Assemblages of algae are altered by both bottom - up ( e.g. nutrient availability ) and top - down ( e.g. herbivory ) processes. As a result of the increasing human population in coastal areas, massive changes are forecast to benthic habitats in response to increasing coastal nutrient concentrations and a reduction in consumers. To identify the scales over which nutrients may have an effect, abundance of turf - forming algae growing as epiphytes on kelp ( Ecklonia radiata ) were related to water nutrient concentration across temperate Australia. In general, the percentage cover of epiphytes was greatest at sites with the greatest nutrient concentrations. By experimentally elevating mean nitrate concentration from the low 0.064 ± 0.01 µmol L [superscript - 1 ] to 0.121 ± 0.04 µmol L [superscript - 1 ], which was still only ~ 5 % of that measured on a more eutrophic coast, I was able to increase the percentage cover of epiphytes to match those seen on nutrient rich coasts, despite not matching the nutrient concentrations on those coasts. Hence, it appears that the effects of elevated nutrients will be disproportionately large on relatively oligotrophic coasts. Nutrient concentrations were also experimentally elevated to test whether the presence of an algal canopy or molluscan grazers were able to counter the effects of nutrient enrichment on algal assemblages. The loss of canopy - forming algae is likely to be a key precursor to nutrient driven changes of benthic habitats, because nutrients had no direct effect on algal assemblages in the presence of canopy - forming algae. In the absence of canopy - forming algae, space was quickly monopolised by turf - forming algae, but in the presence of elevated nutrients grazers were able to reduce the monopoly of turf - forming algae in favour of foliose algae. This switch in relative abundance of habitat may reflect greater consumption of nutrient rich turf - forming algae by grazers, possibly creating more space for other algae to colonise. Importantly, greater consumption of turf - forming algae in the presence of elevated nutrients may act as a mechanism to absorb the disproportionate effect of nutrients on oligotrophic coasts. In southern Australia, canopy - forming algae have a negative impact on the abundance of turf - forming algae. To assess the mechanisms by which an algal canopy may suppress turf - forming algae, abrasion by the canopy and water flow were experimentally reduced. Abrasion by the canopy reduced the percentage cover and biomass of turf - forming algae. In contrast to predictions, biomass and percentage cover of turf - forming algae were also reduced when water flow was reduced. Light intensity was substantially reduced when there was less water flow ( because of reduced movement in algal canopy ). However, the reduction in available light ( shading ) did not account for all of the observed reduction in biomass and percentage cover of turf - forming algae, suggesting that other factors are modified by water flow and may contribute to the loss of turf - forming algae. Habitat loss and fragmentation are well known to affect the diversity and abundance of fauna in habitat patches. I used experimental habitats to assess how fragmentation of turf habitats affects the diversity and abundance of two taxa of macroinvertebrates with different dispersal abilities. I established that increased isolation of habitats reduced the species richness and abundance of invertebrates with slow rates of dispersal, while the species richness and abundance of invertebrates with fast rates of dispersal were greatest in habitats that were far apart. In summary, this thesis provides an insight into some of the impacts associated with human populations in coastal areas, namely increased nutrient inputs, loss of grazers ( e.g. harvesting ), and loss of canopy algae and fragmentation of habitats. I show that increased nutrient concentrations in coastal waters can alter the relative abundance of algal species, and that some effects of elevated nutrients can be absorbed by the presence of grazers. I also show that elevated nutrients have no effect on algal assemblage in the presence of canopy - forming algae, and that canopies can suppress the colonisation of turf - forming algae. Finally, I show that the fragmentation of turf habitats affects taxa of invertebrates with different dispersal abilities in different ways. Whilst the contemporary ecology of much of the temperate Australian subtidal coast is considered to be relatively unaffected by human activity, this thesis shows that changes to top - down and bottom - up processes could have large consequences for habitats and their inhabitants. / Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2005.

"March 2004" / Bibliography: leaves 115-141. / 141. [8] leaves : ill., maps, photos (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Localised disturbance can generate considerable patchiness in the structure and composition of subtidal habitats which is a key determinant of differences in the diversity of associated assemblages of invertebrates. / Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004

<p>Industrial and domestic sewage effluents have been found to cause reproductive disorders in wild fish, often as a result of the interference of compounds in the effluents with the endocrine system. This thesis describes laboratory-based exposure experiments and a field survey that were conducted with juveniles of the three-spined stickleback, <i>Gasterosteus aculeatus</i>. This small teleost is a common fish in Swedish coastal waters and was chosen as an alternative to non-native test species commonly used in endocrine disruption studies, which allows the comparison of field data with results from laboratory experiments.</p><p>The aim of this thesis was to elucidate 1) if genetic sex determination and differentiation can be disturbed by natural and synthetic steroid hormones and 2) whether this provides an endpoint for the detection of endocrine disruption, 3) to evaluate the applicability of specific estrogen- and androgen-inducible marker proteins in juvenile three-spined sticklebacks, 4) to investigate whether estrogenic and/or androgenic endocrine disrupting activity can be detected in effluents from Swedish pulp mills and domestic sewage treatment plants and 5) whether such activity can be detected in coastal waters receiving these effluents.</p><p>Laboratory exposure experiments found juvenile three-spined sticklebacks to be sensitive to water-borne estrogenic and androgenic steroid substances. Intersex – the co-occurrence of ovarian and testicular tissue in gonads – was induced by 17β-estradiol (E2), 17α-ethinylestradiol (EE2), 17α-methyltestosterone (MT) and 5α-dihydrotestosterone (DHT). The first two weeks after hatching was the phase of highest sensitivity. MT was ambivalent by simultaneously eliciting masculinizing and feminizing effects. When applying a DNA-based method for genetic sex identification, it was found that application of MT only during the first two weeks after hatching caused total and apparently irreversible development of testis in genetic females. E2 caused gonad type reversal from male to female. E2 and EE2 induced vitellogenin - the estrogen-responsive yolk precursor protein, while DHT and MT induced spiggin – the androgen-responsive glue protein of the stickleback.</p><p>None of the effluents from two pulp mills and two domestic sewage treatment plants had any estrogenic or androgenic activity. Juvenile three-spined sticklebacks were collected during four subsequent summers at the Swedish Baltic Sea coast in recipients of effluents from pulp mills and a domestic sewage treatment plant as well as remote reference sites. No sings of endocrine disruption were observed at any site, when studying gonad development or marker proteins, except for a deviation of sex ratios at a reference site.</p><p>The three-spined stickleback – with focus on the juvenile stage – was found to be a sensitive species suitable for the study of estrogenic and androgenic endocrine disruption.</p>

<p>The focus of this thesis is the early detection of stress in the environment. It has been proposed that studies on the cellular level would detect stress reactions earlier in time compared to common physiological methods. In a series of experiments we investigated how different stress factors, both natural and introduced by man, affect levels of stress proteins. One- and two-dimensional gels were used to determine individual proteins and families of proteins. The two-dimensional gels were also used in a proteomic approach, were the presence and absence of proteins after treatment was observed, and the protein expression signatures (PES) were identified. </p><p>Baltic <i>Mytilus edulis</i> was used in all experiments and it is evident that earlier observed differences in physiological rates and pollution sensitivity, compared to marine mussels, is also manifested as lower concentrations of stress proteins after exposure to copper and cadmium. When the Baltic mussels were allowed to acclimate for one month the difference decreased, suggesting an environmentally induced difference (paper I). Pre-exposure to heat before exposure to either a second heat-shock or cadmium was found to enhance the levels of HSP70 and thus tolerance, significantly (paper II). Exposure to a mixture of stress factors (PCB, copper and lowered salinity) revealed synergistic, additive and antagonistic effects in induction of 6 different stress proteins. When analyzing a large number of proteins it was shown that it is possible to identify PES with this technique, and we hypothesize that it could be possible to separate responses to mixtures of stress factors (Papers III and IV). Different techniques were also applied to analyze the protein expression pattern when mussels were exposed to PAH- and PCB-fractions extracted from Baltic Sea sediments. In this experiment the protein assays were accompanied by physiological measurements. All methods indicated stressed conditions, but the variation between individual mussels within treatments was smaller in terms of protein response than for physiological parameters (paper V). It is concluded that measuring the induction of stress proteins is a reliable way to detect stressful conditions. Proteins visualized on a one dimensional gel give a “gross” picture of an organism’s condition. The major challenge is to identify the origin and severity of the elucidated stress response. Further mapping of two-dimensional gels suggested that protein patterns are specific to type and level of stress. </p><p>A most important future step is to establish links between sub-cellular protein response to well known physiological effects. This should include long term experiments where altered protein expression signatures are linked to life history characteristics like survival, growth and reproductive success.</p>

<p>In the green-veined white butterfly (<i>Pieris napi</i>), females obtain direct fitness benefits from mating multiply and studies have shown that fitness increases seemingly monotonically with number of matings. The reason is that at mating males transfer a large nutritious gift (a so called nuptial gift) to the females that the females use to increase both their fecundity and lifespan. In addition, if exposed to poor food conditions as larvae, females mature at a smaller size compared to males. Accordingly, it was suggested that smaller females could compensate for their size through nuptial feeding by, for instance, mating more frequently. We did not find any support for that hypothesis. On the contrary, larger females remated sooner and had a higher lifetime number of matings. Neither were smaller females able to compensate in any other way, because singly mated females and multiply mated females suffered to the same extent from their smaller size. This thesis also shows that despite the positive relationship between fitness and number of matings, there is a large variation in female mating frequency in wild populations and about every second female mates only once or twice. This variation is not dependent on how often females get courted by males, because female mating frequency was shown not to be affected by male courtship intensity. Hence, the reason for the low mating frequency could either be that males have evolved the ability to manipulate females to mate at a suboptimal rate as a measure of protection against sperm competition, or alternatively, that female mating rate is suppressed by some costs. Using two selection lines, artificially selected for either a high or a low mating rate, we showed that the variation in mating rate was mainly a female trait because which line the females were from affected their mating rate whereas which line the male was from did not. This implies that females mate at a low rate due to hidden costs or due to constraints. The same study also showed that females with a high "intrinsic" mating rate lived shorter, but only when denied remating. This led us to test the hypothesis that the cost females face is to have the ability to mate at a high rate but the cost is only paid when remating opportunities are scarce. However, we found no support for such an idea, because females with a high intrinsic mating rate held in a cold environment where the butterflies were prevented from flying and feeding did not live shorter. Neither was there an effect of a female’s mating rate on her ability to quickly break down and convert male nutrient gifts into egg material. Female mating rate did, on the other hand, affect dispersal tendency, with low mating rate females being more inclined to fly between different habitats. The underlying reason for this is still to be explored.</p>

<p>Much of current ecological theory stems from experimental studies. These studies have often been conducted in closed systems, at spatial scales that are much smaller than the systems of interest. It is known that the outcome of these experiments may be seriously affected by artefacts associated with the caging procedures, as well as by the actual difference in spatial scale between experimental and target system. Yet, quantitative methods for estimating and removing artefacts of enclosure and for extrapolating experimental results to the scales of natural systems are largely lacking.</p><p>The aim of this thesis was to confront some of the problems encountered when scaling from experiments to nature in studies on predator-prey systems, with focus on effects of changes in spatial heterogeneity. Specifically, I examined mechanisms that may cause consumption rate estimates to depend on the size of the experimental arena. I also studied methods for scaling up these process rate estimates to natural predator-prey systems. The studies were performed on invertebrate predator-prey systems found in the northern Baltic Sea. Initially, a descriptive study of small-scale distribution patterns was performed, in order to get background information on how the behaviour of the organisms was manifested in the spatial structure of the community. Experimental studies of two predator-prey systems exposed an artefact that may be widespread in experiments aiming at quantifying biotic interactions. It is caused by predator and prey aggregating along the walls of the experimental containers. This behaviour affects the encounter rate between predator and prey, thereby causing consumption rates to be scale-dependent. Opposing the common belief that larger arenas always produce less biased results, this scale effect may instead be reduced by decreasing arena size. An alternative method for estimating the magnitude of, and subsequently removing, the artefact caused by aggregation along the arena wall was presented.</p><p>Once unbiased estimates of process functions have been derived, the next step is to scale up the functions to natural systems. This extrapolation entails a considerable increase in spatial heterogeneity, which may have important implications for the dynamics of the system. Moment approximation provides a method of taking the heterogeneity of natural populations into account in the extrapolation process. In the last study of the thesis, the concepts of moment approximation and how to estimate relevant heterogeneity were explained, and it was shown how the method may be used for adding space as a component to a dynamic predator-prey model. It was concluded that moment approximation provides a simple and useful technique for dealing with effects of spatial variation, and that a major benefit of the method is that it provides a way of visualising how heterogeneity affects ecological processes.</p>

<p>The objective of this study was to increase understanding of the processes structuring and controlling the species richness of riparian plant communities. In particular, I examined the unimodal relationship, found in many rivers, between plant species richness and location along the river corridor. The most important finding was that this pattern is dynamic and varies with time, most likely in response to large-scale flood disturbances. I also found that the sensitivity to flood disturbance varied with the environmental setting of the riparian reaches. Turbulent sections of the river retained high species richness, whereas tranquil reaches had significantly lower species richness in years following high and prolonged flooding, compared to a period without extreme flood events. Riparian soils along turbulent reaches are more resistant to oxygen depletion during floods, a factor which is likely to contribute to the maintenance of species richness. </p><p>The finding that the species richness pattern varied with time led me to ask which factors control plant diversity along riparian zones. I addressed this question by formulating three contrasting, although not mutually exclusive, hypotheses: (1) longitudinal patterns in riparian plant species richness are governed by local, river-related processes independent of the regional species richness, (2) riparian plant species richness is controlled by dispersal along the river, i.e., longitudinal control, and (3) the variation in riparian plant species richness mirrors variation in regional richness, i.e., lateral control. I found indications of all three types of control, although local factors seemed to fit most of the criteria. Riparian species richness was not significantly correlated to species richness in the surrounding upland valley. It was however significantly negatively correlated to soil pH, a local habitat factor of the reach. The fact that the species richness pattern varied in time, corresponding to the presence or absence of extreme flood events suggest that it is influenced by local disturbance regimes. The potential for control by longitudinal dispersal was found to be highest in the middle reaches of a river. Here, the similarity between upland and riparian vegetation was lowest, and invasibility (germination ability) was highest. Earlier work has shown that regulated rivers have an inverted species richness pattern compared to free-flowing rivers, with lowest species richness in the middle reaches. One potential mechanism behind this could be varying susceptibility to disturbance along the river. I tested this by experimentally disturbing the vegetation, applying the same level of disturbance along an entire free-flowing river. However, the response to experimental disturbance did not vary with location, likely because of a major flood disturbance preceding the experiment.</p>

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