Monitoring in Lake Scugog in 2015

Is what happened here on Lake Scugog a harbinger of things to come in the Kawarthas and Trent-Severn Waterway?

Dr. Ron Porter – Chair Science and Monitoring, Scugog Lake Stewards and Barbara Karthein, President, Scugog Lake Stewards

As lake monitors, we learned first-hand in 2015 that if we are to observe the annual changes in Lake Scugog and the effects of time and the environment on the ever-changing flora and fauna, we have to make frequent and knowledgeable visits to the lake armed with a reasonable understanding of what we are looking at, backed up by professional colleagues to confirm what we see.

All volunteer monitors were given an aquatic plant ID manual as a gift from the Scugog Lake Stewards’ Board. In addition, the research group of the Stewards made monthly pontoon boat patrols during which observations on the status of the lake were made over the spring and summer. Others, interested in the project, were invited to accompany us on these trips. We were particularly delighted to welcome aboard local students who plan a career in lake science.

Dr. Andrea Kirkwood, a Professor in the Department of Biology at UOIT, joined us on our September patrol. We then added her academic experience to that of Dr. Eric Sager of Trent University who made the initial critical observation of what was truly afoot in Lake Scugog in 2015.

From past experience, we had anticipated a summer of observing thick masses of invasive macrophytes have a detrimental effect on the enjoyment, health and beauty of the lake. Hybrid Eurasian watermilfoil (EWM) had made huge inroads in extensive sections of the lake in recent years. This was occurring to such a degree that our scientific team had been planning to do a series of studies in 2015 on the use of jute matting as a benthic barrier in an attempt to contain the growth of the EWM in strategic areas.

Throughout May, June and early July 2015, our monitoring and sampling showed the entire observable lake bed covered by vegetation to a density of 95% or greater. Not by EWM as in previous years, but what we took to be the alga, Chara, which we had noted in past years in only small pockets in the lake. Among the billowing meadows of Chara, we noted occasional invasive species such as EWM and native plants including Coontail, Bladderwort, Broad-leaf Pondweed, Canadian Waterweed and White Water Lily growing in small patches in secluded bays.

Starry stonewort, a tangled mass of alga that can grow to within 2 inches of the surface of the water and reduce fish habitat greatly.
Starry stonewort, a tangled mass of alga that can grow to within 2 inches of the surface of the water and reduce fish habitat greatly.

We asked Dr. Eric Sager of Trent University and Fleming College about this new phenomenon. After a visit in mid June, Dr. Sager determined that much of what we took to be Chara was actually the alga Starry Stonewort (Nitellopsis obtusa) (SS), intermingled with the Chara. Starry Stonewort is a plant-like alga that looks like tangled light green fishing line and which grows in thick billowy clouds, up to eight feet thick, which can reach almost to the surface of the water. It is identified by tiny bulbils that look like stars on the glass strand-like stabilizers the alga has to connect it to the benthic layer. These strands are not roots.

This alga, which is amazingly on the endangered species list in the United Kingdom, is considered a problem invasive in North American lakes and a danger to our fisheries. It can reduce habitat for both fish and the benthic bugs that they prey on. This information prompted a keen interest by the Stewards to learn more about this new invasive.

We made a further intriguing observation where the Nonquon River flows into lake Scugog. In place of the usual modest stands of wild rice, at the mouth of the river, we now found acres of mature rice. In the path of the nutrient rich plume of river water as it flowed north toward the Scugog River, we observed a massive and apparently healthy growth of Sago Pondweed. What did these new observations mean? Are wild rice and a small number of native aquatic plants able to out-compete SS?

Starry Stonewort is an ancient alga which can, when conditions are right, seemingly invade a lake opportunistically and extensively. In one winter, it appears to have grown to dominate the aquatic plant life in Lake Scugog both in shallow waters and at much greater depths, taking advantage of what seems to be the total collapse of hybrid Eurasian watermilfoil.

The history of the arrival of this invasive in lakes and rivers of the St. Lawrence and Lake Erie watersheds over the past twenty years has not been this dramatic.

Because of the seeming collapse of the hybrid Eurasian watermilfoil, the change in lake vegetation in Lake Scugog in one season was dramatic. What caused this? Could the predominance of this new alga have possible negative consequences for our fishery? Why might the nature of SS be so different than its counterpart in Europe? Might we be facing a new and stronger hybrid of Chara and SS as we had with EWM? Was the colder, rainy weather, and high water levels in Lake Scugog in recent years an important factor to these changes?

Starry stonewort
Reproductive method for starry stonewort; tiny star-like bulbils found near the base of the plant.

It was decided to bring together, for a roundtable table meeting, colleagues from Kawartha Conservation, the Ministry of Natural Resources and Forestry, Trent University and UOIT. This meeting was held in Port Perry in October, 2015. We will continue these connections this year and will hold a second roundtable in September 2016. Further, in an attempt to answer some of the questions which have arisen about Starry Stonewort and what effect it may have on our fishery, we are planning extensive research with Dr. Kirkwood in the next few years. As the head water body of the Kawartha Lakes system, what happened in Lake Scugog in the summer 2015 may have major implications for the future downstream.

This year has seen a metamorphosis in Lake Scugog, from a lake overgrown by EWM, to a pristine environment with clear, relatively plankton-free supernatant and the presence of all the invasive and native aquatic plants of past years reduced by the light-shading Chara/Starry Stonewort biomass. To the average viewer these apparent changes in the health and beauty of the lake have increased its appeal to boaters, fishers and those living on the lake alike. What these changes mean for the fishery and for our lake in the years ahead will be shown by the passage of time.