Occurrence of aquatic invertebrates of the wheatbelt region of Western Australia in relation to salinity

The wheatbelt region of Western Australia has been extensively cleared of indigenous vegetation for agriculture and is now severely affected by dryland salinity. Wetlands that were once freshwater are now saline and others are under threat, as are the animals and plants that inhabit them. Rising groundwater is also affecting the many naturally saline playas. To provide a framework for setting conservation priorities in this region a biological survey was undertaken, including sampling of aquatic invertebrates at 230 wetlands. In this paper, we have used data from the survey to summarise occurrence of species in relation to salinity. Total species richness at a wetland showed no response to salinity below 4.1 g l⁻¹ and then declined dramatically as salinity increased. When halophilic species were excluded from consideration, species richness was found to decline from 2.6 g l⁻¹. These patterns are compared to previous studies of richness-salinity relationships. There is some evidence that the freshwater invertebrate fauna of the wheatbelt may be comparatively salt tolerant, with 46% of freshwater species collected at salinities above 3 g l⁻¹ and 17% above 10 g l⁻¹, though these proportions differed between various invertebrate groups. While this tolerance will provide a buffer against the effects of mild salinisation, many species are at risk of regional extinction as salinisation becomes more widespread.     

Aquatic macrophyte composition in relation to environmental factors of irrigation ponds around Lake Shinji,Shimane, Japan

A comparative study of aquatic vegetation of 149 irrigation ponds in the surrounding area of Lake Shinji, Shimane Prefecture, Japan, was done to document the present status of aquatic flora and water chemistry. In addition, influence of 17 environmental factors on the between-pond variation in aquatic macrophyte composition was assessed by using detrended correspondence analysis (DCA). A total of 38 taxa were recorded, and the most frequent taxon was Trapa spp. (>50%). Number of taxa per pond ranged from 1 to 14 and mean number was 4.1. Floristic composition was primarily related to variation of the factors such as conductivity, Mg, Ca, Na, alkalinity, altitude, pH and depth. In contrast, no significant correlations were found with total P, PO₄-P, transparency, COD, ignition loss of bottom soil, Mn and Fe. Of the 33 significant species associations between 19 species with more than 5% frequency occurrence, 28 were positive and the remaining 5 were negative. All of these negative associations involved Trapa spp., and not only water chemistry but some other factors like competition and bottom soil preference were assumed to influence species associations.Abbreviations (DCA) Detrended Correspondence Analysis     

Influence of salinity on the bacterial community composition in Lake Bosten, a large oligosaline lake in arid northwestern China

Salinity was found to be the dominating contributor controlling bacterial community composition (BCC) and the abundance of Betaproteobacteria in the oligosaline Lake Bosten. The high percentage of unclassified bacteria inhabiting this unique habitat highlights the potential ecological importance of BCC in the early stage of lake salinization and eutrophication.     

Experimental effects of elevated salinity on three benthic invertebrates in Pyramid Lake,Nevada

Salinity of Pyramid Lake increased from 3.7 to 5.5 between 1933 and 1980. Concern over future reductions in overall species richness prompted experiments to assess responses of dominant lake organisms to elevated salinity. Salinity tolerances of three important benthic invertebrates, Hyalella aztecta, Chironomus utahensis, and Heterocypris sp., were tested in controlled laboratory bioassays and also in a semi-natural environment consisting of large (47 m³) mesocosms.Densities of H. azteca in mesocosms were significantly lower at salinities of 8.0 and 11.0 compared with 5.6 controls in year one, but not in 8.5 salinity mesocosms in year two. The 96-h LC₅₀ for H. azteca was high at 19.5. Short-term mortalities of C. utahensis were 100% at salinities of 13.3 and greater. Fifty-seven percent fewer larvae matured from third to fourth instar at 8.9 than at 5.5 salinity in 17 day subacute bioassays. Furthermore, larval chironomid densities and emergence of adults from mesocosms were significantly reduced at salinities of 8.0 and higher compared with controls. Mortality of Heterocypris sp. was 50% at a salinity of 18.6 in laboratory bioassays and populations in mesocosms ranged between 40 and 100% lower at salinities of 8.0 and 11.0 than in controls.Multiple generation mesocosm experiments indicated all three invertebrates were more sensitive to elevated salinity than results of short-term bioassays. Our studies suggest populations of these invertebrates may be reduced from present levels if Pyramid Lake's salinity were to double, although none are expected to be extirpated. Food habit shifts and reduced production of lake fishes are likely consequences of salinity-induced disruption in the benthic invertebrate forage base.     

Coastal plain halophytes and their relation to soil ionic composition

Halophytic coastal communities in Bahia Blanca, Argentina, were examined in relation to soil salinity along a transect from inland to the sea. The relationships between soil electrical conductivity and dominance-abundance values for different species were determined. The Chañaral community with its most conspicuous species Geoffroea decorticans was present in soils with the lowest salinity levels in the area. Halophytic underbush develops at soil salinity values of intermediate soil electrical conductivity, the characteristic species being Cyclolepis genistoides, Atriplex undulata and Salicornia ambigua. Halophytic shrub-like steppe vegetation, dominated by Allenrolfea patagonica or Heterostachys ritteriana, is present in soils with high salinity. It is concluded that the ionic composition of plants was a stable characteristic for different species and did not vary with changes in soil salinity.     

Effects of salinity and waterlogging on the vegetation of Lake Toolibin,Western Australia

Increased rates of tree senescence and mortality in and adjacent to an ephemeral lake in the Western Australian wheatbelt have been attributed to increased levels of soil salinity and inundation following agricultural clearing. Winter lake salinities approximate freshwater lake values, but during periods when the lake is dry, capillary rise of groundwater is thought to increase surface soil salinity. An undescribed species of Melaleuca and Casuarina obesa dominated the seasonally inundated regions of the lake bed. Aeolian deposits of higher elevation were dominated by Eucalyptus loxophleba, Allocasuarina huegeliana or species of Banksia. Woodland of E. oleosa var. longicornis and E. salmonophloia occurred predominantly on upland fluviatile deposits of sand and sandy clays. Measurements of soil salinity and the calculation of percentage inundation from tree elevations and observations of tree vigour and xylem pressure potential response indicated that tree deaths in Melaleuca sp. and C. obesa were due to increased levels of salinity. Deaths and low vigours in E. rudis were attributed to both increasing salinities and prolonged inundation. We believe control of ground water levels should be a major consideration in the preservation of this ephemeral lake and the water fowl populations it supports.     

Aquatic macrophytes of Lake Bled: changes in species composition,distribution and production

The macrophytes of Lake Bled were studied from 1987 to 1990. Three main factors influenced the decline of the aquatic vegetation in the lake during that period: (1) reduced light in the littoral zone due to an increase in phytoplankton (2) grazing by herbivorous fish and waterfowl, and (3) direct human impact.     

The aquatic macrophyte flora of saline wetlands in Western Australia in relation to salinity and permanence

This paper reports a study of fluctuations of salinity, permanence and macrophyte occurrence in a wide range of saline wetlands between 1978 and 1982. Monitoring of salinity and depth of wetlands reserved for the conservation of flora and fauna began in 1978 as part of a Fisheries and Wildlife programme to annually assess conditions for waterfowl breeding. Over 100 reserves have gauges which are monitored at two monthly intervals. Cataloguing of the macrophytes in these reserves began in 1980 and has continued through 1982. Species of the two monocotyledon genera Ruppia and Lepilaena and the charophyte Lamprothamnium show wide tolerance of both salinity fluctuation and habitat drying. These plants occur in both permanent and ephemeral wetlands with salinities which show extremely large seasonal salinity fluctuations from slightly saline to hypersaline. The potential use of data on macrophytes in wetland management is considered.     

Osmotic and ionic haemolymph concentrations in the Baltic Sea amphipod Gammarus oceanicus in relation to water salinity

The aim of this work was to determine the osmotic and ionic (Na(+), K(+), Ca(2+), Mg(2+) and Cl(-)) haemolymph concentrations in Gammarus oceanicus at different salinity levels. Being a species of marine origin it inhabits brackish waters of the Baltic Sea. G. oceanicus specimens were collected in January 2003 from the Gulf of Gdansk (salinity 7 psu). The animals were gradually acclimated to eight different salinity levels (5, 7, 14, 20, 25, 30, 35 and 41 psu) at a temperature of 5 degrees C and 100% oxygen saturation. The haemolymph osmolalities correlated positively with external salinity, from 545.4+/-17.3 mOsm in 5 psu to 1185.9+/-34.6 mOsm in 41 psu. G. oceanicus hyperregulated within the 5-31.5 psu range; above 31.5 psu it hyporegulated its body fluids in comparison to the external medium. At 31.5 psu (1017 mOsm) the haemolymph concentration of G. oceanicus was isoosmotic with the habitat. The haemolymph concentrations of all the studied ions, except K(+), correlated positively with their concentrations at the various salinity.     

Taxonomy of estuarine invertebrates in Australia

An Australian estuary is primarily a marine-dominated environment, subjected to major salinity changes only after heavy rains and during flood conditions. In southeastern Australia estuarine biota are similar to those in shallow coastal bays and some of the coastal lagoons, and most taxonomic studies on estuarine fauna have occurred in this region. Several major surveys of estuarine and coastal bays have been undertaken in Australia during the past three decades and these surveys have largely provided the material for taxonomic studies of the major groups of macrobenthos. All these studies have revealed a diverse and abundant benthic macrobenthos. The composition of estuarine invertebrate fauna is compared with open exposed coasts, including fauna found in soft strata and on hard strata. Australia has a limited specialized estuarine biota much of which is restricted to particular habitats, and a highly diverse marine community which thrives in the sheltered protected waters of estuaries and the associated soft sediments. Currently, interactive computer-based keys are being developed which should greatly assist the student and the benthic ecologist to identify the fauna and prevent potential loss of data. Some aspects of the current debate of the level of taxonomic resolution required to answer various ecological questions are discussed. Finally, some comments are suggested as to future directions in which taxonomists and estuarine ecologists should proceed in order to be able to detect changes or losses of estuarine biodiversity and the loss of the associated biological information which may be critical in understanding the functioning of the estuarine ecosystem.     

Extreme water level decline effects sediment distribution and composition in Lake Alexandrina,South Australia

Water level decline affects the biophysical environment of shallow lakes. Unprecedented drought in Australia’s Murray–Darling Basin resulted in extreme water level drawdown in the large, shallow Lake Alexandrina at the end of the River Murray. Surface sediment was collected from 22 sites in the lake before and after water levels declined to assess the integrated limnological changes over the period of drawdown. Results indicate an increase in the proportion of organic particles in profundal sediments, as well as an increase of fine particles (<19.9 μm) in peripheral sediments. These changes to sediment composition corresponded to higher concentrations of suspended particles at low water levels. Increased autochthony and a shift in primary production from macrophytes to phytoplankton in Lake Alexandrina support these findings. Inorganic carbon and other nutrients were lost from sandy sediments most likely through carbonate dissolution driven by a localized decrease in pore water pH from increased mineralisation of organic matter.     

Inferred ionic composition and salinity of a Bolivian Quaternary lake,as estimated from fossil diatoms in the sediments

Multiple Linear Regression (MLR) was used to estimate past salinity and ionic composition in sediments of a paleolake in the southernmost Bolivian Altiplano. Modern diatom assemblages were sampled from the subsurface sediments of 14 saline lagoons, and compared quantitatively with fossil assemblages. Only one application of the method is reported: to a Quaternary outcrop located on the border of one of them (Laguna Ballivian). Multivariate analysis was performed on diatom data to check the range of variation of both the fossil and modern flora. It also allowed a reduced set of explanatory variables for regression analysis. Finally, a number of transformations of the chemical variables was computed prior to the regression process in order to stabilize the residuals variance and obtain a good error estimate. Only ten chemical components were studied, but the method could be applied to other palaoenvironmental parameters.     

Macro-floral assemblages in upland Welsh streams in relation to acidity, and their importance to invertebrates

SUMMARY 1. Macro-flora (angiosperms. bryophytes and macroscopic algae) and macroinvertebrates were sampled in 1984 at eighty-eight sites on soft-water streams in upland Wales. Assemblage patterns were related to stream chemistry using TWINSPAN, DECORANA and multiple discriminant analysis.
2. Floral assemblages could be related most strongly to pH and aluminium concentration, with Scapania undulata, Nardia compressa and filamentous chlorophytes characterizing streams of mean pH5.2–5.8, whilst Fontinalis squamosa occurred mostly at pH 5.6–6.2 and Lemanea at pH 5.8–7.0. We propose an indicator system based on thesetaxa.
3. Assemblages of invertebrates and flora concorded highly significantly, sites with Scapania and Nardia holding impoverished faunas. Because some acid sensitive invertebrates (e.g. Ecdyonurus and Ancylus ) can feed from acid tolerant plants (e.g. Scapania ), we hypothesize that they are restricted physiologically from acid streams.     

Growth,ion composition,and stomatal conductance of peas exposed to salinity

Availability of irrigation water of appropriate quality is becoming critical in many regions. Excess salt in irrigation water represents a risk for crop yield, crop quality, and soil properties. During the short vegetation period, field peas require high amounts of water, and irrigation is often indispensable for successful production. Steady presence of NaCl (0.1, 0.2, 0.6 or 1.2 g NaCl L⁻¹ in 1/2 strength Hoagland nutrient solution) under semi-controlled conditions reduced growth and resulted in shorter vegetation. Disturbances in the peas’ water regime were provoked by NaCl, as water content in pea tissues was reduced and stomatal density and stomatal diffusive resistance increased in the presence of higher NaCl concentrations. Concentration of Na⁺ increased in all pea tissues with increased NaCl concentration in the nutrient medium. In the presence of NaCl, concentrations of K⁺, Ca²⁺ and P_i increased in roots, stems and leaves, and decreased and in pods and grains. Concentration ratios Na⁺/K⁺, Na⁺/Ca²⁺, K⁺/Ca²⁺ and (Na⁺+K⁺)/Ca²⁺ in various plant parts were affected as well, but magnitudes of changes were variable. Continuous presence of NaCl in concentrations frequently met in irrigation waters significantly reduced pea growth, impaired the water regime, and altered plant chemical composition.     

Growth,physiological, biochemical and ionic responses of pistachio seedlings to mild and high salinity

Key message

Depending on salt concentrations, different mechanisms are involved in the tolerance of pistachio and an acclimation to salinity conditions occurs in the leaves that develop in the presence of salt.

Abstract

Pistachio (Pistacia vera L.) is a salt tolerant species that is considered an alternative crop for cultivation in salinzied orchard soils. In this work, 12-week-old pistachio seedlings cultivated in soil under greenhouse conditions were treated with five levels of salinity including control (0.63 dSm^?1), low (2 and 4 dSm^?1) and high (8 and 10 dSm^?1) salt concentrations for further 12 weeks. Plant growth parameters were not affected by mild salinity; a significant reduction was only observed from 8 dSm^?1. Considerable differences were observed between the young and mature leaves regarding osmotic and ionic stress effects of salt. Main compatible solutes were proline in mature leaves, proline and soluble sugars in young leaves, and soluble sugars and amino acids, other than proline, in roots. Concentration and content of Na in the leaves were not significantly increased at low levels of salinity and the K:Na and Ca:Na ratio of leaves were affected only by higher salt concentrations. Using the sequential extraction procedure for cell wall isolation, we observed that both absolute and relative amounts of Na in the cell wall fraction increased under low salinity, while decreased under higher levels of salt supply. Stable water relations, photochemistry and CO₂ assimilation rates particularly of young leaves, as well as ion homeostasis were mechanisms for maintenance of plants growth under mild salinity. Under severe saline conditions, the impaired ability of mature leaves for synthesis of assimilates, preferent allocation of carbohydrates to roots for maintenance of osmotic homeostasis and finally, reduction of protein synthesis caused growth inhibition in pistachio.     

Aquatic insects in an estuarine environment: densities, distribution and salinity tolerance

1. Aquatic insects were quantitatively surveyed at five sites along the tidally influenced section of a river-dominated estuary in North Wales. Site 1 was the furthest upstream and was established as a reference site as it was never inundated by salt water. Site 5 was the furthest downstream and was inundated by all incoming tides. Numerically, insects made up 32% of the estuarine invertebrate fauna. 2. Although the densities of most insect taxa decreased towards the estuary mouth, there were significant numbers present downstream for much of the year; for example, in April at site 4 (which was inundated by 81% of all high tides), a mean of 3514 chironomid larvae were recorded per m² of estuary bed. Even at site 5, which was inundated twice daily, there were 747 larvae per m². Among the larger aquatic insects, caddisfly and elmid beetle larvae, together with stonefly nymphs, were consistently taken at site 4 (e.g. maxima of forty-eight caddisfly larvae m^–2 in December and seventy elmids m^–2 in April), although their densities were lower than upstream. 3. There were seasonal shifts in the longitudinal distribution of several taxa, most notably the extension of chironomids down the estuary in April and July, and the concentration of simuliid larvae and mayfly nymphs at site 2 in July. The total freshwater benthos showed a downstream shift between September and December, which was maintained through April and into the summer. The latter was despite peak saltwater inundation (highest tides) in October, November and April. In June and July, when saltwater intrusion was lowest, the ranges of many aquatic insects had contracted to sites 1 and 2. 4. Laboratory experiments showed that virtually all individuals of nineteen species of insects collected from site 1 (freshwater) survived a 4-h immersion in 8.75‰ saltwater (25% strength seawater). Immersion in progressively more saline solutions reduced the survivorship of first the mayflies, followed by the caddisflies Glossosoma conformis and Hydropsyche instabilis. After 4 h in full strength seawater, all specimens of the stonefly Dinocras cephalotes, over half of the Perla bipunctata, and some individuals of nine species of caddisfly were alive. Four species of caddisfly (Sericostoma personatum, Odontocerum albicorne, Potamophylax cingulatus and Adicella reducta) survived a 24-h simulated tidal cycle of immersion. With the exception of P. cingulatus, a few individuals of these caddisfly species survived immersion in full-strength seawater for 24 h. For some individual species there was good agreement between their observed longitudinal distribution in the estuary and laboratory-measured salinity tolerance; however, there was no significant correlation, overall, for the fauna.     

Resistance of larvae of common species of White Sea invertebrates to extreme changes in salinity

This study examines the effect of sharp changes in salinity on pelagic larvae of ten common species of invertebrates from the brackish White Sea (Mollusca, Polychaeta, Echinodermata, Cnidaria, Ascidia). For five species, the low salinity resistance limit was in the range of 8–12‰: for the gastropod Littorina littorea, it was below 8‰; for Dyaphana sp. and the bivalves Hiatella arctica and Heteranomia ovata, it was more than 12‰; and for the ascidian Styela rustica, it was 16‰. About 50% of larvae of four investigated species were able to withstand high salinity and survived at 36–40 and even 50‰ (Littorina). Larvae of littoral-sublittoral species proved to be more euryhaline than larvae of sublittoral species.     

Osmotic and ionic hemolymph concentrations of bathyal and abyssal amphipods of Lake Baikal (Siberia) in relation to water depth

We studied the adaptive variations of the hemolymph concentrations in relation to water depth and pressure using deep-dwelling amphipods from Lake Baikal. Hemolymph osmolality was determined in six bathyal and abyssal species immediately after capture when values come closest to the habitat concentrations. In three species, hemolymph osmolalities correlated positively with depth of capture. Prevalent ions in the hemolymph are sodium and chloride. Lactate, our indicator for capture stress, was highest after trawling (2–6 mM) and lowest after retrieval from cages (0–0.6 mM). Acclimation to different pressure was studied by exposing the specimens to different water depths over several days. Hemolymph concentrations did not change after acclimation to surface pressure in the sublittoral Acanthogammarus albus, a native also to shallow water, but decreased by 30–80 mosmol/kg H₂O in the bathyal and abyssal species Acanthogammarus grewingki, Acanthogammarus reicherti, and Parapallasea lagowskii. Similarly, hemolymph osmolality decreased in A. reicherti and P. lagowskii originating from deep water, when acclimated to reduced water depth, and, in A. reicherti hemolymph osmolality reached its original high value when returned to the depth of capture. Higher hemolymph osmolalities and NaCl concentrations, demonstrated here for the first time, may provide selective advantages to abyssal species. Accepted: 24 August 2000     

Biosynthesis, translocation, and accumulation of betaine in sugar beet and its progenitors in relation to salinity

Like other halophytic chenopods, sugar beet (Beta vulgaris L.) can accumulate high betaine levels in shoots and roots. N,N,N-trimethylglycine impedes sucrose crystallization and so lowers beet quality. The objective of this research was to examine the genetic variability and physiological significance of betaine accumulation in sugar beet and its relatives. Three cultivated genotypes of B. vulgaris and two genotypes of the wild progenitor B. maritima L. were grown with and without gradual salinization (final NaCl concentration = 150 millimolar). At 6 weeks old, all five genotypes had moderately high betaine levels in shoots and roots when unsalinized (averages for all genotypes: shoots = 108 micromoles per gram dry weight; roots = 99 micromoles per gram dry weight). Salinization raised betaine levels of shoots and roots 2- to 3-fold, but did not greatly depress shoot or root growth. The genotype WB-167—an annual B. maritima type—always had approximately 40% lower betaine levels in roots than the other four genotypes, although the betaine levels in the shoots were not atypically low.

The site and pathway of betaine synthesis were investigated in young, salinized sugar beet plants by: (a) supplying 1 micromole [¹⁴C]ethanolamine to young leaf blades or to the taproot sink of intact plants; (b) supplying tracer [¹⁴C]formate to discs of leaf, hypocotyl, and taproot tissues in darkness. Conversion of both ¹⁴C precursors to betaine was active only in leaf tissue. Very little ¹⁴C appeared in the phospholipid phosphatidylcholine before betaine was heavily labeled; this was in marked contrast to the labeling patterns in salinized barley. Phosphorylcholine was a prominent early ¹⁴C metabolite of both [¹⁴C]ethanolamine and [¹⁴C]formate in all tissues of sugar beet. Betaine translocation was examined in young plants of sugar beet and WB-167 by applying tracer [methyl-¹⁴C]betaine to a young expanded leaf and determining the distribution of ¹⁴C after 3 days. In all cases, extensive ¹⁴C translocation to young leaves and taproot sink occurred; neither in the fed leaf nor in sink organs were any ¹⁴C metabolites of betaine detected.