Growth and production of Sterechinus neumayeri (Echinoidea: Echinodermata) in McMurdo Sound,Antarctica

Population dynamics of Sterechinus neumayeri were investigated at four sites in McMurdo Sound: Cape Evans, McMurdo Station, East Cape Armitage and New Harbor. The annual formation of natural growth bands in the jaws of the Aristotle's lantern was verified by a tagging-recapture experiment. Growth functions based on natural growth bands indicated differences among stations but showed S. neumayeri to be a slow growing species, reaching its maximum diameter of 70 mm at an age of about 40 yr. Annual production ranged between 2.4 (C. Evans) and 0.65 g ash free dry mass m^-2 (New Harbor) and was related to differences in food conditions. More than 95% of total production was invested in reproduction, and less than 5% was invested in somatic growth. Consumption estimates for S. neumayeri showed this species to play a significant role in the benthic trophic web of McMurdo Sound.     

Oxygen microoptodes: a new tool for oxygen measurements in aquatic animal ecology

We describe two applications of a recently introduced system for very precise, continuous measurement of water oxygen saturation. Oxygen microoptodes (based on the dynamic fluorescence quenching principle) with a tip diameter of ~50 µm, an eight-channel optode array, an intermittent flow system, and online data registration were used to perform two types of experiments. The metabolic activity of Antarctic invertebrates (sponges and scallops) was estimated in respiration experiments, and, secondly, oxygen saturation inside living sponge tissue was determined in different flow regimes. Even in long-term experiments (several days) no drift was detectable in between calibrations. Data obtained were in excellent correspondence with control measurements performed with a modified Winkler method. Antarctic invertebrates in our study showed low oxygen consumption rates, ranging from 0.03-0.19 cm³ O₂ h^-1 ind.^-1. Oxygen saturation inside living sponge specimens was affected by flow regime and culturing conditions of sponges. Our results suggest that oxygen optodes are a reliable tool for oxygen measurements beyond the methodological limits of traditional methods.     

The trophic link between squid and the emperor penguin <Emphasis Type="Italic">Aptenodytes forsteri</Emphasis> at Pointe Géologie,Antarctica

Cephalopod beaks retrieved from stomachs of dead emperor penguin chicks at Pointe Géologie, Terre Adélie, provide information on taxonomic and size composition of the penguin’s squid diet, on the trophic range of the squid species preyed upon and on the fractional trophic impact of the penguin on the whole food web. Emperor penguins prey upon four squid species (Psychroteuthis glacialis, Kondakovia longimana, Gonatus antarcticus, Alluroteuthis antarcticus) and do not take squid larger than 480 mm mantle length. Larger squid live either below the penguin’s diving range or are beyond its handling capacity. Nitrogen stable isotope ratios indicate that squids cover a range of about two trophic levels (2.5–8‰ δ¹⁵N). The impact of the emperor penguin, however, concentrates on the upper part of this range, about 68% of its squid prey being >6‰ δ¹⁵N. The principal components of the emperor’s diet, fish, krill and squid, differ distinctly in average trophic level. Consequently the trophic position of the emperor penguin changes accordingly with diet composition and may differ by almost one trophic level between different emperor penguin colonies.     

Saving by freezing? Metabolic rates of<Emphasis Type="Italic"> Adamussium colbecki</Emphasis> in a latitudinal context

Standard metabolic rates of the endemic Antarctic scallop, Adamussium colbecki (Smith, 1902), were measured in austral summer and under simulated winter conditions. Average mass-specific metabolic rates were significantly different between "summer" (151.17±45.06 µl O ₂ g ^-1 h ^-1) and "winter" (106.52±39.65 µl O ₂ g ^-1 h ^-1) animals. The overall metabolic rates of A. colbecki are comparable to those of other Antarctic bivalve species, but well below those of temperate scallop species. Data for 24 scallop populations (13 species) from different latitudes give no evidence for elevated metabolic rates in A. colbecki as suggested by the concept of "metabolic cold adaptation". A world-wide comparison of metabolic rate and overall growth performance of scallops indicates that in the Antarctic scallop the energetic advantage of low basal metabolism does not counterbalance the disadvantage of the prolonged seasonal period of food shortage.     

Investigation of irradiated soil byproducts

The high dose irradiation of windblown soil deposited onto the surface of spent nuclear fuel is of concern to long-term fuel storage stability. Such soils could be exposed to radiation fields as great as 1.08 x 10(-3) C/kg-s (15,000 R/hr) during the 40-year anticipated period of interim dry storage prior to placement at the proposed national repository. The total absorbed dose in these cases could be as high as 5 x 10(7) Gy (5 x 10(9) rads). This investigation evaluated the potential generation of explosive or combustible irradiation byproducts during this irradiation. It focuses on the production of radiolytic byproducts generated within the pore water of surrogate clays that are consistent with those found on the Idaho National Engineering and Environmental Laboratory. Synthesized surrogates of localized soils containing combinations of clay, water, and aluminum samples, enclosed within a stainless steel vessel were irradiated and the quantities of the byproducts generated measured. Two types of clays, varying primarily in the presence of iron oxide, were investigated. Two treatment levels of irradiation and a control were investigated. An 18-Mev linear accelerator was used to irradiate samples. The first irradiation level provided an absorbed dose of 3.9 x 10(5)+/-1.4 x 10(5)Gy (3.9 x 10(7)+/-1.4 x 10(7) rads) in a 3-h period. At the second irradiation level, 4.8 x 10(5)+/-2.0 x 10(5)Gy (4.8 x 10(7)+/-2.0 x 10(7) rads) were delivered in a 6-h period. When averaged over all treatment parameters, irradiated clay samples with and without iron (III) oxide (moisture content = 40%) had a production rate of hydrogen gas that was a strong function of radiation-dose. A g-value of 5.61 x 10(-9)+/-1.56 x 10(-9) mol/J (0.054+/-0.015 molecules/100-eV) per mass of pore water was observed in the clay samples without iron (III) oxide for hydrogen gas production. A g-value of 1.07 x 10(-8)+/-2.91 x 10(-9) mol/J (0.103+0.028 molecules/100-eV) per mass of pore water was observed in the iron (III) oxide containing clay samples for hydrogen gas production. This value was noticeably larger when the samples were spiked with both KCl and KNO3 salts. The ratio of oxygen to nitrogen gas was observed to increase as a function of absorbed dose particularly in the presence of both KCl and KNO3 salts. The creation of radiolytic byproducts produced an observable but small increase in headspace pressure. Temperature increases during irradiation were not observed. Additionally, KCl and KNO3 salts added to the clays enhanced nitrite production as a function of radiation-dose and the type of clay considered. The addition of aluminum to these samples had no statistically discernable impact at the alpha = 0.05 level. Generation of the irradiation products, hydrogen peroxide and hydrogen gas also depended upon the type of clay irradiated and the presence of both KCl and KNO3 salts and the total dose received.     

Confidence limits for secondary production estimates: Application of the bootstrap to the increment summation method

In field studies, somatic production of animals is often calculated by means of the increment summation method, which is based on consecutive samples from the population. The main disadvantage of this method is the lack of any measurement of variability, therefore the statistical significance of the calculated production value is uncertain. This paper shows that in many cases a nonparametric statistical approach called the “bootstrap” can be used to overcome this problem. By means of this procedure, natural variability of production and production to biomass ratios can be assessed by 95% confidence intervals, standard deviation or related parameters from a sample of limited size.     

Individual growth and somatic production in<Emphasis Type="Italic"> Adelomelon brasiliana</Emphasis> (Gastropoda; Volutidae) off Argentina

Growth, age and somatic production of the benthic predator Adelomelon brasiliana were studied at the southern limit of its distribution on the South American Atlantic shelf. Stable oxygen isotope ratios confirmed annual formation of internal shell growth marks. Modal shell length of the population was 140 mm, while modal shell-free wet mass was 255 g. A logistics growth function (SL=186.28 mm, K=0.185, t₀=4.601) fitted 131 pairs of size-at-age data (25 shells) best. A. brasiliana is a very long-lived species, reaching up to 20 years of age. The maximum individual somatic production of 46 g shell-free wet mass year^–1 is attained at 145 mm shell length, which corresponds to about 12 years of age.Communicated by O. Kinne, Oldendorf/Luhe     

Growth and productivity of the high Antarctic Bryozoan Melicerita obliqua

We analysed growth of the Antarctic bryozoan Melicerita obliqua (Thornely, 1924) by x-ray photography and stable isotope analysis. M. obliqua colonies form one segment per year, thus attaining maximum length of about 200 mm within 50 years. In the Weddell and Lazarev Seas, annual production/biomass ratio of M. obliqua is 0.1 yr⁻¹, which is in the range of other Antarctic benthic invertebrate populations. Production amounts to 3.34 mg C_orgm⁻² yr⁻¹ and 90.6 mg ash m⁻² yr⁻¹ on the shelf (100 to 600 m water depth), and to 0.13 mg C_orgm⁻² yr⁻¹ and 36.8 mg ash m⁻² yr⁻¹ on the slope (600 to 1250 m water depth). Received: 27 February 1998 / Accepted: 8 May 1998     

Consumer-resource body-size relationships in natural food webs

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-'resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.