Morpho-stratigraphic characterization of the southern shelf of Porto Santo Island (Madeira Archipelago): Insights for small-scale instability processes and post-LGM sedimentary architecture

Innocentini, Simone; Quartau, Rui; Casalbore, Daniele; Roque, Cristina; Vinhas, André; Santos, Rúben; Rodrigues, Armanda

doi:10.1016/j.margeo.2021.106729

Cited by 7 publications

(10 citation statements)

References 63 publications

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Section: Methodsmentioning

confidence: 99%

“…This island has a semi‐arid climate, with a mean annual precipitation of 360 mm. Consequently, it lacks permanent streams (Innocentini et al, 2022). The island's drainage network is characterised by torrential flows in winter, but the beds are dry or almost dry during the rest of the year (Gil, 2015).…”

Section: Methodsmentioning

confidence: 99%

“…Located 42 km northeast of Madeira, Porto Santo is the second largest inhabited island (42 km 2 ), with around 14 km in length and 6 km in width (Innocentini et al, 2022). This island has a semi-arid climate, F I G U R E 1 (a) European eel spawning area in the Sargasso Sea, main ocean currents related to larvae migration (Gulf Stream (GS), North Atlantic (NA), Azores (A), Canary (C), Norwegian (N) and North Equatorial (NE) currents) towards recruitment areas in inland waters of Europe, North Africa and Atlantic islands (including the study region of the Madeira archipelago).…”

Section: Study Areamentioning

confidence: 99%

“…Spawning area representation is based on Miller et al (2019), the Sargasso Sea on Knoles (2020), ocean currents on Hamilton (2018) and Cardoso & Caldeira (2021) with a mean annual precipitation of 360 mm. Consequently, it lacks permanent streams (Innocentini et al, 2022). The island's drainage network is characterised by torrential flows in winter, but the beds are dry or almost dry during the rest of the year (Gil, 2015).…”

Section: Study Areamentioning

confidence: 99%

“…Nonetheless, the orography, climate and human modification of the volcanic islands inhabited by the species in Macaronesia may pose major challenges to this catadromous fish. Namely, the steep slopes, seasonally dry water courses and artificial anti‐flooding structures may prevent or limit its upstream migration (Couto et al, 2012; Innocentini et al, 2022; Reis, 2015). The influence of steep slopes and smaller human‐constructed structures – natural and artificial obstacles – on eel distribution has been poorly studied even on the mainland (Belletti et al, 2020; Moriarty & Dekker, 1997; OSPAR, 2022).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Searching for the critically endangered European eel in oceanic islands: A pioneer study in the freshwater systems of Madeira, Macaronesia

Órfão,

Álvarez,

Ramalhosa

et al. 2024

Aquatic Conservation

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The globally threatened European eel (Anguilla anguilla) is the only freshwater fish native to Macaronesia. Despite being a keystone species to freshwater habitats, little is known about its population, environmental associations and conservation requirements in oceanic islands. The density and geographical‐related factors influencing the distribution of A. anguilla in the subtropical Archipelago of Madeira (Portugal) were examined. Data on the species occurrence was initially collected using an online survey addressed to citizens. Eels were then sampled through electrofishing in 31 sampling sites along 11 streams on Madeira Island, and eel‐habitat associations were investigated using LMMs and GLMMs. One stream was also sampled in Porto Santo Island. The presence of A. anguilla was confirmed in the two islands of the archipelago with streams (Madeira and Porto Santo). Eels are distributed throughout Madeira Island, being more abundant – particularly small size individual– at lower altitudes (mostly below 150 m). The number of weirs was an important predictor of eel density, suggesting that these flood‐control structures limit their upstream migration. This study represents a pioneer sampling effort of the European eel in Madeira and results provide much‐needed baseline information on the species distribution and related environmental factors in oceanic islands. While most eel research has historically focused on mainland habitats where dams pose a significant threat to eel habitats, our study underscores the critical importance of addressing smaller, often overlooked barriers that may also cause habitat fragmentation. The European eel is a panmictic species, thus, the conservation of the Macaronesian subpopulations can have substantial benefits for its global recovery. A comprehensive investigation of the impact of man‐made obstacles on eel habitat is still needed. Similarly, other common threats such as interactions with non‐indigenous species and infection by Anguillicola crassus should be a research priority in future studies.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Searching for the critically endangered European eel in oceanic islands: A pioneer study in the freshwater systems of Madeira, Macaronesia

Órfão,

Álvarez,

Ramalhosa

et al. 2024

Aquatic Conservation

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Present‐day sedimentary processes on the shelves of inactive volcanic ocean islands: The case study of Porto Santo Island (Madeira Archipelago)

Innocentini,

Quartau,

Madeira

et al. 2024

Sedimentology

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Shelves surrounding reefless volcanic islands usually host sediment that is considered to result mostly from erosion of pre‐existing volcanic rocks, with minor contributions from active volcanism and biogenic production. However, due to the scarcity of studies on volcanic islands, the way in which sediment is produced and deposited in these settings is still relatively poorly understood. In this study, a source‐to‐sink approach is used to understand how sediments on the southern shelf of the inactive volcanic island of Porto Santo (Madeira Archipelago) have formed. To achieve this aim, sediment texture, composition (carbon content) and morphoscopic characterization are integrated with acoustic information from the shelf (multibeam bathymetry, backscatter imagery and sediment thickness). Seafloor sediments are mostly moderately sorted sands with carbonate skeletal particles representing around 80% of the grains and minor volcaniclasts and aeolianite particles from inland subaerial erosion. Multibeam and seismic data allow recognizing some elongated erosive–depositional features that give insights into present‐day and past currents on the shelf. Additionally, an assessment of the subaerial sediment contribution to the shelf has been compared to the overall sediment volume present there. The findings indicate that the current sediment volume significantly exceeds the terrigenous supply, suggesting a significant primary biogenic carbonate production on the shelf. The sediment microscopic characterization supports this hypothesis, which leads to the conclusion that on low‐relief inactive volcanic islands, like Porto Santo, the contribution of carbonate factories to shelf sediment has a bigger role than previously considered.

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Effects of currents and waves on the morphologies of coastal sandy clinoforms: sediment mobility calculations based on current meter and wave data from Southern California, U.S.A.

Mitchell,

Zhao

2023

Journal of Sedimentary Research

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In some wave-exposed coasts, sandy clinoforms occur with rollovers (locations where their surfaces steepen) at ∼ 20–60 m depth. They have been suggested to have formed from sand mobilized by strong wave agitation in shallow water that has deposited in more tranquil deeper water beyond the rollover, although other suggested origins of clinoforms might also apply. In situ information on active sediment transport is needed to address their origins. Here, we assess sediment transport across a sandy clinoform rollover at 25–30 m depth using legacy data from current meters installed across the Southern California shelf near Del Mar in depths of 15, 30, and 60 m. Although lasting only 25 hours, the data captured conditions during the passage of a cyclone, which occurs frequently along this coast. Information from a global meteorological model reveals that waves were 1–2 m in height during the cyclone passage. Using the mean particle size from vibracores (0.129 mm), sand at the 15-m-depth site would have been continuously agitated above its threshold of motion during the 25-hour period, whereas sand at the 30-m site was mobile over 17 hours. Total-load fluxes of sand estimated from the waves and currents were strong at the 15-m site and comprised mostly suspended particles. The cyclone winds drove water, including bottom water, mostly parallel to the coast, but that movement was accompanied by a downwelling component over the first ∼ 10 hours. That downwelling likely moved suspended particles from the topset of the clinoform onto the foreset. A later upwelling component may have partially reversed that particle movement but was unlikely to have been so effective. The results suggest how wave effects, coupled with downwelling currents, dominated the sand transport and deposition over this short 25-hour period, contributing to the clinoform morphology.

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Morpho-stratigraphic characterization of the southern shelf of Porto Santo Island (Madeira Archipelago): Insights for small-scale instability processes and post-LGM sedimentary architecture

Cited by 7 publications

References 63 publications

Searching for the critically endangered European eel in oceanic islands: A pioneer study in the freshwater systems of Madeira, Macaronesia

Searching for the critically endangered European eel in oceanic islands: A pioneer study in the freshwater systems of Madeira, Macaronesia

Present‐day sedimentary processes on the shelves of inactive volcanic ocean islands: The case study of Porto Santo Island (Madeira Archipelago)

Effects of currents and waves on the morphologies of coastal sandy clinoforms: sediment mobility calculations based on current meter and wave data from Southern California, U.S.A.

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