Abstract
The distribution of modern symbiont-bearing larger foraminifera is confined to tropical and subtropical shallow water marine habitats and a narrow range of environmental variables (e.g. temperature). Most of today's taxa are restricted to tropical and subtropical regions (between 30°N and 30°S) and their minimum temperature limits are governed by the 14 to 20°C isotherms. However, during times of extensive global warming (e.g., the Eocene and Miocene), larger foraminifera have been found as far north as 50°N (North America and Central Europe) as well as towards 47°S in New Zealand. During the last century, sea surface temperatures have been rising significantly. This trend is expected to continue and climate change scenarios for 2050 suggest a further increase by 1 to 3°C. We applied Species Distribution Models to assess potential distribution range changes of three taxa of larger foraminifera under current and future climate. The studied foraminifera include Archaias angulatus, Calcarina spp., and Amphistegina spp., and represent taxa with regional, superregional and global distribution patterns. Under present environmental conditions, Amphistegina spp. shows the largest potential distribution, apparently due to its temperature tolerance. Both Archaias angulatus and Calcarina spp. display potential distributions that cover currently uninhabited regions. Under climate conditions expected for the year 2050, all taxa should display latitudinal range expansions between 1 to 2.5 degrees both north- and southward. The modeled range projections suggest that some larger foraminifera may colonize biogeographic regions that so far seemed unsuitable. Archaias angulatus and Calcarina spp. also show an increase in habitat suitability within their native occurrence ranges, suggesting that their tolerance for maximum temperatures has yet not been fully exploited and that they benefit from ocean warming. Our findings suggest an increased role of larger foraminifera as carbonate producers and reef framework builders in future oceans.
Highlights
Larger, symbiont-bearing foraminifera are marine protists that are abundant in tropical and subtropical reef and shelf-regions of the world’s oceans
123 records were available for Amphistegina spp., 35 for Archaias angulatus, and 31 for Calcarina spp
The potential distributions of Archaias angulatus and Amphistegina spp. in the Atlantic Ocean, the distributions of Calcarina spp. and Amphistegina spp. in the Indopacific as well as changes with future climate are described in detail
Summary
Symbiont-bearing foraminifera are marine protists that are abundant in tropical and subtropical reef and shelf-regions of the world’s oceans. They are major contributors to carbonate production and play an important role in the formation and stability of global reefs [1,2]. Larger symbiont-bearing foraminifera are most abundant in warm, oligotrophic waters [3,4]. They are frequently associated with scleractinian corals due to their corresponding environmental requirements. We applied Species Distribution Models (SDMs) on three taxa of larger foraminifera: Archaias angulatus (Fichtel & Moll, 1798), Calcarina spp. d’Orbigny, 1826 and Amphistegina spp. d’Orbigny, 1826. Amphisteginids are circumglobally distributed and represents one of the most widely distributed and ubiquitous taxa of symbiont-bearing foraminifera
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