Vertical distribution of Calanus finmarchicus and C. helgolandicus in relation to the development of the seasonal thermocline in the Celtic Sea

The geographical distribution and annual mean abundance of Calanus finmarchicus (Gunnerus) and C. helgolandicus (Claus) in the northern North Atlantic Ocean were shown in relation to the seasonal and annual fluctuations of abundance of the species in the Celtic Sea from 1960 to 1981. These congeneric copepods, although showing allopatric distributions over most of their geographical range, have sympatric distributions in the Celtic Sea where they dominate the dry weight biomass of the plankton throughout the year. The two species respond differently to the development of the seasonal thermocline and halocline by taking up different vertical distributions in the water column. C. finmarchicus occurred in the colder, more saline water below the thermocline, while C. helgolandicus occurred in the warmer, less saline water above the thermocline. This behaviour is postulated as a mechanism by which these morphologically similar copepods more fully exploit the resources of their temporally and spatially heterogeneous environment and also minimise interspecific competition. The species have the same foraging techniques and are able to exploit the same size spectrum of particulates. The vertical depth strata in which the populations are found for most of the year in the Celtic Sea means that both species exploit the diatom bloom in early spring but, thereafter, C. helgolandicus grazes on the daily production of the autotrophs in the euphotic zone while C. finmarchicus, below the thermocline, has to rely for its food on sedimenting particulates (whole cells, detritus and faecal material). The isolating mechanisms whereby these two populations partition the habitat in the Celtic Sea are discussed.     

Isolation,purification and partial characterization of four digestive proteases from the purple seastar Pisaster ochraceus

An investigation of enzymatic activity in the pyloric caeca of Pisaster ochraceus collected at Post Point, Bellingham, Washington, USA, in 1982, revealed the presence of four distinct proteases. These enzymes have been partially purified and characterized and display tryptic, chymotryptic and carboxypeptidase A-like activity. The two distinctive tryptic enzymes have molecular weights of 88 000 and 25 200 daltons, respectively, as determined by reducting SDS-PAGE electrophoresis. The chymotryptic and carboxypeptidase A proteases have molecular weights of 22 800 and 34 400 daltons, respectively. The tryptic and chymotryptic enzymes are inactivated by phenylmethylsulfonyl fluoride, indicating that all are serine proteases. Both trypsins are inhibited by soybean trypsin inhibitor; however, the high molecular weight trypsin was not inhibited by tosyl-L-lysine chloromethyl ketone. The chymotrypsin was inhibited by tosyl-L-phenylalanine chloromethyl ketone. Both reagents indicate the involvement of histidine in the active site. The low molecular weight trypsin and the chymotrypsin were able to activate bovine trypsinogen to trypsin, as determined in a modified PAGE electrophoresis with trypsinogen and casein copolymerized in the gel.     

Grazing effects on nitrogen fixation in coral reef algal turfs

This study addressed whether grazing by the sea urchin Diadema antillarum influenced rates of nitrogen fixation by algal turf communities on Caribbean coral reefs. Because the turfs were nitrogen-limited, we also assessed whether newly-fixed nitrogen was important for supporting net primary productivity by the turfs. We measured acetylene reduction in turfs grown in treatments excluding or including D. antillarum in the presence of other herbivores at 3 m water depth on Tague Bay forereef, St. Croix, U.S. Virgin Islands. These were the first measurements of acetylene reduction on coral reefs under quasi-natural conditions of high water-flow and photosynthetic oxygen generation. Rates of acetylene reduction under these conditions were as high as any measured previously in coral reef communities (mean 7.6 nmol C₂H₄ cm⁻² h⁻¹). Algal turfs grazed by D. antillarum and other herbivores had chlorophyll-specific acetylene reduction rates up to three times higher than when D. antillarum was excluded. High rates of nitrogen fixation by the turfs were sufficient to meet <2% of the nitrogen required to support net chlorophyll-specific primary productivity over 24 h. Grazer-mediated increases in nitrogen fixation do not appear responsible for a parallel enhancement of net primary productivity. Algal turfs at this site must be dependent primarily on external sources of nitrogen. Received: 1 July 1997 / Accepted: 5 September 1997     

In situ mapping of growth lines in the calcitic prismatic layers of mollusc shells using X-ray absorption near-edge structure (XANES) spectroscopy at the sulphur K-edge

The microstructure and composition, including chemical speciation of sulphur (S), of two mollusc shells were investigated using a combination of scanning electron microscopy, X-ray absorption near-edge structure spectroscopy (XANES) and electron probe microanalysis (EPMA). The shell of Pinna is composed of monocrystalline, and Pinctada, of polycrystalline, calcite prisms separated by organic-rich walls. Sulphur speciation information from XANES spectra using a scanning X-ray microscope showed that the protein S content of the interprismatic walls is higher than the SO₄ content, whereas the reverse is true for the intraprismatic structures. High-spatial-resolution XANES maps for the different S species across adjacent calcite prisms confirm their distinctive distributions in the molluscan shells and illustrate the presence of narrow, submicron transverse growth features. On a larger scale, a series of wider growth zones, incorporating the submicron zones, are aligned parallel to each other and cross-cut many calcite prisms. EPMA element maps for magnesium (Mg) and S demonstrate that these growth increments are compositionally zoned, comprising alternating layers of high mineral (Mg-rich) and high organic (S-rich) components. Additionally, these maps confirm that the organic interprismatic walls have lower Mg and higher S than the intraprismatic structures.     

An improved user-based beach climate index

In many coastal resort areas of the world, it is likely that optimal climatic conditions for beach use might occur outside the peak of the tourist season. Investigation of this issue together with associated publicity might help to spread the tourism load and hence reduce undesirable social and environmental effects of extreme seasonality in tourist demand. For this to take place, better knowledge of beach user preferences in terms of climate and bathing water temperature is required. Questionnaire surveys were carried out in Wales, Malta and Turkey to establish the preferences of north European beach users for thermal sensation and bathing water temperature, plus priority levels for other climatic attributes. A user-based beach climate index based on these preferences and priorities was formulated. Linkage was made between the user-generated ratings for various climatic conditions and published climate data to evaluate most major Euro-Mediterranean/Black Sea and a range of other beach tourism areas on a month-by-month basis. Results showed excessively hot thermal sensation in many southern and eastern Mediterranean coastal destinations during July and August, the present peak of the beach tourism season. Highest preference was given to water temperatures rather lower than those found in these areas during late summer. Many long haul coastal destinations popular with north European visitors had similar unpleasant thermal sensations over several months. Uncertainties and deficiencies still exist with the system, but from the point of view of north European beach users the final scores generated in this study may be regarded as good approximations of the quality of resort area climates for sedentary beach use.     

Aquatic litter, management and prevention—the role of measurement

Methodology of litter management has many forms and increasingly measurement is linked to management. By providing measured profiles of the quality of litter types, trends in the input of new items can be assessed and prevention programmes directed more effectively to sources. Developing methodologies and their application to management cover three main areas.

Yields of Dissolved Organic C,N, and P. from Three High-Elevation Catchments,Colorado Front Range,U.S.A.

Ecosystem dynamics in high-elevation watersheds are extremely sensitive to changes in chemical, energy, and water fluxes. Here we report information on yields of dissolved organic C, N, and P for the 1999 snowmelt runoff season from three high-elevation catchments in the Colorado Front Range, U.S.A.: Green Lake 4 (GL4) and Albion townsite (ALB) on North Boulder Creek and the Saddle Stream (SS), a tributary catchment dominated by alpine tundra. Dissolved organic carbon (DOC) concentrations in stream waters ranged from <1 to 10 mg C L^-1, with the highest values occurring at the SS site. Dissolved organic nitrogen (DON) concentrations ranged from below detection limits to 0.28 mg N L^-1 and were again highest at the tundra-dominatedsite. Dissolved organic phosphorus (DOP) concentrations were at or near detection limits throughout the season in all three catchments indicating a strong terrestrial retention of P. OnlyDOC showed a significant relationship to discharge. Yields of DOC in the three catchments ranged from 10.6 to 11.8 kg C ha^-1 while yields of DON and DOP ranged from 0.32 to 0.41 and 0.02 to 0.08 kg ha^-1, respectively. The relatively highyield of organic N and P relative to C from the highest elevationsite (GL4) was somewhat surprising and points to either: (1) a source of dissolved organic material (DOM) in the upper reaches of the catchment that is enriched in these nutrients or (2) theselective uptake and processing of organic N and P downstream ofthe sampling site. Additionally, seasonal changes in the relativeimportance of DOM precursor materials appear to result in changesin the N content of DOM at both the GL4 and ALB sites.     

The environmental and biosecurity characteristics of livestock carcass disposal methods: A review

Livestock mortalities represent a major waste stream within agriculture. Many different methods are used throughout the world to dispose of these mortalities; however within the European Union (EU) disposal options are limited by stringent legislation. The legal disposal options currently available to EU farmers (primarily rendering and incineration) are frequently negatively perceived on both practical and economic grounds. In this review, we assess the potential environment impacts and biosecurity risks associated with each of the main options used for disposal of livestock mortalities in the world and critically evaluate the justification for current EU regulations. Overall, we conclude that while current legislation intends to minimise the potential for on-farm pollution and the spread of infectious diseases (e.g. transmissible spongiform encephalopathies, bacterial pathogens), alternative technologies (e.g. bioreduction, anaerobic digestion) may provide a more cost-effective, practical and biosecure mechanism for carcass disposal as well as having a lower environmental footprint. Further social, environmental and economic research is therefore warranted to assess the holistic benefits of alternative approaches for carcass disposal in Europe, with an aim to provide policy-makers with robust knowledge to make informed decisions on future legislation.     

Removal potential of toxic 2378-substituted PCDD/F from incinerator flue gases by waste-derived activated carbons

The application of activated carbons has become a commonly used emission control protocol for the removal or adsorption of persistent organic pollutants from the flue gas streams of waste incinerators. In this study, the 2378-substituted PCDD/F removal efficiency of three types of activated carbons derived from the pyrolysis of refuse derived fuel, textile waste and scrap tyre was investigated and compared with that of a commercial carbon. Experiments were carried out in a laboratory scale fixed-bed reactor under a simulated flue gas at 275 °C with a reaction period of four days. The PCDD/F in the solid matrices and exhaust gas, were analyzed using gas chromatography coupled with a triple quadrupole mass spectrometer. In the absence of activated carbon adsorbent, there was a significant increase in the concentration of toxic PCDD/F produced in the reacted flyash, reaching up to 6.6 times higher than in the raw flyash. In addition, there was a substantial release of PCDD/F into the gas phase, which was found in the flue gas trapping system. By application of the different commercial, refuse derived fuel, textile and tyre activated carbons the total PCDD/F toxic equivalent removal efficiencies in the exhaust gas stream were 58%, 57%, 64% and 52%, respectively. In general, the removal of the PCDDs was much higher with an average of 85% compared to PCDFs at 41%. Analysis of the reacted activated carbons showed that there was some formation of PCDD/F, for instance, a total of 60.6 μg I-TEQ kg⁻¹ toxic PCDD/F was formed in the refuse derived fuel activated carbon compared to 34 μg I-TEQ kg⁻¹ in the commercial activated carbon. The activated carbons derived from the pyrolysis of waste, therefore, showed good potential as a control material for PCDD/F emissions in waste incinerator flue gases.