Movement and habitat use of the freshwater catfish (Tandanus tandanus) in a remnant floodplain wetland

Knowledge of the movement and habitat use of fishes is important in identifying and understanding the causes of population declines and predicting how populations are likely to respond to management interventions. In this study, radiotelemetry was used to examine the spring and summer movement and habitat use patterns of the freshwater catfish (Tandanus tandanus) in a remnant wetland to inform the development of recovery actions for this threatened species. Twenty-one adult fish were tagged and released within Tahbilk Lagoon, Victoria, Australia, in September 2009. Fish were located every 1-2 weeks between September 2009 and February 2010, a period which coincides with the spawning period for the species. Eleven of the fish were also tracked every 2 h for 68 consecutive hours in December 2009 to examine diel movements. The study revealed that freshwater catfish make extensive use of cover (e.g. wood and macrophytes) and typically have limited ranges (median total linear range and 90% linear range 599 and 173 m respectively), although they occasionally moved more extensively (up to 1.5 km) between floodplain and riverine habitats. Fish moved over much greater areas at night compared with during the day. There was also evidence of sex-specific variation in movement, with a trend for greater movement of female fish at night compared with males. The results of the study suggest that strategies that protect macrophyte and wood habitats and improve connectivity between riverine and floodplain habitats are likely to be important in maintaining and restoring remnant populations of this species.

Ecosystem responses to fire : identifying cross-taxa contrasts and complementarities to inform management strategies

Changes in fire frequency, extent, and intensity mean that understanding the effects of fire on plants and animals is a primary concern for ecologists and land managers. Given the potentially conflicting fire responses of species both within and across taxonomic groups, prescribing fire regimes based on the response of one or only a few species may have negative consequences for other species. Here, we integrate data collected from a series of independent but complementary studies spanning a 75 + year chronosequence in a semi-arid shrubland ecosystem in south-western Australia to consider how fire management can best promote biodiversity both within and across taxonomic groups (plants, birds, small mammals, and reptiles). Younger fire ages (6–14 years) contained sparse shrubs, large areas of bare ground, and lacked a distinct litter layer and canopy. The oldest vegetation (60–85 years) had a distinct canopy, a well-developed litter layer and cryptogamic crust, higher variability in patch width, and more woody debris. Plant species richness and diversity decreased with time since fire, whereas bird species richness and diversity increased with time since fire, and mammal and reptile species richness and diversity showed no trend. The composition of all four taxonomic groups varied according to time since fire and the presence of 11 species was confined above or below certain fire-age thresholds. Our results support the need to maintain a mix of both younger and older fire ages across the landscape to maximise species diversity, and highlight the particular importance of older fire ages for many species. Future fire management for biodiversity conservation will benefit from identifying and reconciling cross-taxa contrasts and complementarities.

Coarse-sand ice-rafted debris components and mass accumulation rates of ODP Site 152-918

To understand the late Cenozoic glacial history of the Northern Hemisphere, continuous long-term proxy records from climatically sensitive regions must be examined. Ice-rafted debris (IRD) from Ocean Drilling Program (ODP) Site 918, located in the Irminger Basin, is one such record. IRD in marine sediments is a direct indicator of the presence of glacial ice extending to sea level on adjacent landmasses, and, therefore, is an important paleoclimatic signal from the mid- to high latitudes. The IRD record at Site 918 is the first long-term ice-rafting record available for southeast Greenland, a region that may have been a key nucleation area for widespread glaciation during the late Cenozoic (Larsen et al, 1994, doi:10.2973/odp.proc.ir.152.1994). This data report presents the results of coarse sand-size IRD mass accumulation rate (MAR) analyses for Site 918 from the late Miocene through the Pleistocene. In addition, a preliminary analysis of IRD compositions is included. Detailed discussions of the local, regional, and global paleoclimatic implications of this data, and of the companion Site 919 Pleistocene IRD MAR data (Krissek, 1999, doi:10.2973/odp.proc.sr.163.118.1999), are in preparation. Such future work will include comparisons of these IRD MAR data sets to the Site 919 oxygen isotope stratigraphy developed by Flower (1998, doi:10.2973/odp.proc.sr.152.219.1998).

Chemical composition of basalts from coarse debris of the Kara Sea bottom sediments

Study of basaltic debris from the Kara Sea bottom has shown its similarity to traps of the Eastern Siberia in mineralogy, structures and chemical composition. In comparison with oceanic tholeiites, the source of traps and Kara Sea basin basaltic melts was enriched in REE and some other incompatible elements. K-Ar dating of two samples of supposed autochtonous location from the eastern part of the Kara Sea basin has shown 209 and 218 Ma - younger than traps (247-248 Ma). Origin of Siberian traps used to connect with action of the mantle plume (Iceland plume, according to geodinamic reconstruction). Our new age data may be interpreted as an evidence of the Siberian plate moving over the head of plume.

(Table 1) Grain size, sedimentation rates and accumulation rates of ODP Hole 152-919A coarse-sand ice-rafted debris

At mid- to high-latitude marine sites, ice-rafted debris (IRD) is commonly recognized as anomalously coarse-grained terrigenous material contained within a fine-grained hemipelagic or pelagic matrix (e.g., Conolly and Ewing, 1970; Ruddiman, 1977, doi:10.1130/0016-7606(1977)88<1813:LQDOIS>2.0.CO;2; Krissek, 1989, doi:10.2973/odp.proc.sr.104.114.1989; Jansen et al., 1990; Bond et al., doi:10.1038/360245a0, 1992; Krissek, 1995, doi:10.2973/odp.proc.sr.145.118.1995). The presence of such ice-rafted material is a valuable indicator of the presence of glacial ice at sea level on an adjacent continent, whereas the composition of the IRD can often be used to identify the location of the source area (e.g., Goldschmidt, 1995, doi:10.1016/0025-3227(95)00098-J). Because the amount of core recovered during Leg 163 was very limited, this shore-based, postcruise study focuses on materials recovered at a nearby site during Leg 152. In particular, this study examines sediments recovered at Site 919; these sediments were described as containing a significant ice-rafted component in the Leg 152 Initial Reports volume (Larsen, Saunders, Clift, et al., 1994, doi:10.2973/odp.proc.ir.152.1994). In this study, the sedimentary section from Site 919 has been examined with the goal of providing a detailed history of glaciations on Greenland and other landmasses adjacent to the Norwegian-Greenland Sea; this history ultimately will be calibrated using an oxygen isotope stratigraphy (Flower, 1998, doi:10.2973/odp.proc.sr.152.219.1998), although that calibration has not been completed at this time. Because ice-core studies of the Greenland Ice Sheet (GIS) have shown that the GIS changed dramatically, and in some cases extremely rapidly, during at least the last interglacial stage (GRIP Members, 1993, doi:10.1038/364203a0), a detailed IRD record from the Southeast Greenland margin should provide insight into the longer term behavior of this sensitive component of the Northern Hemisphere climate system.

Drilling into debris-rich basal ice at the bottom of the NEEM (Greenland) borehole

After the NEEM (Greenland) deep ice-core drilling was declared terminated with respect to developing stratigraphic climate reconstructions, efforts were turned toward collecting basal ice-sheet debris and, if possible, drilling into the bedrock itself. In 2010, several meters of banded debris-rich ice were obtained under normal ice-drilling operations with the NEEM version of the Hans Tausen (HT) drill, but further penetration was obstructed by a rock in the path of the drill head at 2537.36 m. During short campaigns in 2011 and 2012, attempts were made to penetrate further using various reinforced ice cutters mounted on the HT drill head, tailored to cut through rock. These had some success in penetrating coarse material, but produced severely damaged cutters. Additionally a 51 mm diameter diamond cutting tipped rock drill was adapted to fit the NEEM drill. With this device, several additional meters of core containing subglacial sediments, rocks and rock fragments were collected. With these tools 1.39 m of additional material were obtained during the 2011 field season, and 7.1 m during 2012. Subglacial water refreezing into the newly formed borehole hindered further penetration, and the bedrock interface was not reached before final closure of the NEEM Camp.