ALBERT

Description: Climate change has significant implications for biodiversity and ecosystems. With slow progress towards reducing greenhouse gas emissions, climate engineering (or ‘geoengineering’) is receiving increasing attention for its potential to limit anthropogenic climate change and its damaging effects. Proposed techniques, such as ocean fertilization for carbon dioxide removal or stratospheric sulfate injections to reduce incoming solar radiation, would significantly alter atmospheric, terrestrial and marine environments, yet potential side-effects of their implementation for ecosystems and biodiversity have received little attention. A literature review was carried out to identify details of the potential ecological effects of climate engineering techniques. A group of biodiversity and environmental change researchers then employed a modified Delphi expert consultation technique to evaluate this evidence and prioritize the effects based on the relative importance of, and scientific understanding about, their biodiversity and ecosystem consequences. The key issues and knowledge gaps are used to shape a discussion of the biodiversity and ecosystem implications of climate engineering, including novel climatic conditions, alterations to marine systems and substantial terrestrial habitat change. This review highlights several current research priorities in which the climate engineering context is crucial to consider, as well as identifying some novel topics for ecological investigation.

Description: The surface chemistry of aquatic organisms determines their biotic interactions. Metabolites in the spatially limited laminar boundary layer mediate processes, such as antifouling, allelopathy and chemical defense against herbivores. However, very few methods are available for the investigation of such surface metabolites. An approach is described in which surfaces are extracted by means of C18 solid phase material. By powdering wet algal surfaces with this material, organic compounds are adsorbed and can be easily recovered for subsequent liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS) investigations. The method is robust, picks up metabolites of a broad polarity range and is easy to handle. It is more universal compared to established solvent dipping protocols and it does not cause damage to the test organisms. A protocol is introduced for the macroalgae Fucus vesiculosus, Caulerpa taxifolia and Gracilaria vermiculophylla, but it can be easily transferred to other aquatic organisms.

Description: Experimental studies linking community composition to functioning are typically confined to small and closed micro- or mesocosms. Such restricted conditions may affect both species’ biology and their environment. Yet, targeting simple features in the behaviour of species may circumvent these constraints. Focusing on ecological functions provided by dung beetles, we test whether large, open-top cages – MESOCLOSURES – will intercept the flight trajectories of beetles, thereby allowing manipulation of local community composition. MESOCLOSURES were built in both tropical forest (Brazil) and temperate grasslands (Finland), thus testing their general efficiency. Within the respective environments, we varied different aspects of MESOCLOSURE design: in the tropical forest, we examined the impact of MESOCLOSURE dimensions on exclusion efficiency, whereas in the temperate grassland, we assessed the potential for selectively excluding and including community members by different mesh sizes. In the temperate environment, we also went from method to application, using MESOCLOSURES to relate community composition to functioning under two simulated grazing regimes. MESOCLOSURES allowed efficient manipulation of dung beetle communities, maintaining dung beetle densities at intended levels in both temperate and tropical systems. In the tropics, the smallest cages (1 × 1 m) offered the highest contrast in beetle densities inside vs. outside of the fence, whereas the largest cages (9 × 9 m) offered the lowest. Nonetheless, densities inside cages never exceed one-fifth of those outside. At the temperate site, manipulations of community structure through mesh size yielded significant differences in functioning and suggested an interaction between small dung-dwelling species and large tunnelling species. Within cages, higher grazing was reflected in augmented dung removal. We conclude that MESOCLOSURES can be effectively used to study dung beetle functions across habitats and latitudes. As applied insights, the present study adds resolution to the significance of different functional groups of dung beetles and shows that grazing pressure may have an important impact on the ecosystem functions that they provide. Overall, this study suggests that targeted manipulation of dispersal may offer new solutions for linking fauna to ecosystem functions with minimal impact on the processes measured.

Description: The Denmark Strait Overflow (DSO) contributes roughly half to the total volume transport of the Nordic overflows. The overflow increases its volume by entraining ambient water as it descends into the subpolar North Atlantic, feeding into the deep branch of the Atlantic Meridional Overturning Circulation. In June 2012, a multiplatform experiment was carried out in the DSO plume on the continental slope off Greenland (180 km downstream of the sill in Denmark Strait), to observe the variability associated with the entrainment of ambient waters into the DSO plume. In this study, we report on two high-dissipation events captured by an autonomous underwater vehicle (AUV) by horizontal profiling in the interfacial layer between the DSO plume and the ambient water. Strong dissipation of turbulent kinetic energy of O( math formula) W kg−1 was associated with enhanced small-scale temperature variance at wavelengths between 0.05 and 500 m as deduced from a fast-response thermistor. Isotherm displacement slope spectra reveal a wave number-dependence characteristic of turbulence in the inertial-convective subrange ( math formula) at wavelengths between 0.14 and 100 m. The first event captured by the AUV was transient, and occurred near the edge of a bottom-intensified energetic eddy. Our observations imply that both horizontal advection of warm water and vertical mixing of it into the plume are eddy-driven and go hand in hand in entraining ambient water into the DSO plume. The second event was found to be a stationary feature on the upstream side of a topographic elevation located in the plume pathway. Flow-topography interaction is suggested to drive the intense mixing at this site.

Description: Male secondary sexual traits are targets of inter- and/or intrasexual selection, but can vary due to a correlation with life-history traits or as by-product of adaptation to distinct environments. Trade-offs contributing to this variation may comprise conspicuousness towards conspecifics versus inconspicuousness towards predators, or between allocating resources into coloration versus the immune system. Here, we examine variation in expression of a carotenoid-based visual signal, anal-fin egg-spots, along a replicate environmental gradient in the haplochromine cichlid fish Astatotilapia burtoni. We quantified egg-spot number, area, and coloration; applied visual models to estimate the trait's conspicuousness when perceived against the surrounding tissue under natural conditions; and used the lymphocyte ratio as a measure for immune activity. We find that (i) males possess larger and more conspicuous egg-spots than females, which is likely explained by their function in sexual selection; (ii) riverine fish generally feature fewer but larger and/or more intensively colored egg-spots, which is probably to maintain signal efficiency in intraspecific interactions in long-wavelength shifted riverine light conditions; and (iii) egg-spot number and relative area correlate with immune defense, suggesting a trade-off in the allocation of carotenoids. Taken together, haplochromine egg-spots feature the potential to adapt to the respective underwater light environment, and are traded-off with investment into the immune system

Description: Different studies on the position of the non-indigenous species Neogobius melanostomus within the coastal food web of the Pomeranian Bay (western Baltic) were performed, resulting in a quantitative and qualitative species list of prey organisms found in the stomachs of the invader and an estimation concerning the importance of round goby as prey for different resident predators. It seems that the colonization process is not fully completed yet, but the results reveal that the species is already established in the food web 16 years after the first observation within the study area. The results show that N. melanostomus feed upon a wide range of different resident organisms. While a direct predation effect on native fish species appears rather unlikely, indirect effects such as competition cannot yet be excluded. In addition, our results reveal an ontogenetic diet shift and that the round goby itself already serves as an important prey for piscivorous fish and seabirds. Finally, we formulate different hypotheses based on our results which will require further research.

Description: The ocean's potential to export carbon to depth partly depends on the fraction of primary production (PP) sinking out of the euphotic zone (i.e., the e-ratio). Measurements of PP and export flux are often performed simultaneously in the field, although there is a temporal delay between those parameters. Thus, resulting e-ratio estimates often incorrectly assume an instantaneous downward export of PP to export flux. Evaluating results from four mesocosm studies, we find that peaks in organic matter sedimentation lag chlorophyll a peaks by 2 to 15 days. We discuss the implications of these time lags (TLs) for current e-ratio estimates and evaluate potential controls of TL. Our analysis reveals a strong correlation between TL and the duration of chlorophyll a buildup, indicating a dependency of TL on plankton food web dynamics. This study is one step further toward time-corrected e-ratio estimates

Description: International Ocean Discovery Program (IODP) Expedition 352 recovered a high-fidelity record of volcanism related to subduction initiation in the Bonin fore-arc. Two sites (U1440 and U1441) located in deep water nearer to the trench recovered basalts and related rocks; two sites (U1439 and U1442) located in shallower water further from the trench recovered boninites and related rocks. Drilling in both areas ended in dolerites inferred to be sheeted intrusive rocks. The basalts apparently erupted immediately after subduction initiation and have compositions similar to those of the most depleted basalts generated by rapid sea-floor spreading at mid-ocean ridges, with little or no slab input. Subsequent melting to generate boninites involved more depleted mantle and hotter and deeper subducted components as subduction progressed and volcanism migrated away from the trench. This volcanic sequence is akin to that recorded by many ophiolites, supporting a direct link between subduction initiation, fore-arc spreading, and ophiolite genesis.

Description: Nitrogen fixation — the reduction of dinitrogen (N2) gas to biologically available nitrogen (N) — is an important source of N for terrestrial and aquatic ecosystems. In terrestrial environments, N2-fixing symbioses involve multicellular plants, but in the marine environment these symbioses occur with unicellular planktonic algae. An unusual symbiosis between an uncultivated unicellular cyanobacterium (UCYN-A) and a haptophyte picoplankton alga was recently discovered in oligotrophic oceans. UCYN-A has a highly reduced genome, and exchanges fixed N for fixed carbon with its host. This symbiosis bears some resemblance to symbioses found in freshwater ecosystems. UCYN-A shares many core genes with the 'spheroid bodies' of Epithemia turgida and the endosymbionts of the amoeba Paulinella chromatophora. UCYN-A is widely distributed, and has diversified into a number of sublineages that could be ecotypes. Many questions remain regarding the physical and genetic mechanisms of the association, but UCYN-A is an intriguing model for contemplating the evolution of N2-fixing organelles.