ORIGINAL PAPER Spatiotemporal coupling/decoupling of planktonic larvae and benthic settlement in decapods in the Scottish east coast Maria Pan • Graham J. Pierce • Carey O. Cunningham • Steve J. Hay Received: 1 December 2009 / Accepted: 28 August 2010 / Published online: 6 October 2010 Ó Springer-Verlag 2010 Abstract Settlement patterns and the relationship between meroplanktonic larvae and settlement in deca- pods were studied on the Scottish east coast. Artificial settlement substrates (ASS), deployed at two locations (sandy vs. rocky sea substrates), were employed to col- lect megalopae and newly settled juveniles. Abundance of meroplanktonic larvae was used as an indicator of larval supply. The results showed a clear seasonality in settlement rates, and in some cases, significant differ- ences between sites were detected. Nevertheless, the interference of the ASS with the surrounding habitat limits the study of spatial variability in settlement rates. Significant cross-correlation was found between the abundance of megalopae and juveniles in the collectors and planktonic larval abundance a month earlier. For individual species, this relationship was observed only in Pisidia longicornis. Complexities caused by the great variety of pre- and post-settlement processes, alongside effects of secondary dispersals of early juveniles may have obscured the relationship between meroplanktonic larvae and juveniles in other species. Introduction In marine benthic invertebrates with complex life cycles, such as decapod crustaceans, settlement and subsequent recruitment are crucial processes affecting their population dynamic, a central issue in marine ecology studies. The influence of pre- and post-settlement processes in the adult population has been the subject of multiple studies, and attempts have been made to find a relationship between larval supply and recruitment, and the benthic populations. Also, the links between larval supply and settlement are not clearly established. Although in some studies a positive relationship has been found between larval supply and set- tlement (Gime ´nez and Dick 2007), in other cases there is a lack of correlation between the two processes (Loher and Armstrong 2000; Moreira et al. 2007) or limitations in the relationship; Quijo ´n and Snelgrove (2005) found a correla- tion only when later larval stages were considered, and Miron et al. (1995) obtained the best correlation results using data from larval stages close to settlement. These and other studies (Moksnes and Wennhage 2001; Paula et al. 2006) have advised on the multiple biotic (larval developmental stage, behavioural component of larvae and settlers, migra- tion, predation) and abiotic (physical processes affecting larval transport) factors that can affect and obscure the cor- relation between larval supply and settlement or recruitment. There is a high mortality associated with the early phases of the life cycle, and the likelihood of survival is enhanced by the behaviour of the larvae, selecting the most suitable substrate on which to settle (Ferna ´ndez et al. 1993; Palma et al. 1998; Moksnes 2002; van Montfrans et al. Communicated by P. Kraufvelin. M. Pan (&) Á C. O. Cunningham Á S. J. Hay Marine Scotland, Victoria Rd, PO Box 101, Aberdeen AB11 9DB, United Kingdom e-mail: pan.mariac@gmail.com G. J. Pierce Oceanlab, University of Aberdeen, Main Street, AB41 6AA Newburgh, Aberdeenshire, UK G. J. Pierce Instituto Espan ˜ol de Oceanografı ´a, Centro Oceanogra ´fico de Vigo, P.O. Box 1552, 36200 Vigo, Spain 123 Mar Biol (2011) 158:31–46 DOI 10.1007/s00227-010-1540-3