It will balance the development of marine industries, such as wind farms and oil and gas exploration, with the need to conserve and protect marine species and habitats.
The UK is one of the first countries in the world to successfully introduce a single piece of legislation to protect the marine environment.
The MMO's responsibilities include:
- implementing a new marine planning system to balance the varied uses of our seas;
- bringing in a new marine licensing regime that is easier for everyone to use - from individual sea users to corporate developers - with clearer, simpler and quicker licensing decisions;
- streamlining the management and regulation of England's fisheries;
- working with Natural England and the Joint Nature Conservation Committee (JNCC) to create and manage a network of protected areas - marine conservation zones (MCZs) - designed to preserve species and habitats, from the rare and threatened to the more common;
- responding to marine emergencies alongside other agencies.
Chair of the MMO, Chris Parry, said: "The MMO has been up and running since the beginning of April as the champion of sustainable development in our marine and coastal areas. I believe that we are already seeing the considerable benefits of integrated marine management and having a single delivery body, working at both national and local levels, on behalf of all those with an interest and stake in our seas."
MMO Chief Executive, Steven Gant, added: "We know that balancing the needs of industries critical to our country's wellbeing, such as energy exploration and fishing, with the pressing needs of our marine eco-systems will be challenging.
"But we are confident we have the expertise and powers in place to do this successfully. And everyone will benefit from cleaner and healthier seas."
Parliamentary Under Secretary of State for Environment and Fisheries, Richard Benyon said: "The Marine and Coastal Access Act is groundbreaking legislation and the MMO will be a vital part in its successful implementation. Our seas are facing increasing pressures, but through the expertise in this one body we will be able to manage those pressures more effectively."