Public evening lecture:
Conference Keynote lectures:
(presented in German language)
20.09.2006,
20:00h
Haus
der Wissenschaft, Großer Vortragssaal, 1. OG (
Map)
Reinhold
LeinfelderHumboldt-Universität zu Berlin, Germany
An ecosystem in transition - the reefs of the Jurassic
The Jurassic Age, 200-130 Million of years ago, is well known for its, often gigantic, dinosaur species, which gave rise to commercial blockbuster movies, such as the Jurassic Park series as well as to well-known edutainment productions like BBC’s Walking with Dinosaurs. Besides all fiction, fact is that biodiversity including dinosaurs was rapidly expanding during the Jurassic. This is particularly true of the marine life, giving rise to the enormous reef development during the Late Jurassic, which is unparalleled from other times of Earth History. Reef regions expanded tens of thousands of kilometers, stretching from Kazakhstan to Florida or from England to Tanzania.
Besides coral reefs, other reef types such as sponge reefs or microbial reefs existed, all being adapted to distinct environments. Stone corals forming coral reefs were already of the modern, scleractinian type, with many forms being as complex as modern star corals or brain corals. However, a much greater variety of coral reef types and coral reef settings existed than today, reason of which is that modern strategies of corals, especially the adaptation to nutrient restriction by photosymbiosis started to develop but at the same time many other strategies were implemented as well. To illustrate such strategies we use a „Swabian House Building“ metaphor: considering Jurassic reefs as self-made homes built by the owners, their complexity depends on the properties of the available ground, limitations by the available energy and overall environment, as well as the availability of co-workers and working materials.
Jurassic reefs are, indirectly, more known to the public than might be imagined: beautiful landscapes such as the Swabian and Franconian Alb of Southern Germany owe their popularity to scenic reef rock relics. Moreover, a great variety of buildung and cover stones from Jurassic reefs, such as the Adnet Limestone of the Salzburg area or the Treuchtlingen Marble of southern Germany, or even tooth paste and pharmaceutical products are derived from Jurassic reef rocks. Last but not least, the great majority of the world’s petroleum and gas is hosted by, and produced from, reef-related Jurassic sediments of the Arabian peninsula. The Jurassic age might therefore better be called the Jurassic Reef Park rather than the Jurassic Dino Park.
See: Jurassic Reef Park: www.palaeo.de/edu/JRP
Anja ScheffersUniversität Duisburg-Essen, Germany
Cyclone and Tsunami Deposits - what Paleo-Science Reveals about Extreme Events and their Impacts on Coral Reefs
The catalogue of the influence of natural disturbances on coral reefs is extremely complex and comprehensive, as reflected in lively scientific debates over the last decades. But, our short historical records do not provide us with sufficient information on extreme events such as tropical cyclones or tsunami and their natural variability. And, if such information exists it rarely contains details on the fate of coral reef communities, because sedimentology mostly works with the stratigraphy of fine sediments to reconstruct paleo-environments. However, I will show that nature effectively records extreme events – tsunami and tropical storms- and their impacts on coral reefs in form of natural archives present in coarse reef debris. These archives provide information on the full range of spatial and temporal variability of these events.
The short term impact of tropical cyclones on coral reefs is well documented and studied in great detail, but the interaction between tsunami and coral reefs was rather neglected until the recent past, when the Indian Ocean Tsunami in December 2004 caused the greatest tsunami catastrophe in human history. This contribution focuses on these extreme events and will present local observations of modern and ancient tropical cyclones and tsunami within the Caribbean region and coastlines affected by the Indian Ocean tsunami. I will also present evidence (based on a detailed geochronology and qualitative and quantitative analyses of reef debris) that a tsunami was responsible for the destruction of coral reefs on a regional scale in the southern Caribbean around 3000 yrs BP.
Here, a flourishing Acropora palmata-dominated reef has shifted into a Sargassum-dominated ecosystem. So far, reef recovery did not occur. The sedimentary record shows a strong tsunami impact on the north-eastern Bahamas and islands in the Eastern Caribbean for the same time period and it remains to be seen whether these events exerted the same influence on the ancient reefs. Another result of debris analyses is a clear differentiation between storm and tsunami deposits. Whereas the energy (or wave height) of a paleo-event can be calculated by the size of transported boulders or their position onshore, the entire amount of debris is not a good indicator of the transport energy: here the time gap between two events of high energy to produce a new reef body and subsequent new debris plays a crucial role.
I suggest that we may gain a better understanding of coral reef ecosystems or disconformities and their causes by incorporating long-term (multi-century to millennial) records of natural hazards and coarse deposits.
Gilbert Camoin
The last deglaciation in the Indo-Pacific regions: Sea-level records and reef development.
The timing and course of the last deglaciation (23,000-6,000 calendar years BP - cal. yr BP) are essential components for understanding the dynamics of large ice sheets and their effects on Earth's isostasy as well as the complex relationship between freshwater fluxes to the ocean, thermohaline circulation and, hence, global climate during the Late Pleistocene to Holocene.
Coral reefs provide the most accurate records of sea-level changes as corals are excellent sea-level indicators and can be accurately dated by mass spectrometry ; their study helps, therefore, in the determination of the timing of deglaciation events and the understanding of the mechanisms driving the glacial-interglacial cycles.
Coral reefs not only record the timing of sea-level rises and associated climate changes but also the biologic and geologic changes the reef experiences in response to these events.
A detailed regional study of the Western Indian Ocean based on the analysis of drill cores carried out through modern reefs, in combination with observations and sampling of reef foreslopes, and investigations of outcrops provides a comprehensive data base for late glacial to post glacial sea-level changes.
Tahiti (French Polynesia) displays a comprehensive coral reef record of the Last Deglaciation based on drill cores carried out through the modern reef, dredgings around the island and more than 600 m of reef cores with an exceptional recovery that were retrieved from 37 holes ranging from 40 to 120 m water depth during the IODP Expedition #310 « Tahiti Sea Level ».
Peter J. Mumby
Understanding the resilience of coral reefs: a mighty challenge for a mighty problem
The crisis facing coral reefs in terms of climate change and overpopulation is well recognized. Combating these problems presents a daunting challenge to both scientists and policy-makers. Given that managers only have a limited suite of tools at their disposal, reef science should reveal the impact of these tools on the processes driving reef ecosystems.
This talk reviews recent progress in reef ecology and attempts to provide a framework for managing reef resilience explicitly.
John M. PandolfiUniversity of Queensland, Australia
Time, Theory and Trouble in Coral Reefs
The well-recognized challenge to the continued degradation of coral reefs can be considered in the light of new data from time-series and new advances in ecological theory. Specifically, paleo-records provide key insight into understanding ecological processes at the level of the community and provide direct tests of the role of niche theory and neutral theory (demographic stochasticity) in their long-term development. Understanding key ecological processes over long time scales informs conservation theory and management practice and provides a mechanism for measuring their success.