Modelling the distribution and growth of ‘problem’ green seaweed in the Medway estuary,UK |
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Authors: | J N Aldridge M Trimmer |
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Institution: | (1) Cefas, Pakefield Rd., Lowestoft, Suffolk, NR33 0HT, UK;(2) School of Biological Sciences, Queen Mary University of London, London, E1 4NS, UK |
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Abstract: | The results of a modelling study to investigate the mechanisms controlling macroalgal growth within the Medway estuary, UK,
are presented. Intertidal zone bathymetry, tidal dynamics and turbidity control the time available for nutrient uptake and
photosynthesis, and were used as a basis for predicting areas where macroalgae will grow. Tidal bed stress was also considered
as a controlling factor for the presence of the less robust green macroalgae species. Two approaches to predicting macroalgal
distributions were applied: (1) a simple ‘suitability index’ method based on tidal flooding and drying, taking account of
the conflict between time available for nutrient uptake and for photosynthesis; and (2) a biological macroalgal growth model
that includes a detailed treatment of nutrient uptake and plant growth. The former approach assigns a value between zero and
one for the suitability of a location for macroalgal occurrence, while the latter predicts the full macroalgal growth dynamics
over an annual cycle. Tidal bed stress was included in both approaches as an independent modifier of macroalgal occurrence/growth.
Results were compared with aerial survey maps of observed vegetation cover and time series of measured biomass density. Both
approaches gave good predictions of non-species-specific vegetation cover in the intertidal zone of the Medway. Tidal bed
stress was found to be a strong predictor of the specific occurrence of Enteromorpha spp. and Ulva spp., with these species favouring areas of low tidal energy. It was concluded that light and a lack of suitable regions
with low tidal bed stress, rather than nutrients, were the main factors limiting excessive growth of Enteromorpha spp. and Ulva spp. in the estuary. Although this study was focussed on the Medway, the results are likely to be applicable to a broad range
of relatively turbid, meso- and macro-tidal estuaries.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Guest editors: J. H. Andersen & D. J. Conley
Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of
Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark |
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Keywords: | Macroalgae Models Medway estuary Nutrients Light Bed stress |
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