The Memorial Day Reality Check
What Cyanobacteria Do in Winter
The Myth of the Winter Reset
The Perfect Storm: Nutrients and Turnover
How Cyanobacteria Get a Jump Start
The Prognosis: Earlier, Longer, More Intense Blooms
Cyanobacterial Succession
Panic Firefighting vs. Strategic Prevention
The Proof: Active Winter Management Works
Full Script with Chapter Markers:
[00:00] The Memorial Day Reality Check
Memorial Day is supposed to be the official start of summer fun on the lake. But what if your lake already looks like a liquid lawn or is already under a toxic HAB warning before summer has even begun?
How does it come to this?
It’s not just bad luck or a spell of slightly warmer weather. The reality is – this has been months, and in most cases, years in the making. And the sad news is – it’s going to continue to get worse every year – because your lake management plan is likely going to keep on helping it do so.
By the time the water turns green, or a warning sign goes up, the conditions that help cyanobacteria take over have been well established for a long time.
A Memorial Day toxic algae bloom is just the final manifestation of a process that is well-studied, well-understood and well-documented in scientific studies.
So let’s take a look at what cyanobacteria do in winter to get ahead of the game, how cyanobacteria actually get a jump start on beneficial algae in late winter and early spring – especially if perfect storm conditions exist, what the science says about early toxic HABs and later summer blooms, and how cyanobacteria can lock themselves into place in a lake all year round, and we’ll finish up by looking at what you need to do to get control, get ahead of the game yourself and make sure that you don’t end up in the same position – or worse – come Memorial Day next year.
[01:40] What Cyanobacteria Do in Winter
So first, let’s look at what cyanobacteria do over winter. You see, cyanobacteria are not just simple algae, – scientific research has shown that they have special winter survival and early bloom initiation capabilities that beneficial algae don’t have.
They can assume various states and forms described with fancy names like akinetes, quiescent vegetative cells.
These are often described as ways that cyanobacteria “hibernate” – but that implies they just go to sleep and wake up again in spring.
But in reality, what they do is more like hunker down, chill out and wait for any opportunity to get blooming again – so these are all ways of seeing out winter and coming out of winter in a state that means they are primed and ready to get a jump start on the true algae when the opportunity arises.
In 2018 this study in Western Lake Erie, found viable toxic and non-toxic Microcystis seed stocks in sediments after winter, indicating how Microcystis can survive winter and lead the way to early bloom initiation
This study showed that in some lakes, cyanobacteria don’t simply disappear or hibernate in winter. They can remain active even under ice.
And this one found that winter temperature can influence whether Microcystis remains more sediment-associated or persists in the water column through winter – showing their tactics are adaptable, and that different winter conditions can shape spring toxic HAB risk.
This study explains that cyanobacteria can persist through winter as overwintering cells, and that effective management has to account for this if we want HAB prevention rather than reactive chemical treatments for HABs after they happen – which of course is what the Government Accountability Office report called for.
By definition – HAB prevention cannot begin after the toxic HAB bloom becomes visible – because by that time cyanobacteria have survived the winter, reactivated, and begun building the next bloom before most lake managers are paying attention.
The key point is that many cyanobacteria are not simply “fresh algae” that show up when the water gets warmer.
They can persist through unfavorable conditions as overwintering cells of various sorts, and when environmental conditions become favorable again, these cells can act as an inoculum that kick starts the next bloom early, pre-emptively establishing cyanobacteria dominance, well ahead of the beneficial algae.
[04:34] The Myth of the Winter Reset
In plain English, a eutrophic lake already contains the cyanobacterial seed stock for next season’s HAB long before spring even arrives.
So the idea that winter resets the lake and levels the playing field for the phytoplankton to all line up equally on the start line again in spring has been shown to be completely wrong.
Winter is the time when cyanobacteria can consolidate their position and prime themselves to exploit any change in conditions that might suit them in late winter or early spring as soon as they happen and before the beneficial algae can get started.
So if winter was a blank space on your lake management calendar, that’s when the cyanobacteria got a jump on you, and now you are paying the price.
[05:26] The Perfect Storm: Nutrients and Turnover
So what might those favorable conditions be that cyanobacteria can take advantage of to get a jump start?
To understand that we need to begin by reviewing the role of lake turnover, how that is changing in many lakes and how nutrient recycling from the accumulated sediment nutrient stockpiles plays into things. You can get the full story on that in this video – but the short version is – warmer winters have often meant that only partial lake turnover occurs, so a permanent hypoxic dead zone remains at the bottom of the lake, year after year, allowing sediment nutrient recycling to continue throughout winter – perfect conditions for cyanobacteria
This research showed the link between the reactivation of resting-stage cyanobacteria and nutrient availability that can trigger early Microcystis blooms and shows that elevated orthophosphate availability does exactly that.
This review confirms that orthophosphate is the immediately bioavailable phosphorus form and that cyanobacteria have multiple phosphorus-utilization strategies that they use to maximize how they benefit from its availability.
And this paper explains why chemically reduced nitrogen forms, especially ammonia, fuel cyanobacterial blooms
And those conditions where nutrient availability can reactivate resting-stage cyanobacteria can be created when there is only partial Fall lake turnover and the organic sediment recycles ammonia and orthophosphate as the bottom water becomes hypoxic again in winter.
[07:21] How Cyanobacteria Get a Jump Start
So if we have cyanobacteria wintering over poised, ready and able to bloom at the first opportunity, and the sediments covered by hypoxic water, supplying recycled nutrients – how do they come together in a perfect storm to help the cyanobacteria bloom and produce toxic HABs?
This paper shows that dormant cyanobacteria in the sediments are easily resuspended, into the overlying water – as could happen at spring lake turnover or from physical agitation from wind in shallower water – and then when temperature and light conditions are favorable the cyanobacteria capitalize on what for them are perfect storm conditions to bloom.
And resuspension of even a small fraction – less than 1% – of the sediment seed stock can be enough to seed those blooms, and summer bloom dominance is influenced more by growth rate than initial seeding numbers, so earlier resuspension and activation of just a little seed stock gives enough of a head start for cyanobacteria to beat out beneficial algae. It’s the compounding effect of early growth that wins out in the end.
And this study showed that dormant stages can respond surprisingly quickly when light, temperature, and nutrients align early, so they are fast out of the blocks and blooming before the beneficial algae have got their running shoes on and tied their laces.
To show you this in action, in May 2022 this was the percentage break down of cyanobacteria and beneficial algae in this lake – over 95% of the phytoplankton was cyanobacteria.
And here is some data from a project that we just managed to get underway in March this year – and this is what the percentage breakdown was in that lake at the end of February – just under 50% cyanobacteria coming into spring.
This problem is real in way too many lakes and too many people don’t realize it until it’s too late.
[09:42] The Prognosis: Earlier, Longer, More Intense Blooms
So what are the implications and the prognosis if your lake has gotten off to a bad start as far as HABs are concerned?
Let’s see what the research says about earlier HAB blooms.
The news is not good – research has been clear for a long time now that as lakes succumb to cyanobacteria infiltration and subversion, toxic HABs start earlier in the year, are more intense and last longer.
In 2014 this study showed that warmer springs were linked to blooms beginning 20 days earlier in Lake Taihu over 20 years from 1991 to 2010.
By 2019 this study showed that bloom start dates had advanced 30 days between 2003 and 2017 – that’s an average of about 2 days earlier per year.
More recent research extends that concern by showing not only earlier bloom onset, but also longer bloom duration, which is exactly what the management problem is: the risk window is widening.
This study in Lake Erie reinforces why this matters, because the start date, peak date, and end date of a bloom all shape exposure risk, treatment time, and public warning decisions.
And when we step back to the larger-scale studies, the pattern is no longer an isolated lake story. Earlier, longer, and more frequent bloom seasons are becoming part of the broader global HAB management reality.
So the more of a stranglehold the cyanobacteria have, the more of a stranglehold they get.
[11:35] Cyanobacterial Succession
On top of that, there’s the phenomenon of cyanobacterial succession – which is the fact that the type of cyanobacteria that can take advantage of late winter conditions are not necessarily the same ones that reign supreme in summer.
Cyanobacteria seem to work in concert and conspire to handover from one species to another as the year progresses – as though one group prepares the way for the next so as to maintain cyanobacterial dominance for as long as possible – and all year if possible.
We’ve seen as many as 6 different cyanobacteria species dominate the phytoplankton population one after the other in a lake over the course of a year.
But there’s no real conspiracy happening. That’s just us anthropomorphizing!
The lake is simply remaining locked-in to a cyanobacteria-favorable state. Small changes at the margin in temperature, nutrients, light, mixing, or watershed inflows may tip the advantage from one cyanobacterial type to another and they respond accordingly – but the real problem is that the lake as a whole remains conducive to cyanobacteria all year and beneficial algae just never get a chance to re-establish themselves as long as that continues.
So cyanobacterial succession is real, and it matters, but it’s not a conspiracy – and the solution is still to get rid of the root cause conditions that keep favoring cyanobacteria in the first place.
So what can you do? It may sound like its all beyond your control – well you can’t control the weather, and earlier or warmer spring-times, but you can fix the root causes of the problem to help Nature rebalance the phytoplankton in your lake and marginalize the cyanobacteria.
[13:17] Panic Firefighting vs. Strategic Prevention
If you already have cyanobacteria showing up for Memorial Day weekend it becomes a question of balancing short-term tactics and long-term strategy – panic firefighting and strategic fire prevention.
If you feel you have no choice other than to engage in chemical warfare in your lake this summer – using algaecides and phosphorus precipitants – then at least do so with your eyes wide open – you are putting lipstick on a pig and the pig is going to get uglier and nastier once you do – you can learn more about what algaecides do here, and you can learn about what phosphorus precipitants do here.
But understand that if you opt for these chemical treatments, you are taking a conscious decision to pay good money now to make the situation worse in the long term.
So you also need to take the conscious decision to change strategic direction and take action now, so that you have a toxic HAB prevention program in place before Fall,
That way you can make sure that you don’t go through the same vicious cycle again next winter that results in the same situation – or worse – next Memorial Day.
The science is clear –
These papers all tell you that you need to be monitoring lake conditions in winter and early-spring.
These papers say you should be measuring dissolved oxygen profiles, ammonium, orthophosphate, phytoplankton composition, in winter so you can be proactive in preventing HABs in spring.
And these papers explain that you should target the root-cause drivers: organic sediment accumulation, oxygen depletion, internal loading, nutrient availability, and cyanobacterial seed stocks.
[15:09] The Proof: Active Winter Management Works
Here’s the proof that you need to see to know that you can in fact actively manage your lake through winter and prevent toxic HABs.
Remember this lake had 95% cyanobacteria in May 2022? Well after effective management through the winter of 2023, this is what the phytoplankton population looked like in May 2024 – and June 2024.
And that lake that we just got started on about 8 weeks ago in March – they are going into Memorial Day looking like they’ll have a good healthy lake this summer after all.
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