Defining variation in pre-human ecosystems can guide conservation: An example from a Caribbean coral reef

Abstract

This file includesSupplemental radiometric dating methods figures S1 to S4 Tables S1 and S2References for supplementary material 1 Supplemental radiometric dating methods U-Th dating was conducted on coral fragments using a Nu Plasma multi-collector inductively-coupled plasma mass spectrometer (MC-ICP-MS) in the Radiogenic Isotope Facility at the University of Queensland, following chemical treatment procedures and MC-ICP-MS analytical protocols described in Clark et al. [1] . For U-Th dating, each coral sample consisting of ~150 mg fine sand-size chips that were carefully fragmented, H 2 O 2 -treated and then hand-picked under a binocular microscope to remove any trace detritus or grains with discolouration was spiked with a mixed 229 Th-233 U tracer and then completely dissolved in double-distilled concentrated HNO 3 . After digestion, each sample was further treated with H 2 O 2 to decompose trace amounts of organic matter (if any) and to facilitate complete sample-tracer homogenization. U and Th were separated using conventional anion-exchange column chemistry using Bio-Rad AG 1-X8 resin. After stripping off the matrix from the column using double-distilled 7N HNO 3 as eluent, 4 N HNO 3 and 2%HNO 3 +0.03% HF mixture were used to elute U and Th into 3.5 ml pre-cleaned test tubes, respectively. After screening U and Th concentrations in the U and Th fractions using their 1:100 dilute solutions on a quadrupole ICP-MS, the U and Th separates for the samples were then re-mixed in 2% HNO 3 to make ~3 ml solution in a pre-cleaned 3.5 ml test tube. The mixed solution for each sample contained the entire Th fraction and a small percentage of the U fraction. The amount of U fraction to be added to the mixed solution was calculated based on the screening results and the MC-ICP-MS working sensitivity of the day, aiming to achieve ~5 volts of 238 U signal. The remixed U-Th solution was injected into the MC-ICP-MS through a DSN-100 desolvation nebulizer system with an uptake rate of ~0.06 ml/min. U-Th isotopic measurements were performed on the MC-ICP-MS using a detector configuration to allow simultaneous measurements of both U and Th isotopes. The 230 Th/ 238 U and 234 U/ 238 U activity ratios of the samples were calculated using the decay constants given in Cheng et al. [2] . 230 Th ages were calculated using the Isoplot 3.75 Program [3] . 230 Th ages were corrected for non-radiogenic 230 Th contributions using a modelled two-component-mixing non-radiogenic 230 Th/ 232 Th value based on the equation in Clark et al. [1] .

Modern, archaeological, and paleontological DNA analysis of a human-harvested marine gastropod (Strombus pugilis) from Caribbean Panama

“…The paleontological S. pugilis remains (n=11 adult shells) were collected from a fossilized fringing reef excavated for construction purposes near the old town of Lennond (9°21’37.0” N 82°16’09.9” W; see Figure 1 ). Twenty four Uranium-Thorium and eight radiocarbon dates from 32 coral pieces date the reef at Lennond to the mid-Holocene (Mean = 6507, SD = 407, Min = 5711, Max = 7187 years BP; Fredston-Hermann et al, 2013; Lin et al, 2019; O’Dea et al, 2020; Dillon et al, in submission). This predates the earliest evidence of human interactions with marine species in the region which starts around around 4000 BP (Baldi, 2011), and confirms previous conclusions that the Caribbean slope of Panama was prehistorically not extensively populated until the Late Holocene (Griggs, 2005; O.…”

“…By measuring the height, width, and lip thickness of S. pugilis shells from archaeological Sitio Drago (dated to AD 690-1410; Wake 2006; Wake et al 2012, 2013), paleontological shells from a mid-Holocene fringing coral reef at Lennond (Fredston-Hermann et al, 2013; Lin et al, 2019; O’Dea et al, 2020), and modern sites spaced throughout the Bocas del Toro archipelago, O’Dea et al (2014) found that size at sexual maturity has decreased consecutively from the paleontological ‘pre-human’ period to the archaeological deposits to the present day. This size decrease is associated with a decline in edible meat weight by ~40% over the past 7,000 years (O’Dea et al, 2014).…”

Microstructural characteristics of the stony coral genus Acropora useful to coral reef paleoecology and modern conservation

“…While heavily impacted and increasingly degraded now, coral reefs have been resilient to past sea‐level and temperature fluctuations over long timescales (Greer et al., 2009; Webster et al., 2018). Therefore, understanding the development of ancient coral reefs and their responses to natural environmental change is helpful to aid protection of presently healthy reefs and to restore degraded reefs in future (Humblet & Webster, 2017; Kuffner & Toth, 2016; Odea et al., 2020).…”

Millennial-scale change on a Caribbean reef system that experiences hypoxia

“…All of these characteristics increase the chance that waters will stratify and surface oxygen will fail to diffuse or become mixed into benthic waters (Diaz and Rosenberg 2008). The increasing eutrophication from runoff of nutrients that has been observed in the region (Seemann et al 2014), likely caused by deforestation and fertilization from local banana plantations and other human effluents (Stephens 2008, Cramer 2013, Aronson et al 2014, Graniero et al 2016, O'Dea et al 2020, could explain the perceived increased frequency of hypoxia in the bay. Alternatively, episodic hypoxic events may have naturally occurred for millennia, and simply been unobserved due to the lack of long-term proxy data and ephemerality of hypoxia.…”