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Runoff and effluent discharge from mining activities has resulted in elevated concentrations of selenium in aquatic ecosystems. Bioavailability is dependent on chemical speciation. Although dissolved inorganic Se species are not directly toxic to organisms, uptake by primary producers and subsequent biotransformation to organo-selenium species substantially increase risk and bioaccumulation potential, potentially impairing reproduction in high-order organisms. The effects of dietary selenium exposure were assessed in two aquatic invertebrates: Ceriodaphnia dubia and Chironomus dilutus. Two generations of these organisms were exposed to seleniferous algae grown in 0-40 μg L-1 selenate. Dissolved selenate was readily absorbed and concentrated by algal species Pseudokirchneriella subcapitata and Chlorella kesslerii. Se had no effect on survival at treated concentrations. Dietary selenium exposures had little effect on reproductive endpoints in either invertebrate species, suggesting that invertebrates have the ability to regulate chronic Se exposures from dietary sources. These results provide valuable information concerning the effects of dietary selenium in aquatic invertebrates.

Despite the importance of tropical rivers to the global carbon cycle, the nature of carbon cycling within these watersheds has been dealt with by only a handful of studies. The current work attempts to address this lack of information, using stable isotope and concentration measurements to constrain sources and sinks of carbon in two Peninsular Malaysian watersheds. The basins are located on the central-western and northeastern coasts of the Malaysian Peninsula, and are drained by the Langat and Kelantan Rivers, respectively. Water samples were collected from three points along the two rivers twice a month, in addition to the sampling of groundwater in adjacent aquifers. Principal component analyses (PCA) on water chemistry parameters in the Langat and Kelantan Rivers show the dominance of geogenic and anthropogenic influences, grouped in 4 to 6 components that comprise over 50 % of the total dataset variances. The geogenic input is reflected by components showing strong loadings by Ca, Mg, Mn, Si, and Sr, while anthropogenic influences via pollution are indicated via strong loadings by NO3, SO4, K, Zn and Cl. The carbon isotope and concentration data appear unrelated to these groups, suggesting that the riverine carbon cycle in both locations is dominated by other factors. These may include alternative sources of organic pollution, or inputs from the local vegetation and soils. The mean riverine 13CDOC of -27.8 ± 2.9 ‰ and -26.6 ± 2.2 ‰ in the Langat and Kelantan Basins, respectively, are consistent with the dominance of C3-type vegetation in both watersheds. Riverine 13CDIC signatures approach C3-like values at high DIC concentrations, with measurements as low as -19 ‰ in the Kelantan Basin and -20 ‰ observed in the Langat Basin, consistent with a biological origin for riverine DIC. However, the average 13CDIC in river water is 13C-enriched by about 10 ‰ relative to the expected C3 source in both rivers, and this 13C- enrichment appears to be largest with smaller DIC concentrations. Because of the overpressures of CO2 in the rivers, entrainment of isotopically-heavy atmospheric CO2 is not a likely explanation for the observed 13C-enrichment. Theoretically, dissolution of carbonates could be an alternative source of 13C-enriched carbon, but this lithology is scarce, particularly in the Langat watershed. The increase in DIC downstream and generally high pCO2 values in most river sections argues against aquatic photosynthesis as a primary causative factor for the observed isotopic enrichment. This elimination process leaves the speciation of riverine DIC and the evasion of CO2 as the most likely mechanisms for 13C-enrichment in DIC, via isotope fractionation during HCO3- hydration and CO2 diffusion. Potentially, methanogenic activity could also be, at least partially, responsible for the 13C-enrichment in DIC, particularly immediately downstream of the Langat Reservoir, but due to the absence of empirical data, this must remain only a theoretical proposition. The aquatic chemistry and dissolved carbon data suggests that pollution discharge into the Langat and Kelantan Rivers is the major factor that is responsible for the considerable CO2 overpressures and high DIC and DOC concentrations in the river waters, particularly in the downstream sections. This pollution is likely of biological origin, via sewage and palm oil mill effluent (POME) discharge, and therefore isotopically indistinguishable from natural C3 plant sources. Carbon budgets of the Langat and Kelantan River show CO2 degassing to be a significant mechanism of fluvial carbon loss, comprising roughly 50 %, or more, of the total riverine carbon export in both watersheds. The remainder of the river carbon is transported to the ocean in the form of DIC, DOC and POC in broadly comparable proportions. However, the combined riverine carbon export from the Kelantan and Langat Basins amount to 2 % or less of the total carbon sequestration of the watersheds. Thus, most of the sequestered carbon is returned to the atmosphere via respiration, with smaller amounts incorporated into ecosystem biomass . These results highlight the complexity of carbon cycling in tropical rivers, and agree with previous studies in showing riverine systems to be more than simple conduits of carbon from the land to the ocean.

Larval Anisakis simplex, Pseudoterranova decipiens, Contracaecum osculatum and larvae and adults of Hysterothylacium aduncum were recovered from specimens of cod, haddock, blue whiting and bull rout; however, only A.simplex were retrieved from long rough dab. The epidemiology of infection by these four nematode species was examined both in whole fish, and in individual host tissues and organs. Frequency distributions of nematodes were found to be generally overdispersed in fish. Preliminary investigations revealed no strong evidence to suggest that competi tive interactions occurred between ascaridoid nematodes wi thin fish. Stomach lesions in gadoids were associated with single (partially penetrated) and mul tiple (throughout stomach wall) worm infections of larval A.simplex; such lesions were discrete and raised in appearance. Lesions associated with 1-3 larval P.decipiens in an open cavity within the stomach of angler fish were diffuse and not significantly raised. Histological examination of each form of ulcer revealed general similarities in pathology, with infil tration of inflamatory cells being the initial response to the nematode\s. Changes in the cephalic morphology of A.simplex, P.decip1ens, C.osculatum and H.aduncu were examined at different life cycle stages under scanning electron microscopy. Due to their small size, newly hatched third stage larvae of P .decip1ens were cultured in a bacterial mat prior to fixation for S.E.M., and the external ultrastructure of these larvae is described. The most prominent external feature at this stage is the cephalic boring tooth. Aspects of the internal ultrastructure of A. simplex, P.decipiens, C.osculatum and H.aduncu were examined using transmission electron microscopy. Newly hatched third stage larvae of P.decipiens show little differentiation of internal organs. The ultrastructure of sensory amphids in H.aduncum and A. simplex is cons i stent wi th that of a chemoreceptor, that of the single papilla in P.decipiens a mechanoreceptor. The ultrastructure of the digestive tract, excretory gland and body wall of marine ascaridoids were also examined.

The Scottish brown trout (Salmo trutta L.) is identified as an important resource which requires responsible and continual management. This study was divided into two parts; an electrophoretic survey of wild trout populations in Scotland, and a quantitative assessment of the genetic component to growth rate in various stocks, grown under hatchery and farm conditions. Sixty wild populations were sampled by various methods. All fish were typed using brain, eye, heart, liver and muscle tissue and starch gel electrophoresis for thirty four enzyme loci, thirteen of which were found to be polymorphic. Gene diversity analysis was conducted on the data collected, 33% of the diversity being attributed to differences between populations, much of the variation was thought to be due to founder effects. Evidence is presented to support a hypothesis that the trout in Scotland are derived from two main post glacial invasion stocks. Future management strategies for wild stocks of Scottish brown trout are discussed. Growth trials were conducted at Howietoun fish farm in order to calculate heritability estimates for growth rate. Hierarchical and factoral crossing schemes were employed, using broodstock from three stocks. Heritability estimates for growth rate were found to be high and it was concluded, significant genetic gains could be achieved if growth rate was the only trait of commercial interest and truncated mass selection was adopted. Attempts were made to investigate the relationship between heterozygosity and growth rate in the hatchery populations. It was concluded that more data were required to make a meaningful assessment, but from this study little evidence exists for a positive correlation between heterozygosity and growth rate. Correlations between early life cycle stages and subsequent growth are discussed.

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Through wastewater entering aquatic environments, aquatic insects are continuously exposed to pharmaceuticals including neurologically active antihistamines. The antihistamine hydroxyzine has previously been found to lower activity in damselflies and to reach 2000 times the concentration of surrounding water in damselfly tissue. The purpose of this short-term exposure study was to investigate if hydroxyzine also bioaccumulates in dragonflies and if dilute hydroxyzine (362 ± 50, mean ng/l ± SD) have effects on predator-prey interactions between dragonfly Aeshna grandis and damselfly Coenagrion hastulatum larvae, i.e. number of attacks and predation success. Predators and prey were captured and exposed during one, three or five days (with controls) before taking part in predation experiments; Dragonflies were put in separate containers with six damselflies, they were video recorded and attacks and predated damselflies noted during four hours. Tissue concentrations of hydroxyzine were analyzed from all dragonflies and a subsample of the damselflies showing a mean bioconcentration factor (BCF) of 27 and 7 respectively, surprisingly much lower than previous research. There was no difference in attack rate or predation efficiency between controls and exposed dragonflies. However, dragonflies exposed for five days were found to attack more and capture more prey than dragonflies exposed for one day, a change that was not seen in the controls. This confounding factor motivates further studies to clarify if hydroxyzine after a period of exposure can have a sublethal effect altering foraging and/or predator avoidance traits with the net result of increased predation success for dragonflies in the predator-prey interaction between dragonflies and damselflies.