Abstract

Oil spills threaten the productivity of ecosystems through the degradation of coastal flora and the ecosystem services these plants provide. While lab and field investigations have quantified the response of numerous species of emergent vegetation to oil, the effects on submerged vegetation remain uncertain. Here, we discuss the implications of oil exposure for Ruppia maritima, one of the most common species of submerged vegetation found in the region affected by the recent Deepwater Horizon oil spill. We grew R. maritima in a range of manipulated sediment oil concentrations: 0, 0.26, 0.53, and 1.05 mL oil /L tank volume, and tracked changes in growth (wet weight and shoot density/length), reproductive activity (inflorescence and seed production), root characteristics (mass, length, diameter, and area), and uprooting force of plants. While no statistical differences were detected in growth, plants exhibited significant changes to reproductive output, root morphology, and uprooting force. We found significant reductions in inflorescences and fruiting bodies at higher oil concentrations. In addition, the roots growing in the high oil were shorter and wider. Plants in medium and high oil required less force to uproot. A second experiment was performed to separate the effects of root morphology and oiled sediment properties and indicated that there were also changes to sediment cohesion that contributed to a reduction in uprooting forces in medium and high oil. Given the importance of sexual reproduction for these plants, oil contamination may have substantial population-level effects. Moreover, areas containing buried oil may be more susceptible to high energy storm events due to the reduction in uprooting force of foundation species such as R. maritima.

Highlights

  • Coastal seagrasses and submerged aquatic vegetation are historically abundant throughout coastal regions worldwide [1,2,3]

  • Chemical analyses of a subset of tanks verified the presence of numerous compounds associated with oil contamination (S1 and S2 Figs). These concentrations are within the range of those found in field conditions after the Deepwater Horizon (DWH) oil spill [56,57]

  • Ruppia grew in all treatments, with little differences found in growth (Table 1)

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Summary

Introduction

Coastal seagrasses and submerged aquatic vegetation are historically abundant throughout coastal regions worldwide [1,2,3]. The estuaries of the northern Gulf of Mexico (GoM) are relatively productive areas [9,10] because of a diverse mix of submerged and emergent vegetation. These structured habitats provide refuge for the young of many commercially and recreationally important nekton species [11,12,13], contribute to the forage base of consumers [14,15], buffer coastlines from high energy events [16,17,18], and improve water quality and clarity to potentially mitigate some of the negative effects of eutrophication [19,20,21]

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