Trace element concentrations in forage seagrass species of Chelonia mydas along the Great Barrier Reef

Abstract

Toxic metal exposure is a threat to green sea turtles (Chelonia mydas) inhabiting and foraging in coastal seagrass meadows and are of particular concern in local bays of the Great Barrier Reef (GBR), as numerous sources of metal contaminants are located within the region. Seagrass species tend to bioaccumulate metals at concentrations greater than that detected in the surrounding environment. Little is known regarding ecotoxicological impacts of environmental metal loads on seagrass or Chelonia mydas (C. mydas), and thus this study aimed to investigate and describe seagrass metal loads in three central GBR coastal sites and one offshore site located in the northern GBR. Primary seagrass forage of C. mydas was identified, and samples collected from foraging sites before and after the 2018/2019 wet season, and multivariate differences in metal profiles investigated between sites and sampling events. Most metals investigated were higher at one or more coastal sites, relative to data obtained from the offshore site, and cadmium (Cd), cobalt (Co), iron (Fe) and manganese (Mn) were found to be higher at all coastal sites. Principle Component Analysis (PCA) found that metal profiles in the coastal sites were similar, but all were distinctly different from that of the offshore data. Coastal foraging sites are influenced by land-based contaminants that can enter the coastal zone via river discharge during periods of heavy rainfall, and impact sites closest to sources. Bioavailability of metal elements are determined by complex interactions and processes that are largely unknown, but association between elevated metal loads and turtle disease warrants further investigation to better understand the impact of environmental contaminants on ecologically important seagrass and associated macrograzers.

Green Turtle (Chelonia mydas) Blood and Scute Trace Element Concentrations in the Northern Great Barrier Reef

“…Cobalt was consistently higher not only in coastal C. mydas populations but particularly in Upstart Bay turtles. Such findings are true not only for the blood and scute analyses conducted in the present study but also in previous analyses of C. mydas blood (Villa et al, 2017), scutes (Villa et al, 2019), and seagrass species within the same study region (Thomas et al, 2020; Wilkinson et al, 2022). Concentrations of Co reported in Upstart Bay are purportedly the highest reported in blood collected from marine turtles or other vertebrates from anywhere else in the world (Villa et al, 2017).…”

“…It was predicted that C. mydas blood metal concentrations would be lower at the control site (Howick Island Group) compared with each coastal site studied. Previous research in this region showed that metal concentrations were consistently higher in coastal C. mydas blood (Villa et al, 2017) and forage material (seagrass; Thomas et al, 2020; Wilkinson et al, 2022) compared with the natural baseline metal levels in an area minimally influenced by land‐based contaminants and industrial activity, Howick Island Group (Villa et al, 2017). In the present study, several elements (Al, Co, Mg, and Mn) were occasionally higher in blood collected from one or more coastal sites compared with the Howick Island Group, though most elements were detected at similar concentrations between sites.…”

Seagrass Ecosystems of Tropical Islands As Bioindicator of Anthropogenic Trace Metal Contamination

“…K. Mishra & Farooq, 2022a;Nikalje & Suprasanna, 2018;Rainbow, 2007). Once trace metals are accumulated in seagrass tissues, they are transferred to seagrass associated herbivores (e.g., fish and turtles), detritus grazers, leaf epiphytes and other organisms and gets biomagnified in trophic food chains and webs (Jiang et al, 2023;Schneider et al, 2018a;Suheryanto & Ismarti, 2018;Wilkinson et al, 2022).…”

Mangroves in a transforming world : Biogeochemical interactions, global change drivers, and innovative mitigation strategies

“…Mangroves can also uptake and translocate these pollutants within their tissues, leading to their bioaccumulation (Analuddin et al, 2017;Arumugam et al, 2018;Dudani et al, 2017). Moreover, seagrasses have the capacity to absorb heavy metals and can be used for phytoremediation in polluted water bodies, although their exposure to these substances severely impacts their health (Yadav et al, 2021), and that of grazers by bioaccumulation (Wilkinson et al, 2022).…”