The timing of sea ice formation and exposure to photosynthetically active radiation along the Western Antarctic Peninsula

Understanding the flow of solar energy into ecosystems is fundamental to understanding ecosystem productivity and dynamics. To gain a better understanding of this fundamental process in the Antarctic winter sea ice, we produced a model that estimates the time-integrated exposure of seasonal Antarctic sea ice to PAR through the use of remotely sensed sea ice concentrations, sea ice movement and spatially distributed PAR calculations that account for cloud cover and have applied this model over the past three decades. The resulting spatially distributed estimates of sea ice exposure to PAR by mid-winter are evaluated in context of changes in the timing of sea ice formation that have been documented along the Western Antarctic Peninsula (WAP) region and its potential effects on the variation (seasonal and inter-annual) in the accumulation of sea ice algae in this region. The analysis shows the ice pack is likely to have large inter-annual variations (10–100 fold) in productivity throughout the autumn to winter transition in the sea ice along the WAP. Moreover, the pack ice is likely to have spatial structure in regards to biological processes that cannot be determined from analysis of sea ice concentration information alone. The resulting inter-annual variations in winter processes are likely to affect the dynamics of Antarctic krill (Euphausia superba).     

Characterization of the genetic diversity of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> in São Paulo city,Brazil

Background

Tuberculosis is a major health problem in São Paulo, Brazil, which is the most populous and one of the most cosmopolitan cities in South America. To characterize the genetic diversity of Mycobacterium tuberculosis in the population of this city, the genotyping techniques of spoligotyping and MIRU were applied to 93 isolates collected in two consecutive years from 93 different tuberculosis patients residing in São Paulo city and attending the Clemente Ferreira Institute (the reference clinic for the treatment of tuberculosis).

Findings

Spoligotyping generated 53 different spoligotype patterns. Fifty-one isolates (54.8%) were grouped into 13 spoligotyping clusters. Seventy- two strains (77.4%) showed spoligotypes described in the international databases (SpolDB4, SITVIT), and 21 (22.6%) showed unidentified patterns. The most frequent spoligotype families were Latin American Mediterranean (LAM) (26 isolates), followed by the T family (24 isolates) and Haarlem (H) (11 isolates), which together accounted for 65.4% of all the isolates. These three families represent the major genotypes found in Africa, Central America, South America and Europe. Six Spoligo-International-types (designated SITs by the database) comprised 51.8% (37/72) of all the identified spoligotypes (SIT53, SIT50, SIT42, SIT60, SIT17 and SIT1). Other SITs found in this study indicated the great genetic diversity of M. tuberculosis, reflecting the remarkable ethnic diversity of São Paulo city inhabitants. The MIRU technique was more discriminatory and did not identify any genetic clusters with 100% similarity among the 93 isolates. The allelic analysis showed that MIRU loci 26, 40, 23 and 10 were the most discriminatory. When MIRU and spoligotyping techniques were combined, all isolates grouped in the 13 spoligotyping clusters were separated.

Conclusions

Our data indicated the genomic stability of over 50% of spoligotypes identified in São Paulo and the great genetic diversity of M. tuberculosis isolates in the remaining SITs, reflecting the large ethnic mix of the São Paulo city inhabitants. The results also indicated that in this city, M. tuberculosis isolates acquired drug resistance independently of genotype and that resistance was more dependent on the selective pressure of treatment failure and the environmental circumstances of patients.

     

Working with living krill - the people and the places

The fascination of Antarctic scientists with Antarctic krill and their capabilities has a long and varied history, and prompted many scientists to maintain and manipulate krill under laboratory conditions. Starting in the Discovery era with Mackintosh at the King Edward Point labs on South Georgia, 1930, scientists have collected krill from sailing vessels, small boats, inflatable zodiacs and large ice-breaking vessels. Krill have been maintained in small and large jars, deep rectangular tanks, large round tanks and in flow-through and recycling systems. They have been maintained both on board research vessels and in laboratories, in flowing seawater systems at ambient conditions and in temperature-controlled environmental rooms. A few researchers have transported living krill back to their home laboratories, for example tropical laboratories in Japan (Murano) and Australia (Ikeda), temperate laboratories (Nicol) in Australia, a northern European laboratory in Germany (Marschall) and a sunny maritime laboratory in California (Ross and Quetin). The goals have been varied: short-term experiments to understand in situ physiological rates, long-term experiments to test the effects of manipulations or controlled changes in environmental conditions, and behavioral responses. We take you on a brief historical tour as we trace the lineage of modern day research on living Antarctic krill.     

Variations in cruropedal musculature

The comparative anatomy of primate musculature has been established frequently from single specimens or small samples which are assumed to be typical for their species. However, a series of dissections of platyrrhine monkeys reported here reveals considerable variation within species and genera. Selected muscles of the leg and foot were examined and compared for discrete variations in attachments. The results were supplemented by observations in the anatomical literature for these and other primates. The range of variation reported across the order also presents itself as widespread polymorphism within most taxonomic groups, down to the species level. Since correlations with phylogeny and positional behavior are expressed only weakly, adaptationist explanations can account for only a part of the variation. Functional redundancy among the muscles supports the conclusion that the behavioral significance of the variations is slight. It is apparent that both genetic and nongenetic factors influence muscle form, and it is likely that observed polymorphisms have been characteristic of populations throughout primate evolution. Therefore, traits involving muscular form, especially as observed on small samples, within species, should be used cautiously in phyletic and adaptationist analyses.     

Effects of nutrient enrichment and biochemical composition of diets of Palmaria mollis on growth and condition of Japanese abalone, Haliotis discus hannai and red abalone, Haliotis rufescens

Two growth experiments were conducted with juvenile red abalone, Haliotis rufescens and Japanese abalone, Haliotis discus hannai. The first experiment was set up to determine if nutrient levels used for co-culture of the Rhodophyte, Pacific dulse (Palmaria mollis) directly affected abalone growth. No significant differences (ANOVA; P=0.117) were found in growth of abalone cultured in either ambient seawater alone or seawater supplemented with different NaNO₃ loads (1176, 1765, 2353, and 2942 μM day⁻¹ NO₃-N), NaH₂PO₄ (83.3 μM day⁻¹ PO₄⁻), and a modified version of Guillard and Ryther's [Gran. Can. J. Microbiol. 8, (1962) 229] f medium containing Fe, Zn, Mn, Cu, Mo, and Co.The second experiment was designed to determine the effect of different nutrient levels on the nutritional value of P. mollis when fed to abalone. P. mollis was cultured with different NaNO₃ loads (1176, 1765, 2353, and 2942 μM day⁻¹ NO₃-N) and NaH₂PO₄ (83.3 μM day⁻¹ PO₄⁻) in the presence or absence of f medium trace metals (Fe, Zn, Mn, Cu, Mo, and Co). H. discus hannai showed the highest LGR and SGR when fed on P. mollis supplemented with nitrate loads ranging from 1176 to 2353 μM day⁻¹ NO₃-N. In contrast, H. rufescens showed the highest linear growth rate (LGR) when fed on P. mollis supplemented with higher nitrate loads of 2353 to 2942 μM day⁻¹ NO₃-N, while nitrate load had no significant effect on specific growth rate (SGR). Both abalone species grew better on P. mollis supplied with 0.75f+Zn (day⁻¹) metal solution [Gran. Can. J. Microbiol. 8 (1962) 229] compared to those without trace metal additions, with H. discus hannai showing a further improvement in food conversion efficiencies (FCE).The present work shows that understanding and manipulating the culture environment of P. mollis can significantly affect growth, FCE, and daily food consumption (DFC) of H. discus hannai and H. rufescens.     

Induced loss of Syk in human basophils by non-IgE-dependent stimuli

In the general population, Syk expression in human basophils is highly variable and correlates well with the IgE-mediated responsiveness of these cells. Previous studies established that IgE-mediated stimulation results in loss of Syk expression. The current studies investigated whether stimulation through other receptors results in loss of Syk. Two classes of stimulation were examined, those that operate through the kinase Syk and those that operate through a GTP-binding protein. These studies demonstrated that aggregation of leukocyte Ig-like receptor LILRA-2 resulted in phosphorylation of Syk and c-Cbl, was inhibited by a third generation Syk inhibitor with an expected IC(50), and induced histamine release in strict proportion to release induced by anti-IgE Ab. Stimulation of LILRA-2 for 18 h resulted in modest loss of Syk that correlated with the more profound loss of Syk induced by anti-IgE Ab. Human recombinant histamine-releasing factor has also recently been shown to induce Syk phosphorylation and in the current studies has also been shown to induce loss of Syk in 18-h cultures. fMLP stimulation for 18 h was also found to induce modest loss of Syk. fMLP induced phosphorylation of c-Cbl that was sustained for at least 45 min. Phosphorylation of c-Cbl was inhibited by a Syk kinase inhibitor but with an IC(50) that was not consistent with Syk activity, suggesting another kinase was responsible for Cbl phosphorylation following fMLP. These studies demonstrate that it is possible to induce the loss of Syk expression in human basophils by a non-IgE-dependent mechanism and even by a mechanism that does directly involve Syk in the reaction complex.     

Vegetation, landscape and human activity in Midland Ireland: mire and lake records from the Lough Kinale-Derragh Lough area, Central Ireland

A high-resolution pollen record for the Holocene has been obtained from Derragh Bog, a small raised mire located on a peninsula in Lough Kinale-Derragh Lough, in Central Ireland as part of the Discovery Programme (Ireland) Lake Settlements Project. The data are compared with two lower resolution diagrams, one obtained from Derragh Lough and one from adjacent to a crannog in Lough Kinale. The general trends of vegetation change are similar and indicate that landscape-scale clearance did not occur until the Medieval period (ca. a.d. 800–900). There are, however, significant differences between the diagrams due primarily to core location and taphonomy, including pollen source area. Only the pollen profile from Derragh Bog reveals an unusually well represented multi-phase primary decline in Ulmus ca. 3500–3100 b.c. (4800–4750¹⁴C b.p.) which is associated with the first arable farming in the area. The pollen diagram indicates a rapid, and almost complete, clearance of a stand of Ulmus with some Quercus on the Derragh peninsula, arable cultivation in the clearing and then abandonment by mobile/shifting late Neolithic farmers. Subsequently there are a number of clearance phases which allow the colonisation of the area by Fraxinus and are probably associated with pastoral activity. The pollen sequence from adjacent to a crannog in Lough Kinale shows clear evidence of the construction and use of the crannog for the storage of crops (Hordeum and Avena) whereas the Derragh Bog diagram and the diagram from Derragh Lough reflect the growth of the mire. This study reveals that in this landscape the record from a small mire shows changes in prehistoric vegetation caused by human agriculture that are not detectable in the lake sequences. Although in part this is due to the higher temporal resolution and more consistent and complete chronology for the mire, the most important factor is the closer proximity of the raised mire sequence to the dry land. However, the pollen sequence from adjacent to a crannog does provide detailed evidence of the construction and function of the site. It is concluded that in order to ascertain a complete picture of vegetation changes in a lowland shallow lake-dominated landscape, cores from both the lake and surrounding small mires should be analysed.     

Energetic demands of larval krill, Euphausia superba, in winter

Metabolic rates of larval and juvenile krill, Euphausia superba, were measured on board ship during three winter cruises west of the Antarctic Peninsula (June-July 1987, June 1993, and June 1994), and also under different temperature regimes and feeding conditions during long-term maintenance in the laboratory (Palmer Station, winter 1993). A mean oxygen consumption and nitrogen excretion ratio of 31.1 measured on board ship at ambient ocean temperatures suggested that larval and juvenile krill from ice-covered waters were primarily herbivorous. Results from both shipboard and laboratory experiments demonstrated that oxygen consumption increased with temperature, but that larvae subjected to acute temperature increases exhibited higher rates. Experiments conducted at near ambient water temperatures for winter were also conducted to test the effect of habitat on the energy requirements of larval and juvenile krill. A comparison of the field and laboratory studies conducted at −1.5 to −1.8 °C showed that larvae from ice-covered waters and fed larvae in the laboratory had oxygen consumption rates significantly higher than those of larvae collected from open, i.e. ice-free, water and those starved in the laboratory. Results of the comparison lend support to the concept that in winter, larval and juvenile krill are better fed in ice-covered waters than in open water, and to the hypothesis that ice biota in the pack ice are an important food resource in winter for larval and juvenile krill.     

Species‐specific responses to climate change and community composition determine future calcification rates of Florida Keys reefs

Anthropogenic climate change compromises reef growth as a result of increasing temperatures and ocean acidification. Scleractinian corals vary in their sensitivity to these variables, suggesting species composition will influence how reef communities respond to future climate change. Because data are lacking for many species, most studies that model future reef growth rely on uniform scleractinian calcification sensitivities to temperature and ocean acidification. To address this knowledge gap, calcification of twelve common and understudied Caribbean coral species was measured for two months under crossed temperatures (27, 30.3 °C) and CO₂ partial pressures (pCO₂) (400, 900, 1300 μatm). Mixed‐effects models of calcification for each species were then used to project community‐level scleractinian calcification using Florida Keys reef composition data and IPCC AR5 ensemble climate model data. Three of the four most abundant species, Orbicella faveolata, Montastraea cavernosa, and Porites astreoides, had negative calcification responses to both elevated temperature and pCO₂. In the business‐as‐usual CO₂ emissions scenario, reefs with high abundances of these species had projected end‐of‐century declines in scleractinian calcification of >50% relative to present‐day rates. Siderastrea siderea, the other most common species, was insensitive to both temperature and pCO₂ within the levels tested here. Reefs dominated by this species had the most stable end‐of‐century growth. Under more optimistic scenarios of reduced CO₂ emissions, calcification rates throughout the Florida Keys declined <20% by 2100. Under the most extreme emissions scenario, projected declines were highly variable among reefs, ranging 10–100%. Without considering bleaching, reef growth will likely decline on most reefs, especially where resistant species like S. siderea are not already dominant. This study demonstrates how species composition influences reef community responses to climate change and how reduced CO₂ emissions can limit future declines in reef calcification.