Tolerance of marine calanoid resting eggs: Effects of freezing,desiccation and Rotenone exposure - a field and laboratory study

Tolerance of calanoid resting eggs from bottom sediment in a manipulated marine enclosure (Svartatjønn, western Norway) to freezing, desiccation and exposure to the insecticide Rotenone was examined in 1989 and 1990, both in situ and in the laboratory. Egg abundances in the sediment were compared before and after draining followed by Rotenone treatment. The drained parts of the basin were exposed to both drying and freezing. A significant decrease in hatching success was found in the drained parts during the study (p<0.05,t-test) and in the deepest parts, which were exposed to Rotenone. No significant difference was found in an intermediate zone around the new water level established by the draining. Both drying (at 20°C) and freezing (at –15°C) caused total mortality of the eggs in laboratory experiments. Laboratory experiments also showed that Rotenone concentrations higher than 0.5 ppm resulted in significantly reduced hatching rates, indicating that resting eggs of calanoids tolerate 20 to 100 times higher Rotenone concentrations than do later ontogenetic stages. The operational procedure (i.e. draining and Rotenone treatment) employed in enclosed ponds used for marine fish fry production will, within a 1-yr cycle, reduce the abundance of resting eggs and therefore the potential for self-recruitment of the zooplankton stocks.     

Maximization of foraging efficiency and resource defense by group retrieval in the ant Formica schaufussi

Summary Workers of the ant Formica schaufussi forage as individuals and cooperate in groups to retrieve arthropod prey. In 2 sample years, group-transported prey were on average 6.8 and 4.7 times heavier than individually retrieved items, and the average loading ratios of groups were greater than the loading ratios of single foragers. Retrieval group size was adjusted to prey size, and prey transport velocity for individuals and groups tended to decrease with increasing prey weight. The efficiency of individual and group retrieval, estimated from calculations of the prey delivery rate to the nest (PDR) achieved by each foraging mode, varied as a function of prey size. Individual retrieval maximized PDR at a prey weight of 19.5 mg, and group transport maximized PDR at 190 mg. Although the PDR maxima of an individual in a group and a solitary forager were approximately equal, depending on prey size, group transport may maximize foraging efficiency. Group transport also decreased interference competition from sympatric ant species. Group-transported prey having a greater likelihood of successful retrieval were within the size range of prey that maximized foraging efficiency. Transport group size appeared to be more important in prey defense than in increasing prey transport velocity, suggesting an important role of group size in competitive ability.Offprint requests to: J.F.A. Traniello     

The influence of rainfall on the distribution and abundance of the school prawn Metapenaeus macleayi in the Hunter River region (Australia)

The effects of rainfall on the distribution and abundance of Metapenaeus macleayi in the Hunter River region (Australia) were examined as part of a study of the prawn fishery and biology in this region. A marked increase in the freshwater flow into the estuary of the Hunter River enhances the seasonal seaward movement of prawns and produces an initial increase in the abundance of adults in the adjacent oceanic waters; it is suggested that the disturbance to the estuarine sediments and to the prawns' normal burrowing and respiratory activity, as a result of the increased river flow, is responsible for this pronounced emigration. This initial increase in adult abundance enhances the prawns' reproductive potential, and the heavy rainfall indirectly assists the recruitment of young to the cotuary and their growth and survival, and thereby increases prawn abundance in the following year also. Prolonged dry weather adversely affects the prawns, and usually results in a smaller population. The annual fluctuations and absence of a downward trend in the catch statistics indicate that this stock has not been overfished.     

Specific features and origin of the Caspian Sea diatom flora

The systematic composition of the diatom flora of the Caspian Sea is original, but poor, especially in marine species. At present, 286 species, varieties and forms, belonging to 46 genera and 4 orders are known to exist in the Caspian Sea. Of this number, 77 species and varieties (27%) are planktonic and 209 (63%) benthonic. The phytoplankton of the Caspian Sea is wholly neritic. In regard to salinity, a characteristic of the Caspian diatom flora is that it is composed of three different groups: marine, brackish, and fresh-water species. The brackish water group is of great interest, as it includes many diatoms which are known only from this water body (endemisms). The poor species-composition of the diatom flora is accounted for by variations in the hydrogical conditions of the Caspian Sea in the geological past. The formation of the flora is based on such sources as the ancient flora remains of the Upper-Tertiary Caspian-Black Sea, the younger elements of the Pliocene Sea during its isolation period, and the immigrants entering the Caspian Sea during the short period of its communication with the Black Sea.     

Respiratory quotient and ammonia excretion in Tilapia mossambica

Tilapia mossambica (Peters), acclimated to and tested in fresh water at 30°C, maintained a routine respiratory quotient (R Q) of about unity and an ammonia quotient (A Q) (Vol. NH₂/Vol. O₂) of about 0.2 at high ambient oxygen concentrations. At low oxygen concentrations (below 2 ppm) R Q and A Q increased sharply to values of 8 and 1, respectively (at 0.6 ppm), indicating a close relationship of increase in anaerobic energy utilization and increase in protein metabolism at inadequate oxygen concentrations. T. mossambica (8 cm), exercised continuously with intervening sampling and flushing stops for 6 h, at a swimming speed of about 2 body lengths/sec, derived some anaerobic energy throughout the exercise (R Q: 1.2), utilizing more protein the longer the exercise. The coupling of the increased protein metabolism and anaerobic energy utilization may be of advantage in preventing acidosis and also in conserving sodium (Na⁺) in fish.Part of this work was included in a paper presented at the Centennial Meeting of The American Fisheries Society, September 13–16, 1970, New York.     

Environmental factors affecting the standing crop of foraminifera in sublittoral and psammolittoral communities of a Long Island salt marsh

Representative samples from the epiphytic and psammolittoral communities were made during the summer of 1968 in North Sea Harbor, Southampton, Long Island, USA. In the epiphytic communities, the foraminifera were very patchy; 2.6% of the total samples accounted for 56.4% of the total foraminifera collected. The standing crop and species composition of the foraminifera changed throughout the summer. Two seasonal peaks were observed in the epiphytes. In early summer Protelphidium tisburyensis was the dominant form. In late July and August Elphidium incertum was dominant. Taken as a whole over the entire summer, the following species comprised the epiphytic foraminiferan community: Elphidium incertum (46.63%); Protelphidium tisburyensis (25.64%); Ammotium salsum (9.88%); Elphidium clavatum (6.74%); E. translucens (3.47%); Ammonia beccarii (2.83%); Ammobaculites dilatatus (2.08%); Trochammina inflata (1.8%); Elphidium advenum (< 1%); E. galvestonense (< 1%); E. gunteri (< 1%); Quinqueloculina lata (< 1%); Q. seminulum (< 1%) and Trochammina macrescens (< 1%). Although fewer species were found, many more foraminifera live in the benthos than in the epiphytic community. Taken as a whole, over the entire summer, the following species comprised the foraminifera in the psammolittoral community: Trochammina inflata (49.6%); Elphidium incertum (31.8%); Ammotium salsum (10.9%); Quinqueloculina seminulum (4.2%); Elphidium sp. (1.5); Protelphidium tisburyensis (0.9%); Ammonia beccarii (0.7%); Elphidium clavatum (< 0.1%); and E. translucens (< 0.1%). Three species, Ammotium salsum, Elphidium incertum and Trochammina inflata bloomed successively in the psammolittoral community. The distribution of the latter two species was correlated with the vertical and horizontal changes of grain size; Elphidium incertum distribution clustered around a median grain size of 0.1 mm, whereas Trochammina inflata clustered around a median grain size of 0.46 mm. The sediments were sampled both at high and low tide. No evidence was obtained to suggest migration of foraminifera through the sediments as a function of tidal cycle. Horizontal distribution of the foraminifera in the marsh was correlated with the flow patterns of very small rivulets in the study area. With respect to many species of foraminifera, the overlying epiphytic communities are not continuous with the psammolittoral communities below them in the water column. Protelphidium tisburyensis was an early summer dominant epiphyte, but was rare in the psammolittoral communities. Trochammina inflata, on the other hand, was dominant in the coarser, deeper sediments and was rare in the epiphytic community. Elphidium incertum is presumably a generalist species. It formed half the foraminiferan population throughout the water column. Ammotium salsum was also abundant in both communities.Supported by US AEC Contract AT (30-1) 3995. Ref. No. NYO 3995-16.Summarized from a thesis submitted by N. J. Matera in partial fulfillment of the requirements of Master of Arts at The City College of New York.University Institute of Oceanography of CUNY, Contribution No. 1.     

Species Imperilment and Spatial Patterns of Development in the United States

Abstract:  Conservation biologists and others hypothesize that humankind's "ecological footprint" is affected not only by the sheer intensity of human activity but also by its spatial arrangement. We used a multivariate statistical model and state-level data to evaluate correlations between species imperilment and the level and spatial distribution of human settlement and infrastructure development in the United States. The level of human activity—measured by the number of people and households, incidence of roads, and intensity of nighttime lights—was significantly correlated with the ecological imperilment of species. Our regression models consistently showed that a 1% increase in the level of human activity across the United States was associated with about a 0.25% increase in the proportion of plant and animal species considered at risk of extinction by The Nature Conservancy. The distribution of human activity did not affect species imperilment. Our results point to rising levels of human activity—and not some particular (e.g., sprawling) distribution of human activity—as the most relevant anthropogenic factor explaining biodiversity loss in the United States.     

Patch Mosaic Burning for Biodiversity Conservation: a Critique of the Pyrodiversity Paradigm

Abstract:  Fire management is increasingly focusing on introducing heterogeneity in burning patterns under the assumption that "pyrodiversity begets biodiversity." This concept has been formalized as patch mosaic burning (PMB), in which fire is manipulated to create a mosaic of patches representative of a range of fire histories to generate heterogeneity across space and time. Although PMB is an intuitively appealing concept, it has received little critical analysis. Thus we examined ecosystems where PMB has received the most attention and has been the most extensively implemented: tropical and subtropical savannas of Australia and Africa. We identified serious shortcomings of PMB: the ecological significance of different burning patterns remains unknown and details of desired fire mosaics remain unspecified. This has led to fire-management plans based on pyrodiversity rhetoric that lacks substance in terms of operational guidelines and capacity for meaningful evaluation. We also suggest that not all fire patterns are ecologically meaningful: this seems particularly true for the highly fire-prone savannas of Australia and South Africa. We argue that biodiversity-needs-pyrodiversity advocacy needs to be replaced with a more critical consideration of the levels of pyrodiversity needed for biodiversity and greater attention to operational guidelines for its implementation.