Integrating sediment dynamics into habitat mapping approaches using sediment mobility indices and seabed classification in Galway Bay, Ireland.

Sediment dynamics information provide vital insights into the important role of oceanographic forcing factors on habitat distribution; yet remains an under-utilized physical surrogate in marine habitat mapping studies. An integrated oceanographic and geophysical analyses of dynamic processes combining sediment mobility indices, obtained from coupled-hydrodynamic- wave sediment transport models; with seabed classification has been made at Galway Bay, Ireland.

Maerl or rhodolith coralline red algae beds are abundant in Galway Bay and these beds represent more than 65% – 70% of the maerl habitats in Ireland (De Grave and Whitaker, 1999). Maerl beds are particularly affected by hydrodynamics and increased storminess resulting in recurrent disturbance of the benthic habitat patch during winter storms. Live maerl beds are biodiversity rich coastal habitats and form subtidal and intertidal banks and open marine beds. Dead maerl beds of the branched maerl morphotype are considered to be biogenic sediment with form dense biogenic gravel debris beaches.

Sediment mobility modelling is of importance to a range of disciplines including sediment dynamics, marine conservation, coastal engineering, and renewable energy (Harris and Coleman, 1998; Idier et al., 2010; Li et al., 2015, Joshi et al, 2017a, Coughlan et al. 2021). It is based on the fundamental quantity of bed shear stress and the impact of pure currents, wave-only, wave-induced currents or combined wave-current flow on surficial sediments.

Multibeam backscatter from the INFOMAR national seabed mapping program of Ireland have been utilized for seabed classification using the new machine learning and deep learning libraries in ArcGIS Pro and Python.

An integrated interpretation of the dynamic processes happening at the seafloor is made as a result of the combined wave-current induced disturbance regime during storm conditions. Implications for future conservation management of maerl beds impacted by increased storminess and anthropogenic activity are discussed.


Coughlan, M., Guerrini, M., Creane, S., O’Shea, M., Ward, S.L., Van Landeghem, K.J.J., Murphy, J., Doherty, P., 2021. A new seabed mobility index for the Irish Sea: Modelling seabed shear stress and classifying sediment mobilisation to help predict erosion, deposition, and sediment distribution. Continental Shelf Research 229, 104574.

De Grave, S., Whitaker, A., 1999. A census of maerl beds in Irish waters. Aquatic Conservation: Marine and Freshwater Ecosystems 9,303-311.

Harris, P.T., Coleman, R., 1998. Estimating global shelf sediment mobility due to swell waves. Marine Geology 150, 171177.

Idier, D., Romieu, E., Pedreros, R., Oliveros, C., 2010. A simple method to analyse non-cohesive sediment mobility in coastal environment. Continental. Shelf Research. 30, 365–377.

Joshi, S., Duffy, G.P., Brown, C., 2017a. Mobility of maerl-siliciclastic mixtures: Impact of waves, currents and storm events. Estuarine, Coastal and Shelf Science 189, 173–188.

Li, M.Z., Hannah, C.G., Perrie, W.A., Tang, C.C.L., Prescott, R.H., Greenberg, D.A., 2015. Modelling seabed shear stress, sediment mobility, and sediment transport in the Bay of Fundy. Canadian Journal of Earth Science. 52, 757–775.

Cite as:

Joshi, Siddhi. (2022). Integrating sediment dynamics into habitat mapping approaches using sediment mobility indices and seabed classification in Galway Bay, Ireland. GeoHab 2022, Venice.


A StoryMap of this research can be found at the link

My journey in oceanography

Growing up listening to the sounds of the sea in a shell. The entire seascape captured within the delicate structure of the conch. The inspiration of nature drove me to continuously spend my head in the books when away from the ocean. We didn’t say studying- we said wonder. Wonder about the abyss, the deep blue ocean and its rich inhabitants. How they breathe, how they respire. Eating their way across the food web. A pioneering life history strategy they said- that was our vision. As a student of marine science, there was so much to learn- so much to inspire, digest and reflect upon. The continuous inspiration of the oceans drove me forward into the deep blue wilderness of the abyss. Where had I come from to do oceanography? From a place in my imagination so intrinsically connected with nature. A place unexplored where explorers seek to find wonder. Confronted with scientific understanding I looked to nature to find my muse. Paper after paper, searching for the vision of the natural world within my data. I learned to be a scientist, an ecologist mapping the shallows as well as the deep. Listening to the sea and all its glory I sat there wondering what could be done to save our oceans.

Continue reading “My journey in oceanography”

GeoHab Habitat Mapping conference happening in Venice

Apologies for the pause in our Seabed Habitats Seminar Series, we hope to find more speakers, increase collaboration and scientific engagement in the coming year. (Plus I have also been working on the Challenger Society for Marine Science’s Early Career Researcher Seminar Series.) Meanwhile, the GeoHab Habitat Mapping conference will take place in Venice, Italy in 16-20 May 2022 and is a wonderful opportunity to learn about the latest scientific developments from leading scientists in marine habitat mapping including a workshop on “Ocean mapping in the Anthropocene: new technologies and Artificial Intelligence (AI) tools.” It’s quite a challenge as an independent marine scientist, but I hope to present at this conference this year and have submitted an abstract before the deadline! It is possible for Masters and PhD students to apply for support to attend the conference (see Student Awards page on the GeoHab website).

Venice (Collage by DanieleDF1995 (talk), Wikipedia, CC BY-SA 3.0)


I would like to acknowledge and thank the Challenger Society for Marine Science, for the Stepping Stones Bursary Award, to make participation possible. Their support is much appreciated.

Seabed ecosystems and indigenous livelihoods

The word “Kadalamma” meaning Mother Ocean has been used for many generations to refer to the sea.

Kumar Sahayaraju

Indigenous fisherman, marine researcher and Chevening scholar Kumar Sahayaraju, gave the January 2022 seminar as part of the Seabed Habitats Seminar Series. Kumar spoke of the indigenous knowledge of the Mukkuva indigenous fishing community in India. The community has seen a close connection with the sea for generations and depend on it for their livelihood. Due to the increasing pressures of large scale industrial development at this coast, marine habitats rich in biodiversity have deteriorated after being neglected. Kumar brought attention to this issue through his seminar and by fostering collaborations with scientists as well as the general public. Citizen science initiatives involving the indigenous fishermen, ocean literacy initiatives to encourage a greater connection with the ocean habitats, and more extensive scientific insights into management are all possible solutions. Furthermore, indigenous knowledge needs to be adequately recorded and documented in order to be preserved for future generations. We would like to cordially thank Kumar for joining us and bringing light to this issue, which has parallels around the world.

Seabed ecosystems and Indigenous livelihoods in Southwest coast of India

Happy new year for 2022! We are pleased to announce that Kumar Sahayaraju, Chevening Scholar, fisherman, and indigenous marine researcher at University of Sussex, UK will be giving a seminar on Tuesday 25th January at 1300 GMT on “Seabed ecosystems and Indigenous livelihoods in Southwest coast of India.”

It is identified by the indigenous fishers that Southeastern Arabian Sea has several biodiversity-rich reefs.  Most of the reefs are rocky, some of them shaped like platforms. There are also sandy reefs and those developed over shipwrecks. Colonies of corals and mussels comprise much of the reef biodiversity, and support livelihoods of more than 300,000 artisanal fishers engaged in sustainable fishing. The local artisanal fishing practices involve a deep understanding of seabed morphology, seasonal variations in weather and sea state, seasonal climatic factors, astronomical objects and marine biodiversity.  Amidst concerns about large-scale biodiversity loss in recent years these reefs are also challenged by anthropological and climate pressures. Much of the biodiversity in these regions is poorly documented in the scientific literature, and yet the Indigenous and local knowledge of many areas is extensive, but often overlooked. The session discusses about the importance and features of seabed ecosystem as a livelihood source of indigenous fishers in South India.

Biography: Kumar Sahayaraju is an emerging Marine Biotechnologist from an indigenous fishing community in South India. Being an Engineer in Biotechnology and a scuba diver, he has the experiences of working with organisations like Friends of Marine Life (FML), an indigenous marine research organisation in Kerala and M.S.Swaminadhan Research Foundation (MSSRF) with a capacity of marine researcher and community youth leader. He is doing sea bed ecosystem studies on the Southwest coast of India and documenting the biodiversity by incorporating the knowledge of the Mukkuva indigenous fishing community in India. As a founding member of Coastal Students Cultural Forum (CSCF), he undertakes marine environment related voluntary activism and promoting ocean literacy with coastal youth and graduate students. He has graduated from University of Stirling with a prestigious UK Chevening Scholarship. He is currently working as research assistant for University of Sussex, UK and volunteering as with Radio Kadal-Community radio for fishermen in Trivandrum. In addition to this, he is volunteering with Climate Science, Ireland on Climate Education in India. He is frequently engaging on climate change, conservation of marine resources and issues of indigenous Fisherfolk in South India.

Please register for seminar and to receive occasional updates below: