The biology and ecology of benthic foraminifera inhabiting intertidal mudflats
Abstract
Benthic foraminifera inhabiting the mudflats of the Eden Estuary, NE
Scotland, exhibited a single annual peak in abundance at both high (270
individuals 10 cm⁻²) and low shore (210 individuals 10 cm⁻²) intertidal sampling
stations during June 2000. The increased total abundance coincided with
reproduction in the two dominant foraminiferal species Elphidium williamsoni
(May) and Haynesina germanica (June) at both sites. Benthic diatom biomass,
measured as chlorophyll c, peaked at the high intertidal site during March and
April 2001 (36 and 37 mg m⁻², respectively) and at the low intertidal site in June 2000 (45 mg m⁻²). The high intertidal foraminiferal populations appeared to
display a lagged response to increases in chlorophyll c. Multivariate statistics
suggest that abiotic factors control the abundance of foraminifera at the high
intertidal site. At the low intertidal site, total foraminiferal abundance
demonstrated an almost immediate response to increased chlorophyll c and
multivariate statistics suggested biotic factors are more important in controlling
foraminiferal species abundance here.
Ingestion rates of ¹³C-labelled benthic diatoms over a five-day
experimental period were high (e.g. enrichment values for Elphidium were
recorded as 687 ± 121 % after 1 day) in intertidal benthic foraminifera.
Laboratory observations of E. williamsoni demonstrated rapid asexual
reproduction (within 3 days) and growth rates of up to 14 µm day⁻¹ were
estimated.
Three benthic foraminiferal species E. williamsoni, H. germanica and E.
oceanensis ingest motile benthic diatoms as a food resource on the intertidal
mudflats of the Eden Estuary. Novel application of natural abundance stable
isotope (δ¹³C and δ¹⁵N) techniques demonstrated the trophic position of intertidal
benthic foraminifera, confirming that they largely ingest and assimilate organic
matter derived from benthic diatoms. Foraminifera have largely been overlooked
in meiofaunal studies, but play a significant role in the rapid transfer of
autotrophic carbon to higher trophic levels within benthic marine food webs.
Type
Thesis, PhD Doctor of Philosophy
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