Periodic Reporting for period 1 - MICRO2MACRO (Microfossils and data science: a new approach to infer the impact of global climate on plankton Macroecology)
Reporting period: 2022-09-01 to 2024-08-31
One of the most pressing scientific challenges today is understanding the fate of our oceans and marine ecosystems under on-going climate change. Unfortunately, anthropogenic stressors act at a rate and magnitude that exceed recent natural variability, making the use of decadal ecological data and time-series insufficient for predictions of future behavior of marine ecosystems. MICRO2MACRO reconstructed snapshots of marine pelagic ecosystems between 54 and 50 million years ago (early Eocene), when climate and environmental conditions approximated what we may start to experience in the next centuries if global warming continues business as usual. Using the microfossil record of planktonic foraminifera (PF), the most complete of any Cenozoic eukaryote, the project generated the first methodologically controlled (hence reproducible) early Cenozoic global dataset of ecology, abundance, species composition, diversity and biogeography (macroecology) of these prolific pelagic calcifiers.
The overarching goal of the project was to test for links between time-specific climate (e.g. sea surface temperatures) and ecosystem (e.g. species composition, dominant ecology) configurations, and understand how plankton biogeography was shaped in a warmer world. The new results obtained with MICRO2MACRO highlight future ecological and evolutionary analogues if the current climate trajectory remains interrupted and we are to hit climate conditions similar to those in the Eocene. Given the uncertainties associated with projections based on modern data this study represents a major advancement in the field.
The overarching goal of the project was to test for links between time-specific climate (e.g. sea surface temperatures) and ecosystem (e.g. species composition, dominant ecology) configurations, and understand how plankton biogeography was shaped in a warmer world. The new results obtained with MICRO2MACRO highlight future ecological and evolutionary analogues if the current climate trajectory remains interrupted and we are to hit climate conditions similar to those in the Eocene. Given the uncertainties associated with projections based on modern data this study represents a major advancement in the field.
MICRO2MACRO targeted the generation of new species-specific abundance data of planktonic foraminifera for the time interval 54-50 Ma (early Eocene) in each main ocean basin to be compared against climate records for the same time interval. A key aspect was to generate such data in a methodologically consistent fashion and with a taxonomy standardized at the species level, to make the new dataset fully reproduceable and comparable with modern datasets. With over 11600 specimens counted, isolated and identified at the species level from 8 tropical to polar oceanic locations, this represented a taxonomic effort of unprecedented complexity and completeness for the study time interval. This effort resulted in the first methodologically and taxonomically consistent global dataset of planktonic foraminiferal species abundance being produced for the early Eocene.
The new dataset was used to reconstruct latitudinal biodiversity variability for the early Eocene and its relationship with sea-surface temperatures (SST) and mean global climate. Contrary to expectations we find that:
1. The early Eocene hothouse ocean was characterized by a Latitudinal Diversity Gradient (LDG) as steep as the moderns;
2. In the early Eocene Ocean different species associations characterize tropical, mid and polar latitudes.
3. SST is a strong environmental predictor of the LDG in the early Eocene, similar to the moderns;
These findings all together imply that in the Cenozoic a LDG in the ocean can develop irrespectively of significantly warmer or colder mean global climate conditions. Hence, mean global climate does not control the latitudinal distribution of diversity in the ocean, it can only enhance or dampen a preexisting pattern.
The new dataset was used to reconstruct latitudinal biodiversity variability for the early Eocene and its relationship with sea-surface temperatures (SST) and mean global climate. Contrary to expectations we find that:
1. The early Eocene hothouse ocean was characterized by a Latitudinal Diversity Gradient (LDG) as steep as the moderns;
2. In the early Eocene Ocean different species associations characterize tropical, mid and polar latitudes.
3. SST is a strong environmental predictor of the LDG in the early Eocene, similar to the moderns;
These findings all together imply that in the Cenozoic a LDG in the ocean can develop irrespectively of significantly warmer or colder mean global climate conditions. Hence, mean global climate does not control the latitudinal distribution of diversity in the ocean, it can only enhance or dampen a preexisting pattern.
The findings from MICRO2MACRO are completely new and challenge the current view according to which a modern-style latitudinal diversity gradient originated in the late Cenozoic as a consequence of the progressive refrigeration of global climate. The results from MICRO2MACRO for the early Eocene super warm ocean, indicate that a steep Latitudinal Diversity Gradient can still exist when mean climate is up to 15°C warmer than today, provided species are adapted to warm ocean conditions. Modern ocean organisms are adapted to much colder climate conditions than those in the Eocene, hence major species reorganization and a reshuffling of the LDG can be expected on human time scales if global warming continues business as usual. However, giving it enough time, our new data show that the LDG will eventually be re-established, through adaptation and evolutionary processes on long geological time scales.