Marine phytoplankton is responsible for approximately half of the annual global net primary production and thus represent one of the main sources of organic matter in the ocean. The composition of phytoplankton-derived organic matter is of utmost importance for marine ecosystems, as it sustains the majority of non-photosynthetic life in the sea. In temperate regions, such as the Mediterranean basin, phytoplankton communities exhibit seasonal patterns driven by biotic and abiotic factors. These patterns are well identified, with several groups such as diatoms, dinoflagellates, coccolithophores, haptophytes and cryptophytes exhibiting contrasting seasonal changes of abundance and dominance. Despite its biogeochemical relevance, the impact of these changes on organic matter composition remains largely unknown. Optical properties have long been used to characterize the fluorescent organic matter (FOM) pool. However, most studies focus on the dissolved FOM fraction (FDOM), disregarding the possible fluorescence of phytoplankton cells and other particles excluded by filtration. In order to assess the effects of phytoplankton ecological succession on the composition of particulate and dissolved FOM, we compared the composition of phytoplankton communities with measurements of organic matter fluorescence in filtered and unfiltered samples from the Blanes Bay Microbial Observatory (BBMO) from 2011 to 2017. We will discuss how these FOM dynamics are related to phytoplankton abundance and seasonal succession as well as to abiotic factors such as solar radiation, and how these dynamics may influence the fate and turnover of the organic matter in the sea

2nd Meeting of the Iberian Ecological Society (SIBECOL), 3-8 July 2022, Aveiro, Portugal

Peer reviewed