Reef Chemistry Question of the Day #28 Toxic?

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #28

Which of the following is likely to be the most acutely (rapidly) toxic to a typical reef aquarium fish?
Pick all that apply.


A. 2 ppm ammonia
B. 20 ppm nitrite
C. 50 ppm nitrate
D. 19,000 ppm chloride
E. 2,700 ppm sulfate

Good luck!


















.

 

[mike007]

a d e

 

[cagdason]

I would say a,d ,e too

 

[ritter6788]

B, a

 

[LetItReef]

A, 2 ppm ammonia

 

[leptang]

D is my guess

 

[DRThompson]

A - ammonia

 

[chrisfraser05]

A and b.

Most things won't notice c, but even those that do will be slow.
D is around normal levels and e although triple the sea water composition it's not acutely toxic from what I gather.

 

[Eienna]

I...honestly don't know XP

 

[reggaedrummin]

My guess is a ammonia though it depends on how your tank is stocked

 

[kireek]

I am going to guess E,Sulfates.Because common household products like to brag "Contains no sulfates".And when I worked for a LFS I tested reef water at 160 ppm Nitrates and the guy still had living fish.

 

[ahmed.boomer]

E followed by B, A, C, D. Depends on inverts in tank.

 

[hart24601]

B!

Something to do with witchcraft?

 

[Randy Holmes-Farley]

And the answer is......

A. 2 ppm ammonia

2 ppm ammonia is quite toxic to a lot of fish.

19,000 ppm chloride and 2,700 ppm sulfate are normal levels for these in seawater.

Despite the fact that nitrite is quite toxic in fresh water systems, it is not especially toxic in seawater.

Nitrate is also not very toxic.

These have more:

Toxicity of Ammonia
Ammonia is very toxic to marine fish. The mechanisms of toxicity are complicated and are an active area of continued investigation by researchers. Its effects include damage to the gills, resulting in poor gas exchange, ion regulation and blood pH regulation.14 Other effects include hampering oxygen delivery to tissues, disrupting metabolism and toxicity to the nervous system that causes hyperactivity, convulsions and death. Ammonia can also be very toxic to many other organisms found in reef aquaria.

Toxicity can be measured and reported in many ways. One common way to measure acute toxicity is to measure how high the concentration needs to be in order to kill half of the organisms in a given time period. A commonly used time period is 96 hours (four days). Such data are called the 96 h LC50 (LC stands for Lethal Concentration, 50 meaning 50% killed).

The other complication that comes with ammonia's toxicity is the relative amount of free ammonia and ammonium ion. While ammonium ion may be toxic to marine fish, it is probably less toxic than free ammonia, and toxicity data are often reported only for the concentration of free ammonia. Aquarists should recognize, however, that such data may not be appropriate if the pH used in the test, or the situation to which it will be applied, deviates significantly from normal seawater's pH (as in a shipping bag, for example, whose pH may be well below pH 8.2, and whose toxicity may actually be coming from ammonium, and not the low concentration of free ammonia). Nevertheless, many scientific articles report ammonia toxicity in ppm (or mg/L) NH3-N. It may also be reported as just ppm NH3.

Marine fish generally have 96 h LC50 levels that range from about 0.09 to 3.35 ppm NH3-N. That result is not particularly different from the range observed for freshwater fish, 0.068 to 2.0 ppm NH3-N. Remember that these values are ppm NH3-N, and at pH 8.2, the marine range becomes 1.3 to 50 ppm total NH4-N because only 7% of the total ammonia in seawater is present as free ammonia.

Concentrations of ammonia that are not acutely lethal can still cause significant problems for fish. Salmon in seawater at pH 7.8, for example, show changes in white blood cells and various blood chemicals, and were more prone to disease, when exposed to sublethal concentrations of ammonia. Consequently, aquarists should strive to keep ammonia concentrations well below lethal levels.

Ammonia and the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com


How Toxic is Nitrite to Fish?

For the reason described above, nitrite is considerably more toxic to many freshwater fish (Table 1) than it is to most marine species (Table 2). The data in these tables are primarily the LC50, which is the concentration at which 50% of the test organisms die (24-h LC50 is the concentration that kills half of the tested organisms within 24 hours). As Table 1 shows, some freshwater fish can die at nitrite levels below 1 ppm. This toxicity is the reason many aquarists worry about nitrite in aquaria. It can be a significant problem in freshwater aquaria. Tests in marine species, however, showed the toxicity to be much lower. None of the thirteen marine fish species for which I could find nitrite toxicity data had LC50 values below 100 ppm, and half had LC50 values of 1,000 - 3,000 ppm or more.

Death is, of course, a very crude indicator of toxicity. An aquarium's nitrite level should not come anywhere close to the LC50 value, because less severe toxicity can occur even at levels below that. In the previous section, I showed data on one marine species in which biochemical effects could be detected at levels well below concentrations that caused death. We saw, for example, a rise in methemoglobin at values as low as 46 ppm nitrite. However, the point remains valid that marine species are orders of magnitude less susceptible to the effects of nitrite than are many freshwater species. The marine aquaculture industry often uses a rough guideline that the safe rearing level of many compounds is a factor of 10 or less than their LC50.

In examining ammonia, nitrite and nitrate toxicity in marine species, one might think to look at the effects on larval fish to see if they are more sensitive. In examining the incidence of the larvae's first feeding after hatching, and the 24-h LC50, it was found that for seven different marine species, only ammonia was found to be toxic at concentrations that might possibly be encountered in aquaculture facilities.

Table 3 brings out the distinction between freshwater and seawater organisms most clearly. In these tests, two fish and one shrimp species that are able to live in both freshwater (or brackish water) and seawater were tested for toxicity at different salinities. At least for these three species, it is clearly shown that nitrite is much more toxic in freshwater (or at lower salinity) than in seawater, even to the same species.

In the only published article that I could find showing toxicity tests to typical reef aquarium fish, Tom Frakes and Bob Studt exposed tank-raised clownfish (Amphiprion ocellaris; Figure 2) to nitrite concentrations ranging from 0 to 330 ppm in artificial seawater. Two of five fish died after a few days at 330 ppm, giving an LC50 not appreciably different from the other species listed in Table 1. At 33 ppm (the next dose down from 330 ppm), the fish were lethargic and breathing with difficulty, but otherwise experienced no lasting problems. At 3.3 ppm nitrite no effects were observed.

Nitrite and the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com


Effects Of Elevated Nitrate In Aquaria
In addition to the concerns described above relating to the growth of potentially undesirable organisms that may be promoted by elevated nitrate (especially algae and dinoflagellates), corals can be impacted by nitrate. Many corals may not be bothered by elevated nitrate, or may even grow more rapidly with the readily available nitrogen. But in certain corals, especially those that calcify, there may be negative effects from elevated nitrate.

In most cases where nitrate levels have been examined in relation to the growth of calcerous corals, the effects have been reasonably small, but significant. Elevated nitrate has been shown to reduce the growth of Porites compressa (at less than 0.3-0.6 ppm nitrate), but the effect is eliminated if the alkalinity is elevated as well (to 4.5 meq/L). One explanation is that the elevated nitrate drives the growth of the zooxanthellae to such an extent that it actually competes with the host for inorganic carbon (used in photosynthesis and skeletal deposition). When the alkalinity is elevated, this competition no longer deprives the host of needed carbon.

A second study on Porites porites and Montastrea annularis tends to support this hypothesis. They showed that elevated nitrate caused an increase in photosynthesis, in the density of zooxanthellae, and in their chlorophyll a and c2, and total protein, while skeletal growth decreased considerably.18 This effect may not be generally true, however, since elevated nitrate does not appear to have decreased calcification in Acropora cervicornis (though the experiments were carried out under very different conditions).19


One very recent study 20 on Porites cylindrica has reported that elevated nitrate (0.9 ppm) did not increase the rate of photosynthesis or zooxanthellae density, but actually decreased it, contrary to the previous literature. They do not provide an explanation of why their results were different, though they indicated that the corals may have been expelling zooxanthellae, which would confound some of the results. Additionally, all of the corals in the study were stressed in that they lost significant biomass during the study compared to when first collected in the wild. Because of that effect, I do not put much faith in how this study may relate to aquaria where corals are growing rapidly.

Aquarium Chemistry: Nitrate in the Reef Aquarium ? Advanced Aquarist | Aquarist Magazine and Blog