scholarly journals Life at stable low oxygen levels: adaptations of animals to oceanic oxygen minimum layers.

1998 ◽  
Vol 201 (8) ◽  
pp. 1223-1232 ◽  
Author(s):  
J J Childress ◽  
B A Seibel
Keyword(s):  
Water Column ◽  
Aerobic Metabolism ◽  
Oxygen Level ◽  
Low Oxygen ◽  
Oxygen Levels ◽  
Surface Areas ◽  
Partial Pressures ◽  
Stable Conditions ◽  
Consumption Rates ◽  
Oxygen Minimum

Zones of minimum oxygen level are found at intermediate depths in most of the world's oceans and, although the oxygen partial pressure in some of these 'oxygen minimum layers' is only a fraction of a kilopascal, populations of pelagic metazoans exist there. These oxygen minimum layers are areas of the water column and the associated benthos with stable conditions of continuously low oxygen level and low temperature at intermediate depths (400-1000 m depth) over vast areas. Off California, where PO2 at the oxygen minimum is 0.8 kPa, there are abundant populations of animals both in the water column and on the bottom. Farther to the south in the eastern tropical Pacific, oxygen partial pressures of less than approximately 0.4 kPa result in very low biomasses and diversity of animals at minimum layer depths. At the minimum oxygen levels found off California, most animals which inhabit the minimum zones appear to support their routine metabolic demands via aerobic metabolism. They do this by being very effective at removing oxygen from water. Among the adaptations of pelagic crustaceans to these conditions are: (1) enhanced ventilatory abilities, (2) enhanced percentage removal of O2 from the ventilatory stream, (3) large gill surface areas, (4) short diffusion distances from the water to the blood, and (5) hemocyanin respiratory proteins with a very high affinity for O2, high cooperativity and large Bohr effects. The lower O2 consumption rates of many deeper-living species are also functionally adaptive in that they facilitate aerobic survival at low PO2. However, they are not adaptations to the minimum layer, since similarly low rates are found in the same and comparable species living at the same depths in regions without well-developed minima, and these animals are unable to survive at the low PO2 values of the minima. While anaerobic metabolism may be important for metabolic rates above the routine level for most animals in the minimum layer, there is little evidence for the use of sustained anaerobiosis in the species studied. In summary, given the stable presence of very low O2 levels in the minima, the primary adaptations of animals living within them are those that support aerobic metabolism by giving the animals remarkable abilities to extract O2 from water. These abilities are notably better than those of animals adapted to unstable hypoxic environments, such as intertidal mudflats, while the latter animals rely to a much greater extent on anaerobiosis and perhaps on metabolic suppression to survive periods of anoxia.

scholarly journals Viral community analysis in a marine oxygen minimum zone indicates increased potential for viral manipulation of microbial physiological state

2021 ◽  
Author(s):  
Sophie K. Jurgensen ◽  
Simon Roux ◽  
Sarah M. Schwenck ◽  
Frank J. Stewart ◽  
Matthew B. Sullivan ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Water Column ◽  
Physiological State ◽  
Community Analysis ◽  
Viral Metagenomics ◽  
Infection Frequency ◽  
Critical Systems ◽  
Low Oxygen ◽  
Viral Community ◽  
Oxygen Minimum

AbstractMicrobial communities in oxygen minimum zones (OMZs) are known to have significant impacts on global biogeochemical cycles, but viral influence on microbial processes in these regions are much less studied. Here we provide baseline ecological patterns using microscopy and viral metagenomics from the Eastern Tropical North Pacific (ETNP) OMZ region that enhance our understanding of viruses in these climate-critical systems. While extracellular viral abundance decreased below the oxycline, viral diversity and lytic infection frequency remained high within the OMZ, demonstrating that viral influences on microbial communities were still substantial without the detectable presence of oxygen. Viral community composition was strongly related to oxygen concentration, with viral populations in low-oxygen portions of the water column being distinct from their surface layer counterparts. However, this divergence was not accompanied by the expected differences in viral-encoded auxiliary metabolic genes (AMGs) relating to nitrogen and sulfur metabolisms that are known to be performed by microbial communities in these low-oxygen and anoxic regions. Instead, several abundant AMGs were identified in the oxycline and OMZ that may modulate host responses to low-oxygen stress. We hypothesize that this is due to selection for viral-encoded genes that influence host survivability rather than modulating host metabolic reactions within the ETNP OMZ. Together, this study shows that viruses are not only diverse throughout the water column in the ETNP, including the OMZ, but their infection of microorganisms has the potential to alter host physiological state within these biogeochemically important regions of the ocean.

scholarly journals Respiratory adaptations in a deep-sea orbiniid polychaete from Gulf of Mexico brine pool NR-1: metabolic rates and hemoglobin structure/function relationships

2002 ◽  
Vol 205 (11) ◽  
pp. 1669-1681 ◽  
Author(s):  
Stéphane Hourdez ◽  
Roy E. Weber ◽  
Brian N. Green ◽  
John M. Kenney ◽  
Charles R. Fisher
Keyword(s):  
Gulf Of Mexico ◽  
Sea Water ◽  
Oxygen Affinity ◽  
Aerobic Metabolism ◽  
Low Oxygen ◽  
Small Diffusion ◽  
Large Numbers ◽  
Partial Pressures ◽  
Hemoglobin Oxygen Affinity ◽  
Rate Of Oxygen Consumption

SUMMARY Methanoaricia dendrobranchiata Blake (Polychaeta; Orbiniidae)occurs in large numbers in association with communities of the mussel Bathymodiolus childressi at hydrocarbon seeps on the Louisiana Slope of the Gulf of Mexico. Its microhabitat can be strongly hypoxic (oxygen is often undetectable) and sulfidic (sulfide concentrations can reach millimolar levels), which may seriously challenge aerobic metabolism. We describe a suite of adaptations to its low-oxygen environment. The worms are capable of regulating their rate of oxygen consumption down to partial pressures of approximately 870 Pa oxygen. This capability correlates with a large gill surface area, a small diffusion distance from sea water to blood, a very high hemoglobin oxygen-affinity (P50=27.8 Pa at 10°C and pH 7.6) and a Bohr effect that is pronounced at high oxygen saturations. When fully saturated, the hemoglobin binds sufficient oxygen for only 31 min of aerobic metabolism. However, these polychaetes can withstand extended periods of anoxia both in the absence and presence of 1 mmoll-1 sulfide(TL50=approx. 5.5 and 4 days, respectively).

scholarly journals Reduced oxygen concentration during human IVF culture improves embryo utilization and cumulative pregnancy rates per cycle

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Aafke P A Van Montfoort ◽  
Eus G J M Arts ◽  
Lydia Wijnandts ◽  
Alexander Sluijmer ◽  
Marie-José Pelinck ◽  
...  
Keyword(s):  
Live Birth ◽  
Embryo Culture ◽  
Oxygen Level ◽  
Low Oxygen ◽  
Birth Rates ◽  
Oxygen Levels ◽  
Live Birth Rates ◽  
Oxygen Groups ◽  
Oxygen Group ◽  
Human Ivf

Abstract STUDY QUESTION Do different oxygen levels during human IVF embryo culture affect embryo utilization, cumulative IVF success rates per cycle and neonatal birthweight? SUMMARY ANSWER After 2 days of culture, a lower oxygen level (5%) leads to more good-quality embryos and more embryos that can be cryopreserved, and thereby to a higher cumulative live birth rate per cycle when compared to embryo culture in 20% oxygen, while birthweights are similar. WHAT IS KNOWN ALREADY Several studies have compared IVF outcome parameters after embryo culture in a more physiological level of 5% oxygen and the atmospheric level of 20%. Although there is consensus that embryo development improves in 5% oxygen, effects on pregnancy and live birth rates are mainly seen in blastocyst, but not cleavage-stage transfers. A major drawback of these studies is that only fresh embryo transfers were included, not taking additional frozen-thawed transfers from these cycles into account. This might have underestimated the effects of oxygen level, especially in cleavage-stage embryo transfers. Furthermore, little is known about the effect of oxygen level during culture on birthweight. STUDY DESIGN, SIZE, DURATION This is a cohort study in 871 consecutive patients who had an IVF cycle between January 2012 and December 2013, and 5–7 years follow-up to allow transfer of frozen-thawed embryos. Based on daily availability of positions in the incubators, all oocytes and embryos of one cycle were allocated to one of the three incubators with traditional ambient oxygen levels (6% CO2 and 20% O2 in air), or to a fourth incubator that was adjusted to have low oxygen levels of 5% (6% CO2, 5% O2 and 89% N2). Embryos were cultured under 5 or 20% oxygen until Day 2 or 3, when embryos were transferred or cryopreserved, respectively. Clinical and other laboratory procedures were similar in both groups. PARTICIPANTS/MATERIALS, SETTING, METHODS To compare embryo characteristics and (cumulative) pregnancy outcomes between the two oxygen groups, for each patient only the first cycle in the study period was included in the analysis, resulting in 195 cycles in the 5% group (1627 oocytes) and 676 in the 20% oxygen group (5448 oocytes). Embryo characteristics were analysed per cycle and per embryo and were corrected for maternal age, cycle rank order, fertilization method (IVF or ICSI) and cause of subfertility. Perinatal data from the resulting singletons (n = 124 after fresh and 45 after frozen-thawed embryo transfer) were collected from delivery reports from the hospitals or midwife practices. MAIN RESULTS AND THE ROLE OF CHANCE In the 5% oxygen group, there were significantly more embryos of good quality (45.8 versus 30.9% in the 20% group, adjusted odds ratio (OR) [95% CI] = 1.9 [1.6–2.4]). This did not result in higher live birth rates per cycle, but after fresh transfers more good-quality spare embryos could be cryopreserved (46.1 versus 29.7%, adjusted OR [95% CI] = 2.0 [1.7–2.5]). After a follow-up period of 5–7 years, in which 82.4% of the cryopreserved embryos from the 5% oxygen group and 85.4% from the 20% oxygen group were thawed, the percentage of patients with at least one live birth resulting from the study cycle was significantly higher in the low oxygen group (adjusted OR [95% CI] = 1.5 [1.01–2.2]). In 124 live born singletons from fresh embryo transfers and in 45 from transfers of cryopreserved embryos, birthweight was similar in both oxygen groups after correction for confounding factors. LIMITATIONS, REASONS FOR CAUTION This is a retrospective study, and treatment allocation was not randomised. The study was not powered for a predefined birthweight difference. With the number of live births in our study, small differences in birthweight might not have been detected. The selection of embryos to be cryopreserved was based on embryo morphology criteria that might be different in other clinics. WIDER IMPLICATIONS OF THE FINDINGS Improved embryo utilization by more cryopreservation leading to higher cumulative live birth rates per cycle favours the use of 5% instead of 20% oxygen during human IVF embryo culture. This study also demonstrates that for comparison of different IVF treatment regimens, the cumulative outcome, including transfers of fresh and frozen-thawed embryos, is to be preferred instead of analysis of fresh embryo transfers only. STUDY FUNDING/COMPETING INTEREST(S) No external funding was received for this study. None of the authors has a conflict of interest to declare. TRIAL REGISTRATION NUMBER NA

scholarly journals Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions

2016 ◽  
Vol 13 (8) ◽  
pp. 2241-2255 ◽  
Author(s):  
Rainer Kiko ◽  
Helena Hauss ◽  
Friedrich Buchholz ◽  
Frank Melzner
Keyword(s):  
Carbon Dioxide ◽  
Partial Pressure ◽  
Respiratory Activity ◽  
Ammonium Excretion ◽  
Calanoid Copepods ◽  
Low Oxygen ◽  
Oxygen Levels ◽  
Minimum Zone ◽  
Excretion Rates ◽  
Oxygen Minimum

Abstract. Calanoid copepods and euphausiids are key components of marine zooplankton communities worldwide. Most euphausiids and several copepod species perform diel vertical migrations (DVMs) that contribute to the export of particulate and dissolved matter to midwater depths. In vast areas of the global ocean, and in particular in the eastern tropical Atlantic and Pacific, the daytime distribution depth of many migrating organisms corresponds to the core of the oxygen minimum zone (OMZ). At depth, the animals experience reduced temperature and oxygen partial pressure (pO2) and an increased carbon dioxide partial pressure (pCO2) compared to their near-surface nighttime habitat. Although it is well known that low oxygen levels can inhibit respiratory activity, the respiration response of tropical copepods and euphausiids to relevant pCO2, pO2, and temperature conditions remains poorly parameterized. Further, the regulation of ammonium excretion at OMZ conditions is generally not well understood. It was recently estimated that DVM-mediated ammonium supply could fuel bacterial anaerobic ammonium oxidation – a major loss process for fixed nitrogen in the ocean considerably. These estimates were based on the implicit assumption that hypoxia or anoxia in combination with hypercapnia (elevated pCO2) does not result in a down-regulation of ammonium excretion. We exposed calanoid copepods from the Eastern Tropical North Atlantic (ETNA; Undinula vulgaris and Pleuromamma abdominalis) and euphausiids from the Eastern Tropical South Pacific (ETSP; Euphausia mucronata) and the ETNA (Euphausia gibboides) to different temperatures, carbon dioxide and oxygen levels to study their survival, respiration and excretion rates at these conditions. An increase in temperature by 10 °C led to an approximately 2-fold increase of the respiration and excretion rates of U. vulgaris (Q10, respiration = 1.4; Q10, NH4-excretion = 1.6), P. abdominalis (Q10, respiration = 2.0; Q10, NH4-excretion = 2.4) and E. gibboides (Q10, respiration = 2.0; Q10, NH4-excretion = 2.4; E. mucronata not tested). Exposure to differing carbon dioxide levels had no overall significant impact on the respiration or excretion rates. Species from the ETNA were less tolerant to low oxygen levels than E. mucronata from the ETSP, which survived exposure to anoxia at 13 °C. Respiration and excretion rates were reduced upon exposure to low oxygen levels, albeit at different species-specific levels. Reduction of the excretion and respiration rates in ETNA species occurred at a pO2 of 0.6 (P. abdominalis) and 2.4 kPa (U. vulgaris and E. gibboides) at OMZ temperatures. Such low oxygen levels are normally not encountered by these species in the ETNA. E. mucronata however regularly migrates into the strongly hypoxic to anoxic core of the ETSP OMZ. Exposure to low oxygen levels led to a strong reduction of respiration and ammonium excretion in E. mucronata (pcrit  respiration = 0.6, pcrit NH4-excretion = 0.73). A drastic reduction of respiratory activity was also observed by other authors for euphausiids, squat lobsters and calanoid copepods, but was not yet accounted for when calculating DVM-mediated active fluxes into the ETSP OMZ. Current estimates of DVM-mediated active export of carbon and nitrogen into the ETSP OMZ are therefore likely too high and future efforts to calculate these export rates should take the physiological responses of migratory species to OMZ conditions into account.

Some Effects of Temporary Exposure to Low Dissolved Oxygen Levels on Pacific Salmon Eggs

1958 ◽  
Vol 15 (2) ◽  
pp. 229-250 ◽  
Author(s):  
D. F. Alderdice ◽  
W. P. Wickett ◽  
J. R. Brett
Keyword(s):  
Oxygen Consumption ◽  
Dissolved Oxygen ◽  
Oxygen Demand ◽  
Oxygen Availability ◽  
Oncorhynchus Keta ◽  
Hatching Rate ◽  
Oxygen Level ◽  
Low Oxygen ◽  
Low Dissolved Oxygen ◽  
Oxygen Levels

Eggs of the chum salmon (Oncorhynchus keta) were exposed to various constant levels of dissolved oxygen for a period of seven days. The procedure was repeated with fresh egg samples at various developmental stages. Temperatures were constant at 10 °C. from fertilization to hatching. Estimates of oxygen consumption uninhibited by low dissolved oxygen levels were obtained at various stages of egg development for whole eggs and also on the basis of the weight of larvae, excluding the yolk. Eggs were most sensitive to hypoxia between 100–200 Centigrade degree-days and compensated for reduced oxygen availability by reducing the oxygen demand and rate of development. Very low oxygen levels at early incubation stages resulted in the production of monstrosities. At about the time the circulatory system becomes functional the compensatory reduction in rate of growth under hypoxial conditions is reduced, but eggs no longer survive extreme hypoxial conditions. Eggs subjected to low dissolved oxygen levels just prior to hatching hatch prematurely at a rate dependent on the degree of hypoxia. The maximum premature hatching rate corresponded approximately with the median lethal oxygen level. Estimated median lethal levels rose slowly from fertilization to hatching. Oxygen consumption per egg rose from fertilization to hatching while the consumption per gram of larval tissue declined from a high to a low level at about the time of blastopore closure. Subsequently, a slight rise in the rate occurred up to a level which was more or less constant to hatching. "Critical" dissolved oxygen levels were calculated and they appear to define the oxygen level above which respiratory rate is unmodified by oxygen availability. Critical levels ranged from about 1 p.p.m. in early stages to over 7 p.p.m. shortly before hatching.

scholarly journals On The Relative Importance of Aerobic Metabolism in Small Nematode Parasites of the Alimentary Tract II. the Utilization of Oxygen at Low Partial Pressures by Small Nematode Parasites of the Alimentary Tract

1949 ◽  
Vol 2 (2) ◽  
pp. 166 ◽  
Author(s):  
WP Rogers
Keyword(s):  
Small Intestine ◽  
Haemonchus Contortus ◽  
Alimentary Tract ◽  
Intestinal Parasites ◽  
Low Oxygen ◽  
Nematode Parasites ◽  
Partial Pressures ◽  
Consumption Rates

Nippostrongylus muris, Haemonchus contortus, Nematodirus spathiger, and N. filicollis are all capable of utilizing oxygen for respiratory purposes even when it is present at very low oxygen tensions. Thus with a partial pressure as low as 5 mm. of mercury the respiration of Nippostrongylus muris may reach 40 per cent. of its maximum rate, whereas Nematodirus spp. and H. contortus may respire at 25 and 12 per cent. of their maximum rates respectively. Further, the results indicate that in vivo the oxygen consumption rates may sometimes reach 80 per cent. of the maximum in vitro rate in the case of Nippostrongylus muris in the small intestine of the rat and 40 per cent. in the case of Nematodirus spp. in the small intestine of the sheep. Haemonchus contortus in the sheep abomasums probably respires at a relatively lower rate than either of the intestinal parasites in vivo.

scholarly journals Differential Distribution and Determinants of Ammonia Oxidizing Archaea Sublineages in the Oxygen Minimum Zone off Costa Rica

2019 ◽  
Vol 7 (10) ◽  
pp. 453 ◽  
Author(s):  
Yanhong Lu ◽  
Xiaomin Xia ◽  
Shunyan Cheung ◽  
Hongmei Jing ◽  
Hongbin Liu
Keyword(s):  
Costa Rica ◽  
Water Column ◽  
Gulf Of California ◽  
North Pacific Ocean ◽  
Oxygen Minimum Zone ◽  
Low Oxygen ◽  
Environmental Determinants ◽  
Ammonia Oxidizing Archaea ◽  
Minimum Zone ◽  
Oxygen Minimum

Ammonia oxidizing archaea (AOA) are microbes that are widely distributed in the ocean that convert ammonia to nitrite for energy acquisition in the presence of oxygen. Recent study has unraveled highly diverse sublineages within the previously defined AOA ecotypes (i.e., water column A (WCA) and water column B (WCB)), although the eco-physiology and environmental determinants of WCB subclades remain largely unclear. In this study, we examined the AOA communities along the water columns (40–3000 m depth) in the Costa Rica Dome (CRD) upwelling region in the eastern tropical North Pacific Ocean. Highly diverse AOA communities that were significantly different from those in oxygenated water layers were observed in the core layer of the oxygen minimum zone (OMZ), where the dissolved oxygen (DO) concentration was < 2μM. Moreover, a number of AOA phylotypes were found to be enriched in the OMZ core. Most of them were negatively correlated with DO and were also detected in other OMZs in the Arabian Sea and Gulf of California, which suggests low oxygen adaptation. This study provided the first insight into the differential niche partitioning and environmental determinants of various subclades within the ecotype WCB. Our results indicated that the ecotype WCB did indeed consist of various sublineages with different eco-physiologies, which should be further explored.

scholarly journals Benthic phosphorus cycling in the Peruvian oxygen minimum zone

2016 ◽  
Vol 13 (5) ◽  
pp. 1367-1386 ◽  
Author(s):  
Ulrike Lomnitz ◽  
Stefan Sommer ◽  
Andrew W. Dale ◽  
Carolin R. Löscher ◽  
Anna Noffke ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Sediments ◽  
Solid Phase ◽  
Continental Margins ◽  
Low Oxygen ◽  
Anoxic Waters ◽  
Oxygen Conditions ◽  
Bottom Waters ◽  
Minimum Zone ◽  
Oxygen Minimum

Abstract. Oxygen minimum zones (OMZs) that impinge on continental margins favor the release of phosphorus (P) from the sediments to the water column, enhancing primary productivity and the maintenance or expansion of low-oxygen waters. A comprehensive field program in the Peruvian OMZ was undertaken to identify the sources of benthic P at six stations, including the analysis of particles from the water column, surface sediments, and pore fluids, as well as in situ benthic flux measurements. A major fraction of solid-phase P was bound as particulate inorganic P (PIP) both in the water column and in sediments. Sedimentary PIP increased with depth in the sediment at the expense of particulate organic P (POP). The ratio of particulate organic carbon (POC) to POP exceeded the Redfield ratio both in the water column (202 ± 29) and in surface sediments (303 ± 77). However, the POC to total particulate P (TPP = POP + PIP) ratio was close to Redfield in the water column (103 ± 9) and in sediment samples (102 ± 15). This suggests that the relative burial efficiencies of POC and TPP are similar under low-oxygen conditions and that the sediments underlying the anoxic waters on the Peru margin are not depleted in P compared to Redfield. Benthic fluxes of dissolved P were extremely high (up to 1.04 ± 0.31 mmol m−2 d−1), however, showing that a lack of oxygen promotes the intensified release of dissolved P from sediments, whilst preserving the POC / TPP burial ratio. Benthic dissolved P fluxes were always higher than the TPP rain rate to the seabed, which is proposed to be caused by transient P release by bacterial mats that had stored P during previous periods when bottom waters were less reducing. At one station located at the lower rim of the OMZ, dissolved P was taken up by the sediments, indicating ongoing phosphorite formation. This is further supported by decreasing porewater phosphate concentrations with sediment depth, whereas solid-phase P concentrations were comparatively high.

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