What is seagrass?
Seagrass, a marine angiosperm, which is not the same as algae, composes of distinct leaves, horizontal and/or vertical rhizomes, and roots. Worldwide, about 60 seagrass species are distributed in coastal and estuarine ecosystems. Seagrass provides numerous crucial ecological and economic services to the marine ecosystems and forms extensive meadows supporting high biodiversity.
Seagrass Family and Genera
| Family | Genera |
|---|---|
| Cymodoceaceae | Amphibolis, Cymodocea, Halodule, Syringodium, Thalassodendron |
| Hydrocharitaceae | Enhalus, Halophila, Thalassia |
| Posidoniaceae | Posidonia |
| Ruppiaceae | Ruppia |
| Zosteraceae | Phyllospadix, Zostera |
UNEP-WCMC's Ocean Data Viewer (http://data.unep-wcmc.org/datasets)
The seagrasses of the republic of Korea
Among the 60 seagrass species, 9 seagrass species are distributed on the coasts of the Korean peninsula, indicating high species diversity. Seagrasses occur on soft sediments and rocky substrata from intertidal to about 15 m off the Korean peninsula.
Zostera marina is the most abundant seagrass species in the northern temperate zones and is widely distributed across all Korean coastal areas. In Korea, the optimal growth temperatures for
Z. marina and
P. japonicus were found to be 15 ? 20 and 14℃ during spring, respectively, whereas the growth of
H. nipponica, which is recently observed on the southern coast of Korea, was highest at approximately 25℃ during summer.
Seagrass species in Korea
| Genus | Species | Characterization |
|---|---|---|
| Halophila | Halophila nipponica | Tropical/subtropical seagrass species, the first observation in 2007 |
| Phyllospadix | Phyllosapdix iwatensis | Occurrence on rocky seashore |
| Phyllospadix japonicus | Occurrence on rocky seashore | |
| Ruppia | Ruppia maritima | Wigeongrass, a salt-tolerant seagrass species |
| Zostera | Zostera asiatica | A limited distribution on the Pacific Ocean, 8?12 m in depth |
| Zostera caespitosa | Very short rhizome occurrence relatively more than Z. marina | |
| Zostera caulescens | Giant seagrass, more than 5 m of shoot height | |
| Zostera japonica | Dwarf glass, occurrence in intertidal zone | |
| Zostera marina | Eelgrass, dominant seagrass species in Korea |
Seagrass value and function
Seagrass provides important habitats and nurseries for diverse groups of marine organisms and is a crucial food source for herbivores such as dugongs, green sea turtles, and manatees. Seagrass also plays an important role in fisheries production, oxygen production and sediment stabilization. Because seagrass can store carbon as much as forests (83,000 metric tons of carbon km
-2 ), seagrass is a vital bio-resource for the solution of the climate change. Seagrass meadows can assimilate and sequester large amounts of inorganic nitrogen (N) and phosphorous (P) through both leaf and root tissues, reducing the occurrence of eutrophication and red tide algal bloom. Thus, seagrass is highly valuable primary producer in coastal and estuarine ecosystems ecologically and economically.
Seagrass decline
Although seagrass is a crucial component of coastal and estuarine ecosystems, more than 50% of seagrass coverage has been lost during recent decades worldwide. In Korea, large areas of seagrass (70-80%) have been lost due to numerous the anthropogenic disturbances since the beginning of industrial development during the 1970s. The main causes of seagrass declines are related to human activities such as dredging, reclamation, and fishery as well as natural events including global climate change, grazing and algal bloom. Reclamation is one of the main causes of decline in Korea. For example, Large
Zostera marina bed (13.6 km
2 ) existed in the Nakdong River estuary on the southern coast of Korea until the mid-1980s, but these meadows nearly disappeared due to reclamation of adjacent mud flats for the construction of a port and industrial complex during the late 1980s.
Seagrass management and restoration
In 2007, the law, "CONSERVATION AND MANAGEMENT OF MARINE ECOSYSTEMS ACT" was established to protect and manage marine organisms including (
P. iwatensis, P. japonicus, Z. asiatica, Z. caespitosa, Z. caulescens , and Z. marina ). The IUCN (International Union for the Conservation of Nature) Red List of Threatened Species contains 15 seagrass species. Among these, 7 threatened seagrass species are distributed on the coasts of Korea. Thus, seagrass habitats on the coasts of Korea require conservation, management and restoration on the coasts of Korea due to high risk of extinction. Because of the essential roles of seagrass habitat in coastal and estuarine ecosystems, numerous seagrass habitat restoration projects have been attempted in many countries since the 1940s. Natural improvement of seagrass beds may be a very slow process and consequently, requires long periods of time, whereas seagrass transplantation might be a rapid way to restore seagrass meadows. In Korea, efforts for seagrass habitat restoration have also been carried out recently on the south coast of Korea (see below). Re-established seagrass ecosystems are more than just meadows. They contain an abundance of marine organisms and provide numerous ecological and economical services.
