What decadal sediment trap time series reveal about planktonic foraminifera biodiversity turnover

Long-term perspectives are essential for understanding natural variability in marine biodiversity and for defining meaningful baselines to guide conservation in areas beyond national jurisdiction (ABNJ). Planktonic foraminifera provide one of the most continuous and globally distributed fossil records among microplankton, yet integrating turnover rates derived from sedimentary archives with present-day observations remains challenging. Temporal integration in sediments, taphonomic alteration, and the lack of absolute abundance data all hinder direct comparison across timescales. At the same time, modern observational programmes rarely extend beyond a few years, which limits our ability to contextualise short-term ecological change.

This project aims to address these challenges by analysing multiple decadal sediment trap time series of planktonic foraminifera from a variety of oceanographic settings, with the goal of connecting present-day observations with the long-term sedimentary archive. These unique datasets provide information on absolute abundance, which is rarely available in sediment cores, and capture seasonal, interannual and decadal variability at a high temporal resolution. By quantifying turnover rates, flux dynamics and species compositional changes across these different timescales, the project characterises the natural range of biodiversity variability, providing a basis for interpreting and comparing long-term trends.

Preliminary analyses indicate that year-to-year fluctuations in absolute abundances can be substantial, whereas relative species composition often remains comparatively stable over decadal scales. To understand how these patterns translate into the sedimentary record, we simulate the effects of temporal integration by pooling multi-year trap samples. This approach helps us to identify which aspects of ecological variability are likely to be retained, dampened, or lost once incorporated into sediments, thereby clarifying the interpretative limits of sediment-derived turnover rates.

This project advances our ability to interpret biodiversity signals preserved in marine sediments by combining multiple long-term sediment trap records with time-integration simulations. It helps clarify the degree to which sedimentary assemblages reflect true ecological change versus time-averaged noise. Through its time-extended perspective, the project provides a crucial link between modern observations, historical ecology, and the long-term dynamics required for effective and informed ocean stewardship.