Nitrate impact on fishes ?

[SomethingsFishy24]

This study is on Zebra fish, who, for lack of better terms seem to be damn near bomb proof fish. This is applicable to a high volume fish farm setting, not a home aquarium, basically trying to find out how high nitrates can be before the fish are affected and die.

“Histopathological Changes and Zootechnical Performance in Juvenile Zebrafish (Danio rerio) Under Chronic Exposure to Nitrate”, António et. al.

2017:

This study evaluated the impact of chronic exposure to relevant levels of nitrate on the zootechnical performance and histology of selected organs (gills, integument, kidney, liver, and intestine) of juvenile zebrafish, with the aim to define safety levels of this nitrogenous compound for zebrafish rearing. For that, groups of 30-day-old zebrafish were exposed to < 7 (control), 100, 200, and 400 mg L− 1 nitrate-N for 28 days.

No mortality was registered in fish exposed up to 200 mg L− 1 nitrate, and all individuals seemed externally healthy; however, in fish exposed to the highest nitrate concentration mortality reached 47% at the end of the trial, and many individuals showed lethargy, abnormal swimming, emaciation, lordosis, and/or superficial lesions. Although final growth was not significantly different among groups, growth parameters tend to decrease with increasing levels of nitrate, and a significant negative correlation was found between weight gain and nitrate levels, suggesting a dose-dependent negative effect of nitrate on growth.

Except for the lowest nitrate concentration (100 mg L− 1 nitrate-N), the histological survey revealed significant changes induced by nitrate in all examined organs, and a dose-dependent effect of nitrate on the overall histopathological changes is suggested. In conclusion, this study shows that the chronic exposure of zebrafish juveniles to nitrate induces histopathological changes that would lead to a negative impact on the general health condition of fish. Fish growth tended to decrease and the overall histological damages tended to increase with increasing nitrate levels, particularly above 100 mg L− 1 (the lowest tested value). Thus, we recommend that this limit of 100 mg L− 1 nitrate-N should not be exceeded in RAS during rearing of juvenile zebrafish.

 

[Uberhoust]

So I cannot find a direct peer reviewed paper but this one https://journals.biologists.com/jeb...rmal-acclimation-offsets-the-negative-effects deals with the Aerobic Scope (AS in the paper) of Silver Perch. The experiment was to determine how fish handled warmer water than normal but also looked at the Nitrate concentration at the same time. The experimenters found a negative affect on the fish at 50ppm Nitrate at fish raised in 28 C water. The Nitrate reduces the fish's ability to transport oxygen in their blood.

Below is a direct quote from the Discussion section:

Nitrate exposure causes a narrowing of AS​

Exposure to elevated nitrate concentrations (both 50 and 100 mg l−1) lowered the AS of fish acclimated to 28°C. Reductions in AS were driven by both increases in ṀO2,standard and decreases in ṀO2,max of nitrate-exposed fish. This is in agreement with other studies that have found elevated resting metabolic costs in response to nitrate pollution due to detoxification and cellular maintenance costs (de Campos et al., 2014), as well as decreases in ṀO2,max caused by the oxidation of haemoglobin to methaemoglobin (Gomez Isaza et al., 2020b).

Although the test is not specifically for Nitrate damage it does suggest that Nitrate is tolerated but leads to lower aerobic capabilities with the fish. This would suggest that the lower the Nitrate values the better the fish function. This paper only looks at relative short term exposure and only on aerobic fitness but suggests fish would do better without any Nitrate. The problem then becomes how much affect from Nitrate is a fish keeper willing to accept, this is a social issue and depends on what compromises one is willing to take to own and keep fish.

 

[Byron]

I know a lot of people state that nitrate is harmful but i would like to see a paper that provides detail on nitrate level/impact on fish health and how it impact the health. If enough people say the same thing it becomes 'well recognize' but if none of those people have every studied the raw data it becomes baseless hersey.

Scientific evidence is (preferably) the results of scientifically-controlled studies. But some equally-valid evidence can result from analysis. Subsequent research and studies may refute or confirm the latter. Much depends upon who is doing the "analysis."

A few years ago I discussed this issue of nitrate with Neale Monks. Most of us here know that Dr. Monks is one of the most highly-respected and knowledgeable scientists associated with this hobby. The following is from our exchange [with Neale's permission].

Byron: I would assume that the effect of nitrate is much like so many things--a source of stress, weakening the fish, opening up opportunities for more serious problems.​

​

Neale: Correct, so far as I can tell. Nitrate isn't immediately toxic like ammonia or nitrite. On the other hand, because high nitrate levels often go hand-in-hand with things like overstocking and infrequent water changes, it's hard to pick out any problems nitrate is causing from things like lack of oxygen and background acidification caused by nitrate and phosphate accumulation. Tanks with high nitrate levels tend to be neglected tanks, in the sense that the fish keeper has too many fish in them and does too few water changes. So there can be all sorts of reasons fish in those tanks are stressed, not just the nitrate. Make sense?​

​

Byron: One obvious that I assume would occur would be a shortened lifespan from the stress if nothing else. But are there any signs along the way that nitrate may be causing issues?​

​

Neale: None that I'm aware of, but some diseases have been associated with high nitrate level, such as Hexamita and HITH/HLLE in cichlids.​

​

Byron: I have come across studies, admittedly on mainly commercial fish and not ornamental, suggesting nitrate levels of 2 to 4 ppm NO3 N-N would affect the development of fry, and many fish and invertebrates will have difficulty with nitrate at 10 ppm NO3 N-N. This study is here:​

https/www.researchgate.net/publication/8063535_Nitrate_Toxicity_to_Aquatic_Animals_A_Review_With_New_Data_for_Freshwater_Invertebrates​

You have mentioned cichlids likely being affected at levels above 20 ppm, and on the cichlid site it is suggested that nitrate above this may be the true cause of Malawi Bloat.​

​

Neale: Correct. That said, nitrate is complicated.​

​

Byron: With the proviso that parameters (GH, KH, pH , temperature) are close enough to be called the same, a large water change to reduce nitrate from 160 ppm down to 10 or 20 ppm is not going to harm the fish, and is more advisable than doing smaller changes over weeks. I will assume my understanding is correct unless you say different.​

​

Neale: This is a good summation. I would 100% agree with this. Triage of any kind is about balancing the big dangers against the minor stresses.​

Cheers, Neale​

 

[anewbie]

Did he comment if ph effected the affect of nitrate on fishes (like it does ammonia ) ? One of the conflict is plant people (hi-tech tanks) want 40ppm nitrate which of course is not very good for many fishes that require more pure water - or from other fishes in general - which of course raises the conflict that sounds like either you are raising a plant tank or a fish tank ?

Scientific evidence is (preferably) the results of scientifically-controlled studies. But some equally-valid evidence can result from analysis. Subsequent research and studies may refute or confirm the latter. Much depends upon who is doing the "analysis."

A few years ago I discussed this issue of nitrate with Neale Monks. Most of us here know that Dr. Monks is one of the most highly-respected and knowledgeable scientists associated with this hobby. The following is from our exchange [with Neale's permission].

Byron: I would assume that the effect of nitrate is much like so many things--a source of stress, weakening the fish, opening up opportunities for more serious problems.​

​

Neale: Correct, so far as I can tell. Nitrate isn't immediately toxic like ammonia or nitrite. On the other hand, because high nitrate levels often go hand-in-hand with things like overstocking and infrequent water changes, it's hard to pick out any problems nitrate is causing from things like lack of oxygen and background acidification caused by nitrate and phosphate accumulation. Tanks with high nitrate levels tend to be neglected tanks, in the sense that the fish keeper has too many fish in them and does too few water changes. So there can be all sorts of reasons fish in those tanks are stressed, not just the nitrate. Make sense?​

​

Byron: One obvious that I assume would occur would be a shortened lifespan from the stress if nothing else. But are there any signs along the way that nitrate may be causing issues?​

​

Neale: None that I'm aware of, but some diseases have been associated with high nitrate level, such as Hexamita and HITH/HLLE in cichlids.​

​

Byron: I have come across studies, admittedly on mainly commercial fish and not ornamental, suggesting nitrate levels of 2 to 4 ppm NO3 N-N would affect the development of fry, and many fish and invertebrates will have difficulty with nitrate at 10 ppm NO3 N-N. This study is here:​

https/www.researchgate.net/publication/8063535_Nitrate_Toxicity_to_Aquatic_Animals_A_Review_With_New_Data_for_Freshwater_Invertebrates​

You have mentioned cichlids likely being affected at levels above 20 ppm, and on the cichlid site it is suggested that nitrate above this may be the true cause of Malawi Bloat.​

​

Neale: Correct. That said, nitrate is complicated.​

​

Byron: With the proviso that parameters (GH, KH, pH , temperature) are close enough to be called the same, a large water change to reduce nitrate from 160 ppm down to 10 or 20 ppm is not going to harm the fish, and is more advisable than doing smaller changes over weeks. I will assume my understanding is correct unless you say different.​

​

Neale: This is a good summation. I would 100% agree with this. Triage of any kind is about balancing the big dangers against the minor stresses.​

Cheers, Neale​

 

[anewbie]

@Byron one other comment i wanted to make is that the paper you referenced has NO3-N which other say has a 4.43 ratio to NO3. I.e, if the paper suggest 10ppm is bad that is equiv to 40ppm of NO3; which is not exactly as low as I would expect.

 

[TwoTankAmin]

Here is what I have bookmarked;

Julio A. Camargo, Alvaro Alonso, Annabella Salamanca,
Nitrate toxicity to aquatic animals: a review with new data for freshwater invertebrates,
Chemosphere, Volume 58, Issue 9, 2005, Pages 1255-1267,
ISSN 0045-6535,


Abstract:
Published data on nitrate (NO3-) toxicity to freshwater and marine animals are reviewed. New data on nitrate toxicity to the freshwater invertebrates Eulimnogammarus toletanus, Echinogammarus echinosetosus and Hydropsyche exocellata are also presented. The main toxic action of nitrate is due to the conversion of oxygen-carrying pigments to forms that are incapable of carrying oxygen. Nitrate toxicity to aquatic animals increases with increasing nitrate concentrations and exposure times. In contrast, nitrate toxicity may decrease with increasing body size, water salinity, and environmental adaptation. Freshwater animals appear to be more sensitive to nitrate than marine animals. A nitrate concentration of 10 mg NO3-N/l (USA federal maximum level for drinking water) can adversely affect, at least during long-term exposures, freshwater invertebrates (E. toletanus, E. echinosetosus, Cheumatopsyche pettiti, Hydropsyche occidentalis), fishes
(Oncorhynchus mykiss, Oncorhynchus tshawytscha, Salmo clarki), and amphibians (Pseudacris triseriata, Rana pipiens, Rana temporaria, Bufo bufo). Safe levels below this nitrate concentration are recommended to protect sensitive freshwater animals from nitrate pollution. Furthermore, a maximum level of 2 mg NO3-N/l would be appropriate for protecting the most sensitive freshwater species. In the case of marine animals, a maximum level of 20 mg NO3-N/l may in general be acceptable. However, early developmental stages of some marine
invertebrates, that are well adapted to low nitrate concentrations, may be so susceptible to nitrate as sensitive freshwater invertebrates.
from https/golias.net/akvaristika/docs/Nitrate toxicity to aquatic animals.pdf

Simultaneous exposure to nitrate and low pH reduces the blood oxygen-carrying capacity and functional performance of a freshwater fish
DanielF.GomezIsaza,RebeccaL.CrampandCraigE.Franklin*
School of Biological Science, The University of Queensland, Brisbane, Queensland 4072, Australia
*Corresponding author School o fBiological Science, TheUniversity of Queensland, Brisbane, Queensland 4072,Australia.
Email: [email protected]

..........................................................................................................................................................
Humana ctivities present aquatic species with numerous of environmental challenges,including xcessive nutrient pollution
(nitrate) and altered pH regimes (freshwater acidification). In isolation, elevated nitrate and acidic pH can lower the blood
oxygen-carrying capacity of aquatic species and cause corresponding declines in key functional performance traits such as
growth and locomotor capacity. These factors may pose considerable physiological challenges to organisms but little is known
about their combined effects. To characterise the energetic and physiological consequences of simultaneous exposure to
nitrate and low pH, we exposed spangled perch (Leiopotherapon unicolor) to acombination of nitrate (0,50 or100 mgL−1) and
pH (pH7.0 or 4.0) treatments in a factorial experimentaldesign.Blood oxygen-carrying capacity (haemoglobin concentration,
methaemoglobin concentrations and oxygen equilibrium curves), aerobicscope andfunctional performance traits (growth,
swimming performance and post-exercise recovery) were assessed after 28 days of exposure. The oxygen-carrying capacity
of fish exposed to elevated nitrate (50 and 100 mg L−1) was compromised due to reductions in haematocrit, functional
haemoglobin levels and a 3-fold increase in methaemoglobin concentrations. Oxygen uptake was also impeded due to a
right shift in oxygen–haemoglobin binding curves of fish exposed to nitrate and pH 4.0 simultaneously. A reduced blood
oxygen-carrying capacity translated to a lowered aerobic scope, and the functional performance offish (growth and 000swimming
performance and increased post-exercise recovery times) was compromised by the combined effects of nitrate and low pH.
These results highlight the impacts onaquatic organisms living in environments threatened by excessive nitrate and acidic pH
conditions.
from https://academic.oup.com/conphys/article-pdf/8/1/coz092/33832357/coz092.pdf

Kellock, Kristen A., Adrian P. Moore, and Robert B. Bringolf. "Chronic nitrate exposure alters reproductive physiology in fathead minnows." Environmental Pollution 232 (2018): 322-328.

Abstract

Nitrate is a ubiquitous aquatic pollutant that is commonly associated with eutrophication and dead zones in estuaries around the world. At high concentrations nitrate is toxic to aquatic life but at environmental concentrations it has also been purported as an endocrine disruptor in fish. To investigate the potential for nitrate to cause endocrine disruption in fish, we conducted a lifecycle study with fathead minnows (Pimephales promelas) exposed to nitrate (0, 11.3, and 56.5 mg/L (total nitrate-nitrogen (NO3-N)) from <24 h post hatch to sexual maturity (209 days). Body mass, condition factor, gonadal somatic index (GSI), incidence of intersex, and vitellogenin induction were determined in mature male and female fish and plasma 11-keto testosterone (11-KT) was measured in males only. In nitrate-exposed males both 11-KT and vitellogenin were significantly induced when compared with controls. No significant differences occurred for body mass, condition factor, or GSI among males and intersex was not observed in any of the nitrate treatments. Nitrate-exposed females also had significant increases in vitellogenin compared to controls but no significant differences for mass, condition factor, or GSI were observed in nitrate exposed groups. Estradiol was used as a positive control for vitellogenin induction. Our findings suggest that environmentally relevant nitrate levels may disrupt steroid hormone synthesis and/or metabolism in male and female fish and may have implications for fish reproduction, watershed management, and regulation of nutrient pollution.
from Institutional Access required for full paper. Or you can pay for it.

I have more papers on a crayfish, turbot, rainbow trout, Cyprinus carpio (commoncarp), Clarias gariepinus and zebrafish larvae and wigglersto small free swimmers/

 

[anewbie]

Abstract

Nitrate is a ubiquitous aquatic pollutant that is commonly associated with eutrophication and dead zones in estuaries around the world. At high concentrations nitrate is toxic to aquatic life but at environmental concentrations it has also been purported as an endocrine disruptor in fish. To investigate the potential for nitrate to cause endocrine disruption in fish, we conducted a lifecycle study with fathead minnows (Pimephales promelas) exposed to nitrate (0, 11.3, and 56.5 mg/L (total nitrate-nitrogen (NO3-N)) from <24 h post hatch to sexual maturity (209 days). Body mass, condition factor, gonadal somatic index (GSI), incidence of intersex, and vitellogenin induction were determined in mature male and female fish and plasma 11-keto testosterone (11-KT) was measured in males only. In nitrate-exposed males both 11-KT and vitellogenin were significantly induced when compared with controls. No significant differences occurred for body mass, condition factor, or GSI among males and intersex was not observed in any of the nitrate treatments. Nitrate-exposed females also had significant increases in vitellogenin compared to controls but no significant differences for mass, condition factor, or GSI were observed in nitrate exposed groups. Estradiol was used as a positive control for vitellogenin induction. Our findings suggest that environmentally relevant nitrate levels may disrupt steroid hormone synthesis and/or metabolism in male and female fish and may have implications for fish reproduction, watershed management, and regulation of nutrient pollution.
from Institutional Access required for full paper. Or you can pay for it.

I have more papers on a crayfish, turbot, rainbow trout, Cyprinus carpio (commoncarp), Clarias gariepinus and zebrafish larvae and wigglersto small free swimmers/

This is interesting; but one negative is 56.5 mg/L NO3-N is equiv to 240 mg/L of NO3 in our tanks - i.e, an extreme level indeed. Even measurements of 11.3 of NO3-N is equiv to 45 NO3 in our tank; still not a particularly low level (I'm converting NO3-N to NO3); Maybe this paper is suggesting 20ppm of NO3 isn't so bad ?