Climatic Influences on Deep‐sea Ostracode (Crustacea) Diversity for the Last Three Million Years

Abstract

Abstract. Ostracodes are small, bivalved crustaceans with the finest-scale fossil resolution of any metazoan, rivaled only by the fossil record of the protistan Foraminifera. This article presents a synthesis of the patterns and possible causes of alpha species diversity variation in benthic deep-sea ostracodes at drilling sites in the North Atlantic and Arctic Oceans. Taken together, these sites represent a period of great climatic variability covering the past three million years. Sediment cores taken from the Mid-Atlantic Ridge show a positive correlation between warm temperatures and high species diversity. These Mid-Atlantic Ridge cores, at the same latitude as northern Spain, show the same positive correlation during the last two glacial-interglacial cycles (200-0 ka [thousands of years ago]) as they do during the pre-glacial Pliocene 2.85-2.4 Ma (millions of years ago). This positive correlation is also found in Pliocene cores from the Rockall Plateau, at the same latitude as Ireland. During the last 200 thousand years, however, this correlation is reversed in cores taken from both the Rockall and Iceland Plateaus. The discovery of high diversity during colder periods in recent high-latitude Rockall and Iceland cores seems to be explained by spikes in diversity caused by ice-rafting events, which would not affect the lower-latitude Mid-Atlantic Ridge. The Heinrich ice-rafting events reduce North Atlantic surface temperatures and salinity every ;6-12 ka, dramatically decreasing surface productivity. This increase in diversity during Heinrich events may be explained either by a negative correlation between surface productivity and benthic diversity or by increase in diversity caused by moderate disturbance when ice rafted debris fall to the bottom of the ocean.

Temporal latitudinal-gradient dynamics and tropical instability of deep-sea species diversity

“…This pattern shows that global climate changes have strongly influenced tropical deep-sea diversity, similar to previously reported effects at mid to high latitudes (11,13,28). This result, coupled with the extremely dynamic diversity trajectory of the tropical ODP 925, suggests that the LSDGs in the deep ocean are not driven by a gradient of increasing environmental stability from poles to tropics.Both temperature and productivity have been considered important factors controlling deep-sea species diversity but their relative importance is uncertain (4,13,28,(38)(39)(40)(41). Species diversity…”

“…Surprisingly little attention has been given to understanding low-latitude deepsea diversity and the temporal dynamics of the LSDGs. Although pollen records suggest a persistent latitudinal diversity gradient existed in terrestrial ecosystems over the last 13,000 years (17, 18), we know of no studies of species-level temporal dynamics of LSDGs based on fossil assemblages from marine environments, despite the sensitivity of marine ecosystems to climatic change (12,13,(19)(20)(21)(22)(23)(24).The Ostracoda (Crustacea) are an important component of the deep-sea benthos (25)(26)(27), and the only commonly fossilized metazoan group in deep-sea sediments (12,13,28). Their various habitats and ecological preferences represent a wide range of deep-sea benthic niches, and their fossil record is considered representative of the benthic community (12,13,28).…”

“…Surprisingly little attention has been given to understanding low-latitude deepsea diversity and the temporal dynamics of the LSDGs. Although pollen records suggest a persistent latitudinal diversity gradient existed in terrestrial ecosystems over the last 13,000 years (17, 18), we know of no studies of species-level temporal dynamics of LSDGs based on fossil assemblages from marine environments, despite the sensitivity of marine ecosystems to climatic change (12,13,(19)(20)(21)(22)(23)(24).…”

“…The Ostracoda (Crustacea) are an important component of the deep-sea benthos (25)(26)(27), and the only commonly fossilized metazoan group in deep-sea sediments (12,13,28). Their various habitats and ecological preferences represent a wide range of deep-sea benthic niches, and their fossil record is considered representative of the benthic community (12,13,28).…”

“…Their various habitats and ecological preferences represent a wide range of deep-sea benthic niches, and their fossil record is considered representative of the benthic community (12,13,28). Furthermore, large (Ϸ130 m) glacial-interglacial sea-level changes (29), which drastically altered shallow-marine environments, had negligible effects on deep-sea habitats (e.g., Ͼ1,000 m water depth).…”