biomechanical traits and their origin.
Highlights
Seagrasses are foundation species of many coastal areas worldwide
The factors we considered in the present study are: (1) temporal variability associated with laboratory conditions with high nutrient levels; (2) temporal variability associated with seasonality; (3) within-plant heterogeneity associated with blade rank; and (4) within-plant heterogeneity associated with the position along blades
Biomechanical traits were measured from seagrass shoots collected in late summer and early spring, they were used to parameterize the numerical model of flow-seagrass interactions
Summary
Seagrasses are foundation species of many coastal areas worldwide. They provide a variety of ecological services from which key economic value arises (Barbier et al, 2011). Seagrasses create habitats and shelter for benthic organisms and fish, supply food for higher animals (Bakker et al, 2016) and help reducing the number of potential pathogens of marine species and humans (Lamb et al, 2017). They provide a considerable contribution to carbon sequestration (e.g., Duarte et al, 2013) through burial of organic carbon, with an estimated global burial rate of 48–112 Tg C/yr (Mcleod et al, 2011). Seagrasses have attracted research from several disciplines, but there remains the need to understand how their important physical and ecological roles arise from their biomechanical traits
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