Calcareous dissolution of deep-sea benthonic foraminifera
confirmed once again the existence of a wide convergence zone in the southwest Atlantic Ocean (Boltovskoy 1966, 1970, 1978).
References Boltovskoy, E. 1966. La zona de Convergencla SubtropicaliSubantártica en el Océano Atlántico (parte occidental) (Un estudio en base a
Calcareous dissolution of deep-sea benthonic foraminifera BRUCE H. CORLISS
and
SUSUMU
la investigación de ForaminIferos indicadores) (Publication H. 1015). Buenos Aires: Argentina Servicio de Hidrografia Naval. Boltovskoy, E. 1970. Masas de agua (caracterIstica, distribución, movimientos) en la superficie del Atlántico suboeste, segiIn indicadores biológicos—ForaminIferos (Publication H. 643). Buenos Aires: Argentina Servicio de Hidrografia Naval, Boltovskoy, E. 1978. Problema de los indicadores biológicos en OceanografIa. Anales de la Academia Nacional de Ciencias Exactas, FIsicas y Naturales, Buenos Aires, 30, 229-251.
Little attention has been given to the effect of carbonate dissolution on calcareous deep-sea benthonic foraminifera other than the observation by many workers that benthonic foraminifera are more resistant than planktonic foraminifera to carbonate dissolution. One of the complicating factors in studying calcareous deep-sea benthonic foraminifera in the southern ocean is the presence of highly corrosive Antarctic Bottom Water, which may influence the faunal distribution patterns by differentially removing solution-susceptible spe-
HoNjo
Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543
SALINITY (%) 3420 3430 3440 3450 3460 3470 3480 3490i SAMPLE NUMBER I and TEMPERATURE (°C) DEPTH(m_40 -30 250 300 400 0 0 5 0 10 0 15 0 200 NORTH ' PACIFIC CENTRAL WATER
cj
-20
I i3O6 2 378
.
Oh
% BROKEN BENTHONIC FORAMINIFERA -10 0 01 02 03 04 0 50 100 -
3 11978 NORTH PACIFIC INTERMEDIATE WATER
- 2000
Nt PACIFIC DEEP WATER
S(%0)
2778
3000
3978
4000
6 5000
4278
4878
9i,5582 10
Figure 1. Temperature, salinity, and 141 data from GEOSECS (Geochemical Ocean Sections Study) station 235, together with dissolution sample number and percentage of broken benthonic foraminiferal tests per sample vs. water depth (Corliss and Honjo In press). 141is an Index of undersaturation with respect to calcite. Note the different scales for 141 above and below zero. Negative values Indicate supersaturation of calcium carbonate (CaCO1), zero is saturation, and positive values indicate undersaturatlon of CaCO1. In this region, the upper 500 meters are supersaturated, with undersaturation increasing steadily below this level.
1981 REVIEW
133
cies. We describe in this article a dissolution experiment involving nine species of benthonic foraminifera on a 5,792meter mooring in the central North Pacific (Corliss and Honjo in press). The purposes of the experiment were (1) to determine the influence of carbonate dissolution on benthonic foraminiferal tests and (2) to establish the relative susceptibility of the nine species. Ten dissolution samples with approximately six specimens each of eight common deep-sea benthonic foraminifera and one shallow-water species were placed on a 5,792-meter PARFLUX (Particle Flux Study) P 1 sediment trap mooring (Honjo 1980) in the central North Pacific (15°21.1'N 151°28.5'W) and exposed to seawater at nine different depths on the mooring (figure 1) for 61 days between September and October 1978. (Two samples were located in water 5,582 meters deep.) The eight deep-sea species, all common in the southern ocean (Corliss 1979), were: Cibicidoides kullenbergi (Parker), Epistominella umbonifera (Cushman), Gyroidinoides orbicularis (d'Orbigny), Gyroidinoides soldanii (d'Orbigny), Hoeglundina elegans (d'Orbigny), Oridorsalis tener (Brady), Planulina wuellerstorfi (Schwager), and Pyrgo murrhina (Schwager). The shallow-water species, Amphistegina sp., was included in the experiment to determine the susceptibility of a porous, shallow-water species. All specimens were greater than 250 micrometers in diameter and in good condition, with no chamber, breakage and shiny surface textures. The sequential modification of the test ultrastructure of E. umbonifera is presented in figure 2 as an example of the results of the experiment. This species, a dominant species in the deep sea, is found throughout the southern ocean and is associated with cold Antarctic Bottom Water (Corliss 1979, in preparation). The sequence of modification in E. umbonifera is: (1) corrosion of test surface, which creates dull surface textures; (2) smoothing of the surface; (3) pitting of the surface, resulting in uneven surface textures; and (4) breakage of the chambers and extensive corrosion of the remaining surfaces, resulting in a highly irregular surface texture. The sequence of modification of E. umbonifera is similar to that of the other hyaline trochospiral species. The modification of P. murrhina is slightly different due to biloculine coiling of
the test. Initial corrosion of the surface layer is associated with the development of cracks, holes, and dull surface textures. Removal of the chamber wall follows, generally without any observable intermediate steps. As each chamber is removed, the preceding chamber is exposed in good condition and the dissolution sequence begins again. The susceptibilities to carbonate dissolution of the nine benthonic foraminifera vary considerably. A ranking of their relative susceptibilities shows that Amphistegina sp. is the most susceptible to dissolution, followed by P. murrhina, P. wuellerstorfi, a group of four species (C. kullenbergi, E. umbonifera, H. elegans, and 0. tener), and finally, G. orbicularis and G. soldanii. The susceptibility ranking shows that E. umbonifera is as susceptible to dissolution as C. kullenbergi, H. elegans, and 0. tener and more susceptible than Gyroidinoides spp. This indicates that it is unlikely that dissolution has a major role in preferentially concentrating E. umbonifera within the depth range where calcareous benthonic foraminifera are found, since E. umbonifera is as susceptible to dissolution as many of the other species. However, this study has not considered all of the major deep-sea species, and the effect of dissolution on deep-sea assemblages would depend somewhat on the composition of the faunal assemblage and the resistance to dissolution of the individual species present. This work was supported by National Science Foundation grant DPP 78-21105 to Bruce H. Corliss and grant OCE 77-27080 to Susumu Honjo. References Corliss, B. H. 1979. Taxonomy of Recent deep-sea benthonic foraminifera from the southeast Indian Ocean. Micropaleontology, 25(1), 1-19. Corliss, B. H. In preparation. Distribution of Recent deep-sea benthonic foraminifera from the southwest Indian Ocean. Corliss, B. H., and Honjo, S. In press. Dissolution of deep-sea benthonic foraminifera. Micropaleontology. Honjo, S. 1980. Material fluxes and modes of sedimentation in the mesopelagic and bathypelagic zones. Journal of Marine Research, 38(1), 53-97.
Figure 2. Sequential modification of Epistominella umbonifera by calcium carbonate dissolution (Corliss and Honjo in press). Photographs (1) through (5) Illustrate the condition of the specimens before the experiment, including two closeup photographs taken at random locations on the umbilical and spiral sides of the test. (1) umbilical view (b OX); (2) closeup of (1)(625X); (3) spiral view (94X); (4) closeup of (3)(625X); (5) edge view (175X); (6) sample 1 (87X), 306 meters; (7) sample 4 (94X), umbilical side, with circular cracks developed near aperture taken at depth of 2,778 meters; (8) closeup of (7) showing surface in good condition (525X); (9) sample 4 (525X), closeup of spiral side showing surface composed of interlocking crystals surrounding pores; (10) sample 5 (68X), initial effects of erosion shown with large crystals standing out in central region, 3,978 meters; (11) sample 5 (525X), closeup of spiral side showing surface of test smooth compared with (9), with no dissolution modification, 3,978 meters; (12) closeup of central region of (10) showing large crystals (525X); (13) sample 7 (89X), spiral side, showing pitting of tests and extensive erosion which created an irregular surface texture, 4,878 meters; (14) sample 10 (87X), spiral side, showing erosion of surface and extensive breakage of chambers, 5,590 meters; (15) closeup of (14) showing highly Irregular surface texture (525X).
134
ANTARCTIC JOURNAL
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References Boltovskoy, E. 1966. La zona de Convergencla SubtropicaliSubantártica en el Océano Atlántico (parte occidental) (Un estudio en base a
Calcareous dissolution of deep-sea benthonic foraminifera BRUCE H. CORLISS
and
SUSUMU
la investigación de ForaminIferos indicadores) (Publication H. 1015). Buenos Aires: Argentina Servicio de Hidrografia Naval. Boltovskoy, E. 1970. Masas de agua (caracterIstica, distribución, movimientos) en la superficie del Atlántico suboeste, segiIn indicadores biológicos—ForaminIferos (Publication H. 643). Buenos Aires: Argentina Servicio de Hidrografia Naval, Boltovskoy, E. 1978. Problema de los indicadores biológicos en OceanografIa. Anales de la Academia Nacional de Ciencias Exactas, FIsicas y Naturales, Buenos Aires, 30, 229-251.
Little attention has been given to the effect of carbonate dissolution on calcareous deep-sea benthonic foraminifera other than the observation by many workers that benthonic foraminifera are more resistant than planktonic foraminifera to carbonate dissolution. One of the complicating factors in studying calcareous deep-sea benthonic foraminifera in the southern ocean is the presence of highly corrosive Antarctic Bottom Water, which may influence the faunal distribution patterns by differentially removing solution-susceptible spe-
HoNjo
Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543
SALINITY (%) 3420 3430 3440 3450 3460 3470 3480 3490i SAMPLE NUMBER I and TEMPERATURE (°C) DEPTH(m_40 -30 250 300 400 0 0 5 0 10 0 15 0 200 NORTH ' PACIFIC CENTRAL WATER
cj
-20
I i3O6 2 378
.
Oh
% BROKEN BENTHONIC FORAMINIFERA -10 0 01 02 03 04 0 50 100 -
3 11978 NORTH PACIFIC INTERMEDIATE WATER
- 2000
Nt PACIFIC DEEP WATER
S(%0)
2778
3000
3978
4000
6 5000
4278
4878
9i,5582 10
Figure 1. Temperature, salinity, and 141 data from GEOSECS (Geochemical Ocean Sections Study) station 235, together with dissolution sample number and percentage of broken benthonic foraminiferal tests per sample vs. water depth (Corliss and Honjo In press). 141is an Index of undersaturation with respect to calcite. Note the different scales for 141 above and below zero. Negative values Indicate supersaturation of calcium carbonate (CaCO1), zero is saturation, and positive values indicate undersaturatlon of CaCO1. In this region, the upper 500 meters are supersaturated, with undersaturation increasing steadily below this level.
1981 REVIEW
133
cies. We describe in this article a dissolution experiment involving nine species of benthonic foraminifera on a 5,792meter mooring in the central North Pacific (Corliss and Honjo in press). The purposes of the experiment were (1) to determine the influence of carbonate dissolution on benthonic foraminiferal tests and (2) to establish the relative susceptibility of the nine species. Ten dissolution samples with approximately six specimens each of eight common deep-sea benthonic foraminifera and one shallow-water species were placed on a 5,792-meter PARFLUX (Particle Flux Study) P 1 sediment trap mooring (Honjo 1980) in the central North Pacific (15°21.1'N 151°28.5'W) and exposed to seawater at nine different depths on the mooring (figure 1) for 61 days between September and October 1978. (Two samples were located in water 5,582 meters deep.) The eight deep-sea species, all common in the southern ocean (Corliss 1979), were: Cibicidoides kullenbergi (Parker), Epistominella umbonifera (Cushman), Gyroidinoides orbicularis (d'Orbigny), Gyroidinoides soldanii (d'Orbigny), Hoeglundina elegans (d'Orbigny), Oridorsalis tener (Brady), Planulina wuellerstorfi (Schwager), and Pyrgo murrhina (Schwager). The shallow-water species, Amphistegina sp., was included in the experiment to determine the susceptibility of a porous, shallow-water species. All specimens were greater than 250 micrometers in diameter and in good condition, with no chamber, breakage and shiny surface textures. The sequential modification of the test ultrastructure of E. umbonifera is presented in figure 2 as an example of the results of the experiment. This species, a dominant species in the deep sea, is found throughout the southern ocean and is associated with cold Antarctic Bottom Water (Corliss 1979, in preparation). The sequence of modification in E. umbonifera is: (1) corrosion of test surface, which creates dull surface textures; (2) smoothing of the surface; (3) pitting of the surface, resulting in uneven surface textures; and (4) breakage of the chambers and extensive corrosion of the remaining surfaces, resulting in a highly irregular surface texture. The sequence of modification of E. umbonifera is similar to that of the other hyaline trochospiral species. The modification of P. murrhina is slightly different due to biloculine coiling of
the test. Initial corrosion of the surface layer is associated with the development of cracks, holes, and dull surface textures. Removal of the chamber wall follows, generally without any observable intermediate steps. As each chamber is removed, the preceding chamber is exposed in good condition and the dissolution sequence begins again. The susceptibilities to carbonate dissolution of the nine benthonic foraminifera vary considerably. A ranking of their relative susceptibilities shows that Amphistegina sp. is the most susceptible to dissolution, followed by P. murrhina, P. wuellerstorfi, a group of four species (C. kullenbergi, E. umbonifera, H. elegans, and 0. tener), and finally, G. orbicularis and G. soldanii. The susceptibility ranking shows that E. umbonifera is as susceptible to dissolution as C. kullenbergi, H. elegans, and 0. tener and more susceptible than Gyroidinoides spp. This indicates that it is unlikely that dissolution has a major role in preferentially concentrating E. umbonifera within the depth range where calcareous benthonic foraminifera are found, since E. umbonifera is as susceptible to dissolution as many of the other species. However, this study has not considered all of the major deep-sea species, and the effect of dissolution on deep-sea assemblages would depend somewhat on the composition of the faunal assemblage and the resistance to dissolution of the individual species present. This work was supported by National Science Foundation grant DPP 78-21105 to Bruce H. Corliss and grant OCE 77-27080 to Susumu Honjo. References Corliss, B. H. 1979. Taxonomy of Recent deep-sea benthonic foraminifera from the southeast Indian Ocean. Micropaleontology, 25(1), 1-19. Corliss, B. H. In preparation. Distribution of Recent deep-sea benthonic foraminifera from the southwest Indian Ocean. Corliss, B. H., and Honjo, S. In press. Dissolution of deep-sea benthonic foraminifera. Micropaleontology. Honjo, S. 1980. Material fluxes and modes of sedimentation in the mesopelagic and bathypelagic zones. Journal of Marine Research, 38(1), 53-97.
Figure 2. Sequential modification of Epistominella umbonifera by calcium carbonate dissolution (Corliss and Honjo in press). Photographs (1) through (5) Illustrate the condition of the specimens before the experiment, including two closeup photographs taken at random locations on the umbilical and spiral sides of the test. (1) umbilical view (b OX); (2) closeup of (1)(625X); (3) spiral view (94X); (4) closeup of (3)(625X); (5) edge view (175X); (6) sample 1 (87X), 306 meters; (7) sample 4 (94X), umbilical side, with circular cracks developed near aperture taken at depth of 2,778 meters; (8) closeup of (7) showing surface in good condition (525X); (9) sample 4 (525X), closeup of spiral side showing surface composed of interlocking crystals surrounding pores; (10) sample 5 (68X), initial effects of erosion shown with large crystals standing out in central region, 3,978 meters; (11) sample 5 (525X), closeup of spiral side showing surface of test smooth compared with (9), with no dissolution modification, 3,978 meters; (12) closeup of central region of (10) showing large crystals (525X); (13) sample 7 (89X), spiral side, showing pitting of tests and extensive erosion which created an irregular surface texture, 4,878 meters; (14) sample 10 (87X), spiral side, showing erosion of surface and extensive breakage of chambers, 5,590 meters; (15) closeup of (14) showing highly Irregular surface texture (525X).
134
ANTARCTIC JOURNAL
r Kr
1 2 0
d
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r;
-T
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3
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.---
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