Response and resilience of estuarine benthic ecosystems to anthropogenic pressures
type: CreativeWork
description: Human activities are altering coastal environments at local and global scales with largely unknown consequences. Catchment land-use changes increase the rates of delivery of fine sediments and nutrients to estuaries, resulting in increased suspended sediment concentrations (SSC) and eutrophication; this thesis investigates the response and resilience of soft-sediment intertidal ecosystems to these two anthropogenic stressors. Increased SSC elevates water-column turbidity and reduces the light available for benthic primary producers that sustain estuarine food webs. In intertidal habitats, this turbidity stressor is removed during low tide as the water-column uncovers the seafloor. In other words, turbidity is a temporally displaced stressor in intertidal environments. Photosynthesis during low tide periods of emergence may therefore provide resilience against elevated turbidity during periods of submergence. However, the role of low tide primary production (PP) in estuarine benthic foodwebs has largely been overlooked. Emerged and submerged benthic PP was measured in adjacent seagrass and microphytobenthos-dominated (sandflat) soft-sediment habitats at three locations along a turbidity gradient. Benthic chambers were used to measure the flux of CO₂ across emerged sediments, and dissolved O₂ across submerged sediments to derive net (NPP) and gross (GPP) PP. Emerged NPP and GPP were higher (2–16 times) than submerged in all instances (p < 0.01), and when standardised by mean incident photosynthetically active radiation, the difference between emerged and submerged seagrass PP increased with site turbidity (from 2 to 26 times greater). Emerged PP may be crucial for providing resilience against benthic productivity losses in turbid environments. Eutrophication results in the deposition of excess organic material to soft-sediments and stimulates microbial respiration; this consumes O₂, potentially leading to hypoxia, and releases CO₂, causing localised acidification. I e…
abstract: Human activities are altering coastal environments at local and global scales with largely unknown consequences. Catchment land-use changes increase the rates of delivery of fine sediments and nutrients to estuaries, resulting in increased suspended sediment concentrations (SSC) and eutrophication; this thesis investigates the response and resilience of soft-sediment intertidal ecosystems to these two anthropogenic stressors. Increased SSC elevates water-column turbidity and reduces the light available for benthic primary producers that sustain estuarine food webs. In intertidal habitats, this turbidity stressor is removed during low tide as the water-column uncovers the seafloor. In other words, turbidity is a temporally displaced stressor in intertidal environments. Photosynthesis during low tide periods of emergence may therefore provide resilience against elevated turbidity during periods of submergence. However, the role of low tide primary production (PP) in estuarine benthic foodwebs has largely been overlooked. Emerged and submerged benthic PP was measured in adjacent seagrass and microphytobenthos-dominated (sandflat) soft-sediment habitats at three locations along a turbidity gradient. Benthic chambers were used to measure the flux of CO₂ across emerged sediments, and dissolved O₂ across submerged sediments to derive net (NPP) and gross (GPP) PP. Emerged NPP and GPP were higher (2–16 times) than submerged in all instances (p < 0.01), and when standardised by mean incident photosynthetically active radiation, the difference between emerged and submerged seagrass PP increased with site turbidity (from 2 to 26 times greater). Emerged PP may be crucial for providing resilience against benthic productivity losses in turbid environments. Eutrophication results in the deposition of excess organic material to soft-sediments and stimulates microbial respiration; this consumes O₂, potentially leading to hypoxia, and releases CO₂, causing localised acidification. I e…
author: Drylie, Tarn Paige
keywords: ecosystem function, disturbance, biodiversity-ecosystem function, intertidal
license: https://researchcommons.waikato.ac.nz/bitstreams/3628096d-103e-4447-9015-79812e65c5f1/download
date published: 2020
date modified: 2026-07-24T05:57:24Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato