Secret garden under the sea, what are we doing to conserve them?

World Ocean’s day is fast approaching! This week we will share some short articles from current grantees under WIOMSA’s MASMA and MARG programmes. 

Secret garden under the sea, what are we doing to conserve them?

Article by: Blandina Lugendo

Seagrasses, the flowering plants of the sea. Like land (terrestrial) plants, seagrasses are among key components of shallow water areas of most tropical countries of the Western Indian Ocean (WIO) region.  

They often occur in close proximity with the beautiful coral reefs and the tall- greenish trees called mangroves. Sometimes they are called “secret gardens of the ocean”. Seagrasses are known to support high biodiversity mainly due to abundant food and complex habitat structure that offers refuge to the myriad of species, including endangered dugongs and the beautiful sea turtles.  

Seagrasses provide many important ecosystem services to coastal communities, through support to fisheries and tourism industries, as well as in the protection of the coastline and the infrastructure along the coast. Nevertheless, benefits arising from seagrasses are not properly acknowledged due to a number of reasons, including little awareness. 

Unlike coral reefs and mangroves, seagrasses have not received similar attention.  We know little on their coverage in the region, on top there is no comprehensive mapping not only in the region but also in most countries. We are learning seagrass meadows have disappeared at a rate of 7% of their total global area per year between 1990 and 2006. Seagrass loss, degradation and fragmentation are still continuing in many areas, and therefore it is logical to generalize that seagrass beds in the WIO region are in a declining trend like many parts of the worlds. 

There are numbers of threats facing seagrasses in the WIO region, most of them are from human activities, the most widespread being the use of destructive fishing gears, particularly the use of beach seines and bottom trawls fishing. Collection of invertebrates from the intertidal area that often involves revolving huge amount of sediments is another serious threat. At a large scale, there is pollution particularly excessive nutrient inputs from unregulated land-based activities let alone ports and other coastal developments. 

Excessive nutrients inputs from untreated sewage and agricultural activities to the sea trigger proliferation of algae that covers seagrasses from getting sufficient light as the consequence seagrass will die.   

When seagrass beds are degraded, they lose their complexity and functionality, leading to severe impacts on the biodiversity and entire marine ecosystems. The effect is extended to human well-being as well. Among these impacts is shoreline erosion. Shoreline erosion in the WIO has caused severe loss of habitats and properties in most countries, this has been witnessed in Kenya, Tanzania and Mozambique. 

Some countries in the WIO, including Comoros, Kenya and South Africa have managed to map all their seagrass beds. Some attempts to map seagrasses have also been undertaken at some localities in Tanzania, French Territories, Mauritius, and Mozambique. While no legislation to protect seagrass beds exist in the WIO, Kenya has managed to establish a management and conservation strategy for coral reefs and seagrass ecosystems in 2013. These efforts should inspire other countries to follow suit. Seagrass restoration within the WIO is limited to some trials in Kenya and Mozambique which calls for further investigation on the best techniques for seagrass restoration in the tropics. 

There are no discrete borders in the Ocean, and so benefits (ecosystem services) accrued from them, impacts of human actions, and impacts to human well-being are not confined within borders. Regional cooperation, as well as cooperation with countries and institutions outside the region, is crucial when scientific and technological development is concerned. If we really need to realize the impacts of the management efforts, apart from appropriate policies, governance structures and technologies, collaborations are indispensably crucial and need to be promoted. 

A WIOMSA’s funded MASMA project titled ‘Seagrass Protect’ provides a good example of such collaborations. The project is set to among other objectives, conduct seagrass mapping, study how seagrasses influence sediment movement and water currents, investigate on the best practices for seagrass restoration and evaluate how seagrass restoration can lead to sustainable shoreline management. This ambitious venture is taking place in Tanzania and Mozambique, findings can be used in other countries in the WIO. The project is implemented by a trans-disciplinary team of researchers with experience in different fields of marine sciences ranging from socio-economics, ecology to geology. The team is led by Dr Blandina Lugendo (University of Dar es Salaam). Others are Prof. Johan Hollander and Prof. Olof Linden (World Maritime University), Prof. Salomao Bandeira (Mozambique), Dr Yohana Shaghude, Dr Mwanahija Shalli and Dr Siajali Pamba (University of Dar es Salaam). The project has also enrolled two PhD students; Manuela Mobuto (Mozambique) and Marcelina Mushi (Tanzania). You can find more information regarding this project through its webpage 

Blandina Lugendo is a lecturer at the University of Dar es salaam 


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