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The effects of wading birds on the erosion, properties and ecosystem services of estuarine intertidal muddy sediments

My name is James, and I am studying part time for a PhD in the School of Environmental Sciences at the UEA. My research topic is “Biosedimentological Cascades: the effects of wading birds on the erosion, properties and ecosystem services of estuarine intertidal muddy sediments”. Wading birds are key to the functioning of estuaries, mediating processes that help deliver ecosystem services that humans rely on. I am investigating this by excluding wading birds from 2m x 2m sections of mudflat in the Colne estuary Fingringhoe Wick Nature Reserve in Essex, so I can compare areas of mudflats where birds feed with areas where they are prevented from feeding. This will enable me to quantify the contribution of wading birds to the delivery of services, by measuring key sediment properties such as erodibility and microalgal biofilm abundance, which underpin ecosystem service delivery (a biofilm is a layer of millions of microscopic organisms covering the surface of the sediment, acting a bit like skin).

I’ve tested two different methods of excluding wading birds from areas of a mudflat, adapted from previously used designs. The idea of species exclusion is not new in ecological studies, but testing the methods is vital to ensure that the exclosures can withstand the harsh and unpredictable conditions of the intertidal environment. Both exclosures withstood the elements for three months, which was a huge relief. One also successfully excluded all wading birds from areas of the mud which gives me hope that a larger scale deployment within a well-designed experiment will produce the data needed to test the effects waders have on their habitat.

I took some preliminary measurements during this testing, learning how to use the equipment whilst sinking knee deep in the mud! Insufficient measurements were taken to perform a detailed statistical analysis, but it appears that changes to the sediment properties occurred more quickly than I was expecting. Algal blooms appeared rapidly among exclusion plots, but by the time I had managed to organise sampling the site, an army of mudsnails had arrived in my study area and eaten much of the biofilm. Measurements taken later suggested that temporal differences between plots were great enough to mask any differences caused by bird presence/absence. These findings raise questions about the interaction of different species on mudflats, which I hope to shed more light on as my research progresses. I’ve not yet managed to find any other published research which has investigated the link between wading bird presence/predation to changes in sediment characteristics. I would be very interested to know whether anybody else has, do get in touch at my e-mail below if you know of any such research.

This work was undertaken at Fingringhoe Wick Nature Reserve in collaboration with Essex Wildlife Trust and with permission from Natural England. Many thanks to Louise Beary and Matt Cole at the reserve for their cooperation and advice.

James Booty, EnvEast PhD student

Project supervisors: Drs Trevor Tolhurst and Richard Davies (UEA), and Prof. Graham Underwood (University of Essex).

Posted by Lisa Johnson on Thu, 15 Sep 2016

Lisa Johnson

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