Sargassum Secrets and Symbiosis

a recent surge in Sargassum reveals insights
 into how these seaweed proliferations are 
relevant examples of intelligent design

Symbiosis and Sargassum Secrets: How Seaweed Teaches Intelligent Design and Stewardship 

By Dr. Sarah Buckland-Reynolds

Imagine being on vacation along the coast of a Caribbean island. The turquoise water and white sand provide a ‘postcard perfect view,’ but as you continue along the coastline, the scene shifts. Ahead, thick brown mats of Sargassum seaweed have washed ashore, hitting you with a sharp odor reminiscent of rotten eggs mixed with brine. This is no longer the idyllic postcard of tropical tourism. As unpleasant as this change seems at the moment, this has become an increasingly common scene due to changing patterns in the movement of the Great Atlantic Sargassum Belt (GASB). 

The sustained increase in sargassum in Caribbean and Atlantic regions since 2011 has puzzled scientists for over a decade. However, recent groundbreaking research entitled “Equatorial upwelling of phosphorus drives Atlantic N2 fixation and Sargassum blooms,” Nature Geoscience, 5 December 2025 provides new insights into the intricate ecological dynamics influencing sargassum growth and movements, showing that this ‘less-than-pleasant view’ plays a vital role in the ecosystem. In this article, we explore some of the benefits of sargassum and how recent movements provide insights on intricate connections between climate and biotic processes that sustain earth’s oceans. 

From Blooms to Balance: Intelligent Design in the Caribbean’s Floating Forests 

Since 2011, the Great Atlantic Sargassum Belt (GASB) has become the largest interconnected floating biome on Earth, stretching thousands of kilometres and impacting coastal communities with unprecedented stranding events. In the open seas, sargassum provides food and shelter for fish, turtles, and seabirds. Its floating forests act as nurseries for marine life, while its nutrient cycling connects deep ocean processes to coastal habitats. Even onshore, though inconvenient for beachgoers, the decaying seaweed contributes to organic matter that can enrich coastal soils. Despite these benefits, the accumulation of sargassum on beaches has often been treated as a burden on coastal ecosystems, tourism, and public health. 

While past theories have explored the roles of Saharan dust and river run-offs in influencing sargassum distribution, this new information from Jung et al. points to a process not previously discovered in connection to sargassum: a nutrient partnership between phosphorus delivered by equatorial upwelling and nitrogen supplied by cyanobacteria living directly on the algae. This discovery highlights the usefulness of upwelling as a designed system of nutrient renewal worth exploring. 

Upwelling as a Nutrient Engine 

Equatorial Atlantic upwelling is a climate-driven oceanic process that exemplifies how the earth’s atmosphere and ocean operate as a coupled system. Oceanic upwelling is predominantly driven by prevailing trade winds which push surface waters aside, allowing colder water below the surface to rush in to replace the surface void from the water displaced by the wind. 

The process of upwelling is further influenced by the Coriolis effect (due to the spinning of the earth on its axis). At the equator, this process further deflects water northward in the Northern Hemisphere and southward in the Southern Hemisphere, leading to the equator becoming a zone of divergence. The strength of the upwelling is further influenced by temperature gradients of the sea surface, and the movement of wind circulation patterns such as the Intertropical Convergence Zone (ITCZ). Together, these forces create a finely tuned conveyor that has been known to sustain some of the most productive marine ecosystems on earth. 

While these processes have been known for decades, new insights have revealed the role of specific nutrients emerging from upwelling in maintaining the bloom of seaweed, such as sargassum. These nutrients, particularly phosphorus and nitrates, form a climate-driven ecosystem for sargassum blooms. As the authors note: 

Equatorial Atlantic upwelling and the northwestward flow of the South Equatorial Current carry excess P into the tropical North Atlantic and the Caribbean region. This “excess P”—phosphorus in stoichiometric excess relative to nitrogen—creates fertile conditions for Sargassum growth. 

The researchers have found that this process sustains productivity in otherwise nutrient-poor tropical seas. In this case, phosphorus becomes the trigger for nitrogen fixation, setting the stage for explosive algal growth. As sargassum blooms provide critical offshore habitat for turtles, fish, and invertebrates, these trends have also brought economic benefits as upwelling zones underpin fisheries that feed millions of people and sustain livelihoods in coastal communities. By enhancing primary productivity, upwelling indirectly supports tourism, aquaculture, and even coastal agriculture, as decaying organic matter enriches soils. In this way, upwelling functions as a life-giving engine that hinges upon the ‘co-operation’ of wind and ocean currents to function. 

Further Evidence of Fine-Tuning: Climate and Cyanobacteria Symbiosis 

The equatorial upwelling system is a complex system that responds on a variety of scales, with seasonal, interannual and even interdecadal oscillations in sea surface temperatures and shifts in wind strength. In cycles of up to 60-year return periods, upwelling rates change in response to the Atlantic Multidecadal Oscillation (AMO), and other cyclic modes of climate variability with adjustments made to its strength and phosphorus delivery.  

As much as climate cycle dynamics at multiple scales reveal complexity, the researchers found that these abiotic factors interact directly with microscopic biomes in the ocean, particularly cyanobacteria. The authors explain:  

Sargassum dynamics are best explained by their symbiosis with N2-fixing epiphytes, which render the macroalgae highly competitive during strong equatorial upwelling of excess P.  

Cyanobacteria are among the main stimulators of nitrogen fixation, playing an important role in nutrient cycles and ecological balance. However, their function is not independent; when these microorganisms fix atmospheric nitrogen and deliver it directly to their algal host, cyanobacteria also mutually benefit from the phosphorus-rich environment. The result is a self-reinforcing cycle of growth. 

While the biotic and climatic elements ebb and flow in mutual responsiveness, this balance ensures resilience: the ocean’s nutrient inventory is maintained through cycles of loss and replenishment. Failure of one component of this chain would diminish nutrient supply and have significant ecological and economic repercussions. 

Implications for Intelligent Design 

When we further dissect the processes described in Jung et al.’s paper, we see a system of remarkable precision in several ways, including: 

• Timed Upwelling for Ecological Balance: The seasonality of the sargassum blooms reflect distinct cycles of upwelling that exist. If nutrient‑rich deep waters were continuously forced to the surface, the balance of ocean chemistry would collapse. Constant upwelling would cause oxygen levels in the oceans to plummet and may lead to the dominance of harmful algal blooms. By contrast, periodic pulses of upwelling aligned with wind and temperature oscillations act like a timed release of fertilizer: enough to renew productivity, but not so much that the system becomes overloaded. This rhythm sustains both ecological and economic communities.  When the winds weaken and upwelling subsides, ecosystems have time to stabilize, recycle nutrients, and prevent runaway growth. 

• Symbiotic Cooperation: The partnership between algae and cyanobacteria exemplifies mutual benefit. Nitrogen fixation is costly, yet cyanobacteria thrive by attaching to Sargassum, while the algae gain a steady nutrient supply. 

• Mathematical Precision of Nutrient Balance: The research on sargassum further exemplified a mathematical pattern discovered by oceanographer Alfred Redfield in the 1930’s: that oceanic balance depended on an approximate ratio between nitrogen and phosphorus of 16:1. This atomic ratio in marine plankton often matches the ratio in seawater in healthy biomes, which is a global chemical pattern that maintains ocean stability. The dynamic between cyanobacteria in sargassum blooms periodically rebalances the ratio where excessive phosphorus trigger adaptive response of nitrogen fixation to ensure resilience.  

How could these precise patterns arise from accidental processes? 

Stewardship in the Face of Challenge 

While the ecological design is remarkable, human impacts may be mixed. Sargassum strandings release hydrogen sulphide gas and may disrupt tourism. Due to this, some tourist areas find themselves having to invest in costly removal efforts. On the other hand, there has been increased international discussion as recently as December 2025 about extracting economic benefits from the increase in sargassum blooms, as evidence also suggests they have the potential to serve as biofuel. 

Stewardship requires us to respond wisely to these challenges, bearing in mind the beneficial roles of these elements, while balancing the needs of impacted populations. 

Seaweed Speaks of our Creator

While the discovery of the nutrient partnership fueling Sargassum blooms deepens our understanding of Atlantic and Caribbean ecology, it provides yet another example of ecological resilience that reflects intelligent design. As scientists and conservation practitioners continue dialogue on understanding dynamic ocean processes effectively managing increased sargassum, Scripture provides a perfect backdrop, affirming the wisdom evident in our seas. In Psalm 104:24-25 it is declared:  

“O Lord, how manifold are your works! In wisdom you have made them all; the earth is full of your creatures. There is the sea, vast and spacious, teeming with creatures beyond number—living things both large and small.” 

The nutrient partnership between phosphorus and nitrogen, the usefulness of upwelling, and the symbiosis of algae and bacteria all testify to divine wisdom. By continuing to study its patterns, we glimpse the Creator’s design. This science shows that sargassum is not merely a nuisance but a signpost pointing to the wisdom embedded in creation.  While we navigate the challenge of sargassum blooms, we are called to be good stewards in obedience to God, in honouring the One who made the seas and all that is in them.

Dr. Sarah Buckland-Reynolds is a Christian, Jamaican, Environmental Science researcher, and journal associate editor. She holds the degree of Doctor of Philosophy in Geography from the University of the West Indies (UWI), Mona with high commendation, and a postgraduate specialization in Geomatics at the Universidad del Valle, Cali, Colombia. The quality of her research activity in Environmental Science has been recognized by various awards including the 2024 Editor’s Award from the American Meteorological Society for her reviewing service in the Weather, Climate and Society Journal, the 2023 L’Oreal/UNESCO Women in Science Caribbean Award, the 2023 ICETEX International Experts Exchange Award for study in Colombia. and with her PhD research in drought management also being shortlisted in the top 10 globally for the 2023 Allianz Climate Risk Award by Munich Re Insurance, Germany. Motivated by her faith in God and zeal to positively influence society, Dr. Buckland-Reynolds is also the founder and Principal Director of Chosen to G.L.O.W. Ministries, a Jamaican charitable organization which seeks to amplify the Christian voice in the public sphere and equip more youths to know how to defend their faith.