Sargassum Seaweed: The Brown Seagrass Along The Liberian Coasts

CONTEXT: Liberia has an extensive coastline of approximately 570km long. The area lies within the West Africa sub-region and experiences Guinea Current, which flows eastward along the western coast of Africa derived from the North Equatorial Counter Current (NECC) and the Canary Current. The region’s biodiversity contains diverse fish, shellfish, shrimps, crabs, lobster, gastropods and cephalopods, reptiles, sea turtles, marine mammals, and other living organisms. Seaweed distribution and diversity has been reported to be in close association with nutrientrich upwelling region. Ecological factors prevalent inLiberia’s coastal waters and tropical West Africa, such as low tidal amplitude, a shallow, permanent thermocline, negligible upwelling phenomenon, and lack of natural rocky shore, may be reasons for poor seaweed diversity in Liberia.

 

In 2015, Liberia witnessed a massive invasion of seaweed,and since then, it has been spreading rapidly to the riverine villages and towns of Liberia. In recent times a brownish seaweed has been observed floating, and some washed ashore of several coastal beaches and brackish water at different locations in Liberia.

 

However, despite considerable interest in the research and development of marine resources, particularly fisheries, surprisingly little effort has been directed at the associated non-fish resources in recent years. Apart from their ecological role, aquatic macrophytes (i.e., seaweed)contribute significantly to Liberian water bodies’ economic, scientific, and recreational importance. The ecology, population dynamics, and socio-economic importance of the resources are interrelated with other dependent aquatic organisms. Although if present in large quantities, aquatic plants may have adverse effects on navigation, result in high water losses through evapotranspiration, and provide habitat for vectors of water-borne diseases. In a balanced environment, they have recreational, aesthetic, and medicinal values.

 

Biophysical Impacts Stranding on coastlines negatively impacts the Sargassum (a potentially beneficial habitat at sea) as it dies and subsequently decays. Also, in that process, the sustained presence of large quantities of decaying biomass negatively impacts coastal and nearshore marine life through a few mechanisms: 1) it prevents strong sunlight from reaching important shallow-water ecosystems (i.e., mangroves, seagrass beds, coral reefs), reducing photosynthesis processes and causing rapid degradation and even coastal dead zones; 2) The accumulation and decay of large amounts of Sargassum in the water can result in hypoxia (low oxygen levels) and the release of poisonous hydrogen sulfide, potentially causing the death of marine life; and 3) Smothering in large quantities of Sargassum can result in death for some marine animals. For example, significant quantities of Sargassum on beaches prevent newly hatched turtles from reaching the ocean. Similar may also be the case for interstitial organisms in beach ecosystems. In water, the thick mats can prevent animals from reaching the surface to breathe, and entanglement can cause animals to be washed onto shore along with the seaweed. Large numbers of dead fish, sea turtles, and dolphins have been found dead, washed ashore in the thick raft of seaweed.

 

Sargassum washing ashore can, in some cases, yield a positive impact, wherein the seaweed aids in stabilizing the beach. However, this benefit is likely lost with large quantities that overwhelm a beach or bay and would often be offset by significant negative impacts depending on the resources present and uses of the beach.

 

Socioeconomic Impacts Sargassum influxes negatively impact human well-being, activities, livelihoods, andsignificant sectors of West African Economies. Key sectors affected include coastal living and livelihoods, marine transport and navigation, public health, fisheries, and tourism. These impacts are interrelated, with many stemming from one of the critical drivers of the biophysical effects – the decay of the sargassum biomass. The production of hydrogen sulfide negatively impacts air quality, results in very unpleasant odors, and prolonged exposure is unhealthy, especially for persons with underlying respiratory conditions. This is detrimental for coastal residents and beach users, whether local or visitors. Beach users who live elsewhere can avoid impacted locations, while residents may be unable to avoid prolonged exposure. Large quantities of Sargassum also spoil the aesthetic appeal of our beaches and inhibit access to nearshore waters. Both issues affect residents, local beach users, and tourists, while the latter particularly impact those whose livelihoods rely on the sea, such as small-scale fishers who may need to access the water to access their equipment and livelihood.

 

Conclusion Significant progress has been made in the last ten years since Sargassum influxes first emerged in the West African region. However, addressing the issue hasgenerally been reactive rather than proactive, resulting in environmental degradation, inefficient use of resources, and poor governance. There also has been significant research and business interest in exploiting Sargassum as a commodity or exploiting those desperate to be rid of Sargassum. The arena is now very dynamic with the entry of many players with varying, sometimes competing interests. There are numerous projects and initiatives at national, multi-country, and sub-regional levels that are sometimes very similar. Yet, no formal attempt has been made to explore opportunities for promoting synergies to avoid unnecessary duplication. Through the Abidjan Convention, Liberia is working at the regional level to address the challenges and explore regional collaboration and partnerships opportunities.

 

This complexity is consistent with and reflective of the complexity and character of the region but adds to the challenge of mounting a coherent response. With so much going on, coordination and collaboration are spoken of. However, there is inevitably fragmentation, disconnects,and gaps. As a result, effort and resources are not being applied efficiently or optimally. This situation has needed a systematic and strategic extensive picture review to consider what is being done, identify gaps and devise a strategy to better coordinate and apply effort and resources, fill gaps, recover costs, and promote synergies between existing initiatives, particularly at the regional level.

NOTE: Sheck Abdul Sherif, PhD Candidate at Queen’s University Belfast and Co-Chair of the Ocean Acidification Africa Network contributed to this article.

 

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