Causes of Macrofaunal Outline on a Dissipative Beach

Causes of Macrofaunal Outline on a Dissipative Beach Investigating the causes of macrofaunal outline on a dissipative beach in Abberffraw. Aim: To investigate macrofaunal abundance and distribution pattern across five different shore levels. Hypothesis: whether physical and biological factors have direct correlation on community structures of infauna species. Cisneros et al. (2011) and Croker Hatfield (1980) have tested this hypothesis and reported significance. Figure lists are illustrating distribution and abundance of 31 species sampled on a vertical gradient across 5 shore heights. Out of these, three polychaetes species; Scolelepis squamata, Scoloplos armiger, Nephtys sp, including twocrustaceans Bathyporeia sp, and Eurydice pulchra were found throughout sampling stations (Fig 2). As shore slope decreases species diversity increases (Fig 1). Station 2 had maximum abundance (4050 ind./ m2) whereas station 4 had the greatest species richness (SR = 18) (Fig 1). Sandy shores are dynamic environments with biotic (Croker Hatfield, 1980) and abiotic (Cisneros et al., 2011) conditions changing continuously, influencing species spatial scales along shores. Three major environmental factors, influencing community structures (McLachlan Brown, 2006); 1. beach type (physical gradient/ sediment texture); 2. tidal regime (wave action/ moisture/ organic enrichment); and 3. swash climate (water filtration) (Defeo, McLachlan, 2005). Zonation patterns are evident, due to tidal movement (Brazeiro Defeo 1996), seasonal migration (De Alava Defeo 1991), and predation contributing to the variations. Ansell et al., (1999), reported that predators migrate following prey species. Cisneros et al. (2011), stated physical drivers influenced macrofaunal community. Abberffraw shore consists of fine grainy sand particles with small interstitial space facilitating burrowing (McLachlan et al., 1996) and slower water filtration (McLachlan Brown, 2006) providing suitable living conditions. Dominating middle and lower shores are Polychaetes (Connor et al., 1997) in water-saturated sediments whiles crustaceans are generally distributed at different shore levels (Dahl, 1952). Work, et al., (2008) found that water drainage is critical in determining polychaets presence; Scolelepis squamat, Scoloplos armiger andNephtys sp.can tolerate drained sediments (Connor et al., 1997) explaining the occurrence at higher stations (Fig 2). More studies are needed in determine zonation and causes (Defeo, McLachlan, 2005). References. Brazeiro, A., Defeo, O. (1996). Macroinfauna zonation in microtidal sandy beaches: Is it possible to identify patterns in such variable environments? Estuarine, Coastal and Shelf Science, 42(4), 523-536. Cisneros, K. O., Smit, A. J., Laudien, J., Schoeman, D. S. (2011). Complex, dynamic combination of physical, chemical and nutritional variables controls spatio-temporal variation of sandy beach community structure. PloS One, 6(8), e23724. Connor, D., Brazier, D., Hill, T., Northen, K. (1997). Marine nature conservation review: Marine biotope classification for britain and ireland. volume 1. littoral biotopes. JNCC Report, 229. Croker, R., Hatfield, E. (1980). Space partitioning and interactions in an intertidal sand-burrowing amphipod guild. Marine Biology, 61(1), 79-88. Dahl, E. (1952). Some aspects of the ecology and zonation of the fauna on sandy beaches. Oikos, 4(1), 1-27. De Alava, A., Defeo, O. (1991). Distributional pattern and population dynamics of excirolana armata (isopoda: Cirolanidae) in a uruguayan sandy beach. Estuarine, Coastal and Shelf Science, 33(5), 433-444. Defeo, O., McLachlan, A. (2005). Patterns, processes and regulatory mechanisms in sandy beach macrofauna: A multi-scale analysis. Marine Ecology Progress Series, 295, 1-20. McLachlan, A., Brown, A. (2006). Sandy beaches as ecosystems. Work, F., Hubble, M., Teague, L., Tennant, K., Skidmore, L., Webb, H., Gillespie, B. Lister, J. (2008). Project: SC 410354 Date of Issue: June 2008. McLachlan, A., de Ruyck. A., Hacking, N. (1996). Community structure on sandy beaches: patterns of richness and zonation in relation to tide range and latitude. Revista Chilena de Historia Natural 69, 451-67