Wiley

Estimates of leaf damage by insect herbivores are presented for 25 species of mangrove plants, comprising canopy and understorey species. Leaf area loss was highly variable among the species sampled, with means ranging from 0.3 to 35.0% of expanded leaf area. There was also great variability amongst leaves within species, and the mean coefficient of variation for leaf loss from the 25 species was 266%. Of the 12 species sampled at more than one site in North Queensland, eight exhibited small, but significant, between‐site differences in herbivory. In general, it did not appear that height in the canopy influenced herbivory. For the dominant mangrove forest community type at Missionary Bay, an estimated mean of 2.1% of leaf production, or 11 g m^‐2 per year, entered the direct grazing pathway. This very low figure is compared with estimates from other studies on mangrove forests and estimates from a variety of Australian terrestrial forests.

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.

An essential pilot study was designed to quantify observer heterogeneity and to compare observation methods for the detectability of forest birds in stands of Eucalyptus and Pinus radiata forest as a basis for a major research project on habitat fragmentation near Tumut, southern New South Wales. Twelve experienced observers participated in the investigation. Point interval counts, zig‐zag walks and strip transects were used to count birds in both eucalypt and pine forests. The 65 species of birds recorded in the study were assigned to one of nine groups classified by a set of attributes that characterized bird detection by field observers (e.g. body size, colour and calling patterns). Observer heterogeneity varied between groups of birds and was most apparent for small birds foraging in low shrubs (species such as the white‐browed scrub wren, assigned to group 2), frequent calling, active birds (species such as the golden whistler, assigned to group 7), and midstorey, undercanopy foragers with distinctive behaviour (species such as the grey fantail assigned to group 4). For bird groups 2, 4 and 7, additional variability due to observer differences resulted in an average increase of ~ 40% in the width of a 95% confidence interval for the logarithm of bird abundance generated from a 20 minute count. Our analysis shows that taking the average of counts obtained by two or more observers would negate the increase in variance of counts due to observer heterogeneity. Few differences between methods of field observation were found. However, for frequent calling, active birds (group 7) there was evidence that more birds were heard using the point interval count method. Our study clearly demonstrated a need to either control for observer differences or to assign at least two observers to individual sites when designing bird surveys for comparative studies. Failure to do so will result in a decrease in precision of bird counts.

This paper reviews the ecology of soft‐sediment macro‐invertebrates and, in particular, evaluates how much progress has been made in the recent literature towards elaborating statistical models of the ecology of these biota and in using quantitative predictions derived from these models. Steps to formulating statistical models on the dynamics of populations and assemblages are discussed. Current models are mostly conceptual (~70% of studies surveyed), falling into 2 main classes: population dynamics (including recruitment, mortality, dispersal and availability of patches) and process‐orientated studies (including the response of individuals to the physical environment, biogenic habitat modification, biological interactions and physical perturbations). Most recent studies were descriptive or on the population dynamics of species and were undertaken mostly at spatial scales of up to 1 km and temporal scales of months. The development of statistical models appears to be impeded by the limited scope of studies, an over‐emphasis on conceptual models (but recognizing an important role for a rigorous experiment framework) and a difficulty in using outcomes from small‐scale processes at the level of individual organisms to predict larger scale outcomes where many interactions contribute to variation in abundances. Currently, few studies undertake field assessments of the defining characteristics of habitats, the dynamics of those habitats and the relative importance of different habitats to individual populations. Much urgent work is required to develop large scale (space: > 1 km; time: > 1 years) statistical models. This is because attention needs to be given to those interactions and processes in the ecological systems that will provide for the greatest reduction in uncertainty in the quantitative predictions derived from these models.

Meiofauna are ubiquitous in estuaries worldwide averaging 10⁶ m⁻². Abundance and species composition are controlled primarily by three physical factors: sediment particle size, temperature and salinity. While meiofauna are integral parts of estuarine food webs, the evidence that they are biologically controlled is equivocal. Top down (predation) control clearly does not regulate meiofaunal assemblages. Meiofauna reproduce so rapidly and are so abundant that predators cannot significantly reduce population size. Food quantity (bottom up control) also does not appear to limit meiofaunal abundance; there is little data on the effect of food quality. In estuarine sediments meiofauna: (i) facilitate biomineralization of organic matter and enhance nutrient regeneration; (ii) serve as food for a variety of higher trophic levels; and (iii) exhibit high sensitivity to anthropogenic inputs, making them excellent sentinels of estuarine pollution. Generally mineralization of organic matter is enhanced and bacterial production stimulated in the presence of meiofauna. Tannins from mangrove detritus in northern Queensland appear to inhibit meiofaunal abundance and therefore the role of meiofauna in breakdown of the leaves. Meiofauna, particularly copepods, are known foods for a variety of predators especially juvenile fish and the meiofaunal copepods are high in the essential fatty acids required by fish. The copepod’s fatty acid composition is like that of the microphytobenthos they eat; bacterial eaters (nematodes?) do not have the essential fatty acids necessary for fish. Most contaminants in estuaries reside in sediments, and meiofauna are intimately associated with sediments over their entire life‐cycle, thus they are increasingly being used as pollution sentinels. Australian estuarine meiofauna research has been concentrated in Queensland, the Hunter River estuarine system in New South Wales, and Victoria’s coastal lagoons. Studies in northern Queensland have primarily concentrated on the role of nematodes in mineralization of organic matter, whereas those from southern Queensland have concentrated on the role of meiofauna as food for fish and as bacterial grazers. The New South Wales studies have concentrated on the Hunter River estuary and on the structure and function of marine nematode communities. In Victoria, several fish have been shown to eat meiofauna. The Australian world of meiofaunal research has hardly been touched; there are innumerable opportunities for meiofaunal studies. In contaminated estuarine sediments reduced trophic coupling between meiofauna and juvenile fish is a basic ecological question of habitat suitability, but also a question with relevance to management of estuarine resources. Because meiofauna have short lifecycles, the effects of a contaminant on the entire life‐history can be assessed within a relatively short time. The use of modern molecular biology techniques to assess genetic diversity of meiofauna in contaminated vs uncontaminated sediments is a promising avenue for future research. Much of the important meiofaunal functions take place in very muddy substrata; thus, it is imperative to retain mudflats in estuaries.

Data on the species compositions and the ages, sizes, reproductive biology, habitats and diets of the main species in the ichthyofaunas of seven estuaries in temperate southwestern Australia have been collated. Twenty‐two species spawn in these estuaries, of which 21 complete their lifecycles in the estuary. The latter group, which includes several species of atherinids and gobies with short lifecycles, make far greater contributions to the total numbers of fish in the shallows of these estuaries than in those of holarctic estuaries, such as the Severn Estuary in the United Kingdom. This is presumably related in part to far less extreme tidal water movements and the maintenance of relatively high salinities during the dry summers, and thus to more favourable conditions for spawning and larval development. However, since estuaries in southwestern Australia have tended to become closed for periods, there would presumably also have been selection pressures in favour of any members of marine species that were able to spawn in an estuary when that estuary became landlocked. Furthermore, the deep saline waters, under the marked haloclines that form in certain regions during heavy freshwater discharge in winter, act as refugia for certain estuarine species. The contributions of estuarine‐spawning species to total fish numbers in the shallows varied markedly from 33 or 34% in two permanently open estuaries to ≥ 95% in an intermittently open estuary, a seasonally closed estuary and a permanently open estuary on the south coast, in which recruitment of the 0 + age class of marine species was poor. The larger estuarine species can live for several years and reach total lengths of ~ 700 mm and some estuarine species move out into deeper waters as they increase in size. Several marine species use southwestern Australian estuaries as nursery areas for protracted periods. However, sudden, marked increases in freshwater discharge in winter and resultant precipitous declines in salinity in the shallows, and in other regions where haloclines are not formed, are frequently accompanied by rapid and pronounced changes in ichthyofaunal composition, partly due to the emigration of certain marine species. In contrast, the ichthyofaunal compositions of macrotidal holarctic estuaries undergo annual, cyclical changes, due largely to the sequential entry of the juveniles of different marine species for short periods. The ichthyofaunal compositions of the narrow entrance channels, wide basins and saline riverine reaches of large, permanently open southwestern Australian estuaries vary, reflecting the marked tendency for some species to be restricted mainly to one or two of these regions. Comparative data indicate that the characteristics determined for ichthyofaunas in southwestern Australian estuaries apply in general to estuaries elsewhere in temperate Australia.

Species of the hypogeous fungus genus. Mesophellia have been shown to form ectomycorrhiza with Eucalyptus diversicolor and improve seedling growth. Since the morphology of these fungi increases their dependence on animal mycophagy for spore dispersal, these results imply a tripartite interrelationship between eucalypts, hypogeous fungi and marsupials which parallels the North American interrelationship between ectomycorrhizal pine, hypogeous fungi and rodents. An understanding of the independent but analogous interrelationships on the two continents has implications for forest management, especially in regard to the effects of forest conversion on other members of the ecosystem.

Abstract In the early 1980s, a strategy for graphical representation of multivariate (multi‐species) abundance data was introduced into marine ecology by, among others, Field, et al. (1982). A decade on, it is instructive to: (i) identify which elements of this often‐quoted strategy have proved most useful in practical assessment of community change resulting from pollution impact; and (ii) ask to what extent evolution of techniques in the intervening years has added self‐consistency and comprehensiveness to the approach. The pivotal concept has proved to be that of a biologically‐relevant definition of similarity of two samples, and its utilization mainly in simple rank form, for example ‘sample A is more similar to sample B than it is to sample C’. Statistical assumptions about the data are thus minimized and the resulting non‐parametric techniques will be of very general applicability. From such a starting point, a unified framework needs to encompass: (i) the display of community patterns through clustering and ordination of samples; (ii) identification of species principally responsible for determining sample groupings; (iii) statistical tests for differences in space and time (multivariate analogues of analysis of variance, based on rank similarities); and (iv) the linking of community differences to patterns in the physical and chemical environment (the latter also dictated by rank similarities between samples). Techniques are described that bring such a framework into place, and areas in which problems remain are identified. Accumulated practical experience with these methods is discussed, in particular applications to marine benthos, and it is concluded that they have much to offer practitioners of environmental impact studies on communities.

The study investigated the relationship between home range and food abundance in a population of the southern brown bandicoot. Isoodon obesulus, in Western Australia. Home range areas were estimated seven times between 1986 and 1988 by live‐trapping, spool‐and‐line devices and fluorescent pigment tracking. The abundance of invertebrate food was measured simultaneously by placing pitfall traps within the home ranges of individual animals, and by sampling invertebrates in topsoil and litter. Home range areas tended to be negatively correlated with food abundance, especially in the autumn and winter of 1986 and 1987.

The influence of food on home range was investigated further in September 1988 by providing eight individual I. obesulus with a supplementary food mixture. Contrary to expectation, the added food caused an increase in home range area, home range overlap and displacement, as well as an influx of new individuals to food stations. In contrast, home range parameters in control (non‐fed) individuals changed little during the experiment.

The shuffling of home ranges due to feeding suggests that the home range system of I. obesulus is relatively flexible, with individuals monitoring and exploiting resources in an opportunistic manner. In contrast to previous studies, we found no evidence that I. obesulus was territorial. We speculate that individuals may be territorial at low population density if resources are defendable and intruder pressure is low, but occupy overlapping ranges if population density is high.