Are upwelling systems an underestimated source of long chain omega‐3 in the ocean? The case of the southern Benguela upwelling system
Puccinelli, E.; Fawcett, S.E.; Flynn, R.F.; Burger, J.M.; Delebecq, G.; Duquesne, N.; Lambert, C.; Little, H.; Pecquerie, L.; Sardenne, F.; Wallschuss, S.; Soudant, P. (2023). Are upwelling systems an underestimated source of long chain omega‐3 in the ocean? The case of the southern Benguela upwelling system. JGR: Biogeosciences 128(9): e2023JG007528. https://dx.doi.org/10.1029/2023jg007528
Additional data:
In: Journal of Geophysical Research-Biogeosciences. AMER GEOPHYSICAL UNION: Washington. ISSN 2169-8953; e-ISSN 2169-8961, more
|   |
| Author keywords |
fatty acid; nitrogen cycling; food web; upwelling; phytoplankton productivity; nanoplankton |
| Authors | | Top |
- Puccinelli, E.
- Fawcett, S.E.
- Flynn, R.F.
- Burger, J.M.
|
- Delebecq, G.
- Duquesne, N.
- Lambert, C.
- Little, H.
|
- Pecquerie, L.
- Sardenne, F.
- Wallschuss, S.
- Soudant, P.
|
| Abstract |
The Benguela upwelling system (BUS) is one of the world's most productive ecosystems, supporting globally relevant fisheries. The BUS marine community is modulated by the availability of nutrients and omega-3 long chain polyunsaturated fatty acid (hereafter, LC omega-3). Phytoplankton growth in the BUS can be supported by upwelled nitrate, a new nitrogen (N) source to the surface, or by recycled N such as ammonium. Preferential assimilation of one N source over another may yield differences in LC omega-3 production between high and low food-quality species. To evaluate how upwelling and the N source(s) consumed by phytoplankton influence LC omega-3 production, we sampled a BUS anchor station daily for 10 days. Upwelling on days 5–7 supplied high concentrations of nutrients to the surface, while pre- and post-upwelling, surface waters were stratified and nutrient concentrations were low. LC omega-3 and phytoplankton concentrations were near-zero during upwelling, and elevated pre- and post-upwelling. Throughout our sampling, nanoplankton (2.7–10 µm) dominated primary production (30–95%), relying mainly on nitrate to support their growth. Surface LC omega-3 concentrations reached peaks of 215 and 175 µg L −1 pre- and post-upwelling, up to 10 times higher than previous measurements from the BUS (<5 µg L−1). Pre-upwelling, non-diatom trophic markers (18:1 n − 9, 18:4 n − 3, 18:5 n − 3) were dominant, with a switch over just two days to diatom trophic markers post-upwelling (16:1 n − 7, 16:2 n − 4, 16:2 n − 7, 16:3 n − 4, 16:4 n − 1). This study reveals the key role of upwelling in promoting phytoplankton LC omega-3 production, which is tightly coupled to the supply of new nitrate. Additionally, the high observed LC omega-3 concentrations suggest that global LC omega-3 production is underestimated. |
|
