Figure 1: A typical seagrass patch. (Photo taken by Cheok Zi Yu) |
Figure 2: From left, the domesticated cow and its marine counterpart, the sea cow, or Dugong both grazing on their favourite foods. Images under Creative Commons license |
Figure 3: Thalassia hemprichii when submerged. Image courtesy of Ria Tan (Wildsingapore) |
Video courtesy of Aquaworks Underwater Films |
Figure 4: From left, Hippocampus comes, Tiger Tail Seahorse (image courtesy of Ria Tan (Wildsingapore)) and Pentaceraster mammillatus, Pentaceraster Sea Star (taken by Cheok Zi Yu) found on seagrass patches in Singapore |
Figure 5: A dugong feeding trail |
|
Seagrass meadows are home to commercially important species such as Giant Tiger Prawns (Peneaus monodon and P. semisulcatus), Whitings (Merlangius merlangus), Snappers (Lutjanus synagris, L. apodus etc.) and more. Decline of seagrass meadows has been predicted to cause significant economic losses in the fishery industy[12] . Seagrass meadow's high productivity and canopy cover are important in counteracting two key aspects of global warming: unprecedented levels of carbon dioxide in the air and sea level rise. Seagrasses consume carbon dioxide in the water as they grow, storing carbon and acting as a carbon sink[14] . This is particularly true of the persistent climax seagrass species such as T. hemprichii, which are long lived[15] . The leaves of seagrasses slow down wave velocity during storms and their roots stablise sediments, protecting coasts from erosion, which is important as the sea level continues to rise[16] . T. hemprichii meadows are also thought to experience enhanced deposition relative to meadows where other species dominate[7] , an added benefit of having this species around! |
Figure 7: Seagrass meadows in Singapore in the 1950s and 2000s. Note the island's growth in size and a number of newly emerged seagrass patches on the East coast. Edited with permission from Yaakub et al., 2014 |
Figure 8: This is a re-emerged (and newly discovered) patch located on the southeastern coast of Singapore. It had yet to be recorded when Yaakub et al. (2014) was published |
Estimated distance travelled |
T. hemprichii[29] |
T. testudinum[30] |
Seed |
less than 5km |
0.06-3km |
Fruit |
23km |
less than 1-15km |
Figure 9: From top, a) distribution of Thalassia hemprichii; b) distribution ofThalassia testudinum. From Discover Life[33][34] . Note that the lone demarcation of T. testudiunum in the east coast of Africa is due to a preserved specimen and is not indicative of the distribution of the species. |
Figure 10: Key morphological characters of T. hemprichii. The scars on the rhizome and thick sheath are diagnostic traits that differentiate this species from other seagrass species in the region. Photographs taken by Cheok Zi Yu |
Figure 11: Reproductive structures of T. hemprichii. 1) Fruit; 2) Flower; 3) Seed. Drawing is under creative commons license Wikipedia page and image of the seed is courtesy of Ria Tan (Wildsingapore) |
Figure 12: Thalassia testudinum, which looks very similar to Thalassia hemprichii |
Flower structure (sex) |
T. hemprichii |
T. testudinum |
Number of styles (female) |
6 |
7-8 |
Stigmatic branches (female) |
Shorter then its sister species |
Longer than its sister species |
Number of stamens (male) |
3-12 |
9 |
Kingdom |
Plantae |
||||||||
Phylum |
Tracheophyta |
||||||||
Class |
Liliopsida |
||||||||
Sub class |
Alismatidae |
||||||||
Order |
Hydrocharitales |
||||||||
Family |
Hydrocharitaceae |
||||||||
Genus |
Thalassia |
||||||||
Species |
Thalassia hemprichii |
Original taxonomical document by Ascherson[38]Read online |
A snapshot (incomplete) of the original description of the species (in German)[39]Read online |
ICZN |
IAPT[41] |
|
Neotype |
To replace a missing holotype[42] |
Serves as a holotype “as long as all of the material on which the name of the taxon was based is missing” |
Lectotype |
Becomes the holotype, chosen from a set of syntypes[43] |
A specimen/illustration of the original material if no holotype was indicated at the point of publication, or if holotype is missing – it takes precedence over the neotype |
Figure 13: Strict consensus phylogenetic tree depicting evolutionary relationships between aquatic angiosperms, species within light blue boxes are "seagrasses" with T. hemprichii marked with a black arrow, and non-seagrass hydrophilic species are boxed in dark blue. Orange and red arrows mark two hypothetical origins of "seagrasses". Used with permission from Les et al. (1997) |
Angiosperm |
a flowering plant |
Asexual Reproduction |
Incliudes seed production without fertilisation and 'selfing' (clonal growth) |
Carbon sink |
a natural environment that stores carbon for a long period of time |
Cryptoviviparious |
the embryo within the seed grows to become a seedling while the seed is still attached to the parent plant |
Diagnosis |
Unique descriptions on a species enabling you differentiate from other species |
Dioecious |
male and female reproductive organs are found on separate individuals |
Epiphytes |
sessile organisms that grow on plant. Compare to the terrestrial definition Wikipedia |
Habit |
the general shape or appearance of the plant |
Holotype |
a single type specimen upon which the description and name of a species is based on |
Hydrophilous |
a pollination system where pollen grains are transported on or below the surface of water (Les 1988), thought to be a requirement for invasion of marine habitats |
Infauna |
a group of animals which live within the sediments of aquatic habitats |
Lectotype |
a subsequent type chosen to serve as the holotype of a species |
Monocots |
a group of flowering plants with seeds that contain one embryonic leaf |
Monophyletic |
a group of organisms (clade) that consists of an ancestor and all of its descendants |
Nomenclature |
The naming of a species |
(Primary) productivity |
rate at which energy gets converted into organic carbon via photosynthesis |
Taxonomy |
the traditional definition, which encompasses species descriptions (alpha) and assigning them into higher classifications (beta) |