The 41 new protected areas range from the coast of Northumberland, designated to protect eider ducks, to the seas south of the Isles of Scilly, which supports seabirds, fish and basking sharks.
Other species that could benefit from the new wave of protection include the rare stalked jellyfish, short-snouted seahorse and blue mussel beds.
The newly designated protected areas cover 4,600 square miles of England's seas - an area almost eight times the size of London, the Environment Department (Defra) said.
With the new marine conservation zones, the UK's "blue belt" of protected sites spans 85,000 square miles around the seas of England, Scotland, Wales and Northern Ireland.
Conservationists described the introduction of the 41 areas as "fantastic" and said good management was now needed to stop damaging activities in the sites in order to protect wildlife.
Environment Secretary Michael Gove said: "The UK is already leading the rest of the world by protecting over 30% of our ocean - but we know there is more to do.
"Establishing this latest round of marine conservation zones in this 'year of green action' is another big step in the right direction, extending our blue belt to safeguard precious and diverse sea life for future generations to come."
The designation of the new sites follows a consultation, including with local fishermen, marine conservation experts and 48,000 responses from the public.
All of the proposed sites have been designated, and protections expanded at 12 existing sites.
Dr Jean-Luc Solandt, from the Marine Conservation Society, said: "The UK has a growing network of more than 300 marine protected areas, but the government must now invest in proper management of these sites and keep them free of all activities that damage the seabed so that our spectacular marine wildlife can recover from decades of destruction and degradation."
Alec Taylor, head of marine policy at WWF, warned: "The UK is nearing 30% coverage of its waters protected, but these areas are poorly monitored and we have little evidence that wildlife is benefiting.
"We need proper management of activities within the boundaries of all marine protected areas and strict enforcement of safeguarding laws. Only then can we secure a future where people and nature thrive.
Charles Clover, executive director of the Blue Marine Foundation, warned there was a need to protect the conservation zones from fishing, otherwise they were just "paper parks".
"Places highly and fully protected from fishing, especially fisheries using towed gears like bottom trawls and scallop dredges, as well as from aggregate dredging, maintenance dredging, dumping and land-based pollution, are shown to have thriving seabed communities."
But he said trawls and dredges were only banned in 5% of UK marine protected areas, and there was more trawling and fewer fish inside them than outside.
"If we dramatically increase levels of protection for these places, we would have a world class network that would deliver the clean, healthy, safe, productive and biologically diverse oceans and seas the government aspires to," he said.