Oil Pollution Affects the Central Metabolism of Keystone Vachellia (Acacia) Trees

Abstract

Vachellia (formerly Acacia) trees are native to arid environments in Africa and the Arabian Peninsula, where they often support the local animal and plant communities acting as keystone species. The aim of this study was to examine whether oil pollution affected the central metabolism of the native keystone trees Vachellia tortilis (Forssk.) and V. raddiana (Savi), as either adults or seedlings. The study was conducted in the Evrona Nature Reserve, a desert ecosystem in southern Israel where two major oil spills occurred in 1975 and in 2014. Leaf samples were collected to analyze the central metabolite profiles from oil-polluted and unpolluted adult trees and from Vachellia seedlings growing in oil-polluted and unpolluted soils in an outdoor setup. We found that oil pollution had a stronger effect on one-year-old seedlings than on adult trees, reducing the levels of amino acids, sugars, and organic acids. While adult trees are mildly affected by oil pollution, the effects on young seedlings can cause a long-term reduction in the population of these keystone desert trees, ultimately threatening this entire ecosystem.

Invertebrate and vertebrate predation rates in a hyperarid ecosystem following an oil spill

“…We find it more likely that higher water availability to the polluted trees due to their central location in the streambed, rather than direct effects of the oil pollution, accounted for this pattern. Although our hypothesis that oil pollution would reduce the activity both invertebrate and vertebrate predators was not confirmed, oil pollution is a major threat to this ecosystem: It was shown to change the soil microbial community (Girsowicz et al, 2018) and parasitoid abundance (Möller et al, 2020), as well as to reduce Vachellia seed germination (Tran et al, 2018), seedling recruitment (Nothers et al, 2017), and to modify the tree metabolism (Ferrante et al, 2021).…”

“…In this area, two large oil spills occurred in 1975 and 2014, during which around 10,000 m 3 and 5,000 m 3 of crude oil, respectively, leaked into the area jeopardizing the entire ecosystem (Golan et al, 2016). Oil pollution has been shown to affect the metabolism, recruitment, and germination of keystone tree species in this area (Ferrante et al, 2021;Golan et al, 2016;Nothers et al, 2017) and may negatively affect insect biodiversity (Möller et al, 2020) with potential cascading effects on biotic interactions. We focused our study on predation, a fundamental ecosystem function (Hairston et al, 1960).…”

Five-Year Monitoring of a Desert Burrow-Dwelling Spider Following an Environmental Disaster Indicates Long-Term Impacts

“…Acacia trees (several species of the genus Vachellia (Wight & Arn. )), the keystone species in this ecosystem, were found to be affected by oil spills [16,17]; germination, seedling height, leaf number, stem diameter, and root growth were significantly reduced in oil-contaminated soils than in clean soils [17]. Moreover, five different metabolites (alanine, β-alanine, acid, maltose, and phosphoric acid) had significantly different levels in the oil-contaminated and clean soils of Acacia trees [16].…”