A biophysical representation of seagrass growth for application in a complex shallow-water biogeochemical model

Baird, Mark E., Adams, Matthew P., Babcock, Russell C., Oubelkheir, Kadija, Mongin, Mathieu, Wild-Allen, Karen A., Skerratt, Jennifer, Robson, Barbara J., Petrou, Katherina, Ralph, Peter J., O’Brien, Katherine R., Carter, Alex B., Jarvis, Jessie C., and Rasheed, Michael A. (2016) A biophysical representation of seagrass growth for application in a complex shallow-water biogeochemical model. Ecological Modelling, 325. pp. 13-27.

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Abstract

Seagrasses are a critical component of the healthy functioning of many coastal marine ecosystems. Capturing the dynamics of seagrass communities requires both a detailed representation of processes such as seagrass nutrient uptake and photosynthesis, as well as models of light penetration, water column and sediment biogeochemical processes and other ecosystem characteristics that determine the environmental state. Here we develop a new two-state, 13-parameter seagrass model with the aim of providing sufficient detail to represent light and nutrient limitation, but simple enough to be coupled into a 60 state variable biogeochemical model. The novel formulation is built around a nitrogen-specific leaf area parameter, Ω, that is well-constrained and is used in calculating both the rate of photosynthesis and the fraction of the seafloor covered by seagrass, Aeff, where Aeff = 1 − exp(− ΩSGA) and SGA is the aboveground areal seagrass biomass. The model also contains terms for the uptake of nutrients from multiple layers of varying-porosity sediments, translocation of organic matter between leaves and roots, respiration and simple mortality terms. The model is applied to Gladstone Harbour, a macro-tidal sub-tropical estuary in northeast Australia, and is able to simulate realistic spatial seagrass distributions. A simplified form of the model is derived, which can be used to predict seagrass light-limited growth based on five measurable species-specific parameters (maximum growth rate, mortality rate, compensation irradiance, leaf blade angle and nitrogen-specific leaf area). The steady-state percent coverage of seagrass achieved at varying light levels and mortality intensity is calculated as a means of understanding the dynamics of the new seagrass model.

Item ID: 43205
Item Type: Article (Research - C1)
ISSN: 1872-7026
Keywords: Gladstone Harbour; leaf area; Zostera; Halophila; photosynthesis; seagrass
Date Deposited: 26 Apr 2016 02:58
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050206 Environmental Monitoring @ 30%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050211 Wildlife and Habitat Management @ 30%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 40%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960503 Ecosystem Assessment and Management of Coastal and Estuarine Environments @ 50%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960507 Ecosystem Assessment and Management of Marine Environments @ 50%
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