WIOMSA ScienceNews provides updates on current WIOMSA-funded research projects. Grantees share their field experiences as well as their research results. In this week’s update, we look at Ecosystem-Based Coastal Zone Protection: The Effectiveness of Seagrass Meadows in Coastal Erosion Management (The Seagrass Project, in Tanzania).
Seagrass restoration successful in Tanzania
Planting a large number of shoots and using a specific planting method improves survival and success.
By January Wegoro, Blandina Lugendo, Siajali Pamba and Johan Hollander
According to ongoing research, seagrass restoration is possible in Tanzania, but it will need time and expertise to establish a best practice and optimize restoration techniques.
Seagrasses are widespread in both tropical and temperate coastal areas. As one of the most productive ecosystems on earth, it is also a major nursery and protective habitat for marine life. Seagrasses play a vital role in global carbon storage, helping to mitigate climate change. Unfortunately, while seagrasses provide exceptional ecological services, they have decreased worldwide, primarily because of human activities. When seagrass beds are damaged, they lose their complexity and ecological functions.
Scientists have devised methods for restoring degraded seagrass ecosystems. Through the Marine and Coastal Science for Management (MASMA) programme, WIOMSA funded the University of Dar es Salaam in Tanzania to restore damaged seagrass habitats in Tanzania. The research project focuses Syringodium isoetifolium species and adopted the plug and the sprigs method of restoration
In global assessments of seagrass restoration initiatives, a survival rate of more than 30% is considered a significant achievement.
The findings in this research indicate a very high survival rate of 49.7% for the 10 cm diameter plugs, compared to 40.7 % the 7 cm diameter plugs, indicating that the restoration activity in this project was extremely effective. A survival percentage of more than 30% is considered a major accomplishment in global evaluations of seagrass restoration efforts.
We made remarkable discoveries in the course of our study. The first is that the wider the diameter of the plug, the higher the growth rate. The 10 cm diamater plus had higher growth rates (7.65 leaves/day) than the 7 cm diamater plug (5.11 leaves/day).
Secondly, the sprigs method proved to be less successful, with plants surviving for only two months after planting. Furthermore, the sprigs did not produce any new shoots before dying. Nonetheless, we discovered that the 5 apical shoot sprigs showed a higher survival percentage (14%) than the 3 apical shoots sprigs (5%). This result implies that planting an increased number of shoots and planting techniques increases survival and success rates.
Caption: Planting techniques used for seagrass restoration in Tanzania – plug method.
Further findings demonstrate that Syringodium isoetifolium produces on average 3 shoots and 1 internode per week, with an internode length of 4 cm. This implies that it will take about 25 weeks on average for the species to cover 1 m2 under normal conditions. Our findings also show that restored seagrass beds improve significantly during the northeast monsoon when the ocean is calm and the waters are clear, with more rhizome elongation and shoot production than during the southeast monsoon, when the ocean is turbulent and turbidity is significant.
Given the time and the costs of seagrass restoration efforts, protection of existing beds, and preventing the leading causes of seagrass degradation, undoubtedly remain the best option for seagrass conservation.