Origins and characteristics of dissolved organic matter fueling harmful dinoflagellate blooms revealed by δ13C and d/l-Amino acid compositions

Abstract

We measured the concentrations of dissolved inorganic and organic nutrients, dissolved organic carbon (DOC), total hydrolyzable amino acids (THAA), fluorescent dissolved organic matter (FDOM), phytoplankton pigments, and δ13C-DOC during the summer of 2019 in the harmful dinoflagellate bloom regions of the southern coast of Korea. In the harmful dinoflagellate bloom region, the concentrations of inorganic nitrogen were depleted, inhibiting the growth of diatoms, while the concentrations of dissolved organic components (nutrients, DOC, FDOM, and amino acids) which fuel dinoflagellates were unusually high. Thus, we attempted to investigate the origins and characteristics of DOM which fuels the harmful dinoflagellate blooms. The δ13C-DOC values (− 22.2‰ to − 18.2‰) indicate that the elevated DOC concentrations result from in-situ biological production rather than terrestrial inputs. The enantiomeric (D/L) ratios of THAA indicate that dissolved organic nitrogen was more labile in the early stage of harmful dinoflagellate bloom and became more refractory in the final stage. Our results suggest that the marine production of bioavailable DOM plays an important role in initiating and sustaining harmful dinoflagellate blooms.

StimulatedProrocentrum donghaiensecell growth byin-situmariculture dissolved organic matter

“…It is consistent with relevant field investigation that dissolved organic nutrients were a crucial factor for the dominance of dinoflagellates (Zhang et al, 2023). Furthermore, for the first time, our results provide the quantitative evidence to address the question that in-situ DOM play an important role in initiating and sustaining the dinoflagellate blooms (Park et al, 2022). Our results also provide clues to the underlying mechanism to address the frequent P. donghaiense bloom in Changjiang Esturay, which is intensively affected by riverine discharge containing complex nutrient compositions in organic forms (Zhou et al, 2022;Wang et al, 2023).…”

The phyto-bacterioplankton couple in a shallow freshwater ecosystem: Who leads the dance?

“…These changes were underscored by an increase of the bacterial abundances as well as a strong decrease in the richness and diversity indexes during the bloom event. Within the phycosphere, most of the interactions are believed to be driven by the recycling of dissolved organic matter (DOM), and can be modulated by DOM quantity and quality (Amin et al, 2015Zhang et al, 2019, by the composition of the daily extracellular phytoplankton production (EPP, Landa et al, 2014, Park et al, 2022 and by microbial senescence/predation (Simek et al, 2008;Seymour et al, 2017). The strong increase in phytoplanktonic OM during the bloom event, likely led to the reduction of the microbial diversity and changes in composition, with species that are well adapted to the new nutritional niche coming to dominate and to a competitive exclusion of other species (Teeling et al, 2012, Luria et al, 2016Nelson et al, 2021).…”

Changes in organic carbon properties during intense plankton blooms and macroaggregate formation in the coastal Adriatic Sea, Croatia (case studies in 2020-2022)

“…All that material was reported to be readily taken up by heterotrophic marine bacteria (Paliaga et al, 2021;Zhang et al, 2017), indicating a pool of labile OM. On the other hand, when we consider the whole bloom phenomena, for some dinoflagellates, a shift in labile OM was noted only early in the blooming phase and became more refractory toward the final stage (Park et al, 2022), whereas for M. leidyi, the final stage is only reported to add more labile material (Budiša et al, 2022;Condon et al, 2010).…”