Mesocosm and Microcosm Experiments On the Feeding of Temperate Salt Marsh Foraminifera

Abstract

Agglutinated foraminifera dominate in temperate salt marsh sediment, making them key indicators for monitoring sea level and environmental changes. Little is known about the biology of these benthic foraminifera because of difficulties in distinguishing live from dead specimens in laboratory cultures. We present data from 10 years of laboratory experiments using comparisons of the agglutinant trochamminids Trochammina inflata and Entzia macrescens and the miliolid Miliammina fusca with the calcareous rotalids Helenina anderseni and Elphidium williamsoni. Specimens were taken from a laboratory mesocosm representing Chezzetcook Inlet, a cool-temperate salt marsh in eastern Canada. We determined culture requirements for the agglutinated foraminifera in Petri dishes over 10–12 week periods. Five inexpensive, non-terminal ways of identifying live organisms were developed: spatial movement, detritus-gathering, attachment, clustering, and test opacity. Comparison with rose Bengal staining showed <10% diversion for calcareous species and T. inflata but M. fusca was over-counted by >30%. Terminal chambers of Trochammina inflata were examined by transmission electron microscopy to visualise food consumption and identify food in digestive vacuoles, both in specimens from mesocosm and in culture. Bacteria and unidentified detritus in the vacuoles establish that this agglutinated species is a saprophagous and bacterivorous detritivore. The adhesive secretions by these species apparently help them gather and possibly farm food while being relatively immobile in the sediments. Our observations of movement and feeding orientation in the agglutinants suggest links between form and function that underscore their value as ultra high resolution sea-level proxies. Mesocosm biomass and abundance counts show that foraminifera represent >50% of the meiofaunal biomass, emphasising their importance in the food web and energy-flow dynamics of temperate salt marsh systems.

Deposit feeding of a foraminifera from an Arctic methane seep site and possible association with a methanotroph revealed by transmission electron microscopy

“…The bacteria observed in the degradation vacuoles resembled those from other deep-sea foraminifera (Globobulimina pacifica and Uvigerina peregrina) and the shallow-dwelling genus Ammonia (Goldstein and Corliss, 1994). Salt-marsh foraminifera also feed on bacteria and detritus, as observed in TEM studies (Frail-Gauthier et al, 2019). Scavenging on bacteria has also been observed by other foraminifera from intertidal environments such as Ammonia tepida or Haynesina germanica (Pascal et al, 2008) and is a logical consequence from detritus feeding.…”

Deposit-feeding of Nonionellina labradorica (foraminifera) from an Arctic methane seep site and possible association with a methanotroph

“…From this result, however, we infer that N. labradorica at this site is a deposit feeder, feeding on organic detritus and associated bacteria. The bacteria observed in the degradation vacuoles resembled those from other deep-sea foraminifera (Globobulimina pacifica and Uvigerina peregrina) and the shallow-dwelling genus Ammonia (Goldstein and Corliss, 1994). Salt-marsh foraminifera also feed on bacteria and detritus, as observed in TEM studies (Frail-Gauthier et al, 2019).…”

“…The bacteria observed in the degradation vacuoles resembled those from other deep-sea foraminifera (Globobulimina pacifica and Uvigerina peregrina) and the shallow-dwelling genus Ammonia (Goldstein and Corliss, 1994). Salt-marsh foraminifera also feed on bacteria and detritus, as observed in TEM studies (Frail-Gauthier et al, 2019). Scavenging on bacteria has also been observed by other foraminifera from intertidal environments such as Ammonia tepida or Haynesina germanica (Pascal et al, 2008) and is a logical consequence of detritus feeding.…”

“…clay) and associated bacteria, organic detritus (dead particulate organic material), and, if present, diatom cells using their pseudopodia. Based on the ultrastructure of the diet found in vacuoles several species of foraminifera from different habitats have already been classified to be deposit feeders (Goldstein and Corliss, 1994).…”

Foraminiferal Sea-Level Reconstructions From Major New Zealand Cities: Implications for Long-Term Vertical Land Movement Trends from Centennial Baselines

“…This zonation typically becomes tighter in the higher part of the marsh (Gehrels, 1994;Scott et al, 2001;Chen et al, 2020), making the high salt marsh environment ideal for the precise reconstruction of past relative sea levels. Foraminifera are also extremely abundant in salt-marsh environments, where they typically account for 24-75% of the meiofaunal biomass (Frail-Gauthier et al, 2019). Diatoms, a group of siliceous testate algae, are also sometimes used for transfer function-based sea-level research, though unlike foraminifera their uppermost limit is not constrained to the zones of tidal reach (Gehrels et al, 2001).…”