Short-term response of aquatic ecosystem metabolism to turbidity disturbance in experimental estuarine wetlands

Abstract

The ecological response to suspended-sediment-induced turbidity is an important consideration for large engineering projects and ecological conservation in estuarine wetlands. However, few studies have quantified the effects of increasing suspended sediment on ecosystem functioning. To explore the effects of short-term turbidity variations on the aquatic metabolism of a wetland ecosystem, we conducted a controlled experiment based on the turbidity characteristics in the Yellow River estuarine wetland. Four turbidity disturbance levels (10, 50, 150, and 250 Nephelometric Turbidity Units (NTUs)) were applied to artificially cultivated wetlands and the subsequent variations and potential causes thereof were analyzed. The results showed that increases in turbidity significantly reduced the gross primary production (GPP) and ecosystem respiration (ER) rates within a single day. The GPP declined more than the ER, leading to lower net ecosystem production and a more heterotrophic water column. Increased turbidity limited photosynthetic oxygen production and thus limited the GPP rate. Even a slight increase in turbidity (for example, from 10 to 50 NTU) had rapid negative effects on the GPP and ER rates, while lower solar radiation and temperature decreased the GPP and ER much further. The results of this study imply that increased exposure to suspended-sediment-induced turbidity may severely impair aquatic metabolism in wetland ecosystems with submerged plants.