In order to obtain detailed information on the interaction of bivalent cations with alginates especially the effects of sequence and acetylation degree the several types of alginates were treated with different solutions of manganese(II)and analysed by 13C-nuclear magnetic resonance (NMR)spectroscopy. The usage of paramagnetic manganese(II) ions lead to a strong influence on the NMR signals of all adjacent nuclei which is based on the dipolar coupling with electron spins of the paramagnetic species. It was found that there are different carbons involved in the interaction of polymannurante and polyguluronate. In alternating sequences the GM/MG parts of the alginates show the strongest interaction with manganese. Additionally it was found that the acetylated parts of the chain show no interaction with the paramagnetic ion. The strong affinity of manganese to the GM/MG-pairs could be a reason for the founded preference of the bacteria to produce alternating alginates. That applies for the amount of the acetyl groups in the alginate. The acetylation degree is another tool to affect the stability of the alginate/cation complexes and therewith for the gelmatrix of alginate/cation gels