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Changes in Intertidal Communities in Strangford Lough S. Vize, S.J. Preston & A. Portig.

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Presentation on theme: "Changes in Intertidal Communities in Strangford Lough S. Vize, S.J. Preston & A. Portig."— Presentation transcript:

1 Changes in Intertidal Communities in Strangford Lough S. Vize, S.J. Preston & A. Portig

2 Introduction Northern Ireland Littoral Survey (NILS)Northern Ireland Littoral Survey (NILS) Strangford Lough Ecological Change Investigation (SLECI)Strangford Lough Ecological Change Investigation (SLECI) SitesSites MethodologyMethodology Summary of SLECI intertidal findingsSummary of SLECI intertidal findings ConclusionsConclusions

3 Northern Ireland Littoral Survey (NILS) completed in 1980’s (Wilkinson et al., 1988) 200 sites around Northern Ireland 59 sites in Strangford Lough 29 sediment sites 30 rocky shore sites Strangford Lough Ecological Change Investigation (SLECI) 2003-’04 17 sites in Strangford Lough 8 sediment sites (4 firm, 4 soft) 9 rocky shore sites

4 Shores of Strangford Lough Major rocky shore habitat – boulder in nature; ranging from cobbles to large boulders Boulder shores may be steep & narrow or gently sloping & extensive Areas of muddy sand & muddy gravel & pebbles – often associated with boulder shores Rocky shores on eastern side of lough physically more diverse than western Western shores are siltier than slightly more wave exposed eastern shores North end – wide sedimentary flats, mainly muddy sand

5 Soft-Sediment Sites Mahee Island North Black Causeway, Mahee Island North, Quarterland Bay & Taggart Island Sampling from boat at high water 10 x Van Veen grabs (0.0625m 2 ) Sieved (1 mm), retained, preserved and identified 2 grabs (abundance); 8 grabs (presence/absence)

6 Firm-Sediment Sites Mid Island Bay Greyabbey Bay Reagh Bay Newtownards A - E

7 Location descriptions & sketch maps from NILS survey examined Samples from upper, upper-mid, mid, mid-lower and lower shore 5 cores at each shore height/location NILS survey: 5 x box cores (0.01 m 3 ) SLECI survey: 5 x cylinder cores (0.025 m 3 ) Sieved (1 mm), retained, preserved and identified 1 core (abundance); 4 cores(presence/absence) Firm-Sediment Sites

8 Rocky Shore Sites Green Island Kircubbin PointLong Sheelah Mahee Island Marlfield Rocks

9 Original NILS transect locations revisited and re-surveyed All zones described and compared to NILS NILS survey methodology repeated: 8-point abundance scale Species composition within each zone: abundance of species identifiable in the field determined; unknown species collected for identification in the lab. Voucher specimens collected and preserved Rocky Shore Sites

10 Total number of species during NILS and SLECI survey, along with mean (  se) number of species per site recorded by SLECI. Pooled data from 10 x 1 litre Van Veen grabs Soft-Sediment Sites

11 Total number of species at Newtownards sites A - E Strangford Lough. NILS survey: 5 x box cores (0.01 m 3 ) pooled and SLECI survey: 5 x cylinder cores (0.025 m 3 ) pooled. Firm-Sediment Sites +3;;+3;; Newtownards Sites A - E

12 Firm-Sediment Sites Newtownards Sites A - E Two-dimensional MDS plot showing similarity relationships between the community composition at firm sediment sites (A-E) located at Newtownards, from NILS and SLECI surveys.

13 Number of species recorded at different shore heights during the NILS survey and the SLECI survey at Greyabbey Bay. NILS survey: 5 x box cores (0.01 m 3 ) pooled and SLECI survey: 5 x cylinder cores (0.025 m 3 ) pooled Firm-Sediment Sites +3;;+3;; Greyabbey Bay

14 Firm-Sediment Sites Number of species at different shore heights from NILS survey and SLECI survey, Mid Island Bay. NILS survey: 5 x box cores (0.01 m 3 ) pooled and SLECI survey: 5 x cylinder cores (0.025 m 3 ) pooled. Mid Island Bay

15 Firm-Sediment Sites Number of species at different shore heights from NILS survey and the SLECI survey at Reagh Bay. NILS survey: 5 x box cores (0.01 m 3 ) pooled and SLECI survey: 5 x cylinder cores (0.025 m 3 ) pooled. Reagh Bay

16 Rocky Shore Sites ANOSIM R = 0.176, p = Two-dimensional MDS plot showing similarity relationships between the community composition at different zones on the shore at rocky shore sites. ANOSIM R = 0.122, p = BEFORE AFTER

17 Rocky Shore Sites SIMPER analysis results: the average abundance and percentage contributions of the species that contributed most to the Bray-Curtis dissimilarity for each survey. Species Average Abundance Percent Contrib. NILSSLECI (average dissim.= 73.56) Verrucaria maura Hildenbrandia rubra Ascophyllum nodosum Fucus spiralis Littorina saxatilis Semibalanus balanoides Fucus serratus Pelvetia canaliculata Spirorbis spp Gibbula cineraria Patella spp Polysiphonia spp Carcinus maenas Littorina littorea

18 Rocky Shore Sites South Island Photo from NILS survey Photo from SLECI survey

19 North end North end

20 Sargassum muticum present: Chapel Island Causeway Kircubbin Point Marlfield Rocks Limestone Rock Long Sheelah South Island Invasive Alga

21 Summary Soft-sediment sites: high spatial variability – not indicative of temporal change Soft-sediment sites: high spatial variability – not indicative of temporal change Firm-sediment sites: expected increase in numbers of species due to doubling sampling effort Firm-sediment sites: expected increase in numbers of species due to doubling sampling effort Rocky shore sites: significant difference between NILS & SLECI surveys – difference still apparent after species repertoires refined to reduce survey/species expertise Rocky shore sites: significant difference between NILS & SLECI surveys – difference still apparent after species repertoires refined to reduce survey/species expertise Loss of Ascophyllum nodosum at Marlfield Rocks, Mahee Island, Kircubbin Point, South Island. Loss of Ascophyllum nodosum at Marlfield Rocks, Mahee Island, Kircubbin Point, South Island. Japanese alga Sargassum muticum now present in Strangford Lough. Japanese alga Sargassum muticum now present in Strangford Lough.

22 Acknowledgements Investigation commissioned by the Environment and Heritage Service, Northern Ireland Adam Mellor (DARD) for assisting with boat work David Hall (Unicomarine) NMBAQCS quality control Mark Johnson (QUB) and James Strong (DARD) for assisting with data analysis Christine Maggs (QUB) for assisting with algal identification


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