A. R. O. Chapman

Bio: A. R. O. Chapman is an academic researcher. The author has contributed to research in topics: Functional ecology. The author has an hindex of 1, co-authored 1 publications receiving 215 citations.

Stress tolerance in intertidal seaweeds

Abstract: Intertidal seaweeds are periodically exposed to air where they experience a variety of potentially stressful environmental conditions, including nutrient limitation, high light, high and low temperature, desiccation, and osmotic stress. This paper considers the current understanding of stress tolerance in intertidal seaweeds and discusses ways in which future research could increase our understanding of the role of environmental factors in the ecology and physiology of these algae. We believe research is required in at least three areas. 1) Laboratory physiological studies have established that correlations exist between stress tolerance and the vertical distribution of species. However, little information is available on the importance of stress in determining community structure in nature. Field experiments are essential to relate the impact of single or multiple stresses on the survival, growth, and reproductive output of macroalgae. In paticular, it is necessary to clarify the role of sublethal stress in determining the outcome of competitive interactions. 2) With the exception of obvious lethal effects or damage associated with extreme environmental conditions, such as unusually hot and dry weather, it is difficult to evaluate the occurrence and severity of stress in natural populations of seaweeds. There is a need to develop molecular and biochemical markers specific for individual stresses or groups of stresses to allow the unambiguous and direct determination of stress in situ. 3) Despite the apparent importance of stress in intertidal seaweeds, we are largely ignorant of the mechanistic basis of tolerance. The application of currently available tools of molecular and cell biology to the investigation of stress-induced transcriptional and translational changes could enormously increase our understanding of both the sites of, and pathways involved in, stress tolerance. In summary, there are numerous unanswered fundamental questions about the stress tolerance of intertidal seaweeds, providing opportunities for research ranging from field ecology to molecular biology and biochemistry.

The Population Biology of Large Brown Seaweeds: Ecological Consequences of Multiphase Life Histories in Dynamic Coastal

Abstract: Seaweed population biology has received far less attention than trophic dynamics, yet is critically important in establishing and maintaining algal communities Complex life histories of habitat-forming kelps and fucoids, including spores, gametophytes, gametes, and microscopic and macroscopic benthic stages, must be considered within the context of their highly dynamic nearshore environments We evaluate differences within and between kelps and fucoids in life histories as they affect population biology; dispersal and potential limitations in population establishment; macroscopic stages and variations in survival and longevity affecting stand structure; and microscopic stage responses to disturbance and variation in the physical environment We suggest that the commonly made comparisons of seaweeds with terrestrial seed plants are misleading because of large differences in morphology, environments, and the ephemeral nature of propagule banks in the sea We conclude that progress in understanding algal populations depends on better knowledge of microscopic stages and on feedback through density-dependent reproductive processes, dispersal, and settlement

The influence of species diversity and stress intensity on community resistance and resilience

Abstract: Recent theory, such as the insurance hypothesis, suggests that higher species diversity may dampen perturbation dynamics within a community. The dynamics of a rocky intertidal macroalgal community were evaluated using an experimentally induced heat stress applied at the end of a 15-mo manipulation of diversity. This pulse event produced a gradient of thermal stress within plots and, consequently, different degrees of perturbation. In gen- eral, the resistance of the community to the thermal stress was forecast by the pre-stress cover of dominant species, total algal cover, and standing biomass. Because higher diversity treatments, especially those containing the dominant algal group, fucoids, had higher overall abundance, highest diversity treatments were the most severely affected. The stress was also relatively nonselective, in that species were reduced in roughly equivalent proportions, suggesting an important distinction for predicting when diversity will not influence dis- turbance dynamics. The resilience of the community was strongly dependent on which species were initially present in the plots and the degree of disturbance. In highly disturbed areas, although the recovery trajectory was similar in early successional stages, differences emerged later; these differences appear to be attributable to the composition of the sur- rounding regeneration pool. For treatments not receiving the thermal stress, low-diversity plots without fucoids remained in states unlike the reference condition for most of the monitored resilience period. But plots in high-diversity treatments, even areas within plots that had experienced moderate disturbance, returned to states similar to the reference quick- ly. Thus, resilience (but not resistance) results are consistent with the insurance hypothesis. Overall, diversity's influence on community dynamics is complex and will depend on the characteristics of the stress as well as the characteristics of the species present in the

Frayed at the edges: selective pressure and adaptive response to abiotic stressors are mismatched in low diversity edge populations

Abstract: Summary 1. Theory predicts that population structure and dynamics affect a population’s capacity for adaptation to environmental change. For isolated, small and fragmented populations at the trailing edge of species distributions, loss of genetic diversity through random genetic drift may reduce adaptive potential and fitness levels for complex traits. This has important consequences for understanding population responses to, for example changing climate, but has rarely been tested in natural populations. 2. We measured the intertidal thermal environment and tidal exposure (emersion) times for natural populations of the intertidal seaweed Fucus serratus at the centre (southwest UK) and southern edge (northern Portugal) of its range in the Eastern Atlantic, and for a congener, F. vesiculosus , whose range extends further south to Morocco. Fitness-related traits of individuals at each location were measured in common garden experiments: physiological resilience to desiccation and heat shock (PSII quantum yield), and the molecular phenotype of the heat shock response (quantitative PCR of heat shock protein gene transcripts). 3. The realized thermal environment experienced by F. serratus was similar at the centre and southern edge of its distribution because the maximum shore height (and emersion period) was reduced in southern populations. For F. vesiculosus , thermal maxima were higher and occurred more frequently in the south, although maximum vertical height (emersion time) remained similar to central populations. 4. Edge populations of F. serratus were less resilient to desiccation and heat shock than central populations, and expression of heat shock genes was higher at the same temperature, suggesting greater cellular stress. In contrast, there was no evidence for physiological divergence in heat shock response in F. vesiculosus , and little variation in gene expression. 5. Synthesis. We provide evidence that compared with range-centre populations upper intertidal limits of F. serratus at the southern edge are ‘pruned back’ by abiotic stressors. Rather than being locally adapted, these small populations are less resilient to abiotic stresses and experience greater cellular stress during heat shock. These results suggest that ongoing climate forcing factors may threaten small, fragmented rear edge populations because of inherently reduced fitness and lower adaptive capacity relative to larger central populations.

Identifying the interacting roles of stressors in driving the global loss of canopy‐forming to mat‐forming algae in marine ecosystems

Abstract: Identifying the type and strength of interactions between local anthropogenic and other stressors can help to set achievable management targets for degraded marine ecosystems and support their resilience by identifying local actions. We undertook a meta-analysis, using data from 118 studies to test the hypothesis that ongoing global declines in the dominant habitat along temperate rocky coastlines, forests of canopy-forming algae and/or their replacement by mat-forming algae are driven by the nonadditive interactions between local anthropogenic stressors that can be addressed through management actions (fishing, heavy metal pollution, nutrient enrichment and high sediment loads) and other stressors (presence of competitors or grazers, removal of canopy algae, limiting or excessive light, low or high salinity, increasing temperature, high wave exposure and high UV or CO2), not as easily amenable to management actions. In general, the cumulative effects of local anthropogenic and other stressors had negative effects on the growth and survival of canopy-forming algae. Conversely, the growth or survival of mat-forming algae was either unaffected or significantly enhanced by the same pairs of stressors. Contrary to our predictions, the majority of interactions between stressors were additive. There were however synergistic interactions between nutrient enrichment and heavy metals, the presence of competitors, low light and increasing temperature, leading to amplified negative effects on canopy-forming algae. There were also synergistic interactions between nutrient enrichment and increasing CO2 and temperature leading to amplified positive effects on mat-forming algae. Our review of the current literature shows that management of nutrient levels, rather than fishing, heavy metal pollution or high sediment loads, would provide the greatest opportunity for preventing the shift from canopy to mat-forming algae, particularly in enclosed bays or estuaries because of the higher prevalence of synergistic interactions between nutrient enrichment with other local and global stressors, and as such it should be prioritized.