Submarine groundwater discharge and associated chemical input to a coastal sea

This paper presents a theoretical model of flow and chemical transport processes in subterranean estuaries (unconfined brackish groundwater aquifers at the ocean-land interface). The model shows that groundwater circulation and oscillating flow, caused by wave setup and tide, may constitute up to 96% of submarine groundwater discharge (SGWD) compared with 4% due to the net groundwater discharge. While these local flow processes do not change the total amount of land-derived chemical input to the ocean over a long period (e.g., yearly), they induce fluctuations of the chemical transfer rate as the aquifer undergoes saltwater intrusion. This may result in a substantial increase in chemical fluxes to the ocean over a short period (e.g., monthly and by a factor of 20 above the averaged level), imposing a possible threat to the marine environment. These results are essentially consistent with the experimental findings of Moore [1996] and have important implications for coastal resources management.

Implication of the visual system in the regulation of activity cycles in the absence of solar light: 2-[I-125]iodomelatonin binding sites and melatonin receptor gene expression in the brains of demersal deep-sea gadiform fish

Relative eye size, gross brain morphology and central localization of 2-[I-125]iodomelatonin binding sites and melatonin receptor gene expression were compared in six gadiform fish living at different depths in the north-east Atlantic Ocean: Phycis blennoides (capture depth range 265-1260 m), Nezumia aequalis (445-1512 m), Coryphaenoides rupestris (706-1932 m), Trachyrincus murrayi (1010-1884 m), Coryphaenoides guentheri (1030 m) and Coryphaenoides (Nematonurus) armatus (2172-4787 m). Amongst these, the eye size range was 0.15-0.35 of head length with a value of 0.19 for C.(N.) armatus, the deepest species. Brain morphology reflected behavioural differences with well-developed olfactory regions in P.blennoides, T.murrayi and C. (N.) armatus and evidence of olfactory deficit in N. aequalis, C. rupestris and C. guentheri. All species had a clearly defined optic tectum with 2-[I-125] iodomelatonin binding and melatonin receptor gene expression localized to specific brain regions in a similar pattern to that found in shallow-water fish. Melatonin receptors were found throughout the visual structures of the brains of all species. Despite living beyond the depth of penetration of solar light these fish have retained central features associated with the coupling of cycles of growth, behaviour and reproduction to the diel light-dark cycle. How this functions in the deep sea remains enigmatic.

Long range forecasts of the numbers of Helicoverpa punctigera and H-armigera (Lepidoptera : Noctuidae) in Australia using the Southern Oscillation Index and the Sea Surface Temperature

The use of long-term forecasts of pest pressure is central to better pest management. We relate the Southern Oscillation Index (SOI) and the Sea Surface Temperature (SST) to long-term light-trap catches of the two key moth pests of Australian agriculture, Helicoverpa punctigera (Wallengren) and H. armigera (Hubner), at Narrabri, New South Wales over 11 years, and for H. punctigera only at Turretfield, South Australia over 22 years. At Narrabri, the size of the first spring generation of both species was significantly correlated with the SOI in certain months, sometimes up to 15 months before the date of trapping. Differences in the SOI and SST between significant months were used to build composite variables in multiple regressions which gave fitted values of the trap catches to less than 25% of the observed values. The regressions suggested that useful forecasts of both species could be made 6-15 months ahead. The influence of the two weather variables on trap catches of H. punctigera at Turretfield were not as strong as at Narrabri, probably because the SOI was not as strongly related to rainfall in southern Australia as it is in eastern Australia. The best fits were again given by multiple regressions with SOI plus SST variables, to within 40% of the observed values. The reliability of both variables as predictors of moth numbers may be limited by the lack of stability in the SOI-rainfall correlation over the historical record. As no other data set is available to test the regressions, they can only be tested by future use. The use of long-term forecasts in pest management is discussed, and preliminary analyses of other long sets of insect numbers suggest that the Southern Oscillation Index may be a useful predictor of insect numbers in other parts of the world.

A new blood-fluke, Cardicola Forsteri, (Digenea : Sanguinicolidae) of southern blue-fin tuna (Thunnus Maccoyii) in aquaculture

Cardicola forsteri sp. nov. (Digenea: Sanguinicolidae) is described from the heart of captive southern blue-fin tuna, Thunnus maccoyii (Scombridae), from South Australia. The new species is distinguished from other species of Cardicola by its very extensive testis, the length of its oesophagus, the length of its gut caeca and the form of its ovary. Cardicola smithi appears to be associated with heart and gill lesions(1).

Spatial and temporal variation in distribution of mangroves in Moreton Bay, subtropical Australia: a comparison of pattern metrics and change detection analyses based on aerial photographs

An assessment of the changes in the distribution and extent of mangroves within Moreton Bay, southeast Queensland, Australia, was carried out. Two assessment methods were evaluated: spatial and temporal pattern metrics analysis, and change detection analysis. Currently, about 15,000 ha of mangroves are present in Moreton Bay. These mangroves are important ecosystems, but are subject to disturbance from a number of sources. Over the past 25 years, there has been a loss of more than 3800 ha, as a result of natural losses and mangrove clearing (e.g. for urban and industrial development, agriculture and aquaculture). However, areas of new mangroves have become established over the same time period, offsetting these losses to create a net loss of about 200 ha. These new mangroves have mainly appeared in the southern bay region and the bay islands, particularly on the landward edge of existing mangroves. In addition, spatial patterns and species composition of mangrove patches have changed. The pattern metrics analysis provided an overview of mangrove distribution and change in the form of single metric values, while the change detection analysis gave a more detailed and spatially explicit description of change. An analysis of the effects of spatial scales on the pattern metrics indicated that they were relatively insensitive to scale at spatial resolutions less than 50 m, but that most metrics became sensitive at coarser resolutions, a finding which has implications for mapping of mangroves based on remotely sensed data. (C) 2003 Elsevier Science B.V. All rights reserved.

Neogene and Quaternary rollback evolution of the Tyrrhenian Sea, the Apennines, and the Sicilian Maghrebides

Reconstruction of the evolution of the Tyrrhenian Sea shows that the major stage of rifting associated with the opening of this basin began at similar to10 Ma. It involved two episodes of back arc extension, which were induced by the rollback of a west dipping subducting slab. The first period of extension (10-6 Ma) was prominent in the northern Tyrrhenian Sea and in the western part of the southern Tyrrhenian Sea. The second period of extension, mainly affected the southern Tyrrhenian Sea, began in the latest Messinian (6-5 Ma) and has been accompanied by subduction rollback at rates of 60-100 km Myr(-1). Slab reconstruction, combined with paleomagnetic and paleogeographic constraints, indicates that in the central Apennines, the latest Messinian (6-5 Ma) arrival of a carbonate platform at the subduction zone impeded subduction and initiated a slab tear and major strike-slip faults. These processes resulted in the formation of a narrow subducting slab beneath the Ionian Sea that has undergone faster subduction rollback and induced extreme rates of back arc extension.

Male-by-female interactions influence fertilization success and mediate the benefits of polyandry in the sea urchin Heliocidaris erythrogramma

Numerous studies have reported that females benefit from mating with multiple males (polyandry) by minimizing the probability of fertilization by genetically incompatible sperm. Few, however, have directly attributed variation in female reproductive success to the fertilizing capacity of sperm. In this study we report on two experiments that investigated the benefits of polyandry and the interacting effects of males and females at fertilization in the free-spawning Australian sea urchin Heliocidaris erythrogramma. In the first experiment we used a paired (split clutch) experimental design and compared fertilization rates within female egg clutches under polyandry (eggs exposed to the sperm from two males simultaneously) and monandry (eggs from the same female exposed to sperm from each of the same two males separately). Our analysis revealed a significant fertilization benefit of polyandry and strong interacting effects of males and females at fertilization. Further analysis of these data strongly suggested that the higher rates of fertilization in the polyandry treatment were due to an overrepresentation of fertilizations due to the most compatible male. To further explore the interacting effects of males and females at fertilization we performed a second factorial experiment in which four mates were crossed with two females (in all eight combinations). In addition to confirming that fertilization success is influenced by male X female interactions, this latter experiment revealed that both sexes contributed significant variance to the observed patterns of fertilization. Taken together, these findings highlight the importance of male X female interactions at fertilization and suggest that polyandry will enable females to reduce the cost of fertilization by incompatible gametes.

Occurrence of cutaneous infections of Myxobolus episquamalis (Myxozoa: Myxobolidae) in sea mullet, Mugil cephalus L, in Australia

Objective To report the occurrence of Myxobolus episquamalis in sea mullet, Mugil cephalus L, caught in estuaries in eastern and western Australia. Design A prospective study of commercial catches of mullet in the Clarence River of NSW and individual cases from other areas. Results The organism caused pale, white to pink, raised lesions on the scales and fins of sea mullet. Occurrence of infection was highest in spring and in a marine (down-river) environment compared to a brackish environment. Up to 6% of fish were affected in commercial catches. Conclusion The infection is widespread in Australian mullet, but rarely causes significant economic loss.

Tubular eyes of deep-sea fishes: A comparative study of retinal topography

The world's deep oceans are home to a number of teleosts with asymmetrical or tubular eyes. These immobile eyes possess large spherical lenses and subtend a large binocular visual field directed either dorsally or rostrally. Derived from a lateral non-tubular eye, the tubular eye is comprised of a thick main retina, subserving the rostrally or dorsally directed binocular visual field, and a thin accessory retina subserving, the lateral, monocular visual field. The main retina is thought to receive a focussed image, while the accessory retina is too close to the lens for a focussed image to be received. Several species also possess retinal diverticula, which are small evaginations of differentiated retina located in the rostrolateral wall of the eye and thought to increase the visual field. In order to investigate the spatial resolving power of these retinae (main, accessory and diverticulum), the distribution of cells within the ganglion cell layer was analysed from retinal wholemounts and sectioned material in ten species representing four genera. In all species, the main retina possesses a marked increase in cell density towards a specialised retinal region (area centralis), with a centro-peripheral gradient range between 7.1 and 60:1 and a peak density range of between 30 and 55 x 10(3) cells per mm(2). The accessory retinae and the transitional zone between the main and accessory retinae possess relatively low cell densities (between 1 and 10 x 10(3) cells per mm(2)) and lack an area centralis. Retinal diverticula examined in four species possess mean ganglion cell densities of between 7.2 and 109.4 x 10(3) cells per mm(2). Analyses of soma areas show that the ganglion cell layer of most species possesses cells with areas in a range of 8.0 to 15.4 mu m(2) in the main retina and between 15.1 and 17.4 mu m(2) in the accessory retina. The peak spatial resolving power of the main retina of the ten species varies from 4.1 to 9.1 cycles per degree. The positions of the retinal areae centrales relative to each species' binocular visual field are discussed in relation to what is known of feeding behaviour of these fishes in the deep-sea.