C.2 communities and ecosystem from Bob Smullen
Bio C2 Communities & Ecosystems in 5 minutes from roxprice:
Ecosystem Ecology: Links in the Chain – Crash Course Ecology #7 with Hank Green:
or here is Energy Flow in Ecosystems from Mr Andersen:
SUCCESSION
Mr Andersen explains Succession in 6 minutes:
and Hank Green takes 10 minutes in Ecological Succession: Change is Good – Crash Course Ecology #6:
Videos on Surtsey and primary succession: The Formation of Surtsey (Encyclopedia Britannica); Surtsey Still Surprises (58s); Stages of Primary Succession (3m 30s).