Succession of physical and chemical conditions and of crustacean communities in some small, man made water bodies

We studied physical and chemical conditions and the crustacean communities in temporary ponds in a military area in South Germany. All ponds were form ed by driving of tanks. They were turbid, without higher aquatic plants but contained a unique crustacean community with endangered species such as th e anostracan Branchipus schaefferi, the copepods Cyclops furcifer and Metac yclops minutus and the cladocerans Daphnia obtusa, Moina brachiata and Macr othrix hirsuticornis. Branchipus was only present in ponds which dried out and where driving occurred. Ponds which did not dry out and where driving e vents were rare or did not take place were devoid of Branchipus. Physical a nd chemical conditions were similar in ponds with and without Branchipus. D ay-night fluctuations of temperature were up to 15 degrees C in summer. Con ductivity was 200-300 mu S cm(-1), hardness ranged between 2 and 3.5 meq l( -1), alcalinity between 1 and 3 meq l(-1), pH between 7.5 and 9, dissolved phosphorus was <20 mu g l(-1), concentration of nitrogen was <0.1 mg l(-1) and oxygen saturation was >60% in the ponds except one pond where concentra tions of nutrients and conductivity were somewhat higher. When driving of t anks had been stopped the number and size of the ponds decreased and their character changed. Branchipus schaefferi and other endangered species disap peared and more but common, benthic species such as the cladoceran Chydorus sphaericus and the copepods Megacyclops viridis and Eucyclops serrulatus g ained importance. Branchipus schaefferi is now close to extinction. Conduct ivity, hardness, alcalinity increased while pH decreased probably because a lgae were replaced by marsh plants. We conclude that driving of tanks raise d clay particles, prevented the growth of higher aquatic vegetation and con densed the bottom sediments. All this was necessary to keep the ponds in an early stage of succession thus providing conditions necessary to maintain Branchipus.