Guide for seagrass identification and epiphyte. Andaman sea

1. FIELD GUIDE TO SEAGRASS
IN ANDAMAN SEA
KRABI
SEAGONG PROJECT
2021
By Green Guardians
AUTHOR: Guillaume Lebout

2. INTRODUCTION
Seagrasses are unique amongst flowering plants in that they have adapted to live immersed in seawater. They flower, pollinate
and produce seeds completely underwater. Seagrasses rank with coral reefs and mangroves as some of the world’s most
productive and ecologically significant marine ecosystems. Seagrasses are food for sea turtles, fishes and dugongs, and also
nursery, support complex food webs because of their physical structure and primary productivity. Unfortunately, human
destruction of seagrass communities is occurring on a worldwide scale. Seagrasses are lost at an alarming rate due to
anchoring, pollution, mining, dredging and modifications to water movement. More recently, climate change has been
recognized as a significant global threat as it may alter local and regional environmental conditions needed for seagrasses to
thrive.
There are about 60 species of seagrasses worldwide, with most restricted to sand habitats in coastal waters where they
sometimes form large meadows composed of one or more species. 11 species of seagrasses are known from the Andaman
Sea.
The purpose of this publication is to provide for naturalists, resource managers and scientists a guide to identify the 11
species of seagrasses in Andaman Sea for conservation project.
Each species is described with scientific name, family, ID code in using photographs and detailed description in alphabetical
order.
This guide give some tools to understand and start conservation program (monitoring, mapping, community engagement).
SOURCE / PHOTO
https://www.algaebase.org/ http://www.wildsingapore.com/ https://www.seagrasswatch.org/ https://seagrassspotter.org/
https://www.researchgate.net/ Jon Lapeyra Martin green guardians DMCR
CONTACT: pierre.echaubard@naturemind-ed.com / guillaume.lebout@naturemind-ed.com

3. SEAGRASS DISTRIBUTION IN THE WORLD
Source: Jon Lapeyra Martin

4. LIST OF SEAGRASS SPECIES FOUND IN EACH PROVINCE
IN THE GULF OF THAILAND AND ANDAMAN SEA
Source: Department of Marine and Coastal Resources

5. Cymodocea rotundata
Family: Cymodoceaceae
ID code: CR
- Leaf tip rounded or squarish with smooth edge, sometimes with indentation in the middle.
- Narrow leaf blade (2-4mm wide).
- Leaves 7-15 cm long.
- 9-15 longitudinal veins.
- Well developed leaf sheath.
- No cross hatched veins.
- Rhizomes thick, smooth.
- separate male and female plants. The female flower appears in pairs at the base of the leaves. They have a prong-like stigma.
- The male flowers form within the leaf sheath.
- Seeds (10mm) are dark color with a hard-coated, beaked nut with a spikey central ridge along the length.
- The seeds are attached to the rhizome.

6. Cymodocea serrulata
Family: Cymodoceaceae
ID code: CS
- Serrated ribbon seagrass
- Leaf tip rounded with serrated edge
- wide leaf blade (4-9mm wide)
- leaves 6-16 cm long
- 13-17 longitudinal veins
- No cross hatched veins
- Robust / strong rhizome (thick, smooth)
- Triangular shaped sheath
- This seagrass has separate male and female plants. The female flower appears in pairs at the base of the leaves. They have a
prong-like stigma. The male flowers form within the leaf sheath.
- Seeds (10mm) are dark color with a hard-coated, beaked nut with three blunt ridges along the length. The seeds are attached
to the rhizome.

7. Enhalus acoroides
Family: Hydrocharitaceae
ID code: EA
- Very long ribbon-like leaves with inrolled leaf margins.
- Thick rhizomes with long black bristles and cord-like roots.
- Leaves 30-150 cm long.
- Leaf edges are inrolled.
- Leaf tip rounded smooth.
-It has separate male and female plants.
- Male flowers are tiny (1cm) and when these float on the water surface, they look like small pieces of white polystyrene or
styrofoam.
- The female flower is large and held on a long stalk. It has three large ribbed white petals (2-3cm).
- The fruit is round to tear-drop shaped and large (4-6cm in diameter) with dark, ribbed hairy skin.
- Roots develop rapidly and the seeds germinate quickly.

8. Halodule pinifolia
Family: Cymodoceaceae
ID code: HP
- Fine, delicate leaves up to 20 cm long.
- Width of leaves 1 cm.
- 1 central vein.
- Rounded leaf tip.
- The leaves emerge from thin rhizomes (underground stems) which have fine roots.
- Black central vein splits into two at the rounded leaf tip.
- Usually pale rhizome, with clean black leaf scars.
- Found on inter tidal sand banks.
- Needle seagrass has separate male and female plants.
- The flowers are tiny, usually forming at the base of the leaf sheath, buried in the sediment and emerging only for a short
period.
- It produces seeds with a hard seed coat.

9. Halodule uninervis
Family: Cymodoceaceae
ID code: HU
- Fine, delicate leaves up to 15 cm long.
- Width of leaves 2-5 mm.
- 1 central vein.
- Trident leaf tip.
- The leaves emerge from thin rhizomes (underground stems) which have fine roots.
- Black central vein splits into two at the rounded leaf tip.
- Usually pale rhizome, with clean black leaf scars.
- Found on inter tidal sand banks.
- Needle seagrass has separate male and female plants.
- The flowers are tiny, usually forming at the base of the leaf sheath, buried in the sediment and emerging only for a short
period.
- It produces seeds with a hard seed coat.

10. Halophila beccarii
Family: Hydrocharitaceae
ID code: HB
- Smallest seagrass (0.5cm long).
- The long oval-shaped leaves emerge in a rosette of 5-10 tiny leaves on long thin stems.
- Some brown stain on the leaf.
- 1 vertical and central vein and a thinner on each side.
- Each plant may bear both male and female flowers, but usually, only male or female flowers are visible on a plant.
- The flowers and fruits are tiny.
- Each fruit contains up to 6 seeds.

11. Halophila decipiens
Family: Hydrocharitaceae
ID code: HD
- Thin rhizomes that run along near the surface of sand or mud, with a root at each node to anchor the plant in place.
- The almost stemless leaves grow in pairs from the nodes with a pair of scales at their base.
- The leaves are paddle-shaped and have a finely serrated margin and are up to 25 mm long and 6 mm wide.
- 6-8 cross veins
- Leaf hairs on both sides
- Leaves usually longer than wider
- Found at subtidal depths (>10m)
- Male and female flowers are found on the same spathe.
- A female flower can produce about 30 seeds.
- Flowering seems to be stimulated by a rise in water temperature above a certain threshold rather than day length. The plant
is an annual.

12. Halophila minor
Family: Hydrocharitaceae
ID code: HM
- Less than 8 pairs of cross veins
- Small oval leaves occurring in pairs
- leaves 1-4 cm long
- Wedge‐shaped leaf sheath
- Found on shallow/intertidal sand flats
- It has separate male and female plants.
- The flowers form at the base of the shoot but may extend to above the height of the leaves.
- The male flower remains low.
- The round fruits are tiny.

13. Halophila ovalis
Family: Hydrocharitaceae
ID code: HO
- 8 or more cross veins.
- No hair on leaf surface.
- Leaf margins smooth.
- Leaf 5-40 mm long.
- Rhizomes has thin, smooth, white (underground stems) about 2mm in diameter.
- It has separate male and female plants.
- The flowers form at the base of the shoot but may extend to above the height of the leaves.
- The male flower remains low.
- The round fruits are tiny.

14. Siringodium isoetifolium
Family: Potamogetonaceae
ID code: SI
- Noodle seagrass.
- Cylindricale leaves.
- Leaves have a smooth pointed tip.
- Leaves 7-30 cm long.
- Found on shallow subtidal reef flats and sand banks.
- The rhizomes (underground stems) are slender (1.5mm in diameter).
- the leaves contain air cavities, they float easily when detached.
- it has separate male and female plants.
- The flowers form a complex inflorescence (called a cyme).
- Each flower forms in a branching array on a stem.
- The fruit forms a small nut that is hard and beaked.

15. Thalassia hemprichii
Family: Hydrocharitaceae
ID code: TH
- Sickle, curved seagrass. Crescent moon shape.
- Leaf tip rounded.
- Cross hatched veins.
- Leaves 10-40cm long.
- Short black tannin cells, 1-2mm long in leaf blade.
- Rhizomes thick, with leaf scars.
- This seagrass has separate male and female plants. The flowers form at the base of the shoot and is hidden by the sheath
until they emerge.
- The male flower is held on a long stalk, maturing into 6 or more parts.
- The female flower appears similar but has a finer texture.
- Fruits are oval and prickly, containing up to 9 tiny seeds.

16. APPENDIX 1
Epiphyte
As with any surface in the marine environment, seagrass leaves provide a place for planktonic organisms to settle. When they settle
on seagrass leaves, they are called epiphytes (sessile organisms that grow on plants). Epiphytes of seagrasses include algae (micro
and macro), bacteria, fungi, sponges, bryozoans, tunicates, protozoa, hydroids, crustaceans and mollusks.
Algae epiphytes are common and can densely cover the leaves of plants like seagrass. This is called "biofouling" - probably because
it turns the clean, green grasses a bit cloudy and brown. These marine epiphytes are grazed by organisms such as snails and if the
balance of host/epiphyte/grazer is not in check, the host plants can be smothered by epiphytes and prevented from
photosynthesizing.
So during seagrass monitoring, it’s important to survey the epiphyte cover on the seagrass.

17. CONTACT and INFORMATIONS
E-MAIL: greenguardians.asso@gmail.com
LINE: green guardians
FACEBOOK: @greenguardians.asso
INSTAGRAM: greenguardians.asso
THAILAND
80 5 Moo 4 Ao Nang
Muang Krabi 81180
FRANCE
Rue Saint Caprais
91770 Saint-Vrain