Ocean acidification and ammonium enrichment interact to stimulate a short-term spike in growth rate of a bloom forming macroalga

Introduction The coastal macroalgal genus, Ulva , is found worldwide and considered a nuisance algal genus due to its propensity for forming vast blooms. response of ocean acidification (OA) concern, particularly with nutrient enrichment, as these combined drivers may enhance blooms because increased availability dissolved inorganic resources. Methods We determined how suite physiological parameters were affected by OA ammonium (NH 4 + ) enrichment in 22-day laboratory experiments gain mechanistic understanding growth, assimilation, photosynthetic processes. predicted change across range pCO 2 NH scenarios ascertain bloom potential under future climate regimes. Results During the first five days there was positive synergy between which could accelerate initiation an bloom. After day 5, growth rates declined overall no effect nor their interaction. acted synergistically increase NO 3 - uptake rates, have contributed days. Under saturating photosynthetically active radiation (PAR) used this experiment (500 μmol photon m -2 s -1 ), maximum negatively 2, be sensitivity light when high CO reduces energy requirements carbon acquisition. Activity CCMs decreased conditions indicating that nutrients play role alleviating photodamage regulating high-light intensities. Discussion This study demonstrates initiating or enhancing eutrophic environment highlights need interactions among light, OA,