Habitat Contractions to Drive Future Planktonic Foraminifera Distribution and Diversity Change

Abstract

Aim

Unicellular calcifiers known as planktonic foraminifera (PF) are of interest for their contribution to the global ocean carbonate cycle and widespread use as paleoclimate proxies. Global warming has impacted current PF habitats, but PF have proven capable of ecological response through distributional shifts. Changing ocean conditions, characterized by warming and increased stratification, raise questions about the extent of PF biogeographical change and consequences for marine ecosystems. Here, we aim to (i) project future changes in abundance and distribution of six major PF species under different climate scenarios and (ii) quantify potential diversity change across 41 species.

Location

Global.

Time Period

Present and future (2070–2100).

Major Taxa Studied

Planktonic foraminifera (6 species).

Methods

We used PF abundance data from the Foraminifera Response to Climatic Stress (FORCIS) database to estimate ecological niches of six PF species. Environmental data (chlorophyll, radiation, isotherm depth and temperature) for the present and future were extracted from the IPSL-CM6A-LR model and used to run two ecological niche models (ENMs) across three climate scenarios. Models were calibrated on six major PF species (three subtropical, one temperate, one polar and one global) to identify optimal parameter settings. The resulting parameters were used to project global patterns of PF abundance and diversity distributions for PF species partitioned into five eco-groups defined by their relationships with symbionts.

Results

Our global maps support earlier studies showing PF abundance decreases (up to ~20% for one species) and poleward shifts, even in the most optimistic future climate scenario. For global and subtropical species, abundance decreases are centred around low-latitudes; for temperate and polar species, decreases are found in mid-latitudes. These trends suggest lower latitude waters are becoming less suitable for many PF species. Beyond species-specific distribution shifts, diversity is projected to decrease in low-latitudes and increase at mid- and high-latitudes by 2100.

Main Conclusions

Our results help constrain future large-scale calcification changes, with implications for oceanic CO₂ uptake and interpretation of paleoclimate archives. PF abundance declines and poleward shifts may suggest similar patterns for other mesozooplankton, with consequences for marine food webs.