On the benefits of being redundant: low compositional fidelity of diatom death assemblages does not hamper the preservation of environmental gradients in shallow lakes

Hassan, Gabriela S.

doi:10.1017/pab.2014.10

Cited by 16 publications

(16 citation statements)

References 62 publications

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“…Regardless of water depth, most shells in the mixed layer disintegrate quickly, with decadal-scale half-lives, whereas a small subset of shells persist for millennia by attaining a refuge from high loss rates. This postmortem persistence permits death assemblages sampled at local scales to carry information on composition and diversity accrued over long temporal scales, permitting the capture of regional-scale composition (Warme 1969; Kowalewski et al 1998; Smith 2008; Tomašových and Kidwell 2010; Miller et al 2014; Hassan 2015) even when most shells disintegrate quickly. This consistency in dynamics across the shelf, derived from AFD data, is also encouraging for habitat-scale paleoecological inference: it suggests that bathymetric variation in live-dead agreement in species composition that is encountered in some meta-analyses (e.g., Kidwell 2001; Tomašových and Kidwell 2011) arises from differences in scales of time averaging (and thus environmental condensation) rather than from bias per se (interspecies differences in preservation), a distinction that has not previously been possible.…”

Section: Discussionmentioning

confidence: 99%

Inferring skeletal production from time-averaged assemblages: skeletal loss pulls the timing of production pulses towards the modern period

2015

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Age-frequency distributions of dead skeletal material on the landscape or seabed—information on the time that has elapsed since the death of individuals—provide decadal- to millennial-scale perspectives both on the history of production and on the processes that lead to skeletal disintegration and burial. So far, however, models quantifying the dynamics of skeletal loss have assumed that skeletal production is constant during time-averaged accumulation. Here, to improve inferences in conservation paleobiology and historical ecology, we evaluate the joint effects of temporally variable production and skeletal loss on postmortem age-frequency distributions (AFDs) to determine how to detect fluctuations in production over the recent past from AFDs. We show that, relative to the true timing of past production pulses, the modes of AFDs will be shifted to younger age cohorts, causing the true age of past pulses to be underestimated. This shift in the apparent timing of a past pulse in production will be stronger where loss rates are high and/or the rate of decline in production is slow; also, a single pulse coupled with a declining loss rate can, under some circumstances, generate a bimodal distribution. We apply these models to death assemblages of the bivalve Nuculana taphria from the Southern California continental shelf, finding that: (1) an onshore-offshore gradient in time averaging is dominated by a gradient in the timing of production, reflecting the tracking of shallow-water habitats under a sea-level rise, rather than by a gradient in disintegration and sequestration rates, which remain constant with water depth; and (2) loss-corrected model-based estimates of the timing of past production are in good agreement with likely past changes in local production based on an independent sea-level curve.

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Section: Discussionmentioning

confidence: 99%

Inferring skeletal production from time-averaged assemblages: skeletal loss pulls the timing of production pulses towards the modern period

2015

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“…Por lo tanto, en base a la gran cantidad sistemática de datos ecológicos y taxonómicos de las especies, comienzan a usarse como bioindicadores de calidad de agua y bioproxy para las reconstrucciones paleoambientales de los cuerpos de agua (Battarbee 1986;Smol 2009). También, se evalúa su fidelidad composicional y ambiental desde una perspectiva de la Tafonomía actualística, experimental y comparativa (Hassan et al 2008, Flower y Ryves 2009Ryves et al 2009;Hassan 2015). Estas tendencias de investigación continúan intensificando y complejizándose hasta la actualidad.…”

Section: Breve Historiaunclassified

“…disolución) y físicos (ej. fragmentación) que afectan sus valvas, generando posibles distorsiones y/o sesgos en las interpretaciones (Hassan 2015). Estos procesos pueden ser generados por condiciones naturales en el momento de su depositación (ej.…”

Section: Algunas Precauciones Generalesunclassified

“…estado de las valvas). Estas consideraciones tafonómicas han sido aplicadas principalmente en las reconstrucciones paleoambientales (Blanco et al 2008;Hassan et al 2008;Flower y Ryves 2009;Ryves et al 2009;Hassan 2015), no así en los estudios enfocados a otras problemáticas arqueológicas. Por ejemplo, muchos estudios mencionan la presencia y/o ausencia de diatomeas sin aclarar si se consideran los fragmentos de diatomeas como señal de presencia y/o cuál es la proporción de estos fragmentos en el total de la muestra.…”

Section: Algunas Precauciones Generalesunclassified

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La arqueología desde el microscopio. Aportes interdisciplinarios de las diatomeas a las problemáticas arqueológicas

Grana

2018

Rev. Mus. Antrop.

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<p>Actualmente, las problemáticas arqueológicas generaran datos no solo desde la propia de la disciplina sino también desde teorías y metodologías provenientes de otras disciplinas. La Diatomología, una disciplina que forma parte de las Ciencias Biológicas, ha demostrado ser una importante herramienta para la Arqueología. El análisis de diatomeas ha sido aplicado en reconstrucciones paleoambientales, en el análisis de procesos de formación de sitio, en material arqueológico como el estudio de procedencia de materia prima para la cerámica, en el estudio del manejo prehistórico del agua y suelos, en los restos bioarquelógicos y, por último, en la conservación del patrimonio tangible. El objetivo del presente trabajo es realizar una revisión crítica de la evolución y estado actual de los análisis diatomológicos en cuestiones arqueológicas, principalmente incluyendo los estudios latinoamericanos. Para ello se propone discutir las potencialidades y limitaciones de estos estudios, con el fin de generar un puente conceptual que sea de utilidad para investigadores interesados en trabajar con estas líneas.</p>

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“…Geohistorical records contain valuable data on past generations of organisms and community states and are increasingly used as tools for conservation, including biodiversity assessment; identification of invasive species; recognizing past, prestress ecosystem states; and monitoring the progress of restoration (e.g., Swetnam et al 1999; National Research Council 2005; Smith 2008; Tsumjimoto et al 2008; Rick and Lockwood 2013; Lotz and McClenacha 2014; Dietl et al 2015; Kidwell 2015). Comparison of living communities with their locally accumulating death assemblages—that is, dead and discarded organic remains produced by the living community, such as shells, bones, molts, and cysts—is proving to be a useful tool in marine, lacustrine, and estuarine environments (Warwick and Light 2002; Alin and Cohen 2004; Kidwell 2007, 2013; Pyenson 2011; Weber and Zuschin 2013; Casey et al 2014; Korpanty and Kelley 2014; Hassan 2015; Zuschin and Ebner 2015; Archuby et al 2015; Smith and Dietl 2016; Powell et al 2017). Empirical studies, including modeling of repeatedly sampled living assemblages and geologic age dating of skeletal remains, demonstrate that death assemblages are time-averaged accumulations of individuals from many generations (e.g., Peterson 1976, 1977; Smol et al1984; Dixit et al 1989; reviews by Kidwell 2013; Kidwell and Tomašových 2013).…”

Section: Introductionmentioning

confidence: 99%

Testing for human impacts in the mismatch of living and dead ostracode assemblages at nested spatial scales in subtropical lakes from the Bahamian archipelago

Michelson¹,

Kidwell²,

Boush³

et al. 2018

Paleobiology

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Naturally time-averaged accumulations of skeletal remains—death assemblages—provide reliable, albeit temporally coarse, information on the species composition and structure of communities in diverse settings, and their mismatch with local living communities usually signals recent human-driven ecological change. Here, we present the first test of live–dead mismatch as an indicator of human stress using ostracodes. On three islands along a gradient of human population density in the Bahamas, we compared the similarity of living and death assemblages in 10 lakes with relatively low levels of human stress to live–dead similarity in 11 physically comparable lakes subject to industrial, agricultural, or other human activities currently or in the past. We find that live–dead agreement in pristine lakes is consistently excellent, boding well for using death assemblages in modern-day and paleolimnological biodiversity assessments. In most comparison of physically similar paired lakes, sample-level live–dead mismatch in both taxonomic composition and species’ rank abundance is on average significantly greater in the stressed lakes; live–dead agreement is not lower in all samples from stressed lakes, but is more variable. When samples are pooled for lake-level and island-level comparisons, stressed lakes still yield lower live–dead agreement, but the significance of the difference with pristine lakes decreases—species that occur dead-only (or alive-only) in one sample are likely to occur alive (or dead) in other samples. Interisland differences in live–dead agreement are congruent with, but not significantly correlated with, differences in human population density. This situation arises from heterogeneity in the timing and magnitudes of stresses and in the extent of poststress recovery. Live–dead mismatch in ostracode assemblages thus may be a reliable indicator of human impact at the sample level with the potential to be a widely applicable tool for identifying impacted habitats and, perhaps, monitoring the progress of their recovery.

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On the benefits of being redundant: low compositional fidelity of diatom death assemblages does not hamper the preservation of environmental gradients in shallow lakes

Cited by 16 publications

References 62 publications

Inferring skeletal production from time-averaged assemblages: skeletal loss pulls the timing of production pulses towards the modern period

Inferring skeletal production from time-averaged assemblages: skeletal loss pulls the timing of production pulses towards the modern period

La arqueología desde el microscopio. Aportes interdisciplinarios de las diatomeas a las problemáticas arqueológicas

Testing for human impacts in the mismatch of living and dead ostracode assemblages at nested spatial scales in subtropical lakes from the Bahamian archipelago

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