Postfledging Dispersal of White-crowned Pigeons: Implications for Conservation of Deciduous Seasonal Forests in the Florida Keys

From 1988 to 1991, we studied the postfledging dispersal of 31 radio-tagged White-crowned Pigeons ( Columba leucocephala ) from three natal keys in Florida Bay. Immature birds dispersed from the natal keys at 26–45 days after batching, and most young dispersed more than 20 km during the first 10 days postdispersal. Dispersing birds flew either north to the Florida mainland or east to northeast to the mainline Florida Keys. On the mainland, immature birds fed nearly exclusively within Everglades National Park or an adjacent state wildlife management area. On the mainline keys, White-crowned Pigeons selectively used 5.01–20 ha forest fragments (p < 0.10) during the first 72 hours postdispersal. After this period, dispersing birds showed no preference among fragment size classes but used deciduous seasonal forests more frequently than suburban habitat(p < 0.10). The spatial pattern of dispersal on the mainline keys suggests that, during the first 72 hours postdispersal. White-crowned Pigeons are not able to reach northern Key Largo, where 69% of the deciduous seasonal forests are protected in state or federal ownership. Protection of large forest fragments, especially on southern Key Largo, should be a priority for maintaining populations of White-crowned Pigeons. These forests provide a series of "stepping stones" that enable dispersing immature White-crowned Pigeons to fly to more distant areas where habitat availability is less restricted. This species is threatened in Florida and may play an important role in maintaining plant species diversity in the seasonal deciduous forests of south Florida by dispersing seeds of at least 37 species of trees and shrubs. Protection of sufficient habitat to allow successful postfledging dispersal of this important seed disperser will also protect the ecosystem's biodiversity.     

Ammonia production and kinetic properties of glutamate dehydrogenase in the sipinculid Phascolosoma arcuatum exposed to anoxia

The amounts of total NH ₄ ⁺ detected in the external media in which Phascolosoma arcuatum had been exposed to various periods of anoxia were significantly greater than those in which the worms were exposed to normoxia for a similar period. The increased NH ₄ ⁺ production by P. arcuatum during anoxic exposure was unlikely to be due to an increased catabolism of adenine nucleotides or urea. In contrast, there were significant decreases in the concentrations of several free amino acids in the coelomic plasma and body tissues of individuals during the 48 h of anoxic exposure. The amount of NH ₄ ⁺ produced by the anoxic P. arcuatum could be accounted for by the decreases in the concentrations of aspartate or glycine. Increases in the catabolism of free amino acids (FAA), leading to the increased production of NH ₄ ⁺ , in P. arcuatum during anoxia were supported by the detection of significant changes in the kinetic properties of glutamate dehydrogenase (GDH), in the deaminating direction, from worms exposed to anoxia for 48 h. The apparent increase in the affinity of GDH from the anoxic worm to glutamate would bring about a greater deaminating activity at physiological concentrations of ths substrate. P. arcuatum used in these experiments were collected from the mangrove swamp at Mandai, Singapore between 1990 and 1993.     

The State of the Mammal Community of Boreal Forest Ecosystems in the Vicinity of a Nickel-Smelting Plant

The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact.     

OBSERVATIONS ON PHYTOPLANKTON PRODUCTIVITY IN RELATION TO HYDROGRAPHY IN THE NORTHERN ADRIATIC

This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997.     

Structure of a Mediterranean cryptobenthic fish community and its relationships with habitat characteristics

In the last 10 years, several studies have been carried out on the fish fauna of the Ustica Island marine reserve, yet no investigation was specifically addressed to the cryptobenthic fish assemblage. The first task of this study, conducted along the shallow rocky reefs of Ustica, was to determine the species composition, diversity and relative density of the resident cryptobenthic fishes. Furthermore, we aimed to assess the effects of some macro- and microscale habitat characteristics on the distribution pattern of fishes. In particular, the effect of predator density was indirectly evaluated by comparing density data collected within and outside the integral reserve zone. Overall, 20 species belonging to Blenniidae, Gobiidae, Tripterygiidae, Scorpaenidae and Gobiesocidae were recorded. Gobius bucchichi, Scorpaena maderensis, Tripterygion delaisi, T. melanurus and T. tripteronotus were the numerically dominant and most common species. The effects of zone (i.e. of predator density), bottom type and depth on species richness, diversity and evenness were not significant. A greater total fish density was observed on stones compared with rocky cliff and plateau, but only in the shallowest depth range. At level of single species, G. bucchichi was more abundant inside than outside the integral reserve, but only on stones and at 0–2 m depth range. Density of G. bucchichi was generally higher on stones than on rocky cliffs or plateau and between 0 and 5 m depth, although these differences were not always significant. T. delaisi was conversely more abundant in the deepest stratum (7–10 m). Canonical analyses demonstrated that bottom type and depth influenced significantly the fish assemblage structure. The observed differences in the assemblage structure relied mainly upon the dominant species. T. tripteronotus was mainly associated with rocky plateau and the intermediate depth range (3–5 m), whereas S. maderensis, T. melanurus and Lipophrys trigloides inhabited preferentially the rocky cliffs. At microscale level, the habitat choice of the investigated species was almost entirely based on whether the substrate was either vegetated or composed of bare rock. T. delaisi and T. tripteronotus were associated with substrata covered by algae, whilst G. bucchichi, S. maderensis and T. melanurus preferred bare rock bottoms. In some species, the electivity indices for the less abundant type of cover, measured at different spatial scale, changed accordingly. For instance, the smaller the size of the sampled area, the higher was the intensity of the association between G. bucchichi and Anemonia viridis.     

Toxicological Assessment of Wastewater and Runoff from the Baikal Pulp and Paper Mill

Russian Journal of Ecology -