STORRE Collection: Electronic theses of Biological and Environmental Sciences students
http://hdl.handle.net/1893/29
Electronic theses of Biological and Environmental Sciences students2024-03-29T13:10:26ZAssessing the photo-physiology of cyanobacteria using active fluorescence
http://hdl.handle.net/1893/35533
Title: Assessing the photo-physiology of cyanobacteria using active fluorescence
Author(s): Courtecuisse, Emilie
Abstract: Eutrophication and the impacts of climate change are responsible for the increased occurrence of harmful algae blooms. In lakes and reservoirs, cyanobacteria blooms pose particular risk to ecosystems, humans and animals due to the occurrence of toxin-producing species. Several methods exist to monitor cyanobacteria, which vary in cost, time and accuracy. Fluorescence methods developed to monitor cyanobacterial abundance already give rapid, robust and reproducible results. Discrimination between cyanobacteria and algae in fluorescence methods is based on their photosynthetic pigment content, but due to overlapping pigment absorption signatures, the interpretation of fluorescence signals is consequently not straightforward. In this thesis, a range of fluorescence markers were tested on the ability to assess and predict cyanobacteria physiology and growth.
Hyperspectral laboratory experiments with algal and cyanobacteria cultures revealed that excitation wavebands centred on 445 nm and 615 nm, and emission wavebands at 660, 685 and 730 nm allow the best differentiation between cyanobacteria and algae. Broadband actinic light should be preferred to assess the relation between ambient light and photosynthesis. Based on these results, a new multispectral active fluorometer (LabSTAF) was tested to assess the physiology and growth of cyanobacteria in reservoirs exhibiting annual blooms. Fluorescence light curves obtained with a green-orange-red (GOR) and a blue (B) excitation protocol were found to follow cyanobacteria and algae physiology, respectively. The fluorescence emission ratio of photosystem I over II was also significantly correlated with the relative abundance of cyanobacteria. Excitation spectra further distinguish the presence of distinct pigment groups. Finally, the ability of the LabSTAF to determine cyanobacteria growth from photosynthetic parameters was demonstrated on natural samples brought into nutrient replete conditions. ETR (electron transport rate) and Pmax (maximum specific photosynthetic rate) were found to predict phytoplankton growth by up to 3-4 days, with excitation protocols GOR and B indicating the dominant phytoplankton group.2023-04-01T00:00:00ZThere are no longer plenty more fish in the sea The potential of wrack macro-invertebrates as an alternative source of the marine origin omega-3 fatty acids: EPA and DHA
http://hdl.handle.net/1893/35532
Title: There are no longer plenty more fish in the sea The potential of wrack macro-invertebrates as an alternative source of the marine origin omega-3 fatty acids: EPA and DHA
Author(s): Richardson, Finlay Bryson
Abstract: Increasing population and affluence puts expanding pressure on global food security. Sustainably meeting future food demand requires novel and innovative food production techniques and technologies that are more efficient than those used today. Furthermore, the disconnect between the diets of people today and the diets for which we were naturally selected has numerous negative health effects. As such, future food must also be of high quality. This is particularly true of our omega-3 consumption relative to our omega-6. However, over recent years, rather than improving, the quantity of omega-3 in farmed fish produce, which is the most significant source of dietary omega-3 globally, has decreased. This is a result of overfishing reducing fish oil supply, creating a lower omega-3 content in the food of these farmed fish. Thus, finding an alternative omega-3 source that is more environmentally sustainable than fish oil is a top priority. This alternative must also be economically attractive and come with social benefits as the comprehensive adoption of any alternative relies on it improving the sustainability of all three of these pillars of society. Insects show much promise as a sustainable source of protein in food and feed and preliminary studies have identified wrack macro-invertebrates as having similar potential as a fish oil replacement. This research assesses the potential of this alternative by investigating the ease with which they could be cultured and their nutritional composition before crudely estimating their production cost and market value following this. The results suggest the biggest barrier to the use of wrack macro-invertebrates as a fish oil replacement is the inherent value of the seaweed substrate which prevents this from being economically viable. Furthermore, even if it were, higher returns of omega-3 would be obtained from the use of the seaweed as a feed ingredient directly.2023-05-01T00:00:00ZCauses and consequences of sexual dimorphism in mandrill (Mandrillus sphinx) feeding and spatial behavior
http://hdl.handle.net/1893/35518
Title: Causes and consequences of sexual dimorphism in mandrill (Mandrillus sphinx) feeding and spatial behavior
Author(s): Bauld, Joshua
Abstract: Sexual dimorphism is a widespread phenomenon, the origins of which have long intrigued evolutionary ecologists. Classic evolutionary theory attributes the evolution of sexual dimorphism to sexual and fecundity selection, that arise due to sex differences in optimal reproductive strategy. However, cross-species comparative analyses have found mixed support for sexual and fecundity selection as drivers of dimorphism. Other hypotheses may therefore be required to explain the full diversity of sexual dimorphisms found in nature.
One alternative is the evolution of sexual dimorphism via ecological causation. This thesis explores the possibility of ecological causation of sexual dimorphism, with a particular focus on mandrills (Mandrillus sphinx). Mandrills are the most sexually dimorphic primate, with males over three times larger than females, possessing 45 mm canines and displaying extravagant red, blue, and violet ornamentation on their faces and rumps. Males also abandon social groups outside of the breeding season, foraging and travelling separately to females, which could suggest an ecological component to mandrill dimorphism.
One of the key predictions of the ecological causation hypothesis is that greater sexual dimorphism should be associated with greater ecological divergence between males and females. In Chapter 2, I conducted a meta-analysis of 163 species to examine associations between sexual dimorphism and ecological sex differences, measured using stable isotopes. Across species, greater size dimorphism was associated with greater sex differences in trophic level. Chapter 2 thus supports a key prediction of the ecological causation hypothesis and suggests that the strength of relationships between sexual dimorphism and ecology may be underappreciated.
Mandrills are challenging to study in the wild, due to the dense forests in which they are found. I therefore applied research tools that avoided the need to directly observe individuals, to study the socioecology of males and females and investigate the possibility of ecological causation of mandrill dimorphism. In Chapter 3, I analyze the contents of 4024 mandrill fecal samples, collected over an eight-year period, in conjunction with eight years of fruiting phenology data. I find that mandrills are primarily frugivorous, with consumption of fruit tracking phenological patterns of fruit production. The focal group also demonstrated high dietary flexibility, consuming animal prey, leaves, crushed seeds, and other plant fibers when fruit availability was low.
However, because male mandrills spend much of year solitary, the feeding niche information gained from Chapter 3 largely relates to females. To investigate sex differences in feeding niche, I therefore applied stable isotope analysis to mandrill hairs. In Chapter 4, I detail the results of a diet-switch experiment, that quantified mandrill hair growth rates, isotopic tissue turnover times and isotopic tissue-diet discrimination factors. This experiment showed that stable isotope analysis of mandrill hairs can reveal dietary information on wild mandrills at a temporal resolution of 5.5 days and allowed the stable isotope ratios of wild mandrills to be correctly adjusted for accurate dietary inference.
In Chapter 5 I applied stable isotope analysis to the hairs of wild male and female mandrills. I found that the diets of individual male mandrills were more consistent than individual females, who instead showed more dietary variation, at the individual level. This result suggests that individual male mandrills had more consistent access to preferred resources than individual females, and therefore that males experience differing levels, or outcomes, of resource competition. Males may therefore seasonally leave mandrill social groups to avoid resource competition.
In Chapter 6, I used GPS collars to examine sex differences in mandrill spatial behavior. I found that, during the breeding season, male habitat selection, home-range size and Brownian motion variance was similar to females, but distinct from females during the non-breeding season. These results indicate that collared males were not always within the social group during the non-breeding season. Furthermore, during the non-breeding season, males travelled shorter distances, at slower speeds, compared to the breeding season. Males therefore appeared to expend less energy on travel during the non-breeding season, suggesting that male mandrills may also leave groups to reduce energetic expenditure.
The results of Chapters 5 and 6 suggest that ecological factors compel male mandrills to abandon social groups outside of the breeding season. However, the intensity of sexual selection on male traits may be increased as a result of this behavior, as males must establish dominance and attract unfamiliar females when they re-join social groups to breed. An interaction between sexual and ecologically mediated selection may therefore offer the most complete explanation of why mandrill dimorphism is so extreme.2023-01-01T00:00:00ZAgent-based modelling to improve management strategy evaluation in complex problems of biodiversity conservation
http://hdl.handle.net/1893/35512
Title: Agent-based modelling to improve management strategy evaluation in complex problems of biodiversity conservation
Author(s): Bach, Adrian
Abstract: Amid the Earth’s 6th mass extinction, conservation of the remaining biodiversity is more urgent than ever. But conservation faces the many challenges associated with the management of ecosystems, including the different sources of uncertainty around their joint social and ecological dynamics. Moreover, mismanagement can have detrimental consequences for both conservation and people’s livelihood. To help managers design efficient and equitable policies in such complex situations, the use of simulation models as virtual laboratories to evaluate management scenarios have become widespread. Yet, most of these models are mathematical models, which can be limited in conservation problems. Indeed, the latter are rather small-scale, often spatially explicit, and unexpected responses often stem from local interactions between the parts of the system. These features are key assets of agent-based modelling (ABM), which should therefore be more appropriate but is still scarcely applied in management strategy evaluation. In this thesis, I further develop the use of ABM in conservation by designing agent-based tools to evaluate alternative management strategies in two complex conservation problems: the management of conservation conflicts between species protection and agriculture, and the management of species endangered by apparent competition.
First, I address the timing of management intervention in a conservation conflict between a manager aiming to conserve an animal population and farmers aiming to maximize yield by protecting their crop from consumption by the animal population. Building upon the agent-based software GMSE, which simulates the budget-constrained adaptive management of conservation conflicts, I propose a novel management strategy that dynamically alternates between intervention and waiting based on the monitoring of the distance between the population density and manager’s target. The evaluation shows that my strategy can produce at least as efficient and equitable results as unconditional intervention while allowing critical budget savings. This strategy is now available in the GMSE package to be evaluated in other cases of conservation conflicts and my method proposes a way to do so in a more equitable way.
Then, I introduce an ABM of trophic interactions between several species in several trophic layers in which apparent competition can emerge. I validate it in its essential version according to the ABM framework and discuss its adequacy with apparent competition theory. Overall, my model behaves as theory and empirical cases predict, with some interesting contradictions challenging predictions of previous mathematical models. The model is now fit for the addition of more complex features needing further understanding in apparent competition theory and conservation.
Finally, I demonstrate how my model can be used to evaluate removal strategies to conserve a prey species endangered by apparent competition with an alternate prey species mediated by a shared predator. Predator removal only, alternate prey removal only, and simultaneous removal of the predator and alternate prey all successfully prevented the extinction of the endangered population, but the simultaneous removal strategy was the most efficient in conserving the endangered population while also ensuring more stable dynamics and higher densities of the other species. Any combinations of these removal strategies are now available in my model for evaluation by researchers or managers in other cases, and my method proposes to conserve the endangered population while also ensuring the persistence of the other species in the system.
Across these chapters, I demonstrate how the agent-based approach can efficiently integrate the complexity of conservation problems to produce informative tools for biodiversity management strategy evaluation. Notably through human individual decision-making, complex individual behaviour, and spatially explicit modelling along with the simulation of different sources of uncertainty. I have shown, with general examples, how to use the modelling tools I provide, with methods enlarging the scope of conservation objectives: a better consideration of the equity of management measures between conservation and land-users’ livelihood in conservation conflicts, and a better inclusion of management consequences on other species in interaction with the population of conservation interest. Through my models’ development and validation, I have questioned and enhanced theory of conservation conflicts' adaptive management and and of apparent competition’s underlying mechanisms and management.2023-03-31T00:00:00Z