Lead and cadmium in urban allotment and garden soils and vegetables in the United Kingdom

In order to assess the intake of lead and cadmium by consumers of home grown vegetables in urban areas, replicated experimental plots of uniform size, comprising summer and winter crops, were established in 94 gardens and allotments in nine towns and cities in England.The geometric mean lead and cadmium concentrations for the soils (n = 94) were 217 g g^–1 (ranging from 27 to 1,676 g g^–1) and 0.53 g g^–1 (<0.2–5.9 g g^–1), respectively. Compared with agricultural soils, the garden and allotment soils contained elevated levels of lead but not cadmium.Lead concentrations in the vegetables ranged from <0.25 g g^–1 to 16.7 g g^–1 dry weight and cadmium concentrations ranged from <0.025 g g^–1 to 10.4 g g^–1 dry weight. Lead concentrations were higher than reported background levels, although <1% exceeded the statutory limit for saleable food in the UK (1 g g^–1 fresh weight). Cadmium concentrations were generally similar to background levels.     

Performance and mechanism for cadmium and lead adsorption from water and soil by corn straw biochar

Cadmium (Cd) and lead (Pb) in water and soil could be adsorbed by biochar produced from corn straw. Biochar pyrolyzed under 400°C for 2 h could reach the ideal removal efficiencies (99.24%and 98.62% for Cd and Pb, respectively) from water with the biochar dosage of 20 g·L^–1 and initial concentration of 20 mg·L^–1. The pH value of 4–7 was the optimal range for adsorption reaction. The adsorption mechanism was discussed on the basis of a range of characterizations, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Raman analysis; it was concluded as surface complexation with active sorption sites (-OH, -COO-), coordination with π electrons (C = C, C = O) and precipitation with inorganic anions (OH^-, CO₃ ^2–, SO₄ ^2–) for both Cd and Pb. The sorption isotherms fit Langmuir model better than Freundlich model, and the saturated sorption capacities for Cd and Pb were 38.91 mg·g^-1 and 28.99 mg·g^–1, respectively. When mixed with soil, biochar could effectively increase alkalinity and reduce bioavailability of heavy metals. Thus, biochar derived from corn straw would be a green material for both removal of heavy metals and amelioration of soil.

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Biochemical and energetic composition of bathyal echinoids and an asteroid,holothuroid and crinoid from the Bahamas

The biochemical and energetic composition of body components of ten species of bathyal echinoids, and an asteroid, a holothuroid and a stalked crinoid were determined from individuals sampled from a variety of deep-water sites near the Bahamas (north Caribbean Sea) in October 1988. When compared with other studies of echinoderms, no geographic- or depth-related differences in biochemical or energetic composition were found. Body-wall tissues were composed primarily of skeletal material (mineral ash), but were comparatively high in organic material in the echinothuriid echinoids, and the asteroid and holothuroid. Gut tissues and pyloric cecae had high levels of lipid and protein, indicating their potential role in nutrient storage. Body-wall tissues were generally low in energy, but were highest in the echinoidsAraeosoma belli (7.7 kJ g^–1 dry wt) andSperosoma antillense (8.0 kJ g^–1 dry wt), the asteroidOphidiaster alexandri (8.9 kJ g^–1 dry wt), and the holothuroidEostichopus regalis (13.1 kJ g^–1 dry wt). Energy levels of gut and pyloric cecal tissues were two to three times higher than those of body-wall tissues. Total somatic tissue energy values varied greatly among species, ranging from 1.5 kJ in the echinoidAspidodiadema jacobyi to 142.1 kJ inE. regalis. As the bathyal echinoderms examined in this study occur in great abundance, they represent a significant reservoir of organic and inorganic materials and energy in deep-water benthic systems.     

Plasmatic resistance and rate of respiration and photosynthesis of Zostera marina at different salinities and temperatures

Zostera marina L. was studied at the Izembek Lagoon, Alaska Peninsula. Two morphologically different forms, tidepool and subtidal, can be distinguished. Both show a high tolerance to different salinities and temperatures. The plasmatic resistance was found in a range of distilled H₂O up to 3.0 seawater (24 h) and between-6° and 34°C (12 h). Within these resistance limits, the photosynthesis, which has its maximum in normal (1.0) seawater, decreases nearly to zero not only in distilled H₂O but even in 2.0 seawater, and increases with the temperature in the tidepool form up to 35°C, but in the subtidal form up to 30°C only. At higher temperatures photosynthesis declines sharply in both forms. Respiration has its minimum in distilled H₂O and at 0°C and increases with increasing salinity and temperature.Dedicated to Prof. Dr. Dr. h. c. mult. K. Mothes, Halle, Germany (DDR) on the occasion of his 70th birthday.     

Cryptic species and population structuring of the Atlantic and Pacific seabob shrimp species, Xiphopenaeus kroyeri and Xiphopenaeus riveti

Seabob shrimps of the genus Xiphopenaeus are important fishery resources along the Atlantic and Pacific coasts of Central and South America. The genus was considered to comprise two species: the Atlantic Xiphopenaeus kroyeri (Heller, Sitzungsber Math Naturwiss cl kaiserliche Akad Wiss Wien 45:389–426, 1862), and the Pacific Xiphopenaeus riveti (Bouvier, Bull Mus Hist Nat Paris 13:113–116, 1907). In a recent review, Xiphopenaeus was regarded as a monotypic genus, on the basis that no clear morphological differences could be found between Pacific and Atlantic specimens (Pérez Farfante and Kensley, Mem Mus Nat Hist Nat Paris 175:1–79, 1997). In the present work, nuclear (allozymes), and mitochondrial (Cytochrome Oxidase I) genes were used to demonstrate the validity of X. riveti and reveal the presence of two cryptic species of Xiphopenaeus within X. kroyeri in the Atlantic Ocean. The high levels of molecular divergence among these species contrast with their high morphological resemblance. Interspecific sequence divergences (Kimura 2-parameter distance) varied from 0.106 to 0.151, whereas intraspecific distances ranged from 0 to 0.008 in Xiphopenaeus sp. 1, from 0 to 0.003 in Xiphopenaeus sp. 2, and from 0.002 to 0.005 in X. riveti. In addition, five diagnostic allozyme loci were found between sympatric samples of Xiphopenaeus sp. 1 and 2 along the Brazilian coast. The results suggest that Xiphopenaeus sp. 2 from the Atlantic is more closely related to the Pacific X. riveti than to the Atlantic Xiphopenaeus sp. 1. Furthermore, a high level of genetic structuring (Xiphopenaeus sp. 1: F _ST =0.026; P<0.05; Xiphopenaeus sp. 2: F _ST =0.055; P<0.01) was found in the Brazilian Xiphopenaeus populations, indicating the presence of different genetic stocks in both Atlantic species. These findings have important commercial implications as they show that the fisheries of the two Atlantic species must be managed separately, and that each one is comprised of different populations.Communicated by O. Kinne, Oldendorf/Luhe     

Extra- and intracellular acid-base balance and ionic regulation in cod (Gadus morhua ) during combined and isolated exposures to hypercapnia and copper

Cod (Gadus morhua) were exposed to hypercapnia (water Pco₂ = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely compensated within 12 to 24 h via a chloride-mediated increase in extracellular [HCO₃ ⁻]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma [Na⁺] and [Cl⁻] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma [Na⁺] and [Cl⁻] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances. The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia. Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma were significantly elevated only after 48 h, with liver showing the largest elevation. Received: 15 November 1996 / Accepted: 2 December 1996     

Some new data on skin-digestion and absorption in urchins and sea stars (Asterias and Henricia)

An adult Psammechinus miliaris, and another specimen 8 mm in diameter were both fed apically by deposition of a protein-powder extracted from a heavily ¹⁴C-tagged urchin. The organs of the former were counted and the latter was totally sectioned and autoradiographed. The gut was more labelled than expected after an apical meal. This could be explained by a pumping of some nutritive powder into the gut, the bright marking of the superficial tissues being obviously due to direct uptake. The localized proteolysis produced by a podial disc of P. miliaris on a black gelatin-film may be due to the secretion of special cell-masses just underlying the calcareous plates of the disc. Extracts from mucus, small spines and dorsal podia from the anterior furrow of Echinocardium cordatum produce a conspicuous digestion of Remazol-brilliant blue hidepowder in vitro. Several in vivo tests with artificial substrates suggest the existence of a trypsin-like enzyme and not chymiotrypsin in the mucus. Fresh frozen sections in podia of Asterias rubens treated with A.S. naphthol-propionate showed that special cells, scattered in the connective tissue, gave a dark-red stain. Strains of red granules issued by them found their way to the surface of the disc between the columnar epithelial cells. These chimiotrypsin-positive cells and their products seem identical to those seen by Chaet and Philpot (1964) in A. forbesi. These authors did not suspect their digestive function. The nutrition of Henricia sanguinolenta through the body wall was tested either with radioactive diatoms or ¹⁴C-labelled amino acids in sea water selectively offered to one or two arms. Both countings and autoradiographs demonstrated the importance of skin-digestion and absorption, especially in the ambulacra. The absorbed nutrients reach the muscle layer, not only the epiderm as mentioned in Ferguson's (1967) esperiments.     

Bacterial degradation of monocrotophos and phyto- and cyto-toxicological evaluation of metabolites

The bacterium Serratia marsescens strain JAS16 was isolated from agricultural soil which had prior exposure to monocrotophos for three years. The strain JAS16 tolerated up to 1200 mg L^–1 monocrotophos and degraded the insecticide (1000 mg L^–1) at a degradation rate constant of 136 d^?1 (DT₅₀ = 3.7 d). In soil, the degradation rate constant was 105 d^?1 (DT₅₀ = 4.8 d). A schematic pathway is being proposed from the degraded products derived from gas chromatography--mass spectrometry (GC-MS). The phytotoxicity of degradation products to Vigna radiata, Vigna unguiculata, and Macrotyloma uniflorum and the genotoxicity to Allium cepa roots were found to be low. A cost-effective powder-based formulation was achieved with the isolate. The isolate remained viable during the storage and also multiplied with a higher colony forming units (CFU) load g^–1 for over a period of seven weeks of storage.     

Submesoscale distribution of Antarctic krill and its avian and pinniped predators before and after a near gale

We conducted two ship-based surveys of the nearshore ecosystem north of Livingston Island, Antarctica during 2–10 February 2005. Between the two surveys, a low-pressure system (963 mbar) passed through the area providing the opportunity to measure ecosystem parameters before and after a near gale. A ship-based multiple-frequency acoustic-backscatter survey was used to assess the distribution and relative abundance of Antarctic krill (Euphausia superba). Net tows, hydrographic profiles, and meteorological data were collected to measure biological and physical processes that might affect the krill population. During the survey, the distribution and behavior of several krill predators [chinstrap penguins (Pygoscelis antarctica), cape petrels (Daption capense), and Antarctic fur seals (Arctocephalus gazella)] were measured from the vessel by visual observations. The survey encompassed an area of roughly 2,500 km², containing two submarine canyons with one to the west and one to the east of Cape Shirreff, which had different abundances of krill and predators. Several aspects of the nearshore ecosystem changed after the near gale including: hydrography of the upper 100 m of the water column, phytoplankton biomass, the abundance and distribution of krill, and the distribution of some krill predators. Differences in these parameters were also measured between the two canyons. These changes in the physical and biological environment during the survey period are quantified and show that the ecosystem exhibited significant changes over relatively short spatial (tens of kilometers) and time (tens of hours) scales.     

Gametic incompatibility and genetic divergence of Pacific and Kumamoto oysters,Crassostrea gigas and C. sikamea

The biological and taxonomic separation of the Pacific oyster Crassostrea gigas (Thunberg, 1793) from the Kumamoto oyster C. sikamea (Amemiya, 1928) is affirmed by three concordant lines of evidence: (1) fixed differences in 2% of a mtDNA sequence coding for large subunit rRNA; (2) a genetic distance of 0.440 based on 19 allozyme loci, including 5 diagnostic loci (Aat-1, Idh-1, Idh-2, Mpi-1, Mdh-2); (3) one-way gametic incompatibility resulting in partial reproductive isolation in interspecific crosses. C. gigas sperm x C. sikamea egg fertilizations form viable hybrid offspring, but C. sikamea sperm do not fertilize C. gigas eggs. Divergence between these two species is mediated by differing peaks in the periods for gamete release and by one-way sperm/egg incompatibility. Two attempts to recover C. sikamea from its place of origin in southern Japan have yielded only individuals with the mitochondrial haplotype that characterizes C. gigas. We thus identify a crucial need for careful screening, management, and conservation of the cultivated populations of C. sikamea on the US west coast.     

Inhibition and facilitation of bryozoan and ascidian settlement by natural multi-species biofilms: effects of film age and the roles of active and passive larval attachment

Sessile marine invertebrate larvae can recognize suitable settlement substrata by using various environmental cues, including organic/microbial biofilms. In laboratory choice assays, the effect of biofilms of varying ages on the settlement behaviour of two fouling organisms was assessed. The species included the arborescent cheilostome bryozoan Bugula flabellata (Thompson) and the solitary ascidian Ciona intestinalis (L.), both of which are characteristic of temperate sublittoral hard substratum assemblages in northwest Europe. Experiments were carried out using polystyrene petri dish substrata preconditioned with multispecies biofilms from natural laboratory-aquarium seawater for 1, 3, 6 or 12 d. Unfilmed (new, initially sterile) dishes were used as control substrata. Whereas the coronate larvae of B. flabellata generally were inhibited by biofilming, irrespective of film age, the settlement of tadpole larvae of C. intestinalis was facilitated on biofilmed substrata, and numbers of settled larvae generally increased with biofilm age: the highest mean numbers were counted on 12 d-old biofilms. In C. intestinalis, settlement and metamorphosis are processes which can be temporally separate and are possibly induced by different environmental cues. This study therefore distinguished between C. intestinalis larvae which were attached to the biofilm surface by the anterior, and those larvae entrapped by the biofilm but not settled in the conventional meaning of the term. As reported in previous studies, we did observe that such entrapped larvae could subsequently attach and develop successfully into sessile juveniles. Both the numbers of “attached” and “trapped” tadpoles increased with biofilm age. Assuming that “settlement” is essentially a process involving the active behavioural response of larvae to environmental cues, it seems that the facilitated attachment of C. intestinalis onto biofilmed substrata is due to the combined effect of active habitat selection and passive deposition/“entrapment” of larvae onto the “sticky” substratum. Received: 21 August 1996 / Accepted: 21 November 1996     

Biochemical composition and digestive enzyme activity in larvae and postlarvae ofPenaeus japonicus during herbivorous and carnivorous feeding

The growth, survival, digestive enzyme activity and biochemical composition ofPenaeus japonicus (Bate) larvae and postlarvae were measured under three feeding regimes. Larvae were reared through the protozoeal stages usingChaetoceros gracilis. From the first mysis stage, three feeding regimes were used; (A)C. gracilis plusArtemia sp. nauplii, (B)Artemia sp. nauplii alone or (C)C. gracilis alone. No significant difference was found in growth, survival, protein content or lipid content of postlarvae from the treatments receiving the single-feed type, despite the low protein (7%) and highly unsaturated fatty acid content of the alga. Growth of larvae receiving the mixed diet was significantly higher than in the other treatments. Trypsin activity was more strongly influenced than amylase activity by dietary treatment, and differences in the ratio of these enzymes between treatments suggest independent control of their secretion. Trypsin activity recorded in larvae feeding onC. gracilis was up to six time higher than in larvae feeding onArtemia sp. nauplii, apparently in response to the low protein content of the alga. Larvae receiving the mixed diet exhibited an intermediate level of trypsin activity; it is suggested that the ingestion of algae is necessary for optimal assimilation of the zooplankton component of the diet.     

Light and temperature demands for growth and reproduction of laminarian gametophytes in southern and central California

The gametophytes of 9 laminarian species (4 from southern California, and 5 from central California, USA) became fertile in the unicellular stage (female gametophytes) or in a few-celled stage (male gametophytes), when appropriate temperatures and a sufficiently high quantum irradiance in the blue part of the spectrum were supplied. Vegetative growth, leading to the formation of filamentous gametophytes was light-saturated at relatively low irradiances (4 W m^-2; equivalent to about 2 nE cm^-2 sec^-1 or an illuminance of 1000 lux), whereas 2 to 3 times this irradiance in continuous fluorescent cool white light was needed to induce the majority of the gametophytes to become fertile. An illuminance of 8300 lux did not inhibit the development of the gametophytes from southern Californian species. Egregia menziesii exhibited an exceptionally low quantum demand for induction of fertility. Gametophytes of species from central and southern California differed in regard to their temperature optimum for growth (12°C in the former, 17°C in the latter) and their upper temperature limit for reproduction (17°C in the former, 20°C in the latter).     

Spatial and temporal pattern in seagrass community composition and productivity in south Florida

We document the distribution and abundance of seagrasses, as well as the intra-annual temporal patterns in the abundance of seagrasses and the productivity of the nearshore dominant seagrass (Thalassia testudinum) in the south Florida region. At least one species of seagrass was present at 80.8% of 874 randomly chosen mapping sites, delimiting 12,800 km² of seagrass beds in the 17,000-km² survey area. Halophila decipiens had the greatest range in the study area; it was found to occur over 7,500 km². The range of T. testudinum was almost as extensive (6,400 km²), followed by Syringodium filiforme (4,400 km²), Halodule wrightii (3,000 km²) and Halophila engelmanni (50 km²). The seasonal maxima of standing crop was about 32% higher than the yearly mean. The productivity of T. testudinum was both temporally and spatially variable. Yearly mean areal productivity averaged 0.70 g m⁻²day⁻¹, with a range of 0.05–3.29 g m⁻² day⁻¹. Specific productivity ranged between 3.2 and 34.2 mg g⁻¹ day⁻¹, with a mean of 18.3 mg g⁻¹ day⁻¹. Annual peaks in specific productivity occurred in August, and minima in February. Integrating the standing crop for the study area gives an estimate of 1.4 × 1011 g T. testudinum and 3.6 × 10¹⁰ g S. filiforme, which translate to a yearly production of 9.4 × 10¹¹ g T. testudinum leaves and 2.4 × 10¹¹ g S. filiforme leaves. We assessed the efficacy of rapid visual surveys for estimating abundance of seagrasses in south Florida by comparing these results to measures of leaf biomass for T. testudinum and S. filiforme. Our rapid visual surveys proved useful for quantifying seagrass abundance, and the data presented in this paper serve as a benchmark against which future change in the system can be quantified. Received: 30 January 2000 / Accepted: 24 July 2000     

Polonium-210 and lead-210 in Antarctic marine biota and sea water

Concentrations of the naturally-ocurring radionuclides ²¹⁰Po and ²¹⁰Pb were measured in krill (Euphausia superba), mesozooplankton, phytoplankton and sea water collected during the South African SIBEX cruise to the Antarctic in autumn 1984. The data reported constitute the first substantial measurements on ²¹⁰Po and ²¹⁰Pb in such samples in the Antarctic Ocean. The concentrations of ²¹⁰Po in mesozooplankton and phytoplankton are unexceptional in comparison with those from other oceans. The SIBEX E. superba, however, have higher levels of ²¹⁰Po than usually found in euphausiids. The ²¹⁰Po data, combined with reasonable estimates of biological quantitites such as the fractional assimilation, are used to obtain information about the diet of E. superba. It is suggested that the higher ²¹⁰Po in the SIBEX E. superba reflects a change from an almost entirely phytoplanktonic diet in summer to a more omnivorous diet as winter approaches. The data show that there are allometric relationships between the ²¹⁰Po content of euphausiids and animal size; these are discussed briefly. The limited sea-water data presented are characterized by unusually high ²¹⁰Po:²¹⁰Pb activity ratios and need further investigation.     

Temperature and plankton

The relationship between temperature and metabolism was studied in Artic copepods with regard to the concept of metabolic cold adaptation of polar poikilotherms. Temperature tolerance and respiration rates of the dominant copepods Calanus finmarchicus (Gunnerus), C. glacialis (Jaschnov), C. hyperboreus (Krøyer) and Metridia longa (Lubbeck), collected in Fram Strait, Greenland Sea, in July 1983, were studied at different temperatures. Temperature tolerance in the boreal C. finmarchicus was slightly higher than in the three Arctic species. Respiration rates at lower temperatures followed the Arrhenius equation in all species, with values for (temperature characteristics) between 11.05 and 22.95, corresponding to a Q₁₀ between 2.05 and 4.5. This increase in metabolic rate with rising temperature was not related to an increase of swimming activity, as was shown by videoanalysis. Activity was determined as average swimming speed and as frequency of certain locomotor patterns. Average swimming speed remained unchanged at all temperatures and was ca 1 cm s^-1 for all species, when only periods of active swimming were considered. The time spent with active swimming did not change with temperature in M. longa and C. finmarchicus, but decreased in c. glacialis. In C. hyperboreus it increased at 5°C and decreased again at higher temperatures. It is suggested that the increase in oxygen consumption is fully accounted for by the basal metabolism.     

Microbial responses to combined oxidation and catalysis treatment of 1,4-dioxane and co-contaminants in groundwater and soil

Post-treatment impacts of a novel combined hydrogen peroxide (H₂O₂) oxidation and WO_x/ZrO₂ catalysis used for the removal of 1,4-dioxane and chlorinated volatile organic compound (CVOC) contaminants were investigated in soil and groundwater microbial community. This treatment train removed ~90% 1,4-dioxane regardless of initial concentrations of 1,4-dioxane and CVOCs. The Illumina Miseq platform and bioinformatics were used to study the changes to microbial community structure. This approach determined that dynamic shifts of microbiomes were associated with conditions specific to treatments as well as 1,4-dioxane and CVOCs mixtures. The biodiversity was observed to decrease only after oxidation under conditions that included high levels of 1,4-dioxane and CVOCs, but increased when 1,4-dioxane was present without CVOCs. WO_x/ZrO₂ catalysis reduced biodiversity across all conditions. Taxonomic classification demonstrated oxidative tolerance for members of the genera Massilia and Rhodococcus, while catalyst tolerance was observed for members of the genera Sphingomonas and Devosia. Linear discriminant analysis effect size was a useful statistical tool to highlight representative microbes, while the multidimensional analysis elucidated the separation of microbiomes under the low 1,4-dioxane-only condition from all other conditions containing CVOCs, as well as the differences of microbial population among original, post-oxidation, and post-catalysis states. The results of this study enhance our understanding of microbial community responses to a promising chemical treatment train, and the metagenomic analysis will help practitioners predict the microbial community status during the post-treatment period, which may have consequences for long-term management strategies that include additional biodegradation treatment or natural attenuation.

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Energy budgets and feeding rates of Coryphaenoides acrolepis and C. armatus

This study develops energy budgets and estimates feeding rates for two macrourid fishes, Coryphaenoides acrolepis, dominant in the bathyal eastern North Pacific, and the abyssal cosmopolitan species, Coryphaenoides armatus. Daily energy expenditure by C. acrolepis was nearly twice that of C. armatus. C. acrolepis allocated nearly equal amounts of energy to metabolism and growth. Once sexual maturity was reached reproduction became the dominant energetic cost. Either these costs are necessary to retain adequate numbers of eggs and larvae on the continental slopes, or this fish does not reproduce on an annual basis and the calculated costs are an overestimate. C. armatus allocated relatively more energy to metabolism than growth. It may be semelparous, and this strategy would be of great energetic savings in its food-poor but stable environment. Individual daily ration for C. acrolepis decreased from 0.31% to 0.07% of body weight (BW) and for C. armatus from 0.12% to 0.02% BW with increasing fish length. These rates are substantially lower than those for fishes living in cold waters on the continental shelves. The population feeding rates for C. acrolepis ranged from 0.8 to 15 kg km^-2 day^-1 and for C. armatus from 5 to 2,800 g km^-2 day^-1. The scavenging behaviour of C. acrolepis was used to investigate the role of carrion as a food supply to the deep-sea benthos. It was estimated that the carrion eaten by C. acrolepis is equivalent to 0.04 mg C m^-2 day^-1 or only 0.2-0.4% of the average small particulate flux. Carrion consumption is important for scavengers like C. acrolepis, but it is not an important component of the carbon flux into the deep-sea benthic environment.     

Population structure and breeding biology of Pisidia longicornis and Porcellana platycheles

Quantitative sampling of littoral and sublittoral populations of Pisidia longicornis (L.) and a littoral population of Porcellana platycheles (Pennant) has been carried out over a 2 year period (1970/1972). On the shore, P. longicornis were most abundant at mean low water spring (MLWS), whereas P. platycheles were found mostly at lower mid-shore level. Differences were found between littoral and sublittoral P. longicornis. Sublittoral females are gravid for a slightly shorter period (April to September), carry more eggs, and are smaller than littoral females. It is suggested that their lifespan may also be shorter than that of littoral individuals. Young of both species settle in autumn and grow until December, when growth ceases until the following spring. Numbers decline in the summer months due to the mortality of older individuals. Many sublittoral and some littoral P. longicornis are sexually mature towards the end of their first year on the shore, and may copulate after the early spring moult and carry eggs in the subsequent summer months. P. platycheles appear to follow a similar basic pattern, but results are less clear.     

Primary production and heterotrophy of a pennate and a centric salt marsh diatom

Radionuclide labeled sodium bicarbonate and glucose were used to measure the rates of primary production and glucose uptake by Nitzschia obtusa var. undulata and Cymbella pusilla. The presence of glucose in the medium enhanced primary production in both diatom species. Uptake of glucose in C. pusilla was photoinhibited. A maximum of 9.3 nmol C mg dry wt^-1 h^-1 of glucose was taken up in the light without the presence of NaHCO₃ in the medium and with NaHCO₃ present the value was 18 nmol C mg dry wt^-1 h^-1. The ratio of inorganic carbon fixed to the total carbon budget (autotrophy and heterotrophy) was 0.51 for N. obtusa var. undulata and 0.62 for C. pusilla.