The Role of ocean acidification in Emiliania huxleyi coccolith thinning in the Mediterranean Sea

Ocean acidification is a result of the uptake of anthropogenic CO₂ from the atmosphere into the ocean and has been identified as a major environmental and economic threat. The release of several thousands of petagrams of carbon over a few hundred years will have an overwhelming effect on surface ocean carbon reservoirs. The recorded and anticipated changes in seawater carbonate chemistry will presumably affect global oceanic carbonate production. Coccolithophores as the primary calcifying phytoplankton group, and especially Emiliania huxleyi as the most abundant species have shown a reduction of calcification at increased CO₂ concentrations for the majority of strains tested in culture experiments. A reduction of calcification is associated with a decrease in coccolith weight. However, the effect in monoclonal cultures is relatively small compared to the strong variability displayed in natural E. huxleyi communities, as these are a mix of genetically and sometimes morphologically distinct types. Average coccolith weight is likely influenced by the variability in seawater carbonate chemistry in different parts of the world's oceans and on glacial/interglacial time scales due to both physiological effects and morphotype selectivity. An effect of the ongoing ocean acidification on E. huxleyi calcification has so far not been documented in situ. Here, we analyze E. huxleyi coccolith weight from the NW Mediterranean Sea in a 12-year sediment trap series, and surface sediment and sediment core samples using an automated recognition and analyzing software. Our findings clearly show (1) a continuous decrease in the average coccolith weight of E. huxleyi from 1993 to 2005, reaching levels below pre-industrial (Holocene) and industrial (20th century) values recorded in the sedimentary record and (2) seasonal variability in coccolith weight that is linked to the coccolithophore productivity. The observed long-term decrease in coccolith weight is most likely a result of the changes in the surface ocean carbonate system. Our results provide the first indications of an in situ impact of ocean acidification on coccolithophore weight in a natural E. huxleyi population, even in the highly alkaline Mediterranean Sea

Capabilities and limitations of a new thermal finite volume model for the evaluation of laser-induced thermo-mechanical retinal damage

Many experimental studies focus on the physical damage mechanisms of short-term exposure to laser radiation. In the nanosecond (ns) pulse range, damage in the Retinal Pigment Epithelium (RPE) will most likely occur at threshold levels due to bubble formation at the surface of the absorbing melanosome. The energy uptake of the melanosomes is one key aspect in modeling the bubble formation and damage thresholds. This work presents a thermal finite volume model for the investigation of rising temperatures and the temperature distribution of irradiated melanosomes. The model takes the different geometries and thermal properties of melanosomes into account, such as the heat capacity and thermal conductivity of the heterogeneous absorbing melanosomes and the surrounding tissue. This is the first time the size and shape variations on the melanosomes‘ thermal behavior are considered. The calculations illustrate the effect of the geometry on the maximum surface temperature of the irradiated melanosome and the impact on the bubble formation threshold. A comparison between the calculated bubble formation thresholds and the RPE cell damage thresholds within a pulse range of 3 to 5000 ns leads to a mean deviation of = 22 mJ ∕ cm2 with a standard deviation of = 21 mJ ∕ cm2. The best results are achieved between the simulation and RPE cell damage thresholds for pulse durations close to the thermal confinement time of individual melanosomes

Exploring benthic biodiversity patterns and hotspots on European margin slopes

There is increasing evidence that continental slope ecosystems represent one of the major repositories of benthic marine biodiversity. The enhanced levels of biodiversity along slopes are hypothesized to be a source of biodiversity for continental shelves and deeper basins. Continental margins are increasingly altered by human activities, but the consequences of these anthropogenic impacts on benthic biodiversity and ecosystem functioning are almost completely unknown. Thus, there is an urgent need to gather sufficient information to enable us to understand patterns and drivers of deep sea biodiversity along continental margins. Although the local diversity of some deep open slope ecosystems is moderately well documented, very little is known about the biodiversity of these systems at greater spatial scales. Topographic setting, hydrodynamic forcing, and the biogeochemical characteristics of the deep-sea floor may play key roles in promoting and sustaining high biodiversity along the open slopes of continental margins. HERMES provided the opportunity to acquire a significant volume of information on the biodiversity, trophic conditions, and topographic characteristics of open slopes across European margins, increasing our knowledge of the latitudinal, longitudinal, and bathymetric patterns of benthic biodiversity, and extending our comprehension of the mechanisms driving deep-sea biodiversity and its potential loss. Improved knowledge of these processes is needed to inform policy decisions for promoting sustainable management of open slopes and deep-sea ecosystems along continental margins

Trophic state of benthic deep-sea ecosystems from two different continental margins off Iberia

The bioavailability of organic matter in benthic deep-sea ecosystems, commonly used to define their trophic state, can greatly influence key ecological processes such as biomass production and nutrient cycling. Here, we assess the trophic state of deep-sea sediments from open slopes and canyons of the Catalan (NW Mediterranean) and Portuguese (NE Atlantic) continental margins, offshore east and west Iberia, respectively, by using a biomimetic approach based on enzymatic digestion of protein and carbohydrate pools. Patterns of sediment trophic state were analyzed in relation to increasing water depth, including repeated samplings over a 3 yr period in the Catalan margin. Two out of the three sam- pling periods occurred a few months after dense shelf water cascading events. The benthic deep-sea ecosystems investi- gated in this study were characterized by high amounts of bioavailable organic matter when compared to other deep- sea sediments. Bioavailable organic matter and its nutritional value were significantly higher in the Portuguese margin than in the Catalan margin, thus reflecting differences in pri- mary productivity of surface waters reported for the two re- gions. Similarly, sediments of the Catalan margin were char- acterized by significantly higher food quantity and quality in spring, when the phytoplankton bloom occurs in surface wa- ters, than in summer and autumn. Differences in the benthic trophic state of canyons against open slopes were more ev- ident in the Portuguese than in the Catalan margin. In both continental margins, bioavailable organic C concentrations did not vary or increase with increasing water depth. Overall our findings suggest that the intensity of primary production processes along with the lateral transfer of organic particles, even amplified by episodic events, can have a role in controlling the quantity and distribution of bioavailable organic detritus and its nutritional value along these continental margin ecosystems

Hidromedusas profundas del Mediterráneo: Un estudio que incluye la descripción de dos nuevas especies recolectadas en cañones submarinos del Mediterráneo Occidental

Two new species of hydromedusae (Foersteria antoniae and Cunina simplex) are described from plankton collected in sediment traps placed in the Lacaze-Duthiers Submarine Canyon and along Banyuls-sur-Mer coast (northwestern Mediterranean). The Mediterranean hydromedusan deep-water fauna contains 41 species which represent 45.5 % of the world-wide deep-sea hydromedusae fauna (90) and 20% of the total number of Mediterranean hydromedusae (204). The Mediterranean deep-water hydromedusan fauna is characterised by a large percentage of holoplanktonic species (61%), mainly Trachymedusae. Nevertheless, contrary to the general opinion, the percentage of meroplanktonic species is equally high. The most original features of this fauna lies however in the importance of the number of endemic species (22%) and in the fact that the majority of them are meroplanktonic Leptomedusae with a supposed bathybenthic stage. Some of the endemic species could still represent relics of the primitive Tethys fauna having survived to the Messinian crisis. The origin of the Mediterranean deep-water hydromedusan fauna is discussed and a general hypothesis is proposed.Se describen dos especies nuevas a partir de ejemplares recolectados mediante trampas de sedimento del cañón submarino de Lacaze-Duthiers situado en frente de la costa de Banyuls-sur-Mer (Mediterráneo noroccidental). La fauna profunda de hydromedusas en el Mediterráneo contiene 41 especies que representan 45.5 % de la fauna mundial del grupo y el 20% de la fauna de hydromedusas del Mediterráneo. La fauna Mediterránea de hydromedusas profundas se caracteriza por un gran porcentaje de especies holoplanctónicas (61%), fundamentalmente Trachymedusas, sin embargo, contrario a la opinión generalizada, el porcentaje de especies meroplanctónicas es igualmente importante (39%). La característica más interesante de esta fauna es el número de especies endémicas (22%) y el hecho de que la mayoría de estas especies son meroplanctónicas (Leptomedusas) con una supuesta fase bentónica. Algunas de estas especies endémicas, podrían ser especies relictas (endémica insular) de la fauna primitiva del Tetis que sobrevivieron a la crisis Mesiniana. Se discute el origen de la fauna de hydromedusas profundas en el Mediterráneo y se presenta una nueva hipótesis

Major consequences of an intense dense shelf water cascading event on deep-sea benthic trophic condtions and meiofaunal biodiversity

Numerous submarine canyons around the world are preferential conduits for episodic dense shelf water cas- cading (DSWC), which quickly modifies physical and chem- ical ambient conditions while transporting large amounts of material towards the base of slope and basin. Observations conducted during the last 20 yr in the Lacaze-Duthiers and Cap de Creus canyons (Gulf of Lion, NW Mediterranean Sea) report several intense DSWC events. The effects of DSWC on deep-sea ecosystems are almost unknown. To in- vestigate the effects of these episodic events, we analysed changes in the meiofaunal biodiversity inside and outside the canyon. Sediment samples were collected at depths varying from ca. 1000 to >2100m in May 2004 (before a major event), April 2005 (during a major cascading event) and in October 2005, August 2006, April 2008 and April 2009 (af- ter a major event). We report here that the late winter–early spring 2005 cascading led to a reduction of the organic mat- ter contents in canyon floor sediments down to 1800 m depth, whereas surface sediments at about 2200 m depth showed an increase. Our findings suggest that the nutritional material re- moved from the shallower continental shelf, canyon floor and flanks, and also the adjacent open slope was rapidly trans- ported to the deep margin. During the cascading event the meiofaunal abundance and biodiversity in the studied deep- sea sediments were significantly lower than after the event. Benthic assemblages during the cascading were significantly different from those in all other sampling periods in both the canyon and deep margin. After only six months from the cessation of the cascading, benthic assemblages in the impacted sediments were again similar to those observed in other sampling periods, thus illustrating a quick recovery. Since the present climate change is expected to increase the intensity and frequency of these episodic events, we anticipate that they will increasingly affect benthic bathyal ecosys- tems, which may eventually challenge their resilience

Revision of an Optical Engineering Lecture Based on students\u27 Evaluation of University Teaching

This article describes the revision of a lecture in optical engineering based on an evaluation of university teaching by students. Although this evaluation method is widely accepted and investigated, only few practically oriented reports on the deduction of teaching improvements from the evaluation\u27s results on lectures are available. Our approach is the analysis of evaluation results by applying the principles of the explorative factor analysis (EFA). The changes that were derived from this analysis were mainly focused on a revision of the course structure and its presentation style.Finally, the impact of the modifications was measured by the evaluation of the lecture after the completed revision. The later evaluation showed improvements in all intended areas of interests illustrating the benefit of thorough revisions for the quality of teaching

Major consequences of an intense dense shelf water cascading event on deep-sea benthic trophic conditions and meiofaunal biodiversity

Numerous submarine canyons around the world are preferential conduits for episodic dense shelf water cascading (DSWC), which quickly modifies physical and chemical ambient conditions while transporting large amounts of material towards the base of slope and basin. Observations conducted during the last 20 yr in the Lacaze-Duthiers and Cap de Creus canyons (Gulf of Lion, NW Mediterranean Sea) report several intense DSWC events. The effects of DSWC on deep-sea ecosystems are almost unknown. To investigate the effects of these episodic events, we analysed changes in the meiofaunal biodiversity inside and outside the canyon. Sediment samples were collected at depths varying from ca. 1000 to > 2100 m in May 2004 (before a major event), April 2005 (during a major cascading event) and in October 2005, August 2006, April 2008 and April 2009 (after a major event). We report here that the late winter-early spring 2005 cascading led to a reduction of the organic matter contents in canyon floor sediments down to 1800 m depth, whereas surface sediments at about 2200 m depth showed an increase. Our findings suggest that the nutritional material removed from the shallower continental shelf, canyon floor and flanks, and also the adjacent open slope was rapidly transported to the deep margin. During the cascading event the meiofaunal abundance and biodiversity in the studied deep-sea sediments were significantly lower than after the event. Benthic assemblages during the cascading were significantly different from those in all other sampling periods in both the canyon and deep margin. After only six months from the cessation of the cascading, benthic assemblages in the impacted sediments were again similar to those observed in other sampling periods, thus illustrating a quick recovery. Since the present climate change is expected to increase the intensity and frequency of these episodic events, we anticipate that they will increasingly affect benthic bathyal ecosystems, which may eventually challenge their resilience

Control of Grain-Boundary Pinning in Al 2 O 3 /ZrO 2 Composites with Ce 3+ /Ce 4+ Doping

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65897/1/j.1151-2916.1992.tb04147.x.pd