Patterns in cumulative increase in live and dead species from foraminiferal time series of Cowpen Marsh, Tees Estuary, UK: Implications for sea-level studies

Abstract

We have collected live and dead foraminiferal times-series data at 2-weekly intervals for a 12-month period from the intertidal zone of Cowpen Marsh, Tees Estuary, UK. The data from the 689 samples show profound differences between live and dead assemblages, although assemblages are dominated by just three species, Haynesina germanica, Jadammina macrescens and Trochammina inflata, which represent over 70% of the assemblage. The cumulative increase in species of most environments approximates to a lognormal or log series. None of the datasets show a broken stick pattern. The cumulative maximum number of species, which represents the species carrying capacity of the environment, is recorded earlier in the life assemblages than the dead counterparts. The dead assemblage of Cowpen Marsh is found to have a higher abundance (435 compared to 163 individuals/10 cm 3 ) and number of species (52 compared to 28) than its live counterpart because the dead assemblage represents many generations added over a long period of time. In contrast, some species are recorded in the live dataset that were not found in the dead assemblage, indicating the dead record is either incomplete (e.g. taphonomic change) or inadequately sampled.We investigated the influence of patterns in cumulative increase on dead assemblages for sea-level reconstructions through the development of foraminiferal-based transfer functions. The cumulative transfer functions suggest that the performance improves during the first six sample intervals of the time-series dataset with reconstruction differing by 1.2 m and remains constant thereafter. AbstractWe have collected live and dead foraminiferal times-series data at two-weekly intervals for a twelve-month period from the intertidal zone of Cowpen Marsh, Tees Estuary, UK. The data from the 689 samples show profound differences between live and dead assemblages, although assemblages are dominated by just three species, Haynesina germanica, Jadammina macrescens and Trochammina inflata, which represent over 70% of the assemblage. The cumulative increase in species of most environments approximates to a log normal or log series. None of the datasets show a broken stick pattern. The cumulative maximum number of species, which represents the species carrying capacity of the environment, is recorded earlier in the life assemblages than the dead counterparts. The dead assemblage of Cowpen Marsh is found to have a higher abundance (435 compared to 163 individuals/10cm 3 ) and number of species (52 compared to 28) than its live counterpart because the dead assemblage represents many generations added over a long period of time. In contrast, some species are recorded in the live dataset that were not found in the dead assemblage, indicating the dead record is either incomplete (e.g. taphonomic change) or inadequately sampled.We investigated the influence of patterns in cumulative increase on dead assemblages for sealevel reconstructions through the development of foraminiferal-based transfer functions. The cumul...

Biodiversity and community structure of deep-sea foraminifera around New Zealand

“…The samples are grouped into four areas, located off the north, west, east and south coasts of the two main islands (North and South Islands) of New Zealand (Fig. 1) Horton and Murray (2006) discuss the advantages and disadvantages of using each of these populations. Ideally, observation of the living population over a considerable period of time is required to assess the vicissitudes of seasonal and yearly fluctuations, and only through use of the living population can we be certain that transport or other kinds of taphonomic loss or gain did not influence the dead or total population.…”

The input of foraminiferal infaunal populations to sub-fossil assemblages along an elevational gradient in a salt marsh: application to sea-level studies in the mid-Atlantic coast of North America

“…sub-fossil assemblages Briefly, living foraminifera accumulate through time forming the death assemblage. The death assemblage is considered to represent a time-averaged accumulation of foraminiferal tests (Murray, 1991;Horton & Murray, 2006) and is used as modern analogue for paleoenvironmental reconstructions (see also Murray, 2000). These dead remains can, however, undergo physical and/or biological reworking and may either be destroyed or remain in the uppermost layer as the death assemblage forms.…”

Seasonal Differences in Live Foraminiferal Densities: Case Studies from Tropical and Temperate Intertidal Environments

“…The dead counts from Cowpen marsh and Brancaster marsh were used since an analysis by Benjamin Horton and John Murray [21] to determined dead counts to better represent average annual conditions.…”