National Marine Baseline Survey 1995 Littoral Cell 10 Bardsey
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E^-nACEIsS' Box A f National Marine Baseline Survey 1995 Littoral Cell 10 Bardsey Sound to Great Orme En v ir o n m en t A g e n c y Report NC/MARy016 Part 12 of 17 National Centre for Environmental Monitoring and Surveillance Rivers House Lower Bristol Road Tv^rton Or Alison Matthews, Oceanographer BA2 9ES Alastair Duncan, Data Officer Fo reword In recent years we have carried out National Baseline Surveys of (he coastal zone which have involved analysis of samples taken at specific locations in coastal waters around England and Wales for a wide range of determinants. These data have been supplemented by further continuous analysis from the Coastal Survey Vessels and by spatial data from airborne remote sensing operations. The dissemination of information from these data in an easily digestible form has proved to be a difficult task. To try to overcome (his problem the data for the 1995 surveys have been distilled into a summary for each littoral cell. The information in these summaries is meant to reflect the main features of the littoral cell. More extensive data as well as data collected in previous surveys are held at the National Centre and can be made available on request. DAVID PALMER MANAGER, NATIONAL CENTRE ENVIRONMENT■ Hill AGENCY 135426 I Introduction I'hc objccl of this report is to present an overview of the results of the four 1995 surveys in a compact form. The report is accpmpanied by the full laboratory analysis results and a catalogue of image data stored on CD -K O M and video. In total there are seventeen parts to the report, and those parts included in this pack arc listed at (lie cud of this section. The coastline has been divided inlo coastal cells, known as littoral cells using the procedure developed by I IR Wallingford (Molyka and ({tampion, Report SR 32X, January 199.1). A map of (lie divisions b e tw e e n these cells is shown in Figure (i). The rationale of these cells means that any changes within a cell should not affect adjacent cells. In addition each cell has a significantly different character to adjacent cells, in term s o f geology or biology. The divisions were defined principally for coastal defence construction, but the position of boundaries have implications on water quality variations, For example, effects from effluent outfalls should not be transferred across boundaries. The water chemistry results for cach ccll have been reviewed for cach season. In particular the nutrient results have been investigated for high concentrations in Summer which may be linked to anthropogenic sourccs, and which may result in eutrophic waters. In parallel with this the chlorophyll-^ concentrations have been studied for any increases which arc linked to high nutrient values, by two techniques. Firstly, the individual samples have been investigated, and secondly, maps of the entire coastal zone have been produced to allow spatial estimates of eutrophic waters to be made. The absolute concentration of chlorophyll-^ is compared with a concentration of 10 pg/1. This is the level suggested as representative of a bloom event by the Department of the Environment in their document "Criteria and Procedures for Identifying Sensitive Areas and Less Sensitive Areas" which was produced as a response to the EC Urban Waste Water Treatment Directive. Although this level signifies the presence of a phytoplankton bloom, it must be associated with other indicators to show that waters are effected by eutrophication. D issolved metals concentrations have been investigated in terms o f their relation to the Environmental Quality Standard (EQS) levels. These levels are established in response to the EC Dangerous Substances Directive. The definition of the EQS level is as an annual mean. This has been calculated for any sites in which an individual sample exceeds the EQS. Organic contaminants have also been compared with EQS levels where they exist. Consideration has been given to the position o f the baseline sampling sites in relation to estuaries or major oceanographic features. The image data and underway data have been investigated for major oceanographic features and changes in water quality. These may be manifested in the image data in two ways. Features are seen in the CASI imagery if they result in an alteration in the ocean colour signal. This usually requires a change in the amount of light scattered or absorbed by particles in the water column. Features such as estuarine plumes have higher particulate matter loading which increases the ocean colour sighal. Phytoplankton blooms increase the absorption of light in selected wavebands and moreover result in fluorescence being detected in other wavebands. Some features do not record a CASI signal but have a difference in water temperature. The thermal video systems used in the baseline survey record only the surface temperature o f the water, but clearly show features such as effluent discharges and outfalls from power station cooling systems, in addition to river plumes. The underway data illustrates changes in temperature, salinity, dissolved oxygen, transmission and fluorescence. The longitudinal profiles from the underway systems have been investigated for major changes which may be associated with estuarine inputs or fronts between different water bodies. Data from the Skalar continuous monitoring nutrient analyser have been investigated to determine the geographical extent of elevated samples in the laboratory analyses. Sum m aries have been produced for cach littoral ccll which provide a statement on the water quality of the region recorded by the baseline survey. The key local oceanographic features arc also summarised. I 1. Wales, After Motyka and Brampton; 1993. Motyka, J.M. and Brampton. A.H. (1993). "Coastal Management, Mapping of Littoral Cells", HR Wallingford. i Littoral Cell 10: Bardsey Sound to Great Orme Executive Summary This littoral cell extends from Bardsey Island to Great Orme, and includes the coastline of the Isle of Anglesey and the Menai Strait. No dissolved metals concentrations were in excess of Environmental Quality Standards, and no organic determinands were detected at concentrations above the minimum reporting value of 0.001 |ig/I. Chlorophyll-a concentrations showed a seasonal cycle with highest concentrations in Spring. Elevated concentrations were seen at Great Orme in Summer, with corresponding high nutrient levels, but these were not above 10 (j.g/1. Spatial Chlorophyll-a results, both from the aircraft and the underway fluorimeter showed no areas within this littoral cell with Chlorophyll-a concentrations in excess of 10 jj.g/1. Thus these waters were not subject to eutrophication at the time of the Summer survey. The major oceanographic processes evident in this region were associated with sediment movement. Although concentrations were low, variability is high and as such is evident in the CASI imagery. Thermal video imagery revealed the extent of the outfall of cooler water from Wylfa power station, and also marked the presence of a coastal front across Malltraeth Bay, which may have implications on water quality within the bay. 1. Introduction This littoral cell extends from Bardsey Island, off the Lleyn Peninsula in the south to Great Orme off the coast of North Wales at Llandudno, and includes the coastline of the Isle of Anglesey (see Figure 1). This represents approximately 1200 km2 of water within the coastal zone for which the Environment Agency has responsibility for controlled waters, of which 105 km2 are estuarine waters. Four vessel surveys for the collection of water samples for laboratory analysis and continuous data were carried out by Coastal Guardian and Vigilance. These took place in early Spring (March), late Spring (early June), Summer (July) and Autumn (September). The vessel track passes around the north of Anglesey and does not include the Menai Strait. Two aircraft campaigns were undertaken in July and September/October. These covered the entire coastline, including inside the Menai Strait. 2. Water chemistry results 2.1 Background There are ten baseline sampling points in this littoral cell, with in two cases extra sampling points added adjacent to the baseline sites for sampling in differing tidal conditions. The positions are marked in Figure 1. 2.2 Nutrients and chlorophvll-q 2.2.1 Total Oxidised Nitrogen (TON) Total oxidised nitrogen (TON) concentrations recorded a maximum of 145 (ig/1 N in early Spring at Holyhead (162), with lower concentrations in Spring and Summer, typically less than 50 jj.g/1 N. Red\Wharf Bay (164) recorded a concentration of 586.6 pg/l N in Summer. Geographically, the maximum concentration for this cell is found at the Holyhead (162) sampling station in early and late Spring and Autumn, with elevated ^concentrations relative to neighbouring sites found here in Summer. 2.2.2 Silicate Silicate concentrations are low in comparison to national figures for each survey, but concentrations are highest during the early Spring and Autumn surveys. The maximum concentration was 189 jj.g/1 Si at Dylan (159). Concentrations of silicate follow no clear geographical pattern, although elevated concentrations are seen at Holyhead (162) and Red Wharf (164) Bay in each survey. 2.2.3 Orthophosphate Orthophosphate concentrations were consistently highest in the early Spring survey, with a maximum concentration of 22.2 jLLg/1 P at Red Wharf (164). Late Spring concentrations were generally lower, but with a maximum of 33.9 (ag/1 P at Holyhead (162). In Summer most sites recorded concentrations less than 10 p.g/1 P, with concentrations rising once more in Autumn, to a maximum of 27.1 jj.g/1 P at Red Wharf (164). 2.2.4 Total A mmoniacal Nitrogen (A mmonia) Ammonia concentrations were highest in Summer, with maxima at Great Orme (165) equal to 90 p.g/1 N and Lynas Point (163.1) equal to 86 (j.g/1 N.