Environmental stress and eutrophication in freshwater wetlands: evidence from carbon and nitrogen stable isotopes in cattail (Typha domingensis Pers.)

Abstract

Background: Florida's Everglades is a vast freshwater peatland that has been impacted by the alterations of hydrological pattern and water quality which led to changes in plant species composition and biodiversity. In this study, carbon and nitrogen stable isotopes (δ 13 C and δ 15 N) in cattail (Typha domingensis) are evaluated as indicators of environmental changes in the Everglades wetlands along nutrient and hydrological gradients represented by reference sites with total phosphorus (TP) < 10 μg L −1 , transition sites with TP ≥ 10 μg L −1 < 20 μg L −1 and impacted sites with TP ≥ 20 μg L −1 which differed in hydrology or habitats (marsh and canal). Results: Cattail δ 13 C values decreased significantly from reference (-24.1‰), transition (-26.8‰) to the impacted sites (-28.2‰). In contrast, δ 15 N values increased significantly from reference (-5.2‰), transition (2.4‰) to the impacted site (5.9‰). In response to a poor hydrological condition, cattail in marsh area displayed 13 C enrichment (-26.0‰) and 15 N depletion (0.2‰). By contrast, cattail grown in the canal sites with favorable hydropattern displayed 13 C depletion (-27.6‰) and 15 N enrichment (5.9‰) from the canal sites with more favorable hydrological condition. Conclusions: The different patterns for the changes in δ 13 C and δ 15 N in cattail suggested that increased nutrients led to increased stomatal conductance and 13 C fractionation during carbon uptake and decreased 15 N fractionation with increasing nitrogen demand while poor hydrological condition coupled with low nutrients led to reduced plant growth indicated by higher δ 13 C and lower δ 15 N values. Findings from this study suggested that δ 13 C in emerged macrophytes such as cattail can be used as an indicator for environmental stress while δ 15 N is a robust indicator for wetland eutrophication.

Eutrophication and sediment–water exchange of total petroleum hydrocarbons and heavy metals of Hashilan wetland, a national heritage in NW Iran

“…The ratio of N:P in the water body (referred to as the "Redfield ratio") is an important indicator of which nutrient is limiting eutrophication. The high ratio of N:P which is greater than 16 indicates that P is most likely a limiting nutrient to plant growth (Zheng et al 2019). The N:P ratio in all the water samples was higher than the Redfield ratio of 16, and was thus P limited.…”

Inner Asian agro-pastoralism as optimal adaptation strategy of Wupu inhabitants (3000–2400 cal BP) in Xinjiang, China

“…Plants of Typha sp. are aquatic species and generally grow in shallow water near the river and lake bank or in wetland (Zheng et al, 2019). The presence of these two plants in the archaeological record in arid southern Xinjiang may be a reliable indicator of water availability and the presence of oases in the local landscape during the period of occupation.…”

Diatom responses to river water quality in the Kruger National Park, South Africa

“…Additionally, water quality is a key driver of productivity in aquatic systems -for instance if a system becomes moderately nutrient enriched, increased productivity may support several organisms depending on photosynthetic organisms. In some instances, when primary productivity is high (eutrophication), this may lead to problems such as algae blooms with associated toxic effects and trophic disruptions (Dallas & Day 2004;Hart 2006, Tsu-Chuan & Clark 2018Zheng et al 2019).…”