NATURAL ENGLAND CHESIL & THE FLEET EMS Survey of Shingle Springline Communities DATA REPORT January 2012 Report Prepared by Lin Baldock & Jon Bass 01305 852585 [email protected] [email protected] NATURAL ENGLAND Chesil & the Fleet EMS Survey of Shingle Springlines Communities _____________________________________________________________________________________________________ TABLE OF CONTENTS EXECUTIVE SUMMARY...........................................................................................................................I 1 INTRODUCTION.............................................................................................................................. 2 2 SPRING CLASSIFICATION............................................................................................................. 2 3 SPRINGS – MAPPING AND SAMPLING METHODS..................................................................... 3 4 RESULTS AND DISCUSSION......................................................................................................... 5 5 MONITORING PROTOCOL FOR SHINGLE SPRINGLINE COMMUNITIES ................................. 7 6 ACKNOWLEDGEMENTS ................................................................................................................9 7 REFERENCES................................................................................................................................. 9 List of Tables Table 1 Locations of fast springs in the eastern Fleet and sampling points at Langton Hive Point and Clouds Hill. Table 2a List of taxa recorded in Fleet springline communities – 2011 Table 2b Habitat descriptions of Fleet springline communities - 2011 Table 3 List of taxa recorded in Fleet springline communities – historical data List of Figures Figure 1 Preliminary comparison of community similarities between spring and seep samples in the Fleet (the closer to each other on the plot the more similar the community). List of Plates Plate 1 Typical fast flowing spring – eastern Fleet. Plate 2 Fast flowing spring eastern Fleet showing characteristic algal growth where there is flowing water over the pebbles. Plate 3 Pebbles embedded in anaerobic, fine sediment in a non-spring area - eastern Fleet. Plate 4 Pebbles in a seep area in the mid-Fleet cleared of a mat of dead Zostera leaves. Plate 5 Close up of pebbles in a mid-Fleet seep area showing open spaces between pebbles colonised by the bivalve Lasaea rubra. Plate 6 Algal flora typical of fast springs – eastern Fleet. Plate 7 Heavily sedimented pebbles with wracks in a non-spring area – eastern Fleet Plate 8 Location of seep in the mid-Fleet just below the line of halophyte scrub (two sample locations shown). Plate 9 De Folin’s lagoon snail (Caecum armoricum) from an eastern Fleet spring. Plate 10 The cumacean crustacean Nannastacus unguiculatus from an eastern Fleet spring. Plate 11 The amphipod crustacean Eulimnogammarus obtusatus from an eastern Fleet spring. _____________________________________________________________________________________________________ Lin Baldock & Jon Bass i January 2012 NATURAL ENGLAND Chesil & the Fleet EMS Survey of Shingle Springlines Communities _____________________________________________________________________________________________________ Plate 12 The tanaeid crustacean Apseudes talpa from an eastern Fleet spring. Plate 13 The slit limpet Emarginula conica from an eastern Fleet spring. Plate 14 Chiton (Achanthochitona crinitus) from an eastern Fleet spring. Plate 15 The mollusc Onuba aculeus from a mid-Fleet seep. Plate 16 The hydroid Clava multicornis from a mid-Fleet seep Plate 17 The pulmonate mollusc Auriculinella bidentata from a mid-Fleet seep. Plate 18 The bivalve Lasaea rubra var. pallida from a mid-Fleet seep. Plate 19 De Folin’s lagoon snail Caecum armoricum from a mid-Fleet seep. List of Video Clips Video 1 Fast flowing spring – eastern Fleet _____________________________________________________________________________________________________ Lin Baldock & Jon Bass ii January 2012 NATURAL ENGLAND Chesil & the Fleet EMS Survey of Shingle Springlines Communities _____________________________________________________________________________________________________ EXECUTIVE SUMMARY A preliminary survey of Shingle Springline Communities in the Fleet was undertaken in the summer and early autumn of 2011. These springline communities were identified as a qualifying sub-feature of the Chesil and the Fleet European Marine Site by English Nature but the extent of the habitat remained unknown, neither was a methodology for surveying this sub-feature established at that time. The aims of the present project were therefore: • to develop a sampling methodology for the spring communities, • compare mollusc species found in 2011 with work reported in 1989, • identify other invertebrate species where possible. Two types of spring, and hence two types of springline community were found to be present on the Chesil Bank shore of the Fleet. • Fast flowing springs – eastern Fleet • Less active springs (seeps) – western Fleet. The fast flowing springs are restricted to the eastern Fleet where they appear as discrete areas of fast flowing seawater running out of the beach at about mid-tide level. The pebbles in these areas are not embedded in smooth, ochorous clay nor compacted in anaerobic sediment. Notably these active spring areas are associated with loose, clean pebbles which are very mobile underfoot. The less active springs (seeps) are located in the mid- and western Fleet. These seeps are not immediately obvious since water does not visibly run out as springs but they can be identified by the fact that they occur in areas of the shore where the pebbles are not compacted by either fine or anaerobic sediment but shift readily underfoot. The location of change between these two “spring” types has not been identified but is likely to be at the transition point in the hydrological system of the Fleet in Butterstreet Cove. A total of twenty fast flowing springs were identified in the eastern Fleet and three sites with less active springs or seeps were located opposite Langton Hive Point and Clouds Hill. Samples of pebbles from the two spring types were collected using cores and returned to the laboratory for sorting and analysis enabling a characteristic community to be identified for each kind of spring. The seep community of the mid- and western Fleet was found to support very high densities of de Folin’s lagoon snail (Caecum armoricum) (10,000s m-2) with both adult and juvenile snails being present together with 100,000s m-2 of the small bivalve Lasaea rubra. This compares with C. armoricum densities of a few thousand m-2 reported for sites in Sussex and Kent. Results of the present survey are tabulated and compared with historical data available on the composition of these special spring communities. The vulnerability of the spring/seep habitats and communities is discussed and a monitoring protocol for the springs has been elaborated. Guidance was developed to identify the fast flowing springs and the slow seeps along the Chesil Bank shore of the Fleet together with advice on timing and methodology for sampling the communities. _____________________________________________________________________________________________________ Lin Baldock & Jon Bass i January 2012 NATURAL ENGLAND Chesil & the Fleet EMS Survey of Shingle Springlines Communities ____________________________________________________________________________________________ 1 Introduction A collaborative agreement schedule between Natural England and Ilchester Estates was recently developed to undertake a preliminary survey of Shingle Springline Communities in the Fleet. These springline communities were identified as a qualifying sub-feature of the Chesil and the Fleet European Marine Site by English Nature (1999). In this publication the distribution of these spring communities was shown diagrammatically as extending continuously the full length of the Fleet from Ferrybridge to the Abbotsbury embayment along the Chesil Bank shore. No methodology for surveying this sub-feature was established at that time and the aim of the present study was to evaluate and develop a methodology for mapping and monitoring the springline communities. The aims of the project were: • to develop a sampling methodology for the spring communities, • compare mollusc species found in 2011 with work reported in 1989, • identify other invertebrate species where possible. The springline communities were first identified by Dennis Seaward as holding an unusual fauna, particularly molluscs most notably De Folin’s lagoon snail Caecum armoricum. Preliminary results were reported in a number of publications (Seaward, 1987a, 1987b, 1989; Little et al., 1989). However little information was provided at the time on the extent of the springline habitat and reports on the composition of the community are scattered in a few publications and within the grey literature. The preliminary survey work and development of methodology reported here was carried out by Lin Baldock and Jon Bass over the summer and early autumn of 2011. Information was obtained on the distribution and characteristics of the springs along the length of the Fleet and methods are proposed for monitoring these features and the associated biotic communities in the future. 2 Spring Classification The first task was to identify the springs following the descriptions provided by Seaward (1987a, 1987b) and develop a preliminary