Impact of increased nutrients and lowered pH on photosynthesis and growth of three marine phytoplankton communities from the coastal South West Atlantic (Patagonia, Argentina)

MASUDA, T.; PRÁSIL, O.; VILLAFAÑE, V.E.; VALIÑAS, M.S; INOMURA, K.; HELBLING, E.W.

FRONTIERS IN MARINE SCIENCE

Frontiers Media SA

Año: 2021

2296-7745

Effect of global change variables on the structure and photosynthesis of phytoplanktoncommunities was evaluated in three different sites of the Patagonian coast of Argentina:enclosed bay (Puerto Madryn, PM), estuarine (Playa Unión, PU), and open waters (IslaEscondida, IE). We exposed samples to two contrasting scenarios: Present (nutrients atin situ levels) vs. Future (with lowered pH and higher nutrients inputs), and determinedgrowth and photosynthetic responses after 2 days of acclimation. Under the Futurecondition phytoplankton growth was higher in the estuarine site compared to thosein PM and IE. This effect was the most pronounced on large diatoms. While theincrease of photosynthetic activity was not always observed in the Future scenario,the lower photosynthetic electron requirement for carbon fixation (Φe,C = ETR/PmB) inthis scenario compared to the Present, suggests a more effective energy utilization.Long-term experiments were also conducted to assess the responses along a 4days acclimation period in PU. Diatoms benefited from the Future conditions and hadsignificantly higher growth rates than in the Present. In addition, Φe,C was lower after theacclimation period in the Future scenario, compared to the Present. Our results suggestthat the availability, frequency and amount of nutrients play a key role when evaluatingthe effects of global change on natural phytoplankton communities. The observedchanges in diatom growth under the Future scenario in PU and IE and photosynthesismay have implications in the local trophodynamics by bottom up control.