Effects of heavy metal pollution on germination and early seedling growth in native and invasive Spartina cordgrasses

Authors: INFANTE-IZQUIERDO, MARIA - Universidad De Huelva; POLO-AVILA, ALJANDRO - Universidad De Huelva; SANJOSE, ISRAEL - Universidad De Huelva; CASTILLO, JESUS - Universidad De Huelva; NIEVA, F. JAVIER - Universidad De Huelva; Grewell, Brenda; MUNOZ-RODRIGUEZ, ADOLFO - Universidad De Huelva

Submitted to: Marine Pollution Bulletin
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2020
Publication Date: 6/17/2020
Citation: Infante-Izquierdo, M.D., Polo-Avila, A., Sanjose, I., Castillo, J.M., Nieva, F.J., Grewell, B.J., Munoz-Rodriguez, A.F. 2020. Effects of heavy metal pollution on germination and early seedling growth in native and invasive Spartina cordgrasses. Marine Pollution Bulletin. 158:111376. https://doi.org/10.1016/j.marpolbul.2020.111376.
DOI: https://doi.org/10.1016/j.marpolbul.2020.111376

Interpretive Summary: Globally, many estuarine wetlands have been degraded by pollution from urban, industrial and mining runoff that has led to concentrations of heavy metals in salt marsh sediments. Seed germination and seedling establishment are the stages most likely to be sensitive to abiotic stresses in the plant life cycle. We analyzed the effects of copper, zinc and nickel on seed germination and early seedling growth of native Spartina maritima and invasive S. densiflora from polluted and non-polluted estuaries. Germination percentages for either species were not affected by any metal at any tested concentration (up to 2000 µM). However, the increase in metal concentration had negative effects on invasive S. densiflora seedlings. Metal tolerance of the early seedling life stage of the Spartina species was spatially variable across estuaries in the Southwest Iberian Peninsula. The primary effect was on radicle development, representing initial seedling emergence. S. densiflora seedlings emerging from seeds from Tinto Estuary, characterized by high bioavailable metal loads, had a higher tolerance to metals than those from less polluted Odiel and Piedras Estuaries. Centuries of invasion history at Tinto wetlands, suggest both environment and evolutionary processes have played a role in the heavy metal tolerance observed today. These results have broad implications, since cordgrasses are widely distributed in estuaries with varying degrees of metal contamination in sediments. In an applied context, management efforts for control of invasive Spartina densiflora should prioritize eradication of this invader in marshes with lower heavy metal concentrations where growth is not limited by metal pollution.

Technical Abstract: Globally, many estuarine wetlands have been degraded by pollution from urban, industrial and mining runoff that has led to concentrations of heavy metals in salt marsh sediments. Seed germination and seedling establishment are the stages most likely to be sensitive to abiotic stresses in the plant life cycle. We analyzed the effects of copper, zinc and nickel on seed germination and early seedling growth of native Spartina maritima and invasive S. densiflora from polluted and non-polluted estuaries. Germination percentages for either species were not affected by any metal at any tested concentration (up to 2000 µM). However, the increase in metal concentration had negative effects on invasive S. densiflora seedlings. Metal tolerance of the early seedling life stage of the Spartina species was spatially variable across estuaries in the Southwest Iberian Peninsula. The primary effect was on radicle development, representing initial seedling emergence. S. densiflora seedlings emerging from seeds from Tinto Estuary, characterized by high bioavailable metal loads, had a higher tolerance to metals than those from less polluted Odiel and Piedras Estuaries. Centuries of invasion history at Tinto wetlands, suggest both environment and evolutionary processes have played a role in the heavy metal tolerance observed today.