Restoring mussel beds on highly dynamic mudflats

Abstract

could potentially be a better donor source for intertidal transplantations, as young mussels may still possess a sufficiently high capacity for phenotypic plasticity, making them capable of acclimating to a new environment. This chapter focuses on the understanding of how mussels adjust to a new environment, and which environmental factors (e.g., exposure to the air and wave action) are driving these adjustments. This knowledge can prevent the transplantation of organisms with illadjusted phenotypes and ultimately increase the transplantation success. Chapter 3: Lowering environmental stressorsNewly transplanted mussels are highly vulnerable to dislodgement by hydrodynamic forces and to predation by crabs or shorebirds (Capelle et al., 2014). As a result, the establishment might require a "window of opportunity," defined as a specific disturbance-free period (Balke et al., 2011;Balke et al., 2013). Additional measures are often needed to artificially create such a window of opportunity on a highly dynamic coast, as the chances are very low for such moments to naturally occur at the same time and space as the restoration effort being executed. Engineering measures such as breakwaters or attachment substrates may be used to create a window of opportunity and kick-start establishment. In this chapter, we tested whether the environmental stress caused by a high predation pressure and wavedriven dislodgement could be reduced through a combination of artificial structures such as fences (to exclude predatory crabs), attachment substrates such as coir-net or oyster shells (to enhance attachment strength) and breakwaters (to reduce dragforces from waves). Overall, this study highlights the potential for using techniques that can lower multiple environmental stressors to create a window of opportunity for establishment in highly dynamic ecosystems. Chapter 4: Promoting self-facilitating feedback processesCoastal ecosystem engineers often depend on self-facilitating feedback processes to ameliorate environmental stress. This makes the restoration of such coastal ecosystem engineers difficult. On soft-bottom mudflats, mussels attach themselves to conspecifics and aggregate into distinctive patterns (van de Koppel et al., 2005a;Commito et al., 2014) to increase their resistance to dislodgement by hydrodynamic forces (Liu et al., 2014) and create a safety in numbers effect and reducing the chance of falling prey to predators (Cote & Jelnikar, 1999;Hunt & Scheibling, 2001). Recent studies emphasize the importance of integrating these kinds of positive intraspecific feedbacks to improve transplantation success (Silliman et al., 2015;Renzi et al., 2019;Valdez et al., 2020). However, large-scale and cost-effective restoration methods that consider positive feedback interactions, in addition to creating a window of opportunity for the establishment of target organisms, are still scarce. In this chapter, Chapter 2 Mussel seed is highly plastic to settling conditions: the influence of waves vs. tidal emergence