Effects of crude oil on survival, morphology, and anatomy of two aquatic macrophytes from the Amazon floodplains

Abstract

Aquatic herbaceous macrophytes grow in profusion in the Amazon fertile varzea floodplains. A large number of species occur but only a few are particularly abundant, supporting food chains, contributing substantially to carbon and nutrient cycles. Their growth and role in the ecosystem depend, among other, on its life cycles and habits, floating or semi-aquatic. Although in the last decades, petroliferous activity intensified in the Central Amazon region and so did oil spills, the effect of petroleum on the native aquatic plants is unknown. The present study was designed to test experimentally the survival and morpho-anatomical modifications of the free floating water hyacinth Eichhornia crassipes and the semi-aquatic grass Echinochloa polystachya to 10 different concentrations of crude oil. Higher concentrations of crude oil caused the mortality in both species; however, lethal dose (LD 50 ) values showed that E. polystachya was more sensitive than E. crassipes. Despite the higher tolerance of E. crassipes, the inhibition of root and leaf growth as well as anatomical modifications in leaves were registered in higher concentrations. Additionally, the oil caused a reduction in leaf numbers in both species. Although mortality of the floating species was lower, it may increases over time, since important alterations in morphology and anatomy occurred. These results show that oil spills in the Amazon varzea can cause severe alterations in the aquatic flora and in the floodplain dynamics.

United States Gulf of Mexico Coastal Marsh Vegetation Responses and Sensitivities to Oil Spill: A Review

“…While mortality of floating species was reported to be low, it may increase over time due to the alterations in plant morphological and anatomical features that are critical for plant functioning. Data on other aquatic species presented by Lopes et al [25] and Lopes and Piedade [26] showed that oil spills led to substantial changes in the mixture of aquatic species as well as the dynamics of vegetation in the floodplain. In addition, Martin et al [27] reported that Ruppia maritima, a common inhabitant of salt marsh ponds and protected embayments in Louisiana salt marshes, was sensitive to oiling.…”

“…These species may have various level of sensitivity to oiling [25][26][27]. For instance, Lopes et al [25] reported that floating Eichhornia crassipes, an invasive plant also common to Louisiana salt marshes, was sensitive to high concentrations of crude oil. Root and leaf growth were inhibited and anatomical modifications in leaves were noted under high oil concentrations.…”

Normalized Difference Vegetation Vigour Index: A New Remote Sensing Approach to Biodiversity Monitoring in Oil Polluted Regions

“…Several researchers have propounded theories on how TPH influences chlorophyll content in affected plants. Investigations of crude oil effect on plant anatomy such as [155][156][157] discovered structural deformations in the form of thickening of the epicuticular region, compression of the palisade and spongy parenchyma, compression of the vascular bundles, reduction of intercellular air spaces, distortion and reduction of the stomata. These changes generally inhibit chlorophyll synthesis thereby affecting plant growth and productivity [155].…”

Effects of Pollution on Freshwater Organisms

“…Hydrocarbons (PAHs) Lopes et al (2009) tested the two Amazon floodplain macrophytes, Eichhornia crassipes and Echinochloa polystachya, for their responses to crude oil exposure. E. polystachya was more sensitive than E. crassipes in lethality testing, but E. crassipes showed inhibition of root and leaf growth, as well as anatomical modifications in the leaves exposed to higher concentrations.…”