Jens Tang Christensen

Life in Ballast Tanks

The abundance and diversity of species in ballast water, a recognised vector for the accidental introduction of nonindigenous organisms, has been examined through many studies around the world over the last 25 years. The results of European research activities are summarised in this contribution by outlining the objectives of some of these studies, and by focusing on the diversity of taxa determined from ballast water and tank sediment samples. In total 1508 samples (1219 ballast water, 289 tank sediment) were collected on 550 ships. A total of 990 taxa were identified during the 14 European shipping studies. The diversity of species found included bacteria, fungi, protozoans, algae, invertebrates of different life stages including resting stages, and fishes with a body length up to 15 cm. Crustacean, molluscan and polychaete invertebrates and algae form the majority of species found.

Effectiveness of odour repellents on red deer (Cervus elaphus) and roe deer (Capreolus capreolus): a field test

Chemical repellents are promoted as a method to reduce ungulate–vehicle collisions and ungulate browsing damages to agricultural and forestry resources. We tested the effectiveness of two odour repellents (Mota FL and Wolf Urine) on the foraging behaviour and area avoidance of free-ranging roe deer (Capreolus capreolus) and red deer (Cervus elaphus). The effects of the repellents were assessed by comparing deer visitation rates to sand arenas before and after application of repellents and visitation rates to control arenas. Neither of the tested products reduced deer visitation rates. Rapid habituation to olfactory stimuli and lack of sensitivity to predator odours may explain the ineffectiveness of the repellents to alter the behaviour of the deer. The results indicate that the tested products have no effects on roe deer and red deer behaviour and suggest that the effectiveness of the chemical area repellents as a measure to reduce deer–vehicle collision risk and browsing damages is questionable.

Late-Holocene salinity changes in Limfjorden, Denmark

Sub-fossil remains of macrofauna extracted from a 5.3 m sediment core in the central part of Limfjorden indicate marked changes in salinity. Sub-fossils in the lower part of the core indicate marine conditions similar to those of the present North Sea, while the upper 2 m of the core represents periods of brackish conditions alternating with periods of intermediate salinity similar to the present condition, indicative of alternating opening and closure of the fjord to the west. Precise 14 C dating of changes is hampered by variable marine reservoir effects and the addition of old carbonate from ground-water run-off. Salinity indications from dinoflagellate cyst assemblages from this core, but published elsewhere, are in accordance with those from macrofauna assemblages.

Polycyclic Aromatic Compounds in the Greenland Marine Environment

Information on levels of polycyclic aromatic compounds (PACs) in the marine environment from pristine areas of the world are still sparse. In this study, PACs were analyzed in sediments and various organisms from the area of Qeqertarsuaq/Disko in the western part of Greenland. PAC levels were measured in sediments, blue mussels ( Mytilus edulis ), liver of shorthorn sculpins ( Myoxocephalus scorpius ), and blubber of ringed seals ( Phoca hispida ). The average levels of PAC in the four sample types were 359 w g/kg, 497 w g/kg, 2762 w g/kg, and 101 w g/kg dry weight respectively. Principal component analyses (PCA) revealed variations in PAC composition between the different samples that could be related to molecular weight of the PAC compounds and lifestyle characteristics of the biota.