Counts and abundance of macrozoobenthic organisms settled in artificial soft sediment at Brandal, Kongsfjorden, Spitsbergen

In the Arctic the currently observed rising air temperature results in more frequent calving of icebergs. The latter are derived from tidewater glaciers. Arctic macrozoobenthic soft-sediment communities are considerably disturbed by direct hits and sediment reallocation caused by iceberg scouring. With the aim to describe the primary succession of macrozoobenthic communities following these events, scientific divers installed 28 terracotta containers in the soft-sediment off Brandal (Kongsfjorden, Svalbard, Norway) at 20 m water depth in 2002. The containers were filled with a bentonite-sand-mixture resembling the natural sediment. Samples were taken annually between 2003 and 2007. A shift from pioneering species (e.g. Cumacea: Lamprops fuscatus) towards more specialized taxa, as well as from surface-detritivores towards subsurface-detritivores was observed. This is typical for an ecological succession following the facilitation and inhibition succession model. Similarity between experimental and non-manipulated communities from 2003 was significantly highest after three years of succession. In the following years similarity decreased, probably due to elevated temperatures, which prevented the fjord-system from freezing. Some organisms numerically important in the non-manipulated community (e.g., the polychaete Dipolydora quadrilobata) did not colonies the substrate during the experiment. This suggests that the community had not fully matured within the first three years. Later, the settlement was probably impeded by consequences of warming temperatures. This demonstrates the long-lasting effects of severe disturbances on Arctic macrozoobenthic communities. Furthermore, environmental changes, such as rising temperatures coupled with enhanced food availability due to an increasing frequency of ice-free days per year, may have a stronger effect on succession than exposure time.

Biological and environmental time series obtained from Point B, Bay of Villefranche

Ecological succession provides a widely accepted description of seasonal changes in phytoplankton and mesozooplankton assemblages in the natural environment, but concurrent changes in smaller (i.e. microbes) and larger (i.e. macroplankton) organisms are not included in the model because plankton ranging from bacteria to jellies are seldom sampled and analyzed simultaneously. Here we studied, for the first time in the aquatic literature, the succession of marine plankton in the whole-plankton assemblage that spanned 5 orders of magnitude in size from microbes to macroplankton predators (not including fish or fish larvae, for which no consistent data were available). Samples were collected in the northwestern Mediterranean Sea (Bay of Villefranche) weekly during 10 months. Simultaneously collected samples were analyzed by flow cytometry, inverse microscopy, FlowCam, and ZooScan. The whole-plankton assemblage underwent sharp reorganizations that corresponded to bottom-up events of vertical mixing in the water-column, and its development was top-down controlled by large gelatinous filter feeders and predators. Based on the results provided by our novel whole-plankton assemblage approach, we propose a new comprehensive conceptual model of the annual plankton succession (i.e. whole plankton model) characterized by both stepwise stacking of four broad trophic communities from early spring through summer, which is a new concept, and progressive replacement of ecological plankton categories within the different trophic communities, as recognised traditionally.

Selected soil properties and bacterial abundance in the glacier forefields 'Black Valley Transect' and 'Glacier Transect' on Larsemann Hills, East Antarctica

Antarctic glacier forefields are extreme environments and pioneer sites for ecological succession. Increasing temperatures due to global warming lead to enhanced deglaciation processes in cold-affected habitats, and new terrain is becoming exposed to soil formation and microbial colonization. However, only little is known about the impact of environmental changes on microbial communities and how they develop in connection to shifting habitat characteristics. In this study, using a combination of molecular and geochemical analysis, we determine the structure and development of bacterial communities depending on soil parameters in two different glacier forefields on Larsemann Hills, East Antarctica. Our results demonstrate that deglaciation-dependent habitat formation, resulting in a gradient in soil moisture, pH and conductivity, leads to an orderly bacterial succession for some groups, for example Cyanobacteria, Bacteroidetes and Deltaproteobacteria in a transect representing 'classical' glacier forefields. A variable bacterial distribution and different composed communities were revealed according to soil heterogeneity in a slightly 'matured' glacier forefield transect, where Gemmatimonadetes, Flavobacteria, Gamma- and Deltaproteobacteria occur depending on water availability and soil depth. Actinobacteria are dominant in both sites with dominance connected to certain trace elements in the glacier forefields.

(Table T1) Coral taxa and their ecological significance in ODP Site 194-1196 and Hole 194-1199A sediments

The Southern Marion Plateau (SMP) represents a vertical stacking of Miocene carbonate platform deposits. Two sites (1196 and 1199) were drilled on top of this plateau, penetrating a 663-m carbonate succession of bioclastic and reefal sedimentary bodies. The study focuses on the least dolomitized 410-m-thick upper part of the succession, which is middle to late Miocene in age. Sedimentological and paleontological studies were conducted at both sites in order to propose a paleoenvironmental model and its evolution through the Miocene age. Six main microfacies of possible environmental significance were defined using statistical multivariate analyses, based on the recognition and point counting of 24 biogenic components. Depositional environment reconstructions are proposed as well as the biosedimentary and the environmental evolution regarding seismic architectures, stratigraphy, biosedimentology, and microfacies analysis. The SMP platform mainly results from a vertical stacking of lens-shaped bodies in homoclinal to distally steepened ramp settings.

Succession of benthic hard-bottom communities in the shallow sublitoral of Comau Fjord, Chile

Succession was already studied over decades. The present thesis investigated the succession on hard substrate at two different study sites within the fjord Comau, Chile. Nine plates were installed at both sites (mouth of fjord and inner fjord) and photographed over three years. Additionally the natural community was recorded and a ground truthing was carried out to verify the analyzed species. Respectively at both sites over 50 different species were identified. Abundance data decreased with only one exception continuously, whereas the percentage cover increased. But the communities on the recruitment plates do still not reach the community structure of the natural environment. The present data showed that the hard-bottom succession in the fjord Comau is best described by the TOLERANCE MODEL (Connell & Slatyer, 1977). An important species of the natural community is the stony coral Desmophyllum dianthus, which normally (outside the fjord) grows beneath 1000 m water depth. The results of this work indicate that the mature community is not reached after 36 months.

Distribution of ostracoda in the lower Cretaceous succession of ODP Hole 80-549 (Figure 3)

Site 549 recovered a Lower Cretaceous succession which has been shown to include parts of the Barremian and Albian stages. Forty-four species of Ostracoda are illustrated and their stratigraphic distribution used to recognise three major facies units. An high diversity inner shelf facies earlier in the Barremian gives way to a low diversity, outer shelf facies, higher in the succession. The early Albian appears to indicate a return to an inner shelf fauna. The faunas recovered have been compared to similar faunas elsewhere in N. W. Europe.

Nannofossil assemblages and flux rates during the late Oligocene-early Miocene

This study investigates abundance variations in Noelaerhabdaceae assemblages during the late Oligocene-early Miocene at three subtropical sites in the Atlantic and Pacific oceans (DSDP Sites 516, 608 and 588). At these three sites, nannofossil assemblages were characterized by the successive high proportion of Cyclicargolithus, Dictyococcites and Reticulofenestra. Local paleoceanographic changes, such as the input of nutrient-poor water masses, might explain shifts in ecological prominence within the Noelaerhabdaceae at DSDP Site 516 (South Atlantic). But the similar timing of a decline in Cyclicargolithus at the three studied sites more likely corresponds to a global process. Here, we explore possible causes for this long-term taxonomic turnover. A global change in climate, associated with early Miocene glaciations, could have triggered a decline in fitness of the taxon Cyclicargolithus. The ecological niche made vacant because of the decrease in Cyclicargolithus could then have been exploited by Dictyococcites and Reticulofenestra that became prominent in the assemblages after 20.5 Ma. Alternatively, this global turnover might reflect a gradual evolutionary succession and be the result of other selection pressures, such as increased competition between Cyclicargolithus and Dictyococcites/Reticulofenestra. A diversification within Dictyococcites/Reticulofenestra, indicated by an expansion in the size variation within this group since ~ 20.5 Ma, may have contributed to the decreased fitness of Cyclicargolithus.

Ecological investigations in the wadden area off Borkum, East Frisian Islands, Germany

Die Bodentiergemeinschaft des Wattenmeeres ist von Frühjahr bis Herbst eines jeden Jahres durch extrem hohe Dichten von Jungtieren charakterisiert. Die Kenntnisse über die Ansiedlung von fplanktischen Larven im Wattenmeer, sowie die Dynamik postlarvaler Stadien sind aufgrund der üblicherweise verwendeten, großen Siebmaschenweiten gering. Gerade aber diesen Altersstadien kommt möglicherweise eine besondere Stellung im Energiefluß des Wattenmeeres zu. An 5 Stationen (von NWL bis HWL, B1-B5) im Rückseitenwatt der ostfriesischen Insel Borkum wurden 1986 Ansiedlung, räumliche Verteilung, Wachstum, Mortalität und Produktion der Altersklasse 0 von Macoma balthica, Mya arenaria und Cerastoderma edule untersucht. Um die Ansiedlung der planktotrophen Larven dieser Arten zu beschreiben, wurden ihre Dichten in Plankton und Bodenproben miteinander verglichen. Die Untersuchungen zur Dynamik der benthischen Stadien wurden mit zwei in der Probenfläche und der Siebmaschenweite unterschiedlichen Probenserien durchgeführt. Die Drift postlarvaler Stadien wurde durch bodennahe Planktonfänge innerhalb des Eulitorals nachgewiesen. Parallel zu den Untersuchungen an der Endofauna wurden das Vorkommen und die Größe epibenthischer Räuber im Untersuchungsgebiet erfaßt. Die Hauptansiedlung von M. balthica- und M. arenaria-Larven erfolgte nahezu gleichzeitig Ende Mai/Anfang Juni. Die meisten Larven beider Arten gingen an der prielnächsten (tiefsten) Station (B1) zum Bodenleben über, gefolgt von der nächst höher gelegenen Station B2. Während frühe Bodenstadien von M. arenaria nicht im oberen Bereich des Watts (B3,B4) gefunden wurden, ist eine geringfügige Erstansiedlung von M. balthica in diesem Gebiet nicht auszuschließen. Ein die Ansiedlung limitierender Einfluß der relativ dichten Mya arenaria-Siedlung an den Stationen B1 und B2 sowie der Alttiere von M. balthica konnte nicht festgestellt werden. Die Ähnlichkeit des Ansiedlungsprozesses bei beiden Arten, die sich im Zahlenverhältnis Larvenangebot zu Anzahl der ersten Bodenstadien widerspiegelt, kann ein Hinweis auf eine überwiegend passive Ansiedlung der Larven am Boden sein. Der Ort der Hauptansiedlung von C. edule wurde durch den Transekt nicht erfaßt. Die Station B2 war zwar durch ein Herzmuschelfeld charakterisiert, dieses war aber nach zwei Eiswintern nahezu vollständig eliminiert. Der Abundanz der planktischen Larven zufolge war der Hauptansiedlungszeitraum ebenfalls Ende Mai/Anfang Juni. Zu dieser Zeit wurden nur vereinzelt frühe Bodenstadien an den Stationen B1 und B2 gefunden, keine an den Stationen B3 und B4. Während die frühen postlarvalen Stadien von M. arenaria überwiegend am Ort der Ansiedlung blieben, verbreiteten sich die von M. balthica bis in den oberen Bereich des Untersuchungsgebietes (B3-B5). Analog zu der Besiedlung dieser Gebiete durch postlarvale M. balthica wurde die im Verlauf des Untersuchungsjahres stattfindende Kolonisierung der Station B1 durch C. edule ebenfalls postlarvalem Transport zugeschrieben. Demzufolge spielt bei beiden Muschelarten postlarvaler Transport eine wichtige Rolle bei der Besiedlung von Habitaten. Planktonfänge innerhalb der bodennahen Wasserschicht bestätigten, daß im Untersuchungsgebiet M. balthica die am stärksten verdriftende Muschelart war, gefolgt von C. edule. Mortalität, Wachstum, mittlere Biomasse, Produktion und P/B-Verhältnis wurden für M. balthica an den Stationen B1, B3 und B4 sowie für M. arenaria an der Station B1 bestimmt. Wachstum und damit auch Produktion beider Arten erwiesen sich hier - wie an den höher gelegen Stationen (nur M. balthica) - als durch größenselektiven Feinddruck beeinflußt. Der Effekt postlarvalen Transports auf Wachstum wird diskutiert. Übergreifend über die auf Artebene diskutierten Ergebnisse wird die Bedeutung der Dispersion postlarvaler Stadien und die Wirkung epibenthischen Feinddrucks im Wattenmeer erörtert. Der Vergleich postlarvalen Transportes mit der Dispersion planktischer Larvenstadien, der Dispersion von Meiofauna und der Mobilität adulter Stadien der Makrofauna verdeutlicht, daß es sich hierbei um eine Strategie handeln kann, innerhalb eines unvorhersagbaren Biotops freiwerdende Ressourcen zu nutzen und dadurch Konkurrenz zu vermeiden. Es wird die Hypothese aufgestellt, daß Initialansiedlung und Immigration einerseits sowie Feinddruck und Emigration andererseits einen Regelkreis darstellen, der in verschiedenen Teilbereichen des Watts mit unterschiedlicher Geschwindigkeit abläuft.