A high-resolution operational forecast system for oil spill response in Belfast Lough

This paper presents a high-resolution operational forecast system for providing support to oil spill response in Belfast Lough. The system comprises an operational oceanographic module coupled to an oil spill forecast module that is integrated in a user-friendly web application. The oceanographic module is based on Delft3D model which uses daily boundary conditions and meteorological forcing obtained from COPERNICUS and from the UK Meteorological Office. Downscaled currents and meteorological forecasts are used to provide short-term oil spill fate and trajectory predictions at local scales. Both components of the system are calibrated and validated with observational data, including ADCP data, sea level, temperature and salinity measurements and drifting buoys released in the study area. The transport model is calibrated using a novel methodology to obtain the model coefficients that optimize the numerical simulations. The results obtained show the good performance of the system and its capability for oil spill forecast.     

Understanding the culture of natural disaster preparedness: exploring the effect of experience and sociodemographic predictors

Natural Hazards - Understanding the culture of preparedness is essential to improve public policies and programs aimed to promote population preparedness to cope with natural hazards. The present...     

Assessing drought in the drylands of northeast Brazil under regional warming exceeding 4 °C

Natural Hazards - Historically, during periods of extreme drought, food security in the drylands of the semiarid region of Northeast Brazil (NEB) is under severe risk due to agricultural collapse....     

Effects of urban wastewater on crab and mollusc assemblages in equatorial and subtropical mangroves of East Africa

Mangrove forests are known to accomplish crucial ecosystem functions and services. They are nursery areas for fish, prawns and crabs, which provide coastal communities with a variety of food, timber and chemicals, and protect coasts from catastrophic events, such as tsunamis. Recently, a novel ecological service has been proposed for mangrove systems, namely natural wastewater treatment wetlands. This hypothesis was based on experimental data collected mainly in Chinese mangrove systems, which proved that mangrove soils were efficient in absorbing nutrients. Moreover, sewage loading seemed harmless to both plants and benthic communities in these systems. However, before promoting the use of natural mangroves as pollution buffers, or constructed mangrove wetlands as sewage treatment facilities, more data are needed on their overall tolerance to organic loading. Differences in macrobenthos patterns were thus investigated between peri-urban mangroves and sites not affected by sewage disposal in East Africa. We assessed differences in epifaunal assemblages, comprising crabs and molluscs, employing multivariate ACI unbalanced analyses to compare peri-urban mangrove swamps with those characteristic of non-urban mangroves with similar ecological traits. The sampling design was spatially nested, replicates being assessed at equatorial (southern Kenya) and subtropical (southern Mozambique) sites. The results manifested a consistent increase in crab biomass at the peri-urban sites in both Kenya and Mozambique. Moreover, the peri-urban systems were richer than the non-urban mangroves, both in terms of fiddler crabs (Uca spp.) which feed on benthic microalgae and bacteria, and sesarmids, such as Perisesarma guttatum and Neosarmatium meinerti, which feed on both substratum and leaf litter. The abundance of gastropods, in contrast, decreased significantly, especially in Kenya, mainly due to the disappearance of the mud whelk Terebralia palustris. The results thus indicate that, in East African mangrove systems, domestic wastewater has detectable effects on crabs and molluscs, suggesting their usefulness as bioindicators of its effects in mangroves. Transformed benthic patterns at the peri-urban sites indicated the need for further study of the actual potential of natural mangrove forests to absorb pollution in sewage treatment.     

Population structure, density and food sources of Terebralia palustris (Potamididae: Gastropoda) in a low intertidal Avicennia marina mangrove stand (Inhaca Island, Mozambique)

Population structure and distribution of Terebralia palustris were compared with the environmental parameters within microhabitats in a monospecific stand of Avicennia marina in southern Mozambique. Stable carbon and nitrogen isotope analyses of T. palustris and potential food sources (leaves, pneumatophore epiphytes, and surface sediments) were examined to establish the feeding preferences of T. palustris. Stable isotope signatures of individuals of different size classes and from different microhabitats were compared with local food sources. Samples of surface sediments 2.5–10 m apart showed some variation (−21.2‰ to −23.0‰) in δ¹³C, probably due to different contributions from seagrasses, microalgae and mangrove leaves, while δ¹⁵N values varied between 8.7‰ and 15.8‰, indicating that there is a very high variability within a small-scale microcosm. Stable isotope signatures differed significantly between the T. palustris size classes and between individuals of the same size class, collected in different microhabitats. Results also suggested that smaller individuals feed on sediment, selecting mainly benthic microalgae, while larger individuals feed on sediment, epiphytes and mangrove leaves. Correlations were found between environmental parameters and gastropod population structure and distribution vs. the feeding preferences of individuals of different size classes and in different microhabitats. While organic content and the abundance of leaves were parameters that correlated best with the total density of gastropods (>85%), the abundance of pneumatophores and leaves, as well as grain size, correlated better with the gastropod size distribution (>65%). Young individuals (height < 3 cm) occur predominantly in microhabitats characterized by a low density of leaf litter and pneumatophores, reduced organic matter and larger grain size, these being characteristic of lower intertidal open areas that favour benthic microalgal growth. With increasing shell height, T. palustris individuals start occupying microhabitats nearer the mangrove trees characterized by large densities of pneumatophores and litter, as well as sediments of smaller grain size, leading to higher organic matter availability in the sediment.     

Swimming abilities of wild-caught,late-stage larvae of Diplodus capensis and Sarpa salpa (Pisces: Sparidae) from temperate South Africa

Understanding the movement of marine fish larvae in coastal habitats requires an assessment of active swimming abilities. The critical speed (U-crit) and endurance swimming of late-stage larvae of Diplodus capensis and Sarpa salpa (Family Sparidae), common inshore recreational linefish species, were measured in a laboratory swimming chamber. Postflexion and settlement-stage larvae were collected from the wild in a small bay on the warm temperate coast of South Africa. Larvae were allowed to acclimate in captivity and were tested soon after capture. For the endurance tests a speed of 18 cm s⁻¹ was selected, as this approximated the mean current speed observed in the coastal environment of the area. The mean U-crit value (maximum swimming speed) for D. capensis (19 cm s⁻¹) was similar to that of S. salpa (18 cm s⁻¹), and similarly mean endurance (km swum) for S. salpa (8 km) was similar to that of D. capensis (6 km). The increase in critical speed and endurance swimming abilities with standard length was best described by a linear relationship. At lengths between 12 and 15 mm BL, D. capensis was the better swimmer, whereas S. salpa was the better swimmer between 15 and 16 mm BL. Of all the larvae that swam at critical speed, 90% were in an inertial environment. These swimming speeds exceed the modal current velocities observed in the shallow nearshore of the study region where these larvae occur abundantly. These swimming abilities provide larvae with the potential to influence their dispersal trajectories and ultimately influence their distribution in their nearshore nursery areas.     

Exhumed hydrocarbon traps on the North Atlantic margin: Stratigraphy,palaeontology, provenance and bitumen distribution,an integrated approach

Previous work has demonstrated the presence of a number of exhumed hydrocarbon traps in central East Greenland. Re-evaluation of the stratigraphy alongside detailed investigation of the occurrence of bitumen within the Mols Bjerge and Laplace Bjerg exhumed hydrocarbon traps provides new perspectives on these structures, as well as the petroleum geology of East Greenland and the wider North Atlantic. Sedimentological and stratigraphic studies, augmented with palynological and provenance investigations, have constrained the dating and correlation of the strata exposed in the Mols Bjerge and Laplace Bjerg. Petrographic analysis, alongside analysis of the bitumen identified, has highlighted a much wider distribution of hydrocarbon than previously recognized. It was previously considered that Jurassic strata formed the main reservoir interval within the Mols Bjerge and Laplace Bjerg exhumed hydrocarbon traps. It is shown here that the reservoir intervals in the Laplace Bjerg trap lie within the Late Triassic Ørsted Dal and Vega Sund members, which contain up to 18% pyrobitumen and were previously misidentified as Jurassic. The Jurassic Bristol Elv Formation is the most extensively bitumen stained unit in the Mols Bjerge trap. However, occurrences of pyrobitumen (up to 3%) are recorded throughout the Triassic stratigraphy, including the Early Triassic Wordie Creek Formation. Faults, thick calcrete development and regionally continuous mudstone units play an important role in compartmentalizing the palaeohydrocarbon accumulations.     

The impact of lateral boundary data errors on the simulated climate of a nested regional climate model

In this study, we investigate the response of a Regional Climate Model (RCM) to errors in the atmospheric data used as lateral boundary conditions (LBCs) using a perfect-model framework nick-named the “Big-Brother Experiment” (BBE). The BBE has been designed to evaluate the errors due to the nesting process excluding other model errors. First, a high-resolution (45 km) RCM simulation is made over a large domain. This simulation, called the Perfect Big Brother (PBB), is driven by the National Centres for Environmental Prediction (NCEP) reanalyses; it serves as reference virtual-reality climate to which other RCM runs will be compared. Next, errors of adjustable magnitude are introduced by performing RCM simulations with increasingly larger domains at lower horizontal resolution (90 km mesh). Such simulations with errors typical of today’s Coupled General Circulation Models (CGCM) are called the Imperfect Big-Brother (IBB) simulations. After removing small scales in order to achieve low-resolution typical of today’s CGCMs, they are used as LBCs for driving smaller domain high-resolution RCM runs; these small-domain high-resolution simulations are called Little-Brother (LB) simulations. The difference between the climate statistics of the IBB and those of PBB simulations mimic errors of the driving model. The comparison of climate statistics of the LB to those of the PBB provides an estimate of the errors resulting solely from nesting with imperfect LBCs. The simulations are performed over the East Coast of North America using the Canadian RCM, for five consecutive February months (from 1990 to 1994). It is found that the errors contained in the large scales of the IBB driving data are transmitted to and reproduced with little changes by the LB. In general, the LB restores a great part of the IBB small-scale errors, even if they do not take part in the nesting process. The small scales are seen to improve slightly in regions with important orographic forcing due to the finer resolution of the RCM. However, when the large scales of the driving model have errors, the small scales developed by the LB have errors as well, suggesting that the large scales precondition the small scales. In order to obtain correct small scales, it is necessary to provide the accurate large-scale circulation at the lateral boundary of the RCM.     

Predicting significant wave height with artificial neural networks in the South Atlantic Ocean: a hybrid approach

Ocean Dynamics - Accurate simulations of significant wave height (Hs) are extremely important for the safety of navigation, port operations, and oil and gas exploration. Thus, accurate forecasts of...     

Fatty acids dynamics during embryonic development in genus Uca (Brachyura: Ocypodidae), from the mangroves of Inhaca Island,Mozambique

Variations in egg volume and fatty acid (FA) content through embryogenesis were evaluated in Uca species from Inhaca island, Mozambique. Egg volume increased 96.1%, 93.3%, 84.2%, 92.9%, 96.3%, respectively, in Uca annulipes, Uca inversa, Uca urvillei, Uca chlorophthalmus and Uca vocans (p < 0.05). Fatty acid content decreased through embryogenesis, showing its importance as fuel during embryonic development. Major fatty acids were 16:0, 18:0, 16:1n-7, 18:1n-9, 18:1n-7, 18:2n-6, 20:5n-3 and 20:4n-3. Unsaturated fatty acids (UFA) and saturated fatty acids (SFA) were used up at a similar rate for U. annulipes and U. inversa contrarily to the other three species. Within the UFA, MUFA were more consumed than PUFA for all species except U. chlorophthalmus. The high values detected for fatty acid trophic markers (essential C₁₈ and C₂₀ PUFAs) and odd-numbered fatty acid suggest that Uca species occupy medium trophic level, primarily omnivores and scavengers/detritivores consuming algae common in the intertidal habitats. The fatty acid consumption pattern during embryonic development was essentially similar between species with some variation as expected, as FA content varies within species mainly due to female feeding ecology, nutritional and physiological conditions, differential demands on resource allocation and geographic and seasonal variations in embryonic development.