Pennsylvanian sea level cycles, nutrient availability and brachiopod paleoecology Alberto Pe ´rez-Huerta a, * , Nathan D. Sheldon b a Palaeontological Research Centre, Mahasarakham University, 44150 Mahasarakham, Thailand b Department of Geology, Royal Holloway University of London, Egham, Surrey TW20 0EX, United Kingdom Received 13 March 2005; received in revised form 24 July 2005; accepted 29 July 2005 Abstract As with modern organisms, the spatial and temporal distribution of fossil communities was controlled by both the physical setting in which the organisms lived and by the organisms’ physiology and interactions. By studying the sedimentological and geochemical context of fossil communities, it is possible to assess the relative importance of the physical setting and the organisms’ physiology. Comparison of Pennsylvanian brachiopod associations with changing sedimentological context (water depth/facies) and nutrient availability indicates that body size is a function of water depth and nutrient availability for most spire-bearing (athyridids and spiriferids) brachiopods but rarely for productid brachiopods. Spire-bearing brachiopods dominate the associations in high-nutrient settings, and productid brachiopods dominate the associations in low-nutrient settings. This difference suggests that physiological differences between brachiopod orders, such as lophophore filtering efficiency, play an important role in controlling their distribution. D 2005 Elsevier B.V. All rights reserved. Keywords: Pennsylvanian; Brachiopods; Sea level change; Nutrients; Weathering 1. Introduction Fossil communities analyzed in the context of their sedimentological and geochemical setting can give fundamental information about paleoecological con- trols on their structure, composition, and spatial dis- tribution. In benthic marine communities, the two most important factors are thought to be physico- chemical control (e.g., substrate composition/struc- ture; water depth, oxygen availability; Boucot, 1981) or biological control (e.g., species interactions, avail- ability of nourishment; Fu ¨rsich and Hurst, 1974). Traditionally, the physico-chemical factors substrate type and sedimentary facies were thought to be the primary controls on the distribution of benthic organ- isms, especially for filter-feeders, with biological con- trols playing a secondary role. However, for some benthic organisms such as brachiopods, food supply 0031-0182/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2005.07.020 * Corresponding author. Fax: +66 43 754373. E-mail address: aprezhuerta@yahoo.com (A. Pe ´rez-Huerta). Palaeogeography, Palaeoclimatology, Palaeoecology 230 (2006) 264– 279 www.elsevier.com/locate/palaeo