Effects of Fine Sediment on Seagrass Meadows: A Case Study of <i>Zostera muelleri</i> in Pāuatahanui Inlet, New Zealand

Abstract

Seagrass meadows are vulnerable to fine sediment (mud) pollution, with impacts usually attributed to reduction in submerged light. Here we tested two non-exclusive hypotheses, that mud particles (−3), porewater ammonium concentration (65 µM), and a more reduced redox profile (negative redox at only 2 cm soil depth) as well as a lower light availability when submerged compared to other habitats, while total daily light exposure differed little between habitats. This suggests that failure of seagrass to recolonize historical seagrass habitat reflects substrate muddiness and consequent unfavorable rhizosphere conditions. Our results provide evidence for the multi-stressor effects of fine sediment on seagrasses, with substrate suitability for seagrass being detrimentally affected even where light exposure seems sufficient.

Keywords

• sedimentation
• pollution
• fine sediment
• mud
• photosynthetically available radiation (PAR)
• rhizosphere