Radiocarbon dating supports bivalve-fish age coupling along a bathymetric gradient in high-resolution paleoenvironmental studies

Abstract

Studies of paleocommunities and trophic webs assume that multispecies assemblages consist of species that coexisted in the same habitat over the duration of time averaging. However, even species with similar durability can differ in age within a single fossil assemblage. Here, we tested whether skeletal remains of different phyla and trophic guilds, the most abundant infaunal bivalve shells and nektobenthic fish otoliths, differed in radiocarbon age in surficial sediments along a depth gradient from 10 to 40 m on the warm-temperate Israeli shelf, and we modeled their dynamics of taphonomic loss. We found that, in spite of the higher potential of fishes for out-of-habitat transport after death, differences in age structure within depths were smaller by almost an order of magnitude than differences between depths. Shell and otolith assemblages underwent depth-specific burial pathways independent of taxon identity, generating death assemblages with comparable time averaging, and supporting the assumption of temporal and spatial co-occurrence of mollusks and fishes.

Holocene fish assemblages provide baseline data for the rapidly changing eastern Mediterranean

“…The sample completeness at each station was never lower than 0.8, and it was 0.97 for the whole transect (Table 2). Observed and coverage standardized species richness peaked at 30 m, possibly because of the greatest time-range of the assemblage (29–5012 yr; Albano et al, 2020). Especially the assemblages between 10 and 30 m depth are clearly clustered in multivariate space, and differ from each other (global test: F = 4.695, p = 0.001; pairwise tests significant at α = 0.05; Figure 3).…”

“…Otoliths are durable remains and we showed that their assemblages span decades to millennia (Figure 2). Otoliths are degraded by a two-stage taphonomic process: the first and faster occurs in surficial sediments and has half-lives of 4–200 years, whereas the second and slower occurs after burial with half-lives of 30–500 years (Albano et al, 2020). Consequently, young otoliths, as are those that belong to Lessepsian species, have high chances of preservation and enable non-indigenous species detection beyond the limitations of species small body size, cryptic lifestyle, and restricted seasonality.…”

“…Radiocarbon ages were converted to calendar years with a constant regional marine reservoir correction (Δ R ) of 3 ± 66 years, which is the weighted mean of eight published pre-bomb Δ R values from Israel and Lebanon (Boaretto et al, 2010; Reimer and McCormac, 2002). For samples younger than 1950 AD, the fraction of modern carbon (F 14 C) was converted to calendar ages using a regional marine calibration curve and the calibration software OxCal v4.2 (for details see Albano et al, 2020). All ages were reported in calendar years before 2016, the year of sample collection.…”

COMPARING DIRECT CARBONATE AND STANDARD GRAPHITE 14C DETERMINATIONS OF BIOGENIC CARBONATES

“…An increasing variety of scientific investigations require a large number of radiocarbon analyses to address their underlying research questions, as exemplified by recent studies assessing the degree of time-averaging in natural or anthropological shelly accumulations (Kowalewski et al 2018;New et al 2019;Parker et al 2019;Albano et al 2020). These types of studies are generally constrained by their analytical budget rather than by the number of samples suitable for analysis, whereas some are limited by the size of the targeted specimens.…”

“…In response to this growing need, a direct carbonate AMS 14 C sputter method was developed by Longworth et al (2013) that allows submilligram samples of carbonate powder to be analyzed quickly and efficiently. Several publications have highlighted the utility of direct carbonate 14 C dating where it has been used on its own or in combination with amino acid racemization to determine time-averaging in taphonomic studies (Dominguez et al 2016;Kosnik et al 2017;Ritter et al 2017;Parker et al 2019;Albano et al 2020) or coupled with standard precision 14 C and uranium/thorium dating to determine coral age distributions (Grothe et al 2016).…”