Abstract
Abstract. Assemblages of corals characterise specific reef biozones and the environmental conditions that change spatially across a reef and with depth. Drill cores through fossil reefs record the time and depth distribution of assemblages, which captures a partial history of the vertical growth response of reefs to changing palaeoenvironmental conditions. The effects of environmental factors on reef growth are well understood on ecological timescales but are poorly constrained at centennial to geological timescales. pyReef-Core is a stratigraphic forward model designed to solve the problem of unobservable environmental processes controlling vertical reef development by simulating the physical, biological and sedimentological processes that determine vertical assemblage changes in drill cores. It models the stratigraphic development of coral reefs at centennial to millennial timescales under environmental forcing conditions including accommodation (relative sea-level upward growth), oceanic variability (flow speed, nutrients, pH and temperature), sediment input and tectonics. It also simulates competitive coral assemblage interactions using the generalised Lotka–Volterra system of equations (GLVEs) and can be used to infer the influence of environmental conditions on the zonation and vertical accretion and stratigraphic succession of coral assemblages over decadal timescales and greater. The tool can quantitatively test carbonate platform development under the influence of ecological and environmental processes and efficiently interpret vertical growth and karstification patterns observed in drill cores. We provide two realistic case studies illustrating the basic capabilities of the model and use it to reconstruct (1) the Holocene history (from 8500 years to present) of coral community responses to environmental changes and (2) the evolution of an idealised coral reef core since the last interglacial (from 140 000 years to present) under the influence of sea-level change, subsidence and karstification. We find that the model reproduces the details of the formation of existing coral reef stratigraphic sequences both in terms of assemblages succession, accretion rates and depositional thicknesses. It can be applied to estimate the impact of changing environmental conditions on growth rates and patterns under many different settings and initial conditions.
Highlights
Ecologists and geologists tend to have different spatial and temporal perspectives of coral reefs
We present a 1-D deterministic, carbonate stratigraphic forward model called pyReef-Core that simulates vertical reef sequences comparable to those found in actual fossil reef drill cores. pyReef-Core is a tool to represent how dynamic biological and physical processes interact to create predictable, stratigraphic patterns
Tolerance functions are defined for each environmental factor as a set of four points that indicates both the range in which an assemblage would reasonably exist based on published empirical data (Done, 1982; Hopley et al, 2007; Dechnik, 2016) and the rate at which vertical accretion reduces as the environmental conditions exceed upper or lower threshold limits for each assemblage (Fig. 2)
Summary
Ecologists and geologists tend to have different spatial and temporal perspectives of coral reefs. Three software packages have been developed that represent important antecedents to the modelling effort described in this paper: CARBONATE-3D (C3D) (Warrlich et al, 2008), ReefSAM (Barrett and Webster, 2017), and SIMSAFADIM-CLASTIC (Clavera-Gispert et al, 2017) These models are 3-D and able to simulate hydrodynamic processes, sediment transport and biological production, but with varying degrees of realism. Because 1-D forward modelling prioritises accommodation space as the fundamental control over vertical sequences, it is a starting point to understand and constrain other essential influences on reef growth before adding greater complexity Rationalised this way, pyReef-Core serves as a basis for constraining the biological interactive aspect of carbonate production and the ef-. We focus on these three main controls; the model can simulate the impact of other ocean forcings (temperature, nutrients and pH) on coral reef development
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