Benthic invertebrate assemblages of Delaware Bay

During two consecutive summers, the first quantitative bay-wide survey (207 stations) of benthic invertebrates was conducted in Delaware Bay (USA). In 1972, 109 species were collected at 105 stations; and in 1973, 125 species were collected at 102 stations. A total of 169 different species were collected for both summers. The number of species and number of individuals increased with increasing salinity and increasing median grain size. These relationships were compared and were found similar to those in estuaries and bays throughout the world. Average density was 722 individuals m², which is low compared to other estuaries. The relationship of low secondary production to pollution, macroscopic algae, sediment transport, predation, and hydrography is discussed. Deposit feeders comparised the major feeding type. Local species composition was similar to that in Chesapeake Bay, and dominant species occurred in estuaries throughout the Mid-Atlantic Bight. The benthic invertebrates of Delaware Bay were related to the cosmopolitan mode of estuarine faunas. Faunal assemblages were identified by cluster analysis. The assemblages were associated with sediment type and salinity. It was concluded that Delaware Bay comprises a mosaic of animal assemblages, some of which have relatively sharp boundaries similar to classical level bottom type communities, whereas the boundaries of others are almost impossible to detect, and these represent species distributed along an environmental continum.     

Geographic Range Fragmentation and Abundance in Neotropical Migratory Birds

Populations of neotropical migrant landbirds have experienced significant declines in recent years. We investigated potential consequences of these declines by examining the relationship between abundance and fragmentation of geographic ranges of species on the North American breeding grounds. We estimated areograpbic fragmentation using the box dimension of a species' geographic range and demographic fragmentation using the fractal dimension of the semivariance function calculated from samples of population abundance across species' geographic ranges. We found a negative relationship between average abundance and demographic fragmentation for neotropical migrants, but not for residents. We also showed that demographic fragmentation and areographic fragmentation are inversely related for residents, but not for neotropical migrants. These results imply that neotropical migrants may be more sensitive to extinction than are residents.     

Individual differences in the mechanisms underlying the onset and maintenance of paternal behavior and the inhibition of infanticide in the monogamous biparental California mouse,Peromyscus californicus

Virgin male Peromyscus californicus tend to behave infanticidally or nonparentally towards pups, whereas virtually all males exhibit parental behavior following birth of their own young. Most males (65–75%) living with their pregnant partner attacked or ignored unfamiliar pups and did not become parental (behave parentally) prior to birth of their young. However, a significant minority of males (34%) living with their partner became parental after just 24 h of postcopulatory cohabitation with the female and remained parental throughout their mate's pregnancy. Males that were infanticidal before the birth of their young became parental only after their young were born. The presence of the mother was necessary for the postpartum maintenance of paternal behavior and the inhibition of infanticide in males that were infanticidal prepartum. In contrast, males that were paternal prior to birth of their young continued to be paternal after birth, even in the absence of postpartum contact with the mother. Thus, different mechanisms are involved in the inhibition of infanticide and the onset and maintenance of paternal behavior. Correspondence to: D.J. Gubernick     

Size-dependent mating and gender choice in a simultaneous hermaphrodite, Bulla gouldiana

Simultaneous hermaphrodites are predicted to optimally divide resources between male and female function, which can result in both size-dependent mating behaviors and conflict between potential mates. Predicted strategies include size-assortative mating, conditional exchange of gametes, and mating patterns where relative size affects investment in each sexual role. This study investigated the effect of body size on the mating strategies of a hermaphroditic opisthobranch, Bulla gouldiana. Although individuals were spatially aggregated in the field with high levels of movement and size variation, there was little evidence for predictions. Laboratory experiments, however, revealed complicated effects of mass on the probability and duration of mating, as well as gender choice. Pairs were more likely to mate if they included at least one large animal, with the larger animal typically inseminating the smaller. When both individuals were large, they were more likely to each mate in both sexual roles by switching roles once. Although B. gouldiana did not usually alternate between sexual roles multiple times within mating events, paired individuals behaved similarly (neither or both mating as sperm donors) more often than expected by chance. This suggests some level of reciprocity, which is unlikely to be conditional given rates of unilateral mating. When the larger member of the mating pair inseminated the smaller, the duration of insemination increased with the size of the smaller sperm recipient. Copulations lasted longer in pairs that switched sexual roles than in those that did not switch roles. This study suggests that variation in body size can lead to size-dependent mating patterns, but only some of the patterns in B. gouldiana support theoretical predictions. We review other studies that have addressed similar issues, providing inconsistent mating patterns in sperm-storing hermaphrodites.     

A Bayesian network approach to modelling land-use decisions under environmental policy incentives in the Brazilian Amazon

ABSTRACT

Deforestation driven by agricultural expansion is a major threat to the biodiversity of the Amazon Basin. Modelling how deforestation responds to environmental policy implementation has thus become a policy relevant scientific undertaking. However, empirical parameterization of land-use/cover change (LUCC) models is challenging due to the high complexity and uncertainty of land-use decisions. Bayesian Network (BN) modelling provides an effective framework to integrate various data sources including expert knowledge. In this study, we integrate remote sensing products with data from farm-household surveys and a decision game to model LUCC at the BR-163, in Brazil. Our ‘business as usual’ scenario indicates cumulative forest cover loss in the study region of 8,000 km² between 2014 and 2030, whereas ‘intensified law-enforcement’ would reduce cumulative deforestation to 1,600 km² over the same time interval. Our findings underline the importance of conservation law enforcement in modulating the impact of agricultural market incentives on land cover change.     

Mosaicism for trisomy 12: Four cases with varying outcomes

Trisomy 12 observed in chorionic villus sampling (CVS) may reflect generalized mosaicism or indicate mosaicism confined to only the placenta. In this report, four cases of trisomy 12 observed in CVS or cultured placental biopsies with varying outcomes are presented. Seven dinucleotide repeat polymorphisms for chromosome 12 were used to determine the chromosome 12 origins in the fetus or child and to delineate the mechanism(s) that gave rise to the trisomy. In two cases (cases A and C), the mosaicism was confined to the placenta, resulting in normal liveborns. Although, in one case, the molecular results suggested an apparent duplication of one paternal chromosome 12 in the placenta, normal biparental inheritance was found in the diploid fetal cell line in both cases. In two other cases (cases B and D), trisomy 12 was observed in both extraembryonic and fetal tissues. In one of these pregnancies, a child was born by Caesarean section at 37 weeks because of intrauterine growth retardation and oligohydramnios, and resulted in neonatal death. Molecular markers and fluorescence in situ hybridization (FISH) revealed low-level trisomy 12 mosaicism in the spleen. In the fourth case, fetal abnormalities were detected on ultrasound and low-level trisomy 12 mosaicism was observed in amniotic fluid cells using conventional cytogenetics and FISH. Molecular markers revealed a maternal meiosis I non-disjunction of chromosome 12 in DNA from a cultured placental biopsy. Although predicting the outcomes of pregnancies involving confined placental mosaicism remains difficult, molecular techniques are valuable tools for distinguishing uniparental from biparental disomy and mechanisms of mosaicism.     

Investigation of real-life operating patterns of wood-burning appliances using stack temperature data

ABSTRACT

A study was undertaken to identify patterns of consumer use of outdoor wood boilers or outdoor wood furnaces (technically referred to as outdoor wood-fired hydronic heaters (OWHHs)) and indoor wood stoves (IWSs) to inform the development of performance testing protocols that reflect real-life operating conditions. These devices are manually fed, and their usage protocols are a function of a number of variables, including user habits, household characteristics, and environmental factors. In this study, researchers logged the stack wall temperatures of 4 OWHH and 20 IWS units in the states of New York and Washington over two heating seasons. Stack wall temperature is an indicator of changes in combustion modes. Two algorithms were developed to identify usage modes and cold and warm start refueling events from the stack wall temperature time series. A linear correlation analysis was conducted to evaluate the effect of heat demand on usage patterns. The results and methods presented here will inform the cataloging of typical operational patterns of OWHHs and IWSs as a step in the development of performance testing procedures that represent actual in-home usage patterns.

Implications: Current US regulatory programs for residential wood heating use a certification program to assess emissions and efficiency performance. Testing under this program uses a test that burns 100% of a single, standardized wood fuel charge to assess performance at different steady-state load conditions. This study assessed in-field operational patterns to determine if the current certification approach accurately characterized typical homeowner use patterns. The data from this study can be used to inform revisions to testing methods to increase certification test comparability between lab and field performance.     

Recovery from acidification in European surface waters: a view to the future

There is now overwhelming documentation of large-scale chemical recovery from surface water acidification in Europe, but to date there has been little documentation of biological recovery. Modelling studies based on current emission reduction plans in Europe indicate that there will be further chemical recovery. The uncertainties in these scenarios mainly relate to the future behavior of nitrogen in the ecosystem and the effects of climate change. Four major climate-related confounding factors that may influence the chemical and biological recovery process are: i) increased frequency and severity of sea-salt episodes; ii) increased frequency and severity of drought; iii) increased turnover of organic carbon; iv) increased mineralization of nitrogen. International cooperative work to abate acidification has so far been very successful, but there is still a long way to go, and many potential setbacks. It is essential that future development of water chemistry and aquatic biota in acidified waterbodies continue to be monitored in relation to further emission reductions of S and N and future effects of climate change.     

Evidence for destruction of PCBs by the OH radical in urban atmospheres

Evidence for reaction of polychlorinated biphenyl (PCB) congeners with the hydroxyl (OH) radical in the troposphere was observed in diurnal variations in ambient gas-phase PCB concentrations at three urban sampling sites located in the Chicago, IL; Baltimore, MD; and Jersey City, NJ urban/industrial areas. The magnitude of the depletion of individual PCB congeners decreased by about 10-20% for each additional chlorine substituent, reflecting slower reaction rates for higher MW congeners with the OH radical. Octa- and nonachlorobiphenyls, which are largely unreactive with the OH radical, were used as tracers to investigate the effects of dilution on diurnal variation. The environmental rate constants for disappearance of the PCBs range from about 1.0 day(-1) for trichlorobiphenyls to about 0.3 day(-1) for hexachlorobiphenyls. Assuming a OH radical concentration of 3 x 10(6) molecules cm (-3), the second-order rate constants for reaction of specific congeners with the OH radical are consistent with laboratory measurements. More importantly, the relative reactivity of PCB homologues agrees well with the relationship predicted by other researchers from laboratory measurements, suggesting that losses of PCBs during daytime tropospheric transport are due at least in part to reactions with the OH radical.