The capacity of the world’s coastal ecosystems to sequester carbon dioxide (CO2), termed “Blue Carbon,” has been a major focus of research in recent decades due to its potential to mitigate climate change. Vegetated coastal ecosystems such as mangroves, seagrass beds, and salt marshes represent a global area that is one to two orders of magnitude smaller than that of terrestrial forests, yet their contribution to long-term carbon sequestration is much greater per unit-area, in part because of their high productivity and efficiency in trapping suspended matter and associated organic carbon. Despite the value that Blue Carbon (BC) systems offer in sequestering carbon, as well as providing numerous other goods and services, these habitats are being lost at critical rates and require urgent action in order to prevent further degradation and loss. Recognition of the carbon sequestration value of vegetated coastal ecosystems provides a strong argument for their protection and restoration, and global efforts are now underway to include BC ecosystems into global carbon offset budgets, focusing on their optimal management to optimize CO2 sequestration and minimize CO2 emissions. Here, BC was investigated in the Cowichan Estuary in relation to habitat type (salt marsh, eelgrass meadow, non-vegetated mudflats, and oyster shell beds), and habitat degradation. Stored organic carbon (OC) and inorganic carbon (IC) were quantified in the top 20 cm depth of sediment cores, as well as in eelgrass and salt marsh vegetation, and then extrapolated to the areal extent of each habitat type based on a high resolution 1:12,000 scale base map of the estuary. Rates of sedimentation and carbon sequestration were quantified in each habitat type using 210Pb radiometric dating, and organic matter (OM) sources and quality were assessed in each habitat type using δ13C, C/N ratios and photopigment content in the sediments. A particular focus on the lower intertidal zone allowed us to examine the potential impact of industrial activity (log transport and storage) on the estuary’s capacity for carbon storage, as a result of a reduction of suitable habitat for eelgrass and microphytobenthos (MPB). Additionally, IC was quantified in aboveground oyster shell beds and buried oyster shell to assess inorganic storage. Finally, potential valuation of Blue Carbon in the Cowichan Estuary was investigated by comparing carbon sequestration to provincial greenhouse gas (GHG) emission equivalents as well as carbon sequestration in B.C. forests. We found that the salt marsh was the most important carbon reservoir, with a mean per-hectare sediment organic carbon (SOC) stock of 49.1 ± 19.9 Mg C ha-1, total ecosystem carbon stock (TECS) of 5443.75 Mg C, and carbon accumulation rate of 74 ± 23 g C m-2 yr-1. In the other habitats, we found SOC stocks and TECS respectively 19.1 ± 3.78 Mg C ha-1 and 3651.6 ± 72.3 Mg C in the upper mudflats, 16.9 ± 4.36 Mg C ha-1 and 1058.85 Mg C in the lower mudflats, 17.9 ± 1.21 Mg C ha−1 and 324.57 Mg C in the eelgrass meadow, and 9.43 ± 1.50 Mg C ha-1 and 59.4 Mg C in the oyster beds. The eelgrass meadow had a carbon accumulation rate of 38 ± 26 g C m-2 yr-1, while the mudflats could not successfully be dated due to erosion and/or mixing. Furthermore, the salt marsh contained the highest proportion of recalcitrant, terrestrial-derived root material which was more protected from hydrodynamic forces compared to other habitats. No pattern differences were observed between the carbon reservoirs or bulk properties of the log boom area (lower mudflat) compared to the upper mudflat, and thus there was no evidence that the log booms significantly decrease carbon sequestration in the areas where they make frequent contact with the seafloor. However, decreased chlorophyll a (chl a) concentrations in the lower mudflat sediment suggests a possible detrimental impact on microphytobenthos in addition to preventing the recolonization of the seagrass Zostera marina (Z. marina). Carbon stocks in the eelgrass meadow were similar to those of the mudflats. These carbon stocks were lower than global averages but consistent with those recently reported in low Z. marina meadows in the Pacific Northwest. Evidence of significant eelgrass vegetation outwelling necessitates further investigation to elucidate the degree to which these primary products are being decomposed or buried elsewhere in the estuary or open ocean. Since approximately half of the historical salt marsh habitat is currently reclaimed for agricultural and industrial use, consideration should be given to the role of the marsh system as a carbon reservoir in future land-use policy in the Cowichan Estuary. / Graduate / 2022-04-30

Seagrasses are well known for the important ecological roles they play in coastal marine waters worldwide. However, the severe rate of decline observed in seagrasses this century is expected to accelerate with climate change. Conservation efforts can be improved by quantifying physiological thresholds of seagrasses and using these estimates in modeling to forecast changes in distribution. This study examines the response of eelgrass (Zostera marina L.) across current temperatures to look for early warning signs of vulnerability and to evaluate the ways we determine critical thresholds for survival. Whole eelgrass ramets, collected from three beds in Morro Bay, California, were used to develop photosynthesis-irradiance (P-I) curves from 10-20°C. Productivity was not affected by changes in temperature when traditionally measured as the light-saturated photosynthetic rate to dark respiration rate (P:R) ratio. However, photosynthesis in light-limited conditions declined at higher temperatures, suggesting a decrease in productivity when coupled with the increased respiration rates observed at higher temperatures. Irradiance thresholds increased with temperature; critical irradiance was the most sensitive to increases in temperature due to the inclusion of overnight energy use, which also increases with temperature. Measurements of root and rhizome respiration, overnight respiration, and variation across eelgrass beds reveal that these are important components to consider when calculating survival thresholds to use in modeling. Differences in physiological responses across beds suggest that some eelgrass beds operate more efficiently than others in current conditions and are likely to be more resilient to the progressing stressors of climate change. Management of eelgrass in the face of climate change will require reliable distribution forecasts, and therefore accurate estimates of physiological thresholds, to guide mitigation and restoration efforts.

Seagrasses are ecosystem engineers, forming extensive meadows that provide critical habitat and modulate local morphodynamics. Their canopies induce drag on flow to attenuate mean flow and reduce near-bed flow velocities, which can shield the bed from erosion and sediment suspension. Alternatively, seagrass loss can enhance erosion and sediment suspension, which can be initiated through short-lived extreme events, or chronic long-term disturbances. Physical process and disturbances can govern the evolution of seagrass meadow ecosystems. In two separate chapters, this research examined 1) the influence of climate variability and storms on seagrass loss and erosion at a high spatial resolution, and 2) how flow attenuation by seagrass varies across tidal cycles and at different locations in the Choked Passage meadow, on the Central Coast of British Columbia. We used high resolution multibeam echosounder (MBES) bathymetry and backscatter data from 2018 to 2021, drone mapped seagrass delineations from 2014 to 2021, and wind and wave data from 2014 to 2021. Flow data (i.e. velocity magnitude, velocity direction, and acoustic backscatter) above the seagrass canopy was collected with an Acoustic Doppler Current Profiler (ADCP) along transects and moored to the seafloor over a tidal cycle. Sediment samples were collected from the bed to estimate critical shear stress and verify sediment classes from an acoustic backscatter analysis. From 2018 to 2021, the meadow experienced significant erosion (net surface lowering of -18,768 m3) and loss of seagrass (10% reduction), which we attribute to the preceding winter storm activity driven by moderate La Niña conditions. The spatial patterns of erosion and seagrass loss was non-uniform across the meadow. Coupled erosion and seagrass loss resulted in the generation and/or expansion of blowouts. We observed a trend of a reduction in seagrass coverage following winters with a high number of storm events and/or high recorded storm intensity from 2014 to 2021. We believe the Choked Passage seagrass meadow undergoes cyclic behaviour with reduction in seagrass coverage during energetic ENSO years, followed by a recovery period during weak years. The ADCP was used to detect the seagrass canopy height, measure flow, and estimate shear stress. Overall, flow is fastest in the northern section of the main meadow, particularly in the north-west corner where the meadow is patchy. Moreover, flow appears to accelerate through the meadow interior, which suggests that topographic steering and the strength of incoming currents exceeds the ability of seagrass to dampen flow velocity. During the transition from peak flood to ebb, flow velocity remained heightened for longer above the southern meadow and lagged the other sections. Shear stress results indicate that sediment can be transported as bedload and in suspension under peak flow velocities at some of the sites examined within the meadow. Shear stress is largest in the meadow center and lower towards the southern margin of the main meadow. Based on our results, when sediment transport is initiated under peak tidal and/or extreme conditions, sediment is likely primarily transported as bedload, creating the observed sand wave and blowout bedforms. This research demonstrated linkages between extreme storms (during ENSO years), seabed morphology, and seagrass coverage, and examined the variability in the interaction between flow, seagrass, and sediment transport. Geomorphic processes and disturbances have an important influence on ecosystem structure and function over time, therefore, it is important to understand how these processes operate and are modified by external drivers. The results of this study have significant implications on seagrass conservation, restoration, and the evolution of coastal landscapes. / Graduate

No description available.

Ålgräs fungerar som ekosystemingenjörer som förser både människan och naturen med en mängd viktiga ekosystemtjänster och tillhandahåller olika ekosystemfunktioner. Ålgräsängens vegetation skapar en fysisk struktur till den annars kala, mjuka ler- eller sandbottnen och ökar den biologiska mångfalden. En annan viktig funktion som ålgräsängar skapar är habitat som fungerar som barnkammare för olika fiskarter, såsom torsk, flundror och sej. Det uppskattas att cirka 30% av de kända arealerna av ålgräsängar har försvunnit globalt och att 7% försvinner årligen. I Sverige kan liknande historiska förluster av ålgräs visas, bara i Bohuslän har 60% försvunnit sedan 1980-talet och ålgräsängarna fortsätter att minska till följd av fortsatt exploatering av kustområden. I detta projekt har vi undersökt ålgräsets förmåga till etablering samt dess tillväxt efter förflyttning och omplantering i ett nytt habitat vid Hallands kust. Plantering av ålgräs har inte tidigare gjorts i Halland och syftet med denna studie var att se om plantering var möjligt och hur stor tillväxt det sker på blad samt antal nya tillväxande vegetativa skott.Våra resultat visade att det fanns signifikanta skillnader för ålgräsets överlevnad mellan de tre olika metoder som vi utförde vid plantering. Vår metod singelskottsmetoden visade sig vara mest lyckad vid platsen, som låg på ett område med relativt hög våg- och vindexponering, vilket vi anser är typiskt för den Halländska kusten. De andra två metoderna, nätmetoden samt grillspettsmetoden, som användes inkluderade förankring av plantorna vilket resulterade i sämre överlevnad. Detta kan ha berott på att det fanns flera stressfaktorer vid platsen som vågor, vind och algpåväxt och att förankring störde ålgräsets etablering. / Eelgrass act as ecosystem engineers, providing both humans and nature with a variety of important ecosystem services and providing various ecosystem functions. The vegetation that eelgrass beds provide is a physical structure to the otherwise bare, soft clay or sand seabed and increases biodiversity. Another important function that eelgrass beds provide is that they create habitats that act as nurseries for various fish species, such as cod, flounder and pollock. It is estimated that around 30% of the known areas of eelgrass meadows have disappeared globally and that 7% is decreasing annually. In Sweden, similar historical losses of eelgrass can be seen, only in Bohuslän, 60% has disappeared since the 1980s and continues to decrease as a result of continued exploitation of coastal areas.  In this project, we have investigated the ability of eelgrass to establish as well as its growth after relocation and replanting in a new habitat on the coast of Halland. Planting of eelgrass has not previously been done in Halland, so the purpose of this study was to see if this was possible and how much growth occurs on leaves and the amount of new growing vegetative shoots. Our results showed that there were significant differences in the survival of the eelgrass between the three different methods we used when planting. Our method the single-shoot method proved to be most successful at the site, which was in an area with relatively high wave and wind exposure, which we believe is typical for the coast of Halland. The other two methods used, the netmethod and skewermethod, included anchoring the plants which resulted in poorer survival. This may have been because there were several stress factors at the site such as waves, wind and algae growth and that anchoring disturbed the establishment of the eelgrass.

ix, 60 leaves : maps ; 28 cm Notes Typescript Thesis (M.S.)--University of Oregon, 1983 Includes vita and abstract Bibliography: leaves 56-60 Another copy on microfilm is located in Archives

x, 62 leaves : ill. ; 29 cm Notes Typescript Thesis (M.S.)--University of Oregon, 1987 Includes vita and abstract Bibliography: leaves 54-62 Another copy on microfilm is located in Archives

The most common eelgrass along the Swedish coast is Zostera marina. It is an ecosystem engineer which provides both nature and humans with important ecosystem services and various ecosystem functions. Eutrophication is one of the main reasons why the Swedish coast has lost a lot of Z. marina meadows. When there is more nitrogen in the ocean, it is an advantage for epiphytic algae so that they can grow faster. The epiphytic algae grow on Z. marina and reduce Z. marina from receiving light. And therefore, the aim of my thesis is to investigate the effect of eutrophication on the growth of epiphytic algae on Z. marina. I took water samples at 8 different locations (spanning 7.21 km) along the coast of Halmstad, from the mouth of river Nissan, which I hypothesize to be a main source of nitrogen, to the open sea. From the water samples nitrogen, absorbance and TOC was measured to see if there was any difference in the water composition from Nissan's outlet and seawards. Z. marina leaves were taken from two different sites on one occasion to investigate the degree of epiphytic algae on the leaves. I found that the nitrogen concentration was decreasing from the outlet of Nissan River along coast towards the open sea. Also, the growth of epiphytic algae on Z. marina was decreasing from the outlet of Nissan River along the coast towards the open sea. The growth of epiphytic algae on Z. marina was not solely dependent of the concentration of nitrogen. In Scandinavia, Z. marina meadows are one of the most diverse coastal ecosystems. On otherwise sandy and species-poor substrates, Z. marina is an important habitat for a rich epiflora and fauna so a more integrated understanding in both management and science of Z. marina's stress responses is needed.

In this thesis I review how Sargassum muticum (Yendo) Fensholt, an invasive alga from Asia, has spread globally due to human activities and describe how this species can affect seagrass ecosystems. Abiotic factors such as nutrient and substratum availability may facilitate the spread of S. muticum into Zostera marina L. meadows, but analyses of seawater nutrients, and sediment particle size and % organic content revealed no significant differences between experimental quadrats in seagrass meadows either with, or without the presence of S. muticum. Phenolic compounds were examined because they form the basis of defensive mechanisms in plants and algae, therefore any change in phenolic content may affect the ability of Z. marina to protect itself from disease, herbivory and invasive species through allelopathic interactions. Results from a four year field study and multiple annual laboratory experiments showed significant reductions (p = 0.034 and p = 0.002, respectively) in the caffeic and tannic acids equivalents content of Z. marina when in the presence of S. muticum. As the abundance of S. muticum increases, other changes in the physiology of Z. marina may occur including variations in growth rates, nutrient partitioning and chlorophyll fluorescence, but data from multiple laboratory experiments illustrated no significant differences in growth. Chlorophyll fluorescence analyses revealed significant differences between treatments with and without S. muticum (p = 0.008), but pairwise comparisons indicated these differences only occurred in 2008 (p < 0.001). Significant differences were also found in nutrient partitioning amongst functional regions of the shoots (p = 0.024), but pairwise comparisons detected these differences between a biomass control treatment (ZZ: Zostera + Zostera) and the ZS (with S. muticum) and ZM (Z. marina on its own at a lower biomass per replicate) treatments (p = 0.013 and p = 0.019, respectively), but not between ZS and ZM. Previous in situ research has found negative effects of S. muticum presence on densities of kelp and other algae. Results from the long-term field study indicated significantly lower mean in situ Z. marina densities within the ZS treatment (p < 0.001). Epibiota found living on the blades of Z. marina provide food for organisms within seagrass ecosystems and also create microhabitats for other species to occupy. Alterations in the abundances of epibiota and microhabitats formed could further modify seagrass ecosystems through shifts in timing of food availability, food preferences and microhabitats created. The long-term field study data revealed significantly lower epibiota abundances within the ZS treatment (p = 0.019), but differences in biomass between treatments were not detected. Changes in the biochemistry, physiology, vegetative physiognomy and epibiota assemblages of Z. marina revealed during experimental manipulations are presented and considered within the context of long-term seagrass survival in light of increasing S. muticum invasion.

Coastlines are particularly susceptible to the necessary trade-offs which occur between different ecosystem services. Should the areas be managed for biodiversity or for people? Where sandy beaches are found there is usually a management decision to be made between managing for recreation or for biodiversity. Many popular tourist beaches (particularly those with a Beach Award) are often groomed with mechanical equipment to remove any stranded seaweed and associated litter which can get entangled in the wrack. This is likely to be having a negative impact on coastal biodiversity, with wide ranging implications for the entire habitat, including the intertidal zone, sand dunes and shorebirds. Beached wrack should be allowed to naturally decompose providing a habitat for numerous species of macro-invertebrates. These macro-invertebrate communities not only include many endemic species found exclusively along the strandline but they also provide a very rich source of food for shorebirds. The re-mineralised nutrients resulting from the decomposed macrophytes should then become available to provide a rich source of nutrients to dune, strandline and marine ecosystems populations of the strandline. In previous studies grooming has been shown to have a negative impact on the invertebrates of the strandline and this study reveals that tidal range has an effect on the impacts of grooming with a higher tidal range having a more negative impact on the invertebrates. A study to observe the impacts of grooming on both adult plant and seed bank communities of the sand dunes found that grooming is having a negative impact on these populations. Grooming is predominantly driven by beach managers who aspire to gain Beach Awards in order to attract tourists to their beaches. Using non-market valuation in the form of a stated preference choice experiment and a travel cost model, it was observed that Beach Awards are not valued by beach goers but are instead influenced to visit a particular beach by good bathing water quality, high levels of biodiversity and low levels of litter. It was also shown that stranded seaweed on the beach does not deter visitors. Future management suggestions include attempting to reduce the confusion arising from the presence of multiple beach awards by either removing them altogether or by making their criteria more clear and direct with consistency in their design and designation. Bathing water quality should be completely removed from the Beach Award system and real-time information in the form of electronic signage and a publicly available App should replace it.