Bhagooli, Ranjeet

Ramah, Sundy

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179WIO Journal of Marine Science  Special Issue 2/ 2021 179-182Seagrass meadows are one of the most produc-tive marine ecosystems in the world (Duarte and Cebrian, 1996). They play key ecological roles in providing important services such as nursery and feeding grounds for juvenile fish and other marine organisms, thus maintaining populations of com-mercially exploited fishery resources ( Jackson et al., 2001). Seagrass has strong linkages with coral reefs and mangroves, forming one of the most productive coastal habitats, and can play a critical role in buffer-ing the effects of ocean acidification on adjacent coral reefs (Anthony et al., 2011). They often form extensive meadows which can be of mono- or multi- specific species. They are commonly situated in shallow areas of lagoons up to 20 meters depth, or deeper if the environmental conditions permit photosynthesis. There are about 60 species of seagrasses worldwide and 13 species are known to occur in the Western Indian Ocean (Gullstrom et al., 2002), making up an important habitat in coastal waters (Gullstrom et al., 2002; Duarte et al., 2012). While it has been reported that 5 seagrass species prevail in Mauritian waters ( Jagtap, 1993), very few studies have been carried out on seagrasses and their associated organisms (Pau-piah et al., 2000; Daby, 2003; Nakamura et al., 2006; Ramah et al., 2014), and even less on their occurrence on distant fishing banks, creating a significant knowl-edge gap on this important ecosystem in the waters of the Republic of Mauritius.During the EAF-Nansen Indian Ocean Research Expedition 2018, two shallow locations over the Naz-areth Bank were explored; location SS45 (14o 10.852’S; 60o 56.465’E) and SS46 (14o 24.848’S; 61o 02.659’E) on the northeast of the bank with a depth range of 35-36 m and 34-38 m, respectively. The Nazareth Bank is found within the Exclusive Economic Zone of the Republic of Mauritius and is characterised by a sur-rounding slope of about 150 m with a shallow cen-tral part of about 50 - 60 m deep (Mees, 1996). With the aid of the Argus Remotely Operated Underwater Vehicle (ROV) attached to the Video-Assisted Mul-ti-Sampler (VAMS), SS45 and SS46 were explored for 11 minutes along a transect of 37 m and 30 minutes along a transect of 110 m, respectively. Both areas were covered with the seagrass Thalassodendron cilia-tum or mixed with organisms such as Halimeda spp. and sponges, among others (Fig. 1). Both locations indicated the occurrence of one dominant species of seagrass of approximately 90 – 100 % coverage within the studied area, similar to the Saya de Malha Bank. This observation provides new information on seagrass beds occurring on the Mascarene pla-teau, notably on the Nazareth Bank.One of the very important services that seagrass beds provide, besides being important as nursery grounds for fish and other juvenile benthic organisms, is its blue carbon storage capacity. While seagrasses have been recognised for their carbon sequestration capac-ity since the 1980s (Smith, 1981), this topic has received very little attention until recently where they have been recognised as a blue carbon ecosystem that could potentially contribution in addressing climate change impacts (Duarte et al., 2005, 2013; Mcleod et al., 2011; Fourqurean et al., 2012; Gullstrom et al., 2018; Bedulli et al., 2020). Indeed, seagrass can absorb carbon diox-ide from the atmosphere and the ocean for the process First field observation of a Thalassodendron ciliatum bed on the Nazareth Bank,  Mascarene PlateauSundy Ramah 1,2*, Ranjeet Bhagooli 2Field Note1 Albion Fisheries Research Centre, Ministry of Blue Economy, Marine Resources, Fisheries and Shipping, Albion, Petite Rivière 91001, Republic of Mauritius2 Department of Biosciences and Ocean Studies, Faculty of Science & Pole of Research Excellence in Sustainable Marine Biodiversity, University of Mauritius, Réduit 80837, Republic of Mauritius* Corresponding author:  sundy.ramah@gmail.comhttp://dx.doi.org/10.4314/wiojms.si2021.2.13180 WIO Journal of Marine Science  Special Issue 2/ 2021 179-182  |  S. Ramah & R. Bhagooli Figure 1. Figure 1. Presence of large seagrass beds (T. ciliatum) on the Nazareth Bank. A-D: Location 45 at a depth range of 35-36 m. E-H: Location 46 at a depth range of 34-38 m. D and H represents a closer view of the seagrass species at Location 45 and 46, respectively. Photographs were taken using the Argus Remotely Operated Underwater Vehicle (ROV).181S. Ramah & R. Bhagooli   |  WIO Journal of Marine Science  Special Issue 2/ 2021 179-182of photosynthesis and store the organic carbon for a long time in the underlying sediments (McKenzie and Unsworth, 2009). Globally, they have been estimated to sequester between 27-44 Tg (approximately 10-18 %) of organic carbon per year in the ocean. This is com-parable to terrestrial and mangrove forests (Duarte et al., 2005; Fourqurean et al., 2012). A study in 2012 by Gullstrom et al. (2018), conducted on the Eastern Afri-can coast of Tanzania and Mozambique, demonstrated that of the four species of seagrass meadows targeted, Enhalus acoroides, Thalassia hemprichii, Cymodocea spp., and T. ciliatum, meadows of both E. acoroides and T. ciliatum had a signifi cantly higher organic carbon stock (approximately 7305 gm-2) as compared to the other two species.Research carried out on the Nazareth Bank is extremely limited and has been concentrated mainly on its fi sheries resources (Caussy et al., 2019), primary productivity (Ramchandur et al., 2017) or oil and gas prospects (Meyerhoff  and Kamen-Kaye, 1989), while no research has been carried out on its benthic hab-itats, especially on the presence of seagrass beds with potential for blue carbon sequestration. This fi rst fi eld observation on the presence of large T. ciliatum mead-ows at two shallow water areas within the Nazareth Bank brings forth new knowledge on the distribution of this species in the waters of the Republic of Mau-ritius. More work is however warranted to thoroughly explore the distribution of such meadows within the Bank as well as their potential for carbon capture.AcknowledgementsThe underlying work was made possible with the support of the EAF-Nansen Programme “Supporting the Application of the Ecosystem Approach to Fish-eries Management considering Climate Change and Pollution Impacts” executed by Food and Agriculture Organization of the United Nations (FAO) and funded by the Norwegian Agency for Development Cooper-ation (Norad). The authors are thankful to FAO for funding and supporting the Indian Ocean research expedition 2018 on the Saya de Malha Bank and Naza-reth Bank with the R/V Dr Fridtjof Nansen, the Depart-ment of Continental Shelf, Maritime Zones Admin-istration & Exploration of Mauritius for co-leading and coordinating the scientifi c expedition, the Mau-ritius-Seychelles Joint Commission of the Extended Continental Shelf for their support and assistance and granting the necessary authorisations, the Min-istry of Blue Economy, Marine Resources, Fisheries & Shipping for hosting and spearheading the Habitat Mapping Workshop in Mauritius and for granting necessary authorization to carry out research in the Nazareth Bank; the Institute of Marine Research, Norway for leading the expedition and providing the technical and logistic support. 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First field observation of a Thalassodendron ciliatum bed on the Nazareth Bank, Mascarene Plateau

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First field observation of a Thalassodendron ciliatum bed on the Nazareth Bank, Mascarene Plateau

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