Production and sedimentation of peptide toxins nodularin-R and microcystin-LR in the northern Baltic Sea

This seven-year survey was primarily targeted to quantification of production of nodularin-R (NOD-R), a cyclic pentapeptide hepatotoxin, in Baltic Sea cyanobacteria waterblooms. Additionally, NOD-R and microcystin-LR (MC-LR; a cyclic heptapeptide toxin) sedimentation rates and NOD-R sediment storage were estimated. NOD-R production (70–2450 μg m−3; ∼1 kg km−2 per season) and sedimentation rates (particles; 0.03–5.7 μg m−2 d−1; ∼0.3 kg km−2 per season) were highly variable over space and time. Cell numbers of Nodularia spumigena did not correlate with NOD-R quantities. Dissolved NOD-R comprised 57–100% of total NOD-R in the predominantly senescent, low-intensity phytoplankton blooms and seston. Unprecedentedly intensive MC-LR sedimentation (0.56 μg m−2 d−1) occurred in 2004. Hepatotoxin sedimentation rates highly exceeded those of anthropogenic xenobiotics. NOD-R storage in surficial sediments was 0.4–20 μg kg−1 (∼0.1 kg km−2). Loss of NOD-R within the chain consisting of phytoplankton, seston and soft sediments seemed very effective.