Bacterial biomass and productivity in sediments,stromatolites, and water of hamelin pool,shark bay,Western Australia

Heterotrophic bacterial biomass and growth rates were examined in stromatolites formed from four different types of benthic cyanobacterial mats. Bacteria in algal mats were counted using direct microscopy and biomass was estimated from the numbers of bacteria. Heterotrophic bacterial growth rates were estimated from the rate of incorporation of tritiated thy‐midine into DNA. Pustular mat, which occurs in the upper in‐tertidal zone, contained relatively few bacteria in the surface layers (0–5 mm), having about 0.2 x 10⁶ cells mm^‐3, or 20 mgC m^‐2 per millimetre depth. Other mats in the lower intertidal and subtidal zones had from 1 x 10⁶ cells mm^‐3 to 8 x 10⁶ cells mm^‐3. Heterotrophic bacterial productivities were 2.1 to 5.0 mgC m^‐2 h^‐1. Turnover times were an average of 1 day in the sandy sediment and 5 days in the colloform mat. Although these results are minimum estimates, they indicate that heterotrophic bacteria contribute substantially to the carbon cycle in stromatolites, by utilizing about 20 to 30% of primary production.     

The loss of seagrass in Cockburn Sound,Western Australia. II. Possible causes of seagrass decline

This paper examines possible reasons for the extensive loss of seagrass in Cockburn Sound following industrial development. Transplanted seedlings survived poorly in Cockburn Sound compared with an adjoining embayment. Altered temperature, salinity, sedimentation and water movement do not explain the death of seagrass over wide areas, and there is no evidence for a role of pathogens. Oil refinery effluent reduced seagrass growth in aquaria at concentrations similar to those at the point of discharge, but could not account for the widespread deterioration observed in the field. Severe grazing by sea urchins was observed on meadows already under stress and does not appear to be a primary cause of decline; caged, transplanted seedlings also deteriorated.Increased light attenuation by phytoplankton blooms may have affected the ddepth to which seagrasses could survive, but would have had little significant effect in shallow water; marked phytoplankton blooms were recorded only after extensive seagrass decline had taken place. Light reduction by enhanced growth of epiphytes and loose-lying blankets of filamentous algae in nutrient enriched waters is suggested as the most likely cause of decline. Heavy epiphyte fouling was consistently observed on seagrasses in deteriorating meadows, as well as on declining, transplanted seedlings, and is known to significantly impair photosynthesis in other systems. Extensive seagrass decline coincided with the discharge of effluents rich in plant nutrients.     

The cichlid fishes of Guyana, South America, with notes on their ecology and breeding behaviour

Field studies in Guyana, north-eastern South America, from 1957 to 1962 included observations on the ecology and behaviour of cichlids in natural waters. Collections made were examined at the British Museum (Natural History) together with other cichlid material from Guyana. This paper records these observations and gives keys for the field indentification of these cichlids. Fifteen genera comprising at least 35 species occur in Guyana, mostly species with a wide distribution in tropical South America. In the predatory Cichla ocellaris which grows larger than other South American cichlids, growth continues long after the fish matures. Males tend to be larger than associated females. The behaviour of Cichla ocellaris and Cichlasoma festivum when guarding their young suggests that the caudal ocellus has a vital role in the orientation of young to parent. Most of these cichlids in which breeding habits are known are substratum-spawners. An attachment gland, producing viscous threads, was found on the heads of recently hatched Geophagus jurupari young, although this species carries the young in the mouth.     

Seed germination ecology in southwestern Western Australia

Germination responses of species from the native plant communities of southwestern Western Australia can be related to syndromes of life history, fire response, and seed storage, and also to factors related to environmental stress. The Mediterranean-type climate of the region with periodic drought and recurrent fires affects the production of viable seeds in plants of limited stature and rooting depth. Fire response ephemerals and species cued to flower by fire tend to produce viable, readily germinable seeds, but there are instances where seed production is aborted in these predominantly herbaceous life forms. Clonal, rhizomatous species often produce mainly inviable seeds. Production of viable seeds in woody species of these highly diverse communities may also be restricted by limitations to cross pollination. Obligate post-fire seeding species tend to produce a greater proportion of viable seeds than species which are capable of resprouting following fire. Serotinous species, whether post-fire re-seeders or post-fire resprouting species, produce mainly viable seeds, which germinate readily once freed from protective fruits. Species of the legume families and a few others of the soil seed bank produce innately dormant seeds which can be germinated following heat shock treatments which simulate the effects of fire. Heat shock in these species appears mainly as a mechanism to crack the hard seed coats, but the effect of heat to denature seed coat inhibitors has not been eliminated. Western Australian species do not seem to break dormancy when exposed to leachates from burned wood as has been observed in comparable habitats in California and South Africa, but further research is advised. Germination in many native southwestern Australian species is cued by temperatures that correspond to the winter rainfall period. There are also indications that an after-ripening period of warm, dry storage increases percentage of germinable seeds. Stimulation of germination by hormones is almost unresearched in Western Australia, but germination percentages have been increased in a small number of species of horticultural potential. Stimulation of germination by soil nutrient concentrations is almost unresearched in Western Australia, except for the inhibitory effect of excess sodium chloride levels inEucalyptus andMelaleuca. These species only germinate when osmotic effects are reduced to lower levels as would occur when winter rains dilute soil salts. Application of research on seed germination has already enhanced the establishment of seedlings in the restoration of mine sites and is becoming important in aspects of the breeding and selection of native plants for the cut flower, bedding plant and essential oil industries.     

The distribution and ecology of coastal species on roadsides

The invasion of roadsides by coastal species is a response to the use of de-icing salt. The most widespread species on Britain's roadsides, Puccinellia distans, occurs in the north and east of England and Wales. This distribution is due to the varying use and effects of de-icing salt which are related in turn to regional differences in climate and traffic density. On roadsides, seed dispersal is greater in the direction of traffic flow and the smaller seeds of Puccinellia distans are carried further than the larger seeds of Plantago maritima. Species on roadsides occur in distinct zones with the coastal species confined to the saline road margin. The causes of this zonation were investigated by examining seedling establishment in experimental plots. Seedlings were only able to establish in grass plots when the salinity was sufficiently high to kill the competing glycophytic grasses. On bare soil, the halophytes established and grew satisfactorily when salt was added but grew very poorly in the absence of salt. After two years Plantago maritima overcame this apparent requirement for salt on bare soil but Puccinellia distans and Spergularia marina did not.Acknowledgements: N. E. Scott was in receipt of a N.E.R.C. Studentship. The authors wish to thank the members of the B.S.B.I. and the Biological Records Office for information on species distribution.     

Patterns of seagrass macrobenthic biodiversity in the warm-temperate Knysna estuarine bay,Western Cape: a review

Aquatic Ecology - Knysna estuarine bay in South Africa's Garden Route National Park is that country's most significant estuarine system for biodiversity and conservation value. One...     

Distribution of sawfishes (Pristidae) in the Queensland Gulf of Carpentaria,Australia, with notes on sawfish ecology

Synopsis Pristis microdon, P. zijsron, P. clavata and Anoxypristis cuspidata are distributed throughout the Queensland section of the Gulf of Carpentaria, Australia. In a survey of the four species, Anoxypristis cuspidata was the most abundant and was recorded in both the inshore and offshore set net fisheries. The size distribution and catch locations of A. cuspidata suggest that the inshore area to a depth of 10 m may be the preferred habitat for juveniles of this species, while adults primarily occur offshore. Pristis microdon, P. zijsron and P. clavata were recorded only in the inshore fishery with catches dominated by immature animals. Pristis microdon was caught in the inshore fishery late in the monsoonal wet season (February to April) and inhabited both freshwater and estuarine environments. Pristis zijsron occurred only on the sand and mud flats outside river mouths whilst P. clavata inhabited both the sand and mud flats and upstream estuarine habitats. Observations on reproductive staging and the capture of neonate specimens suggest that in all four pristids, pupping occurred through the wet season until the beginning of the dry season in May. A seasonal set net closure for the barramundi, Lates calcarifer and shark fisheries, which has been in place since 1980 in Queensland Gulf waters, therefore offers a measure of protection to breeding female sawfish and their offspring.     

Posidonia australis seed predation in seagrass habitats of Two Peoples Bay,Western Australia

Posidonia australis seed predation experiments conducted in three seagrass habitats (P. australis, Posidonia sinuosa, Halophila ovalis) and bare sand in Two Peoples Bay, Western Australia, showed higher predation rates in seagrass than bare sand, supporting general conclusions from two previous predation studies in Western Australia. However, much higher rates were noted in H. ovalis, compared to previous observations of very low rates in H. ovalis on Rottnest Island, Western Australia. We attribute these differences to gammaridean amphipods (family Lysianassidae) that were present in a detrital layer within the H. ovalis in Two Peoples Bay. Our data from Two Peoples Bay continues to add to the growing body of information showing high seed predation rates in most seagrass habitats by a diverse group of crustacean species.     

The comparative ecology of ten species of honeyeaters in South Australia

We describe the habitats and feeding sites used by ten species of honeyeaters in the Mount Lofty Ranges near Adelaide, South Australia.Five of the species have relatively short beaks and feed chiefly on insects gleaned from leaves and bark or captured in the air. They also visit the flowers of Eucalyptus and occasionally of other plants. Species in the same genus occupy different habitats. The five longer-beaked species feed more often onflowers of a wider variety including Eucalyptus, tubular flowers of the heaths and the inflorescences of bottle-brushes. They also feed on insects, most of which they capture in the air. Most of these species overlap broadly in habitat and thus form a guild of species which are very similar in their overall ecology.     

Notes on the ecology and distribution of non-marine ostracods in Australia

The knowledge of the ecology and distribution of ostracods from inland waters in Australia is reviewed. The large diversity of the athalassic saline fauna is discussed in detail and species diversity in different areas is analysed; salinity tolerance of the halobiont species is also presented. In addition discussion deals with hatching, permanent versus ephemeral water fauna, mode of locomotion, large size of some species, variation in size and ornamentation of shell. A brief characterization is attempted of the ostracods and the type of habitats in which they live. Finally, the distribution, species diversity in different areas and the endemicity of the fauna are outlined and a comparison of this fauna is made with that of other parts of the world.     

Some notes on the cytotaxonomy of two Ruppia species in South Australia

Chromosome counts were made from root tip cells of Ruppia megacarpa Mason (2n = 20 chromosomes) and of Ruppia tuberosa Davis and Tomlinson (2n = 20 and 3n = 30 chromosomes). The plants were collected in South Australia from coastal lakes, lagoons and the sea. The salinity in these waters varied from 6.9 to 67.9% total dissolved solids (TDS). We report the occurrence of Ruppia tuberosa in the tidal zone of the sea, and the occurrence of a triploid population of this species in a lagoon.     

The role of hoplonemerteans in the ecology of seagrass communities

Seagrasses of the world harbor a rich and varied fauna, but a review of the literature revealed that little has been done to evaluate the ecological importance of nemerteans in such communities. Monostiliferous hoplonemerteans are common inhabitants of some seagrasses, e.g. eelgrass (Zostera), but generally they are seldom collected or identified or are apparently absent in other species such as schoalgrass (Halodule) or turtlegrass (Thalassia). Nineteen species of hoplonemerteans (four families) have been identified from eelgrass beds around the world; they exist mainly as epifauna, and all except two species are probably suctorial feeders. Some palaeonemerteans (2 species) and heteronemerteans (4 species) are also associated with eelgrass, but mainly as infauna. Suctorial nemerteans (4 species in 3 families) from eelgrass beds located along the mid-Atlantic coast of the United States feed in the laboratory on a variety of amphipod species that inhabit eelgrass. Tubicolous species (e.g. Corophium) seem to be preferred. Zygonemertes virescens feeds on nine species of amphipods belonging to six families, and is the only species to feed on isopods (3 species). Analyses of field studies on the occurrence of hoplonemerteans in eelgrass beds in Virginia and New Jersey, along with available information on the food habits of these worms, were used as a basis for demonstrating their potential importance as predators of peracarids in seagrass systems. More careful methods for collecting and identifying worms, continued studies on food preferences and rates of predation, and emphasis on the population dynamics of worms and prey, are recommended in order to evaluate the role of suctorial hoplonemerteans in the ecology of seagrasses.     

Nitrogen and phosphorus uptake in seedlings of the seagrass Amphibolis antarctica in Western Australia

The uptake of nitrate, ammonium and phosphate was examined in vitro in seedlings of the seagrass Amphibolis antarctica ((Labill.) Sonder ex Aschers.). Uptake of all three nutrients was significantly correlated with external concentration up to 800 µ g l^–1. The uptake of nitrate (0–200 µ g NO₃-N g dry wt^–1 h^–1) was significantly lower than the uptake of ammonium (0–500 µ g NH₄-N g dry wt^–1 h^–1), suggesting that the seedlings have a higher affinity for this form of nitrogen in the water column.Data were in general agreement with uptake rates recorded for other seagrasses, notably Zostera marina. In comparison to the dominant macroalgae for the same region, seedlings had either similar or higher uptake rates in relation to external concentration, lending support to the hypothesis that seedlings, which do not possess roots, behave like macroalgae in terms of nutrient acquisition from the water column.A comparison with literature data on adult seagrass suggests, however, that seagrasses show lower uptake rates than macroalgae suggesting that the macroalgae, which are totally reliant on the water column for nutrients, are more efficient at uptake than seagrasses which may potentially use the sediment for a nutrient source.     

The taxonomy of some British Littorina species, with notes on their reproduction (Mollusca: Prosobranchia)

The rough periwinkle Littorina saxatilis is considered, in current literature, to consist of various sympatric "subspecies" and "varieties". These, it has been suggested, are incipient species and are evidence for sympatric speciation.
This paper shows that in Wales the "saxatilis" aggregate consists of four separate, fully sympatric species: L. rudis, patula, nigrolineata and neglecta . Differences between these species include proportions, sculpture and size of the shell, range of colour patterns, the anatomy of the genitalia, and isozyme patterns. The possible evidence for incipient species is discussed and rejected.
The diversity of penis form amongst the British winkles is remarkable, and it is suggested that in these sympatric species the structure of the penis could be of importance in species recognition.
The four species occupy different zones on the shore and three certainly differ also in their methods of reproduction: L. rudis is ovoviviparous and contains embryos throughout the year, patula is ovoviviparous but contains embryos only in winter, nigrolineata is oviparous. The reproduction and dispersal methods of all British winkles are reviewed. The evidence available supports the view that non-planktonic dispersal is an adaptation which, in species whose shell colour varies considerably from one locality to another, enables each population to become adapted to its local environmental conditions. Ovoviviparity occurs in high-shore non-planktonic species, and may be an adaptation to avoid the dangers of egg desiccation. Planktonic dispersal is found in species whose shell colour does not vary as much as in non-planktonic ones. In these species, it is argued that a common planktonic pool enables a rapid re-colonization in the case of local decrease in population numbers, and also the rapid dispersal of successful mutations.     

海草生态学研究进展

海草床生态系统是生物圈中最具生产力的水生生态系统之一,具有重要的生态系统服务功能。作者根据海草生态学及相关领域的最新研究进展,对世界范围内海草床的空间分布、海草床的生态系统服务功能以及外界因素对海草床的影响等研究进展进行了综述。海草床生态系统服务功能主要包括净化水质、护堤减灾、提供栖息地和生态系统营养循环等。对海草床影响较大的外界环境因素包括盐度、温度、营养盐、光照、其他动物摄食、人类活动和气候变化等。海草普查、海草生态功能研究,影响海草床的主要环境因素,海草修复研究等将是我国海草研究的主要方向。