Bioturbation

Bioturbation is the ransacking and mixing ( Turbation ) from soils or sediments by living organisms. It belongs to the Translokationsprozessen. Since soils from rock basically differ in that they are busy, the bioturbation is primarily a research field of pedology. Bioturbate structures, however, are preserved in rocks and often play an important role in the reconstruction of past depositional environments in geology and paleontology.

In the terrestrial area of ​​the biogenic soil mixing procure primarily soil animals such as small mammals (eg mole ), worms (eg earthworm ) or insects. In aquatic ( subhydrischen ) area of the sediments or soils subhydrischen these are mainly worms (eg lugworm ), mussels, sea urchins, sea cucumbers, etc. In the first place, there is an increase of recent processes of pedogenesis, ie the formation of soils with consequences be mapped in geological dimension. In addition to the bioturbation Hydro- ( Pelo ), cryo- and Kultoturbation to the pedogenic mixing processes would provide for.

Importance for soil formation ( pedogenesis )

Bioturbation plays an important role in soil formation, in the development of black earth even a decisive one. In particular, the physical properties ( the aggregate structure) are they positively affected because the burrowing Edaphon (soil burrowers ) contributes creating through its tubes grave activity to a loosening of the soil, sometimes promotes the formation of a voided crumb structure, in the special case pronounced earthworm activity a worm solution structure creates. The loosening of the soil can also contribute to a better ventilation of the surface soil (if the soil material is deposited on the surface, see molehills ) and counteract the accumulation of water. However, the drainage effect is likely to be classified as secondary, since many of the animal transitions end blindly. However, positive effects are yet to prove (increasing the water capacity) for clayey soils.

Finally, through the processes of bioturbation for computing the limits of soil horizons by " blurring " that for a washed- nutrients such as lime are fed back into the subsoil, as well as humus- free underbody material is transported upward, and on the other the upper humus soil deepening and homogenization experiences. Especially those representatives of Edaphons that hunt in the soil ( moles ) or live ( Geophagen such as earthworms ), an especially important factor for soil rearrangement in ( mole and earthworm up to 12 kg per m² and year).

The importance of bioturbation in the case of black soils is due to the fact that the small mammals involved in pedogenesis (here, hamster, ground squirrel and prairie dog ) are driven by the winter cold and summer drought for vertical migration and thereby bring about a profound humus accumulation ( think was about the storehouses of the hamster ), which ultimately causes the powerful, characteristic dark brown to black Ah horizon. The humus-rich soil material will be transported in the aisles, which are called Krotowinen down and saved from complete mineralization. This in turn transported over from the ground up material agitators in turn acts against the decalcification.

Since mainly the fine soil material is homogenized, hardly be transported along with a mixture of organic and mineral matter, and larger soil particles such as stones and gravel, the bioturbation, in certain cases, the formation of stone soles in the subsoil - and to a certain extent segregation - favor.

Consistent with its role in land reallocation and its kind of grave terminate influence on soil structure ( = structure) can be the one involved in the bioturbation macro - and megafauna categorize into different groups. Accordingly, moles, beetles and mole crickets were the blade graves, ants and termites mouth graves, hamster, ground squirrel and prairie dog scratching the graves as well as earthworms and snakes assign the Bohrgräbern. Other differentiation are possible.

When bioturbation soil and sediment components are shifted to a not inconsiderable extent. Sediments can be resolved layering. In the bottom can also hydrophobic, highly sorptive contaminants (eg, PCBs, dioxins ) that are fixed by the atmospheric deposition actually in the top soil horizon, reach deeper soil zones.

Bioturbation of Benthals

Also in the bottoms of waters ( benthic ) bioturbation plays an essential role. It is here also to the degradation processes of organic material that falls to the floor as detritus and is embedded in the sediment. A relaxation of the sediment and thus a better supply of oxygen is the most important aspect. In addition to influence the species composition and diversity of benthos and thus the food chain, there are many fish at their peak.

Bioturbation is accomplished mainly in the sea by different groups of worms, especially from the class of polychaetes, but in addition also of shells, which play a further role in the exchange of material as filter feeders. Also in the bottom grave crustaceans such as shrimp Monoporeia affinis ( in places, 10,000 to 20,000 individuals per square meter in the Baltic Sea) or decapods from the family of Callianassiden ( responsible for fossil grave transitions of Thalassinoides - Ophiomorpha - form group) may be of importance for bioturbation of Benthals.

Geological aspects

In sedimentary rocks can be frequently found fossil traces of bioturbation and interpret. Sedimentary rocks with strong traces of fossil bioturbation indicate an oxygen-rich, life- friendly environment, while finely layered sediments with no signs of bioturbation provide evidence of a hostile to life, oxygen-poor or - free environment. Under certain conditions, remain evidence obtained in rocks on bioturbation in the form of trace fossils ( Ichnofossils ), such as residential buildings, Fraßbauten, traces of life ( crawler lanes, quiet lanes) or grazing traces.