Quantifying annual cycles of macronutrient fluxes and net effect of transformations in an estuary: their responses to stochastic storm-driven events

Lead Research Organisation: University of Southampton
Department Name: School of Ocean and Earth Science

Abstract

Estuaries are more than simply areas of mud and marsh that represent the transition zone between rivers and the ocean. They play a vital role in our economy as sites of leisure and commercial activities, such as fishing and boating. In addition, they are important nursery grounds for many species of economically important fish that later migrate to the open sea. As approximately 40% of the world's population live within 100 km of the coast, estuaries are also some of the most vulnerable sites for impact from man's activities. Not only can they suffer from activities occurring within the estuary itself, but they also mark the point where pollutants gathered by rivers from large areas of the interior can accumulate.
One of the major pollution concerns in estuaries arises from the excess river borne concentrations of phosphate and nitrate. These can be derived from a variety of sources, such as run off from fertilised fields and discharge (accidental or purposeful) from sewage treatment plants. Regardless of their source, they can cause severe problems, such as stimulating the growth of excess algal growth that can deplete the water in oxygen and causing widespread fish kills, or causing the growth of poisonous algal species (red tides) that cause shell fish fisheries to be closed. Although this problem has been recognised for some time, and monitoring activities by bodies such as the Environment Agency and water companies play an important role in keeping pollution in check, there are still major gaps in our knowledge. In particular, it is apparent that a large proportion of the flux of nitrate and phosphate are delivered to estuaries by sudden storm events, but most monitoring takes place at fixed times that are spaced too far apart to capture these events. This is a major gap in our knowledge that will become more important as the intensity and frequency of storms are likely to increase due to climate change. Additionally, the phosphate and nitrate load of rivers can take many forms - dissolved and particulate, organic and inorganic - and relatively little is known about the concentrations of these different forms varies throughout the seasons and during storm events. Only if we are able to fully understand these processes will we be able to take the necessary steps to identify and control polluting sources of nitrate and phosphate to estuaries.
Our research seeks to address this gap in our knowledge by carrying out detailed monitoring of the many forms of phosphate and nitrate that enter Christchurch Harbour estuary (Dorset) from both the rivers and the sea over the course of a year. We will be using state-of-the-art technology (much of it developed by ourselves) that will allow us to monitor they key parameters at intervals of every 30 minutes. Hence, we will be able to capture the effects of sudden and short-lived storms that have eluded previous studies and routine monitoring practices. We will then use the results of our study to examine how these sudden storm events affect the distribution of phosphate and nitrate within the estuary. In particular, we will examine what happens when sediments are stirred up in the estuary by storms - do they remove or add phosphate and nitrate to the system? We will also examine the effects of these sudden storms on the biological activity in the estuary. Again, do they increase or decrease the growth of algae, and what difference is there if the storm happens in the summer or the winter?
The various threads of our study will be drawn together into a powerful statistical model that will allow us to better understand the transfer of phosphate and nitrate from rivers, through estuaries and into the coastal seas, and the role that storms play in this process. Our results will then allow policy makers to make more informed decisions about how we can seek to reduce pollution of estuaries by nitrate and phosphate.

Planned Impact

The potential users of this work will include all the UK agencies that are involved in the regulation of the marine, estuarine and freshwater environments within the UK. These include the main stakeholders (Department for Environment, Food and Rural Affairs (Defra) and the Environment Agency (EA)) already outlined in the Macronutrient Cycles Programme Stakeholder Policy and Research Interest Document. Other agencies that are potential users include Natural England (NE) and The Joint Nature Conservation Committee (JNCC). Along with the major agencies there are a number of other groups within the Christchurch Harbour Catchment that are potential users. One of these is the Christchurch Harbour Steering Group (CHSG), which consists of a number of interested end-users and stakeholders including - Bournemouth Borough Council, Sembcorp Bournemouth Water, Christchurch Borough Council, Christchurch Community Partnership (a network of statutory, business and voluntary organisations), Christchurch Harbour Association (itself made up of 27 user groups including boatyards, sailing and rowing clubs, hiring and mooring concerns, residential marinas and the Fisherman's Association), Dorset Coast Forum, Dorset Police, Environment Agency and Natural England (NE). Other users that could potentially benefit from this research include NGO's interested in the effective management of estuarine and harbour environments that could be susceptible to eutrophication and harmful algal blooms, such as The Royal Society for the Protection of Birds (RSPB), the Wildfowl & Wetlands Trust (WWT) and the Dorset Wildlife Trust. Other potential users include school children for education about environmental science and impacts and also local interest groups such as the National Trust.
The Government's vision is for clean, healthy, safe, productive and biologically diverse coastal seas (including harbours and estuaries). This is the basis for managing sustainable human use and exploitation of the goods and services provided by the seas. The challenge for science is to provide an understanding of the state and function of the marine environment and thus put future forcing such as climate change or changes in human activities into context. The work outlined in this project will aim to provide an impact both economically and societally by building on the existing lines of knowledge exchange and public engagement already established by the NERC Macronutrients Programme (MNP). Through dialogue with the CHSG there is a clear link for dissemination of the findings to end-users and stakeholders. The results generated by this project are complex and potentially wide ranging, it is envisaged that by engaging with Defra and the EA through the MNP that they will advance understanding relevant to specific Defra and UK agency research themes.
Other beneficiaries who may have an interest in the outcomes of this work include the commercial private sector as there is a clear economic potential embedded within the project. The commercial potential of the Lab On a Chip technology (LOC) has been described previously in reports prepared by two consultants funded by a NERC Pathfinder award. This evaluation has been extended by ongoing discussions with industry partners, and NOC and UoS Technology Transfer Office's (TTOs). The technology directly addresses a market estimated at >£11-33 m, with significant growth potential. This product could contribute to the competitiveness of the UK economy in the short term. The pathfinder studies identified that demonstration to users was a critical step in gaining the confidence of users and potential commercialisation partners. The programme will enable this demonstration of LOC technology by directly engaging with key partners and user groups (such as the EA and Defra). We will engage with the stakeholders and also meet with commercialisation partners (YSI, Chelsea Technologies Group, Teledyne and others) to progress commercialisation.
 
Description Macro-nutrient fluxes of nitrate and phosphate under high river flow conditions are underestimated if sampling frequency is less than once per week.
Autonomous insitu monitoring of water quality of rivers and estuaries is possible over extended periods using autonomous samplers and water quality sondes with minimal maintenance of the equipment. Dissolved organic carbon inputs to Christchurch Harbour estuary from both the
Hampshire Avon and Dorset Stour rivers positively correlate with river flow where as dissolved organic nitrogen shows no clear relation to river flow.
Exploitation Route Water authorities and Environment Agency are interested in our results
Sectors Environment,Other

URL http://www.christchurch-macronutrients.org.uk/
 
Description Results of study have been included on several water industry web pages. eg http://www.environmentuk.net/technology/technology-news/autos/3379-estuary-research-project-highlights-advantages-of-continuous-monitoring. http://www.allaboutshipping.co.uk/2015/10/07/estuary-research-project-highlights-advantages-of-continuous-monitoring/ https://www.ysi.com/File%20Library/Documents/Application%20Notes/Christchurch-Harbour-Macronutrient-Cycles-Programme.pdf Data resulting from the research has been submitted to BODC in December 2016 (Lap on Chip Nitrate data) April 2018 (all Christchurch Harbour estuarine and river data from Macronutrient project) and results from the grant presented at final NERC Macronutrients programme meeting at Royal Society in June 2016.
First Year Of Impact 2016
Sector Environment,Other
Impact Types Policy & public services

 
Description Application of water quality and nutrient sensors for assessment of nutrient fluxes from rivers to estuaries.
Amount £10,000 (GBP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 04/2014 
End 11/2014
 
Description High Frequency Autonomous Nutrient and Water Quality Monitoring in a River-Estuary System
Amount £9,000 (GBP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2013 
End 06/2014
 
Description NERC capital opportunity (CNHS analyser)
Amount £25,000 (GBP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 04/2013 
End 03/2014
 
Title A Bayesian model approach to estimate effect of storm events on macronutrient fluxes in the Hampsghire Avon. 
Description Model developed by Dr Monica Pirani and Prof Sujit Sahu 
Type Of Material Computer model/algorithm 
Year Produced 2016 
Provided To Others? Yes  
Impact Publication M. Pirani, A. Panton, D.A. Purdie, S.K. Sahu. (2016) Modelling macronutrient dynamics in the Hampshire Avon river: A Bayesian approach to estimate seasonal variability and total flux. Science of the total Environment 572, 1449-1460 
 
Title Christchurch Harbour Macronutrients Project weekly spot sampling 2013 - 2014 and boat transects 2014. 
Description As part of the NERC-funded Christchurch Harbour Macronutrients Project scientists from the University of Southampton and the University of Portsmouth sampled two rivers on the south coast of England (U.K.) and their joint estuary on a weekly basis between April 2013 and April 2014. The river sites used were the lowest Environment Agency gauging stations on the Hampshire Avon (Knapp Mill) and the River Stour (Throop), and samples were also taken from the outflow of Christchurch Harbour at low tide on the same dates. A fourth site, Iford Bridge on the River Stour, was added to the project in August 2013. In addition to this, a series of boat transects sampling at 6 stations along the salinity gradient in Christchurch Harbour were undertaken in the summer of 2014 at fortnightly intervals. Samples were analysed for dissolved inorganic and organic nutrients and a multi-sensor sonde was used to measure vertical profiles of temperature, conductivity, salinity, pH, dissolved oxygen concentration, and chlorophyll a concentration at each station 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact New data set on this river/estuary system 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/6aab5ff3-1c0f-1105-e053-6c86abc...
 
Title Nitrate and nitrite data from a National Oceanography Centre lab-on-chip analyser at Knapp Mill 
Description High resolution measurements of nutrients in rivers can provide unprecedented information about sources, fluxes and in-stream processing. NOC has developed a submersible lab-on-chip (LOC) nitrate analyser that can be operated without mains power for extended periods (e.g. three months of hourly measurements without intervention). As part of the Christchurch Harbour Macronutrients Project (NERC Macronutrient Cycles Programme), the LOC nitrate analyser was deployed at Knapp Mill, an Environment Agency gauging station on the Hampshire Avon, between 15th October 2014 and 15th October 2015. It collected hourly nitrate data (subject to some short gaps) for the entire year. The reagents an onboard 300 uM standard were replaced every three months on-site. Deployed alongside were a YSI EXO sonde (full year) and an ISCO water sampler (until 19th December 2014). Spot samples were also collected throughout the year. This is the first high-resolution (hourly) nitrate dataset from Knapp Mill, and also the first river dataset from a miniaturised LOC sensor. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
Impact New data using lab on chip nitrate sensor 
URL https://www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/47f09d73-b5aa-0c3b-e053-6c86abc...
 
Description Christchurch Harbour Macronutrient Project Website 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A project website is now live http://www.christchurch-macronutrients.org.uk/

Interest stimulated widely on the project
Year(s) Of Engagement Activity 2013