Underwater
Meadows
A dive through our underwater grasslands, one of our planet’s most incredible ecosystems.
by
UNPLUCKED &
Pablo A. Padilla Jargstorf
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Underwater Meadows
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Seagrasses form dense underwater meadows which are among the most productive ecosystems in the world. They provide habitats and food for a diversity of marine life comparable to coral reefs. This includes invertebrates like shrimp and crabs, cod and flatfish, marine mammals and birds. They provide refuges for endangered species such as seahorses, turtles, and dugongs. They function as nursery habitats for shrimps, scallops and many commercial fish species. Seagrass meadows provide coastal storm protection by the way their leaves absorb energy from waves as they hit the coast. They keep coastal waters healthy by absorbing bacteria and nutrients, and slow the speed of climate change by sequestering carbon dioxide into the sediment of the ocean floor.
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Halophila Stipulacea
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Halophila stipulacea is a species of seagrass in the Hydrocharitaceae family. It is native to the Indian Ocean that spread into the Mediterranean after the opening of the Suez Canal. This seagrass is widespread through the Gulf of Aqaba. Recently it has arrived in the Caribbean where it is also spreading.
It is suggested that the expansion of H. stipulacea from the Red Sea into the Mediterranean Sea was a result of the opening of the Suez Canal in 1869. The invasion into the Mediterranean was first documented in 1894.
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The plant H. stipulacea has the ability to adapt to a wide range of ecological conditions, including salinity, light intensity, depth, temperature, substrates, and nutrient levels. Particularly, it is considered a euryhaline species due to its ability to tolerate different salinity levels. In fact, H. stipulacea can withstand both low and high salinity levels, ranging from 24 to 70 PSU. Also, it has the ability to adapt to a wide spectrum of irradiance levels, leading to a high plasticity in its photosynthetic structures, which enables more efficient light absorption . Furthermore, H. stipulacea typically grows in shallow depths of 1–6 m; however, it can also be found in deeper meadows at 20–70 m and therefore can tolerate a large range of depths. And two unidentified photosynthetic pigments were found in high concentrations in H. stipulacea, which may indicate a possible biochemical adaptation to different irradiance levels to optimize growth in deeper areas. It has been reported that H. stipulacea also grows across a wide range of temperatures, from 17 to 42 °C. Moreover, this seagrass is found in marine sublittoral sediments living on different substrates of sand, silt, mud, and coral rubble. Finally, H. stipulacea has a limited capacity for the uptake of nitrate, while it has a high capacity and efficiency for the uptake of ammonium. Interestingly, nitrogen fixation by associated diazotrophic epiphytes compensates for the nitrogen limitation of this seagrass under low nitrogen conditions, providing an advantage when competing for resources with other seagrass species. All of these characteristics contribute to the invasive nature of this species, giving it the ability to outcompete other seagrasses.
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Source: Wikipedia; National Center for Biotechnology Information.
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Description
Zostera noltii has a creeping rhizome that runs along under the surface of the seabed. Groups of two to five strap-shaped leaves grow out of nodes on the rhizome and each node also bears a tuft of up to four short roots that anchor the plant in the sediment. The leaves have three irregular, longitudinal veins and blunt, notched ends. They are up to 22 cm (9 in) long and contain air spaces which make them buoyant. Several separate male and female flowers grow on a short, spear-shaped lateral stem. The smooth white seeds develop inside a green capsule with membranous walls and are about 2 mm (0.08 in) long.
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Distribution and habitat
Zostera noltii is found in the eastern Atlantic Ocean along the coasts of Europe as far north as Norway, Sweden and the Baltic Sea.[1] Around the British Isles it grows extensively in the Firths of Moray and Cromarty, the Wash and the Thames Estuary. In Ireland substantial quantities are found in Strangford Lough,[5] Dungarvan Harbour and 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.[6] 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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Source: Wikipedia.
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Thalassia hemprichii, called Pacific turtlegrass or Sickle seagrass, is a widespread species of seagrass in the genus Thalassia, native to the shores of the Indian Ocean, the Red Sea, and the western Pacific Ocean. Its growth rate 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.
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The vegetation of Thalassia hemprichii seagrass is the area of food hunting, breeding and habitat of several plants and animals. Anthropogenic activities in coastal zones such as construction on the coastline, tourism, near-shore shing and aquatic activities can have long-lasting negative effects on Thalassia hemprichii seagrass beds and coastal ecosystems. Thalassia hemprichii has 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.
Seagrass is a commodity that has been widely used by community both traditionally and modern. Traditionally, seagrass has been utilized, among others, for making basket, burned to get the salt, soda or warmers, for filling mattresses, as thatched roofs, for compost and fertilizer, used for sound insulation and temperature, can in lieu of yarn in making nitrocellulose and so on. While modern use is as waste filters, beach stabilizers, materials for paper, fertilizer and fodder, as well as medicinal ingredients.
Seagrasses are also known to have the potential to be used as pharmaceutical raw materials. Kannan et al. explained that Thalassia hemprichii has bioactive potential as antioxidants and contain compounds phenolic group. Thalassia hemprichii collected from Pamban, Tamil Honey, India is known to contain potential bioactive compounds as antibacterial, antifungal, anti protozoa, antiviral, antifertility and ingredients drugs that affect cardiovascular system.
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Antimicrobial potential of Thalassia hemprichii seagrass
Seagrasses produce antimicrobial/antibacterial compounds to reduce or control the microbial growth. The secondary metabolite that is produced by many organisms and it is known to have many biological activities that can be utilized by human being.
Some of the biological activities of the secondary metabolite are anticancer, antibacterial, antioxidant and antifungi. The technique to isolate the secondary metabolite compound of a particular natural material is known as extraction. Extraction is one of substance separation processes that are needed from a plant material.
The method of extraction relies on the solubility of the compound to be extracted in the solvent used. The success of the extraction process is also influenced by some factors so that to need to carefully choose the method of extraction used to extract the secondary metabolite compound.
The extraction of Thalassia hemprichii which is continued by doing phytochemical test shows that Thalassia hemprichii has some bioactive compounds which can become anticancer, antibacterial and antifungal substances. Some research shows the advantage of Thalassia hemprichii extract as antibacterial.
The result of bioassay test shows that the extract and fraction of Thalassia hemprichii has the potential of S. aureus (gram-positive) antibacterial while on E. coli bacteria (gram-negative), it does not have inhibitory power.
Other research shows that phytochemical test done shows the extracts of Enhalus acoroides and Thalassia hemprichii contain bioactive compounds of the types of flavonoid, alkaloid and steroid.
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Source: Wikipedia; Scialert.net.
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Description
This beautiful seagrass has tiny leaves that grow in opposite pairs on a long thin stem, forming a flat fern-like overall shape. 10-20 pairs of leaves may form on the stem, new leaves growing from the tip while older leaves at the bottom drop off. Each leaf is about 2cm long and 0.4cm wide, with tiny serrations on the edges and a small one-sided fold at the base. (Some books refer to these leaves as leaflets). The entire stem is about 4-6cm long. Its rhizomes (underground stems) are thin, sometimes woody.
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Fern seagrass has separate male and female plants. The flowers form at the junction where each tiny leaf attaches to the central stem. There may be several flowers on a single stem. The tiny fruits are flask-shaped and may contain up to 30 tiny seeds.
Source: Wildsingapore.com​​
