Problems With Sargassum in the Mexican Caribbean Sea
How should we deal with these massive algal blooms?
∘ When did Sargassum events begin to occur?
∘ How much money has the Mexican tourism industry lost due to Sargassum?
∘ Environmental and ecological impacts
∘ Dealing with the Sargassum problems in the Mexican Caribbean Sea
When did Sargassum events begin to occur?
Since 2011, the changing climatological and environmental conditions have increased the production and transport of floating Sargassum biomass in the Atlantic Ocean [1, 2].
These “Sargassum events” have increased in volume and damage over time, generating severe economic and socio-ecological problems in coastal environments of the Caribbean Sea, the Gulf of Mexico, and West Africa [3, 4, 5].
Current reports estimate that around 20 million metric tons of this algae can accumulate yearly on the beaches of the Caribbean Sea [3].
Although some of these events are part of a natural seasonal phenomenon, the increase in the frequency and strength of Sargassum events has been directly related to a series of factors linked to climate change and globalization [3, 4, 5].
These factors include the increase in seawater nutrients and sea surface temperatures, changes in ocean currents and wind patterns, hurricanes, and maritime traffic [6, 7, 8, 9].
It was originally assumed that the main source of these mass seaweed arrivals was the Sargasso Sea, however, they have also been associated with the regional environmental changes in the Amazon River basin in Brazil [3, 10, 11].
Recent increases in deforestation and the industrialization of agricultural systems have led to increased nutrient runoff from the Amazon River that in turn, favors Sargassum proliferation before it reaches the Caribbean Sea [3].
It has also been theorized that dust from the Sahara desert, along with smoke and ash, being carried into the Atlantic Ocean could be contributing to the Sargassum proliferation [6].
It may sound a bit crazy, but all these factors mentioned above interact remotely from different parts of the Atlantic Ocean and increase the strength and frequency of the Sargassum events along the Caribbean Sea.
How much money has the Mexican tourism industry lost due to Sargassum?
In the Mexican Caribbean, Sargassum events began to appear in late 2014, peaking in 2015, 2018, and 2019 [12, 13].
The accumulation of Sargassum decreases tourist access to beaches, increases cleanup costs, and interferes with waterway transportation and coastal activities.
From an aesthetic point of view, it alters the beauty of the region’s white-sand beaches, and the decomposition of the algae emits an unpleasant odor as it decomposes that drives away tourists [5].
In severe cases, tourists cancel vacations, resulting in the dismissal of personnel and a big hit to the coastal tourist economies (which is the main driver of the economy in the region).
There was a particularly evident decline in the occupancy rates at hotels after the 2018 Sargassum event in the Riviera Maya (2.87 % in the last year as of April 2019) [5].
In an attempt to stem further decline in tourism, the Mexican government invested ~USD 17 million dollars in the removal of 522,226 tons of Sargassum in 2018, and ~USD 2.6 million dollars for the removal of 85,000 tons in 2019 [5, 14].
The hotel industry also spent large amounts removing Sargassum from their beach fronts: in 2018, hotels between Cancun and Puerto Morelos spent USD 128,770 and USD 284,830, respectively, just on staff salaries for cleaning their beaches [15].
Some hotels have also acquired very expensive equipment, including machinery, (~USD 82,000), barriers, to prevent the Sargassum from arriving on the beach (~USD 330 per meter, plus installation, ~USD 50 per meter), and anchors (USD 450 in rock and USD 900 in sand per unit), and boats to transport the collected Sargassum (costing from USD 200,000 to USD 1 million dollars) [5].
In 2019, the State Government of Quintana Roo issued an emergency declaration for all its coastal municipalities, in the face of the “imminent natural disaster” as a result of the ecological damage caused by the Sargassum.
This emergency declaration provides access to federal emergency relief funds, and the government of Quintana Roo expects to gather ~USD 30 million dollars to meet the contingency [16].
This situation has worsened since March 2020, due to the COVID-19 pandemic [5].
If tourism in this region continues to decline, it will lead to severe unemployment, which could bring a range of social problems.
Environmental and ecological impacts
The Sargassum events have diverse impacts on the environment, mostly related to the pollution they produce and the erosion resulting from cleanup activities [5].
The degradation of Sargassum can negatively impact human health. The production of hydrogen sulfide and anhydrous ammonia as a result of the decomposition processes produces neurological, digestive, and respiratory problems [17].
Sargassum produces leachate and particulate organic matter during its degradation that causes Sargassum brown tides (SBT), which deplete oxygen, reduce light, and reduce the water quality in the aquatic environments [18].
From an ecological view, SBT increase the biological oxygen demand, which in turn, produces anaerobic zones that can potentially kill near-shore marine species and damage coastal ecosystems [19].
Since the Yucatan peninsula is made of limestone it is highly susceptible to groundwater pollution.
The nutrients and toxic elements of the Sargassum dumped in the jungle, mangroves, and wetlands, can infiltrate down into the aquifer and pollute the region’s only available source of freshwater.
There is also a potential risk of contamination by heavy metals if Sargassum leachate drains into groundwater when it is dumped into unsuitable land deposits [20].
Additionally, in response to the Sargassum events, there have been documented shifts in tourist preferences toward cenote-related activities, which in turn also increase the risk of contamination of the aquifer [21].
Another often sound impact of the Sargassum relates to its impact on the sea turtles [5].
During the incubation period of the eggs, Sargassum can induce temperatures that are lethal for the embryos and, potentially, can change the sex ratios of hatchling turtles; thus, the demographic balance of future turtles populations can be negatively altered [22, 23].
The most severe negative impacts on sea turtles are probably caused by the activities of collecting and cleaning up the Sargassum.
The beach compaction, caused by heavy machinery, hampers nesting activity and interferes with the emergence of hatchlings from the nest. Vehicle transit may also directly destroy the nests [24].
Dealing with the Sargassum problems in the Mexican Caribbean Sea
Sargassum events are a complex phenomenon that requires including interdisciplinary and transdisciplinary approaches to find a solution to the economic and socio-ecological impacts [4].
It is a priority to identify the challenges of their offshore collection and the implementation of stabilization strategies to avoid degradation of the feedstock [4].
The creation of a circular economy that takes advantage of these events is the best way forward if we are to mitigate damage to the environment and to the local society and economy [5].
Given the high cost of Sargassum contention, removal, and transportation, it is vital to create industries that use large volumes sustainably. In this context, there is a need to forecast the distribution and the arrival of the floating biomass.
The use of satellite imaging techniques and the monitoring of physicochemical parameters in strategic areas are fundamental to help establish effective management policies and mitigate future potential negative impacts [4, 5].
It is also crucial to value the Sargassum biomass [4].
The large volumes of these algae have a great potential to be used for different well-documented purposes, but several elementary questions must first be answered for their efficient exploitation [4, 5]:
- Which are the species found in the Mexican Caribbean and what is their relative abundance?
- What are the regional and local factors that promote the proliferation and accumulation of biomass in the beaches?
- What is the chemical composition of Sargassum species, and how this composition varies spatiotemporally?
The Sargassum’s capacity to absorb heavy metals and its discontinuous and unreliable supply due to seasonal variations are the main constraints to harvesting this alga for commercial exploitation [4].
Finally, Sargassum management requires improving current regional waste disposal practices. In the Yucatan Peninsula, pollution by waste disposal is a serious problem with a strong impact on water quality [25, 26].
If tourism of inland cenotes intensifies, environmental policies in the region should be strengthened to protect these ecologically fragile karst groundwater systems and the local residents who rely on the groundwater for their livelihoods [21].
You can find more information about Sargassum events in the Mexican Caribbean at the following links: [4, 5, 21].
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