Dearth of aquatic plants in south basin leads to dangerous algal blooms, habitat loss
LAKEWOOD, NY Jan. 6, 2020 – A third-party’s 2019 fall survey of the habitat of Chautauqua Lake, a waterway that supports a rich economy based on sports fishing, recreation, vacation rentals and tourism, found the lake’s status had “skewed radically from the norm,” essentially creating two lakes, a vibrant, normal one north, and a barren, vulnerable one south.
A 158-page report from the independent and well-respected Racine-Johnson Aquatic Ecologists of Ithaca, NY states in unusually stark language for a scientific paper the changes observed. It documents how Chautauqua Lake exists in two extreme parts, with the south basin a barren lake floor where “data shows critical decline from a healthy sustainable littoral ecosystem;” and the north basin, where aquatic plants continue to grow well, buffering against dangerous algal blooms witnessed in the south basin last summer.
“Our late-summer/early-fall 2019 plant survey results came as a shock, and should alarm the stakeholders of Chautauqua Lake,” states the annual report prepared independently for the Chautauqua Lake Association. The report uses “macrophytes” as a scientific term for aquatic plants in the lake, where 27 species were found, none of them newly invasive.
“The outcomes we normally expect, after 18 years of consecutively collecting variable aquatic plant and invertebrate community data from Chautauqua Lake, skewed radically from the norm,” the report’s authors wrote. “The submersed aquatic plant growth in the north basin, north of Long Point, was normal and anticipated for a fall survey, generally good-to-excellent water clarity and a healthy growth of desirable macrophytes. South of Long Point, blooms of phytoplankton were obvious and did not dissipate during our survey.”
The survey, from Sept. 17 to Oct. 1, 2019 generally involved the rake-toss method of collecting plants to determine density and variety. The New York State Department of Environmental Conservation recently issued bid invitations for a three-year state project requiring use of the same certified approach, which involves gathering plants from the lakebed and analyzing their health and frequency.
What caused this radical change in the lake’s south basin? In spring of 2019, the herbicides 2,4-D and endothall were applied in near-shore areas south of Long Point. The report concludes these herbicides were highly effective, doing their job of killing nearly all plant life in those areas. But the report states that such removal is “detrimental to the health of the lake’s ecosystem.” The survey also found the herbicides killed well beyond a specific application zone, due to inevitable drift of the chemicals in the water column.
“The stakeholders of the lake may, or may not know, or recognize, what happened to Chautauqua Lake south of Long Point in 2019,” the report says. “The stakeholders that fish in the lake, who spend time at the shoreline or in a boat, have noticed that the summer months in the south basin, in 2019, were not the usual. However, this fall other stakeholders accepted the news reports, internet posts and a third-party report that the management of aquatic macrophytes by the application of aquatic herbicides, south of Long Point, on Chautauqua Lake in 2019, was a success and beneficial.”
“We agree, the application of the herbicides 2,4-D and endothall on May 15-17, 2019 was successful in removing macrophytes from large areas of the lake’s littoral zone (where plants grow). Conversely,
we do not agree that this almost total plant removal in those areas was beneficial, but rather it was detrimental to the health of the lake’s ecosystem.”
“The management decision to prohibit herbicide use north of Long Point in 2019 was astute and that decision must remain,” the report concludes.
The annual survey, according to the report, found few plants in the south basin, concluding that: “A decrease in macrophyte species diversity, richness and biomass has the potential of leading to a decline of a world-class, warm-water fishery dependent on the habitat that aquatic plants provide.”
“Since 2002, we have recorded for 17 years in the south-east end of Chautauqua Lake aquatic plants and macroinvertebrates as part of a vibrant lake ecosystem, while in the 18th year our data shows large areas in critical decline from a healthy sustainable littoral ecosystem,” the Racine-Johnson ecologists wrote.
In addition, since the herbicides were applied to water, its fluidity distributed them beyond the areas permitted for treatment, the report found. This finding, therefore, “clearly suggests the drift and concentration of 2,4-D was vast and basin-wide, likely contributing to the massive indiscriminate defoliation of the macrophytes in the south basin.”
“The wholesale loss of macrophytes may push the south basin toward a phytoplankton-dominated turbid state, void of many of the submersed plants, invertebrates and fish that have inhabited this
littoral zone historically,” the scientists continued. “While the south basin could recover quickly, it is likely to be a slow return to normal macrophyte growth with HABs [harmful algal blooms] currently having the advantage.”
According to the National Oceanic and Atmospheric Administration, harmful algal blooms, or HABs, occur when colonies of algae – simple plants that live in the sea and freshwater – grow out of control and produce toxic or harmful effects on people, fish, shellfish, marine mammals and birds. “The human illnesses caused by HABs, though rare, can be debilitating or even fatal,” the agency states.
Among the report’s additional conclusions:
- The importance of having a robust healthy macrophyte community in the littoral zone of Chautauqua Lake is essential to the survival of this large, shallow lake. A decrease in macrophyte species diversity, richness and biomass [have] the potential of leading to a decline of a world class, warm water fishery dependent on the habitat that aquatic plants provide. Loss of macrophytes from the littoral zone in a large eutrophic shallow lake, like Chautauqua, will dramatically increase nutrient loading and shoreline erosion into the water column by allowing an increase in wind driven waves to whip up the bottom sediments and pound the shoreline. The loss of plant structure that provided refuge for the phytoplankton grazing zooplankton from planktivorous fish can lead to a zooplankton decline allowing phytoplankton and cyanobacteria to increase.
- Therefore, conservation of these essential biological control agents is paramount in maintaining a healthy Chautauqua Lake. Protection from the wholesale elimination of macrophyte species from the littoral areas must be the top consideration in the long-term management of the lake. With the loss of macrophytes from large sections of the south basin, those areas will likely experience a decline of macroinvertebrates, the fishery and water clarity along with increased phytoplankton blooms and corresponding low oxygen levels. The management decision to prohibit herbicide use north of Long Point in 2019 was astute and that decision must remain. Prohibiting herbicide usage in crucial fish habitat specifically used for spawning and nursery is paramount as suggested at an earlier time in areas like Tom’s Point, Whitney Bay and Irwin’s Bay. The decision in 2020 for managers and stakeholders of Chautauqua Lake is how to improve the lake ecosystem south of Long Point while continuing protection to the north.
Racine-Johnson Aquatic Ecologists of Ithaca, NY, was formed by Robert Johnson upon his retirement as Cornell University’s Cornell Ponds Manager. Johnson has been monitoring aquatic plants and herbivores in Chautauqua Lake annually since 2002 under contract to the Chautauqua Lake Association as an independent monitor. Racine-Johnson also performs third-party consultant herbicide-monitoring for NYSDEC and other lake associations.
The Chautauqua Lake Association traces its beginnings to 1946 and its actual formation in 1953. The current focus is to perform environmentally sound plant-control practices, undertake scientific monitoring and relevant research, service the shoreline in promotion of maintaining healthy conditions, and promote educational efforts to enhance public understanding of lake association methods and lake needs. Since 1954, the CLA has sponsored lake improvement projects, has performed lake maintenance services, and has facilitated on-going scientific monitoring and research. The CLA is a charter member of New York State Federation of Lake Associations (NYSFOLA). For more information, visit http://chautauqualakeassociation.org/about-us/history/