MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps12330

Modeling transparent exopolymer particles aggregate dynamics and interactions with a pelagic food web

Temel Oguz*

*Email: temeloguz@gmail.com

ABSTRACT: Mechanistic understanding of the role of transparent exopolymer particles (TEP) in particular and macrogels in general on food web functioning is an overlooked aspect of the ecosystem modeling. The present study addresses this problem by a one-dimensional, vertically-resolved model that integrates the particle aggregation dynamics with the pelagic ecosystem structure. The model first simulates the observed annual food web structure of the mesotrophic Marmara Sea ecosystem in the absence of aggregation processes. This reference structure is then shown to reduce by about 40% in the presence of aggregation web formed by direct physical collision of detritus particles with live phytoplankton/bacteria cells. This type aggregation model approach therefore introduces adverse effects on the overall food web structure and is more restrictive in terms of aggregates formation. The alternative aggregation web considers transforming a fraction of dissolved organic matter into particulate form by the formation of two TEP size classes. They coagulate with phytoplankton/bacteria cells to form live biotic (BG) and with detritus to form abiotic (AG) aggregates, and additional coagulation of AG and BG particles to form macrogels. This system is shown to result in approximately twice higher aggregate concentrations, to facilitate stronger particle sedimentation to deep sea (quantified by AG concentrations) and higher food availability for macrozooplankton (quantified by BG concentrations). It also maintains the reference food web structure with only minor changes. Therefore, the present study demonstrates feasibility of coupling of food web models with a simplified TEP-based aggregation model.