The response of benthic foraminifera to productivity cycles in the eastern equatorial Pacific: Faunal and geochemical constraints on glacial bottom water oxygen levels

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal-induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

Download Full-text

Shift in biotic response of abyssal benthic foraminifera since MIS 7 in the eastern equatorial Pacific Ocean

Geosciences Journal ◽

10.1007/s12303-011-0031-y ◽

2011 ◽

Vol 15 (4) ◽

pp. 417-422 ◽

Cited By ~ 2

Author(s):

Hiroyuki Takata ◽

Boo-Keun Khim ◽

Chan Min Yoo ◽

Sang-Bum Chi

Keyword(s):

Pacific Ocean ◽

Benthic Foraminifera ◽

Equatorial Pacific ◽

Equatorial Pacific Ocean ◽

Biotic Response ◽

Eastern Equatorial Pacific ◽

Eastern Equatorial Pacific Ocean

Download Full-text

I/Ca in epifaunal benthic foraminifera: A semi-quantitative proxy for bottom water oxygen in a multi-proxy compilation for glacial ocean deoxygenation

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2019.116055 ◽

2020 ◽

Vol 533 ◽

pp. 116055 ◽

Cited By ~ 3

Author(s):

Wanyi Lu ◽

Rosalind E.M. Rickaby ◽

Babette A.A. Hoogakker ◽

Anthony E. Rathburn ◽

Ashley M. Burkett ◽

...

Keyword(s):

Benthic Foraminifera ◽

Bottom Water ◽

Water Oxygen ◽

Ocean Deoxygenation

Download Full-text

Abyssal benthic foraminifera in the eastern equatorial Pacific (IODP EXP 320) during the middle Eocene

Journal of Paleontology ◽

10.1666/12-107 ◽

2013 ◽

Vol 87 (6) ◽

pp. 1160-1185 ◽

Cited By ~ 5

Author(s):

Hiroyuki Takata ◽

Ritsuo Nomura ◽

Akira Tsujimoto ◽

Boo-Keun Khim ◽

Ik Kyo Chung

Keyword(s):

Water Depth ◽

Benthic Foraminifera ◽

Middle Eocene ◽

Accumulation Rate ◽

Equatorial Pacific ◽

Equatorial Pacific Ocean ◽

Ocean Drilling Program ◽

Integrated Ocean Drilling Program ◽

Eastern Equatorial Pacific ◽

Study Interval

We report on the faunal transition of benthic foraminifera during the middle Eocene at Site U1333 (4862 m water depth, 3,560–3,720 m paleo-water depth) of Integrated Ocean Drilling Program Expedition 320 in the eastern equatorial Pacific Ocean. During the period ∼41.5–40.7 Ma, which includes carbonate accumulation event 3 (CAE-3), the benthic foraminiferal accumulation rate (BFAR) increased gradually and then it declined rapidly. In contrast, BFAR was considerably lower during ∼40.7–39.4 Ma, corresponding to the middle Eocene climatic optimum (MECO), and then it increased during ∼39.3–38.4 Ma, including CAE-4. Diversity (E [S200]) was slightly lower in the upper part of the study interval than in the lower part. The most common benthic foraminifera were Nuttallides truempyi, Oridorsalis umbonatus, and Gyroidinoides spp. in association with Globocassidulina globosa and Cibicidoides grimsdalei during the period studied. Quadrimorphina profunda occurred abundantly with N. truempyi, O. umbonatus, and G. globosa during ∼39.4–38.4 Ma, including CAE-4, although this species was also relatively common in the lower part of the study interval. Virgulinopsis navarroanus and Fursenkoina sp. A, morphologically infaunal taxa, were common during ∼38.8–38.4 Ma, corresponding to the late stage of CAE-4. Based on Q-mode cluster analysis, four sample clusters were recognized and their stratigraphic distributions were generally discriminated in the lower and upper parts of the study interval. Thus, there was only a small faunal transition in the abyssal eastern equatorial Pacific during the middle to late-middle Eocene. The faunal transition recognized in this study may be related to recovery processes following intense carbonate corrosiveness in the eastern equatorial Pacific during MECO.

Download Full-text

Coastal hypoxia and sediment biogeochemistry

Biogeosciences Discussions ◽

10.5194/bgd-6-3655-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 3655-3706 ◽

Cited By ~ 29

Author(s):

J. J. Middelburg ◽

L. A. Levin

Keyword(s):

Organic Matter ◽

Bottom Water ◽

Water Exchange ◽

Transport Processes ◽

Ecosystem Dynamics ◽

Ecosystem Functions ◽

Oxygen Levels ◽

Concise Review ◽

Water Oxygen ◽

Sediment Biogeochemistry

Abstract. The intensity, duration and frequency of coastal hypoxia (oxygen concentration <63 μM) are increasing due to human alteration of coastal ecosystems and changes in oceanographic conditions due to global warming. Here we provide a concise review of the consequences of coastal hypoxia for sediment biogeochemistry. Changes in bottom-water oxygen levels have consequences for early diagenetic pathways (more anaerobic at expense of aerobic pathways), the efficiency of re-oxidation of reduced metabolites and the nature, direction and magnitude of sediment-water exchange fluxes. Hypoxia may also lead to more organic matter accumulation and burial and the organic matter eventually buried is also of higher quality, i.e. less degraded. Bottom-water oxygen levels also affect the organisms involved in organic matter processing with the contribution of metazoans decreasing as oxygen levels drop. Hypoxia has a significant effect on benthic animals with the consequences that ecosystem functions related to macrofauna such as bio-irrigation and bioturbation are significantly affected by hypoxia as well. Since many microbes and microbial-mediated biogeochemical processes depend on animal induced transport processes (e.g. re-oxidation of particulate reduced sulphur and denitrification), there are indirect hypoxia effects on biogeochemistry via the benthos. Severe long-lasting hypoxia and anoxia may result in the accumulation of reduced compounds in sediments and elimination of macrobenthic communities with the consequences that biogeochemical properties during trajectories of decreasing and increasing oxygen may be different (hysteresis) with consequences for coastal ecosystem dynamics.

Download Full-text

Records of past mid-depth ventilation: Cretaceous ocean anoxic event 2 vs. Recent oxygen minimum zones

Biogeosciences ◽

10.5194/bg-12-1169-2015 ◽

2015 ◽

Vol 12 (4) ◽

pp. 1169-1189 ◽

Cited By ~ 10

Author(s):

J. Schönfeld ◽

W. Kuhnt ◽

Z. Erdem ◽

S. Flögel ◽

N. Glock ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Bottom Water ◽

Carbon Accumulation ◽

Marine Biota ◽

Accumulation Rates ◽

Oxygen Minimum Zones ◽

Oxygen Levels ◽

Water Oxygen ◽

Oxygen Minimum

Abstract. Present day oceans are well ventilated, with the exception of mid-depth oxygen minimum zones (OMZs) under high surface water productivity, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or anoxic. The Cretaceous ocean anoxic events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossils preserved in the sedimentary record. Yet assessments of the intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life have been studied thoroughly. Their implications for constraining past bottom-water oxygenation are addressed in this review. We compared OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the north-west African shelf. Holocene laminated sediments are encountered at bottom-water oxygen levels of < 7 μmol kg−1 under the Peruvian upwelling and < 5 μmol kg−1 in California Borderland basins and the Pakistan Margin. Seasonal to decadal changes of sediment input are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg−1. Chondrites has not been reported in Peruvian sediments but centimetre-sized crab burrows appeared around 10 μmol kg−1, which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation rates ranged from 0.7 and 2.8 g C cm−2 kyr−1 in laminated OAE 2 sections in Tarfaya Basin, Morocco, matching late Holocene accumulation rates of laminated Peruvian sediments under Recent oxygen levels below 5 μmol kg−1. Sediments deposited at > 10 μmol kg−1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In the absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of palaeo-oxygenation. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions.

Download Full-text

Benthic Foraminifera from Middle to Late Pleistocene, coastal upwelling sediments of ODP Hole 686B, Pacific Ocean, off Peru

Journal of Micropalaeontology ◽

10.1144/jm.9.2.153 ◽

1991 ◽

Vol 9 (2) ◽

pp. 153-158 ◽

Cited By ~ 3

Author(s):

Kathryn A. Malmgren ◽

Brian M. Funnell

Keyword(s):

Late Pleistocene ◽

Surface Waters ◽

Benthic Foraminifera ◽

Bottom Water ◽

Coastal Upwelling ◽

Oxygen Minimum Zone ◽

Water Oxygen ◽

Minimum Zone ◽

Water Depths ◽

Oxygen Minimum

Abstract. Benthic Foraminifera from middle to late Pleistocene, (c. 600ka to 0ka), sediments of ODP Hole 686B, off Peru, show highest abundances and diversities during periods of cooler surface waters, (inferred from the Uk37 index), and enhanced upwelling, (inferred from the peridinacean/gonyaulacacean dinoflagellate cyst ratio). During the latest Pleistocene, (c. 160ka to 0ka), these periods are characterised by higher organic carbon contents in the bottom sediments, and occur during the odd-numbered, interglacial_18O stages. The benthic Foraminifera indicate deposition in 120 to 250 metres water depth for the earlier part of the record, (c. 600ka to c. 200ka), within the oxygen-minimum zone, with bottom water oxygen contents of <0.5 to 0.2 ml/l, (inferred from the dominance of Bolivinellina humilis). Deposition in water depths approaching those of the present day, (c. 450 metres), is indicated from c. 160ka onwards, with better oxygenated bottom water conditions, probably corresponding to the lower part of the oxygen-minimum zone.

Download Full-text