Hot Spots and Hot Moments in Riparian Zones: Potential for Improved Water Quality Management1

Vidon, Philippe, Craig Allan, Douglas Burns, Tim P. Duval, Noel Gurwick, Shreeram Inamdar, Richard Lowrance, Judy Okay, Durelle Scott, and Steve Sebestyen, 2010. Hot Spots and Hot Moments in Riparian Zones: Potential for Improved Water Quality Management. Journal of the American Water Resources Association (JAWRA) 46(2):278-298. DOI: 10.1111/j.1752-1688.2010.00420.x Abstract: Biogeochemical and hydrological processes in riparian zones regulate contaminant movement to receiving waters and often mitigate the impact of upland sources of contaminants on water quality. These heterogeneous processes have recently been conceptualized as “hot spots and moments” of retention, degradation, or production. Nevertheless, studies investigating the importance of hot phenomena (spots and moments) in riparian zones have thus far largely focused on nitrogen (N) despite compelling evidence that a variety of elements, chemicals, and particulate contaminant cycles are subject to the influence of both biogeochemical and transport hot spots and moments. In addition to N, this review summarizes current knowledge for phosphorus, organic matter, pesticides, and mercury across riparian zones, identifies variables controlling the occurrence and magnitude of hot phenomena in riparian zones for these contaminants, and discusses the implications for riparian zone management of recognizing the importance of hot phenomena in annual solute budgets at the watershed scale. Examples are presented to show that biogeochemical process-driven hot spots and moments occur along the stream/riparian zone/upland interface for a wide variety of constituents. A basic understanding of the possible co-occurrence of hot spots and moments for a variety of contaminants in riparian systems will increase our understanding of the influence of riparian zones on water quality and guide management strategies to enhance nutrient or pollutant removal at the landscape scale.     

Global distribution of a key trophic guild contrasts with common latitudinal diversity patterns

Most hypotheses explaining the general gradient of higher diversity toward the equator are implicit or explicit about greater species packing in the tropics. However, global patterns of diversity within guilds, including trophic guilds (i.e., groups of organisms that use similar food resources), are poorly known. We explored global diversity patterns of a key trophic guild in stream ecosystems, the detritivore shredders. This was motivated by the fundamental ecological role of shredders as decomposers of leaf litter and by some records pointing to low shredder diversity and abundance in the tropics, which contrasts with diversity patterns of most major taxa for which broad-scale latitudinal patterns haven been examined. Given this evidence, we hypothesized that shredders are more abundant and diverse in temperate than in tropical streams, and that this pattern is related to the higher temperatures and lower availability of high-quality leaf litter in the tropics. Our comprehensive global survey (129 stream sites from 14 regions on six continents) corroborated the expected latitudinal pattern and showed that shredder distribution (abundance, diversity and assemblage composition) was explained by a combination of factors, including water temperature (some taxa were restricted to cool waters) and biogeography (some taxa were more diverse in particular biogeographic realms). In contrast to our hypothesis, shredder diversity was unrelated to leaf toughness, but it was inversely related to litter diversity. Our findings markedly contrast with global trends of diversity for most taxa, and with the general rule of higher consumer diversity at higher levels of resource diversity. Moreover, they highlight the emerging role of temperature in understanding global patterns of diversity, which is of great relevance in the face of projected global warming.     

Prenatal diagnosis of occipital encephalocele,mega-cisterna magna,mesomelic shortening,and clubfeet associated with pure tetrasomy 20p

We present the first case of a fetus with pure tetrasomy 20p proven by cord-blood sampling at 24 weeks of gestation. This case was diagnosed in utero with multiple congenital anomalies including occipital encephalocele, mega-cisterna magna, mesomelic shortening, and clubfeet. An analysis of GTG-banded chromosomes of 20 metaphase cells was performed. Female karyotype [47,XX, +i(20)(p10)] was revealed in all cells. Pure tetrasomy 20p was confirmed using fluorescent in situ hybridization (FISH) with a telomere probe for chromosome 20p in all seven metaphase cells. The pregnancy was terminated because of associated multiple anomalies and severe oligohydramnios. The postmortem examination confirmed the prenatal diagnosis. Copyright © 2003 John Wiley & Sons, Ltd.     

A major increase in snake pipefish (<Emphasis Type="Italic">Entelurus aequoreus</Emphasis>) in northern European seas since 2003: potential implications for seabird breeding success

Since the early 2000s routine fish surveys have recorded increasing numbers of snake pipefish, Entelurus aequoreus, in the northeast Atlantic. Fishermen and divers have also commented on this increase and pipefish have started to appear in the diet of seabirds and other marine predators. This paper collates information from these diverse sources and assesses the current status of snake pipefish. We found compelling evidence of a dramatic increase in the abundance of snake pipefish starting around 2003 and continuing up to the present (2006) and a range expansion northwards to Spitzbergen and the Barents Sea. Since 2004 snake pipefish have been increasingly recorded in the diet of many species of seabird breeding in colonies around the coast of the UK, and in Norway, Iceland and the Faeroe Islands. Information on the nutrient value of snake pipefish is currently lacking but their rigid, bony structure makes them difficult for young seabirds to swallow and there are numerous records of chicks choking to death. Thus, in the case of avian predators during the breeding season, it appears unlikely that increased abundance of snake pipefish will provide a useful alternative prey. The reason for the rapid and dramatic increase in numbers of snake pipefish is currently unclear but such events are characteristic of marine ecosystems and will almost certainly have an effect on food web dynamics.     

Use of Nutshells as Fillers in Polymer Composites

Nutshells are agricultural waste products that can be procured at relatively low cost. In this work we examined the possibility of using these biodegradable materials as fillers in poly(lactic acid) and low density polyethylene. The nutshells were ground into powder, blended with the polymer, and then injection molded with final weight varying from 10 to 40 weight %. The mechanical and thermal properties of the composites were then studied. In general, the addition of fillers caused reductions in mechanical properties to varying extents, but thermal properties were only slightly affected. The use of maleic anhydride and peroxide with the fillers had a negative effect on poly(lactic acid) but a slightly positive effect on the stiffness of polyethylene. The results suggested that polymer-nutshell composites may be usable in applications where cost is a concern and where some reductions in mechanical properties are acceptable.     

The Contribution of Headwater Streams to Biodiversity in River Networks1

Abstract: The diversity of life in headwater streams (intermittent, first and second order) contributes to the biodiversity of a river system and its riparian network. Small streams differ widely in physical, chemical, and biotic attributes, thus providing habitats for a range of unique species. Headwater species include permanent residents as well as migrants that travel to headwaters at particular seasons or life stages. Movement by migrants links headwaters with downstream and terrestrial ecosystems, as do exports such as emerging and drifting insects. We review the diversity of taxa dependent on headwaters. Exemplifying this diversity are three unmapped headwaters that support over 290 taxa. Even intermittent streams may support rich and distinctive biological communities, in part because of the predictability of dry periods. The influence of headwaters on downstream systems emerges from their attributes that meet unique habitat requirements of residents and migrants by: offering a refuge from temperature and flow extremes, competitors, predators, and introduced species; serving as a source of colonists; providing spawning sites and rearing areas; being a rich source of food; and creating migration corridors throughout the landscape. Degradation and loss of headwaters and their connectivity to ecosystems downstream threaten the biological integrity of entire river networks.     

Book reviews

Green Culture: environmental rhetoric in contemporary America. C. G. Herndl & S. C. Brown (Eds), 1996, Madison, WI, University of Wisconsin Press, 315 pp. ISBN 0 229 14990 0, £35.95 (hbk) ISBN 0 299 14994 3, £17.50 (pbk)

Earthtalk: communication empowerment for environmental action. S. A. Muir & T. L. Veenendall, 1996, Westport, CT, Praeger, Praeger Series in Political Communication, 233 pp. ISBN 0 275 953700 X, £47.95

Environmentalism and Cultural Theory. Kay Milton, 1996 London & New York, Routledge, 266 pp. ISBN 0 415 115529 9, £45.00 (hbk) ISBN 0 415 11530 2, £13.99 (pbk)

Local Environmental Struggles: citizen activism in the treadmill of production. Kenneth A. Gould, Allan Schnaiberg & Adam S. Weinberg, 1996, Cambridge University Press, 239 pp. ISBN 0 521 55519 1, £40.00 (hbk) ISBN 0 521 55521 3, £14.95 (pbk)

The Language of Environment: a new rhetoric. George Myerson & Yvonne Rydin, 1996 London, UCL Press, 264 pp. ISBN 1 85728 330 9, £35.00 (hbk) ISBN 1 85728 331 7, £11.95 (pbk)

Environmental Issues and Business: implications of a changing agenda. Sally Eden, 1996, Chichester, Wiley, ISBN 0 471 94872 1, £25.00

Green Shift: towards a green sensibility in architecture. John Farmer, edited by Kenneth Richardson, 1996, Oxford, Butterworth Architecture, with World-Wide Fund for Nature, ISBN 07506 15303

Lewis Mumford and the Ecological Region: the politics of planning. Mark Luccarelli, 1995, New York, Guilford Press, ISBN 1572300019, £19.95

The Ecology of Hope: communities collaborate for sustainability. Ted Bernard & Jora Young, 1997, East Haven, CT, New Society Publishers, 233 pp. ISBN 0 86571 355 33 (pbk)

Turning the Tide: integrated local area management for Australia's coastal zone. Valerie A. Brown, 1995, Canberra, Australia, Department of the Environment, Sport and Territories

Involving Communities in Forestry through Community Participation. Forestry Practice Guide 10, Forestry Commission

The Scope for Community Participation in Forest Management. A Report for the Forestry Commission and Scottish Office by Bill Slee, Gill Clark & Patrick Snowdon, £10 (£15 non UK)

The Role of Woodlands in Meeting Planning Objectives in Great Britain. A Report for the Forestry Commission by Professor Paul Selman