Are we ready for scaling up restoration actions? An insight from Mediterranean macroalgal canopies

Abstract

Extensive loss of macroalgal forests advocates for large-scale restoration interventions, to compensate habitat degradation and recover the associated ecological functions and services. Yet, restoration attempts have generally been limited to small spatial extensions, with the principal aim of developing efficient restoration techniques. Here, the success of outplanting Cystoseira amentacea v. stricta germlings cultured in aquaria was experimentally explored at a scale of tens of kms, by means of a multifactorial experimental design. In the intertidal rocky shores of SE Italy, locations with a continuous distribution for hundreds of meters or with few thalli forming patches of few centimeters of C. amentacea canopy were selected. In each location, the effects of adult conspecifics and the exclusion of macrograzers (salema fish and sea urchins) on the survival of germlings were tested. We evaluated the most critical determinants of mortality for germlings, including the overlooked pressure of mesograzers (e.g. amphipods, small mollusks, polychaetes). Despite the high mortality observed during outplanting and early settlement stages, survival of C. amentacea germlings was consistently favored by the exclusion of macrograzers, while the presence of adult conspecifics had no effects. In addition, the cost analysis of the interventions showed the feasibility of the ex-situ method, representing an essential tool for preserving Cystoseira forests. Large scale restoration is possible but requires baseline information with an in-depth knowledge of the species ecology and of the areas to be restored, together with the development of specific cultivation protocols to make consistently efficient restoration interventions.

Effects of Natural and Anthropogenic Stressors on Fucalean Brown Seaweeds Across Different Spatial Scales in the Mediterranean Sea

“…When fucalean populations are reduced or become locally extinct, their natural recovery is almost impossible, primarily due to their slow growth and the low dispersal abilities of their large and heavy zygotes (Orfanidis, 1991;Ballesteros et al, 2009;Buonomo et al, 2017;Bermejo et al, 2018). Although restoration by transplantation or recruitment enhancement techniques has emerged as a tool to restore and prevent species loss (Susini et al, 2007;Marzinelli et al, 2014Marzinelli et al, , 2016Shabnam et al, 2015;Falace et al, 2018;Verdura et al, 2018;Medrano et al, 2020), not all restoration initiatives have been successful (Coleman and Wernberg, 2017;Tamburello et al, 2019).…”

Impairment of microbial and meiofaunal ecosystem functions linked to algal forest loss

“…forests is possible using non-destructive methods and generating self-sustaining populations 33 . We recommend that policy makers plan active restoration actions (e.g., reforestation) to limit the loss of the important ecosystem services that these species provide 35 , 73 .…”

“…In terms of their contributions to ecosystem functions, seaweed-dominated nearshore habitats have been ranked among the most relevant carbon sinks (ca 173 TgC year −1 sequestration 29 ), leading to so called “blue carbon strategies”, aiming at exploring the potential of vegetated-marine habitats for mitigating climate change 30 – 32 . Due to their relevance in the provision of ecosystem services 15 , the magnitude of macroalgal forests decline is leading the scientific community to investigate the best strategies for their protection, as well as exploring the most efficient tools for their restoration 33 – 35 .…”

Marine ecosystem restoration in a changing ocean

“…In addition, because the outcome of restoration activities depends in large part upon the environmental conditions and levels and duration of past anthropogenic activities/impacts, restoration success critically hinges upon the removal or at least major modification of human-mediated stressors, which are particularly intense in some shallow-water habitats, deep-water fishing grounds and, in the future, where society allows deepsea mining. Pilot restoration actions provide lessons learned, paving the way for steady refinement of future, scaled-up, restoration actions (Verdura et al 2018;Montero-Serra et al 2019;Tamburello et al 2019;Gagnon et al 2020;Medrano et al 2020;Meysick et al 2020;Temmink et al 2020).…”

“…Another paper presents future scenarios of deep-sea ecosystems connected to coastal kelp forests under climate change anthropogenic activities, as well as the importance of cumulative impacts on deep-sea ecosystems for efficient ecosystem-based management within a restoration and global change context (Vilas et al 2021). Furthermore, in this issue, van Tatenhove et al (2021) highlight the importance of governmental arrangements (policies and legislation) in marine ecosystem restoration, and O' Connor et al (2021) investigate societal attitudes toward marine ecosystem restoration and find evidence for wide societal support despite a lack of clear awareness and understanding of marine restoration actions already underway.…”