Effects of mercury on the feeding behavior of the mummichog, Fundulus heteroclitus from a polluted habitat

Fish living in contaminated environments may exhibit reduced growth which may be due, in part, to the impact of toxicants on prey capture ability. We studied the effects of methylmercury (meHg) and mercuric chloride (Hg) on feeding of Fundulus heteroclitus from Piles Creek, a polluted habitat in Linden, New Jersey. We found that exposure to 0·01 mg/liter of meHg for one week had less impact on the prey capture rate than exposure to a similar concentration of Hg. Exposure to 0·01 mg/liter for two weeks or to 0·02 mg/liter for one week, of either meHg or Hg, produced significant reductions in feeding rate, compared to controls. In general, the fish were affected to a greater degree by exposure to Hg than to meHg. This is the reverse of the usual order of toxicity, but is in keeping with previous observations on this population, in which we have noted that gametes and embryos had developed tolerance to meHg, but were more susceptible to Hg.     

Composition,export and faunal utilization of drift vegetation in the salt river submarine canyon

Submarine canyons may be particularly important in the transport process of drift seagrasses and seaweeds from highly productive shallow lagoon areas to deeper water. We studied the composition, export, and faunal utilization of shallow, nearshore benthic vegetation as it was transported to offshore areas via the Salt River submarine canyon on the island of St Croix, U.S. Virgin Islands. The study was conducted using a saturation diving system (NULS-1: Hydrolab) during two missions in April and August, 1980. Using bottom drifters deployed in Salt River Bay and the submarine canyon, we recorded net benthic current flow up to 2 cm s^?1 moving out of the lagoon and down the canyon to deeper water. Using bottom nets set up at the canyon head and at the 29 m isobar, and from transect surveys and drift clump samples, we determined drift plant export rates and drift clump biomass and species composition. The dominant drift plants were Thalassia testudinum and Syringodium filiforme and algae in the genera Dictyota, Dictyopterus, and Diloplus. During the second mission, the seagrass Halophila decipiens became more abundant, both in the drift and in large patches along the canyon floor. In both missions, more drift was collected in the nets during high wind conditions than during calmer days. Calculated turnover times ranged from 0·01 to 4·4 days for algae in the order Dictyotales and 4·4 to 18 days for Thalassia blades. Total exported biomass of drift vegetation varied between 1·4 to 65·1 kg wet wt day^?1. Samples of drift vegetation contained mostly juvenile forms of both invertebrates and fishes, but in relatively low numbers. Faunal numbers were most strongly related to rate of drift movement.     

What has Corruption Got to do with it? Understanding the Persistence of Rural-Urban and Inter-Regional Inequalities in Ghana and Zimbabwe

Inequalities are no respecter of countries, including the affluent ones. Nevertheless, these problems appear to prevail more in the developing countries, which have the dubious distinction of having the highest degrees of inequalities in the world. Inequalities exist between urban and rural areas, as well as between the various regions. This paper discusses inequalities in Ghana and Zimbabwe, emphasizing the rural–urban dichotomy. Using data from the Ghana Demographic and Health Surveys (GDHS) and the Zimbabwe Demographic and Health Surveys (ZDHS) conducted by the respective statistical authorities of both countries and Macro International, the paper analyses existing inequalities in both countries. The paper also attempts to elucidate and understand the causes. It concludes that the traditional explanation of disparities that attribute the conditions to aberrations in the operations of market forces, while having some validity, may not provide a full explanation for Ghana and Zimbabwe’s predicament. It argues that whilst the existing disparities may be rooted in history, their persistence and worsening in the post-independence era could only be understood with reference to the corruption, nepotism and the mismanagement that have characterized these states since they gained their independence.     

Palaeovelocity: A parsimonious proposal

Using data collected in her field studies, Maizels (1983) compared five methods of calculating palaeovelocity from coarse gravel deposits. Her paper indicated that the five methods provide estimates which differ by up to 2 x. There are several errors in the published equations, however. Upon correction, the smallest estimate is within 3% per cent of the largest. Other published data sets suggest that the distinction among a variety of palaeovelocity equations is not worth pursuing in light of the amount of scatter in typical data. This paper recommends use of the Thompson and Campbell (1979) modification of the basic Keulegan flow resistance equation because it fits the data as well as any other, whilst covering a more comprehensive range of flow conditions. Problems of appropriate roughness length and entrainmnet function remain.     

Crossing boundaries: Interdisciplinarity in the context of urban environments

Drawing upon the discussions and insights provided by researchers and policy-makers during a seminar series, this paper explores the rationales for, and the practices and difficulties of, interdisciplinarity. The urban environment provides the problem context. Despite a consistent rhetoric and repeated attempts to promote interdisciplinary research, not least by the funding councils in response to policy imperatives, success appears to have been limited. The paper suggests that rather than viewing interdisciplinarity as a distinct, often difficult, category of research it is more useful to consider a continuum of research types from multi- to transdisciplinarity. The paper furthers the interdisciplinarity debate by characterising five categories of ‘border troubles’. These involve the relentless association of interdisciplinarity with ‘real world problems’, the epistemological structuring of disciplines, assumptions about the disciplinary division of labour and the privileging of certain frames and forms of enquiry, the increasing complexity of knowledge transfer, and the ‘hard wiring’ of the research funding and assessment system. However, we conclude optimistically in terms of the evident willingness of researchers to occupy hazardous disciplinary border zones to further urban environmental understanding and propose a set of ‘conditions for success’ encompassing both the approach and practices of participants in interdisciplinary work as well as operational and contextual factors.