Living holoplanktonic gastropods (pteropods and heteropods) are a common component of the zooplankton at all latitudes and are highly sensitive indicators of surface ocean changes. Despite having a fossil record that may extend from the Jurassic, there are few detailed stratigraphic sequences of holoplanktonic gastropods and, consequently, they are rarely used in biostratigraphy. This is largely due to the susceptibility of their delicate aragonitic shells to dissolution. However, in well-preserved sediments, fossil holoplanktonic gastropods have the potential to contribute valuable information for paleoceanography, paleoecology, and stratigraphic correlation. Here we present a ~300 ky record of holoplanktonic gastropods from two sites cored/drilled offshore of Montserrat during Integrated Ocean Drilling Program (IODP) Expedition 340. Oxygen isotope stratigraphy was used to produce a stratigraphic framework for each site, which was compared and correlated to the corresponding downcore abundances of holoplanktonic gastropods. In addition, the record of previously cored Site CAR-MON 2, ~15 km southwest of IODP Site U1396, was compared to data at Sites U1395 and U1394 to identify species associations that are reproducible across the area. A number of downhole distributions were found to correlate significantly across the three sites, highlighting ten key species, three of which (Heliconoides inflatus, Creseis clava, and Atlanta plana) display significant relationships to multiple holoplanktonic gastropod species. Fluctuations in species abundance were found not to be related to changes in temperature, locally or globally, and were more likely to indicate predator-prey relationships or competition for prey. This made holoplanktonic gastropod assemblages unsuitable as stratigraphic markers in this area but improves our understanding of holoplanktonic gastropod ecology in the Caribbean Sea. 10,000/m 3 , constituting an important component of the ocean food web at all latitudes (Fabry et al., 2008). There are two groups of holoplanktonic gastropods: pteropods (Thecosomata and Gymnosomata) and heteropods (Pterotracheoidea). Within these Chapter contents

The aragonite shell–bearing thecosome pteropods are an important component of the oceanic plankton. However, with increasing <i>p</i>CO₂ and the associated reduction in oceanic pH (ocean acidification), thecosome pteropods are thought to be particularly vulnerable to shell dissolution. The distribution and preservation of pteropods over the last 250,000 years have been investigated in marine sediment cores from the Caribbean Sea close to the island of Montserrat. Using the <i>Limacina</i> Dissolution Index (LDX), fluctuations in pteropod dissolution through the most recent glacial/interglacial cycles is documented. By comparison to the oxygen isotope record (global sea ice volume), we show that pteropod dissolution is closely linked to global changes in <i>p</i>CO₂ and pH and is, therefore, a global signal. These data are in agreement with the findings of experiments upon living pteropods, which show that variations in pH can greatly affect aragonitic shells. The results of this study provide information which may be useful in the prediction of future changes to the pteropod assemblage caused by ocean acidification

No abstract