Relationships between primary productivity and bottom‐water oxygenation off northwest Africa during the last deglaciation

The upwelling region off northwest Africa is one of the most productive regions in the world ocean. This study details the response of surface‐ and deep‐water environments off Mauritania, northwest Africa, to the rapid climate events of the last deglaciation, especially the Bølling–Allerød (15.5–13.5 ka BP) and Younger Dryas (13.5–11.5 ka BP). A high accumulation rate gravity core GeoB7926‐2, recovered at ～20° N, 18° W, was analysed for the grain size distribution of the terrigenous sediment fraction, the organic carbon content, diatom and benthic foraminifera communities. Humid conditions were observed during the Bølling–Allerød with a high contribution of fluvial sediment input. During the Younger Dryas intensified trade winds caused a larger sediment input of aeolian dust from the Sahara and more intense upwelling with higher primary productivity, as indicated by high diatom concentrations. The abrupt and large increase of organic matter caused low oxygen conditions at the sea floor, reflected by the poor benthic foraminiferal fauna and the dominance of the low‐oxygen‐tolerant foraminiferal species Bulimina exilis. This is surprising since low‐oxygen conditions have not been recorded during modern times at the sea floor in this region, despite present‐day intensive upwelling and high primary productivity. After the Younger Dryas, more humid conditions returned, diatom abundance decreased and B. exilis was replaced by typical deep‐sea species as found in the region today, indicating the return of more oxygenated conditions at the sea floor. Copyright © 2011 John Wiley & Sons, Ltd.     

Digging by badgers and rabbits on some wooded slopes in Belgium

Eight forest areas, totalling 128.7 hectares, located near the northern border area of the Belgian Ardennes, have been surveyed for soil material brought to the surface by burrowing animals. It appeared that at least 7003.6 kg/ha were present, brought up by badgers and rabbits. The amount turned out to vary a factor 10³ between the eight regions. During the half year survey period badgers added some 570 kg to their mounds. On this basis the rate of mass transport effected directly by badgers may be estimated at an insignificant 0.02 gcm^?1 y^?1. Also, production of available sediment by these animals is relatively unimportant in this temperate humid forest environment.     

The Decline of the North Sea Whelk (Buccinum undatum L.) Between 1970 and 1990: A Natural or a Human-Induced Event?

Abstract. Recent surveys in the southern and central North Sea and the Dutch Wadden Sea revealed that the whelk Buccinun undarum L. can no longer be found in areas where whelks were abundant twenty or more years ago.
The decline of whelk populations tends to coincide with areas of various, intense human activities, which may cause either pollution or physical damage. Potential causes for the decline of whelks from the southern North Sea and coastal areas are discussed and considered in view of North Sea ecology and protective policies for the North Sea.