Spawning time and early life history of Murray cod, <Emphasis Type="Italic">Maccullochella peelii</Emphasis> (Mitchell) in an Australian river

Synopsis I investigated aspects of the early life history of Murray cod in the Broken River, southern Murray-Darling Basin, Australia. I documented patterns in abundance, length, age and the amount of yolk of drifting free embryos and estimated spawning periods for adult Murray cod in two reaches throughout each breeding season between mid-October and mid-December from 1997 to 2001. Free embryos began drifting in late-October and continued until mid- to late-December. Abundances of drifting free embryos showed no obvious peak in most years and were unrelated to discharge. Length, amount of yolk and age typically varied with sampling date, but only age showed strong and negative correlations with temperature. Thus, it appears that temperature affected rates of development, and that developmental stage, not length or age, was likely to be the determinant for when free embryos left the paternal nest. Most free embryos were estimated to have spent between 5 and 7 days drifting. Spawning of Murray cod in the Broken River usually commenced in mid-October and continued until at least early December. Initiation of spawning was associated with temperatures of 15°C and above, but discharge was highly variable, and no other environmental variables were consistent across years. The mid-point of spawning – usually in the first week of November – is considered a more significant time, because it likely coincides with peak spawning, and conditions during and immediately after this time are expected to be optimal for the survival of eggs and free embryos.     

Ontogenetic Behavior and Dispersal of Sacramento River White Sturgeon, <Emphasis Type="BoldItalic">Acipenser Transmontanus</Emphasis>, with a Note on Body Color

Synopsis We studied Sacramento River white sturgeon, Acipenser transmontanus, in the laboratory to develop a conceptual model of ontogenetic behavior and provide insight into probable behavior of wild sturgeon. After hatching, free embryos initiated a low intensity, brief downstream dispersal during which fish swam near the bottom and were photonegative. The weak, short dispersal style and behavior of white sturgeon free embryos contrasts greatly with the intense, long dispersal style and behavior (photopositive and swimming far above the bottom) of dispersing free embryos of other sturgeon species. If spawned eggs are concentrated within a few kilometers downstream of a spawning site, the adaptive significance of the free embryo dispersal is likely to move fish away from the egg deposition site to avoid predation and reduce fish density prior to feeding. Larvae foraged on the open bottom, swam <1 m above the bottom, aggregated, but did not disperse. Early juveniles initiated a strong dispersal with fish strongly vigorously swimming downstream. Duration of the juvenile dispersal is unknown, but the strong swimming likely disperses fish many kilometers. Recruitment failure in white sturgeon populations may be a mis-match between the innate fish dispersal and post-dispersal rearing habitat, which is now highly altered by damming and reservoirs. Sacramento River white sturgeon has a two-step downstream dispersal by the free embryo and juvenile life intervals. Diel activity of all life intervals peaked at night, whether fish were dispersing or foraging. Nocturnal behavior is likely a response to predation, which occurs during both activities. An intense black-tail body color was present on foraging larvae, but was weak or absent on the two life intervals that disperse. Black-tail color may be an adaptation for avoiding predation, signaling among aggregated larvae, or both, but not for dispersal.     

Ecological restoration and revegetation works in Korea

Korea established foundations for rapid economic growth and national development within a short period of time, but not without incidental problems of degradation to the natural environment. Problems include destruction of ecosystems and reduction of forest area. Nowadays, environment-friendly construction projects are required in Korea for efficient use and preservation of national land. In an effort to protect natural land four types of restoration and preservation plans have been proposed recently. This paper explores the status and value of these efforts and the problems of re-vegetation works on disturbed land in Korea. Korea still gives insufficient attention to species selection for re-vegetation in terms of ecological soundness. In restoring damaged areas, Korea still uses mainly exotic species. As a result, the Ministry of Construction and Transportation is revising design criteria for road slopes in consideration of climate and topography. The Ministry of Environment revised the Natural Environment Conservation Law and uses natural ecological restoration engineers and natural environment management operators as environment restoration specialists. These engineers and sectors specialize in the area of nature in reviews and ecological restoration works. The first national qualifying examination to select natural ecological restoration engineers and natural environment management operators took place in 2004. In an effort to seek systematic conservation for an eco-network, there have been attempts to designate the Baekdu Daegan, which runs south to north along the Korean Peninsula, and the Demilitarised Zone, which traverses east to west, as ecological axes. Efforts to survey the damaged habitats found in the Baekdu Daegan and to develop a restoration plan after designating restoration areas are being made. Moreover, in 2004, the National Assembly passed an Act on the Protection of the Baekdu Daegan Mountain System which will facilitate the designation of Baekdu Daegan into core and buffer areas and therefore its designation as a protected area. The Seoul Metropolitan Government is planning to increase green space in urban areas. In the case of the Cheonggyecheon stream restoration project, which was initiated as part of efforts to restore urban ecosystems, the removal of existing structures is nearing completion. Once it is finished, a highly diverse urban green corridor biosphere reserve will be created along with rooftop re-vegetation. The Seoul Metropolitan government plans to introduce programs to support rooftop re-vegetation projects. Various options are still under consideration or at a pilot stage, but once these efforts become more visible, they are likely to play a positive role in developing and preserving national land in Korea.     

Prevalence, quantification and typing of adenoviruses detected in river and treated drinking water in South Africa

AIMS: Human adenoviruses (HAds), of which there are 51 serotypes, are associated with gastrointestinal, respiratory, urinary tract and eye infections. The importance of water in the transmission of HAds and the potential health risks constituted by HAds in these environments are widely recognized. Adenoviruses have not previously been quantified in river and treated drinking water samples. In this study, HAds in river water and treated drinking water sources in South Africa were detected, quantified and typed. METHODS AND RESULTS: Adenoviruses were recovered from the water samples using a glass wool adsorption-elution method followed by polyethylene glycol/NaCl precipitation for secondary concentration. The sensitivity and specificity of two nested PCR methods were compared for detection of HAds in the water samples. Over a 1-year period (June 2002 to July 2003), HAds were detected in 5.32% (10/188) of the treated drinking water and 22.22% (10/45) of river water samples using the conventional nested PCR method. The HAds detected in the water samples were quantified using a real-time PCR method. The original treated drinking water and river water samples had an estimate of less than one copy per litre of HAd DNA present. The hexon-PCR products used for typing HAds were directly sequenced or cloned into plasmids before sequencing. In treated drinking water samples, species D HAds predominated. In addition, adenovirus serotypes 2, 40 and 41 were each detected in three different treated drinking water samples. Most (70%) of the HAds detected in river water samples analysed were enteric HAds (serotypes 40 and 41). One HAd serotype 2 and two species D HAds were detected in the river water. CONCLUSIONS: Adenoviruses detected in river and treated drinking water samples were successfully quantified and typed. The detection of HAds in drinking water supplies treated and disinfected by internationally recommended methods, and which conform to quality limits for indicator bacteria, warrants an investigation of the risk of infection constituted by these viruses. The risk of infection may have implications for the management of drinking water quality. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is unique as it is the first report on the quantification and typing of HAds in treated drinking water and river water. This baseline data is necessary for the meaningful assessment of the potential risk of infection constituted by these viruses.     

Export of Nitrogen,Phosphorus, and Suspended Solids from a Southern New England Watershed to Little Narragansett Bay

The Pawcatuck River watershed (764 km²) is a mainly forested drainage basin with a low population density (80 people km⁻²) that discharges to a shallow estuary, Little Narragansett Bay (RI and CT, USA). In order to quantify the nitrogen (N) and phosphorus (P) flux to the estuary, we measured all forms of nitrogen and phosphorus, as well as suspended solids at the mouth of the river above tidal influence, on more than 80 occasions over an annual cycle. The annual export of total nitrogen, total phosphorus, and total suspended solids amounted to 16.0×10⁶ mol y⁻¹, 0.97×10⁶ mol y⁻¹, and 1.4×10⁶ kg y⁻¹, respectively. Nitrogen export was equally divided between dissolved inorganic (83% NO₃⁻) and organic forms, with particulate nitrogen comprising 17% of the total flux. Phosphorus export was dominated by particulate forms (67%), with dissolved inorganic phosphate contributing 30% and dissolved organic phosphorus contributing 8% of the annual flux. Preliminary nutrient budgets for the Pawcatuck watershed suggest that only about 10% of the nitrogen and phosphorus inputs are exported from the system. Strong regressions between water discharge and TN enabled us to extrapolate the data collected during the relatively dry study period to a long term average discharge year. Under normal river discharge conditions, the N flux would be approximately 26.0×10⁶ mol y⁻¹ or about 20% of the nitrogen inputs to the watershed. This value is very close to the N flux predicted by a regression developed by others from a wide range of larger watersheds. The relatively large size of the Pawcatuck watershed relative to the estuary (9.6 km²), makes Little Narragansett Bay one of the most intensively nitrogen loaded estuaries on the Atlantic coast in spite of the dominant forest cover of the watershed.     

Dynamics of seston constituants in the Ariège and Garonne rivers (France)

Water contents of suspended matter, algal pigments, particulate organic carbon and particulate phosphorus were measured in the rivers Garonne (2 sites) and Ariège (1 site) throughout an annual cycle. The general trend of the parameters was similar at the three sites. Depending on the sites, the period of algal growth (chlorophyll a + phaeopigments > 25 µg l^–1), lasted from two to six weeks in August–September. The algal peaks reached 50 to 90 µg 1^–1 of total pigments. High contents of particulate organic carbon (> 2 mg 1^–1) occurred at the end of summer (coinciding with algal growth), and during the November and May floods. In summer 50–75 % of the suspended matter was organic, in spring this was 10 times less. The high linear correlation between particulate organic carbon and pigment contents (r = 0.87; P = 0.0001) suggested an algal origin of at least part of the particulate carbon. Algal carbon was minor in the annual fluxes of particulate carbon (25 to 39% depending on the sites), but relatively high in comparison with other rivers. The mean particulate phosphorus content calculated over the year was 24 µg l^–1 ; it varied from 15 µg l^–1 during the high water period to 28 µg 1^–1 during the low water period. Likewise the percentage of particulate phosphorus in the suspended matter varied from 0.17 to 0.40. A negative linear correlation existed between particulate phosphorus content and specific discharge (r = – 0.46; P = 0.0001).The very marked seasonal trend of the parameters and the interactions led us to differentiate two modes of the rivers' functioning: a hydrologic phase and a biological phase. The hydrologic phase (high water) was dominated by the processes of erosion and transfer over the whole catchment area and the flood plain, while the biological phase was characterized by a high primary production in the river bed.     

Variation in nutrient limitation of lotic and lentic algal communities in a Texas (USA) river

Nutrient limitation of periphyton and phytoplankton was assessed in the Upper Guadalupe River, Texas USA. Nutrient-diffusing substrates with added nitrogen (N) and phosphorus (P) were used to identify the limiting nutrient for lotic algae at three river sites in summer, fall, and winter. Pots enriched with P had significantly higher chlorophyll a concentrations for 7 of 9 trials. Added N alone did not significantly increase algal standing crops, although it was found to be secondarily limiting on one (and possibly two) occasions. Flow-through enrichment experiments were conducted in order to quantify the concentration of P needed to significantly increase algal standing crops. Response to enrichment was rapid when ambient P concentration was low (< 0.010 mg L^–1), but more moderate when ambient P levels were higher (0.015–0.025 mg L^–1). Nutrient limitation of phytoplankton in small surface-release reservoirs varied throughout the study, but N was either primarily or secondarily limiting in 6 of 8 trials; shifts in the limiting nutrient were correlated with fluctuations in flow into the reservoirs. Our enrichment studies show that algal response to nutrient addition was unpredictable as phytoplankton tended to be N-limited while periphyton was mainly P-limited. Further, while discharge apparently dictated the nutrient-biomass relationship for phytoplankton in reservoirs, ambient nutrient level is an important determinant of lotic periphyton response to enrichment.     

Transport of mercury by the Katun river,West Siberia

Some results of a 2-year study of mercury pollution of the Katun river (Siberia) are summarised. Measurements of water flow, sediment transport and mercury concentrations were made and used to calculate the amount of mercury transported by the river. The distribution of transport between water phase and suspended material is calculated. It is concluded that suspended sediments play the main role in this process. The significance of different fractions of suspended sediment is also discussed.     

15N natural abundance in plants of the Amazon River floodplain and potential atmospheric N2 fixation

Summary The¹⁵N natural abundance values of various Amazon floodplain (várzea) plants was investigated. Samples of young leaf tissues were collected during three different periods of the river hydrography (low water, mid rising water and high water) and during one period in the Madeira River (high water). A large variation of¹⁵N abundance was observed, both among the different plant types and between the different flood stages. This variation probably, reflected, in part, the highly variable nature of the floodplain, sometimes dry and oxygenated and at other times inundated and anaerobic and, in part, changes in plant nitrogen metabolism. Comparison of the nitrogen isotopic composition of leguminous plants with that of non-leguminous plants showed that, on average, the¹⁵N abundance was lower in the legumes than non-legumes, suggesting active N-fixation. Also, the¹⁵N natural abundance in aquatic grasses of the generaPaspalum, was in general, lower than the¹⁵N abundance of aquatic grasses of the generaEchinochloa. As both of these grasses grow in the same general habitat, it appears thatPaspalum grasses may also be nitrogen fixers.