Dynamics of aquatic macrophytes and their contribution to carbon storage in La Zapatosa wetland, Colombia, under seasonal hydrological variation

Resumen

This study evaluated floristic composition, seasonal variation in macrophyte coverage (percentage of quadrat area occupied by each species), and the relationship between macrophytes, water physicochemical variables, and carbon stored in biomass in La Zapatosa Wetland (Cesar, Colombia), a RAMSAR site, during the rainy (October 2023) and dry (April 2024) seasons. Three stations (Chiriguaná, Chimichagua, and the Cesar River confluence) were sampled with two transects per station, each with five 1 m² quadrats; biomass was estimated gravimetrically, carbon by applying a fraction of 0.45 to ash-free organic matter, and physicochemical variables were measured in situ. Electrical conductivity ranged from 162 to 230 µS cm⁻¹ in the rainy season and from 322 to 489 µS cm⁻¹ in the dry season. Six genera in five families were identified, with higher richness and coverage in the rainy season. Floating species such as Neptunia oleracea and Eichhornia azurea dominated at higher water levels, whereas Hymenachne amplexicaulis tolerated water recession. Carbon stored in biomass, expressed as CO₂ equivalent, was highest in the rainy season at the Cesar River confluence (96.95 g m⁻²), followed by Chimichagua (69.51 g m⁻²) and Chiriguaná (60.07 g m⁻²). Principal component analysis showed that stored carbon is modulated by tissue quality, architecture, and life form, and by gradients of turbidity, electrical conductivity, temperature, and pH. In the sectors evaluated, macrophytes store relevant amounts of carbon, although potential methane emissions must be considered; their conservation is key to enhancing wetland resilience to climate change.

Keywords: flood pulse, hydrophytes, multivariate ordination, plant biomass, Ramsar site.