- [Jasmine] It's on Muskegon Lake, which is good. We also saw some changes in the cyanobacteria community composition over time, as well, so. Very briefly in group one, which goes from 2003 to 2008, we saw a complete domination by the genus Microcystis. In group two we kind of saw this diversification of the cyanobacteria community. And then in group three, we saw this return to dominance, or at least co-dominance by Microcystis. And then there were a few years in there that didn't conform to their groups: 2003, 2015 and 2019. And these are the results of the NMDS, and we can see that if we point out those three groups on this ordination again, the groups kind of lumped together on the ordination and that first group of years, which was, again, dominated by Microcystis associated with high ammonia in the spring, high total phosphorus in the summer and then high total Kjeldahl nitrogen in the fall. Group two was centrally located, which indicates intermediate values of all variables. And then group three, which was again dominated by Microcystis, associated with high temperatures in the spring, high nitrate in the fall and summer and high total phosphorus and cyano- reactive phosphorus in the fall. So, going over the discussion very briefly, essentially HABs have reduced on Muskegon Lake tremendously. Which coincided with an increase in water quality and a significant reduction in nutrients, which is a great thing. And I believe that nitrogen was a much more influential nutrient than phosphorus in this case because phosphorus concentrations were really pretty low throughout the whole study period and didn't vary a ton. So I think it was mostly the reduction in reduced nitrogen, which is what cyanobacteria prefers, that led to the reduction in HABs. We also saw that temperature, total Kjeldahl nitrogen, which is made up of ammonia and organic nitrogen, and chlorophyll A increased over time. And I think that the increase in chlorophyll was likely driven by the increase in temperature since that would increase vital plankton growth rates. And then the increase in TKN might be due to an increase in organic nitrogen bound up in phytoplankton biomass, but it also might represent kind of a new source of organic nitrogen to the system. Which might be a little bit concerning, It's definitely something to keep an eye on in the future. [ Moderator] Jasmine? [Jasmine] Yeah? [Moderator] Just wanna let you know we got five minute warning right here. And we have a couple questions too. [Jasmine] Okay. [Moderator] But you can keep going if you'd like. (chuckling) [Jasmine] Okay. I'm just gonna very briefly run through the second portion, my second objective. And then I will (laughs) unfortunately call it quits. So, essentially the year 2019 was a very anomalous year in terms of weather. Mostly because it was a very cool year and also because it was a very rainy year. And what this led to was complete domination by diatoms in Muskegon Lake, which had never been seen before. And essentially that was because the temperature regime and the precipitation favored them because they prefer cooler temperatures and they need frequent mixing to reduce their risk of sinking. And then the weather patterns kind of disadvantage other genera, especially the cyanobacteria, which prefer a warmer water temperatures and a more stable water column. And I will leave it at that. Again, I am so sorry everybody. My internet never goes out and it just chose to do it at the very wrong time. (chuckling) So I guess I can take some questions now. [Moderator] Sure, the question we had a little while back was have you ever used EXO2 sonde for collecting data? [Jasmine] I'm sorry, I can't see the chat. So I'm not sure what that means. What was the word before sonde? [Moderator] EXO dash two. [Jasmine] Oh no we used YSIs and some SUNAS and some other ones that were attached, but mostly YSIs to collect our environmental data. [Moderator] And we have a quick question. Can you go back to the previous slide before? Thanks. All right and another question I have is is your thesis published and accessible anywhere? [Jasmine] I'm working on publishing it right now. It's kind of on a embargo period with the university for two years, and then I hope to submit it to a journal. So hopefully it will be published in the next half year or so. [Moderator] I think that is it for questions unless anyone else has last minute questions right now. [Man] You sample at all on Bear Lake? [Jasmine] No, I haven't done any sampling on Bear Lake. I know they have in the past and Bear Lake has kind of historically been a major contributor to some of the pollution issues in Muskegon Lake, but I don't know that we, we sample the inflow of it into Muskegon Lake, but I don't know that we actually go into Bear Lake and do any sampling there. [Man] That's a result of that old Hooker plant upstream? [Jasmine] Maybe, I'm not too familiar with Bear Lake, I'm sorry. [Man] I just ask because I grew up on Bear Lake (chuckling). [Jasmine] Oh, okay, cool. (chuckling ) [Moderator] Someone asked do you know what caused the reduction in nitrogen? [Jasmine] So they did a lot wetland restoration, they did some restoration on some old celery farms. They also stopped dumping wastewater into the lake. They created the Muskegon Wastewater Treatment Plant, which, of course, helped. And there've been a lot of other types of shoreline restoration. And they've done some drudging from the bottom waters to kind of get rid of some of the legacy nutrients, but overall it was probably mostly the shoreline restoration and the reduction of wastewater. [Moderator] All righty, we don't have any more questions. Think we'll wrap it up right there. Renee did post a little survey in the chat. So please go over to that link and answer a quick two question survey. And... 'cause that'll greatly help us in feedback. And then I think that's it. [Jasmine] Okay, thank you guys for listening. And again, I am so sorry for the technical difficulties. [Moderator II] No hard feelings at all Jasmine. Thanks so much. [Jasmine] All right, thank you.

Bloom or bust: long- and short-term drivers of cyanobacterial blooms on Muskegon Lake, Michigan – a Great Lakes estuary - Part 1

From Renae Siler October 6th, 2020

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Muskegon Lake, a drowned river mouth estuary that empties Michigan’s second largest watershed into Lake Michigan, historically suffers from cyanobacterial harmful algal blooms due to cultural eutrophication. This study provides both a historical take on cyanobacterial blooms in Muskegon Lake and a focus on the year 2019. While visible blooms still form periodically on the lake during the summer and fall, a look into historical data from 2003 to 2019 reveals a major decrease in cyanobacterial abundance over time along with shifts in community composition in response to changes in nutrients and temperature. Additionally, the long-term dataset from the Muskegon Lake Observatory buoy revealed 2019 to be an anomalous year in terms of weather. Biweekly sampling of three sites on the lake during 2019 captured how the aberrant weather affected the phytoplankton community. With an unusually cool spring and the highest precipitation accumulation on record, the phytoplankton community saw domination in all seasons by an unexpected group – the diatoms. Though multiple genera were found, cyanobacteria comprised less than 2% of the phytoplankton community in 2019 – the lowest on record for Muskegon Lake. Further, an in situ bioassay with bottom water and river water as treatments and near-surface water as a control allowed us to explore which nutrients stimulate algal growth, identify the sources of these nutrients (internal loading v. river influx), and determine whether this source changed seasonally. We conclude that nutrient forms and concentrations drive cyanobacterial abundance and composition in Muskegon Lake on a yearly basis, but large-scale climatic events impacting regional temperature and precipitation can override the system. These findings provide an alternate perspective on the impacts of a changing climate on the phytoplankton community in Great Lakes estuaries. Lessons learned from this model Great Lakes estuary should be applicable to similarly impacted freshwater estuaries and temperate lakes.

Presented by Jasmine Mancuso, Grand Valley State University, during the 2020 Michigan Inland Lakes Convention

Tags: milc2020

Appears In: Agriculture Natural Science Agriculture Natural Science

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Bloom or bust: long- and short-term drivers of cyanobacterial blooms on Muskegon Lake, Michigan – a Great Lakes estuary - Part 1

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