Tools for assessing the impact of climate change on freshwater fish populations

We identify and discuss ways to use existing information on the thermal ecology of freshwater fishes to assess the potential impact of climate change on wild populations of these organisms. Two primary questions are identified: (i) how do aquatic habitats change in response to atmospheric climate change? (ii) how do fish respond to habitat change at both the individual and population levels? In lakes, climate warming will lead to higher surface water temperatures, longer ice-free periods, and longer periods of thermal stratification. In rivers, climate warming will lead to higher groundwater temperatures with corresponding increases in both summer and winter temperatures, from headwaters to mouth. We describe several methods for predicting the biological effects of these changes in habitat. We examine the use of bioenergetic models to predict the impact of climate change on the growth of individual fish. We examine the use of thermal habitat models to assess the impact of climate change on population abundance. We examine the use of life cycle models to assess the impact of climate change on the zoogeographic distribution of species. Finally, we identify new research required to further develop these methods.     

Assessing potential effects of global climate change on tropical freshwater fishes

Climate change will affect both the quality and the quantity of water in freshwater environments. Changes in air temperature and precipitation will alter the annual water temperature cycle and the annual water level cycle. Initial assessments of the effects of climate change on freshwater fishes of North America have focused on the potential thermal effects of climate change because of the strong influence of water temperature on the life histories of temperate fishes. Paralleling the influence of water temperature on temperate fishes is the influence of water quantity on tropical fishes, especially on riverine fishes. The extreme seasonal fluctuations in discharge of tropical rivers, through the effects on fish habitat availability and habitat conditions, have produced a range in preferred habitat types among riverine fishes. We suggest that initial assessment of potential effects of climate change on tropical freshwater fishes should focus on changes to water quantity variables in riverine environments. Assessments should begin at a coarse level of resolution. A useful starting point would be comparative analyses of the sensitivity of blackfishes and whitefishes to changes in habitat availability, oxygen levels and desiccation stress that will likely accompany changes in the seasonal flow regimes of tropical rivers.This paper formed part of a symposium held at the XVII Pacific Science Congress in Honolulu, Hawaii June 1991. The theme of the symposium was Aspects of Global Environmental Change: Freshwater Ecosystems which focused on southern Pacific environments.     

MIDI – the 10 μm instrument on the VLTI

After more than five years of preparation, the mid-infrared interferometric instrument MIDI has been transported to Paranal where it will undergo testing and commissioning on theVery Large Telescope Interferometer VLTI from the end of 2002through large part of this year 2003. Thereafter it will be available as a user instrument to perform interferometric observations over the8 μm–13 μm wavelength range, with a spatial resolution of typically 20 milliarcsec, a spectral resolution of up to 250, and an anticipated point source sensitivity of N = 3–4 mag or 1–2.5 Jy for self –fringe tracking, which will be the only observing mode during the first months of operation. We describe the layout of the instrument, laboratory tests, and expected performance, both for broadband and spectrally resolved observing modes. We also briefly outline the planned guaranteed time observations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Scientific and technical results from VINCI using coherent estimation of fringe visibility

Although primarily intended as a test and alignment instrument in order to commission the VLTI, VINCI has taken useful scientific data in its first year and a half of operation. Our results employ coherent integration of fringe visibility in which the actual amplitudes of the raw scans are combined linearly after correcting for the position of the fringe within each scan. In addition to reducing the effect of noise compared to incoherent integration, the result contains a broader range of information, including an estimate of the complex visibility spectrum. Such an estimator is thus sensitive to instrumental phase and spectral characteristics, including the variable component of dispersion introduced by the excess air paths in the delay lines. Calibration of such instrumental effects demonstrates the ability to detect source phase at a fine level as will be required for direct interferometric detection of extra solar planets. We present diameters for five stars obtained by observing the visibility null in their correlated spectra. Using coherent integration we have also observed the peculiar correlated spectra seen in many Mira variables, possibly due to changes in the apparent diameter with wavelength. Calibration of the zero-baseline power from o Ceti is used with other interferometric observations of this star over a period of 90 days to plot diameter variations associated with its pulsation cycle. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Solar Minimum Active Region 7978, Its X2.6/1B Flare,CME, and Interplanetary Shock Propagation of 9 July 1996

The first X-class flare in four years occurred on 9 July 1996. This X2.6/1B flare reached its maximum at 09:11 UT and was located in active region 7978 (S10° W30°) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio observations of the type II shock, and GOES disk-integrated soft X-ray flux during an extended period that included energy build-up in this active region.The LASCO coronagraphs measured a significant coronal mass ejection (CME) on the solar west limb beginning on 8 July at about 09:53 UT. The GOES 8 soft X-ray flux (0.1–0.8 nm) had started to increase on the previous day from below the A-level background (10^-8 W m^-2). At the start time of the CME, it was at the mid-B level and continued to climb. This CME is similar to many events which have been seen by LASCO and which are being interpreted as disruption of existing streamers by emerging flux ropes.LASCO and EIT were not collecting data at the time of the X-flare due to a temporary software outage. A larger CME was in progress when the first LASCO images were taken after the flare. Since the first image of the 'big' CME was obtained after the flare's start time, we cannot clearly demonstrate the physical connection of the CME to the flare. However, the LASCO CME data are consistent with an association of the flare and the CME. No eruptive filaments were observed during this event.We used the flare evidence noted above to employ in real time a simplified Shock-Time-of-Arrival (STOA) algorithm to estimate the arrival of a weak shock at the WIND spacecraft. We compare this prediction with the plasma and IMF data from WIND and plasma data from the SOHO/CELIAS instrument and suggest that the flare - and possibly the interplanetary consequences of the 'big' CME - was the progenitor of the mild, high-latitude, geomagnetic storm (daily sum of Kp=16+, Ap=8) on 12 July 1996. We speculate that the shock was attenuated enroute to Earth as a result of interaction with the heliospheric current/plasma sheet.presently at High Altitude Observatory, Boulder, CO80309, U.S.A.presently at Naval Research Laboratory, Washington DC, 20375, U.S.A.