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The contribution of carbonate-producing benthic organisms to the global marine carbon budget has been overlooked, the prevailing view being that calcium carbonate (CaC[O.sub.3]) is predominantly produced and exported by marine plankton in the 'biological pump.' Here, we provide the first estimation of the global contribution of echinoderms to the marine inorganic and organic carbon cycle, based on organism-level measurements from species of the five echinoderm classes. Echinoderms' global CaC[O.sub.3] contribution amounts to ~0.861 Pg CaC[O.sub.3]/yr (0.102 Pg C/yr of inorganic carbon) as a production rate, and ~2.11 Pg CaC[O.sub.3] (0.25 Pg C of inorganic carbon) as a standing stock from the shelves, slopes, and abyssal depths. Echinoderm inorganic carbon production (0.102 Pg C/yr) is less than the global pelagic production (0.4-1.8 Pg C/yr) and similar to the estimates for carbonate shelves globally (0.024-0.120 Pg C/yr). Echinoderm CaC[O.sub.3] production per unit area is ~27.01 g CaC[O.sub.3] x [m.sup.-2] x [yr.sup.-1] (3.24 g [C x [m.sup.-2] x [yr.sup.-1] as inorganic carbon) on a global scale for all areas, with a standing stock of ~63.34 g CaC[O.sub.3]/[m.sup.2] (7.60 g C/[m.sup.2] as inorganic carbon), and ~7.97 g C/[m.sup.2] as organic carbon The shelf production alone is 77.91 g CaC[O.sub.3] x [m.sup.-2] x [yr.sup.-1] (9.35 g C x [m.sup.-2] x [yr.sup.-1] as inorganic carbon) in contrast to 2.05 g CaC[O.sub.3] x [m.sup.-2] x [yr.sup.-1] (-0.24 g C x [m.sup.-2] x [yr.sup.-l] as inorganic carbon) for the slope on a global scale. The biogeography of the CaC[O.sub.3] standing stocks of echinoderms showed strong latitudinal variability. More than 80% of the global CaC[O.sub.3] production from echinoderms occurs between 0 and 800 m, with the highest contribution attributed to the shelf and upper slope. We provide a global distribution of echinoderm populations in the context of global calcite saturation horizons, since undersaturated waters with respect to mineral phases are surfacing. This shallowing is a direct consequence of ocean acidification, and in some places it may reach the shelf and upper slope permanently, where the highest CaC[O.sub.3] standing stocks from echinoderms originate. These organism-level data contribute substantially to the assessment of global carbonate inventories, which at present are poorly estimated. Additionally, it is desirable to include these benthic compartments in coupled global biogeochemical models representing the 'biological pump' and its feedbacks, since at present all efforts have focused on pelagic processes, dominated by coccolithophores. The omission of the benthic processes from modeling will only diminish the understanding of elemental fluxes at large scales and any future prediction of climate change scenarios. Key words: benthic compartments; CaC[O.sub.3] budget; carbon cycle; carbonate production; echinoderms; ocean acidification; standing stock.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2005.11.006 Byline: Babette Boeckel (a), Karl-Heinz Baumann (a), Rudiger Henrich (a), Hanno Kinkel (b) Keywords: Coccoliths; Distribution; Ecology; Statistics; Surface sediments; South Atlantic; Southern Ocean (Atlantic sector) Abstract: In this study, the coccolith compositions of 213 surface sediment samples from the South Atlantic and Southern Ocean were analysed with respect to the environmental parameters of the overlying surface waters. From this data set, the abundance patterns of the main species and their ecological affinities were ascertained. In general, Emiliania huxleyi is the most abundant species of the recent coccolith assemblages in the study region. However, the lower photic zone taxa, composed of Florisphaera profunda and Gladiolithus flabellatus often dominate the assemblages between 20[degrees]N and 30[degrees]S. If E. huxleyi is excluded, Calcidiscus leptoporus and F. profunda become the most abundant species, each dominating discrete oceanographic regimes. While F. profunda is very abundant in the sediments underneath warmer, stratified surface waters with a deep nutricline, Calcidiscus leptoporus is encountered in high-productivity environments. Furthermore, the results of a canonical correspondence analysis reveal affinities of Gephyrocapsa spp., Helicosphaera spp. and Coccolithus pelagicus for intermediate to higher nutrient conditions in a well-mixed upper water column. In contrast, Gladiolithus flabellatus seems to be associated with high temperatures and salinities under low-nutrient conditions. Based on the relative abundances of Calcidiscus leptoporus, F. profunda, Gladiolithus flabellatus, Helicosphaera spp., Umbilicosphaera foliosa, Umbilicosphaera sibogae and a group of subordinate subtropical species, six surface sediment assemblages have been identified, which reflect the distribution and characteristics of the overlying surface waters. Their distribution appears to be mainly a function of the relative position of the nutricline and thermocline in the overlying photic zone. Author Affiliation: (a) Faculty 05: Geosciences, University of Bremen, P.O. Box 33 04 40, 28334 Bremen, Germany (b) Institute for Geosciences, University Kiel, Ludewig-Meyn-Street 10, 24098 Kiel, Germany Article History: Received 24 February 2004; Revised 22 September 2005; Accepted 25 November 2005