Mokai Island

Mokai Island

Mokai Island, located in the southeast corner of Rongcheng City, Shandong Province, is the largest island in Rongcheng. It is long and narrow from northeast to southwest. It covers an area of 4.5 square kilometers and has a coastline of 20.22 kilometers.

The geographical location of the island is superior, and it is the natural barrier of Shidao Port. There are unique conditions for the development of fishery and tourism. There is a lighthouse on the island, and a fishing port wharf was built in 1985. The Western sea area has excellent conditions for building a 50000 ton port.

Location context

Mokai island is located in the southeast sea area of Ningjin Town, Rongcheng City, Shandong Province (36 ° 54 ′ 48 ″ n, 122 ° 31 ′ 00 ″ E). It is surrounded by the sea on three sides, adjacent to the Yellow Sea in the southeast, Shidao Bay in the west, and 2.5 km away from Shidao Port. Rongcheng is the largest island in Rongcheng. It is named because it looks like an ancient sword. From northeast to southwest, it is 5.3 km long (i.e. 6 km), 1.5 km wide at the widest point and 0.3 km narrow at the narrowest point, with an average width of 0.84 km. The coastline is 20.22 km long (i.e. 18 km). The highest altitude is 31 meters, with a total area of 8.05 square kilometers, including 4.75 square kilometers of land area (i.e. 4.5 square kilometers) and 3.3 square kilometers of beach area. It is the largest island in Rongcheng.

geographical environment

topographic features

The topography of Mokai island is relatively flat. The west, South and east sides of Mokai island are eroded by waves all the year round. The coastline retreats. There are a large area of sea erosion platforms and sea erosion cliffs more than 10 meters high. Only the northern wave shadow area has two sand mouths and a large lagoon between them. In 1972, a seawall was built, and the highway was connected to the land through the lagoon. Most of the island is covered by residual sediments, and bedrock is exposed only around the island and on the roadside. The exposed strata are the Fuyang formation in the upper part of Archean Proterozoic Jiaodong Group, mainly composed of biotite schist, plagioclase amphibolite, granite gneiss and a small amount of marble. Groundwater is abundant.

Characteristics of sea area

Mokai island is located between Shidao Bay and the Yellow Sea. Shidao Bay is located in the east of Shidao town. It starts from Mokai island in the East and ends at Huangshi banzui in the West. It is a semi oval open bay with a depth of 7.5 km and an average width of 4 km. It covers an area of 31 square kilometers, a water depth of 7 meters, a coastline of 15 km and a soft mud bottom. Bay mouth southeast to open, about 5 km wide.

Physical and chemical properties of seawater

The annual average temperature is 12.3 ℃. In February, the water temperature was the lowest, with a monthly average of 1.3 ℃; in September, the water temperature was the highest, with a monthly average of 22.4 ℃. The temperature rises fastest from April to may, and the temperature drops fastest from October to November. The water temperature in the southern sea area is higher than that in the northern sea area from March to August, and vice versa from September to next February. Extreme value: the highest temperature of 27.1 ℃ appeared on August 15, 1966; the lowest temperature of - 2.8 ℃ appeared on February 2, 1969.

Intertidal zone: the annual average beach temperature is 15 ℃. The highest temperature was 25.8 ℃ in August and the lowest temperature was 1.2 ℃ in December. The annual mean temperature of interstitial water is 12.64 ℃. The highest temperature was 21.02 ℃ in October and the lowest temperature was 1.57 ℃ in December.

Transparency: the transparency of sea water is 50-250 cm, with an average of 120 cm, with the largest in March and September, reaching 600 cm.

Water color: water color is generally lower than 19.

Sea ice: generally, there is only slight ice formation in the Bay during the period from the end of January to the beginning of February.

Salinity: according to the observation statistics from 1960 to 1982, the annual average salinity is 31.63 ‰. The salinity is the highest in June and the lowest from August to September. Except December, the salinity in the southern sea area is lower than that in the northern sea area. Extreme value: the highest value was 32.74 ‰, which appeared on December 14, 1962; the lowest value was 27.3 ‰, which appeared on January 14, 1965. There is a high salinity center with salinity higher than 33 ‰ in the northeast of Chengshantou. The salinity of interstitial water is 31.83 ‰.

PH value: the pH value of shallow seawater and interstitial water is 8.19.

Sea water movement

The tides along the coast of Mokai island are regular or irregular mixed. There is regular semidiurnal tide to the west of Shidao and irregular semidiurnal tide to the east of Shidao. Because there is no tidal point outside Chengshantou, the range of tidal change is small. The average spring tide rise is 141-314cm, and the average neap tide rise is 119-239cm. There is also a certain difference between the two high tides every day. When the day is long, the night tide is greater than the day tide; when the night is long, the opposite is true. The annual average high tide is about 0.4 meters above the yellow sea level, and the low tide is about 0.35 meters below the yellow sea level. The highest tide is 1.07 meters above the yellow sea level, the lowest tide is 1.40 meters below the yellow sea level, and the maximum tidal range is about 1.65 meters.

Near Mokai Island, the first high tide in the first month of the lunar calendar appears at 2:11 on average (from September to January of the next year, the first high tide appears at about 1:30). After that, the first high tide appears 50 minutes later than the day before yesterday, with the maximum tidal range of 2.6 meters, the average tidal range of 2.2 meters in the big flood season and 0.9-1.4 meters in the small flood season. Through years of observation, the masses have discovered the law of sea tide fluctuation, which has been summed up into Proverbs: "on the eighth day of the lunar new year, 23, dry at noon", "two floods on the first and the fifteenth day of the Lunar New Year", "big floods on the second, the third, the seventeenth and the eighth day of the lunar new year, and death news on the tenth, the eleventh, the twenty fifth and the sixth day of the Lunar New Year".

Due to the influence of topography and other factors, the current is more complex. The nearshore flow is mostly annular flow, and the velocity is relatively low, generally 0.15-0.5 M / S; the velocity outside the 10 m isobath is relatively high, generally 0.8-0.9 M / s. The maximum velocity is 1.44 M / s at Chengshantou.

Flow direction: northwest southeast.

There are wind waves and swells in the coastal waters, mainly wind waves, with little interannual variation. The average frequency of wind and wave on Mokai island is 98%. The frequency of swell is 59% in July, only 11% in January, and 26% in the whole year.

The main wave direction of wind wave and swell in each month is shore direction. The main wave direction of Shidao is southwest with a frequency of 8%, and the main wave direction of Shidao is south with a frequency of 11%.

Wave height varies with geographical location and seasonal variation. The average monthly wave height of Shidao sea surface is 0.2-0.7m, 0.7m in July, 0.2m in January and December, with an average annual height of 0.4m. The maximum wave height of Shidao is 6.3 meters, which appeared on July 28, 1960. The inner bay is less affected by the wind, with a maximum wave height of 3 meters; the offshore is obviously affected by the easterly wind, with a maximum wave height of 6.9 meters.

Coastal promontory

The sea area around Mokai Island basically belongs to the type of sand rock mixed sediment dominated by reefs, with large inclination angle of beach surface; the sea area in the south from Mokai island to fenghuangwei basically belongs to the type of reef sediment, with large inclination angle of beach surface.

Dongtou island is located 1km east of houhaiya village, Mokai island. Its geographical coordinates are 36 ° 55 ′ N and 122 ° 32 ′ E. The angle is an irregular triangle with an area of 250 square meters, an altitude of 10.1 meters and a coastline of 0.25 kilometers. There are many reefs in the East and south of the headland, which are not suitable for shellfish growth.

The southeast high angle is located in the south of nanwa village, Mokai island. Its geographical coordinates are 36 ° 53 ′ N and 122 ° 30 ′ E. It is an irregular triangle with an area of 200 square meters, an altitude of 28 meters, and a coastline of 0.3 kilometers. It is an important point on the sea, with a lighthouse at the corner.

reef

Gushaoshi is a huge reef not far from the shore at the west end of Mokai island. Three juxtaposed reefs, the big one in the middle and the small one on both sides, are like sister-in-law holding two little aunts with two hands. Later people called it "sister-in-law rock". "Gusao stone" is also called "Sanfan stone". Its base is huge, like a big ship sleeping on the bottom of the sea. On the base, three stone boron of different sizes are erected at an average distance. Weeds and wild flowers grow on the top of each stone boron. The stone boron is thin on the top and thick on the bottom, like three masts standing on the ship. The height of the left and right stone boron is about 10 meters, and the middle one is more than 30 meters. Because the three stones are flat, they are like sails on the mast, and the one in the middle is like the main mast of a sailboat. When the tide is full, from a distance, "gushaoshi" looks like a sailing boat with three masts, sailing on the blue sea.

fishery resources

Intertidal and subtidal biological resources. According to the report on the comprehensive investigation of intertidal biological resources in Rongcheng County in 1983, the area of the original intertidal zone and subtidal zone reached 156000 mu. After the founding of the people's Republic of China, it has been converted into salt fields, reed fields, grain fields, reservoirs and shrimp ponds, reaching 100000 mu. At the time of the annual investigation, there was only 55000 mu of beach area. A total of 324 species of intertidal and subtidal organisms were collected, including 251 species of animals and 73 species of plants. There are 123 species of molluscs, 22 species of echinoderms, 25 species of Polychaeta, 54 species of crustaceans and 27 other species in the animals, and all the plants are algae. According to the distribution area, there are 254 species of intertidal organisms, with an average annual total biomass of 446.41 g / m2 and an average annual total biomass density of 66.8 g / m2. Among them, there are 24 species of Polychaeta, 91 species of mollusks (37 species of monocrustaceans and 54 species of bicrustaceans), 47 species of crustaceans and 47 species of echinoderms

Chinese PinYin : Mo Ye Dao