Sargassum

Sargassum Fertilizer Transfers Heavy Metals to Vegetables

Nederlands below.

 

A joint experiment between WWF-Mexico and STINAPA Bonaire found that vegetables grown in soil enriched with sargassum had higher levels of arsenic and cadmium, heavy metals that can be toxic to humans and animals.  Researchers warn that sargassum should not be used to compliment animal fodder, nor used as a fertilizer for consumables until further investigated.

Sargassum influx in Lac Cai

Sargassum is a floating brown seaweed that plays several important ecological roles. Although sargassum occurs naturally, due to shifting ocean currents and increased pollution, the Atlantic is experiencing episodic sargassum blooms.  Since 2011, the Caribbean has experienced several significant sargassum events, leading to a number of social, environmental and economic issues, particularly in the hospitality and fisheries sectors.  Sargassum influxes threaten the already fragile coral reefs, mangroves and seagrass beds.

The Study

To better understand the impact of disposed sargassum, a joint project between WWF-Mexico and STINAPA Bonaire explored whether sargassum-enriched fertilizer promoted faster seed development and if any heavy metals were detectable in the vegetables after harvest. Two planter boxes were used, one filled with 50/50 dried sargassum and potting soil and one with only potting soil.

 

The Results

Sargassum enriched soil testing set up

Although, in general, there appeared to be no significant physical differences (shape or quantity of vegetable production) between plants grown with or without the presence of sargassum, samples analyzed at the Radboud University laboratory found that arsenic levels were higher in vegetables grown in soil with sargassum. More specifically, bok choy had 37 times, zucchini 21 times, spinach 4 times and soil 13.5 times more arsenic than their counterparts grown in plain potting soil.  Cadmium levels were also higher in plants grown in sargassum enriched soil, with chemical analysis showing bok choy having 2.5 times, zucchini with 3 times, spinach with 1.3 times and soil with 2.7 times the amount of cadmium than samples without sargassum enrichment.

Furthermore, a Wageningen University and Research report titled “Opportunities for valorization of pelagic Sargassum in the Dutch Caribbean”, analyzed sargassum from the same source and found it to have high levels of heavy metals.  This full report is available from the Wageningen University and Research website (https://edepot.wur.nl/543797).

Implications

Decomposing sargassum in water

The health implications of these findings are still unclear. Arsenic can take several forms, namely organic and inorganic, where organic levels can be much higher before negative impacts are observed in people.  It should be noted that the European Food Safety Authority (EFSA) has not yet set official thresholds for arsenic. In fact, the EFSA Panel on Contaminants in the Food Chain (CONTAM) published data in 2010 which stated that there are no ‘safe’ levels of arsenic.  Long term ingestion of inorganic arsenic has been connected to skin lesions, cancer, developmental toxicity, neurotoxicity, cardiovascular disease, abnormal glucose metabolism and diabetes (CONTAM, 2010). More research is needed to understand impacts of these higher levels of heavy metals and the long -term effects when ingested.

As influxes of sargassum are becoming increasingly common, countries and individuals will search for innovative ways to use and dispose of this nuisance. Already, some reports have highlighted its use as a building material, animal fodder or fertilizer for home gardens. Until the health implications are more widely understood, it would be wise to limit sargassum use to non-consumable options.  This leaves the door open for sargassum to be used as building material (dried and pressed into bricks), biofuel or perhaps fertilizer for decorative plants or construction material, such as bamboo.

Submitted by: Jessica Johnson and Sabine Engel, researchers for STINAPA. This project was funded by WWF-Netherlands and received support from Radboud University.

 

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Nederlands

Zware metalen in sargassum-mest worden door planten opgenomen

De bevindingen van een experiment uitgevoerd door STINAPA in het kader van een gezamenlijk project met WWF Mexico tonen aan dat grond verbeterd met sargassum hogere arseeen (As) en cadmium (Cd) waardes heeft. Arseen en cadmium zijn zware metalen die schadelijk zijn voor mens en dier. De onderzoekers waarschuwen dat sargassum niet gebruikt moet worden als aanvulling voor dier voedsel of als bemesting van groenten, voordat verder onderzoek heeft plaatsgevonden.

Sargassum bij Lac, Bonaire

Sargassum is een drijvend bruinwier dat een aantal belangrijke ecologische functies vervult. Sargassum komt natuurlijk voor, maar door veranderde zeestromingen en toegenomen vervuiling komen er nu periodieke sargassum ‘blooms’ (woekeringen) voor. Sinds 2011 zijn er in de Caraïben verschillende heftige sargassum ‘blooms’ geweest die gevolgen hadden op sociaal-, milieu- en economische gebied, voornamelijk in de horeca, toeristen en visserij sector. De periodieke sargassum aanvoer bedreigt daarnaast ook de toch al kwetsbare koraalriffen, mangroves en zeegras bedden.

De studie

Om meer te weten over het lot of de mogelijke toepassing van het afgevoerde sargassum werd in een gezamenlijk WWF Mexico – Bonaire project door STINAPA onderzocht of planten beter ontkiemden op grond waar sargassum-mest aan toe was gevoegd, en of de zware metalen voor kwamen in de geoogste planten. Twee plantenbedden werden klaargemaakt: één met potgrond, en één met 50/50 potgrond en gedroogd sargassum.

De resultaten

Het kweek experiment

Over het algemeen was er geen zichtbaar verschil tussen de planten gekweekt in de twee bedden maar monsters geanalyseerd aan de Radboud Universiteit toonden hogere arseen waardes aan in groentes uit de bedden met sargassum. Om precies te zijn, bok choy had 37 keer, zucchini 21 keer, malabar spinazie 4 keer, en het groeimedium potgrond sargassum 13.5 keer meer arseen dan de planten en grond uit de bedden met alleen potgrond. Het cadmium gehalte was ook hoger in planten die gekweekt waren in de ‘sargassum’ grond. Bij bok choy was dat 2,5 keer zoveel, zucchini 3 maal spinazie 1,3 maal en het medium 2,7 keer de hoeveelheid cadmium dan de controle planten.

Aan de Wageningen Universiteit werden monsters sargassum van dezelfde bron onderzocht in het kader van de studie “Opportunities for valorization of pelagic Sargassum in the Dutch Caribbean”, en werden ook hoge waardes voor zware metalen aangetroffen. Het volledige rapport is te vinden op de site van Wageningen University and Research (https://edepot.wur.nl/543797)

Implicaties

De gezondheids implicaties zijn nog niet helemaal duidelijk. Er zijn verschillende organische en anorganische vormen van arseen. Pas bij hogere waardes van organisch arseen worden negatieve gevolgen waargenomen voor mensen. De Europese Voedsel Veiligheid authoriteit (EFSA) heeft nog geen drempelwaardes vastgesteld. In feite publiceerde het EFSA Panel Verontreinigingen in de Voedselketen (EFSA Contaminants in the Food Chain (CONTAM)) in 2010 gegevens en stelde dat er geen ‘veilige’ arseen waarden zijn. Verband is gelegd tussen langdurige blootstelling aan anorganisch arseen en huidafwijkingen, kanker, ontwikkelingstoxiciteit, neurologische toxiciteit, cardiovasculaire ziektes, abnormale glucose vertering en diabetes (CONTAM, 2010). Er is meer onderzoek nodig om te bepalen wat de effecten zijn van deze zware metalen bij langdurige blootstelling.

Nu het op de kust ophopen van sargassum steeds vaker voorkomt zoeken landen en organisaties naar innovatieve manieren om van deze sargassum-overlast af te komen. Er zijn al publicaties die hebben aangegeven dat sargassum gebruikt kan worden als bouwmateriaal, veevoer of als huis & tuin grondverbeteraar. Maar zolang de gezondheidseffecten niet duidelijk zijn is het verstandig om sargassum niet te gebruiken voor voedselproductie. Het biedt dus alleen mogelijkheden voor bouwmateriaal (gedroogd en in blokken samengeperst), biofuel en misschien bemesting voor decoratieve planten of bouwmateriaal zoals bamboe.

Samengesteld door Jessica Johnson en Sabine Engel, onderzoekers voor STINAPA. Dit project is gefinancierd door WWF – Nederland, met bijdrages van de Radboud Universiteit.

 

Published in BioNews 54

 

Date
2022
Data type
Media
Theme
Research and monitoring
Geographic location
Bonaire

Brown Tides: Assessing the Past, Present, & Future State of Sargassum in Aruba Through a Mixed Methods Approach

ABSTRACT:

In the last decade, Caribbean shores have been inundated with a floating seaweed known as Sargassum. In large amounts, Sargassum threatens biodiversity by suffocating nearshore ecosystems and decreases tourism levels due to its nauseating smell, putting small island environments and economies at risk. With little to no research conducted on the monitoring and cleanup opportunities of Sargassum in Aruba, I aimed to fill that gap with this thesis by identifying susceptible influx areas and potential impacts. In collecting both quantitative data using geographic information systems (GIS) and Sargassum specific monitoring software, as well as qualitative data through interviews, my research has explored the potential social, economic, and environmental consequences or opportunities that Aruba may face. I used this data to further visualize the spatial distribution and impacts of Sargassum such that my research findings could be applied within the larger Caribbean context

Date
2022
Data type
Research report
Theme
Research and monitoring
Document
Geographic location
Aruba

The effect of Sargassum on settlement of Diadema antillarum larvae around Saba

Abstract 

Before its mass-mortality in the 1980’s, Diadema antillarum was the most important benthic herbivore on Caribbean reefs. Since then, reefs have experienced an increase in turf/macroalgae abundance. Despite the approximate 40 years that have past, natural recovery is slow and variable. Therefore efforts are taken to boost D. antillarum recovery artificially. Several bottlenecks for recovery have been found, but in the last decade a new potential problem has risen: massive influxes of floating Sargassum species. Studies have shown that algae or its biofilm can induce sea urchin settlement to a certain extent, but no in vivo experiments have been conducted for D. antillarum. Here we investigated if these Sargassum floats interfere with the recruitment of D. antillarum by measuring the abundance of D. antillarum settlers in submerged and floating, rinsed and unrinsed Sargassum units and comparing values with a positive control. While the amount of data collected with the low sample sizes did not suffice to answer the research question in any statistically significant manner, hypothesis could be formulated.   

D. antillarum certainly is attracted to sargassum patches, whether as post-settler only or also as settler is however still debatable. Cues by conspecifics could possibly play a role in increased settlement in Sargassum, blurring the effect of Sargassum solely. A large variation in D. antillarum abundance was found for the unrinsed submerged treatment, which was possibly the result of migration from nearby existing ecosystems with older D. antillarum into the experimental units, or it was an artefact of the low sample size. To confidently distinguish signal from noise in a similar study, some alterations to the research design need to be made and drifting sargassum patches need to be sampled to get a sense of D. antillarum settler abundance on naturally occurring Sargassum. 

Date
2021
Data type
Research report
Theme
Research and monitoring
Report number
Thesis
Geographic location
Saba

Special Edition: Transboundary Species

There has been a recent increase in public awareness of environmental issues as the effects of climate change have become ever more noticeable in our daily lives. As we enter a new decade, it becomes useful to review what conservation efforts have worked so far, and take inventory of what efforts will be required for the future. Starting with the constitutional referendum creating the Caribbean Netherlands (Bonaire, St. Eustatius and Saba (BES), the response to conservation challenges of all six Dutch Caribbean islands have varied. Since 2010, the BES islands have seen an overall increase in funding support and conservation actions, and therefore presumably also saw greater improvements when compared to Aruba, Curaçao and Sint Maarten, though clearly not enough (Sanders et al, 2019).

The goal of this Transboundary Species special edition of BioNews is to provide an update on the latest published research results and highlight the need for transboundary protection. These species know no boundaries, and thus move between the Dutch Caribbean islands and beyond. Their protection will require broadscale conservation efforts which cover the entire Caribbean, including the six Dutch Caribbean islands. Collaboration between all six islands is of the utmost importance. This is one of the Dutch Caribbean Nature Alliance’s (DCNA) main goals: working together and sharing skills, knowledge and resources to maintain a solid network and support nature conservation in the entire Dutch Caribbean.

 

Date
2019
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
Saba bank
St. Eustatius
St. Maarten
Author

Mapping Sargassum on beaches and coastal waters of Bonaire using Sentinel-2 imagery

Sargassum is a genus of brown macroalgae or seaweed that can be found in shallow waters or free floating in the ocean. Sargassum patches on the open sea drift along sea current and can aggregate into larger Sargassum rafts or long slicks. Sargassum seaweeds that accumulate in the Sargasso Sea originate from The Gulf of Mexico where it blooms in the spring. This Sargassum bloom is induced by nutrient loadings from land that are discharged via the Mississippi River into the sea. Sargassum is not directly harmful on sea, in fact diverse biotic communities and animal species such as fishes, sea turtles and invertebrate depend on the seaweed for shelter and food source. However, Sargassum can potentially damage coastal ecosystems such as mangroves and seagrass beds if it accumulates on the coast. Therefore, monitoring of pelagic Sargassum is of great importance for managing coastal ecosystems.

An unprecedented amount of pelagic Sargassum invaded the Caribbean islands in the summer of 2011. Masses of Sargassum seaweed piled up on beaches trapping sea turtles and releasing high concentration of toxic hydrogen sulphide gas when it decomposes. Beside sea turtles, local tourism was also affected by the Sargassum beaching which led to temporarily closure of hotel resorts and high-cleaning costs of beaches. Climate change and increasing nitrification of seas might indicate that the amount of Sargassum in the Caribbean Sea might increase substantially within the near future.

The main objective of this research is to use multispectral data to map and classify Sargassum patches on the east coast of Bonaire. Accurate Sargassum maps will be useful for the coastal management to assess the location and coverage of Sargassum mats that have washed up along the shores and beaches. Consequently, the extent to which these Sargassum seaweeds affect nearshore benthic habitats and mangrove ecosystems in east Bonaire can be evaluated too.

Date
2019
Data type
Other resources
Theme
Research and monitoring
Geographic location
Bonaire
Author

Sorobon and Lagoen covered by sargassum

March 6, 2018

Sorobon en Lagoen overspoeld door sargassum.

Sinds gisteren is er een enorme invasie van sargassum wier aan de oostkust. Sorobon en Sorobon zijn de meest getroffen gebieden momenteel. Vanwege dreiging van zware stormen in het noorden van het Caribisch gebied, is de verwachting dat er meer sargassum in de komende dagen naar Bonaire afdrijft.

Sargassum is een bruine alg die de drijvende zeewiermatten vormen die bekend staan ​​als de Sargassozee in de Atlantische Oceaan. In de open oceaan zijn deze drijvende matten buitengewoon divers en vormen ze een belangrijk leefgebied voor meer dan 250 soorten vissen en ongewervelde dieren, waarvan er veel nergens anders voorkomen. Soms breekt een stuk van de mat af en reist naar het Caribisch gebied waar het op onze kusten terechtkomt.

Zodra het sargassum de kust raakt, wast het op, of hoopt het op, zinkt en rot. Wanneer het gaat rotten, wordt alle zuurstof opgebruikt en vormen zich waterstofsulfide, beiden veroorzaken verstikking bij de zeedieren. Veel babyschildpadden, kreeften en vissen kunnen hierdoor worden gedood. We hebben hulp nodig om zoveel mogelijk levende wezens uit de sargassum te verwijderen en ze te verplaatsen.

retrieved from Bonaire nieuws on 22 March 2018

Date
2018
Data type
Media
Theme
Education and outreach
Tags
Geographic location
Bonaire

The Protection and Management of the Sargasso Sea: The golden floating rainforest of the Atlantic Ocean

The Sargasso Sea is a fundamentally important part of the world’s ocean, located within the North Atlantic sub-tropical gyre with its boundaries defined by the surrounding currents. It is the only sea without land boundaries with water depths ranging from the surface coral reefs of Bermuda to abyssal plains at 4500 m. The Sargasso Sea’s importance derives from the interdependent mix of its physical structure and properties, its ecosystems, its role in global scale ocean and earth system processes, its socio-economic and cultural values, and its role in global scientific research. Despite this, the Sargasso Sea is threatened by a range of human activities that either directly adversely impact it or have the potential to do so. Being open ocean, the Sargasso Sea is part of the High Seas, the area of ocean that covers nearly 50% of the earth’s surface but which is beyond the jurisdiction and responsibility of any national government, and as such it enjoys little protection. To promote the importance of the Sargasso Sea, the Sargasso Sea Alliance was created under the leadership of the Government of Bermuda in 2010. This report provides a summary of the scientific and other supporting evidence for the importance of the Sargasso Sea and is intended to develop international recognition of this; to start the process of establishing appropriate management and precautionary regimes within existing agreements; and to stimulate a wider debate on appropriate management and protection for the High Seas.

Nine reasons why the Sargasso Sea is important are described and discussed. It is a place of legend with a rich history of great importance to Bermuda; it has an iconic ecosystem based upon floating Sargassum, the world’s only holopelagic seaweed, hosting a rich and diverse community including ten endemic species; it provides essential habitat for nurturing a wide diversity of species many of which are endangered or threatened; it is the only breeding location for the threatened European and American eels; it lies within a large ocean gyre which concentrates pollutants and which has a variety of oceanographic processes that impact its productivity and species diversity; it plays a disproportionately large role in global ocean processes of carbon sequestration; it is of major importance for global scientific research and monitoring and is home to the world’s longest ocean time series of measurements; it has significant values to local and world-wide economies; and it is threatened by activities including over-fishing, pollution, shipping, and Sargassum harvesting.

Apart from over-fishing many of the threats are potential, with few direct causal relationships between specific activities and adverse impacts. But there is accumulative evidence that the Sargasso Sea is being adversely impacted by human activities, and with the possibility of new uses for Sargassum in the future, the lack of direct scientific evidence does not preclude international action through the established precautionary approach. The opportunity to recognise the importance of the Sargasso Sea and to develop and implement procedures to protect this iconic region and the wider High Seas should be taken before it is too late. 

Date
2011
Data type
Research report
Theme
Governance
Author