Cobalt
Cobalt is an essential trace element that can have negative effects even at slightly elevated concentrations.
The concentration in natural seawater at the surface is extremely low at 0.03 µg/l1 – therefore cobalt is considered an ultra-trace element. The concentration is highest at the sea surface and decreases with increasing depth1. Cobalt occurs as a free ion but is also a central component of the important B-provitamin cyanocobalamin (vitamin B12), see Figure 1. New studies show a connection between cyanocobalamin and the growth of phytoplankton2.
As an important co-factor for enzymatic reactions, cobalt (or cyanocobalamin) is essential for many organisms.
Scientific studies show significant growth inhibition in the studied stony corals Stylophora pistillata and Acropora muricata at a cobalt concentration of 0.2 µg/l – a low pH value (7.8) had an even stronger effect here. 3 Even robust animals like Aiptasia anemones show negative effects (bleaching, tentacle retraction) at significantly elevated cobalt concentrations.4
Figure 1: The structure of cyanocobalamin (precursor to vitamin B12), an important form of organically bound cobalt
Method of analysis
Detection strength Oceamo Classic Laboratory Analysis (ICP-OES): Good sensitivity when measuring cobalt; detection limit about 0.5 µg/l. However, this is not sufficient to reliably detect deficiencies. Moderately elevated concentrations can be reliably detected.
Detection strength Oceamo ICP-MS Seawater Analysis: very high sensitivity, detection limit in the range of 0.005 µg/l. Deficencies can also get reliably detected.
Our recommendation:
Measurement quality in the Oceamo laboratory:
Measurement quality in the Oceamo laboratory:
Excellent accuracy and reproducibility in the Oceamo ICP-MS seawater analysis, even at extremely low concentrations in the range of the target concentration (see graphs).
Method: ICP-MS
Mean accuracy @ 1ppb:95.61(±3.69)% (9 Measurements split over 3 days)
Mean accuracy @ 5 ppb:95.82(±1.48)% (9 Measurements split over 3 days)
Mean accuracy @ 10 ppb:96.35(±1.31)% (9 Measurements split over 3 days)
Mean accuracy @ 0.074 ppb:94.97(±9.35)% (18 Measurements on 18 consecutive days, CRM data)
Stability of cobalt in the sample:
No significant change in cobalt concentration was observed in real samples over 8 days at room temperature or at -20°C (see graph).
Sample stability Cobalt
Seawater
Target concentration in the reef aquarium & dosing:
We recommend a cobalt concentration in the marine aquarium of 0.05–0.2 µg/l, which is significantly above the natural concentration. This ensures sufficient availability of this important trace element without reaching problematic concentration levels. Cobalt is contained in Oceamo Regulator A&O and Oceamo Reactor A&O in both inorganic and organically bound form. Targeted additional dosing is rarely necessary and can be done with Oceamo Custom Elements. Due to the low target concentration, cobalt is present in sufficient quantities in many aquariums even without conscious dosing, or is even slightly elevated (due to contamination in salts, etc.). Cobalt should never be dosed based on a “not detectable” result of an ICP-OES analysis, as there is a risk of overdosing!
Potential problems
Signs of cobalt deficiency: Stagnating growth
Signs of cobalt overdose: Significant growth stagnation, tissue loss, bleaching/expulsion of zooxanthellae
Potential sources
Elevated cobalt levels in the aquarium occasionally occur, and can have the following reasons:
- Overdosing through trace element supplements.
- Contaminants in salts, water additives, or feed.
- Corrosion of alloys and magnets.
Even slightly elevated levels can lead to significant growth reduction, while highly elevated levels can cause coral bleaching and tissue loss. Cobalt can be bound with iron-based adsorbents (GFO)5, organic cobalt compounds are likely to bind to activated carbon.
Cobalt deficiency is rare: In such cases, cobalt should be regularly dosed (with Oceamo Custom Elements).
Cobalt should never be dosed based on a “not detectable” result of an ICP-OES analysis, as there is a risk of overdosing!
Freshwater
n/a
Potential problems
n/a
Potential sources
n/a
Literature/References:
1) Periodic table of elements in the ocean. (2024).
2) Barber-Lluch, E. et al. Variability of vitamin B12 concentrations in waters along the Northwest Iberian shelf. Reg. Stud. Mar. Sci. 42, 101608 (2021).
3) Biscéré, T. et al. Responses of Two Scleractinian Corals to Cobalt Pollution and Ocean Acidification. (2015) doi:10.1371/journal.pone.0122898.
4) Howe, P. L., Reichelt-Brushett, A. J. Clark, M. W. Investigating lethal and sublethal effects of the trace metals cadmium, cobalt, lead, nickel and zinc on the anemone Aiptasia pulchella, a cnidarian representative for ecotoxicology in tropical marine environments. Mar. Freshw. Res. 65, 551–561 (2014).
5) Denk, C. Reactor media under the ICP-MS magnifying glass. https://en.oceamo.com/reaktormedien2 (2022).
