Underwater
Meadows
by
UNPLUCKED &
Pablo A. Padilla Jargstorf
A dive through our underwater grasslands, one of our planet’s most incredible ecosystems.
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Underwater Meadows
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When we think of aquatic greenery, we tend to associate this with images of fresh-water plants, undulating in river currents, floating on calm pond surfaces, fencing the margins of lakes and water basins.
But our seas and oceans are also home to some of the most fascinating plant-based ecosystems on our planet, with critical roles to play not just as natural habitats but also for geological and climate stability.
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UNPLUCKED, in collaboration with international artist and designer Pablo A. Padilla Jargstorf (www.jargstorf.com ), would like to introduce you to the key heroes of this story, the Seagrasses, and the wonders of the underwater meadows they create.
Seagrasses derive their name from their similarity to their terrestrial plant relatives, with most species exhibiting long green, grass-like leaves, forming a three-dimensional habitat which allows a wide range of species to inhabit the area. The sometimes vast and dense esplanades of grassland, or underwater meadows they generate can be large enough to be seen from space, as in the case of the Al Wadj Bank in Saudi Arabia (Image 1).
​They are the only known flowering plants able to live in seawater and pollinate while submerged, completing their full life cycle under water.
Like most plants, they are able to manufacture their own food through a process called photosynthesis which requires high levels of light and therefore limits their location to shallow waters, no deeper than 4 metres. The plants’ roots are anchored in mud, sand or fine gravel. This in turn stabilises the seabed, prevents erosion and further helps defend the wider coastline.
Seagrasses have evolved for a long time, estimated to be around 100 million years ago, and can be found on many corners of our planet, from the Tropics to the Arctic Circle (Image 2).
Often referred to as underwater nurseries, these biodiversity heavens provide shelter, feeding stations and breeding grounds for a multitude of marine species, and even protection against infections through the potential antibacterial properties of some seagrasses. The density of the grasses causes the water currents to slow down and allows nutrients to settle, attracting wildlife. These underwater meadows are home to small sea creatures like algae, bacteria, invertebrates such as sponges, polychaete worms and sea anemones, clams, crustaceans, sea horses and other small fish, juveniles of larger fish species, but also to larger ones like many types of fish, sharks, turtles, marine mammals (dugongs and manatees), mollusks (octopus, squid, cuttlefish, snails, bivalves). Some will be permanent residents, while others are just temporary visitors (i.e. during breeding season).
Seagrass meadows are also critical Blue Carbon sinks, coastal ecosystems capable of absorbing and storing large amounts of carbon dioxide, and therefore critical in our efforts to limit the impact of climate change. The numbers are indeed impressive. While seagrasses occupy only 0.1 percent of the total ocean floor,It has been calculated that seagrass is responsible for 15% of the ocean’s total carbon absorption (Reference 3).
In addition, underwater seagrass in coastal areas appears to trap plastic pollution in natural bundles of fibre known as “Neptune balls”, made of natural aggregates of vegetal fibres and plastic residues intertwined by seawater motion, eventually leaving the marine environment through beaching (reference 4). It remains unclear whether collecting the plastic damages the seagrass itself.
Like all things in nature, seagrass meadows are a fine equilibrium of life. The disturbance of one or more aspects in these ecosystems can cause imbalances that can drive them to stagnation or make them disappear altogether. Unfortunately, we humans seem to be once again at the centre of the threat to these amazing havens, with overfishing, mechanical damage (dredging of the seabed) and discharge of both sewage and chemical pollution having been proven to have devastating effects. Globally, it is estimated that 30,000km2 of seagrass has been lost in the last couple of decades which is equal to 18% of the global area.
In May 2022, the General Assembly recognised the value of these ecosystems and adopted A/RES/76/265 proclaiming 1 March as World Seagrass Day UN World Seagrass Day to raise awareness of its importance, inform, and encourage support for campaigns and action (5).
About the Artwork
Seagrasses are not a taxonomically unified group, but rather an ecological one that arose through separate paths of evolution and includes several different families.
All the depicted seagrasses in our Underwater Meadows collection share a similar structure, growing and expanding through a rhizome, an underground stem from which all the foliage, flowers, fruits and seeds appear at regular intervals in nods, with short roots keeping the plants anchored on the sea bed.
Like other ecosystems on our planet, seagrass meadows are subject to changes, with species composition, extent and biomass of seagrass meadows varying both seasonally and between years.
Amongst the four different species of seagrasses depicted in our Underwater Meadows collection, we have included some which have breached their original natural habitats and are considered invasive species, competing and in some cases even taking over established habitats. Our aim was to highlight the impact on the wellbeing of these ecosystems of both global marine traffic and critical events linked to climate change, such as the continuous rise in sea surface temperature and salinity.​​
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Each seagrass was carefully hand-drawn. This series of illustrations was created using only watercolour pencils and graphite pencils.
Halophila Stipulacea
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Halophila stipulacea is a species of seagrass native to the Indian Ocean that spread into the Mediterranean after the opening of the Suez Canal in 1869, and continued to spread to the Caribbean (first reported in 2002), making it an invasive plant. In the Mediterranean, many invasion sites were recorded over the last 150 years, but the areas occupied have remained small and highly restricted. In contrast, in the Caribbean, the invader has occupied vast areas and has done so rapidly. The impact of climate change on marine waters (what is now being defined as a tropicalization, increasing salinity and temperature levels) may see this expansion accelerate even further and across all recorded locations. Such expansion across different sea conditions has been possible due to its inherent ability to adapt to a wide range of ecological conditions, including salinity, light intensity, depth, temperature, substrates, and nutrient levels. Able to tolerate different salinity levels, able to grow in water temperatures ranging from 17 to 42, it also presents two previously unidentified photosynthetic pigments in high concentrations that may indicate a possible biochemical adaptation to different irradiance levels to optimise growth in deeper areas.
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Zostera Noltii, commonly known as dwarf eelgrass, can be found in shallow coastal waters across many latitudes. It plays an important role in the intertidal and shallow subtidal ecosystems of estuaries, bays and lagoons. Its presence has been recorded in the eastern Atlantic Ocean along the coasts of Europe as far north as Norway, Sweden and the Baltic Sea or Dublin Bay. In the Mediterranean Sea and the Black Sea, it is restricted to the brackish conditions found in lagoons and estuaries. It is the only species of seagrass found in the Caspian Sea and the Aral Sea.It also grows in Morocco, Mauritania, and the Canary Islands. It grows intertidally on fine sandy or muddy substrates and can tolerate various levels of salinity. It tends to grow in a band higher up the beach than Zostera marina beds and is often mixed with other seagrasses (Ruppia spp.). It grows subtidally in deeper water when it is in low salinity or brackish water in estuaries and lagoons. It is adversely affected by high nutrient levels and cloudy water.​​
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Thalassia hemprichii, called Pacific turtle grass or Sickle seagrass, is native to the shores of the Indian Ocean, the Red Sea, and the western Pacific Ocean. It is widely known for attracting Green Turtles (Chelonia mydas) as a key feeder to these pastures, hence its colloquial name. The growth rate of Turtle grass increases with CO2 enrichment, and it can tolerate lowered light conditions caused by algal blooms, allowing for it to respond positively to ocean acidification and other disturbances. However, a wide range of disruptive anthropogenic activities in coastal zones such as construction on the coastline, tourism, near-shore fishing and aquatic activities can have long-lasting negative effects on Thalassia hemprichii seagrass beds and coastal ecosystems. Thalassia hemprichii has a secondary metabolite mechanism which is used to counteract predator attack and to survive in the environment. Many secondary metabolite compounds have been used as medicines or models to make new medicines. Some of them are antimicrobial and antioxidant.Some of the biological activities of the secondary metabolite are anticancer, antibacterial, antioxidant and antifungi. Traditionally, this seagrass has been utilized, among others, for making baskets, filling mattresses, insulating roofs, as fertiliser, and burnt to obtain salt.
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Halophila Spinulosa, or Fern seagrass, is found only in the South China Sea region including the coasts of northern Australia. It can tolerate a range of conditions so it is found in a wide range of habitats. Small in size, Fern seagrass have lower photosynthetising demands and therefore lower light requirements for growth and survival. This enables them to survive at greater depths than other species. However, being small does have its drawbacks, not allowing these seagrasses to store nutrients for long periods of time. Evolutionarily, they have managed to compensate for this by relying on sexual reproduction and the dispersal of seeds to recover quickly once a disturbance or stress has abated. This ability to recolonise quickly after disturbance has resulted in Halophila species being referred to as' colonising’ species.
REFERENCES
1- https://earthobservatory.nasa.gov/images/8593/al-wadj-bank-saudi-arabia
2- https://www.researchgate.net/publication/223235046_Global_seagrass_distribution_and_diversity_A_bioregional_model
3- https://ocean.si.edu/ocean-life/plants-algae/seagrass-and-seagrass-beds#:~:text=As%20a%20result%2C%20seagrasses%20can,and%20the%20list%20goes%20on
4- https://www.nature.com/articles/s41598-020-79370-3
5- https://www.un.org/en/observances/seagrass-day
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ADDITIONAL LINKS OF INTEREST
https://www.unep.org/resources/report/out-blue-value-seagrasses-environment-and-people
https://www.projectseagrass.org
https://www.wildlifetrusts.org/habitats/marine/seagrass
https://www.themarinediaries.com/tmd-blog/savannahs-of-the-sea​
UNPLUCKED MOSAICS
We like to consider Unplucked a collection of stories, boxes that once open transport you closer to one of those natural wonders we share our lives with. In the spirit of those cabinets of curiosities treasured by so many in the past.
All these stories are unique in themselves, and at the same time share a common place and a connecting thread.
To reflect that, UNPLUCKED brings you our own MOSAICS. Like looking through the lens of an observation instrument, before focusing on a particular corner of our world. Encapsulating both our curiosity to discover and our eagerness to collect.
Generated from each one of our collections, but all sharing a deep connection, MOSAICS distill some of the essence of UNPLUCKED.
