It seems we don't have any pond plant experts rushing to offer advice. Nor can I help much. I haven't a clue what species of plants are in our pond but they are all showing signs of spring growth. It is late April, so a complete absence of new growth does seem odd.
Mind you, the weather has been a bit perplexing. Incredibly wet for a spell (I posted a pic of a nearby plot under water), then bitterly cold, and now hot days, cold nights and drought conditions in my part of the world. I've got frost's killing the blossom on the plum tree, and strawberries in flower, well chitted first early potatoes that went in early March yet to show. The plants seem confused and who can blame them. Whatever happened to April showers?