Perturbation pathways affecting the avian lotic predator, blue duck, following a volcanic eruption

1. Perturbation pathways affecting interactions between feeding habitat, food supplies and diet of a lotic avian predator, blue duck (Hymenolaimus malacorhynchos Gemlin), were tracked in a New Zealand river following substantial inputs of sediment from a volcanic eruption. Sediment impacts were separated temporally into two distinct phases: (i) deposition of fine ash from volcanic fall‐out, and (ii) pulsed releases of volcanic sand and gravel retained by an upstream dam. 2. Levels of interstitial suspendable inorganic sediments increased by several orders of magnitude following ash inputs to the river, but returned to low levels within 3 months. Flushing of volcanic sand and gravel retained by the dam resulted in sediment deposition upstream of a large island where coarse material lodged firmly between larger benthic substratum elements in blue duck feeding habitat. 3. Changes in algal biomass appeared to largely reflect seasonal and hydrological influences, but the percentage inorganic content of periphyton increased significantly during both posteruption phases. 4. Diversity and abundance of blue duck food supplies on boulders and on the riverbed declined following the eruption, whereas significant impacts on biomass were only detected in benthic habitats which were more susceptible to sediment deposition. However, percent composition of the benthic and boulder invertebrate food resources appeared largely unaffected by the eruption. 5. There was no apparent association between the eruption and the composition or electivity (E*) of blue duck diet, but there was a significant increase in the percent inorganic content of faeces, suggesting a reduction in the quality of food rations. 6. Changes in food quantity and quality associated with deposition of volcanic sediments were linked to an observed decline in blue duck population density and fecundity following the eruption. An interacting continuum of adaptive responses to perturbation intensity and impact duration is proposed for blue duck, and potentially other long‐lived, riverine birds, that enable them to cope with disturbances in highly variable and heterogenous lotic environments.     

SYMBIOSIS IN THE PLANKTONIC FORAMINIFER,ORBULINA UNIVERSA,AND THE ISOLATION OF ITS SYMBIOTIC DINOFLAGELLATE,GYMNODINIUM BÉII SP. NOV.1

The symbiotic association of the spinose planktonic foraminifer, Orbulina universa, with the dinoflagellate, Gymnodinium béii sp. nov., was examined with light and electron microscopy, and the symbiont was isolated into unialgal culture. The intact association is characterized by a diurnal movement of the symbionts from the distal regions of the spines during the day, to perialgal vacuoles within the host cytoplasm at night. This diurnal migration involves a daily endo- exocytotic cycle. Gymnodinium béii is non-motile and spindle-shaped within the host, whereas it is motile and gymnodinoid in shape when in culture. Ultrastructural examination revealed two or more stalked pyrenoids penetrated by lamellae, a typical dinokaryon nucleus and no trichocysts. A distinct ‘flange’projects over the sulcus from the hypocone. The swimming behavior of this dinoflagellate was characterized by intermittent darting events. Swimming speeds during a dart reached velocities of 770 μm. s^?1 as compared to a mean, non-darting swimming velocity of 126 μm. s^?1. Gymnodinium béii is eurythermal and division rates ranged between 0.16 and 0.65 divisions day^?1 for culture temperatures between 6.5 and 25° C respectively.     

Vesicle transport and the cytoskeleton in the unicellular red alga Glaucosphaera vacuolata

Vesicles are continually transported from the perinuclear region to the cell's exterior in the unicellular red alga Glaucosphaera vacuolata Korshikov. This phenomenon is recorded here with time‐lapse videomicroscopy. The mechanism governing this intracellular motility is unknown but the cytoskeleton is believed to be involved. Microtubules and actin filaments are located in Glaucosphaera using fluorescently conjugated antibodies and FITC‐phallicidin, respectively. Microtubules radiate in all planes from the perinuclear region to the periphery whereas actin filaments form rings around migrating vesicles. This pattern of location might indicate that both microtubules and actin filaments are involved in vesicle transport. However, this conclusion is not confirmed directly because the thick mucilaginous wall material seemed to prevent the entry of cytoskeletal inhibitors. A video clip of vesicle movement is available at http://www.cytographics.com/ .     

Carotenoids found in Littorina littorea and their relationship to parasitic infection by larva trematodes

Littorina littorea from Long Island Sound feed primarily on algae: Chlorophyceae (three species) and Rhodophyceae (two species). Carotenoids from the algae accumulate in tissues of the snail in either an unchanged or a metabolized state. β-Carotene, the major pigment of green and red algae, was isolated from the foot, hepatopancreas, and nephridium of these snails. Six oxygenated carotenoids, not completely identified, were isolated from the same tissues. The snails show a variation in foot color from white to brown to red. L. littorea is parasitized by trematode larvae of Cryptocotyle lingua and Cercaria parvicaudata from which β-carotene and one oxygenated carotenoid were isolated. Contrary to previous work, there is no relation between foot color of the snail and parasitic infection. Neither age nor sex appears to have any relation to foot color. Although carotenoid pigments are known to cause the variation in foot color, the reasons or factors for their accumulation in the snail tissue have not been established. Some hypothetical explanations are discussed.     

NEW PYRENOID FORMATION IN THE BROWN ALGA,SCYTOSIPHON LOMENTARIA (SCYTOSIPHONALES,PHAEOPHYCEAE)1

The Scytosiphon lomentaria (Lyngbye) Link cell characteristically has only one chloroplast with a prominent protruding pyrenoid. We observed the appearance of a new pyrenoid in each chloroplast during first mitosis in zygotes of S. lomentaria, using the freeze substitution technique. At first, a pyrenoid matrix appeared within the outermost stroma, in which thylakoid triplets and ribosomes were absent. At this time, the surface of this part remained smooth. The old pyrenoid was covered with a pyrenoid cap on the cytoplasmic side, whereas there was no pyrenoid cap on the new pyrenoid before protrusion. Irregularly shaped membranous sacs containing fine granular materials associated with the cytoplasmic side of the new pyrenoid. The sacs fused with each other and changed conformation and finally transformed into the pyrenoid cap. The new pyrenoid gradually protruded toward the cytoplasm, and the new pyrenoid cap became curved along the surface of pyrenoid. Cytokinesis occurred, and each chloroplast had two prominent protruding pyrenoids in two‐celled zygotes. We examined immunolocalization of β‐1,3‐glucans within the pyrenoid cap with a monoclonal antibody, using EM. Gold particles indicating localization of β‐1,3‐glucans were detected in vacuoles but never in the pyrenoid cap. This observation suggests that the pyrenoid cap in brown algae contains no photosynthetic products such as polysaccharide.     

Varying foraging strategies of Labridae in seagrass habitats: Herbivory in temperate seagrass meadows?

The diets of five species of Labridae in south-western Australia were examined to determine whether: (1) grazing of seagrass and epiphytic algae is a prominent feature of the food web within the deeper seagrass meadows of this temperate region; (2) levels of grazing differ among different seagrass systems; and diets differ among these closely-related species. Fish were collected seasonally from three seagrass habitats mainly comprising either Posidonia sinuosa, Posidonia coriacea or Amphibolis griffithii between the summer of 1996/97 and spring of 1997. Consumption of considerable amounts of algae and seagrass by Odax acroptilus and seagrass by Haletta semifasciata indicates that macrophyte grazing by fish is a component of the trophic dynamics of south-western Australian seagrass meadows. O. acroptilus and H. semifasciata were both omnivorous, feeding on a range of epifauna, infauna and flora, whereas Siphonognathus radiatus, Neoodax balteatus and Notolabrus parilus were carnivorous, feeding predominantly on motile epifauna, such as molluscs and crustaceans. The level of macrophyte grazing is likely to be underestimated in temperate offshore meadows of P. sinuosa and A. griffithii where omnivorous labrids, monacanthids and terapontids are abundant. Stable isotope data for O. acroptilus from the study region suggest that animal prey is more important to tissue maintenance than macrophyte material. Macrophytes may be grazed to acquire attached animal prey or for fulfilling energy requirements. Based on the distribution of prey, it appears that species in A. griffithii meadows forage within and below the seagrass canopy, whilst species in P. sinuosa meadows are likely to forage towards the basal area of this seagrass.     

On the taxonomy of the Paleozoic red algae of the family Ungdarellaceae

The history of the genus Ungdarella and the family Ungdarellaceae is discussed. Data on thallus morphology in members of the family are analyzed. Three new genera, Ungdarelloides, Urtasimella, and Suundukella, and a new species of the genus Ungdarella, U. mitchaelensis sp. nov., are described. The type localities of these taxa are briefly outlined. All these taxa come from Middle Carboniferous carbonate rocks of the Subpolar and Southern Ural Mountains.     

Photosynthetic H<Subscript>2</Subscript> metabolism in <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis> (unicellular green algae)

Unicellular green algae have the ability to operate in two distinctly different environments (aerobic and anaerobic), and to photosynthetically generate molecular hydrogen (H₂). A recently developed metabolic protocol in the green alga Chlamydomonas reinhardtii permitted separation of photosynthetic O₂-evolution and carbon accumulation from anaerobic consumption of cellular metabolites and concomitant photosynthetic H₂-evolution. The H₂ evolution process was induced upon sulfate nutrient deprivation of the cells, which reversibly inhibits photosystem-II and O₂-evolution in their chloroplast. In the absence of O₂, and in order to generate ATP, green algae resorted to anaerobic photosynthetic metabolism, evolved H₂ in the light and consumed endogenous substrate. This study summarizes recent advances on green algal hydrogen metabolism and discusses avenues of research for the further development of this method. Included is the mechanism of a substantial tenfold starch accumulation in the cells, observed promptly upon S-deprivation, and the regulated starch and protein catabolism during the subsequent H₂-evolution. Also discussed is the function of a chloroplast envelope-localized sulfate permease, and the photosynthesis–respiration relationship in green algae as potential tools by which to stabilize and enhance H₂ metabolism. In addition to potential practical applications of H₂, approaches discussed in this work are beginning to address the biochemistry of anaerobic H₂ photoproduction, its genes, proteins, regulation, and communication with other metabolic pathways in microalgae. Photosynthetic H₂ production by green algae may hold the promise of generating a renewable fuel from nature’s most plentiful resources, sunlight and water. The process potentially concerns global warming and the question of energy supply and demand.     

Salt lakes of the northern agricultural region,Western Australia

A survey of 11 sites covering three large (>10 km long, 6 sites) playa lakes and four pans (<1 km², 5 sites) of the Yarra Yarra salt lake system in the Northern Agricultural Region of Western Australia commenced in 2001. These salt lakes are shallow and ephemeral, with inundation being more regular following winter rainfall, but summer inundation also occurred in 2001. Salinity was generally higher in playas (156–368 g l⁻¹) than pans (30–284 g l⁻¹), but salinity responded noticeably to heavy rainfall events, especially in pans. pH values in the playa lakes (6.68–7.82) were less variable than in the pans (6.81–8.08). The range of dissolved oxygen concentrations was greater in pans (3.7–14.4 mg l⁻¹) than in playas (3.9–8.2 mg l⁻¹). Cationic concentrations generally followed the pattern of sea water cation dominance. Benthic microbial communities comprised either cohesive to loosely mucilaginous mats, or thin films of diatoms. Five genera of diatom and two species of filamentous cyanobacteria were recorded. Guest Editor: John M. Melack Saline Waters and their Biota