Seagrass sedimentary deposits as security vaults and time capsules of the human past

Abstract

Seagrass meadows form valuable ecosystems, but are considered to have low cultural value due to limited research efforts in this field. We provide evidence that seagrass deposits play a hitherto unrealized central role in preserving valuable submerged archaeological and historical heritage across the world, while also providing an historical archive of human cultural development over time. We highlight three case studies showing the significance of seagrass in protecting underwater cultural heritage in Denmark, the Mediterranean and Australia. Moreover, we present an overview of additional evidence compiled from the literature. We emphasize that this important role of seagrasses is linked to their capacity to form thick sedimentary deposits, accumulating over time, thereby covering and sealing submerged archaeological heritage. Seagrass conservation and restoration are key to protecting this buried heritage while also supporting the role of seagrass deposits as carbon sinks as well as the many other important ecosystem functions of seagrasses.

Thermal dependence of seagrass ecosystem metabolism in the Red Sea

“…Seagrass ecosystems rank among the most productive (Duarte & Chiscano 1999) and economically valuable ecosystems in the world (Costanza et al 1997), offering important ecosystem services such as nurseries, food and shelter for commercially important fisheries, coastal stabilization, carbon sequestration, removal of nutrients (Orth et al 2006, Ruiz-Frau et al 2017) and bacterial pathogens (Lamb et al 2017) and protection of archaeological heritage (Krause-Jensen et al 2019). Seagrass ecosystems can be found worldwide, except for Antarctica (Green & Short 2003), and inhabit a broad thermal range (Lee et al 2007, Pedersen et al 2016).…”

Toward a Coordinated Global Observing System for Seagrasses and Marine Macroalgae

“…They protect coastal lives and property by stabilizing coastal sediments via both their belowground rhizome structure and leaf canopies (Cruz-Palacios and Van Tussenbroek, 2005;Bos et al, 2007). Seagrass ecosystems are also increasingly recognized as protecting underwater cultural heritage (Krause-Jensen et al, 2018).…”

“…A first-order estimate indicates that this macroalgal contribution is of the same order of magnitude as carbon sequestration by seagrasses, saltmarshes, and mangroves combined (Krause-Jensen and Duarte, 2016). The contribution of macroalgae to carbon sequestration varies among species (Trevathan-Tackett et al, 2015), but more direct estimates are needed to quantify sequestration, and this requires a paradigm shift in accounting procedures as well as development of methods to trace carbon from donor to sink habitats in the ocean (Krause-Jensen et al, 2018). As vegetated ecosystems have declined substantially in area (Waycott et al, 2009), many coastal areas have been converted from carbon sinks to sources, a shift that can, in principle, be reversed (Pendleton et al, 2012;Macreadie et al, 2015Macreadie et al, , 2017Marbà et al, 2015;Kerrylee et al, 2018).…”

Integrated Methodological Approach for the Documentation of Marine Priority Habitats and Submerged Antiquities: Examples from the Saronic Gulf, Greece

“…Usually, the existence of the two is interdependent since multiple archaeological sites are accompanied by the presence of seagrass. Seagrass has been proved to play a central role in the preservation of submerged archaeology, while its ability to accumulate sediment secures the site and preserves the sedimentary balance [42]. Artificial seagrass mats have been installed on submerged archaeological sites within the framework of the SASMAP project, aiming to protect them from erosion [11].…”