The Egyptian Spiny-tailed Lizard, Uromastyx aegyptia (Forskål, 1775), inhabits the arid regions of the Middle East, where it relies heavily on self-dug burrows for thermoregulation and protection. This study investigates the burrow characteristics and microhabitat use of this species in the Ha’il region of northern Saudi Arabia. Data were collected from 369 active burrows over a five-year period (2013–2019), recording variables such as burrow entrance orientation, soil type, vegetation cover, and environmental factors including temperature, humidity, and light intensity. The results showed that burrow entrances were primarily oriented toward the north, northeast, and east, likely to reduce direct solar exposure. Burrows with north-facing entrances exhibited significantly cooler internal temperatures compared to those with south-facing entrances, while relative humidity was lower in north-facing burrows. The lizards showed a preference for burrows located in coarse sand and microhabitats with low to moderate vegetation cover. Given the ongoing rise in temperatures due to climate change, longterm monitoring of burrow characteristics, particularly entrance orientation, may provide valuable insights into how this species adapts to shifting environmental conditions.

Blooms of filamentous cyanobacteria regularly occur in the Baltic Sea during warm summer months. These blooms can be toxic and interfere with recreational activities. However, the underlying drivers of these events and how their distribution might change in response to future climate conditions remain poorly understood. To investigate this, we applied a multi-realm modeling approach that integrates environmental data from both marine and terrestrial systems, combined with climate projections, to predict future filamentous and nitrogen-fixing cyanobacterial distribution along Sweden's Baltic Sea coast. Our models identified several key factors significantly influencing bloom distribution: terrestrial temperature, precipitation during the wettest quarter, sea surface temperature, nitrate levels, and interactions between landbased and marine environmental variables. Our projections suggest an expansion of filamentous cyanobacteria in the northern Baltic Proper, Bothnian Sea, Bothnian Bay, and Arkona Basin driven by rising land temperatures by 2070, increasing sea surface temperatures by 2100, and declining salinity in specific basins. Overall, the results demonstrate that incorporating environmental data from both land and sea improves predictions of cyanobacterial distribution in coastal Baltic Sea regions. This multi-realm modeling strategy may also prove valuable for forecasting and managing harmful cyanobacterial blooms in other coastal areas experiencing similar environmental challenges.

The Western Reef Heron (Egretta gularis) has a wide geographic distribution, ranging from the coasts of West Africa to Southwest Asia, including the Arabian Peninsula. Despite this extensive range, detailed information on its incubation behavior remains scarce. To address this gap, we investigated the 24 h incubation behavior of Western Reef Herons on Al-Fanateer Island, Eastern Saudi Arabia, during early summer—a period characterized by pronounced diurnal fluctuations in ambient temperature. Using trail cameras and temperature loggers, we found that adults maintained nearly continuous attendance at the nest throughout the day, with incubation coverage exceeding 97% across all two-hour intervals. A slight reduction in nest attendance was observed during nighttime (lowest at 86.8% between 20:00–21:59). Incubating adults exhibited behavioral plasticity in response to ambient temperature: a sitting posture was predominant during cooler periods, while a shading posture was more frequent during peak heat. Incubating adults also adjusted their orientation with the solar angle, actively avoiding southern and western exposures during the hottest parts of the day. Despite substantial variation in ambient temperature, the temperature beneath the clutch ranged from 29.4 to 37.8 °C, which may indicate effective thermoregulation. These findings suggest that a combination of near-continuous nest attendance, posture adjustment, and solar orientation avoidance allows Western Reef Herons to mitigate thermal stress and maintain optimal conditions for embryo and chick development. We recommend long-term monitoring of incubation behavior in this species to further evaluate its adaptability to environmental changes, particularly those driven by climate variability.

The islands and coastal habitats of the Red Sea are home to diverse and endemic animal species. However, the current and future conservation status of these species remains unclear. One such species is the White-eyed gull (Ichthyaetus leucophthalmus), an endemic seabird of the Red Sea region that nests on the ground during the hottest months, from June to August. Despite the species' current state of knowledge, there is limited information about its biogeography and spatial distribution in response to ongoing climatic changes in the Red Sea region. In this study, we used a spatial clustering analysis combined with an ensemble modeling approach to predict the coastal distribution and identify potential hotspots for the White-eyed gull. We utilized two sets of current environmental variables and future climatic scenarios for the year 2050 derived from both marine and terrestrial domains. Our analysis identified 13 potential hotspots that are crucial for the conservation of the White-eyed gull. Our findings reveal that climate change is likely to significantly impact the spatial distribution of the White-eyed gull, potentially reducing its current suitable habitats and shifting its range further into the northern Red Sea and possibly to the Mediterranean Sea. Additionally, our models, which integrate marine and terrestrial variables, predict the biogeography of the White-eyed gull with 88–95 % accuracy. Our spatial clustering analysis combined with an ensemble modeling approach can inform conservation and management strategies for coastal areas identified as suitable habitats for the White-eyed gull. Furthermore, it has the potential to be applied to other seabird species with similar habitat requirements in the Red Sea region and beyond.

Microbial communities comprise immense diversity, mediating numerous ecosystem functions such as nitrogen transformation in aquatic ecosystems. Yet, how microbial communities and ecosystem functions respond to changes in environmental conditions at different spatial scales in aquatic habitats is not fully understood. This thesis investigates the effect of changes in environmental conditions at different spatial scales on Baltic Sea microbial diversity and nitrogen transformation, specifically denitrification, with a focus on biodiversity-ecosystem function relationship. Two spatial scale settings were examined. A small spatial scale setting was examined with experimental mesocosms of benthic sediment of different salinity and dissolved oxygen levels and at different spatial arrangements, and an incubation experiment conducted with benthic sediments from two different aquatic habitats enriched with 15N nitrate isotope. Microbial diversity, denitrification gene transcript abundances, and potential denitrification rate were analyzed. At a large spatial scale of the Baltic Sea benthic and coastal seascape, a metadata-based modeling approach was employed to investigate how current environmental conditions and future climatic change scenarios affect the predicted spatial distribution of key taxa of denitrifiers and nitrogen-fixing filamentous cyanobacteria. Results showed that salinity and dissolved oxygen levels significantly influenced denitrification capacity, according to analyses of transcript abundances of nirS and nosZ genes, which was mainly driven by habitat environmental conditions rather than habitat spatial arrangement. Bacterial community composition in experimental mesocosms was significantly affected by salinity. Findings from the small scale mesocosms experiments indicate that salinity can be an important driver of microbial denitrification capacity and affect microbial diversity in studied mesocosms. At large coastal and seascape scales, multi-realm environmental variables from both marine and terrestrial domains had significant impacts on the predicted distribution of the studied microbial taxa. The predicted distribution under different global warming trajectories indicated that rising temperatures in year2050 and 2100 risk reducing the current bio-climatically suitable areas of the studied denitrifiers and filamentous cyanobacteria across the Baltic Sea. The studies with experimental mesocosms and modeling approaches presented in this thesis contribute knowledge and novel predictions on the spatial response of ecosystem function and microbial communities to ongoing and future environmental changes in the Baltic Sea.

Östersjön genomgår stora miljöförändringar vilka förväntas påverka dess kustnära ekosystemfunktioner. Många ekosystemfunktioner, däribland kvävetransformation i akvatiska ekosystem, förmedlas av mikrobiella samhällen. Hur förändringar i miljöförhållanden i akvatiska livsmiljöer i olika rumsliga skalor och framtida klimatscenarier kan påverka relationen mellan mikrobiella samhällens mångfald och mikrobiella ekosystemfunktioner har varit understuderat. Avhandlingen undersöker effekten av förändringar i miljöförhållanden vid olika rumsliga skalor på relationen mellan mikrobiell mångfald och ekosystemfunktionen denitrifikation i kustnära  miljöer i Östersjön. Detta undersöktes på två rumsliga skalnivåer. På liten rumslig skala undersöktes experimentellt mesokosmer av mikrohabitat, med sediment med olika salthalt och nivåer av syre, i olika rumsliga arrangemang genom biogeokemisk och molekylär metodanalys. Potentiell denitrifikationshastighet, kvantitativ analys av transkript av denitrifikationsgener och mikrobiell diversitet analyserades. För analys av effekter på större geografisk rumslig skala, inom Östersjönskust- och havsområden, tillämpades en metadatabaserad spatial modelleringsmetod för att undersöka hur nuvarande miljöförhållanden och framtida klimatförändringsscenarier kan påverka prediktionen av den rumsliga fördelningen av studerade nyckeltaxa av denitrifierare och kvävefixerande filamentösa cyanobakterier. Resultaten visade att salthalt och syre signifikant påverkade den mikrobiella denitrifikationskapaciteten, enligt analys av transkript av nirS- och nosZ-generna, snarare än rumsligt arrangemang. Denitrifikationshastigheten var inte korrelerad med abundansen av nirS-transkript. Den bakteriella taxonomiska sammansättningen påverkades signifikant av salthalt. På kust- och havsskalenivå hade miljövariabler från både marina och terrestra domäner betydande inverkan på den predicerade fördelningen av de studerade bakteriella populationerna. Den förutspådda geografiska spridningen av de studerade denitrifierarna och filamentösa cyanobakterierna, under olika globala uppvärmningsscenarior, indikerade att stigande temperaturer år 2050 och 2100 riskerar att minska de nuvarande bioklimatmässigt lämpliga områdena i Östersjön för de studerade populationerna. Studierna med de experimentella mesokosmerna och modelleringsmetoderna som presenteras i avhandlingen bidrar med kunskap och nya förutsägelser om de rumsliga effekter på ekosystemfunktioner och mikrobiella samhällen under pågående och framtida miljöförändringar i Östersjön.

Denitrifying microbial communities provide an important ecosystem function in aquatic systems. Yet, knowledge on predictive and modeling of these complex and changing communities is limited. The emergently challenging question of how the geographical distribution of denitrifiers responds to ongoing and future environmental change is not yet fully understood. In our study we use metadata-based correlative niche modeling to analyze the geographical distribution of selected putative denitrifiers in the genus Sphingomonas, Mycoplana, Shewanella, and Alteromonas at different predicted environmental conditions and future climatic scenarios across the Baltic Sea. Using the predictive power of an ensemble modeling approach and eight different machine-learning algorithms, habitat suitability and the distribution of the selected denitrifiers were evaluated using geophysical and bioclimatic variables, benthic conditions, and four Representative Concentration Pathway (RCP) trajectories of future global warming scenarios. All algorithms provided successful prediction capabilities both for variable importance, and for habitat suitability with Area Under the Curve (AUC) values between 0.89 and 1.00. Model findings revealed that salinity and nitrate concentrations significantly explained the variation in distribution of the selected denitrifiers. Rising temperatures of 0.8 to 1.8 °C at future RCP60–2050 trajectories are predicted to diminish or eliminate the bioclimatic suitable habitats for denitrifier distributions across the Baltic Sea. Multi-collated terrestrial and marine environmental variables contributed to the successful prediction of denitrifier distributions within the study area. The correlative niche modeling approach with high AUC values presented in the study allowed for accurate projections of the future distributions of the selected denitrifiers. The modeling approach can be used to improve our understanding of how ongoing and predicted future environmental changes may affect habitat suitability for organisms with denitrification capacity across the Baltic Sea.

Denitrification in sediments is a key microbial process that removes excess fixed nitrogen, while dissimilatory nitrate reduction to ammonium (DNRA) converts nitrate to ammonium. Although microorganisms are responsible for essential nitrogen (N) cycling, it is not yet fully understood how these microbially mediated processes respond to toxic hydrophobic organic compounds (HOCs) and metals. In this study, we sampled long-term polluted sediment from the outer harbor of Oskarshamn (Baltic Sea), measured denitrification and DNRA rates, and analyzed taxonomic structure and N-cycling genes of microbial communities using metagenomics. Results showed that denitrification and DNRA rates were within the range of a national reference site and other unpolluted sites in the Baltic Sea, indicating that long-term pollution did not significantly affect these processes. Furthermore, our results indicate an adaptation to metal pollution by the N-cycling microbial community. These findings suggest that denitrification and DNRA rates are affected more by eutrophication and organic enrichment than by historic pollution of metals and organic contaminants.

Many factors affect the habitat selection for animal species, which in turn may greatly affect their distribution in different ecosystems. Understanding the processes that affect habitat selection is also critical for guiding and managing conservation initiatives. Our study aimed to assess the habitat selection by free-ranging Spiny-tailed lizard (Uromastyx aegyptia) by analyzing a geospatial data connecting its burrow parameters to different habitat characteristics within selected sites in Hail region, Saudi Arabia. We examined evidence and patterns of significant spatial clustering for (366) active burrows by linking their parameters (burrow entrance size, burrow entrance width and burrow entrance height), their reference geographical locations and, two habitat characteristics defined by soil type and vegetation cover. The objective of the analysis was to increase the understanding on the burrows aggregation process in the space and, to describe its possible relation to other spatial habitat configurations. Analysis of distances based on the Nearest Neighbor Index (NNI) and hotspots detection in Nearest neighbor hierarchical clustering (Nnh) suggested twelve (12) spatial clusters located within the study area. In addition, a spatial ordinary least square (OLS) and Poisson regression models revealed significant effects of soil type and vegetation cover on burrow parameters (OLS, p < 0.05; Poisson, p < 0.001), which indicate a strong association between burrows parameters and habitats characteristics. Findings from the study also suggest that other factors such as elevations, highways, and human settlement concentration spots could possibly play a major role in defining burrow spatial aggregation and furthermore have a significant impact on habitat selection.

This study was conducted to assess the phytodiversity distribution in relation to altitudinal gradient in Salma Mountains, a naturally protected habitat in Ha'il region in the north of Saudi Arabia. Seventeen (17) sampling sites covering three altitudinal zones (i.e. valley, foot and top mountain) were randomly selected within the study area. Within each site and altitudinal zone, the floristic composition and the potential plant species of economic values were assessed and evaluated. A total number of 163 plant species belong to 101 genera and 41 families were identified in this study. Their economic values were also classified into forage (32%), edible (8.7%), medicinal (21.3%), ornamental (30.7%), weeds (18%) and rare species (14%). In addition, results obtained from different altitudinal zones of Salma Mountains, showed that 24 species were spread in the adjacent valley to the mountains, where 32 species spreading at the foot of the mountains and 40 found occupying the top of the mountains. The rest of species have been found to occupy larger geographical distribution in all altitudinal parts. Across the altitudinal gradients, species richness has been found to be consistent with a monotonically increasing pattern with a high richness at high altitudes. The current study suggests that such naturally protected ecosystem can provide a refuge for native plant species and serve as seed bank for a future restoration program in Ha'il region and other similar habitats in Saudi Arabia.