Ecology and nutrition of the large agglutinated foraminiferan Bathysiphon capillare in the bathyal NE Atlantic: distribution within the sediment profile and lipid biomarker composition

Abstract

The large agglutinated foraminiferan Bathysiphon capillare de Folin (Protista) was an important component of the macrofauna in box core samples recovered at a 950 m site on the southern flank of the Wyville-Thomson Ridge, northern Rockall Trough. The long, narrow, very smooth, flexible tubes of B. capillare reached a maximum length of almost 10 cm. Densities ranged from 100 to 172 ind. m -2 , a figure that represents at least 5 to 9% of metazoan macrofaunal densities. This infaunal species usually adopted a more or less horizontal orientation within the upper 5 cm layer of brownish sandy silt. Its cytoplasm yielded a diverse spectrum of fatty acids. These included various monounsaturated fatty acids (39% of total), mainly 18:1(n-7), 20:1(n-9) and 22:1(n-7), the polyunsaturated fatty acids (PUFA) 20:4(n-6), 20.5(n-3) and 22.6(n-3), and non-methylene diene-interrupted fatty acids (NMIDS), particularly 22:2∆7,13 and 22:2∆7,15. The spectrum of PUFAs is consistent with the ingestion by B. capillare of phytodetrital material. However, the presence of NMIDS, reported here for the first time in a protist, provides evidence for a substantial bacterial component in the diet. Viewed by scanning electron microscopy (SEM), the cytoplasm occupied a narrow space between the inner organic test lining and an inner core of detritus around which it formed a sheath. The core material included numerous spherical structures (2 to 10 µm diameter) that we interpret as stercomata (waste pellets composed largely of mineral grains). Taken together, our observations suggest that B. capillare is a deposit feeder, consuming sediment, detritus and associated bacteria. Other deep infaunal foraminiferans probably have a similar diet, leading us to speculate that these protists, which are often abundant in dysoxic settings, may contribute significantly to carbon cycling in the deep sea. Since B. capillare and similar large Bathysiphon species can be recovered in good condition from bathyal depths, they may prove to be ideal experimental subjects for addressing some fundamental issues in the lipid biochemistry of deep-sea benthic organisms.

Uptake of algal carbon and the likely synthesis of an "essential" fatty acid by <i>Uvigerina</i> ex. gr. <i>semiornata</i> (Foraminifera) within the Pakistan margin oxygen minimum zone: evidence from fatty acid biomarker and <sup>13</sup>C tracer experiments

“…We expect that the 13 C content would increase during a longer experiment. Many benthic foraminifera contain high amounts of this "essential" fatty acid (Gooday et al, 2002, Suhr et al, 2008, which is also dominant in deep-sea echinoderms (Howell et al, 2003, Hudson et al, 2004. It is possible that particular biomechanical properties of 20:4(n-6) facilitate life at increased hydrostatic pressures.…”

“…semiornata actively synthesised 20:4(n-6) during the experiments. This "essential" polyunsaturated fatty acid is often extremely abundant in deep-sea organisms, particularly foraminifera (Gooday et al, 2002, Suhr et al, 2008), yet its origins and functions in this environment remain unclear. The evidence presented here suggests that foraminifera could possibly be a major source of 20:4(n-6) in benthic ecosystems, with important consequences for the supply of this "essential" dietary nutrient to higher trophic levels.…”

Global bathymetric patterns of standing stock and body size in the deep-sea benthos

“…Deep-sea foraminiferans are an abundant, diverse and ecologically important group (Levin et al 1991, Bernhard 1992, Gooday et al 1998. Some species reach macro-or even megafaunal dimensions (Gooday et al 2002), but most are meiofaunal in size, and foraminiferans are often grouped with the meiofauna. There are very few measurements of foraminiferan biomass.…”

Selective agglutination of tourmaline grains by foraminifera in a deep-water flysch environment (Eocene Hieroglyphic beds, Silesian Nappe, Polish Outer Carpathians)

“…On the other hand, Recurvoides, Trochamminoides and Paratrochamminoides, which oc cur in sim i lar num bers in the as sem blage, se lect tourma line grains much less of ten in spite of the fact that, be ing actively mo bile on the sur face and within sed i ment, they have eas ier ac cess to this test-build ing de tri tal com po nent. Also, rela tively low pro por tion of Bathysiphon in cor po rate tour ma line grains, but they ag glu ti nate in or ganic par ti cles and var i ous non-quartz min eral com po nents rel a tively of ten (Dick, 1928;Bruce et al, 1981;Gooday nad Claugher, 1989;Gooday et al, 1995bGooday et al, , 2002Cole and Val en tine, 2006).…”

“…Quartz grains con sti tute the most com mon de tri tal compo nent, but there are also tests com posed, partly or en tirely, of or ganic ma te rial, i.e. coccolihts, sponge spicules, tests of other foraminifera, di a toms, radio lar ians, or fine frag ments of bi valve tests (Smith and Kaesler, 1970;Tendal et al, 1982;Commeau et al, 1985;Cart wright et al, 1989;Gooday and Claugher, 1989;Gooday et al, 1995aGooday et al, , 2002Gooday et al, , 2010Allen et al, 1999;Gooday and Smart, 2000; Thom sen and Ras mus sen, 2008 and ref er ences therein). Be sides quartz, the fol low ing in or ganic de tri tal com po nents are ob served in the foraminifera test walls: cal cite, ar agon ite, do lo mite, glauconite, feld spars, micas, pyroxene, hornblende, mag ne tite, py rite as well as other heavy min er als, e.g.…”