Monitoring of the BNNC Sands and Mud Flats – With respect to the size and location of the Zostera spp. beds, the Enteromorpha spp. mats, the Mussel beds and the seaward boundary of the Spartina sp zone. Aquatic Environments 01/03 Monitoring of BNNC Sands and Mud Flats Contents Contents ......................................................................................................................... 2 1. Introduction and Aims. .............................................................................................. 1 2. Survey methodology .................................................................................................. 1 3. Results for Lindisfarne. .............................................................................................. 2 4. Results for Budle Bay. .............................................................................................. 4 5. Discussion ................................................................................................................ 12 6. Bibliography ........................................................................................................... 13 Appendix 1. .................................................................................................................. 14 A. Lindisfarne Bay. .................................................................................................. 14 B. Budle Bay. ........................................................................................................... 48 2 Aquatic Environments 02/03 1. Introduction and Aims. Previous work on the intertidal sediment biotopes and life-forms of Lindisfarne and Budle Bay have been carried out by the Joint Nature Conservation Committee’s Marine Nature Conservation Review teams (Connor, 1989; Holt, 1994; and Brazier et al 1998) and specific monitoring of the Enteromorpha spp. mats on both Fenham Flats and Budle Bay has also been undertaken by the Environment Agency on an annual basis since 1995 (Peaty, 1996, 1998, 2002, Swaile, 2000). The largest Zostera noltii bed on the east coast of England is located in the southwest corner of Lindisfarne Bay on Fenham Flats and there is concern that the seasonal over-growth by Enteromorpha spp. may cause a decline in this species. The Zostera spp. is an important food source for passage and over-wintering wildfowl and the over- wintering flock of Light-bellied Brent Geese in particular. This study of 5 specific life-forms provides a follow up to a survey carried out by the Institute of Estuarine and Coastal Studies in 1999 (Allen et al., 1999). This previous survey analysed and mapped both the sediment infaunal communities and the epi- faunal and floral communities of Lindisfarne and Budle Bay, assigning biotope codings to the identified features, in line with the Marine biotope classification for Britain and Ireland (Connor (Ed.), 1997). This 2002 Aquatic Environments survey aimed to map to an accuracy of +/- 5m the position and extent of the gross life-form features listed below. Zostera spp. beds Enteromorpha spp. mats Mytilus edulis (mussel) beds The position of the seaward boundary of the Spartina anglica zone. The results of the Aquatic Environments survey are presented in this report as life- form maps overlaid on the Ordnance Survey ‘landline’ tiles for the area, the latter supplied by English Nature and reproduced here under their licence No. …... 2. Survey methodology A3 field base-maps for Lindisfarne and Budle Bay were prepared prior to the survey. These were laminated and carried in the field with waterproof pens, so that geo- referenced notes and information could be recorded on maps in situ during the survey should it be required. Two surveyors working in the field as a pair, carried out the mapping of the group of life-forms noted above, each surveyor carried a Garmin etrex GPS receiver, a base- map and recording forms. The life-form was identified when encountered on the sand/mudflats and the boundary was then walked, whilst the surveyor took photographs, made contemporaneous notes and entered waypoints in the GPS, as Monitoring of BNNC Sands and Mud Flats features of interest were encountered. Life-form beds were recorded where the percentage cover was deemed to be greater than 5% of the relevant species. The surveyors generally walked opposite boundaries of each life-form bed, in order to cover the ground quickly and efficiently. Safety was maintained during this exercise, as each carried a mobile phone and a regular call-in procedure was followed where beds were so wide that audio or visual contact was not clear. The Garmin etrex GPS stores the entered waypoints in a pre-determined format (Grid References or Latitude and Longitude) and also stores the track walked in a similar format. Both these data sets can be downloaded from the GPS receivers and uploaded into the mapinfo GIS programme. This allowed the boundaries of the life-forms to be immediately viewed in relation to the Landline map data and subsequently digitised as polygons, producing accurate maps of the life-form bed locations. The photographs taken during the survey were geo-referenced with a recorded waypoint and the description, along with the contemporaneous notes were entered into Mapinfo Browser tables. The resulting maps and photographs have been printed out and are presented in the results section of this report and a CD that includes the Mapinfo tables has also been produced as an output. 3. Results for Lindisfarne. Maps 1-3. present the life-form bed locations, their boundaries, photograph locations and target note waypoint positions in Lindisfarne Bay. The main features of interest and the limitations of the data are described below and photographs taken during the survey are presented in appendix 1. 3.1 Zostera noltii: Z. noltii is only found in relatively pure stands on the sandier / firmer areas of Lindisfarne Bay, these being on west Holy Island Sands and east Fenham Flats inside the Old Law promontory. The vast majority of the Zostera noltii is present as a large bed lying along the western side of the bay, occupying an area that runs out from the bottom of the Spartina anglica zone across the mudflats west to east for 800-1000m and north to south from ‘The Cages’ to ‘Cathangings Letch’, a distance of some 5 kilometres. This bed is generally overgrown by Enteromorpha spp., to varying degrees and the two genera together form a blanket almost completely covering the sediment. The exception to this is the uppershore edge of this bed, from the Spartina anglica out for 50- 80m eastwards, where the Zostera noltii is commonly present as a low density, but pure stand before the Enteromorpha spp. appears lower down the shore. Another mixed bed of Zostera spp. and Enteromorpha spp. lies at the north side of the bay on the eastern side of Holy Island Sands in the vicinity of the ‘line of posts’. A bed of Zostera noltii was recorded to the north of St Cuthbert’s Island near Lindisfarne village, which had not been previously recorded in 1999 Aquatic Environments 02/03 Monitoring of BNNC Sands and Mud Flats 3.2 Zostera marina var. angustifolia: Z. marina occurs sporadically amongst the Z. noltii, specifically where there are areas of standing water on the sand flats. Areas where it occurs with some regularity are around the southern end of the bay in the vicinity of ‘Stinking Goat’ and around the creeks that enter the bay from the west (see photograph L46 taken at waypoint 147, adjacent to the Spartina anglica burial experiment area). One area where there is a larger bed of Zostera marina and Enteromorpha spp. without the Z. noltii, is found on the shore where ‘Black Low’ Creek spreads across the soft muddy-sand to the north of Granary Point on the east side of the bay. The polygons of mixed Zostera spp. shown on maps 1-3 are generally dominated by Zostera noltii and Enteromorpha spp. and Zostera marina is only present sporadically where conditions allow as noted above and usually with Enteromorpha spp.. 3.3 Enteromorpha spp.: Enteromorpha spp., being generally annual in its growth habit on the Lindisfarne sand flats, grows over the Zostera spp. throughout the spring and summer months, particularly where there is an increased mud component to the substratum. This is most notable on Fenham Flats and eastern Holy Island sands, where in places by September the Enteromorpha spp had formed a ‘blanket’ above the Zostera spp. sward. These ‘blankets’ begin to roll up in the autumn, as can be seen in photograph L39 (waypoint 139), though if the weather remains calm, they can persist until October (S. Peaty pers. comm.). Occasional beds of pure Enteromorpha spp. also occur in the bay, the most notable of these being at Granary Point below the Zostera noltii and on Holy Island Sands in several patches on the uppershore on both the east and west sides of the sand flats. 3.4 Mytilus edulis (mussels): Mussel beds were recorded at numerous locations in Lindisfarne Bay. They occur at varying densities, from diffuse (<5% cover) to dense (>20% cover). The main bed within the bay is located on the east side, inside the Old Law promontory where the mussel density reaches 100% cover in places. This bed is considered by the author to be of local nature conservation interest for the occurrence of the large intertidal pools that occur within the mussel bed that are largely undisturbed by man or nature (see photograph L10, waypoint 169). This feature has allowed considerable growth of crustose coralline algae around many of the mussels,