Fish and decapod crustaceans inhabiting drifting algae in Jervis Bay,New South Wales

Abstract This study documents the fish and decapod crustaceans inhabiting a bed of Gracilaria verrucosa that was drifting on the bottom of a temperate marine embayment in relatively deep water (15- 18m) during autumn 1991. Fauna were sampled with diver-operated enclosure nets. Relatively few species inhabited the algae at this time, and the assemblage was primarily a subset of that in adjacent Posidonia australis beds. Three fish species [Neoodax balteatus (Odacidae), Cristiceps australis (Clinidae), Siphamia cephalotes (Apogonidae)] and one species of crab [Nectocarcinus tuberculosus (Portunidae)] dominated the catches numerically. A further 14 fish and decapod species were relatively rare. Neoodax balteatus, C. australis and N. tuberculosus were caught at all life stages and appeared to be permanent residents of the Gracilaria. Few juveniles of other species were captured, which indicates that these algal wracks may not be an important nursery habitat for seasonally resident fish species. Trachurus novaezelandiae and a number of other fish species that associate with a variety of benthic habitats appeared to be transient visitors. The biomass of algae varied significantly within the bed, but algal biomass was not a good indicator of faunal abundances. The low species richness of the fish and decapod crustacean assemblage may be related to both lower recruitment in deeper water and to unfavourable characteristics of the alga.     

Effect of K+, its Counter Anion, and pH on Sodium Efflux from Barley Root Tips

Sodium efflux from ²²Na⁺-loaded root tips root tips of Hordeumvulgare L. was markedly increased by replacing 10mM Na₂SO₄ inthe washing solution by K₂SO₄ with the same electrical conductivity.This increase was inhibited by both an uncoupler and an inhibitorof oxidative phosphorylation but not by ouabain. Potassium ionsdid not enhance Na⁺ efflux in the presence of a rapidly absorbedcounter anion, such as Cl^–, instead of . Efflux of ²²Na⁺ could also be enhanced by a low pH in theabsence of K⁺; this was prevented by uncouplers, but not byan inhibitor of the mitochondrial ATPase. It seems that K⁺ indirectly enhances Na⁺ efflux. It is suggestedthat metabolic K⁺ uptake in excess of the counter anion resultsin a proton gradient across the plasmalemma (acid outside) inducingH⁺/Na⁺ antiport.     

The Effect of ATP on Uptake of Monovalent Cations and Anions by Red Beet Slices

Externally added ATP inhibits sodium and potassium uptake byred beet tissue; this inhibition seems to be competitive. Theeffects of DNP and ATP additions on cation uptake were foundto be additive. ATP did not inhibit chloride and bromide uptake.The results and their implications are discussed.     

Non-specificity of Salt Effects on Mg2+dependent ATPase from Grass Roots

The effect of tris, choline, and ethanolamine chlorides on theactivity of Mg^2–dependent ATPase in membrane fractions(cell walls, mitochondria, and microsomes) of Zea mays L. (cv.Neve Yaar 22), Avena saliva L. (cv. Mulga), and Hordeum vulgareL. (cv. Omer) was compared with the effect of KC1 and NaCl.Considerable salt effects on apparent Mg²⁺ATPase activity werefound only at relatively high pH values (8.2) at which Mg²⁺.ATPaseactivity was low in the absence of monovalent cation salts.The Mg²⁺-dependent ATP hydrolysis by ATPases from all the membranefractions increased in the presence of at least one of the organiccations to the same extent as in the presence of KCI or NaCl.The monovalent organic cations are only very slowly absorbedby corn roots in comparison with K⁺ and Na⁺. It is concluded that monovalent salt effects on ATPase fromthese plant roots are not cation specific and not related tothe capability of root cells to absorb cations. Present evidencefor the existence of a cation-transport ATPase in plant tissueis critically reviewed.     

Rubidium and Potassium Absorption by Bean-leaf Slices Compared to Sodium Absorption

At salt concentrations of 0.1 mM as well as of 5.0 mM, the ²²Na⁺ absorption capacity of bean (Phaseolus vulgaris L. cv. ‘Brittle Wax’) leaf tissue increased during the period of leaf expansion and decreased rapidly after leaf maturation. The absorption capacity for ⁸⁶Rb⁺ and ⁴²K⁺ was highest in very young leaves and decreased continuously in expanding and in mature leaves. The ⁸⁶Rb⁺ absorption capacity of mature leaves was not increased by detopping the plants; this senescence-retarding treatment more than doubled ²Na⁺ absorption. The absorption of ²²Na⁺ by bean-leaf slices was not enhanced by light, whereas ⁸⁶Rb⁺ and ⁴²K⁺ absorption was much affected. Previously absorbed ⁸⁶Rb⁺ and ⁴²K⁺ were more available for exchange than ²²Na⁺.     

Alterations in periphyton characteristics due to grazing in a Cascade foothill stream

SUMMARY 1. In situ experiments were conducted in a Washington stream to quantify the effects of grazing by a caddisfly larva, Dicosmoecus gilvipes (Trichoptera: Limnephilidae), and a mayfly nymph, Nixe rosea (Ephemeroptera: Heptageniidae) on periphyton biomass, structure, and function.
2. Dicosmoecus gilvipes reduced periphyton biomass from 92 mg m⁻²(as mean chlorophyll a ) to 33 mg m⁻². The grazed assemblage was less diverse and composed of smaller, closely attached diatoms, whereas there was a higher proportion of overstorey and filamenttius algae in the diverse, ungrazed periphyton.
3. By maintaining the periphyton community as a thin layer of diatoms, grazing by D. gilvipes appeared to promote a healthier, more vigorous community relative to the ungrazed mat, which became senescent in the latter part of the experiment.
4. Nixe rosea had little measurable effect on any characteristics of the periphyton measured. These nymphs apparently preferred small diatoms, which resulted in only micro-scale alterations in periphyton characteristics that were difficult to detect.
5. Biomass accrual of ungrazed and grazed periphyton was described by the logistic growth equation. Loss of biomass due to grazing by D. gilvipes or to senescence and sloughing were incorporated in the model to account for changes in grazed and ungrazed periphyton. respectively. Proposed mechanisms which described biomass accumulation were largely sup ported by model predictions.     

Energetics of 22Na+ Absorption by Bean-leaf Slices

Sodium absorption by bean-leaf slices from o·1 mM ²²NaCldepends on metabolic energy, but is not enhanced by light. Lightalso does not effect the ATP content of the tissue. Inhibitorsof energy metabolism which decrease the ATP content also inhibit²²Na⁺ absorption. In darkness, anoxia severely affects the ATPcontent as well as ²²Na⁺ absorption; illumination restores bothto almost normal values.     

The Effect of Dichlorophenyldimethylurea on Light-Stimulated 22Na+, 42K+ and 86Rb+ Absorption in Different Tissues of Phaseolus vulgaris Leaves

The light-stimulated absorption of ⁸⁶Rb⁺ by Phaseolus vulgaris L. leaf slices was found to be sensitive to dichlorophenyldimethylurea in air as well as in nitrogen, whereas light-stimulated ²²Na⁺ absorption in nitrogen was not sensitive to this inhibitor. The absorption of ²²Na⁺ is not affected by light in air. The absorption of ⁴²K⁺ is enhanced by a dichlorophenyldimethylurea-insensitive light effect under anaerobic conditions and further increased by light in the absence of the inhibitor. Light-enhanced ⁴²K⁺ absorption in air was also inhibited by dichlorophenyldimethylurea. Previous work showed that light-stimulated ⁸⁶Rb⁺ and ⁴²K⁺ absorption by Phaseolus vulgaris leaf slices is restricted to the guard cells. The present results are discussed with reference to the effect of light on stomatal opening.