Plankton
Plankton consists of organisms that live in the water column and are not strong swimmers. Many plankton species are microscopic or very small, although this category does include jellys. Plankton are an important component of the food web.
In the three lakes, we study two groups of plankton: phytoplankton and zooplankton. Phytoplankton (also called algae) are primary producers, capable of converting the energy in sunlight into starches, creating oxygen in the process. Often colored green, they function somewhat like plants. The other group is zooplankton, which eat the phytoplankton and are in turn eaten by fish. Thus, zooplankton are analogous to animals that graze on plants, and in turn become prey to larger animals.
Phytoplankton
We encounter three types of phytoplankton in our lakes. The first, and the one we don’t talk about very much, is macroalgae. This algae appear as large branching structures that can look like plants, but they don’t have any of the structures found in plants. Macroalgae are rarely a nuisance, although an invasive macroalgae, starry stonewart, is appearing in more area lakes.
Filamentous phytoplankton are long strings of algae. Sometimes these attach to the bottom, sometimes they drape over plants, and sometimes they make up big “clouds” in the water that look like green cotton candy. Filamentous algae can float to the top and look like bubbling green scum. The term periphyton describes filamentous algae that is attached to rocks or plants.
Unicellular phytoplankton consist of individual cells or colonies of cells that float in the water column. These can
give the water a green, brown, or sometimes red tint. At high densities, these form algal blooms that can reduce water clarity. Some blooms of blue-green algae (or cyanobacteria) are harmful algal blooms (HABs) because these algae have the potential to produce toxins.
Unicellular phytoplankton have their own subgroups, including diatoms, green algae, golden algae, and blue-green algae. These algae cycle through growth patterns during the summer, although with warming weather and heavier rainstorms, that typical seasonal progression can be disrupted often.
Our studies show that blue-green algae often dominate in our lakes for most of the year. Blue-green algae are lumped in with other algae, but they are actually a bacteria that can photosynthesize, called cyanobacteria. Cyanobacteria are a concern because they can produce toxins that can be harmful to humans and pets. Toxins may occur during a cyanobacteria bloom, so avoid green and scummy water.
As of 2023, NYSDEC identifies cyanobacteria blooms, or Harmful Algal Blooms (HABs), by their visual appearance. They no longer rely on algal samples, cell counts, or toxin screens.
Zooplankton
Zooplankton are an important link in the lake food web, since they typically feed on algae, and become large enough that fish will eat them. Three key types of zooplankton are in our lakes. Rotifers are the smallest. Cladocera are usually very common. Sometimes called water fleas, cladocera can be voracious consumers of algae. Copepods are found almost exclusively in lakes, not streams.
Zooplankton can be effective at knocking down the amount of algae in lakes, but they are most effective eaters of diatoms and green and brown algae. Unfortunately lakes with alewives (fish that eat zooplankton) often have lower levels of zooplankton and thus higher levels of algae.
Reports
Three Lakes Council has taken a point in time sample of plankton at each of our lakes since 2013. We take open water samples in late July on all three lakes to provide year to year data for this analysis. While plankton can vary hour by hour and day by day, we hope this will alert us to major disruptions.
In 2023, overall algal levels were high, and dominated by green algae on Waccabuc and Oscaleta, while Rippowam had more cyanobacteria. All three lakes had more zooplankton in 2023 than in 2022, and all were dominated by rotifers.
In 2022, overall algal levels were reduced compared to 2021, and cyanobacteria continued to be a dominant algae species in our lakes. Zooplankton appeared to rebound closer to levels previously observed in our lakes.
In 2021, as residents know, we had much higher than typical levels of algae on Waccabuc and Oscaleta, while Rippowam had an average year. And, after a boom in 2020, zooplankton levels plummeted in 2021. This is not good news, since zooplankton both consume algae, and are eaten by fish. See the 2021 summary.
In 2020, our summary report shows average levels of algae, and surprisingly high levels of zooplankton for our lakes. See the 2020 summary.
Our 2019 report, based on the July samples, indicated lower than typical levels of algae in Waccabuc, moderate levels in Oscaleta, and typically high levels on Rippowam. In all our lakes, the amount of cyanobacteria was down from 2018 levels. Zooplankton were moderately to high in abundance on all three lakes, with more balanced diversity than typical for our lakes. See our 2019 Plankton Report.
In 2018, we saw a widespread algal bloom in June and early July on Lake Waccabuc, and those algal results are summarized in our CSLAP report. In general, our lakes show increasing levels of algae, especially in 2017 and 2018, and on Oscaleta and Rippowam, more of that algae consisted of blue-green algae, or cyanobacteria. Zooplankton levels are also higher, supported by the increased algal food supply, but unfortunately the best algae predators, cladocera, do not dominate the mix. See our 2018 Plankton Report for more details.
Want even more? Our 2017 Plankton Report, showed generally higher levels of both algae and zooplankton in each of the lakes, and relatively high levels of blue-green algae. You can also read the phytoplankton and zooplankton report from 2016.