Summary of our Findings

Importance of Seagrass:

• acts as a nursery for juvenile fish species, providing a safe environment in which to reach adulthood.
• is an important food source for many vegetarian marine species, such as dugongs, which are endangered.
• puts oxygen into water through photosynthesis, creating a cleaner and healthier ocean.

Dangers posed by the Japan Crisis:

• radiation being put into the sea will damage seagrass levels considerably.
•  (previous posts for more details)
• Seagrass can only grow in the photic zone (the area of the ocean into which light penetrates). The photic zone varies, and is determined by the clarity and depth of the water. The movement of the earth's crust, combined with the high input of debris from the crisis will significantly decrease the photic zone around northern Japan, and thus the habitat in which seagrass can grow.
• Seagrass in Japan are mainly found in depths of around 20m or shallower in muddy sands, gravel sands, coral sands or reef platforms (Seagrasses from Japan: species composition, distribution) and the high energy of the waves would have caused the uprooting of many seagrasses 
• as the energy of a wave is proportional to the square of its amplitude, a 32m high tsunami would have a wave strength 1000 times that of a normal 1m wave with a strength of 1 unit 
• the highest height of the tsunami was 37.9 m 
• Since the 2004 9.1 earthquake in Indonesia had caused a damage of 20% to seagrass beds and 30% to coral reefs (according to the State Ministry of National Development Planning) and 3-10% damage to seagrass beds in Thailand (according to the Thai government) , it can be expected that a larger damage will be done to the seagrass beds of Japan as the energy released was nearly double that of the 2004 earthquake
• According to the New York Times the earthquake led to shift of Honshu (the main island of Japan) by 13ft to the East, with the largest shifts happening closest to the epicentre--> this would have caused the destruction or  loss of many of the seagrass habitats (especially those located new Sendai) on the east coast of Japan as seagrasses are mostly found  50km2 or less from the coastline (with some exceptions according to the study: Seagrasses from Japan: species composition, distribution) http://www.nytimes.com/2011/03/14/world/asia/14seismic.html?_r=1 (see diagram below)  

red dots = major segrass locations (http://data.unep-wcmc.org/datasets/9#Download)

• Without a safe area in which to mature, many fish species living in the seagrass ecosystems of Japan will experience a drop in population.
• A decline in food sources will cause population levels of marine vegetarian species to decline.
• Without additional sources for oxygen input into the water, it will take longer for the sea around Japan to be habitable for marine life again.
• The change in photic zone and seafloor levels could possibly mean that seagrass will grow back in much more limited quantities.

Economy

• Fishing is a large part of Japans economy (fresh water fishing = 30%)
• The loss of fish habitat, and thus population and the additional loss of species is likely to have a severe, long lasting impact on the economy
• As the loss of fish species and populations is not likely to recover in  near future, consequently it it likely that the impact on the Japanese economy will be long lasting
• From a strictly economic point of view, the decline of the fishing industry is likely to have a negative impact on the economy as a whole, as well as the global supply of fish.
• The overall effect of the decline in fish populations will create a long lasting, severe shock for the Japanese economy, as well as the rates of unemployment.