Quantifying Sedimentary Capture of Biological Information

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Quantifying Sedimentary Capture of Biological Information: meta-analysis of bias in molluscan shell assemblagesSusan M. Kidwell(EAR-0345897)ABSTRACTGeohistorical information on the state of marine ecosystems - that is, data from sedimentary cores for periods that pre-date quantitative studies by scientists -- provides unique opportunities to (a) extend ecological time-series into the past and thereby identify pre-impact baselines and drivers of relatively recent environmental change, and (b) use past geointervals to test for organizing principles in the behavior of species and communities. To extract full value from sedimentary records, however, we need a quantitative evaluation of post-mortem bias in biological information, particularly under ordinary conditions of sedimentary time-averaging. The primary method used to evaluate bio-data capture by sedimentary records is a "live-dead" study, in which the taxonomic composition and numerical abundances of skeletal remains (here, the shells of benthic mollusks) are compared against the local living community. This project will use both conventional statistics and meta-analysis (new to sedimentary geology and paleoecology) both to quantify bias and to rank factors that determine data quality. Factors to be investigated include (1) intrinsic biology (e.g., species' body size, shell mineralogy, life habit), (2) extrinsic environment (e.g., habitat type, bathymetry, latitude), and (3) methodology (e.g., sampling gear and density in time/space, mesh-size used to separate specimens from sediment). The effects of spatial scaling (i.e., the capture of environmental gradients, the capture of regional information by single death assemblages) will also be tested explicitly. These analyses, using existing data generated from many decades of fieldwork around the world in coastal and shelf settings, and representing millions of dollars of past investment by geological, biological and fisheries groups, are an important step in improving the design of paleobiologic sampling and protocols for analysis, particularly for studies that seek to (a) link geohistorical with neontologic information, or (2) use death assemblages to substitute for or augment neontologic inventories of biodiversity. A key aspect of the project is enlarging of the digital database both by further literature search, and by the "rescue" of data from 4 exceptionally valuable past ecological surveys in US coastal waters. Patterns revealed (or debunked) by meta-analysis provide new hypotheses for field experimentation and numerical modeling, as is already occurring in response to pilot work on this subject. In addition, it is expected that the techniques developed from this work (including factors identified as critical to bio-data capture) can be applied to the evaluation of other major groups and environments.