In situ nitrogen enrichment experiments in two Idaho (U.S.A.) streams

We conducted a series ofin situ experimental nutrient additions in two Idaho streams: Deep Creek, a desert stream located in Southeastern Idaho, and Big Wood River, situated in a mountainous region of Central Idaho. In both streams, a homogeneous reach was partitioned into almost identical channels. This allowed us to vary nutrient levels and measure algal response in experiments uncomplicated by differences in other factors.Ammonium nitrate was added to the treatment channels in Deep Creek. After nine days,Cladophora glomerata still predominated in both the control and treatment channels and algal biomass was not statistically different between the two. In the Big Wood River experiment significant differences in chlorophylla concentrations were not detected among three treatments of differing nitrogen enrichment and the control for both natural and artificial substrates. Also chlorophylla levels were not correlated with nitrogen concentrations, and the composition of algal communities remained similar among all treatments.We conclude that macronutrient enrichment of streams does not necessarily result in an increase in algal density or a change in algal community structure so long as other factors, which may limit the use of nutrients by algae, remain unaltered. Our results suggest that light, current velocity, and macroinvertebrate grazing may account for the failure of the periphyton to respond toin situ additions of nitrogen (and phosphorus) in our study streams.     

A comparative analysis of the psychosocial impacts of waste disposal facilities

This paper reports the results of a comparative analysis of the psychosocial impacts of municipal solid waste disposal facilities (both landfills and incinerators) in six communities in the provinces of Ontario and British Columbia, Canada. Telephone surveys were administered to random samples of residents living around each facility between 1990 and 1995 (total n=1203). The results of logistic regression analyses show that type of facility was the strongest predictor of residents' awareness, concern, and actions taken in response to site concerns. Essentially, residents living in close proximity to a landfill had a higher probability of reporting awareness, concern or actions than residents living around an incinerator site. There was little evidence of differences in reactions between Ontario and British Columbia (BC) residents, despite variations in provincial policies on waste disposal. The effects of other predictors, with the exception of involvement in the local community, were not consistent, supporting previous findings that the determinants of facility impacts are outcome‐specific. It is essential that environmental managers take this constellation of factors into account in the operation of existing, or siting of new, facilities.     

Abnormal gonadal morphology in intersex,<Emphasis Type="Italic"> Echinogammarus marinus</Emphasis> (Amphipoda): a possible cause of reduced fecundity?

Recent reports have demonstrated a cost associated with intersexuality in Amphipoda, including reduced fecundity and fertility. In this study, the gross morphology of the gonads in normal and intersex Echinogammarus marinus (Amphipoda) were compared to determine whether resource allocation to gonadal tissue accounted for this reduced fitness. Evidence for the presence of the male sex-determining hormone, androgenic gland hormone (AGH), was compared between sexual phenotypes using MALDI mass spectrometry. Two distinct intersex phenotypes (male intersex and female intersex) were found, with variation in gonadal structure corresponding with external phenotype. Examination of male intersexes revealed normal testicular development (testes, seminal vesicles and vas deferens), but also revealed the formation of an oviduct. Ovaries of intersex females showed normal ovarian development, but were reduced in length by approximately 20% due to the presence of vas deferens. The number of vas deferens in intersex females was equal to the number (one or two) of genital papillae. We hypothesise that the reduced ovarian length observed in intersex females is a likely cause of the reduced brood size previously reported in intersex females of this species. Variation in the sexual phenotype corresponded both to development of the androgenic gland and to expression of a peptide fragment corresponding to the A chain of androgenic gland hormone (AGH). Androgenic glands and a putative AGH peptide were present in males. However, in both normal and intersex females, the androgenic glands were only present in a rudiment form and the peptide was not detected. Intersex males were found to possess abnormal glands that appeared hypertrophied. However, AGH peptides were not detected, supporting the suggestion that the intersex phenotype is manifested via perturbations of AGH.An erratum to this article can be found at Communicated by J.P. Thorpe, Port Erin     

Extra-pair paternity in tree swallows: why do females mate with more than one male?

Recent studies of monogamous tree swallows (Tachycineta bicolor) suggest that females may receive some type of genetic benefit from extra-pair fertilizations. In this study we attempted to determine what type of genetic benefits might be gained by females. We compared numerous morphological and behavioral traits (Table 1) of every male nesting on one grid of nest-boxes (n = 23) to determine what male traits were correlated with male success at gaining extra-pair fertilizations. DNA fingerprinting revealed an increase in the level of extra-pair paternity from the previous year (50% of broods contained extra-pair young in 1990 vs. 87% of broods in 1991), but no significant correlates of paternity. We found six extra-pair fathers at seven nests (20 nests had extra-pair young). The traits of these extra-pair males did not differ from those of the males they cuckolded. We discuss several reasons for this lack of difference, but argue that our results are not inconsistent with females choosing extra-pair males to enhance the genotypic quality of their offspring. Despite a complete search of the nest-box grid for extra-pair fathers, we were able to explain the paternity of just 21% (13/63) of all extra-pair young. This suggests that extra-pair fathers were either residents off our study grid or non-territorial floaters. Tree swallows are quite mobile and spend only part of the day at their nest prior to laying. In addition, we rarely see swallows visiting other grids of nest-boxes. Therefore, we suggest that most extra-pair copulations occur at some unknown location, possibly at a feeding or roosting area where females may be able to choose from many more potential extra-pair fathers than at their nest-site.     

Modelling the spatial distribution of ammonia emissions from seabirds in the UK

Knowledge of the sources and distribution of ammonia (NH3) emissions underpins our understanding of the nitrogen budget. Research has focused on quantifying NH3 emissions from anthropogenic sources, whilst those from natural sources have received little attention internationally. Seabirds excrete large quantities of nitrogen, making seabird colonies a major natural source of NH3. Ammonia emissions from each UK seabird species were estimated and combined with population distribution data to model their spatial distribution. Total NH3 emissions from UK seabirds were estimated at 2.7 kt per year. Seabird emissions are concentrated in remote parts of the UK where anthropogenic emissions are small, so that seabirds often represent the main source of NH3 emissions in these areas. Seabird NH3 emissions were found to have increased by 34% since the 1970s. This corresponds to population changes which may be influenced by human activities, showing that even this natural source can be anthropogenically modified.     

REGIONAL RAINFALL INTENSITY-DURATION-FREQUENCY CURVES FOR PENNSYLVANIA1

ABSTRACT: A statistical analysis of all available continuous hourly and 15-minute duration rainfall records for Pennsylvania was performed to develop an updated procedure to estimate design storms. As a resuit of this study, Pennsylvania was divided into five homogeneous rainfall regions and a set of rainfall intensity-duration curves developed for each region, for return periods of 1 to 100 years and durations ranging from 5 minutes to 24 hours. The PDT-IDF curves were judged to be a better representation of Pennsylvania rainfall than the nationwide TP-40 maps, particularly for storm events of 10-years and lower return periods. The average time distribution of 24-hour storms in Pennsylvania was found to be well represented by the SCS Type II distribution. The Corps of Engineers SPS 24-hour distribution was found to differ appreciably from both the SCS Type H and the Pennsylvania 24-hour storm distribution. For storm durations between 15 and 90 minutes the standard Yarnell intensity-duration curves closely resemble Pennsylvania storm distributions.     

Development of a New Approach to Cumulative Effects Assessment: A Northern River Ecosystem Example

If sustainable development of Canadian waters is to be achieved, a realistic and manageable framework is required for assessing cumulative effects. The objective of this paper is to describe an approach for aquatic cumulative effects assessment that was developed under the Northern Rivers Ecosystem Initiative. The approach is based on a review of existing monitoring practices in Canada and the presence of existing thresholds for aquatic ecosystem health assessments. It suggests that a sustainable framework is possible for cumulative effects assessment of Canadian waters that would result in integration of national indicators of aquatic health, integration of national initiatives (e.g., water quality index, environmental effects monitoring), and provide an avenue where long-term monitoring programs could be integrated with baseline and follow-up monitoring conducted under the environmental assessment process.