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Seagrass habitats are ecologically valuable and play an important role in sequestering and storing carbon. There is, thus, a need to estimate seagrass percentage cover in diverse environments in support of climate change mitigation, marine spatial planning and coastal zone management. In situ approaches are accurate but time-consuming, expensive and may not represent the larger spatial units collected by satellite imaging. Hence, there is a need for a consistent methodology that uses accurate point-based field surveys to deliver high-quality mapping of percentage seagrass cover at large spatial scales. Here, we develop a three-step approach that combines in situ (quadrats), aerial (unoccupied aerial vehicle—UAV) and satellite data to map percentage seagrass cover at Turneffe Atoll, Belize, the largest atoll in the northern hemisphere. First, the optical bands of four UAV images were used to calculate seagrass cover, in combination with in situ data. The seagrass cover calculated from the UAV was then used to develop training and validation datasets to estimate seagrass cover in Sentinel-2 pixels. Next, non-seagrass areas were identified in the Sentinel-2 data and removed by object-based classification, followed by a pixel-based regression to calculate seagrass percentage cover. Using this approach, percentage seagrass cover was mapped using UAVs (R2 = 0.91 between observed and mapped distributions) and using Sentinel-2 data (R2 = 0.73). This work provides the first openly available and explorable map of seagrass percentage cover across Turneffe Atoll, where we estimate approximately 242 km2 of seagrass above 10% cover is located. We estimate that this approach offers 30 times more data for training satellite data than traditional methods, therefore presenting a substantial reduction in cost-per-point for data. Furthermore, the increase in data helps deliver a high-quality seagrass cover map, suitable for resolving trends of deteriorating, stable or recovering seagra

Accurate knowledge of the spatial extent of seagrass habitats is essential for monitoring and management purposes given their ecological and economic significance. Extent data are typically presented in binary (presence/absence) or arbitrary, semi-quantitative density bands derived from low-resolution satellite imagery, which cannot resolve fine-scale features and intra-habitat variability. Recent advances in consumer-grade unoccupied aerial vehicles (UAVs) have advanced our ability to survey large areas at higher resolution and at lower cost. This has improved the accessibility of mapping technologies to developing coastal nations, where a large proportion of the world’s seagrass habitats are found. Here, we present the application of UAV-gathered imagery to determine seagrass habitat extent and percent of canopy cover. Four contrasting sites were surveyed in the Turneffe Atoll Marine Reserve, Belize, and seagrass canopy cover was ground truthed from in situ quadrats. Orthomosaic images were created for each site from the UAV-gathered imagery. Three modelling techniques were tested to extrapolate the findings from quadrats to spatial information, producing binary (random forest) and canopy cover (random forest regression and beta regression) habitat maps. The most robust model (random forest regression) had an average absolute error of 6.8–11.9% (SE of 8.2–14), building upon previous attempts at mapping seagrass density from satellite imagery, which achieved errors between 15–20% approximately. The resulting maps exhibited great intra-habitat heterogeneity and different levels of patchiness, which were attributed to site energetics and, possibly, species composition. The extra information in the canopy cover maps provides greater detail and information for key management decisions and provides the basis for future spatial studies and monitoring programmes.

Land-ocean dissolved organic matter (DOM) transport is a significant and changing term in global biogeochemical cycles which is increasing as a result of human perturbation, including land-use change. Knowledge of the behavior and fate of transported DOM is lacking, particularly in the tropics and subtropics where land-use change is occurring rapidly. We used Parallel Factor (PARAFAC) Analysis to investigate how land-use influenced the composition of the DOM pool along a subtropical land-use gradient (from near-pristine broadleaf forest to agri-urban settings) in Belize, Central America. Three humic-like and two protein-like components were identified, each of which was present across land uses and environments. Land-use mapping identified a strong (R2 = 0.81) negative correlation between broadleaf forest and agri-urban land. All PARAFAC components were positively associated with agri-urban land-use classes (cropland, grassland, and/or urban land), indicating that land-use change from forested to agri-urban exerts influence on the composition of the DOM pool. Humic-like DOM exhibited linear accumulation with distance downstream and behaved conservatively in the coastal zone whilst protein-like DOM exhibited nonlinear accumulation within the main river and nonconservative mixing in coastal waters, indicative of differences in reactivity. We used a hydrodynamic model to explore the potential of conservative humics to reach the region's environmentally and economically valuable coral reefs. We find that offshore corals experience short exposures (10 ± 11 days yr−1) to large (∼120%) terrigenous DOM increases, whilst nearshore corals experience prolonged exposure (113 ± 24 days yr−1) to relatively small (∼30%) terrigenous DOM increases.

Benthic fauna form spatial patterns which are the result of both biotic and abiotic processes, which can be quantified with a range of landscape ecology descriptors. Fine- to medium-scale spatial patterns (<1–10 m) have seldom been quantified in deep-sea habitats, but can provide fundamental ecological insights into species’ niches and interactions. Cold-water coral reefs formed by Desmophyllum pertusum (syn. Lophelia pertusa) and Madrepora oculata are traditionally mapped and surveyed with multibeam echosounders and video transects, which limit the ability to achieve the resolution and/or coverage to undertake fine-scale, centimetric quantification of spatial patterns. However, photomosaics constructed from imagery collected with remotely operated vehicles (ROVs) are becoming a prevalent research tool and can reveal novel information at the scale of individual coral colonies. A survey using a downward facing camera mounted on a ROV traversed the Piddington Mound (Belgica Mound Province, NE Atlantic) in a lawnmower pattern in order to create 3D reconstructions of the reef with Structure-from-Motion techniques. Three high resolution orthorectified photomosaics and digital elevation models (DEM) >200 m2 were created and all organisms were geotagged in order to illustrate their point pattern. The pair correlation function was used to establish whether organisms demonstrated a clustered pattern (CP) at various scales. We further applied a point pattern modelling approach to identify four potential point patterns: complete spatial randomness (CSR), an inhomogeneous pattern influenced by environmental drivers, random clustered point pattern indicating biologically driven clustering and an inhomogeneous clustered point pattern driven by a combination of environmental drivers and biological effects. Reef framework presence and structural complexity determined inhabitant distribution with most organisms showing a departure from CSR. These CPs are likely caused by an affinity

Cold-water corals, like their shallow-water counterparts are capable of forming reef habitats that are important for their local environment. Cold-water corals are under increasing anthropogenic pressure and thus, the need to map their occurrence and understand their fundamental ecological role is essential in order to plan effective conservation measures. Cold-water coral reefs promote biodiversity with the introduction of structural complexity and substrate heterogeneity. Whilst the role of structural complexity is important and is a key criterion of Vulnerable Marine Ecosystem designation, we typically lack high-resolution data that can quantify such metrics. Ship-borne multibeam echosounder (MBES) data is typically low resolution, missing vital geomorphological features and the detailed video coverage is minimal in comparison. This results in Ill-matched datasets for mapping coral extent through predictive mapping and insufficient resolution to quantify cold-water coral reef structural complexity. We deployed an Autonomous Underwater Vehicle to collect high-resolution MBES data and Remotely Operated Vehicles to collect images for Structure from Motion (SfM) to bridge the gaps in data resolution and undertake novel fine-scale investigations. The results in this thesis show that by resolving fine-scale geomorphological features with high-resolution bathymetry, additional locations suitable for cold-water coral growth can be identified. The results further highlighted the importance of vertical walls in Explorer Canyon, NE Atlantic, as a habitat for cold-water coral. This thesis also demonstrates how SfM can be used to quantify cold-water coral structural complexity. Cold-water coral reef in Explorer Canyon introduces significant structural complexity on a centimetric scale, promoting local biodiversity and providing a distinct cold-water coral habitat when coral coverage was greater than 30%. Further investigations reveal that cold-water coral associated taxa are

Benthic fauna form spatial patterns which are the result of both biotic and abiotic processes, which can be quantified with a range of landscape ecology descriptors. Fine- to medium-scale spatial patterns (<1–10 m) have seldom been quantified in deep-sea habitats, but can provide fundamental ecological insights into species’ niches and interactions. Cold-water coral reefs formed by Desmophyllum pertusum (syn. Lophelia pertusa) and Madrepora oculata are traditionally mapped and surveyed with multibeam echosounders and video transects, which limit the ability to achieve the resolution and/or coverage to undertake fine-scale, centimetric quantification of spatial patterns. However, photomosaics constructed from imagery collected with remotely operated vehicles (ROVs) are becoming a prevalent research tool and can reveal novel information at the scale of individual coral colonies. A survey using a downward facing camera mounted on a ROV traversed the Piddington Mound (Belgica Mound Province, NE Atlantic) in a lawnmower pattern in order to create 3D reconstructions of the reef with Structure-from-Motion techniques. Three high resolution orthorectified photomosaics and digital elevation models (DEM) >200 m2 were created and all organisms were geotagged in order to illustrate their point pattern. The pair correlation function was used to establish whether organisms demonstrated a clustered pattern (CP) at various scales. We further applied a point pattern modelling approach to identify four potential point patterns: complete spatial randomness (CSR), an inhomogeneous pattern influenced by environmental drivers, random clustered point pattern indicating biologically driven clustering and an inhomogeneous clustered point pattern driven by a combination of environmental drivers and biological effects. Reef framework presence and structural complexity determined inhabitant distribution with most organisms showing a departure from CSR. These CPs are likely caused by an affinity

© 2020 Elsevier B.V. The identification and correlation of a sequence of Pleistocene beach barriers located within the northern Coorong Coastal Plain, South Australia, is made difficult by long-term subsidence and extensive reworking. Associated shell beds, to all but the last interglacial barrier, are subsurface and not readily accessible. The whole-rock amino acid racemization method was found to be unsuitable for distinguishing age differences of the individual barriers due to the low calcium carbonate content of the sediments, concerns for the leaching or contamination as a result of the comminuted nature of the shelly component, and the potentially high content of reworked sediment. These difficulties prompted an investigation into the applicability of AAR analysis of single foraminifera tests to ascertain whether the relative age of beach barriers could be determined and whether sediment contribution from antecedent barriers could be identified. Foraminifera tests of multiple genera (including Cibicides corticatus and Rosalina bradyi) from numerous modern depositional environments were analyzed to establish aminozones of aspartic acid and glutamic acid D/L values representative of modern/Holocene foraminifera and to assess natural variability of Holocene D/L values between depositional settings. Tests of Lamellodiscorbis dimidiatus, common in the Pleistocene barriers, were analyzed from MIS 5 and MIS 7 sediments and aminozones identified, allowing correlation of non-contiguous barrier features and the identification of reworked foraminifera. Rejection criteria removed, on average, between 25 and 30% of analytical results. The Holocene aminozone for every genus analyzed falls within the same general constraint: D/L values less than 0.40 for aspartic acid and less than 0.20 for glutamic acid. The D/L values of approximately 15% of foraminifera from the modern sediments exceed the Holocene aminozone constraint and the tests are considered reworked. The range of D

2020 Elsevier B.V. Progradation of the Quaternary Gilbert River megafan and Holocene delta, located in the low gradient intracratonic basin and epeiric sea of the Gulf of Carpentaria, Australia, has been enhanced by the slight fall in sea level during the late Holocene. The monsoonal floods and channel avulsions on the megafan have controlled the rate of progradation and supply of sediment to the delta front. The mixed-influence delta can be classified as a tide dominated, fluvially influenced and wave affected (Tfw) delta. Palaeogeographic reconstruction of the Gilbert River megafan, delta and palaeoshorelines was created through GIS analysis of beach and chenier ridges combined with field observations, previous cross-section data, and radiocarbon and thermoluminescence dating. Progradation rates on the Gilbert River delta are about 0.85 to 0.9 m/yr in the northern and central parts of the delta and increase to 1.8 m/yr in the southern part of the delta. Sedimentation rates vary from 0.2 to 1.0 mm/yr with a total Holocene delta volume of about 9.4 x 109 m3 and a sediment supply rate of ~1 Mm3/yr. The low sediment supply rate is characteristic of most Australian river systems but is about two orders of magnitude less than on many of the larger Southeast Asian deltas. The low onshore and offshore accommodation space on the Gilbert and Mitchell River deltas is a function of the epeiric sea setting of these deltas, and hence the thin succession of Holocene sediments on these deltas also represent a significant difference from most Southeast Asian deltas.