Seagrass species

• The most commonly found species of seagrasses in Puerto Rico are easily distinguished by their distinctive traits, such as:

• Size and shape of the leaves

• Whether the roots are near the surface or lie deep

• Location within their habitat

• These five seagrass species have dis nc vely shaped leaves, roots, flowers and fruits.

• Their tolerance to salinity and depth also varies according to where they grow.

• Addi onal topic: If the instructor desires, basic botany terms may be reviewed here (types of leaf, root, flower, etc.)

Turtle grass ( Tu Thalassia ass a testudinum m)

• Turtle grass is the seagrass most found in Puerto Rico and the Caribbean.

• This seagrass is the preferred food source for green sea turtles.

• It is generally found at a depth up to 10 m (33 feet), but in clear waters, it can grow at depths of around 30 m (98 feet).

• It has long, flat leaves.

• It has a deep root system.

• Turtle grass is a foodsource to many herbivore species such as the green sea turtle (Chelonia mydas), an endangered species.

• However, other smaller herbivores feed on these grasses; therefore, leaf ps are o en jagged from bite (herbivory) marks.

• Turtle grasses grow in short clusters, are flat and ribbon-like and measure between 0.4 and 1.8 cm (0.16 and 0.71 inches) in width. They can measure up to 30 cm (approx. 12 inches) long. The leaf ps are rounded.

• It produces big, pale greenish-white flowers and seed pods that frequently wash up on the beach.

• This seagrass has a horizontal rhizome that buries itself in the sediment to a depth of up to 25 cm (10 inches).

• Turtle grass can tolerate exposure to direct sunlight and air during low de.

Manatee grass ( anatee grass Ma Syringodium ass m filiforme me)

• Manatee grass is the second most common seagrass found in Puerto Rico.

• This seagrass is the primary source of food for manatees.

• The leaves are long, fine and cylindrical, like spaghetti noodles.

• It can grow at depths of up to 30 m (100 feet).

• Manatee grass is an important source of food for many herbivorous species, including the An llean manatee (Trichechus manatus), an endangered species.

• This grass is frequently found in stable environments, since it does not tolerate low salinity condi ons. In Puerto Rico, it is usually found mixed with turtle grass, or in monospecific meadows.

• The leaves are fine and cylindrical, measure between 0.8 and 2 mm (0.03 and 0.08 inches) and up to 50 cm (approx. 20 inches) in length and break easily.

• Because the blades have less surface area than other seagrass species, manatee grass is not a good compe tor for sunlight (necessary for photosynthesis). This grass is a good colonizer in high energy environments since their leaves offer li le resistance to surf condi ons.

Shoal grass ( oal grass Sh Halodule ass le wrightii tii)

• Shoal grass is a colonizing seagrass that thrives in shallow soils.

• It tolerates environmental variations well.

• The leaf is slender and flat and has two or three pointy tips.

• It can be found at depths of around 5 m (16 feet), and in clear waters, it can reach depths of approximately 30 m (100 feet).

• Shoal grass is characterized by having a flat leaf that is narrower than turtle grass. This can measure between 4-10 cm (1.6-4 inches) in length and 0.2-0.5 cm (0.1-0.2 inches) in width.

• Leaves and roots arise from nodes along the rhizome. Each nodule sprouts between 2 to 5 roots growing downward and several leaves growing upwards.

• The roots are not ramified.

Paddle grass ( ddlePa Halophila rass a decipiens ns)

• Paddle grass is not commonly found in Puerto Rico.

• They are small and fragile.

• Their leaves resemble little paddles or oars.

• They grow in depths around 30 m (100 feet), and in clear waters, they can grow at depths of up to 50 m (165 feet).

• Out of the seagrass species found in Puerto Rico, this is the species that least resembles terrestrial grasses, since it doesn’t have a sheath covering the base of its leaves (unlike turtle grass, for instance, which does have this sheath).

• This species is characterized by it pe olate and oval-shaped leaves, which feature a serrated border and are borne in pairs above the rhizomes (horizontal stalks) stemming from a pair of scale-like structures. These leaves can reach 2.5 cm (0.98 inches) in length and 0.6 cm (0.24 inches) in length.

• This is an annual plant (it completes its life cycle within a year) that is usually found in deeper waters (approx. 30 – 100 m depth, and in clear waters, it can grow at depths of 50 m, or 165 feet). It has slender rhizomes (horizontal stems) that run along the ground surface and features a root descending from each node.

Widgeon grass ( Wiidgeon Ruppia grass on a maritima ma)

• Widgeon grass is not very common in Puerto Rico.

• This grass lives in shallow areas and tolerates a wide range of salinity.

• The leaves are very long and fine.

• Widgeon grass is an important source of food for migratory birds.

• Widgeon grass is a species with wide geographical distribu on, and which thrives in coastal lagoons, estuaries and bays.

• Although it is usually found in brackish or low-salinity waters, it has a high tolerance for dras c changes in salinity. Several botanists do not consider widgeon grass a seagrass but rather a freshwater plant which tolerates salinity well (Den Hartog, 1970).

• Widgeon grass leaves are very fine (0.1 cm – to 1 mm) and measure approximately 10 cm (approx. 4 inches) in length.

• Several branches grow out of the grass stem, which can reach up to 0.5 m (1.6 feet) in length. Its anchoring system consists in fine rhizomes (or horizontal stems) and roots. Its flowers are very small (3-5 mm, or 0.12-0.20 inches). Its fruits are dark, pear-shaped and grow in bunches.

• Seagrass meadows, mangrove forests and coral reefs are interconnected, and they all depend on one another.

• Seagrass meadows, mangrove forests and coral reefs are the three main marine ecosystems in Puerto Rico. These ecosystems are interconnected, and each exerts a stabilizing effect on the environment. We will men on some examples of how these ecosystems connect with each other and depend on one another.

• The ecosystem closest to the coastline is the mangrove forest, which has the important func on of trapping and stabilizing terrestrial sediments with their roots. This reduces the chance of excess sediments deteriora ng water quality and harming the seagrass meadows and coral reefs either directly (burying them) or indirectly (increased turbidity limi ng photosynthesis).

• Seagrass meadows also trap sediments with their leaves and stabilize the seafloor with their roots. Likewise, seagrass meadows help diminish the currents’ strength since the leaves generate resistance.

• Both mangrove forests and seagrass meadows are highly-produc ve environments, that generate a lot of organic ma er. This is used by several reef-dwelling organisms that spend their juvenile life stages in these habitats before moving to the reefs.

• Seagrass meadows are some of the most important carbon sinks and oxygen producers on the planet.

• They obtain the energy to survive through photosynthesis, and they produce great amounts of organic matter.

• A carbon sink is a natural system that absorbs and sequesters atmospheric carbon dioxide (Thompson, 2012). Along with plants and soils, the ocean is one of the largest sinks on the planet, with seagrasses playing a vital role. Seagrass meadows are globally important since they are highly produc ve ecosystems that use large amounts of carbon dioxide (CO2) and produce oxygen (O2) through photosynthesis.

• By consuming part of the carbon dioxide in the atmosphere, seagrass meadows help reduce the planet’s greenhouse effect and can therefore help reduce global warming.

• Seagrasses are primary producers, since they perform photosynthesis.

• Seagrasses provide food for many herbivores.

• The debris left behind after seagrasses decompose is a source of food for many other organisms.

• Seagrass leaves are an important source of food for a wide variety of organisms including manatees and green sea turtles, both endangered species.

• Also, the debris generated by these plants’ decomposi on is food to many other species, such as sea cucumbers, crabs and anemones.

• Seagrass decomposi on also releases nutrients into the water which are then used (reabsorbed) by the grasses themselves and by some planktonic organisms. Some seabirds such as pelicans and swallows fly over seagrass meadows in search for food.