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 very low at 0.03 µg/l1 – therefore cobalt is considered an ultra-trace element. The concentration is highest at the sea surface and declines with increasing depth1.
Cobalt is present as a free ion, but also forms 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 living 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 level Oceamo Classic laboratory analysis (ICP-OES): Good sensitivity in the measurement of cobalt; detection limit approx. 0.5 µg/l. However, this is not sufficient to reliably detect deficiencies. However, moderately elevated concentrations can be reliably detected.
Detection level Oceamo ICP-MS seawater analysis: very high sensitivity, detection limit in the range of 0.005 µg/l. Deficencies can also be 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 seawater aquarium of 0.05-0.2 µg/l, which is well above the natural concentration. This ensures a sufficient availability of this important trace element without entering in a problematic concentration range.
Cobalt ist in Oceamo Regulator A&O und Oceamo Reactor A&O sowohl in anorganischer Form als auch organisch gebunden enthalten. Eine gezielte zusätzliche Dosierung ist selten erforderlich und kann mit Oceamo Custom Elements erfolgen.
Due to the low target concentration, cobalt is present in sufficient quantities in many aquariums even without deliberate dosing, or is even slightly elevated (due to contamination in salts, etc.).
Cobalt should never be added on the basis of an ‘undetectable’ result from 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 values can lead to a significant reduction in growth, while strongly elevated values can cause bleaching of corals and tissue loss.
Cobalt can be bound with iron-based adsorbers (GFO)5, organic cobalt compounds are very 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 added on the basis of an ‘undetectable’ result from an ICP-OES analysis, as there is a risk of overdosing!
Freshwater
n/a
Potential problems
n/a
Potential sources
n/a
Literature/list of sources:
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).
With these products, you can influence the cobalt level:
Price range: €39,90 through €59,90 €
