Field data from CO2 vents, a current model of future ocean acidification conditions, show a positive correlation between elevated seawater pCO2 and fleshy macroalgal abundance, as well as a negative correlation between elevated seawater pCO2 and calcareous macroalgal abundance on coral reefs. One underlying physiological mechanism for increases of fleshy macroalgae species in response to greater pCO2 could be an increase in their photosynthesis. Furthermore, inorganic carbon use mechanisms, irradiance and depth may influence species-specific responses to ocean acidification. Therefore, this thesis aimed to discern carbon use strategies and photosynthetic responses to elevated pCO2 of dominant tropical fleshy and calcareous macroalgae. All species studied were able to utilize HCO3 - for photosynthesis. 33% of calcifying macroalgae and 80% of fleshy macroalgae had increased photosynthetic rates in response to lower pH. Thus, future conditions of OA may perpetuate or exacerbate the abundance of fleshy seaweeds at the expense of calcareous species. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Mosses display a number of hallmark life history traits that influence their ecology at the population and community level. The long lived separation of sexes observed in the haploid gametophyte (dioicy) is one such feature of particular importance, as it is observed in the majority of bryophytes and creates intraspecific specialization of male and female individuals. The prevalence of sexually dimorphic mosses raises the possibility of sex-specific interactions with fungi as observed in some vascular plants. Here I investigated how moss sex shapes fungal communities associated with gametophytic tissues of the ubiquitous moss, Ceratodon purpureus. Using greenhouse populations of C. purpureus grown in a common garden, I examined fungal community structure and overall abundance of fungal biomass associated with male and female individuals from multiple populations. I hypothesized that individual mosses would harbor unique fungal communities based on their sex, and that overall fungal biomass associated with host tissues would differ significantly due to differences in morphological and physiological characteristics between the sexes. I found that fungal community composition and overall abundance (i.e. biomass) differ between male and female individuals of C. purpureus, and that sex-specific patterns are retained across individuals from three different populations. This work provides a first glance at how genetically based sexual systems in early land plants influence affiliated fungal community composition.

Three experiments were designed to determine if and how steelhead trout, Oncorhynchus mykiss, may affect chinook salmon, O. tshawytscha, when they are confined together as in a raceway or on a barge. We observed groups of chinook and steelhead together and groups of only chinook in a behavioral experiment to determine if steelhead are aggressive and if their presence changed the behavior of chinook. Two physiological experiments were completed to determine if the loading of steelhead on top of chinook and if the introduction of odor from rainbow trout (steelhead not available) caused a change in plasma cortisol levels in chinook. It was found that chinook showed characteristics of a schooling species, while steelhead exhibited territory holding characteristics. Behavioral changes in chinook were observed when steelhead were present. Chinook grouped with steelhead reduced their movements, darted less, were attacked up to 16 times more often, and were found less frequently in the shade than groups of only chinook. Steelhead were found to establish territories and defend them with chases, charges, and nips. In attempts to establish territories and defend them, steelhead attacked chinook as often as they attacked other steelhead even though chinook showed little aggression toward steelhead. In a physiological experiment, chinook experienced the loading of salmonids into their tank. Chinook had higher levels of plasma cortisol at 2 and 32 hours after the loading of steelhead than chinook that were loaded with chinook or controls (no loading). A second physiological experiment with odor showed that chinook that received rainbow odor and those that received chinook odor had similar levels of plasma cortisol. Cortisol levels (two hours after the odor was introduced) were higher in chinook receiving either of the scented waters than in those that did not receive any odor. In conclusion, all three experiments indicated that the presence of juvenile steelhead trout affect juvenile chinook salmon behavior and physiology. / Graduation date: 1998

Graduation date: 1995

<p>The effects of climate change on forest dynamics will be determined by tree responses at different life-stages and different scales -- from establishment to maturity and from individuals to populations. Studies incorporating local factors, such as natural enemies, competition, or tree physiology, with sufficient variation in climate are lacking. The importance of global and regional climate variation vs. local conditions and responses is poorly understood and may only be addressed with large datasets capturing sufficient environmental variation. This dissertation uses several large datasets to examine tree demographic and ecophysiological responses to light, moisture, predation, and climate in eastern temperate forests of North Carolina. </p><p> First, I use a 19-yr seed rain record from 13 forest plots in the piedmont, transition zone, and mountains to examine how climate-mediated seed maturation and density-dependent seed predation processes increase population reproductive variation in nine temperate tree species (Chapter 1). I address several hypotheses explaining interannual reproductive variation, such as resource matching, predator satiation, and pulse resource dynamics. My results indicate that (1) interannual reproductive variation increased as a result of seed maturation and seed predation processes, (2) seed maturation rates increased under warm, wet conditions, and (3) seed predation rates exhibited negative and positive density-dependence, depending of tree species and type of seed predator (specialist insects vs. generalist vertebrates). Because positive density-dependent seed predation dampened and negative density-dependent seed predation amplified the effects of climate-mediated maturation on reproductive variation, this study showed evaluations of tree reproduction need to incorporate both climate and seed predation.</p><p> Next, I use an 11-yr record of annual tree seedling growth and survival in 20 tree species planted in the piedmont and mountains to quantify individual tree seedling growth and survival responses to spatial variation in resources and temporal variation in climate (Chapter 2). First, I tested whether height-mediated growth provides an advantage to large individuals in all environments by amplifying responses to light and moisture or only when those resources were plentiful. Second, I tested whether allometric and survival responses differed among species based on life-history strategies. Individual height amplified tree seedling growth. However, some species exhibited amplification at moderate to high resource levels as well as depression of growth in large individuals growing in low light and moisture environments. Shade intolerant species exhibited an increasing ratio of height to diameter growth and increasing survival probability with both increasing light and moisture resources. Conversely, shade tolerant species exhibited decreasing height to diameter ratio with increasing light, possibly because of biomass allocation toward acquisition of limiting light resources. Despite relative small effects of drought and winter temperature of tree seedling demography, the results of this study indicate that individual tree seedlings sensitive to light and moisture environments, such as large seedlings and seedlings of shade intolerant species, growing in shaded or xeric sites may be particularly vulnerable to climate induced mortality. </p><p> Finally, I examine interannual and interspecific variation in canopy conductance using four years of environmental (vapor pressure deficit, above canopy light, and soil moisture) and stem sap flux data from heat dissipation probes for six co-occurring tree species. I developed a state-space modeling framework for predicting canopy conductance and transpiration which incorporates uncertainty in canopy and observation uncertainty. This approach is used to evaluate the degree to which co-occur deciduous tree species exhibited drought tolerating and drought avoiding canopy responses and whether these patterns were maintained in the face of interannual variation in environmental drivers. Comparisons of canopy conductance responses to environmental forcing across species and years highlighted the importance of tree sensitivity to moisture limitation, both in terms of high vapor pressure deficit and low soil moisture, and tree hydraulic characteristics within diverse forest communities. The state-space model produced similar parameter estimates to the more traditional boundary line analysis, performed well in terms of in-sample and out-of-sample prediction of sap flux observations, and provided for coherent incorporation of parameter, process, and observation errors in predicting missing data (i.e., gap-filling), canopy conductance, and transpiration.</p><p> Much needs to be learned about forest community responses to climate change, however these responses depend on local growing conditions (light and moisture), the life-stage being examined (seedlings, juveniles, or mature trees), and the scale of inference (individuals, canopies, or populations). Because climate change will not occur in isolation from other factors, such as stand age or disturbance, studies must characterize tree responses across multidimensional gradients in growing conditions. This dissertation addresses these challenges using large demographic and ecophysiological datasets well-suited for global change research.</p> / Dissertation

The black-ribbed mussel, Septifer virgatus, is a northern species which forms dominant bands in the mid-low levels of exposed rocky shores along the Northwest Pacific coast. S. virgatus is thought to reach its southern distributional limits just south of Hong Kong. In Hong Kong, mass mortalities of S. virgatus were recorded with the onset of the hot and wet season, with mussel cover decreasing at the upper limit of the mussel bed at Shek O from 82 % (~1746 ind m-2) in May to 9 % (~ 38 ind m-2) in August 2012. Elevated temperatures played an important role in driving physiological responses of the mussel, including heart rate, oxygen consumption and mantle water and haemolymph osmotic concentrations. The upper thermal limit in water (36 °C, as indicated by the Arrhenius breakpoint temperature, ABT), was unlikely to be reached by local seawater, but the ABT in air (~ 41 °C) was often lower than rock temperatures on Hong Kong shores, suggesting S. virgatus is living at its thermal limit. When immersed, both heart rates and oxygen consumption increased from 25 – 35 °C and dropped beyond 35 °C; whilst in air, haemolymph and mantle water osmolalities increased with duration (0 vs 6 hrs) and temperature (30 vs 40 °C) and 60 % of individuals died at 40 °C after 6 hours. Mortality of S. virgatus is, therefore, linked to the high temperatures and desiccation stress experienced on the shore, which are likely to impose high energetic costs. To better understand the performance of S. virgatus under natural conditions, and the energetic implications of thermal stress on its survival and fitness and hence potential distribution, a Dynamic Energy Budget (DEB) model was constructed. The model had a high goodness of fit. Mussels were predicted to live 5 years, and their main growth and energy reserves were derived from high assimilation during the hot and wet season when food was most abundant, while another slower growth period and reproduction occurred during the cool and dry season. Energy stored in the reserve during growth periods was likely to be allocated to combat thermal stress during the hot and wet season and reproduction during the cool and dry season. The DEB model was used to investigate the energy allocation strategies of S. virgatus under the most conservative and extreme scenarios associated with climate change as projected by the IPCC. The model predicted that reproductive events throughout the mussels’ life-span would be reduced by 30 – 70 %, despite an increase (18 – 470 %) in number of eggs per event. This reduction in the number of reproductive events might not be able to sustain local populations due to the high annual mortality. Such a decrease in performance and fitness, associated with not being able to reach the energy threshold necessary for somatic maintenance, suggests that S. virgatus may be limited to living lower on the shore, where conditions and duration of exposure are more benign, and ultimately experience a northwards range shift as environmental temperatures increase. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

Saccostomus campestris display sexual disparity in the use of summer daily torpor in response to energy stress. The hypothesis that males may compensate for a limited heterothermic capacity with lower normothermic body temperatures by maintaining lower resting metabolic rates relative to females was tested. Furthermore, the influence of testosterone on torpor incidence in males was investigated. Body temperature (T[b]) and oxygen consumption (VO₂) were measured at various ambient temperatures (Tₐ) and were compared between the sexes under food ad libitum and food restriction treatments. There were no significant differences in T[b] and VO₂ between sexes under food ad libitum treatment. Under food restriction there were pronounced sex differences in the employment of heterothermy. Females defended a lower setpoint T[b] for torpor (ca. 25°C), than males (ca. 29°C), and also employed torpor more frequently than males. Non-torpid males did, however show slight reductions in VO₂ under food restriction. The effect of testosterone on daily torpor was investigated by comparing minimum T[b]and torpor frequency of castrated mice implanted with testosterone-filled (experimental) and saline-filled (control) silastic capsules in response to food ad libitum and food restriction treatments. Testosterone inhibited torpor in males. The majority of control animals employed torpor under both food ad libitum and food restriction diets. It was concluded that although the animals were capable of shallow, summer torpor, it was confined to moderate ambient temperatures and was not used at low Tₐ's where several animals became pathologically hypothermic. Females derive energetic benefits from the use of torpor whereas males may partially compensate for their limited heterothennic capacity by a reduction in resting metabolic rates, accompanied by moderate reductions in body temperature during energetically stressful periods. The difference in the capacity for daily heterothenny between sexes was attributed to differences in their reproductive physiology. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

An ecophysiological comparison among species was conducted to investigate the possible factors controlling the distribution of North American spruce (Picea) species, especially with regard to the possible influence of global change. The seedlings of 8 North American spruce species were grown in a growth chamber, with half of them being given an episodic 'increased temperature and drought' stress treatment. Trait values among species, particularly growth analysis components, were compared and related to climatic variables associated with the geographical range of the species. Relative growth rate (RGR) and specific leaf area (SLA) were positively correlated with latitude, and the leaf weight ratio (LWR) variation negatively with the dryness of species' natural ranges. All these relationships hold with both messed and unstressed seedlings, even thou seedling response to the stress was significant. The SLA-latitude and LWR-dryness relationships are likely to have ecological significance, and this indicates that foliage stricture (SLA) and allocation (LWR) play important roles determining a species range along temperature and dryness gradients.

Thesis (Ph.D.)--University of Western Australia, 2007.

Water use efficiency (WUE), measured as the ratio of plant biomass to water consumption, is an essential agronomical trait for enhancing crop production under drought. Measuring water consumption is logistically difficult, especially in field conditions. The general objective of the present Thesis is to respond to three main questions: (i) can WUE be determined by using carbon isotope discrimination (CID), easy to measure?, (ii) how WUE and CID variation analysis can contribute to the genotypic selection of sunflower subjected to drought?, and (iii) can WUE variation be revealed by the variation of plant-water relation traits. Four experiments were carried out in greenhouse across two different years: (i) on two drought scenarios, progressive soil drying and stable water-stress, and (ii) on five levels of soil water content. The main traits that have been measured include WUE, CID, as well as plant-water relation traits, i.e. control of transpiration (FTSWt), water extraction capacity (TTSW), and dehydration tolerance (OA). A highly significant negative correlation was observed between WUE and CID, and a wide phenotypic variability was observed for both WUE and CID. A wide variability was also observed for FTSWt, TTSW and OA. The results provide new insight into the genetic control of WUE and CID related-traits, which, unlike to other crops, genetic control of WUE, CID, and TTSW in sunflower have never been reported in the literature. Further, quantitative trait loci (QTL) mapping for FTSWt was never reported in any plant species. The QTL for WUE and CID were identified across different drought scenarios. The QTL for CID is considered as a ‘‘constitutive’’ QTL, because it is consistently detected across different drought scenarios. The QTL for CID co-localized with the QTL for WUE, biomass and cumulative water transpired. Co-localization was also observed between the QTL for FTSWt and TTSW, between the QTL for TTSW and WUE-CID-biomass, as well as between the QTL for FTSWt-TTSW and biomass. This study highlights that WUE is physiologically and genetically associated with CID. CID is an excellent surrogate for WUE measurement, and can be used to improve WUE by using marker-assisted selection (MAS) to achieve the ultimate goal of plant breeding at genomic level.