Andrén, Thomas; Norbäck Ivarsson, Lena; Andrén, Elinor
The Baltic Sea coastal zone contains over 20 % of all identified hypoxic sites worldwide and shows an increasing trend since 1950 (Conley et al. 2011). In the open Baltic Sea, hypoxia events are recorded during three time periods: about 8000-4000, 2000-800 cal. yr. BP, and from AD 1800 up to present, but in the coastal zone data on long-term trends are lacking (Zillén et al. 2008). Different views have been proposed of what caused the oscillation in the oxygen content at sea bottoms in the open Baltic Sea e.g. changes in agricultural practice, fluctuations in human population density and climate change. The role of humans and climate in driving the eutrophication and hypoxia in the Baltic Sea needs to be understood and there is an urgent need for increased knowledge of the historical extent of hypoxia and the driving forces for formation in the coastal zone. This project aims to disentangle the role of human induced and natural climate-driven processes that have resulted in times of eutrophication and hypoxia in the Baltic Sea during the last 2000 years. Research focus is put on the coastal zone and carefully selected estuaries along the Swedish east coast, where responses to changed human land-use can be expected to be first recorded. Eight sites, from the Stockholm archipelago to Bråviken, have been cored and sediments lithologically described and dated by radiocarbon using preferably terrestrial macrofossils. Preliminary results of age models, sedimentation rates, and lithologies will be presented. Lithological descriptions using laminated sediments as a proxy for hypoxic bottom water conditions will significantly increase the knowledge on the distribution of hypoxia and the extension of areas of laminated sediments in time and space in the coastal area. References: Conley, D.J., Carstensen, J., Aigars, J., Axe, P., Bonsdorff, E., Eremina, T., Haahti, B.-M., Humborg, C., Jonsson, P., Kotta, J., Lännegren, C., Larsson, U., Maximov, A., Rodriguez Medina, M
Rocha, C F D; Bergallo, H G
The gekkonid lizard Hemidactylus mabouia is an exotic species in Brazil and is found in different ecosystems. This species was recorded at Ilha Grande, RJ, one of the largest insular remains of the Atlantic Rainforest in Brazil. In this study, the occurrence of H. mabouia was determined throughout the island, including the rain forest, restinga and anthropic environments. We used the active search method in points along 19 trails that surround Ilha Grande. At each regular interval of 100 m, we searched for the presence of H. mabouia. The species was recorded in a total of 100 points among the 719 sampled and, in all cases, the occurrence of the lizard corresponded to points located in anthropic or perianthropic areas. As most of Ilha Grande is covered by dense tropical rain forest, we believe this has restricted the invasion of H. mabouia in natural environments within the island. PMID:21755162
Germer, Carina M; Tomaz, Juliana M; Carvalho, Ana F; Bassani, Rosana A; Bassani, José W M
The electrocardiogram (ECG) is the simplest and most effective non-invasive method to assess the electrical activity of the heart and to obtain information on the heart rate (HR) and rhythm. Because information on the HR of very small reptiles (body mass <10 g) is still scarce in the literature, in the present work we describe a procedure for recording the ECG in non-anesthetized geckos (Hemidactylus mabouia, Moreau de Jonnès, 1818) under different conditions, namely manual restraint (MR), spontaneous tonic immobility (TI), and in the non-restrained condition (NR). In the gecko ECG, the P, QRS and T waves were clearly distinguishable. The HR was 2.83 ± 0.02 Hz under MR, which was significantly greater (p < 0.001) than the HR under the TI (1.65 ± 0.09 Hz) and NR (1.60 ± 0.10 Hz) conditions. Spontaneously beating isolated gecko hearts contracted at 0.84 ± 0.03 Hz. The in vitro beating rate was affected in a concentration-dependent fashion by adrenoceptor stimulation with noradrenaline, as well as by the muscarinic cholinergic agonist carbachol, which produced significant positive and negative chronotropic effects, respectively (p < 0.001). To our knowledge, this is the first report on the ECG morphology and HR values in geckos, particularly under TI. The methodology and instrumentation developed here are useful for non-invasive in vivo physiological and pharmacological studies in small reptiles without the need of physical restraint or anesthesia. PMID:25395252
Novotny, Jerry F.; Macy, Thomas L.; Gardenier, James T.; Beeman, John W.
Pen rearing studies during 1986 completed the second of three years intended for rearing and releasing upriver bright fall chinook salmon (Oncorhynchus tshawytscha) from two study sites, a backwater and a pond, adjacent to the Columbia River; both areas are located in the Jonn Day Reservoir. Results of this study in 1984 and 1985 showed that fish could be successfully reared in net pens and that growth and physiological development of the off-station reared fish proceeded at a faster rate than in fish reared at a hatchery. Transfer of fish from the hatchery to off-station sites at Social Security Pond (pond) and Rock Creek (backwater) during early March increased the period of rearing in 1986 by about four weeks. The increased period of rearing allowed all treatments of fed fish to reach a minimum weight of YU fish/lb by release. Differences in growth of fed fish between regular density treatments and additional, high density treatments (double and triple the regular densities) were not significantly different (P > 0.05), but growth of all fed fish reared off-station was again significantly better than that of hatchery reared fish (P < 0.05), Mortalities in all groups of fed fish were low. Physiological development of fed fish was similar in all treatments. At release, development of fish at Social Security Pond appeared to be somewhat ahead of fish at Rock Creek on the same dates however, none of the groups of fed fish achieved a high state of smoltification by release. Unfed fish grew poorly over the redring period, and at release were significantly smaller than either fed groups at the off-station sites, or the control groups reared at the hatchery (P < 0.05). Development of unfed fish toward smoltification was much slower than of fed fish. Mortality of all groups of unfed fish, including the barrier net, was relatively low. Health of all fish reared off-station remained good over the rearing period, and no outbreaks of disease were noted. On-site marking and