Has decline in whale stocks negatively impacted on marine production?Would we expect a measurable decline in local productivity if whales were missing from the picture?

Has decline in whale stocks negatively impacted on marine production?

Whales have been hunted to extirpation and near extinction in many places around the world. Incorporating both top predators and plankton feeding mega fauna, it is fair to expect that their removal might have a knock-on effect on local food webs. However, is this effect really significant? Would we expect a measurable decline in local productivity if whales were missing from the picture?