Phytoplankton production and growth rate in Lake Tanganyika: evidence of a decline in primary productivity in recent decades

1. This study focused on phytoplankton production in Lake Tanganyika. We provide new estimates of daily and annual primary production, as well as growth rates of phytoplankton, and we compare them with values published in former studies.
2. Chlorophyll- a (chl- a ) in the mixed layer ranged from 5 to 120 mg chl- a  m⁻² and varied significantly between rainy and dry seasons. Particulate organic carbon concentrations were significantly higher in the south basin (with 196 and 166 mg C m⁻³ in the dry and the rainy season, respectively) than in the north basin (112 and 109 mg C m⁻³, respectively).
3. Carbon : phosphorus (C : P) ratios varied according to season. Phosphorus limitation seemed to occur more frequently than nitrogen limitation, especially during the rainy season. Severe P deficiencies were rare.
4. Measured particulate daily primary production ranged from 110 to 1410 mg C m⁻² day⁻¹; seasonal contrasts were well marked in the north basin, but less in the south basin, where primary production peaks occurred also in the rainy season. Estimates of annual primary production, based on daily primary production calculated from chl- a and water transparency, gave values lower than those reported in previous studies. Picophytoplankton accounted on average for 56% of total particulate production in the south basin during the wet season of 2003.
5. Phytoplankton growth rates, calculated from primary production, ranged from 0.055 to 0.282 day⁻¹; these are lower than previously published values for Lake Tanganyika.     

Animal and vegetation patterns in natural and man-made bog pools: implications for restoration

1. Peatlands have suffered great losses following drainage for agriculture, forestry, urbanisation, or peat mining, near inhabited areas. We evaluated the faunal and vegetation patterns after restoration of a peatland formerly mined for peat. We assessed whether bog pools created during restoration are similar to natural bog pools in terms of water chemistry, vegetation structure and composition, as well as amphibian and arthropod occurrence patterns. 2. Both avian species richness and peatland vegetation cover at the site increased following restoration. Within bog pools, however, the vegetation composition differed between natural and man‐made pools. The cover of low shrubs, Sphagnum moss, submerged, emergent and floating vegetation in man‐made pools was lower than in natural pools, whereas pH was higher than in typical bog pools. Dominant plant species also differed between man‐made and natural pools. 3. Amphibian tadpoles, juveniles and adults occurred more often in man‐made pools than natural bog pools. Although some arthropods, including Coleoptera bog specialists, readily colonised the pools, their abundance was two to 26 times lower than in natural bog pools. Plant introduction in bog pools, at the stocking densities we applied, had no effect on the occurrence of most groups. 4. We conclude that our restoration efforts were partially successful. Peatland‐wide vegetation patterns following restoration mimicked those of natural peatlands, but 4 years were not sufficient for man‐made pools to fully emulate the characteristics of natural bog pools.     

Flight characteristics of birds:

This is the first part of a study on flight characteristics of birds and presents an annotated list of flight speeds of 139 western Palearctic species. All measurements were taken with the same tracking radar and corrected for wind influence according to radar-tracked wind-measuring balloons. Graphical presentation of the birds' air speeds emphasizes the wide variation of speeds within species and allows easy comparison between taxonomic groups, species, and types of flight. Unlike theoretical predictions, speeds increase only slightly with size. The larger species seem to be increasingly limited to speeds close to their speed of minimum power consumption V_mp',. Released birds, apparently reluctant to depart with migratory speed, fly at considerably lower speeds than migrating conspecifics. While large birds seem to be limited to speeds around V _mp', smaller birds seem to be capable of selecting between various speeds, approaching predicted V _mp, when tending to remain airborne at low cost, but flying at much higher speeds when tending to make best progress at low cost (around predicted speed of maximum range V _mr,). Predictions of air speeds by aerodynamic models proved to be too low for small birds because the models do not account for the gain in speed attained by the reduction in profile drag during bounding flight of small passerines. The models predict excessive speeds for large birds because the power output available for flight seems to decline much more with size than previously assumed.     

Invaders or endemics? Molecular phylogenetics,biogeography and systematics of Dreissena in the Balkans

1. Zebra mussels and their relatives (Dreissena spp.) have been well studied in eastern, central and western Europe as well as in North America, because of their invasiveness and economic importance. Much less is known about the biology and biogeography of indigenous (endemic) taxa of Dreissena, in the Balkans. A better knowledge of these taxa could help us (i) understand the factors triggering invasiveness in some taxa and (ii) identify other potentially invasive species. 2. Using a phylogenetic approach (2108 base pairs from three gene fragments), Dreissena spp. from natural lakes in the Balkans were studied to test whether invasive Dreissena populations occur in such lakes on the Balkan Peninsula, whether Dreissena stankovici really is endemic to the ancient Lakes Ohrid and Prespa, and to infer the phylogenetic and biogeographical relationships of Balkan dreissenids. 3. No invasive species of Dreissena, such as Dreissena polymorpha, were recorded. The supposedly ‘endemic’D. stankovici is not restricted to the ancient Lakes Ohrid and Prespa, but is the most widespread and dominant species in the west‐central Balkans. Its southern sister taxon, Dreissena blanci, occurs sympatrically with D. stankovici in Lakes Prespa, Mikri Prespa and Pamvotis. Both species are classified into the subgenus Dreissena (Carinodreissena) of which the subgenus Dreissena (Dreissena) (which includes the invasive D. polymorpha) is the sister taxon. Dreissena blanci and D. stankovici are considered to represent distinct species. 4. On a global scale, the two Balkan species have small ranges. An early Pliocene time frame for the divergence of the subgenera Carinodreissena and Dreissena is discussed, as well as potential colonization routes of the most recent common ancestor of Carinodreissena spp. 5. The ambiguous taxonomy of dreissenids in the Balkans is addressed. As nominal D. blanci presbensis from Lake Prespa has nomenclatural priority over D. stankovici, the correct name for the latter taxon should be Dreissena presbensis.     

Tuberculation in spatangoid fascioles: Delineating plausible homologies

The existing definition of spatangoid fascioles as a narrow band of minute tubercles (miliaries) is inadequate. One reason is that many intermediates between the presence of indisputable fascioles and their total absence are known. Although fascioles are widely used in the classification of spatangoids, diversity of fasciole tuberculation has largely been ignored. We examine fascioles in about 100 spatangoid species, focusing on the earliest manifestations of fascioles (both developmentally and phylogenetically) and on their variable tuberculation. Qualitative observations are complemented by quantitative analyses (ANOVA and PCA) of 21 species. Three types of fascioles are defined according to tubercle pattern: protofascioles for localized concentrations of miliaries; parafascioles for bands of miliaries with a progressive transition to the surrounding tuberculation; orthofascioles for strongly differentiated, well-circumscribed bands of miliaries. Ontogenetic, architectural, ecological, and taxonomic variations of these three patterns are qualitatively and quantitatively investigated. We attempt to delineate plausible homologies, origins, and subsequent evolution of the different kinds of fascioles.