Method for determination of turgor pressure in macroalgae,with particular reference to the Phaeophyta

A procedure is described for the determination of the internal osmotic pressure and turgor pressure of marine macroalgae, for use in the laboratory and on the shore. A volume-related parameter (either thallus fresh weight, or area) is measured before and after transfer of plant material to a range of hyperosmotic solutions. Plotting the final fresh weight/area as a percentage of the initial value gives a biphasic curve, with an initial component of negative slope due to the change in thallus volume in less extreme hyperosmotic solutions, where the non-rigid thallus contracts in response to decreasing cell turgor pressure. The second component has a shallower slope and represents plasmolysis in more extreme hyperosmotic solutions, i.e., where turgor pressure is reduced to zero and the protoplast shrinks away from the cell wall; the extraprotoplast space created by plasmolysis will be filled with the external solution and thus no further changes in weight occur. These two components intersect at the lowest osmotic pressure at which cell turgor is zero. By correcting for any effects of the cell wall on thallus volume, the relationship can be used to calculate internal osmotic pressure and hence turgor pressure, assuming that the remaining change in thallus volume of the initial component is due entirely to variation in the intraprotoplast volume (approximately equivalent to the intraprotoplast water content, determined by subtraction of the extraprotoplast water and dry weight from the thallus fresh weight). Using this procedure, the turgor pressures of Fucus spiralis L., Ectocarpus siliculosus, (Dillw.) Lyngb. and Laminaria digitata (Huds.) Lamour. (from Fife Ness, Scotland, May–August 1987) in a seawater-based medium were 0.82, 0.58 and 1.34 Osmol kg^–1, respectively. The turgor pressure of F. spiralis on the shore at Fife Ness (June 1987) was 0.74 Osmol kg^–1.     

Terrestrial ecosystem recovery--modelling the effects of reduced acidic inputs and increased inputs of sea-salts induced by global change

The reduced emissions of acidifying sulfur and nitrogen in Europe since the late 1970s will be further reduced when the Gothenburg protocol is fully implemented by 2010. Here we address the consequences for the recovery of acidified terrestrial ecosystems using the acidification model MAGIC applied to 3 large-scale "clean rain" experiments, the so-called roof experiments at Risdalsheia, Norway; G?rdsj?n, Sweden, and Klosterhede, Denmark. Implementation of the Gothenburg protocol will initiate recovery of the soils at all 3 sites by rebuilding base saturation. The rate of recovery is small and base saturation increases less than 5% over the next 30 years. A climate-induced increase in storm severity will increase the sea-salt input to the ecosystems. This will provide additional base cations to the soils and more than double the rate of the recovery, but also lead to strong acid pulses following high sea-salt inputs as the deposited base cations exchange with the acidity stored in the soil. Future recovery of soils and runoff at acidified catchments will thus depend on the amount and rate of reduction of acid deposition, and in the case of systems near the coast, the frequency and intensity of sea-salt episodes as well.     

Distribution of chlorpyrifos in air and on surfaces following crack and crevice application to rooms

Measureable levels of chlorpyrifos were seen in air and on horizontal and vertical surfaces over an 84-day sampling period following application by two different methods. Pressurized aerosol applications had the highest airborne levels over the 84-day sampling period, and movement into adjacent, nontreated rooms was seen 7 days after application. Highest surface residues found were located at floor/wall interfaces and were due probably as a result of splash or overspray around treated areas. Residue levels from desk sides were very low and all surface residues were highly variable. One could not predict what surface levels would be based upon airborne concentrations.     

An ecosystem report on the Panama Canal: monitoring the status of the forest communities and the watershed

In 1996, the Smithsonian Tropical Research Institute and the Republic of Panama's Environmental Authority, with support fromthe United States Agency for International Development, undertook a comprehensive program to monitor the ecosystem of the Panama Canal watershed. The goals were to establish baselineindicators for the integrity of forest communities and rivers. Based on satellite image classification and ground surveys, the2790 km² watershed had 1570 km² of forest in 1997, 1080 km² of which was in national parks and nature monuments. Most of the 490 km² of forest not currently in protected areas lies along the west bank of the Canal, and its managementstatus after the year 2000 turnover of the Canal from the U.S. to Panama remains uncertain. In forest plots designed to monitorforest diversity and change, a total of 963 woody plant specieswere identified and mapped. We estimate there are a total of 850–1000 woody species in forests of the Canal corridor. Forestsof the wetter upper reaches of the watershed are distinct in species composition from the Canal corridor, and have considerably higher diversity and many unknown species. Theseremote areas are extensively forested, poorly explored, and harbor an estimated 1400–2200 woody species. Vertebrate monitoring programs were also initiated, focusing on species threatened by hunting and forest fragmentation. Large mammals are heavily hunted in most forests of Canal corridor, and therewas clear evidence that mammal density is greatly reduced in hunted areas and that this affects seed predation and dispersal. The human population of the watershed was 113 000 in 1990, and grew by nearly 4% per year from 1980 to 1990. Much of this growth was in a small region of the watershed on the outskirts of Panama City, but even rural areas, including villages near and within national parks, grew by 2% per year. There is no sewage treatment in the watershed, and many towns have no trashcollection, thus streams near large towns are heavily polluted. Analyses of sediment loads in rivers throughout the watershed did not indicate that erosion has been increasing as a result ofdeforestation, rather, erosion seems to be driven largely by total rainfall and heavy rainfall events that cause landslides.Still, models suggest that large-scale deforestation would increase landslide frequency, and failure to detect increases inerosion could be due to the gradual deforestation rate and the short time period over which data are available. A study of runoff showed deforestation increased the amount of water fromrainfall that passed directly into streams. As a result, dry season flow was reduced in a deforested catchment relative to aforested one. Currently, the Panama Canal watershed has extensive forest areasand streams relatively unaffected by humans. But impacts of hunting and pollution near towns are clear, and the burgeoningpopulation will exacerbate these impacts in the next few decades.Changes in policies regarding forest protection and pollution control are necessary.     

STREAM HEALTH RANKINGS PREDICTED BY SATELLITE DERIVED LAND COVER METRICS1

ABSTRACT: Land cover and land use change have long been known to influence the chemical, physical, and biological characteristics of streams. This study makes use of land cover maps derived from fine resolution satellite imagery and an extensive stream quality dataset to determine the relationship between small watershed health rankings and land cover composition and configuration. Landscape metrics were derived from digital impervious surface area (ISA), tree cover (percent), and agricultural crop maps within Montgomery County, Maryland. Watershed rankings were developed by state and county collaborators (MD‐DNR and MCDEP) using extensive biological and chemical measurements. In stepwise logistic regression models the factors accounting for the most variation in stream health ranking were the percent ISA, followed by the percent of tree cover. Riparian buffer zone tree cover was also a significant predictor. Of the metrics that considered the spatial configuration of the landscape, a contagion index and the percent of ISA in the flow path from the ISA to the stream were also found to be significant predictors of stream health. Despite limited ability to characterize landscape configuration or narrow riparian buffer zone vegetation with coarser resolution imagery (from Landsat), model results were not significantly different from those based on the use of fine‐resolution ISA information, suggesting that broader area applications of the approach are possible. The results indicate that management practices designed to improve stream water quality should focus on the amount of ISA and tree cover in both the watershed and within the buffer zone.     

Effects of recreational use on forested sites

Impact of recreational activities on soil and vegetation was evaluated in eight forested camping and picnic areas in southern Rhode Island. Forest vegetation consists of mixed-oak and white pine stands. Soils are of granitic glacial till or outwash origin and textures range from loamy sand to find sandy loam. Recreational use resulted in significant compaction of soils as indexed by soil penetration resistance and bulk density. Evidence indicates that compaction influences bulk densities to a depth of about 12.7 cm. Rates of water infiltration are less on recreation areas. Soil water accretion and depletion during the growing season are less rapid on recreation sites than on control sites. Differences are attributed to reduced infiltration, percolation, and rooting activity. Much of the ground surface on recreation areas is devoid of vegetation. The surface consists primarily of bare mineral soil, rock, or litter. The plants most commonly present are grasses. Native ground cover vegetation including tree seedlings, ericaceous shrubs and herbs has been eliminated or greatly reduced by trampling. Damage to tree trunks is common in recreation areas. White pine radial growth and scarlet oak height growth were significantly less on recreation sites. Scarlet oak appears intolerant to heavy recreation use.     

PLANNITG INDIANA'S WATER INFRASTRUCTURE FROM A COMPETITIVE PERSPECTIVE1

ABSTRACT: Indiana has embarked on a program to assess the condition of its infrastructure and to plan for its future. The perspective of this planning differs from the traditional “master plan” approach — instead, the focus is on competitiveness for economic development. The initial work on the water and sewerage competitiveness of the infrastructure includes: (1) a comparative analysis of the water resources and infrastructure of Indiana and its industrial midwestern neighbors; (2) a technology scan to identify possible technological opportunities that may be important for Indiana; and (3) a set of recommendations for future planning. This work is preliminary in nature but should serve as a starting point for continued strategic planning over the next decade for positioning of Indiana's water and sewerage infrastructure as a key element in the economic growth equation.     

ESTIMATION OF WATER TEMPERATURE EXCEEDANCE PROBABILITIES USING THERMO-HYDRODYNAMIC MODELING1

ABSTRACT: A continuous simulation approach is proposed for estimating water temperature exceedance probabilities using thermo-hydrodynamic modeling. The approach uses (1) a deterministic unsteady flow and heat transport model, (2) continuous hydrological and meteorological data for a long historical period, and (3) synthetic records of tributary water temperatures and other model inputs. Representative historical records of streamflow, air temperatures, and other hydrometeorological variables are obtained from nearby gages. Stochastic modeling methods are used to construct synthetic records for other model inputs, including inflow water temperatures. An application of this deterministic-stochastic approach is presented for a complex waterway in northeastern Illinois with heat discharges from several power plants and wastewater treatment plants. Statistical results from the continuous simulations are compared to results obtained from traditional event simulations. The application illustrates the information that engineers and biologists can obtain for (1) evaluating compliance with water temperature standards, and (2) assessing the effect of water temperatures on aquatic habitat.     

Brood reduction in response to manipulated brood sizes in the common swift (Apus apus)

Following a brood size manipulation experiment on the common swift (Apus apus) in which different levels of parental effort were created, brood reduction occurred in all five nests manipulated to four chicks and in two of the five manipulated to three young. This provided an opportunity for looking in detail at the parental investment decisions concerning allocation strategies between parent and young during the process of brood reduction. The data recorded here were analysed on a visit-by-visit basis regarding changes in parental and chick body masses, the mass of prey delivered and the estimated mass of parental self-feeding. The results show that food delivery rates did not increase in proportion to the number of chicks in the broods. This reduction in delivery rates per chick resulted in lower chick masses and ultimately in the death of one or more chicks in the larger broods. The resulting low parental body masses for adult birds feeding larger broods suggested that these parents could not have raised all their young without risking their own survival. There was a tendency for parents from nests that experienced brood reduction to feed themselves instead of allocating most of the food gathered to the young. After brood reduction, parents regained lost body mass and their young fledged at masses only slightly lower than normal. The differential allocation decisions regarding parental self-feeding which resulted in brood reduction were largely responsible for keeping the parents in good enough condition to care for the surviving nestlings. Therefore, this study clearly demonstrates that brood reduction can operate through the differential allocation of food between parent and young in a way that can have adaptive consequences for the survival of parents and their young. Correspondence to: T.L.F. Martins