Bladderwort is a tough name.  Yes, it has bladders, and someone might have thought it had medicinal or food value back in the day.  But the formal name is so much better: Utricularia.  I will use that.

IMG_4057Utricularia has been in the pond for years, but I didn’t notice it until 2016, when it was superabundant.  There are multiple species in the genus, and I’m not sure which one(s) constituted the near carpet on the pond back then.  At least some of them were Utricularia inflata, but most were probably something else.

When they are blooming, they are impressive.  The flowers are supposed to be yellow (one species is purple, and I’ve seen that on another pond), and some of them are bright yellow, but most are mostly white with only a hint of yellow.  That’s another reason why I am unsure what species are present.

July 2016
July 2016

Whatever they are, these plants, as a group, are highly variable in abundance, year to year, as least in the portion of the pond that I visit.  I don’t know why, but I wanted to document this variability, at least visually.

Look at how they have changed in abundance in this part of the pond.  The peak seems to have been 2016, though pictures from earlier years show that they were present.  Since 2016 (left), the numbers have declined (2017 in the center, 2020 on the right).

Why have they declined?  I don’t know.  Will they become abundant again?  Probably, because there was a bit of a resurgence in 2018.  Will they disappear?  I hope not.

Update 2021

Utricularia is essentially gone from the pond.  I saw none in 2021.  I might have missed some if they were hidden among other plants, but there is no question that their population has, in a word, crashed.

I didn’t expect such a radical fall in numbers, but then, I hadn’t foreseen such a radical rise in 2016.  We should add Utricularia to the list of species that fluctuate dramatically in abundance.  There are some hypotheses about why other species rise and fall so spectacularly: diseases, resources, predators, something called the Allee effect (a requirement for a minimum number of individuals before the population can take off), and more.  I don’t know enough about Utricularia to say whether any of these hypotheses – or something else – is relevant.   And bladderwort abundance is obviously hard to study because the numbers keep changing, and sometimes they are missing.  But it still might be worth a try.