Mangroves are small trees that grow in the muddy areas of tropical or subtropical coastal regions. These plants have developed unique morphological and physiological features to ad apt to their habitat environment. Mangroves belong to the family Rhizophoraceae, feature mostly red trunks, are rich in tannic acids, and can be used to make red dye. Taiwan possesses mangrove forests totaling approximately 300 Ha. The forests can be found from the Keelung Bay to the Dapeng Bay and contain four families, seven genera, and seven species of mangroves: Rhizophoraceae Bruguiera gymnorrhiza (L.) Lamk., Ceriops tagal C.B. Rob., Kandelia obovata Sheue, Liu & Young, Rhizophora stylosa Griff., Verbenaceae Avicennia marina Vierh, Combretaceae Lumnitzera racemosa Willd., and Euphobiaceae Excoecaria agallocha L. Mangroves grow in tropical or subtropical regions and are important coastal ecosystems serving important ecological functions. Together with seagrass beds and coral reefs, they are listed as the three typical marine coastal ecosystems. In addition, mangroves are a critical part of wetland ecosystems, providing the environment needed by marine organisms to gr ow and develop. Moreover, their leaves are crucial sources of energy. Furthermore, mangroves provide a place for birds to rest and stay during migrations. To humans, mangroves offe r many ecosystem-related functions, such as stabilizing coasts, preventing erosion, purifying water, providing shelter from wind, and reducing the impact of storms and waves. Mangr oves are the coasts ’ natural protectors, offer important ecological functions, and possess economic value.

Corals are marine invertebrates classified under the phylum Cnidaria. Their bodies consist of mesoglea sandwiched between two layers of epithelium (i.e., an ectoderm and endoderm). The ectoderm is where cnidocytes are found. Polyps are the living parts of corals and are the contributors of colonial corals in most corals (e.g., Acropora austere); said colonia l corals are formed by polyps undergoing asexual reproduction. However, solitary corals (e.g., mushroom corals) also exist. When polyps grow, they accumulate calcium carbonate, for ming calcareous bones that in turn become coral reefs. Corals are found in all parts of Taiwan, including the Northeast Corner, Kenting, Green Island, Orchid Island, Hsiao Liouciou Island, Penghu Islands, Pratas Islands, and Taiping Is land. Taiwanese corals can be divided into two types: non-reefal coral communities and tropical coral reefs. The distribution of corals is determined by climate and ocean currents. Because non-reefal coral communities are exposed to water temperatures lower than those required for reef-building corals to grow, they grow on hard matrix and do not form coral r eefs. Non-reefal coral communities are primarily found on rocky shores in Northern Taiwan, the inner seas of Penghu Islands, and the northern seas of Penghu Islands. In contrast, t ropical coral reefs are mainly found in Southern Taiwan, Green Island, Orchid Island, Hsiao Liouciou Island, Penghu Islands, Pratas Islands, and Taiping Island, where temperatures are suitable for corals to grow. Coral reef ecosystems are the most “productive ” and biologically rich ecosystems in the oceans. Their complex structure and environment provide not only marine life with habitat and food sources, but also coastal residents wit h means of livelihood and for developing marine tourism. Coral reef ecosystems support people ’s livelihood, prevent coastal erosion, reduce the magnitude of severe weather-led waves, and ensure coastal stability.

Algae reefs are biological and algae-formed reefs. They are formed when coralline algae accumulate calcium carbonate and attract other organisms, after which they slowly evolve int o a unique terrain structure. Coralline algae grow remarkably slowly, increasing approximately 1 cm in thickness every ten years. Coralline algae resemble coral reefs, are highly “productive ” with high biodiversity, and possess a 3D space and porous environment that enable organisms to grow, hide, and forage. Large-scale algae reefs are distributed across the coasts of Taoyuan City and are mainly found in the intertidal zone between south of the Xiahai River (in Dayuan District) and the Yongan Fishing Harbor (in Xinwu District). In this intertidal zone, an algae area measuring approximately 7 km long and containing baiyu algae reefs, datan algae reefs, and guanxi n algae reefs can be found. Said area is a relatively healthy algae reef area rich in crustose coralline algae (aka. hermatypic coral red algae). Other areas containing crustose co ralline algae (albeit considerably less in number) include Shimen and Sanzhi Districts in New Taipei City, Kenting in Pingtung County, and Sanxiantai and Shanyuan in Taitung County . Animals found around algae reefs include various small fish, crustaceans, shellfish, and polychaeta. Algae reefs also provide shelter for birds and are a place for them to forage a nd breed. For migratory birds such as anatidae, Chinese egrets, and terns, algae reefs are their main food supply stations and resting places. Most importantly, because living crus tose coralline algae attach themselves to aging calcified algae reefs, they ultimately protect the algae reefs from wave-led erosion, serving the role of protectors in marine ecosy stems.