Emanuela Claudia La Marca

Drawing the Line at Neglected Marine Ecosystems: Ecology of Vermetid Reefs in a Changing Ocean

Vermetid mollusks form reefs that protect coasts from erosion, regulate sediment transport, serve as carbon sinks, and provide habitat for many fish and invertebrates. This biogenic habitat is found in tropical, sub-tropical, and warmtemperate coastal areas, such as Bermuda, oceanic islands in Brazil, and Hawaii, several locations within the Caribbean and the Mediterranean. These reefs are functionally similar to tropical coral fringing reefs but are built by gregarious M. Milazzo (*) • E.C. La Marca (*) • C. Alessi (*) • R. Chemello (*) Department of Earth and Marine Sciences, University of Palermo, Palermo, Italy e-mail: marco.milazzo@unipa.it; emanuelaclaudia.lamarca@unipa.it; cinzia.alessi01@community. unipa.it; renato.chemello@unipa.it M. Fine (*) Bar-Ilan University & Interuniversity Institute for Marine Sciences, Eilat, Israel e-mail: maoz.fine@biu.ac.il # Springer International Publishing Switzerland 2016 S. Rossi (ed.), Marine Animal Forests, DOI 10.1007/978-3-319-17001-5_9-1 1 vermetid gastropods cemented by a crustose coralline algal species, which probably triggers their settlement. Some descriptive studies in different regions worldwide and comparisons among tropical and Mediterranean reefs contributed to show their important role as engineered habitat and biodiversity hotspots. In recent years, a dramatic decrease in the vermetid live cover was recorded in the Eastern basin of the Mediterranean, with some documented local extinctions within a few decades. Pollution and the spread of invasive species are potential threats to this animal forest and to the biodiversity it supports. Yet, the response of the vermetid reef to climate change is almost unknown, although recent experiments demonstrated high sensitivity of this snail species to ocean acidification. Hence, the ongoing rapid environmental change and increasing anthropogenic use along the coast may have detrimental effects on the remaining reefs and therefore significant ramifications for coastal systems in the Mediterranean and subtropical and warm-temperate regions. This chapter aims at filling these knowledge gaps by presenting both a short literature-based study and a set of new research paths to explore and improve conservation and research activities given the range of ecosystem services pristine vermetid reefs may provide.

Recruitment patterns in an intertidal species with low dispersal ability: the reef-building Dendropoma cristatum (Biondi, 1859) (Mollusca: Gastropoda)

Abstract In the Mediterranean, the gastropod Dendropoma cristatum (sin. D. petraeum (Monterosato, 1884)) is the primary builder of the vermetid reef, an intertidal bioconstruction of exceptional ecological importance. Despite awareness of the need for conservation of this key species, the biology of D. cristatum remains poorly understood. The recruitment of D. cristatum deserves particular attention because the absence of a planktonic larval stage limits its dispersal ability. We examined the temporal pattern of recruitment during the breeding season of D. cristatum from June to September in 2013. Specifically, we compared the two portions of the vermetid reef (i.e. the inner edge and the outer edge) at localities with different exposures to wave motion. The number of recruits peaked in July, when it was significantly higher in the outer than in the inner edge. No differences emerged between localities with different wave exposures; however, the width of the reef was significantly related to the exposure index. Although there are still several gaps in our knowledge of the recruitment dynamics of D. cristatum, this study contributes to characterising recruitment rate variation at small spatial and temporal scales.

Settlement performance of the Mediterranean reef-builders Dendropoma cristatum (Biondi 1859) in response to natural bacterial films

The gastropod Dendropoma cristatum is a biogenic engineer of the central Mediterranean, forming reefs along the lower rocky intertidal fringe with a remarkable ecological role. To understand whether reef-associated biofilm cultivable bacterial and biofilm ageing may trigger the settlement of the juvenile snails, a combination of laboratory techniques and field experiments was used. Reef-associated biofilm cultivable bacteria were isolated, and a settlement-choice experiment was performed in situ on artificial biofilms composed of i) a mixture of six biofilm-forming selected isolates, ii) all the cultivable bacteria, and iii) 13-, 23-, 32-day old biofilms formed under natural conditions. Overall, settlement rate significantly differed among biofilm treatments (p < 0.0001). A significant positive correlation between biofilm ageing and juvenile D. cristatum settlement was assessed (r = 0.69 (p < 0.001), whereas the biofilm bacterial composition (relatively to the cultivable fraction) did not show any effect on the vermetids settlement rate.