Sedimentary organic matter quality across the continental shelf off central Peru

Pérez A.; Carhuapoma W.; Marquina R.; Quipúzcoa L.; Gutiérrez D. · Journal of Soils and Sediments (2026) · DOI: 10.1007/s11368-026-04520-5

Resumen

Purpose: The biogeochemical characterization of sedimentary organic matter (OM) on continental shelves is fundamental for understanding organic matter cycling and benthic ecosystems functioning. This study assessed the composition, distribution, and biogeochemical state of organic matter (OM) along a bathymetric transect (48–178 m) across the central Peruvian continental shelf, beneath a highly productive coastal upwelling system and a persistent oxygen minimum zone (OMZ). Materials and methods: Total and hydrolysable fractions of carbohydrates, proteins, and lipids, as well as photosynthetic pigments (chlorophyll-a and pheopigments), were analyzed and integrated into biogeochemical indices: Biogeochemical Quality Index (BI); Lipid Index (LI), Carbohydrate-to-Lipid ratio (C/L), Chlorophyll-a to Pheopigments ratio (Chl-a/Pheo-a) and Biopolymeric Carbon Index (BPC) to evaluate OM quality, origin, bioavailability, and early diagenetic processes. Undisturbed 50 cm-length sediment cores were collected in triplicate at four stations during ENSO-neutral period, sectioned at 1 cm intervals for the uppermost 10 cm-depth, and analyzed using spectrophotometric and fluorometric techniques adapted for marine sediments. Results and discussions: The results suggest that sediments displayed a pronounced inner–outer shelf gradient: inner shelf sediments contained fresher, labile, and nutritionally rich OM, linked to high primary production and rapid burial, whereas outer shelf sediments showed selective preservation of lipids and refractory OM. Additionally, comparison with data obtained from the same study area suggests that temporal variability in phytopigments responded to oceanographic drivers (e.g. bathymetry, primary productivity, hydrodynamic, etc.) including anomalous events (e.g. post–La Niña and weak El Niño). These findings highlight the sensitivity of benthic biogeochemical processes to upwelling intensity and bottom-water oxygenation. Integration of hydrolysable fractions and biogeochemical indices may suggest strong benthic–pelagic coupling, selective OM degradation, and differential preservation along the shelf. These results underscore the interplay between primary productivity and sedimentary dynamics as key modulators of OM quality and distribution. Conclusions: This studyhighlights the key role of continental shelf sediments in carbon storage, nutrient recycling, and the biogeochemical processes that sustain benthic communities in highly productive upwelling systems. These findings underscore the importance of understanding sedimentary organic matter dynamics and their implications in the context of ongoing global warming. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2026.

Instituciones: Universidad Peruana Cayetano Heredia