Changes in the location of biodiversity–ecosystem function hot spots across the seafloor landscape with increasing sediment nutrient loading

Declining biodiversity and loss of ecosystem function threatens the ability of habitats to contribute ecosystem services. However, the form of the relationship between biodiversity and ecosystem function (BEF) and how relationships change with environmental change is poorly understood. This limits our ability to predict the consequences of biodiversity loss on ecosystem function, particularly in real-world marine ecosystems that are species rich, and where multiple ecosystem functions are represented by multiple indicators. We investigated spatial variation in BEF relationships across a 300 000 m2 intertidal sandflat by nesting experimental manipulations of sediment pore water nitrogen concentration into sites with contrasting macrobenthic community composition. Our results highlight the significance of many different elements of biodiversity associated with environmental characteristics, community structure, functional diversity, ecological traits or particular species (ecosystem engineers) to important functions of coastal marine sediments (benthic oxygen consumption, ammonium pore water concentrations and flux across the sediment–water interface). Using the BEF relationships developed from our experiment, we demonstrate patchiness across a landscape in functional performance and the potential for changes in the location of functional hot and cold spots with increasing nutrient loading that have important implications for mapping and predicating change in functionality and the concomitant delivery of ecosystem services

Disturbance of sandflats by thin deposits of terrigenous sediment: consequences for primary production and nutrient cycling.

The contributions of biodiversity to ecosystem functioning are increasingly recognized by ecologists, with biodiversity loss considered a significant threat to the maintenance of life-supporting ecosystem goods and services. Although ecologists have increased the amount of realism in biodiversity–ecosystem functioning (BEF) experiments, effects on functioning are rarely investigated in the field in conjunction with disturbances that affect biodiversity. Here, effects on functioning were investigated in situ following experimental disturbance of a realistic type and magnitude. Experimental deposits of terrigenous sediment (5 mm thickness) were applied at three intertidal sites in Whangapoua Harbour (Coromandel Peninsula, New Zealand), where soil erosion associated with logging is a serious problem. Experimental disturbance by terrigenous sediment impacted macrofaunal abundance and community composition (suspension and deposit feeders), and there were coincident shifts in ecosystem functioning at all three sites. Relative to controls, sediment-treated plots had higher rates of ammonium efflux (despite 50% fewer macrofaunal individuals) and lower rates of gross primary production and photosynthetic efficiency (despite similar sediment chlorophyll a concentrations). Judging from nutrient ratios in sediment pore water, microphyte primary producers living on the sediment surface in control plots were likely nitrogen limited (the normal situation for marine waters), whereas microphytes in sediment-treated plots were likely phosphate limited. Gross primary production and photosynthetic efficiency were significantly and positively correlated with ammonium uptake in control plots (r2 = 0.463 and 0.856, respectively) but not in treated plots (P > 0.05, r2 < 0.3). We suggest that the higher content of charged particles (clay) in the experimental deposits bound up phosphate, limiting its bio-availability, and shifted functional relationships between sandflat macrofauna and sediment primary productivity

Ecosystem functioning in a disturbance-recovery context: Contribution of macrofauna to primary production and nutrient release on intertidal sandflats

Aunque muchos ecólogos han descrito las relaciones entre la biodiversidad y el funcionamiento de los ecosistemas, los cambios en el funcionamiento después de una perturbación y durante la recuperación no están bien documentados. La teoría de la diversidad y el funcionamiento predice una disminución del funcionamiento con una menor diversidad (por ejemplo, después de una perturbación) y un aumento gradual del funcionamiento coincidente con la recuperación biótica. Probamos esta teoría empíricamente midiendo la producción primaria y la liberación de nutrientes (índices del funcionamiento de los bancos de arena) en tres sitios al inicio, la mitad y el final de un período de recuperación de un año. Aunque las reservas de microfitobentos (contenido de clorofila a en los sedimentos) se recuperaron rápidamente, las tasas de producción bruta de oxígeno fotosintético se redujeron en las parcelas perturbadas, en relación con los controles, en 7 de las 9 comparaciones. Las parcelas con una alta riqueza de macrofaunal tuvieron un mayor eflujo de amonio, y un mayor eflujo de amonio probablemente aumentó las tasas de producción primaria. El sitio con el mayor potencial de bioturbación, que estaba dominado por grandes bivalvos, exhibió la mayor disminución del funcionamiento inmediatamente después de la perturbación. Este sitio también tuvo las diferencias más persistentes entre el tratamiento y el control durante la recuperación, probablemente porque los bivalvos grandes permanecieron en baja abundancia en las parcelas tratadas durante todo el año del experimento

Macrofaunal Functional Diversity Provides Resilience to Nutrient Enrichment in Coastal Sediments

The degradation of ecosystems is often associated with losses of large organisms and the concomitant losses of the ecological functions they mediate. Conversely, the resilience of ecosystems to stress is strongly influenced by faunal communities and their impacts on processes. Denitrification in coastal sediments is a process that may provide ecosystem resilience to eutrophication by removing excess bioavailable nitrogen. Here, we conducted a large-scale field experiment to test the effect of macrofaunal community composition on denitrification in response to two levels of nutrient enrichment at 28 sites across a biologically heterogeneous sandflat. After 7 weeks of enrichment, we measured denitrification enzyme activity (DEA) along with benthic macrofaunal community composition and environmental variables. We normalised treatment site specific DEA values by those in ambient sediments (DEACN) to reveal the underlying response across the heterogeneous landscape. Nutrient enrichment caused reductions in DEACN as well as functional changes in the community; these were both more pronounced under the highest level of nutrient loading (on average DEACN was reduced by 34%). The degree of suppression of DEACN following moderate nitrogen loading was mitigated by a key bioturbating species, but following high nitrogen loading (which reduced the key species density) the abundance and diversity of other nutrient processing species were the most important factors alleviating negative effects. This study provides a prime example of the context-dependent role of biodiversity in maintaining ecosystem functioning, underlining that different elements of biodiversity can become important as stress levels increase. Our results emphasise that management and conservation strategies require a real-world understanding of the community attributes that facilitate nutrient processing and maintain resilience in coastal ecosystems

Nachweis genetischer Veraenderungen in repetitiven DNA Sequenzen in somatischen menschlichen Zellen nach Bestrahlung im niedrigen Dosisbereich

Bestimmung der Instabilitaet von Mikrosatelliten in Zellpopulationen nach Behandlung mit niedrigen Dosen ionisierender Strahlung und in strahlenassoziierten Schilddruesentumoren aus Weissrussland. (orig.)Determination of microsatellite instability in cells after low-dose irradiation, as well as in radiation-associated thyroid tumor in Belarus people.SIGLEAvailable from TIB Hannover: RO 3190(2002-606) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman