Utrecht Studies in Earth Sciences 57 Seagrass Mollusks As a Model Group for Paleoecological and Paleodiversity Studies Sonja
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Utrecht Studies in Earth Sciences 57 Seagrass Mollusks as a Model Group for Paleoecological and Paleodiversity Studies Sonja Reich Utrecht 2014 Members of the comittee: Prof. dr. Juan Carlos Braga FacultadUniversidad de Ciencias de Granada, - Estratigrafía Spain y Paleontología Dr. Mathias Harzhauser Geologisch-Paläontologische Abteilung Naturhistorisches Museum Wien, Austria Prof.Faculty dr. ofWout Geosciences Kriegsman Utrecht University, The Netherlands Prof.Faculty dr. ofJelle Geosciences Reumer Utrecht University, The Netherlands Prof. dr. Martin Zuschin Fakultät für Geowissenschaften, Geographie und Astronomie Universität Wien, Austria The research presented in this thesis is part of the Throughflow Project funded by the Marie Curie Actions Plans, Seven Framework Programme (grant no. 237922). Research was carried out the Department of Geology, Naturalis Biodiversity Center, Leiden, The Netherlands. TheISBN: cover 978-90-6266-363-7 photo of a living Smaragdia was printed with friendly permission of S. Lobenstein (www. enelmar.es). Cover design: Margot Stoete, Department of Cartographic and Graphic Design, Faculty of Geosciences, Utrecht University. Printed in the Netherlands by CPI-Wöhrmann Print Service, Zutphen Seagrass Mollusks as a Model Group for Paleoecological and Paleodiversity Studies Studies Weekdieren van het Zeegras als Modelgroep voor Paleomilieu en Biodiversiteit (met een samenvatting in het Nederlands) Seegrass Mollusken als Modelgruppe für Studien der Paläoökologie und Paläodiversität (mit einer Zusammenfassung in deutscher Sprache) P roefschrift ter verkrijging van de graad van doctor aan de Universiteit Utrecht op gezag van de rector magnificus, prof.dr. G.J. van der Zwaan, ingevolge het besluit van het col- lege voor promoties in het openbaar te verdedigen op dinsdag 24 juni 2014door des middags te 12.45 uur Sonja Reich geboren op 3 oktober 1981 te Kiel, Duitsland Promoter: Prof. dr. L.J. Lourens Co-promotoren: Dr. F.P. Wesselingh Dr. J.A. Todd v Contents Summary and Thesis Outline 1 Introduction Chapter 1 - Indirect Paleo-Seagrass Indicators (IPSIs): A 9 SectionReview 1 - Mollusk Assemblages from the Miocene of Indonesia Chapter 2 - A Highly Diverse Molluscan Seagrass Fauna 65 from the Early Burdigalian (Early Miocene) of Banyunganti (South-Central Java, Indonesia) 181 Chapter 2 - Plates Chapter 3 - Diversity and Paleoecology of Miocene Coral- 223 SectionAssociated 2 - MollusksShelly IPSIs from East Kalimantan, Indonesia 247 Chapter 4 - Gastropod Associations as a Proxy for Seagrass Vegetation in a Tropical, Carbonate Setting (San Salvador, Bahamas) Chapter 5 - Paleoecological Significance of Stable Isotope 283 SynthesisRatios Miocene Tropical Shallow Marine Habitats (Indonesia) Chapter 6 - Composition, Ecology and Diversity of Seagrass- 315 Associated Mollusk Faunas in the Miocene of the Marine Biodiversity Hotspot, Indonesia vi Supplementary Material 347 References 433 Samenvatting 479 Zusammenfassung 485 Acknowledgements 493 Curriculum Vitae 495 List of Papers 497 Summary and Thesis Outline Today’s global marine diversity hotspot, or center of maximum biodiversity, is located in the Indo-West Pacific (IWP), namely in the Indo-Malayan region, including Malaysia, the Philippines, Indonesia, and Papua New Guinea (Hoeksma, 2007; Renema et al., 2010). Numerous groups of marine organisms, for instance foraminifera, mollusks, and corals contribute to the high taxonomic richness (e.g., Bellwood et al., 2005; Hoeksema, 2007; Kohn, 1990; Wilson and Rosen, 1998). The exceptional biodiversity in the region is thought to have originated in the Early Neogene with the diversification of scleractinian coral reefs and associated organisms (e.g., Wilson and Rosen, 1998; marine organisms in the Cenozoic of SE-Asia are comparatively sparse, the collection Chapter 6). Because the available fossil data to document patterns of diversification of of new data is needed in order to document the timing and context of diversification. To perform this task, the Marie-Curie Initial Training Network (ITN) Throughflow was formed in 2010, focusing on Miocene fossils and their paleohabitats of East Kalimantan, TheIndonesia. initial aim This of thesis the research represents presented one of ineleven this thesis projects was of the the reconstruction Throughflow ofprogram. marine diversity over time it is necessary to compare faunas from the same paleohabitat, mollusk biodiversity in the Miocene of Indonesia. To make useful comparisons of species because species richness varies considerably among different environments (Chapter were selected as a model habitat and model group for this research: 3). For the following reasons seagrass meadows and associated mollusk assemblages Significance 1. Seagrass meadows are ecologically important marine habitats with a worldwide distribution and are of high scientific interest (Chapter 1). They are highly productive and play an important role in the ocean’s carbon cycle. Seagrass roots stabilize sediments and therefore help prevent coastal erosion. Seagrass meadows dimensional structuring provides a habitat for numerous associated organisms, can reduce eutrophication and bind organic pollutants. Furthermore, their three- including economically important species. For instance, seagrass meadows act as a are threatened by human impact, therefore studies on the response of this ecosystem nursery habitat for fish. Like other shallow marine environments seagrass meadows (e.g., indicated by the diversity of associated organisms) to small and large scale Summary and Thesis Outline 2 environmentalAbundance and changes species in therichness past are of critical importance. 2. Mollusca represent a large animal phylum that includes amongst others snails, mussels and clams, and squids. They are an important richness in the habitat and are usually very abundant or even numerically dominant seagrass-associated higher taxon, because they contribute significantly to the species in seagrass-associated invertebrate communities. Yet, compared to other marine a good opportunity to study this group within a restricted time frame without being environments (e.g., coral reefs), mollusk diversity is not exceedingly high, providing overwhelmedBiodiversity. by species numbers (Chapters 2, 3, 6). 3. Seagrasses and associated organisms follow global diversity patterns. Seagrasses, like numerous other shallow marine organisms, have their highest species diversity in the Indo-Malayan region, as do a number of highly speciose mollusk 4families. Preservation that occur commonly in modern seagrass meadows (Chapter 6). Seagrass meadows are mainly located in areas where the plants are protected from strong currents and wave action; the plant cover itself additionally reduces water flow velocities. Seagrasses trap and stabilize sediments, therefore sediments within meadows are often finer-grained than in adjacent unvegetated areas (Chapter 1). These parameters increase the preservation potential of associated organisms and decrease the chance of transport of material out of the habitat. rates of associated organisms and might therefore be another control for reduced Additionally, increased pH-values in seagrass environments may enhance calcification taphonomic shell loss in seagrass habitats. Seagrass-associated mollusk faunas are among the best preserved in marine Miocene deposits in the study area, whereas the record of reef-associated mollusks is highly biased against by diagenetic loss of shell carbonateAvailability. (Chapters 2, 3, 5, 6). 5. The presence of seagrasses in the Miocene of Indonesia in combination with the increased fossilization potential of mollusks in seagrass meadows led to the availability of several fossil seagrass-associated mollusk faunas in the study area that represent different stratigraphic intervals (Chapters 2, 5, 6). However, the focus on a specific paleohabitat also comes with challenges; in particular the addressed paleohabitat has to be reliably identified in the geological record. 3 poor fossil record and their former presence has to be inferred using other approaches Seagrasses as well as their pollen easily disintegrate. Therefore, seagrasses have a (Chapter 1). This is why the focus of this research shifted towards investigating possibilities of the successful identification of paleo-seagrass meadows from other data as a base for future biodiversity studies. This includes the characterization of mollusk assemblages from seagrass meadows and other marine environments in the study area (Chapters 2 and 3) as well as studies on the potential of mollusk assemblages as paleoenvironmental indicators (Chapter 4 and 5). Subsequently this has led to a first attempt of reconstructing Miocene biodiversity of seagrass-associated also addresses challenges that come with such studies, such as analysis of material mollusk assemblages in today’s biodiversity hotspot (Chapter 6). The latter chapter Althoughobtained fromtaxonomy differing is fundamental collection methods to studies and onpost-collection ecology and treatmentbiodiversity, of samples.detailed taxonomic revisions and the description of new species were not the principal goals in this research. However, four new seagrass-associated gastropod species are described from the early Burdigalian (early Miocene) of Banyunganti, Java, Indonesia (Chapter 2). It is assumed that a high percentage of the taxa presented here (Chapters 2, 3, and 6) is still undescribed. The use of open nomenclature in this research provided a pragmatic approach to conducting