Sargassum is a genus of brown seaweed. Over 300 species are distributed internationally in each temperate and tropical climates. The species fluitans and natans are distinctive as a result of they spend their life cycle floating on the ocean, by no means attaching to the ocean ground. Different seaweed species reproduce and start life on the ocean ground .
Pelagic (open sea) sargassum has been described because the “golden rainforest of the ocean” due to the floating ecosystem it helps within the Sargasso Sea, within the western Atlantic Ocean. Pelagic sargassum additionally happens naturally within the Gulf of Mexico and the Caribbean.
Floating sargassum first started arriving en masse on shores throughout the tropical Atlantic in 2011. As much as 10,000 tonnes arrived day by day throughout a very extreme peak season. Extreme years since then embody 2015, 2018 and 2022 – however yearly there’s a important inflow. Within the Caribbean, there was good progress in understanding the pelagic sargassum seaweed. We now have a greater concept of the place it’s coming from: possible a brand new southern space of development.
In 2009 the first experiences emerged of pelagic sargassum sightings off the coast of Ghana. Densities have elevated yearly ever since. In early March 2023, massive portions have once more arrived on the shores of the Western Area of the nation.
Pelagic sargassum is helpful in plenty of methods. Marine species resembling eels, white marlin and dolphin fish depend upon it for spawning grounds within the Sargasso Sea. Industrial fish species together with tuna depend upon it for meals.
However issues come up when massive portions are skilled close to and on the shorelines of coastal communities. Algal and seaweed blooms have gotten extra frequent in seas and oceans worldwide, each far offshore and nearshore. There’s solely restricted proof of a hyperlink between pelagic sargassum blooms and local weather change, however warming oceans do appear to be one explanation for the rise in different dangerous algal blooms in coastal areas.
The pelagic sargassum off Ghana’s coast is affecting communities’ capability to fish and use their seashores.
Significance of fishing in Ghana
Greater than 60% of Ghana’s residents stay inside 200km of the coast and 42% inside 100km. The artisanal or small-scale fisheries sector employs an estimated 80% of the nation’s fishers.
Round 2.4 million folks, about 10% of the inhabitants, work within the fisheries sector. Small-scale fisheries contribute about 4.5% to Ghana’s gross home product (GDP). The coastal areas of the nation are significantly depending on fisheries for his or her livelihoods.
Marine fisheries are the first supply of revenue for greater than 200 coastal villages, together with about 200,000 fishers with roughly 2 million dependants .
Impacts of pelagic sargassum on fishing communities
In a latest examine we assessed the affect of pelagic sargassum on the livelihoods of fishers on Ghana’s coast. By means of group discussions, surveys, discipline observations and images, we documented the experiences of fishers. Most (70%) of these we spoke to throughout three websites within the area – Sanzule, Beyin and Newtown – relied on fishing for his or her sustenance and livelihood.
The seaweed had considerably affected the livelihoods of fishing dependent communities within the western area. Pelagic sargassum had diminished their fish catch by getting tangled in nets. It made up a lot of the catch as an alternative of fish.
Pelagic sargassum additionally inhibits fishing by:
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breaking nets and filling nets
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clogging outboard motors on boats
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creating seaweed mats which are unimaginable to navigate boats by
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inflicting pores and skin irritations
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inflicting insufferable discomfort from the scent.
These preliminary outcomes spotlight the urgency of discovering methods to handle pelagic sargassum in western Africa. However to attain this, we additionally want extra knowledge and an improved understanding of what’s taking place.
Options
To determine options, you will need to know what forms of seaweed are arriving, their origins, makes use of and how one can monitor them. It’s potential that the solutions are the identical for west Africa as within the Caribbean. However that is an assumption. Little or no is understood about pelagic sargassum in West Africa.
What we do know, as scientists, is that answering a few of these questions for locations like Ghana is perhaps even trickier than it was for the Caribbean.
Take forecasting and early warning, for instance. These processes depend on adequate cloud-free satellite tv for pc imagery together with an understanding of ocean processes and climate programs. Which means detecting the place the pelagic sargassum is at any given second, together with ocean course of fashions, to forecast the place it will likely be later.
However west African coasts are inclined to have important cloud cowl. Strategies that labored properly within the Caribbean could not work in Ghana.
Not too long ago, a workforce from universities in Ghana, the UK and Jamaica got here collectively to discover how ground-based pictures may create a helpful dataset to raised perceive the seasonality and volumes of pelagic sargassum arriving in Ghana, utilizing citizen science strategies.
Citizen science recognises the necessary function that the general public can play in analysis, and invitations non-researchers to be a part of knowledge assortment and evaluation.
Citizen science is now utilized worldwide for coastal monitoring however focuses nearly solely on coastal erosion. Coastal erosion work, such because the CoastSnap platform, paperwork how the bodily construction of coastlines adjustments throughout days, months and years. The citizen science monitoring is achieved by putting in a easy steel pole and a few signage requesting {that a} passersby take a fast photograph with their cell phone and share it on-line or by way of an app.
In our work, we have now come along with colleges and group members from Beyin, Esiama and Sanzule within the western area of Ghana to use CoastSnap to review pelagic sargassum. Collectively, we have now put in three of those steel monitoring posts. Academics and group members are actually photographing the impacts that the seaweed has on folks’s lives when it arrives.
Regularly, we are going to study extra about pelagic sargassum impacts and adaptation choices in west Africa.
