Increased nutrients from aeolian‐dust and riverine origin decrease the CO₂‐sink capacity of coastal South Atlantic waters under UVR exposure

Abstract

Increases in ultraviolet radiation (UVR) levels due to the ongoing stratification of water bodies and higher nutrient concentrations either through riverine or aeolian‐dust‐inputs are expected in the near future in coastal surface waters. Here, we combined remote‐sensing data of particulate organic carbon (POC; 1997–2016 period), observational data of solar radiation (1999–2015 period), and a mid‐term experimental approach with coastal plankton communities from South Atlantic Ocean (SAO) to test how the interaction between increased nutrients by riverine and aeolian‐dust inputs and high UVR may alter the community dynamics and the CO2 sink capacity of these ecosystems in the future. Our results show a decline ∼ 27% in the sink capacity of the coastal ecosystems regardless of the nutrient source considered and under high UVR levels. This decreased CO2 uptake was coupled with a high dynamic photoinhibition and dark recovery of photosystem II and shifts in the community structure toward the dominance by nano‐flagellates. Moreover, remote‐sensing data also evidences an incipient tipping point with decreasing POC values in this area over the annual planktonic succession. Therefore, we propose that to continue this climate and human‐mediated pressure, these metabolic responses could be strengthened and extended to other productive coastal areas.

Impact of Increased Nutrients and Lowered pH on Photosynthesis and Growth of Three Marine Phytoplankton Communities From the Coastal South West Atlantic (Patagonia, Argentina)

“…It is recognized that the r-strategists allocate a large portion of resources to cell division, which is advantageous in a variable environment such as PU, whereas K-strategists would be favored in less variable environments such as PM and IE. Cabrerizo et al (2018) studied the impact of different nutrient sources (aeoline vs. riverine) on community structure, and determined that the combination of high solar UVR and nutrient addition decreased CO 2 sink capacity of coastal ecosystems in the SWAO by 27%, by changing the phytoplankton community toward heterotrophic nanoflagellates. Our Future generally stimulated the increase of biomass and carbon incorporation in the three sites, in spite of the dominance of different phytoplankton groups (Figures 3, 4).…”

Temporal Characterization of Dust Activity in the Central Patagonia Desert (Years 1964–2017)

“…It is expected that there will be an improvement in the characterization of dust activity in the Patagonia area. Local groups are carrying out more dedicated studies of dust and its impacts downwind (Cabrerizo et al, ; Crespi‐Abril et al, ; Montes et al, ; Paparazzo et al, ). Also, the availability of better remote sensing tools, such the TropOMI sensor, a similar sensor to OMI with improved spatial resolution and the geostationary GOES‐E sensor with a high temporal (at least every 30 min) and spatial resolution than previous sensors, will all help to better characterize dust activity and transport from this area.…”

“…This is relevant for the marine ecosystem in the Patagonian sea shelf because this sector has high levels of primary productivity (Garcia et al, 2008) and it is an important contributor to the global ocean CO 2 uptake from the atmosphere (Bianchi et al, 2009). Recent studies highlighted the sensitivity of this ecosystem to the deposition of nutrients contained in Patagonian dust (Cabrerizo et al, 2017;Paparazzo et al, 2017).…”

Dual role of DOM in a scenario of global change on photosynthesis and structure of coastal phytoplankton from the South Atlantic Ocean

“…The coastal South Atlantic area receives high inputs of terrigenous material from riverine origin, which brings also nutrients from anthropogenic-related activities such as agriculture and fishing (Bermejo et al, 2018). In addition, the Patagonian dust, which carries micronutrients such as Fe (Johnson et al, 2011) and other nutrients, can significantly affect the biological activity (i.e., photosynthesis and respiration) of phytoplankton (Cabrerizo et al, 2017). Therefore, it is of great importance to evaluate the role that the terrigenous material has on the lower levels of the aquatic food web.…”