This thesis centres on mesoscale spatial patterns in species richness, as a measure of intertidal biodiversity. It is split down two lines of enquiry. The first correlated primary producer species richness with trophic functioning (SIA) within two biogeographical regions. Consumers were anticipated to either specialise or generalise their resource use depending on the richness of these resources or, alternatively, mesoscale environmental features were anticipated to dominate resource contributions. Across Northern Ireland, a gradient contrasting semi-enclosed water bodies with the operl coast was recorded, with isotopic variation reflecting physical (e.g. fetch, embayment) rather than biological (e.g. macroalgal diversity) factors. Along Northern Chile, isotopic variation alluded to a broad split in resource use between localities on the outer Mejillones Peninsula and those in bay situations. Mussel utilisation of kelp matter was supported where other POM constituents were scarce. Macroalgal community compositions tracked environmental patterns, suggesting predictability of consumer 81SN. Furthermore, taxonomic relatedness was hypothesised to source trophic equivalence. Despite large regional differences in abiotic conditions (although not biotic differences), hypothesis support was found in suspension feeding mussels, potentially allowing broad-scale comparison of isotopic baselines (Post, 2002). , Secondly, adaptable proxies for sampling effort were developed to enable use of collated datasets following Blight et al. (2009). Macroalgal and molluscan species richness across Northern Ireland were influenced by mesoscale wave fetch, tidal range, and sampling effort variables, but OLS regression was inadequate. The extent to which rare and common species contribute to UK-wide richness patterns for major intertidal taxonomic groups was investigated, finding that common species held stronger correlations than the full assemblage groups, whilst rarer species were variable. On-going work is planned to investigate the relationship of these patterns with abiotic and biotic habitat variables using a robust spatial regression model. Salient themes of the thesis were discussed in the final chapter.

No description available.

No description available.

Coastal grasslands, such as salt marshes and sand dunes, provide many important ecosystem services including 'supporting services' (soil formation, primary productivity and nutrient cycling), 'provisioning services' (fresh water supply, food and fibre products, biochemical or genetic resources), 'regulating services' (equable climate, pollution control, flood prevention, invertebrate pollination and pest regulation) and 'cultural services' (recreation, education and aesthetic appreciation). Historically, salt marsh and sand dune grasslands were commonly used as agricultural livestock grazing land. Currently, some of these coastal grasslands are 'conservation grazed' (i.e. extensively grazed to maximise plant diversity and to provide a suitable habitat for over-wintering bird species), others have been 'abandoned' (i.e. large herbivores removed) due to the removal of agricultural subsidies or remain historically 'un-grazed'. Grazing management of coastal grasslands influences biological and physical habitat characteristics, ecosystem function, biodiversity and ecosystem service delivery. Understanding the impact of grazing is therefore vital to enable future robust management recommendations. Biodiversity is often used as an indicator of ecosystem health and ecosystem service provision with conservation priorities allocated accordingly. It is therefore essential to critically assess just how important biodiversity is to the provision of ecosystem services within a wide range of habitats. The review chapter draws together evidence for this argument from salt marsh and sand dune habitats with the conclusion that functional diversity and composition are more important than biodiversity per se (Chapter 2). The experimental chapters of this thesis deal with the impact of grazing upon temperate salt marsh and sand dune grassland biodiversity and ecosystem service provision. 'Grazed' (cattle grazed < 8 cm) and historically 'un-grazed' upper salt marsh plots were compared. 'Fully grazed' (ponies 0.2 ha⁻¹, cattle 0.05 ha⁻¹ and rabbits 45 ha⁻¹), 'rabbit grazed' and 'un-grazed' (for 8 years) fixed sand dune grassland plots were also evaluated. Firstly, how grazing management affected ecosystem service provision of sand dune grassland was examined, by measuring a wide range of biophysical variables as proxies for ecosystem services (Chapter 3). 'Supporting' and 'regulating' services were provided predominantly by the un-grazed, 'provisioning' and 'cultural' services by the extensively grazed grassland. Secondly, the impact of short sward cattle grazing on the abundance, composition and diversity of the ground dwelling invertebrate community of an upper salt marsh was assessed using pitfall traps (Chapter 4). The findings showed that both cattle grazed and un-grazed saltmarsh habitat should be maintained to maximise invertebrate abundance and diversity and provide suitable habitat for coastal specialists. Thirdly, greenhouse gas emissions from grazed and un-grazed salt marsh were measured monthly for one year. Additionally, below-ground gas sampling tubes were used to measure soil methane concentrations (Chapter 5). Carbon dioxide efflux was greater from the un-grazed marsh soil but 'hotspots' of methane efflux were only found on the grazed marsh. Finally, the influence of grazing on the soil microbial community of both salt marsh and sand dune grasslands was measured by microbial biomass (fatty acid phospholipids: PLFAs), bacterial growth rate (Leucine incorporation) and respiration rates (Chapter 6). Microbial biomass, PLFA markers and bacterial growth rate were all influenced by grazing management. In summary, this work concludes that grazing management clearly affects biological and physical habitat characteristics, biodiversity, ecosystem function and ecosystem service delivery (Chapter 7). Management of coastal grasslands evidently involves trade-offs between biodiversity conservation and multiple ecosystem service provision.

Biodiversity is under increasing pressure from human activities driving global environmental change. Global climate driven change interacts with regional (e.g. eutrophication) and local scale impacts (e.g. overexploitation). Long-term and broad scale data are required to distinguish human-induced changes from natural fluctuations. The aim of this thesis was to explore the responses of intertidal ecosystems to climate change and other impacts, using the Azores as a model system, by describing patterns and experimentally testing processes. Relevant long-term environmental data on surface air and sea temperature testing processes. Relevant long-term environmental data on surface air and sea temperature plus wave action were collected. Baseline data collected in the 1980s was compared to the 2010s. Descriptive studies examined the patterns at the individual and community level providing evidence of long-term changes in response to greater stress due to changing environmental conditions. At the individual level, changes in phenology of two Azorean species of limpets (Patella aspera and Patella candei gomesii) were assessed over time (1980s versus 2010s) and space across the Archipelago. Evidence of temporal and spatial changes were found in the reproductive cycle of the limpets; these can probably be related with climate change and spatial gradients in environmental conditions across the Archipelago. At the community level, long-term changes in distribution of key intertidal species were assessed. Changes were found not only in the abundance but also in the vertical distribution of the species. Some of these may be ascribed to recent climate change, whereas other may be better explained by the overexploitation of keystone limpet grazers. Finally, community response to the loss of a key intertidal northern species (Fucus spiralis) was experimentally simulated. Fucus spiralis showed fast recovery rates and, unlike expected, its loss had minimal effect on the associated assemblages. Overall, results indicate that there have been some significant changes on the Azorean rocky shores. These included changes in the phenology, abundance and distribution of species. My results suggest F. spiralis in the Azores is not a key species as found elsewhere; so its potential loss may have little to no impact on the remainder of the community. My research highlights the key role of enforced marine reserves in distinguishing between the long-term effects of changes in climate from other anthropogenic activities such as fishing. Whilst there was some evidence of climate driven change, it is likely that human overexploitation of limpets has a greater effect.

There has been growing concern by policy and other decision makers that timber extraction by local communities is the main threat to achieving sustainable management of mangrove systems in Unguja Island, Zanzibar, Tanzania. However, this concern, and responses to the perceived threat to date, do not appear to be informed by a clear understanding of the complexity and capacity of mangrove Social-Ecological Systems (SES) at different scales to adapt to this and other disturbances. The aim of this study was to assess the resilience of mangroves to the increased demand for provisioning ecosystem services and other drivers with a view to identifying options for sustainable mangrove management on Unguja Island. This study was guided by broad resilience concepts and specific approaches, particularly the components-relationship-innovation-continuity framework developed by Cumming et al. (2005). Data relating to both social and ecological components of the mangrove system was collected. A total of 185 plots were surveyed within mangrove forests from three case study sites of Pete- Jozani, Charawe and Michamvi Shehia (lowest administrative unit) on Unguja Island in which mangrove tree species, diameter and height of trees, the numbers of seedlings and stumps were collected to assess the ecological condition of the forests. Key informant interviews (with government officials and village stakeholders), semi-structured household interviews, village meetings and focus group discussions (with beekeepers, mangrove harvesters, village elders and village conservation organisations) were used to collect social-economic data from the three case study sites. The results showed that between the 1920s and 1970s at each case study site local communities reported that they were able to obtain diverse ecosystem services while the key variables that defined the identities of the mangrove SES were maintained. The mangrove SES from each case study site was found to have changed over the past three decades in temporal and spatial scales and currently reside at different phases of change. The current mangrove ecological systems of Pete, Charawe and Kinani (part of Michamvi) were found to have been degraded compared to the past. This was evidenced by the quality and quantity of trees present, with a relatively high density of small-sized mature trees with correspondingly small basal areas and volumes, together with significant numbers of tree stumps in the ecosystems. The areas covered by mangrove vegetation in the study sites were also found to have declined. The decline in quality and quantity of trees was found to correspond with a reduction in desirable ecosystem services as reported by communities. The levels of dependence on mangrove wood provisioning ecosystem services and management approaches have changed across the case study sites. Excessive rates of harvesting of mangrove wood were identified as the key direct driver on mangrove ecological systems, which was fuelled by several underlying drivers including poverty, population change, limited livelihood activities, inappropriate management regimes, and markets for trading mangrove wood ecosystem services. Vijichuni mangrove (another part of Michamvi) was found to be an exceptional case whereby the quality and quantity of mangrove ecological variables had improved. Availability of reliable alternative income sources by the majority of villagers and effective management institutions had contributed to these changes. The drivers identified were used to develop three alternative future scenarios to explore whether projected changes will result in the mangrove SES maintaining their identities in the future. The findings suggest that the Non-inclusive State Control scenario strictly conserves the mangroves, but does not provide alternative livelihood opportunities to improve the well-being of local communities and so is not desirable. Coastal Boom scenario, characterised by unregulated economic growth, particularly in the tourism sector and community forest management with limited benefits for local communities, results in complete degradation of mangrove and reduced wellbeing of local people. However, the Techno-green scenario which includes green growth, access to low-cost cooking energy and co-managed mangrove forests with benefits for local communities, provides decision makers and other stakeholders with an alternative pathway towards more resilient mangrove SES in Unguja.

The methylated sulfur compound dimethylsulfide (DMS) plays a major role in the biogeochemical sulfur cycle and atmospheric chemistry. Bacteria are a main sink for DMS in the global sulfur cycle and can utilise DMS as a sole carbon and energy source. This study investigated the diversity and activity of bacteria capable of DMS degradation and associated with the salt marsh plant Spartina anglica known to be a producer of the DMS precursor dimethylsulfoniopropionate (DMSP). Initially, it was shown that S. anglica is rich in DMSP throughout the entire seasonal cycle in the Stiffkey salt marsh providing a likely hotspot for DMSP- and DMS-degrading bacteria. DMS uptake experiments demonstrated that DMS degradation takes place in the phyllosphere and rhizosphere of S. anglica and denaturing gradient gel electrophoresis (DGGE) and high-throughput amplicon sequencing of the 16S rRNA revealed the dominance of bacteria related to α - and γ- Proteobacteria, as well as Flavobacteria in the phyllosphere of S. anglica, whereas the rhizosphere was mainly colonised by members of the classes γ-, δ-, α-, and ε-Proteobacteria and Bacteroidia. The diversity of DMS-degrading bacteria associated with S. anglica was first assessed by enrichment culture. DGGE analysis and high-throughput sequencing diversity of DMS enriched samples using the 16S rRNA gene as a marker suggested the dominance of Piscirickettsiaceae, Methylophaga and Methylophaga-like bacteria in DMS-enrichments of phyllosphere and rhizosphere samples of S. anglica. A functional gene marker analyses was carried out using the gene encoding methanethiol oxidase (mtoX), a key enzyme in DMS degradation and the gene encoding a DMSP lyase (dddP) to determine the diversity of bacteria degrading DMS and DMSP, respectively, in the phyllosphere and rhizosphere of S. anglica. The analysis for mtoX showed a great diversity of this gene in phyllosphere and rhizosphere of S. anglica and that major clades of mtoX clustered together with Sedimenticola, Methylohalobius, Methylophaga and other mtoX clones previously detected in surface sediments of the same salt marsh. The results for the functional marker gene analysis for the dddP gene suggested the dominance of Ruegeria-like species and Roseobacter-like bacteria but also of unidentified Ddd+ bacteria in the phyllosphere and rhizosphere of S. anglica. In order to identify the active DMS degraders in the phyllosphere and rhizosphere of S. anglica stable-isotope probing (SIP) combined with DGGE and highthroughput sequencing of the 16S rRNA gene was carried out. The SIP experiments revealed the dominance of Piscirickettsiaceae, Methylophaga and Methylophaga-like microorganisms in the rhizosphere of S. anglica. However, the DMS-degrading microbial community in the phyllosphere seemed more diverse than in the rhizosphere and microorganisms like Halothiobacillus, Xanthomonadaceae, Rhodanobacter but also Piscirickettsiaceae seemed to be involved. A comparative proteomic and transcriptomic experiment of Methylophaga thiooxydans, a microorganism found in phyllosphere and rhizosphere of S. anglica, revealed the general pathways involved in methanol but especially DMS degradation. During DMS cycling the protein and the protein-encoding gene for the methanethiol oxidase (MtoX/mtoX) was highly expressed. A metaproteogenomic experiment provided an insight into the taxonomy and functional diversity of the microbial community associated with the Spartina anglica phyllosphere. Analysis of the metagenome provided evidence that the microbial community associated with S. anglica is dominated by γ-Proteobacteria such as Halomonadales, Alteromonadales, Oceanospirillales, and Thiotrichales and the alphaproteobacterial order Rhodobacterales and showed therefore a major difference to the bacterial community composition in the phyllosphere of for instance A. thaliana, clover, soybean and rice. The detection of DMSP lyase encoding genes and genes encoding proteins for DMS degradation confirmed the genetic potential for the observed DMSP and DMS degradation activity previously measured in the phyllosphere of S. anglica. The metaproteomic experiment allowed a first insight into the proteins expressed in the phyllosphere of S. anglica which also suggested that mainly γ-Proteobacteria and α-Proteobacteria are dominant populations occurring in this habitat. New insights were gained into the activity and diversity of DMS-degrading microbial communities associated with a salt marsh plant that represents a significant component of salt marsh plant communities world wide. Not only was the taxonomic and functional diversity of DMS-degrading microorganisms associated with S. anglica greater then previously realised, the observation of considerable potential of above-ground plant-associated DMS degradation in the phyllosphere demonstrates a previously unrealised sink in the DMS cycle in coastal ecosystems, which is clearly more complex than previously appreciated.

Managed realignment is now widely seen as an important part of coastal management strategy, as an environmentally sustainable, cost-effective alternative to traditional, hard defences. However, the trajectory of salt marsh development in managed realignment schemes remains uncertain and it is unclear how sites should be managed to fulfil both coastal defence and biodiversity objectives. In this study, the overarching aim is to find out ways in which we can create salt marshes that are self-sustaining and function as closely to natural ecosystems as possible, by considering the linked biogeomorphological processes in salt marsh ecosystems. Such an approach will improve predictions of habitat development and recommendations for future practice in managed realignment schemes. The first important question is: How do pre-alignment plant species growing within managed realignment sites respond to salt water inundation upon re-exposure to flooding? Understanding the responses of the terrestrial vegetation community to initial seawater flooding may improve predictions of the short-term transition into salt marsh vegetation. To answer this, the effects of seawater inundation on pre-existing vegetation are initially examined in a greenhouse experiment in Chapter 3. It was demonstrated that one common plant species component of many coastal grasslands, Trifolium repens, responds poorly to simulated seawater soil flooding, but the response is population-, i.e. ecotype-, specific; therefore, the species consequently has an adaptive capacity to withstand short periods of soil inundation by seawater. In addition, I look at how and why the vegetation community of a restored site transitions following the reintroduction of tidal water, including the response of the original community of non-salt marsh plant species to salt water inundation and subsequent salt marsh plant community reassembly. After three years of tidal inundation at South Efford managed realignment site (SEM), terrestrial vegetation had decreased in cover and nearly all species recorded on the adjacent natural marsh had colonised. However, the cover of salt marsh species was limited by waterlogging, caused by modifications to the tidal regime by a self-regulating tidal gate. This leads on to the second question: How do new engineering techniques alter the tidal regime and what specific aspects of the new regime drive plant community reassembly and sedimentation patterns? In Chapters 4, 5 and 6, three years of ecological and geomorphological development are investigated in response to a variable inundation regime imposed by regulated tidal exchange at SEM. Inundation of the marsh surface was very regular, but water levels were not deep enough to encourage sufficient morphological development, sedimentation nor hydrochory. In contrast, ecological development was limited by waterlogging. Balancing the tidal regime with the drainage efficiency of managed realignment sites may be the most likely scenario under which restored salt marsh will develop with maximum biodiversity benefits. Otherwise, further management techniques, such as the excavation of tidal channels, may need to be employed to improve site drainage. Consequently, the final question is: How can biodiversity be maximized on realignment sites through the use of different management techniques and site design? Tidal channels on a range of managed and natural sites were shown to improve the drainage efficiency of adjacent soils (particularly channels of greater width and/or higher Strahler order). Plant species diversity was generally higher on channel banks in managed realignment sites. On sites with highly reduced soils, the colonisation and establishment of halophytes could be advanced on the banks of tidal channels. Additionally, topographic heterogeneity introduced by tidal channels created a variety of habitat niches, which allowed a range of salt marsh species to establish in the absence of highly competitive species, such as Elymus repens. Results from this study could contribute to the generation of a number of recommendations for the implementation of managed realignment schemes, particularly regarding the excavation of tidal creek networks.

Sandy beaches are often highly allochthonous, depending on external subsidies of carbon and nutrients. Despite this, sandy beach macrofaunal assemblages have received little attention regarding their response to enhanced primary productivity generated from coastal upwelling. This thesis investigates the influence of upwelling on macrofaunal assemblages over a variety of spatial and temporal scales. Spatially, four regions were examined across two biogeographic provinces to remove temperature as a confounding factor, and limit biogeography-specific effects. A nested hierarchical design enabled both large and small scales to be examined and generalities about upwelling effects across multiple areas to be considered. Sampling was conducted in two seasons, and over two years, to test the persistence of any effects. Biogeography and region had the strongest influences on macrofaunal biodiversity. Upwelling influenced macrofaunal assemblages in every region when analyses were conducted at the species level. However, the particular effect, positive or negative, differed among regions depending on local factors, and between the response variables, abundance and biomass. Coarser scales of taxonomy, feeding guild and developmental mode were investigated; however, the influence of upwelling generally became weaker and more varied, and occasionally disappeared. Seasonality was greater on the South Coast but was still important in some analyses on the West Coast. At the small-scale, variation within-beaches was lower than between beaches, assemblage structure remained stable over time, and consistent zonation was not present. The influence of temperature on filtration rate and oxygen consumption of Donax serra was investigated to test a driving mechanism for assemblage responses to upwelling. Feeding ability was significantly reduced at colder temperatures indicating an important factor which may be involved in determining assemblage structure. These results suggest that alterations to upwelling regimes predicted under climate change scenarios will impact sandy beach macrofauna, however the specific outcome will depend on multiple contextual factors.

Estuarine systems are of crucial importance to the provision of goods and services on a global scale. High human population densities in coastal systems have caused an increasing input of pollutants, of which nutrient pollution is of major concern. Increasingly, these areas are also impacted by physical disturbance, which can originate from anthropogenic sources (e.g. bait digging, shipping) or climate change causing increasingly frequent and intense storms. The individual impacts of such stressors on ecosystems have been investigated however their combined impacts have received less attention. Cumulative impacts of multiple stressors are unpredictable and will likely result in non-additive effects. Further, the effect of local environmental context on multiple stressors is a relatively understudied topic. Work in this thesis compared the combined impact of nutrient enrichment and physical disturbance in Scotland and Australia, using a series of manipulative field experiments. Results demonstrate that response to stressors is highly context dependent, varying between and within geographic locations. While the background levels of stress may vary, by comparing these two locations it is possible to comment on the adaptations and response that communities within different parts of the world display when subjected to additional stress. This study demonstrates that environmental context must be considered when implementing future management practices. Further work demonstrated that the impact of multiple stressors varies depending on how the stress is applied –whether stressors are applied simultaneously or whether there is a delay between two stressors. This study was among the first of its kind, assessing the implications of how multiple stressors react with each other given the order and intensity in which stressors were applied. Results demonstrated that systems can become sensitised to stress making them increasingly vulnerable to additional stress. Future research should be focussed on incorporating ecologically relevant scenarios of how stressors will impact estuaries while considering how environmental context will mediate impacts.