10.5061/DRYAD.0R76J
Tomašových, Adam
Slovak Academy of Sciences
Kidwell, Susan M.
University of Chicago
Data from: Nineteenth-century collapse of a benthic marine ecosystem on
the open continental shelf
Dryad
dataset
2017
historical ecology
Chlamys hastata
land use history
Southern California Bight
Laqueus
community paleoecology
amino-acid racemization
Leopecten diegensis
Holocene
watershed history
National Science Foundation
https://ror.org/021nxhr62
EAR-1124189
2017-05-14T11:03:55Z
2017-05-14T11:03:55Z
en
https://doi.org/10.1098/rspb.2017.0328
1493254 bytes
2
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
The soft-sediment seafloor of the open continental shelf is among the
least-known biomes on Earth, despite its high diversity and importance to
fisheries and biogeochemical cycling. Abundant dead shells of epifaunal
suspension-feeding terebratulid brachiopods (Laqueus) and scallops on the
now-muddy mainland continental shelf of southern California reveal the
recent, previously unsuspected extirpation of an extensive offshore
shell-gravel ecosystem, evidently driven by anthropogenic siltation.
Living populations of attached epifauna, which formerly existed in a
middle- and outer-shelf mosaic with patches of trophically diverse muds,
are restricted today to rocky seafloor along the shelf edge and to the
sandier shelves of offshore islands. Geological age-dating of 190 dead
brachiopod shells shows that (i) no shells have been produced on the
mainland shelf within the last 100 years, (ii) their shell production
declined steeply during the nineteenth century, and (iii) they had
formerly been present continuously for at least 4 kyr. This loss,
sufficiently rapid (less than or equal to 100 years) and thorough to
represent an ecosystem collapse, coincides with intensification of
alluvial-plain land use in the nineteenth century, particularly livestock
grazing. Extirpation was complete by the start of twentieth-century
urbanization, warming, bottom fishing and scientific surveys. The loss of
this filter-feeding fauna and the new spatial homogeneity and dominance of
deposit- and detritus-feeders would have altered ecosystem functioning by
reducing habitat heterogeneity and seawater filtering. This discovery,
attesting to the power of this geological approach to recent ecological
transitions, also strongly increases the spatial scope attributable to the
negative effects of siltation, and suggests that it has been
under-recognized on continental shelves elsewhere as a legacy of coastal
land use.
Table-spatial distribution of Laques erythraeus, Leopecten diegensis and
Chlamys hastataOccurrences of Laques erythraeus, Leopecten diegensis and
Chlamys hastata in living (Live) and death (Dead) assemblages, with
latitude, longitude, water depth (m), year of sampling (NA if unknown) and
sampling gear. Some data refer to presence-absence data (0-absent,
1-present) and some to abundance data (column Data). Occurrences are
partitioned into mainland-shelf and island-shelf occurrences (column
Shelf.island). Some occurrences are based on photographic surveys. The
column "Survey" refers to monitoring of wastewater agencies (LA
City, LA County, Orange County, Point Loma, and South Bay), to Bight-wide
surveys, to photographic USGS surveys, or Melville 2012 survey (performed
by authors of this study).Table-spatial distribution.xlsTable-agesSummary
of radiocarbon-calibrated shell ages of Laqueus erythraeus estimated by
amino-acid racemization (with 95% confidence intervals on the mean age),
with water depth (m), sampling year, and D/L of Aspartic and Glutamic
acids.Tomasovych and Kidwell supplement R codeSource code for evaluating
the postmortem age-fequency distribution of the brachiopod Laqueus
erythraeus from the Southern California Bight written in R language.
Postmortem age estimates based on the Bayesian fitting of Allen et al.
(2013) are assigned to a vector directly in this code. The code recreates
the figures where the estimates of shell loss from the mixed layer are
based on the fitting of the age-frequency distribution to two-phase
exponential models, and these estimates are used to reconstruct the
trajectory of production.Laqueus postmortem age analyses.txt
Southern California Bight
California