Imperial Germany's submarine mining threat

What if Imperial Germany had 150 minelaying submarines in 1914?

A larger German submarine arm would intensify an already serious blockade threat, with minelayers especially effective because their mines continued to cause losses after the boat had moved on.

The scenario specifically adds a force of minelaying submarines to Imperial Germany in 1914. The answer regards these boats as particularly dangerous because their mines could sink ships after the submarine had moved elsewhere to use torpedoes. It also argues that Germany's First World War submarine campaign came closer to starving Britain than the Second World War campaign. That comparison rests partly on Britain having learned from the earlier threat and prepared for tactics used again later. No numerical estimate is given for the extra losses or the chance of forcing Britain out of the war.