Assimilation efficiency of the antarctic marine isopod Glyptonotus antarcticus

first_imgWhen fed shrimp every 2 days, the isopod Glyptonotus antarcticus Eights assimilated over 90% of the ingested food. Errors in this estimate due to loss of food material during maceration by G. antarcticus were investigated and allowed for. These results are discussed in relation to data for other isopods and marine invertebrates.last_img

Climate change and the evolution of high-latitude terrestrial vegetation and floras

first_imgOur understanding of polar vegetation and climate through time has expanded enormously in the past five years as a consequence of improved logistics, detailed studies of plant fossils in their proper sedimentological context, and the development of sophisticated physiognomic methods for extracting the climate signal present in plant fossil assemblages. These revelations are particularly timely in that climate change is most strongly expressed at the poles, and polar conditions play a critical role in determining global climate. By studying the evolution and change in polar vegetation, valuable insights on possible future biotic responses to global warming can be obtained.last_img read more

Establishing a postgraduate qualification in remote health

first_imgThe British Antarctic Survey (BAS) provides medical care for the scientists and support staff working on British scientific bases and research vessels in the Antarctic. The BAS directs significant resources towards medical research, so a doctor who does not complete the research component of the programme of training and medical duties represents a partially wasted investment. Additionally, the professional experience gained by the doctor is appropriate for a postgraduate qualification. For these reasons, the training, clinical placement and research undertaken by doctors were formalized as a masters degree in 1992. The objectives of the MSc degree were to optimize the benefits of the training and research for Antarctic doctors and their patients, and to improve the quality of the research output. In the three years before the degree was introduced, only 25% of doctors produced a useful research output. Following the introduction of the MSc, this figure rose to 88%.last_img read more

Is there a Universal Temperature Dependence of metabolism?

first_imgIn a challenging and provocative paper Gillooly et al. (2001) have proposed that the metabolism of all organisms can be described by a single equation, * Q = b0M3/4e−E/kT, where Q = metabolic rate, M = body mass, E = the activation energy of metabolism (defined as the average activation energy for the rate-limiting enzyme catalysed biochemical reactions of metabolism), T = absolute temperature, k = Boltzmann’s constant and b0 is a normalization constant independent of M and T. In deriving this equation Gillooly et al. (2001) start from the premise that metabolic rate scales with body mass as Q ∝ M3/4, based on the fractal-like design of exchange surfaces and distribution networks in plants and animals (West, Brown & Enquist 1997, 1999a,b). These arguments have stimulated some criticism (see for example Dodds, Rothman & Weitz 2001) but here I will concentrate on the derivation of the second part of the equation, namely the temperature dependence term. Gillooly et al. (2001) called the temperature dependence term of this equation the Universal Temperature Dependence (UTD) of metabolism. Although there have been many statistical descriptions of the relationship between size, temperature and metabolism since the classic work of Hemmingsen (1950, 1960) and Kleiber (1950, 1961), the UTD differs from these in being explicitly derived from first principles, in the sense that the formulation of the temperature dependence term is derived from classical statistical thermodynamics. The UTD has subsequently been incorporated into explanations of developmental time in all organisms, and macroecological patterns including global-scale analyses of diversity and population density (Allen, Brown & Gillooly 2002; Belgrano et al. 2002; Gillooly et al. 2002). Here I examine the assumptions underlying the formulation of the UTD, and test the relationship with a carefully assembled data set for teleost fish. In doing so I have distinguished between two philosophically different forms of the UTD, both of which are discussed but not explicitly distinguished by Gillooly et al. (2002). The first is where metabolic rate is determined mechanistically by temperature alone; this might be termed the hard UTD hypothesis. In the second form the UTD is simply a parameter-sparse statistical model describing the relationship between temperature and metabolic rate; this is the soft UTD hypothesis.last_img read more

Palaeoecological tools for improving the management of coastal ecosystems: a case study from Lake King (Gippsland Lakes) Australia

first_imgSince European settlement began over 200 years ago, many southeast Australian coastal lakes and lagoons have experienced substantial human impacts, including nutrient enrichment. Present day management and conservation efforts are often hampered by a lack of data on pre-impact conditions. We used a palaeoecological approach at Lake King, Gippsland Lakes, southeast Australia in order to determine its pre-impact condition and to establish the nature and direction of subsequent environmental changes, including responses to the construction of a permanent entrance to the sea in 1889. A 120 cm sediment core was analysed for diatoms, chlorophyll a, total carbon, nitrogen and sulphur, and dated using Pb-210. Past phosphate and salinity concentrations were reconstructed using diatom-phosphate and diatom-salinity transfer functions developed from a calibration set based on 53 sites from 14 southeast Australian coastal lakes and lagoons. Results show changes in the diatom assemblage that record a shift from a brackish-water to marine diatom flora since construction of the permanent entrance. Phosphate concentrations increased at the same time and experienced major peaks in the 1940s and 1950s to > 100 mu g/l. Chlorophyll a concentrations were generally below 24 mu g/l/gTOC in the core, but there has been a clear increase since the 1980s, peaking at 120 mu g/l/gTOC, likely associated with a recorded increase in the frequency of nuisance algal blooms. These results indicate that the Lake King environment is now very different to that present during early European settlement. We conclude that by identifying the nature and direction of environmental change, palaeoecological studies can contribute towards developing realistic and well-informed management, conservation and restoration strategies in Australianlast_img read more

Freeze tolerance, supercooling points and ice formation: comparative studies on the subzero temperature survival of limno-terrestrial tardigrades

Many limno-terrestrial tardigrades live in unstable habitats where they experience extreme environmental conditions such as drought, heat and subzero temperatures. Although their stress tolerance is often related only to the anhydrobiotic state, tardigrades can also be exposed to great daily temperature fluctuations without dehydration. Survival of subzero temperatures in an active state requires either the ability to tolerate the freezing of body water or mechanisms to decrease the freezing point. Considering freeze tolerance in tardigrades as a general feature, we studied the survival rate of nine tardigrade species originating from polar, temperate and tropical regions by cooling them at rates of 9, 7, 5, 3 and 1 degrees Ch(-1) down to -30 degrees C then returning them to room temperature at 10 degrees Ch(-1). The resulting moderate survival after fast and slow cooling rates and low survival after intermediate cooling rates may indicate the influence of a physical effect during fast cooling and the possibility that they are able to synthesize cryoprotectants during slow cooling. Differential scanning calorimetry of starved, fed and cold acclimatized individuals showed no intraspecific significant differences in supercooling points and ice formation. Although this might suggest that metabolic and biochemical preparation are non-essential prior to subzero temperature exposure, the increased survival rate with slower cooling rates gives evidence that tardigrades still use some kind of mechanism to protect their cellular structure from freezing injury without influencing the freezing temperature. These results expand our current understanding of freeze tolerance in tardigrades and will lead to a better understanding of their ability to survive subzero temperature conditions. read more

Nuculidae (Bivalvia) in the Cape Melville Formation, King George Island, Antarctica, with an overview of the bivalve fauna

first_imgNuculid bivalves of the Cape Melville Formation (Early Miocene, King George Island)are reviewed. Ten bivalve taxa are listed from the formation in the families Nuculidae (two species),Sareptidae, Malletiidae, Limopsidae (two species), Limidae, Pectinidae, Hiatellidae, and Periplomatidae.The Nuculidae consist of two species of Leionucula Quenstedt, 1930. One of these, L. melvilleana n. sp., isdescribed and the other consists of the two species named previously by Anelli et al. (2006), which aredemonstrated to be synonymous and are assigned to the species Leionucula frigida (Anelli, Rocha-Campos,Santos, Perinotto & Quaglio 2006). This assemblage, dominated by protobranchs (89% of specimens), isa typical fauna of offshore soft substrates, with a few specimens transported from hard substrates nearby.The diversity of Nuculidae has decreased in the Antarctic region through the Cenozoic.last_img read more

Oceanographers’ contribution to climate modelling and prediction: progress to date and a future perspective

first_imgThe ocean plays an essential role in determining aspects of the climate through its influence on coupled processes involving the atmosphere, cyrosphere and biogeochemistry,including budgets of heat and carbon dioxide and sea-level rise. Here, the key developments in ocean modelling over the past 20 years are reviewed and the prospects for the next 20 years are outlined, considering a hierarchy of idealized, conceptual and realistic modelling frameworks. It is emphasized that any long-term modelling strategyneeds to be underpinned and complemented by fundamental theoretical and observational research activities. The need to be aware of the societal and technological drivers thatwill shape future research directions is also articulated.last_img read more

Detection and quantification of oil under sea ice: the view from below

first_imgTraditional measures for detecting oil spills in the open-ocean are both difficult to apply and less effective in ice-covered seas. In view of the increasing levels of commercial activity in the Arctic, there is a growing gap between the potential need to respond to an oil spill in Arctic ice-covered waters and the capability to do so. In particular, there is no robust operational capability to remotely locate oil spilt under or encapsulated within sea ice. To date, most research approaches the problem from on or above the sea ice, and thus they suffer from the need to ‘see’ through the ice and overlying snow. Here we present results from a large-scale tank experiment which demonstrate the detection of oil beneath sea ice, and the quantification of the oil layer thickness is achievable through the combined use of an upward-looking camera and sonar deployed in the water column below a covering of sea ice. This approach using acoustic and visible measurements from below is simple and effective, and potentially transformative with respect to the operational response to oil spills in the Arctic marine environment. These results open up a new direction of research into oil detection in ice-covered seas, as well as describing a new and important role for underwater vehicles as platforms for oil-detecting sensors under Arctic sea ice.last_img read more

No ocean acidification effects on shell growth and repair in the New Zealand brachiopod Calloria inconspicua (Sowerby, 1846)

first_imgSurface seawaters are becoming more acidic due to the absorption of rising anthropogenic CO2. Marine calcifiers are considered to be the most vulnerable organisms to ocean acidification due to the reduction in the availability of carbonate ions for shell or skeletal production. Rhychonelliform brachiopods are potentially one of the most calcium carbonate-dependent groups of marine organisms because of their large skeletal content. Little is known, however, about the effects of lowered pH on these taxa. A CO2 perturbation experiment was performed on the New Zealand terebratulide brachiopod Calloria inconspicua to investigate the effects of pH conditions predicted for 2050 and 2100 on the growth rate and ability to repair shell. Three treatments were used: an ambient pH control (pH 8.16), a mid-century scenario (pH 7.79), and an end-century scenario (pH 7.62). The ability to repair shell was not affected by acidified conditions with >80% of all damaged individuals at the start of the experiment completing shell repair after 12 weeks. Growth rates in undamaged individuals >3 mm in length were also not affected by lowered pH conditions, whereas undamaged individuals <3 mm grew faster at pH 7.62 than the control. The capability of C. inconspicua to continue shell production and repair under acidified conditions suggests that this species has a robust control over the calcification process, where suitable conditions at the site of calcification can be generated across a range of pH conditions.last_img read more