DOI: 10.5061/dryad.5q1q6
title: Data from: Evidence for stratigraphy in molluscan death assemblages preserved in seagrass beds: St. Croix, U.S. Virgin Islands

description: Death assemblages that occupy the upper tens of centimeters of sediment in
 shallow-marine settings are often subject to extensive mixing, thereby
 limiting their usefulness in assessing environmentally mediated
 compositional changes through time in the local biota. Here, we provide
 evidence that dense, Thalassia-rich seagrass beds preserve a stratigraphic
 record of biotic variation because their dense root–rhizome mats inhibit
 mixing. We sampled benthic mollusk assemblages at seven localities in
 Thalassia-rich beds around St. Croix, USVI, collecting three separate
 sediment intervals of ~13 cm each to a total depth of ~40 cm below the
 sediment–water interface, and found evidence that sedimentary intervals
 preserved compositional stratigraphy. Further, some localities displayed
 systematic, directional changes down-core. An examination of
 interval-to-interval changes in composition revealed that compositional
 variation was unique from locality to locality rather than reflecting
 coordinated, island-wide transitions. In general, however, relative
 abundances of epifaunal gastropods and small lucinid bivalves tended to
 decrease with depth below the sediment–water interface. Quantitative
 comparisons of life-to-death assemblages from each successive sedimentary
 interval demonstrated that the shallowest death assemblages were typically
 more similar to the life assemblages than were deeper assemblages,
 suggesting that deeper intervals provide records of earlier community
 states.
description: Death Assemblage - Arkle
 2017Raw abundances of death
 assemblage data from seven localities around St. Croix, USVI. Singletons
 have been removed and bivalve abundances have been halved to provide a
 minimum number of individuals (MNI). First two letters in row names
 (sites) indicate locality (SC=Smuggler's Cove, CH=Christiansted
 Harbor, PP=Power Plant, SR=Salt River Bay, MP=Molasses Pier,
 HP=Ha'Penny Bay, DS=Dump Site). First set of numbers in sample labels
 indicate position on the transect (in meters). Letters B,C, and D indicate
 depth (see text), and numbers 11 and 12 indicate sampling years (2011 and
 2012, respectively). Columns are species names.Arkle_Dead_FINAL.xlsxLife Assemblage - Arkle 2017Raw abundances of life assemblage data from seven localities around St. Croix, USVI. Singletons have been removed. First two letters in row names (sites) indicate locality (SC=Smuggler's Cove, CH=Christiansted Harbor, PP=Power Plant, SR=Salt River Bay, MP=Molasses Pier, HP=Ha'Penny Bay, DS=Dump Site). First set of numbers in sample labels indicate position on the transect (in meters). Letter A indicates that all are living individuals, and numbers 11 and 12 indicate sampling years (2011 and 2012, respectively). Columns are species names.Arkle_Live_Final.xlsxSeagrass Census - Arkle 2017Average seagrass and macroalgal abundances from seven localities around St. Croix, USVI. First two letters in row names (sites) indicate locality (SC=Smuggler's Cove, CH=Christiansted Harbor, PP=Power Plant, SR=Salt River Bay, MP=Molasses Pier, HP=Ha'Penny Bay, DS=Dump Site). First set of numbers in sample labels indicate position on the transect (in meters), and numbers 11 and 12 indicate sampling years (2011 and 2012, respectively). Columns are species names.Arkle_Seagrass_FINAL.xlsx