Effects of algal diet on digestive enzyme activity in Calanus helgolandicus

Adult female Calanus helgolandicus were transferred, immediately after collection in the English Channel in June 1984, to two unialgal diets one of which, the flagellate Cryptomonas maculata, was rich in starch, while the other, the diatom Thalassiosira weissflogii, contained no starch. The activity of the digestive enzymes amylase, trypsin and laminarinase was measured in these two populations under foodsaturating conditions over an acclimation period of eight days. Ingestion rates were measured on a daily basis and the results confirmed, together with a constant level of body protein, that the experimental conditions were above the incipient limiting concentration. In the long-term (4 to 8 d), the activities of all three enzymes were significantly elevated in the C. maculata-fed copepods, whereas ingestion rates were lower than those on T. weissflogii. These results observed under food-saturating conditions indicate a compensatory mechanism between digestive enzymes and the substrate ingested. They are consistent with previous work on Artemia sp. suggesting that the rate of assimilation is a function of the digestive enzyme activity and ingestion rate. Enzyme activity exhibited differing shortterm responses (<48 h) on transfer to the two algal diets, which are interpreted in relation to the in situ activity of the field population.Communicated by J. Mauchline, Oban     

Method of estimating the standing stock of Trochus niloticus incorporating Landsat satellite data,with application to the trochus resources of the Bourke Isles,Torres Strait,Australia

The habitat of Trochus niloticus in the Bourke Isles, Torres Strait, was classified into areas of a Landsat image, using high-ratio values of green (Band 2) to red (Band 3) light, along the windward reef margins. These shallow-water (< 15 m) areas have a coral and rubble/algal pavement cover, which constitutes the optimal habitat for this gastropod. The habitat was sampled to estimate the abundance of T. niloticus. The proportion of commercial-sized individuals was estimated by measuring the basal width of all individuals in a sample. A multistage sample design incorporating three spatial scales -100 m² (transect), 1500 m² (site) and 1 km² (reef) — was used to provide variance estimates for sample-design optimisation and to provide data on the spatial variation of abundance. Most variation (68%) in abundance was within reefs and was attributable to differences in reef cover. Variations in abundance and time costs for sampling 2 and 4 m transects were compared; the 2 m transect was more efficient than the 4 m transect. The abundance estimates were combined with habitat-area estimates and the proportion of commerical-sized individuals was estimated at a standing stock of 186000 (24% precision), or 14 t of commerical-sized T. niloticus.     

Resources policies in Australia

Developments in Australia's resource industries in recent years have raised policy issues not previously encountered, and their consideration has been superimposed onto traditional policies affecting resource production and use. This review of Australia's policies on resources - here meaning minerals and energy policies - looks at the objectives of these policies and their interrelationships. It considers issues such as management, development objectives, investment, taxation, environment and processing, and likely future developments.     

Tropical annual cropping systems: Ant ecology

The ecological role of ants in tropical annual cropping systems is discussed in general and with respect to a specific Mexican agroecosystem Generally, the potential positive contributions of ants to crop yields result from their impact on soil structure, nutrient cycling, and reduction of insect and weed pests In annual wet lowland fields in eastern Mexico, the ant community is simple and dominated by the aggressive fire ant,Solenopsis geminata. The influence of vegetation structure and composition on the ant community and, specifically, on the foraging behavior ofS geminata is discussed     

Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: Two-stage carcinogenesis in skin tumor sensitive mice (SENCAR)

Skin tumors can be induced by the sequential application of a subthreshold dose of a carcinogen (initiation phase), followed by repetitive treatment with a noncarcinogenic tumor promoter. There is a very good dose-response relationship between the induction of the number of papillomas per mouse at early times (10 to 20 weeks) by either tumor initiators and promoters and the final carcinoma incidence after a longer latency (20 to 50 weeks) in SENCAR mice. This system not only can be used to determine the tumor initiating and promoting activities of a compound but if the agent is given repeatedly by itself one can also determine if it is a complete carcinogen, i.e., if it has both tumor initiating and promoting activity. In addition, if the agent is given concurrently with a known complete carcinogen or a tumor initiator one can also determine if the agent has cocarcinogenic or cotumor initiating activity or even possibly anticarcinogenic activity. Likewise, if the agent is given concurrently with a known tumor promoter one can determine if the agent has copromoting or antipromoting activity. Using the SENCAR skin carcinogenesis system we have undertaken the determination of the skin carcinogenic, cocarcinogenic, tumor initiating and promoting activities of various diesel emission particle extracts as well as for comparative purposes, standards such as benzo(a)pyrene and 12-0-tetradecanoylphorbol-13-acetate and extracts of emissions from a gasoline engine, roofing tar, coke oven and cigarette smoke condensate. Most of the studies are still in progress but some preliminary data is available on the comparative tumor initiating activities of the various samples at 14 weeks. Caterpillar diesel and cigarette smoke condensate were essentially without activity, whereas the Mustang gasoline catalyst and Olds diesel gave extremely low values although they were slightly above background. Roofing tar, coke oven and Nissan Diesel all gave moderate activity at high doses (1 to 10 mg) but when compared to benzo(a)pyrene were relatively low values.     

The digital workshop: exploring the use of interactive and immersive visualisation tools in participatory planning

This paper examines the emerging role of digital tools in a collaborative planning process for British Columbia's Bowen Island. The goal of this research was to evaluate the effectiveness of a 'digital workshop', combining the interactive CommunityViz tool with the immersive lab facilities at the Collaborative for Advanced Landscape Planning (CALP). In support of the larger community planning process, two 3-h workshops were held at CALP's Landscape Immersion Lab. To facilitate collaborative exploration, the interactive landscape visualisation and real-time data analysis capabilities of CommunityViz were employed to illustrate the possible outcomes of residential density policies for Bowen Island's Snug Cove community. The community planning workshops were structured to provide the 14 semi-expert participants with the opportunity to explore and discuss the contentious residential density components of the draft Snug Cove Village Plan. The abilities to dynamically explore the visualisations of the planning proposals, and to see real-time changes in indicator metrics were considered particularly informative, and appeared to increase participants' understanding of the plan. Written and verbal responses indicated, however, that there was insufficient time to examine and interact with the information during the workshop, suggesting a need to examine in greater depth how and when these tools might best be employed in collaborative settings. Current and future research relating to this project is discussed.     

The design of water markets when instream flows have value

The main objective of this paper is to design and test a decentralized exchange mechanism that generates the location-specific pricing necessary to achieve efficient allocations in the presence of instream flow values. Although a market-oriented approach has the potential to improve upon traditional command and control regulations, questions remain about how these rights-based institutions can be implemented such that the potential gains from liberalized trade can be realized. This article uses laboratory experiments to test three different water market institutions designed to incorporate instream flow values into the allocation mechanism through active participation of an environmental trader. The smart, computer-coordinated market described herein offers the potential to significantly reduce coordination problems and transaction costs associated with finding mutually beneficial trades that satisfy environmental constraints. We find that direct environmental participation in the market can achieve highly efficient and stable outcomes, although the potential does exist for the environmental agent to influence outcomes.