Mapping intertidal habitats and an evaluation of their conservation status in Queensland, Australia

The goal of biodiversity conservation has been described as the conservation of diversity at three levels: ecosystem, species and genetic diversity. Developing a representative system of marine protected areas (MPAs) is considered an effective way to achieve this goal in the marine environment. In the absence of detailed information relating to biological distributions there has been increasing use of biodiversity surrogates to determine MPA priorities at regional levels. The development of biodiversity surrogates at fine scales (i.e. habitats) will have an increasingly important role in the identification of sites that will contribute to a representative system of MPAs. This is because it will increase the likelihood that the system will adequately achieve biodiversity objectives by ensuring protection of a greater range of habitats and species. This article provides an explanation of an intertidal shoreline habitat surrogate used to describe 24,216km of Queensland's coastline. The protective status of intertidal habitats was evaluated to assist with designing a representative system of intertidal MPAs. (C) 2002 Elsevier Science Ltd. All rights reserved.

Winter intervention against Aedes aegypti (Diptera : Culicidae) larvae in subterranean habitats slows surface recolonization in summer

At semiarid Charters Towers, north Queensland, Australia, the importance of Aedes aegypti (L.) in wells was assessed in relation to the colonization of surface habitats during the wet season. From April to July 1999, 10 wells (five positive for Ae. aegypti) were monitored to assess their status and larvae population numbers therein. All surface containers located within a 100 m radius of each well were removed, treated with s-methoprene or sealed to prevent the utilization of these containers by mosquitoes. These inner cores were surrounded by outer zones for a further 100 m in which surface containers were left untreated but all subterranean habitats were treated. Ovitraps were monitored monthly in the inner cores for 36 wk from August 1999 to April 2000 and differences in the proportions of ovitraps positive for Ae. aegypti and Ochlerotatus notoscriptus (Skuse) were analyzed by logistic regression. Analysis of the proportions of ovitraps positive for Ae. aegypti near positive wells indicated significantly greater colonization from November to March (the wet season), compared with those situated near Ae. aegypti negative wells. As Oc. notoscriptus were not produced from subterranean sites, comparisons of the proportions of ovitraps positive for Oc. notoscriptus in positive and negative inner cores provided an indication of the relative productivity of the uncontrolled surface containers in the outer zones. Differences in the utililization of ovitraps by Oc. notoscriptus among positive and negative cores were observed during only one month (March), when oviposition was greater in ovitraps in the negative cores, compared with the positive cores. Best subsets linear regression analysis of the proportion of ovitraps positive for Ae. aegypti against meteorological variables (rainfall, mean wind speed, mean relative humidity, mean minimum, and maximum temperature) during the week of ovitrapping indicated that minimum temperature and wind speed accounted for 63.4% of the variability. This study confirms that for semiarid towns such as Charters Towers, the practice of treating a relatively small number of key subterranean habitats during winter will significantly affect Ae. aegypti recolonization of surface container habitats during summer, the period of greatest risk for dengue.

Adaptation of rainbow fish to lake and stream habitats

Fish occupy a range of hydrological habitats that exert different demands on locomotor performance. We examined replicate natural populations of the rainbow fishes Melanotaenia eachamensis and M. duboulayi to determine if colonization of low-velocity (lake) habitats by fish from high-velocity (stream) habitats resulted in adaptation of locomotor morphology and performance. Relative to stream conspecifics, lake fish had more posteriorly positioned first dorsal and pelvic fins, and shorter second dorsal fin bases. Habitat dimorphism observed between wild-caught fish was determined to be heritable as it was retained in M. eachamensis offspring raised in a common garden. Repeated evolution of the same heritable phenotype in independently derived populations indicated body shape divergence was a consequence of natural selection. Morphological divergence between hydrological habitats did not support a priori expectations of deeper bodies and caudal peduncles in lake fish. However, observed divergence in fin positioning was consistent with a family-wide association between habitat and morphology, and with empirical studies on other fish species. As predicted, decreased demand for sustained swimming in takes resulted in a reduction in caudal red muscle area of lake fish relative to their stream counterparts. Melanotaenia duboulayi lake fish also had slower sustained swimming speeds (U-crit) than stream conspecifics. In M. eachamensis, habitat affected U-crit of males and females differently. Specifically, females exhibited the pattern observed in M. duboulayi (lake fish had faster U-crit than stream fish), but the opposite association was observed in males (stream males had slower Ucrit than lake males). Stream M. eachamensis also exhibited a reversed pattern of sexual dimorphism in U-crit (males slower than females) relative to all other groups (males faster than females). We suggest that M. eachamensis males from streams responded to factors other than water velocity. Although replication of muscle and U,,it phenotypes across same habitat populations within and/or among species was suggestive of adaptation, the common garden experiment did not confirm a genetic basis to these associations. Kinematic studies should consider the effect of the position and base length of dorsal fins.

Changes in morphology and physiology of an East Mediterranean sponge in different habitats

The sponge Tetilla sp. (Tetractinomorpha: Tetillidae) is a common species in the eastern Mediterranean. This sponge inhabits four different habitat types differing in wave impact and irradiance levels. Two of these habitats (a shallow cave and deep water) are characterized by relatively calm water, whereas the other two (shallow exposed site and tide pools) are in turbulent water with high energy flow. The present study examined the influence of physical (depth, illumination and water motion) and biotic factors on morphology, skeletal plasticity and reproductive traits among the four spatially separated populations. Sponges from tidal pools had significantly larger body volume than sponges from deep water and from shallow caves (ANOVA: tidal-deep P< 0.0001; tidal-shallow caves P< 0.05). Sponges from exposed habitats were significantly larger than deep-water sponges (ANOVA: P=0.01). In addition, individuals from tide pools and from the exposed habitat had a significantly higher proportion of structural silica than sponges from the calmer deep water and from the cave sites. Oxea spicules in sponges from the calm habitats were significantly shorter than in those from the tidal pools and the exposed habitats. The percentage of spicules out of a sponge's dry weight in individuals transplanted from deep (calm) to shallow (turbulent) water significantly increased by 21.9&PLUSMN; 12.9%. The new spicule percentage did not differ significantly from that of sponges originally from shallow water. Oocyte diameter differed significantly between habitats. The maximal size of mature eggs was found in deep-water sponges in June (97&PLUSMN; 5 μ m). In the shallow habitats, a smaller maximal oocyte diameter was found in the cave, in May (56.5&PLUSMN; 3 μ m). Furthermore, oocyte density in shallow-water sponges was highest in May and decreased in June (with 88.2&PLUSMN; 9 and 19.3&PLUSMN; 9 oocytes mm(-2), respectively). At the same time (June), oocyte density of deep-water sponges had just reached its maximum (155&PLUSMN; 33.7 oocytes mm(-2)). The difference in oocyte size and density between deep- and shallow-water individuals indicates an earlier gamete release in the shallow sponge population. The results suggest that plasticity in skeletal design of this sponge indicates a trade off between spicule production and investment in reproduction.

Herbicides implicated as the cause of severe mangrove dieback in the Mackay region, NE Australia: consequences for marine plant habitats of the GBR World Heritage Area

Herbicides, particularly diuron, were correlated with severe and widespread dieback of the dominant mangrove, Avicennia marina (Forsk.) Vieth. var. eucalyptifolia (Val.) N.C. Duke (Avicenniaceae), its reduced canopy condition, and declines in seedling health within three neighbouring estuaries in the Mackay region of NE Australia. This unusual species-specific dieback, first observed in the early 1990s, had gotten notably worse by 2002 to affect > 30km(2) of mangroves in at least five adjacent estuaries in the region. Over the past century, agricultural production has responded well to the demands of increasing population with improvements in farm efficiency assisted by significant increases in the use of agricultural chemicals. However, with regular and episodic river flow events, these chemicals have sometimes found their way into estuarine and nearshore water and sediments where their effects on marine habitats have been largely unquantified. Investigations over the last three years in the Mackay region provide compelling evidence of diuron, and possibly other agricultural herbicides, as the most likely cause of the severe and widespread mangrove dieback. The likely consequences of such dieback included declines in coastal water quality with increased turbidity, nutrients and sediment deposition, as well as further dispersal of the toxic chemicals. The implications of such findings are immense since they describe not only the serious deterioration of protected and beneficial mangrove habitat but also the potential for significant direct and indirect effects on other highly-valued estuarine and marine habitats in the region, including seagrass beds and coral reefs of the Great Barrier Reef lagoon. This article reviews all key findings and observations to date and describes the essential correlative and causative evidence. (c) 2004 Elsevier Ltd. All rights reserved.

Mapping mosquito breeding habitats (water) under mangrove canopy: contribution from airborne thermal scanning

Proceedings of the 11th Australasian Remote Sensing and Photogrammetry Conference

Osmoregulation of the Australian freshwater crocodile, Crocodylus johnstoni, in fresh and saline waters

An unusual saltwater population of the "freshwater" crocodilian, Crocodylus johnstoni, was studied in the estuary of the Limmen Bight River in Australia's Northern Territory and compared with populations in permanently freshwater habitats. Crocodiles in the river were found across a large salinity gradient, from fresh water to a salinity of 24 mg.ml-1, more than twice the body fluid concentration. Plasma osmolarity, concentrations of plasma Na+, Cl-, and K+, and exchangeable Na+ pools were all remarkably constant across the salinity spectrum and were not substantially higher or more variable than those in crocodiles from permanently freshwater habitats. Body fluid volumes did not vary; condition factor and hydration status of crocodiles were not correlated with salinity and were not different from those of crocodiles from permanently fresh water. C. johnstoni clearly has considerable powers of osmoregulation in waters of low to medium salinity. Whether this osmoregulatory competence, extends to continuously hyperosmotic environments is not known, but distributional data suggest that C. johnstoni in hyperosmotic conditions may require periodic access to hypoosmotic water. The study demonstrates a physiological capacity for colonisation of at least some estuarine waters by this normally stenohaline freshwater crocodilian.

Weathering of hydrocarbons in mangrove sediments: testing the effects of using dispersants to treat oil spills

This field study was a combined chemical and biological investigation of the relative effects of using dispersants to treat oil spills impacting mangrove habitats. The aim of the chemistry was to determine whether dispersant affected the short- or long-term composition of a medium range crude oil (Gippsland) stranded in a tropical mangrove environment in Queensland, Australia. Sediment cores from three replicate plots of each treatment (oil only and oil plus dispersant) were analyzed for total hydrocarbons and for individual molecular markers (alkanes, aromatics, triterpanes, and steranes). Sediments were collected at 2 days, then 1, 7, 13 and 22 months post-spill. Over this time, oil in the six treated plots decreased exponentially from 36.6 +/- 16.5 to 1.2 +/- 0.8 mg/g dry wt. There was no statistical difference in initial oil concentrations, penetration of oil to depth, or in the rates of oil dissipation between oiled or dispersed oil plots. At 13 months, alkanes were >50% degraded, aromatics were similar to 30% degraded based upon ratios of labile to resistant markers. However, there was no change in the triterpane or sterane biomarker signatures of the retained oil. This is of general forensic interest for pollution events. The predominant removal processes were evaporation (less than or equal to 27%) and dissolution (greater than or equal to 56%), with a lag-phase of 1 month before the start of significant microbial degradation (less than or equal to 7%). The most resistant fraction of the oil that remained after 7 months (the higher molecular weight hydrocarbons) correlated with the initial total organic carbon content of the soil. Removal rate in the Queensland mangroves was significantly faster than that observed in the Caribbean and was related to tidal flushing. (C) 1999 Elsevier Science Ltd. All rights reserved.

Life tables of the processionary caterpillar Ochrogaster lunifer Herrich-Schaffer (Lepidoptera : Thaumetopoeidae) at local and regional scales

A major ongoing debate in population ecology has surrounded the causative factors underlying the abundance of phytophagous insects and whether or not these factors limit or regulate herbivore populations. However, it is often difficult to identify mortality agents in census data, and their distribution and relative importance across large spatial scales are rarely understood. Were, we present life tables for egg batches and larval cohorts of the processionary caterpillar Ochrogaster lunifer Herrich-Schaffer, using intensive local sampling combined with extensive regional monitoring to ascertain the relative importance of different mortality factors at different localities. Extinction of entire cohorts (representing the entire reproductive output of one female) at natural localities was high, with 82% of the initial 492 cohorts going extinct. Mortality was highest in the egg and early instar stages due to predation from dermestid beetles, and while different mortality factors (e.g. hatching failure, egg parasitism and failure to establish on the host) were present at many localities, dermestid predation, either directly observed or inferred from indirect evidence, was the dominant mortality factor at 89% of localities surveyed. Predation was significantly higher in plantations than in natural habitats. The second most important mortality factor was resource depletion, with 14 cohorts defoliating their hosts. Egg and larval parasitism were not major mortality agents. A combination of predation and resource depletion consistently accounted for the majority of mortality across localities, suggesting that both factors are important in limiting population abundance. This evidence shows that O. lunifer is not regulated by natural enemies alone, but that resource patches (Acacia trees) ultimately, and frequently, act together to limit population growth.