Posted: November 29th, 2023

Sargassum Ecosystem: A Vital but Vulnerable Marine Habitat

Sargassum Ecosystem: A Vital but Vulnerable Marine Habitat

Sargassum is a genus of brown macroalgae (seaweed) that can be found in both benthic (attached to the seafloor) and pelagic (free-floating) forms. The pelagic forms of Sargassum create a unique and ecologically significant marine ecosystem that supports a high diversity of life. However, this ecosystem is also facing various threats and challenges that require more research and conservation efforts.

What is Sargassum and where does it come from?

Sargassum belongs to the order Fucales of the class Phaeophyceae, which are mostly cold-water organisms that benefit from nutrient upwelling. However, Sargassum is an exception, as it can thrive in warm, oligotrophic (low-nutrient) waters of the tropical and subtropical oceans.

There are over 300 species of Sargassum, but only two are holopelagic, meaning they never attach to the seafloor and reproduce vegetatively. These are Sargassum natans and Sargassum fluitans, which are the main components of the pelagic Sargassum ecosystem.

Pelagic Sargassum originates from two main regions: the Sargasso Sea in the North Atlantic Ocean, and the North Equatorial Recirculation Region (NERR) in the tropical Atlantic Ocean. The Sargasso Sea is a large gyre (circular current system) that traps Sargassum within its boundaries, while the NERR is a smaller gyre that transports Sargassum westward towards the Caribbean Sea and the Gulf of Mexico.

Pelagic Sargassum can form isolated clumps, long windrows, or extensive mats that cover hundreds of square meters. These formations are influenced by wind, waves, currents, and biological factors.

Why is pelagic Sargassum important?

Pelagic Sargassum provides food, shelter, nursery, spawning, and migratory habitat for a variety of marine organisms, such as invertebrates, fish, turtles, birds, and mammals. Some of these organisms are endemic (found only in Sargassum), while others are transient (visit Sargassum occasionally).

Pelagic Sargassum also contributes to the global carbon cycle by sequestering carbon dioxide through photosynthesis and exporting organic carbon to the deep ocean through sinking. Pelagic Sargassum also produces oxygen and releases dimethyl sulfide (DMS), a gas that influences cloud formation and climate regulation.

Pelagic Sargassum also has socio-economic value for humans, as it supports fisheries, tourism, biotechnology, and traditional medicine. Some species of fish that are associated with Sargassum are commercially important, such as dolphinfish, tuna, amberjack, and flying fish. Pelagic Sargassum also attracts tourists who enjoy snorkeling or diving among the floating seaweed and its inhabitants. Pelagic Sargassum also contains bioactive compounds that have potential applications in pharmaceuticals, cosmetics, and nutraceuticals. Pelagic Sargassum has been used as a herbal remedy in traditional Chinese medicine for centuries.

What are the threats and challenges facing pelagic Sargassum?

Pelagic Sargassum is facing several threats and challenges that may affect its distribution, abundance, composition, and function. Some of these are natural, such as storms, predators, parasites, diseases, and invasive species. Some of these are human-induced, such as climate change, pollution, overfishing, habitat degradation, and coastal development.

One of the most noticeable impacts of human activities on pelagic Sargassum is the increase in its biomass and frequency of strandings on shorelines since 2011. This phenomenon has been attributed to various factors, such as increased nutrient inputs from river runoff (especially from the Amazon and Congo), changes in ocean circulation and temperature patterns due to climate change, and alterations in the genetic diversity and morphology of Sargassum due to selective grazing by fish.

While pelagic Sargassum provides many benefits for marine life and humans when it is in the open ocean, it can cause negative impacts when it accumulates on beaches. These impacts include:

– Smothering of benthic habitats and organisms
– Alteration of beach morphology and erosion
– Emission of hydrogen sulfide gas (H2S) during decomposition
– Attraction of pests and pathogens
– Reduction of tourism revenue
– Increase in beach cleaning costs
– Interference with fishing activities
– Obstruction of navigation and power generation

How can we protect and manage pelagic Sargassum?

Pelagic Sargassum is a vital but vulnerable marine habitat that requires more attention and action from researchers, managers, policymakers, and the public. Some of the possible ways to protect and manage pelagic Sargassum are:

– Conducting more scientific research on the ecology, physiology, genetics, and biogeochemistry of pelagic Sargassum and its associated organisms
– Developing and implementing monitoring and forecasting systems for pelagic Sargassum distribution and abundance
– Establishing and enforcing regulations and guidelines for sustainable harvesting and utilization of pelagic Sargassum
– Promoting and supporting conservation initiatives for the Sargasso Sea and other areas of high pelagic Sargassum biodiversity
– Enhancing public awareness and education on the importance and value of pelagic Sargassum
– Encouraging and facilitating collaboration and cooperation among stakeholders at local, regional, and international levels

Pelagic Sargassum is a remarkable marine ecosystem that deserves our respect and appreciation. By understanding its role in the ocean, recognizing its benefits and challenges, and taking action to conserve and manage it, we can ensure its survival and sustainability for the future.

Bibliography

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