The nitrification in the ocean is influenced by several environmental  factors and the importance of these is more or less known. There are very  likely many more to be discovered in the study of the interaction of  nitrification bacteria and other micro-organisms in the ocean. Some of the  factors to be considered will briefly be dealt with in this paper. Then the authors give the results  of an incubation experiment in the Baltic Sea and from a detailed study in  Gullmarn

Enoksson, V.

English

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FRESHWATER BIOLOGICAL ASSOCIATION 
FBA Translation (New Series) No. 172 
Title: Nitrification in marine ecosystems 
Author (s) Enoksson, V. 
Reference: Rapp. Naturvardsverket SNVPM, No. 1213, 157-166. 
Original language: Swedish 
Date of publication of original: 1980 
Translator: I. Talling 
Date of publication of translation: 1986 
No. of pages of translation: 8 
FBA Translations are to be considered as 'provisional'. As a 
rule they have not been prepared by expert translators, nor have 
they been edited by the original authors. 
They are available from: The Librarian 
Freshwater Biological Association 
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at the current rate for xerox copying. 
FBA TRANSLATION (NEW SERIES) No. 172 
ENOKSSON V. 1980 
Nitrification in marine ecosystems. 
Rapp. Naturvardsverket SNVPM, No. 1213, 157-166 
Translated by: I. Talling 
Introduction 
The nitrification in the ocean is influenced by several environmental 
factors and the importance of these is more or less known. There are very 
likely many more to be discovered in the study of the interaction of 
nitrification bacteria and other micro-organisms in the ocean. Some of the 
factors to be considered will briefly be dealt with. Then we give the results 
of an incubation experiment in the Baltic Sea and from a detailed study in 
Gullmarn. 
The nitrate production in the ocean is synonymous with the bacterial 
oxidation of ammonia to nitrate. The process occurs in two stages: 
1) NH3 + 1 1/2 02 = > HN02 + H 20 
2) HN02 + 1/2 02 = > HN03 
Marine representatives of these two processes are (1) Nitrosococcus 
oceanus and (2) Nitrococcus mobilis. Both are chemoautotrophs i.e. they fix 
carbon dioxide. 
Environmental factors 
Oxygen: Nitrification bacteria are micro-aerophilic (Gundersen, 1966), 
i.e. they grow more quickly at low oxygen concentration. The 
oxygen starts to limit under 0.05 ml/1. 
pH: NH4 -oxydisers produce HN02 but not at such a rate that the 
pH of the ocean water is appreciably lowered. 
Redox- Nitrification is energy yielding if the Eh value is above 
potential c. 200 mV at a pH value of the oceanic water. 
NH+4 High NH+4 - content is rarely found in oceanic waters; at 
the most a few uM. The nitrate formation in a water mass 
cannot exceed the NH4 formation and it is therefore necessary 
to study the mineralisation. 
NO2- Nitrite is an intermediary product both in nitrification and 
denitrification. Phytoplankton can furthermore reduce NO -3 
to NO-2 in poor conditions of light. In the autumn of 1977 
we found in the Baltic Sea a primary NO -2 -maximum at the 
thermocline, which in this case was much deeper than the 
photic zone (fig. 1). It coincided with a NH4- -maximum and 
at the same depth the NO-3 started to increase towards the 
bottom. Similar depth distribution of inorganic nitrogen 
can often be found in various oceans. 
- 2 -
N0-3 gives little directional indication for the nitrification 
activity as it is used both for nitrogen assimilation and 
denitrification. 
Fig. 1 Distribution of nitrate, nitrite and ammonia during a period of 
11 days under BOSEX, the central station. September 6-19 1977. 
Fig. 3 Data for the uppermost 300m of a water column at station 17A outside 
Oahu. Data collected during the Bug Seafari cruise outside Hawaii 
(Gundersen et al, 1972). 
Fig. 2 Vertical profiles of nitrite, nitrate, phosphate, dissolved oxygen, 
temperature and salinity at station 15, Hakuho Maru KH-69-4 cruise 
(2°36'S, 154°53'W (Hattori and Wada 1971). 
- 3 -
The Problems 
Where does the primary N0-2 maximum originate? A secondary maximum 
can occur at greater depths in the oceans and is believed to be derived from 
denitrification. Brandhorst suggested (1959) that nitrification gave rise 
to the primary nitrite maximum. Hattori and Wada (1971) gave denitrification 
as the explanation in the tropical southern part of the Pacific Ocean (fig. 2) 
and Gunderson et al (1972) gave the same explanation for Hawaii (fig. 3). 
- 4 -
Kiefer et al (1976) (fig. 4) say that the NO -2 production from 
phytoplankton is sufficient to explain the primary NO-2 maximum in the central 
part of the Northern Pacific Ocean. 
Fig. 4 The vertical distribution of nitrate, nitrite and ammonia (A), density 
and oxygen (B) and chlorophyll, plant biomass-C and primary production 
(C). The measurements were all made between August 29 and September 
2 1973 near 27°57'N and 154°42'W. The biomass carbon was calculated 
from determinations of phytoplankton numbers (Kiefer et al, 1976). 
Attempts have been made to calculate the rate of nitrification in the 
ocean from the NO-3 production per cell density in the ocean. The cell density 
in the water body studied was far from sufficient to explain the high nitrate 
concentrations of up to 40 uM in the deep waters. One may speculate that 
this high nitrate was produced when the water was at another latitude than 
when measured. It is possible that a vital factor in the process has been 
ignored. Carlucci et al (1970) suggested that the rate can be larger in 
micro-environments, i.e. on plankton during the process of breaking down. 
Sediment 
Nitrification only takes place in the uppermost sediment layer, where 
oxygen is present. This has been confirmed by Billen (1976), who measured 
the autotrophic 14C incorporation in different types of sediment. In the 
sediment are often liberated large amounts of NH4 during mineralisation, 
which would favour a quick nitrification as long as the oxygen available 
is sufficient. The distance between the aerobic and anaerobic environment 
is short, especially if anaerobic micro-environments are included. N0-3 
can therefore easily diffuse to oxygen free zones where it is quickly denitrified. 
In the sediment bound nitrogen should thus effectively be released as N2. 
If the oxygen is depleted then the nitrogen accumulates as NH 4+. The 
denitrification is then moved out to the free water. Even water masses with 
low oxygen content have truly oxygen free micro-environments, though this is difficult 
to prove. Thus it is possible that nitrification and denitrification can 
exist side by side even in the free water. 
Methods 
The methods used to study the nitrification activity consisted of incubation 
with several combinations of added materials. 
Incubation in bottles in situ or in the laboratory 
Incubation with or without the addition of NH+/4, NO -2 
Incubation with or without inhibitors 
Incubation with tracers: 15M, 14c 
- 5 -
Fig. 5 Nitrification (activity experiments), the Baltic Sea. Station BY 38 
(Karlso depth) June 1978. 
A. Vertical distribution of temperature, salinity, density and 
oxygen. 
B. Vertical distribution of the various nitrogen parameters presented 
as components of the total nitrogen content. 
C. The nett increase resp. decrease of different nitrogen components 
after the addition of 9uM of NH+4, and following incubation of 
3 months. Each point is the mean of two (duplicate) samples. 
NB In B and C the quantities are given as lengths of horizontal 
columns, not as area. 
Results of incubation experiments with water from the Baltic Sea 
Karlso djupet (Karls Island depth) June 1978 (fig. 5) 
The samples were incubated for 3 months with the addition of 9uM NH+4 
Fig. 5a: Hydrography. A thermocline between 10m and 30m depth. A halocline, 
which coincides with a thermocline at 70-80m. At the same depth, the 
oxygen content declines drastically. 
Fig. 5b: Original concentrations of the nitrogen components. (PON = particulate 
nitrogen. DON = dissolved organic nitrogen). The NO -2-and NH+4 -maxima 
found the previous autumn were not found again. Nitrate was the 
only inorganic nitrogen component found in rather high concentrations 
and then only below the halocline. 
Fig. 5c: Changes in the water during the incubation. The left hand side shows 
the utilisation and the. right hand one the formation of nitrogen 
components. 
- 6 -
The water column can be divided into three zones: 
20 - 30m: Mineralisation but no nitrification. 
40 - 50m: In one sample from each of the depths, all the NH had been 
oxidised to NO but not further on to N03. There thus existed 
a potential for the NH+4-oxidation but not for the N0-2-oxidation. 
Even here a nett-mineralisation had occurred. 
60 - 102m (bottom): Just about all the NH+4 had been used up in all the 16 
samples. Inorganic nitrogen reappeared as NO -3, including that 
formed by mineralisation. 
The nitrification potential was thus largest at the depths where we 
found high NO -3 concentrations the previous autumn, i.e. under 60m. It may 
be coincidence that the samples which gave the NO -2 production had been 
taken from depths where the NO -2 maximum had been the previous autumn. Above 
30m the nitrification potential is insignificant in spite of a good access 
to NH +4. 
This experiment very much indicates that the NO -2 maximum in the 
Baltic Sea originates from NH +4 oxidation which has not been follcwed by NO 2 
oxidation. 
Results from intensive studies in Gullmarn 
At the end of October and beginning of November 1978, an intensive 
study was made in Gullmarn; two measurements per day for 5 days (fig. 6). 
Oxygen and nitrogen components were analysed along with measurements of flow, 
temperature and salinity which were done by Gary Shaffer (The Oceanographic 
Institute, Goteborg). We had hoped to find an answer to the question, 'How 
representative are individual measurements in Gullmarn?' 
The sequence of events can most easily be explained for the first three 
days. On the fourth day the situation was complicated by strong winds. 
<10m: An inwards directed current was dominating. This period was preceded 
by a very dense autumn bloom and therefore nearly all the nitrogen 
organically bound. 
10-20m An outwards directed current carried old water from Gullmarn, with 
a relatively low oxygen content, but a high NO 3 content. 
20-50m This layer had entered over the threshold. The high NH +4 content had 
a connection with the preceding bloom. One can speculate that the 
water had been closer to the surface in Skagerak and it can therefore 
be considered to be not old or as surface water. 
50m-bottom The threshold at 40m depth prevents the bottom water from being 
exchanged at the same rate as the layers above. The water is typically 
old, with relatively low concentrations of oxygen, NH +4, NO -2 and 
organic nitrogen but large amounts of NO -3. 
The distribution of NH +4, N0-2 and NO -3 in GulImam during this period 
gives certain information about the nitrification activity. The large quantities 
of NH +4 between 20m and 50m indicate that the nitrification was slow in this 
water body. Both on top and below it was deliminated by old water which gave 
rise to two mixed zones. In both of these zones we found high concentrations 
of nitrite; this agrees well with the results from the incubation experiments 
with the Baltic Sea water. We still do not know why the NO -2 oxidation is 
inhibited more than the NH +4 oxidation in the mixed zones between the surface 
water and old water or why nitrification is nearly completly inhibited in the 
surface water. 
- 7 -
- 8 -
This unusual situation where we have a NO -3 maximum near the surface and 
two NO -2 maxima can be explained through our knowledge of the behaviour of 
the currents. We are continuing our intensive studies in Gullmarn in 
co-operation with other groups of the West Coast Project on the long term 
aspect of the nitrogen budget. 
Referenser 
Billen, G. 1976. Evaluation of nitrifying acticity in sediments by dark 
14C-bicarbonate incorporation. - Water Research 10:51-57. 
Brandhorst, W. 1959. Nitrification and denitrification in the eastern 
tropical north Pacific. - J. Cons. int. Explor. Mer 25:3-20. 
Carlucci, A.F., Hartwig, E.O. & Bowes, P.M. 1970. Biological production. 
of nitrite in seawater. - Mar. Biol. 7:161-166. 
Gundersen, K. 1966. The growth and respiration of Nitrosocystis oceanus at 
different partial pressures of oxygen. - J. gen. Microbiol. 42:387-396. 
Gundersen, K., Mountain, C.W., Taylor, D., Ohye, R. & Shen, J. 1972. 
Some chemical and microbiological observations in the Pacific Ocean 
off the Hawaiian islands. - Litnnol. Oceanogr. 17:524-531. 
Hattori, A. & Wada, E. 1971. Nitrite distribution and its regulating 
processes in the equatorial Pacific Ocean. - Deep-Sea Research. 
18:557-568. 
Kiefer. D.A., Olson, R.J. & Holm-Hansen, 0. 1976. Another look at the 
nitrite and chlorophyll maxima in the central North Pacific. 
- Deep-Sea Research. 23:1199-1208. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Notice 
 
 
Please note that these translations were produced to assist the scientific staff of the 
FBA (Freshwater Biological Association) in their research. These translations were 
done by scientific staff with relevant language skills and not by professional 
translators. 
 
 
 


Nitrification in marine ecosystems [Translation from: Rapp.Naturvardsverket SNVPM No.1213, 157-166, 1980]

http://aquaticcommons.org/4964/1/172_1980_enok_nitr.pdf

Nitrification in marine ecosystems [Translation from: Rapp.Naturvardsverket SNVPM No.1213, 157-166, 1980]

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