The oceans cover 71% of the earth's surface, with the deepest part being about 11,000 meters below sea level, and the average depth of the oceans is about 3,800 meters. As is often said, it is more appropriate to call it a sea sphere than the Earth. The ocean is also the place where life originated, and it was the site of biological evolution for a long time before organisms began to live on land. In terms of the number of species, the ocean has about 220,000 species, which is not as many as those on land, but in terms of evolutionary diversity, such as the number of phyla, the ocean is home to more than 30 phyla, while land and freshwater have less than 20, making the ocean by far the most diverse. This indicates that terrestrial organisms originated in the sea, and only a portion of marine organisms made it to land.
The environmental factors affecting organisms in the sea and on land are very different. In addition, the word "ocean" in a nutshell covers a wide range of environments from estuarine to coastal areas to the open ocean. Even in terms of depth, there is a wide range of environmental differences, from the shallow sea where sunlight reaches the surface to the deep sea where no light at all reaches the surface. Life forms adapted to each of these environments live in them.
In this marine ecology training, students learn about the relationship between such environmental factors and organisms in the ocean. The best part of the practical training is the opportunity to actually go out to sea and come into contact with the organisms and the diversity of life in the environment. The training period is short, and there are not many practical exercises available, but I would like you to spend the training period looking and thinking carefully for yourself, without being passive.
The sea as a habitat for living things
1) Rocky intertidal shores: These rocky intertidal shores provide a solid and stable substrate for attached organisms, but are also subject to strong waves in some cases. It is also a unique growing site that is exposed to the air and submerged in the sea due to the tides that occur twice a day. Many seaweeds thrive here, as well as many adherent and detritivorous animals.
2) Tidal flat: A sedimentary bottom (a seabed composed of sand and mud) formed at the back of bays and estuaries, which is located in the intertidal zone and is dried up at low tide. Generally, the water movement is quiet and stable. In estuarine tidal flats, salinity fluctuates greatly during the course of a day due to the inflow of river water and tides. Mangroves are also categorized in this growing environment.
3) Sandy beach: In contrast to 2), sandy beaches face the open ocean and have an unstable substrate of sand that is constantly changing due to waves and currents. Many animals grow specifically on sandy beaches. There are also many small organisms that grow in the spaces between the sand grains.
4) Seagrass beds: Refers to landscape communities consisting mainly of large plants (seagrasses and seagrasses) that inhabit the intertidal to subtidal zones. Seagrass beds (eelgrass beds) form on sedimentary bottoms (sandy and muddy bottoms) and are dominated by seagrasses, whereas seaweed beds form on reef bottoms and are dominated by soft brown algae such as Honda straw; kelp forests consist mainly of hard brown algae such as arame, kajime, wakame and kelp.
5) Pelagic ecosystems (oceanic and coastal): In offshore areas, there is no substrate to support organisms, so organisms in these habitats must be able to swim or float.
Each habitat is home to a wide variety of organisms that are well adapted to their environment. Although we will only be able to observe a small portion of these organisms in this exercise, we hope that you will observe the organisms from the perspective of their habitat and the adaptation of the organisms living there to the environment.
Surveys conducted during Training of Marine Ecology