Millions of Visitors Invade Huron Overnight

Huron residents awoke to the invasion of millions of mayflies (Hexagenia limbata) this morning.  Apparently, the prevailing winds were just right to lead the insects into Huron.  Though the insects might seem bothersome, their presence is an indicator of a healthy Lake Erie.  In the early 1990s, no Hexagenia could be found in Lake Erie due to toxins in the sediments.  As the Lake has recovered from the abuse it suffered in the early part of the 20th century, so has the mayfly population.

Mayflies spend the majority of their life living deep in the sediments of lakes.  The mayflies

that you see covering the buildings of Huron are currently non-mating adults known as subimagos.  Over the next 24 to 48 hours, the mayflies will undergo their final molt and become adults.  You might notice their shed skins clinging to screens and other hard surfaces.  During this period, they do not eat-they do not even have mouth parts.  The only purpose of the adult stage of the mayfly’s life is to mate.  Once mating is complete, the adults die.

The females will lay their eggs in the water just after mating.  The eggs remain in the sediments until the spring when they hatch.  Once hatched, the mayfly is considered a nymph.  The nymphs will go through several life stages called instars.  They may experience as many as 30 instars that can take anywhere from 14 to 22 months.  During each instar, the mayfly sheds its skin or molts.  The nymphs breathe by moving their feathery gills, located along their abdomen, thus increasing the amount of water that passes over them and aiding in oxygen absorption.  The final nymphal instar swims to the surface and molts into a subimago.  Nymphal development time is temperature dependent, so development times vary.  In general, the emergence of the subimagos occurs during June and July. 

Mayfly nymph

Living near the shores of Lake Erie has many benefits.  It is up to you whether you deem the emergence of the mayflies as one of these benefits!  Frankly, I think they are a beautiful insect, though the numbers in which we are seeing the mayflies today is a bit overwhelming.  Remember, the mayflies will only remain here for a short time, so we will be free of them soon or at least until the next hatch.

New Monitoring Tools to Help Keep Track of Water Quality

Algal blooms in Lake Erie are a reality.  Though not as bad as those seen in the 1960s and 1970s, algal blooms (both harmful and non-harmful) occur on an annual basis in Lake Erie.  The National Atmospheric and Oceanic Administration (NOAA), in junction with Heidelberg University’s National Center for Water Quality Research, has developed a new monitoring program to predict the severity of algal blooms based on the combination of current measurements of phosphorus loading from the Maumee River for the season to date with historical records from past years.  According to NOAA, “The severity of the western Lake Erie cyanobacterial harmful algal bloom (HAB) is dependent on phosphorus inputs from March 1st through July 31st, henceforth the loading season.  Based on 12 weeks of data (March 1- May 23, 2015), the extensive severe blooms observed in 2011 and 2013 are not projected to occur this year.”  The positive outlook for Lake Erie this year is due to a relatively dry spring which resulted in less discharge and lower phosphorus loads into the western basin.  Yet, NOAA stresses that there is some uncertainty in their projection because the loading season still has 2 months to go.  Updated forecasts for the algal blooms will be released by NOAA periodically.

In addition to the potentially harmful algal blooms, those wishing to enjoy Lake Erie’s beaches should be mindful of bacteria levels.  The Erie County Health Department monitors water quality near 25 beaches in the county four times per week from Memorial Day to Labor Day.  According to their Erie County Health Department’s website, “Our employees strive to ensure that unsafe swimming conditions are communicated to Erie County residents as quickly as possible and in doing so reduce the risk of unwanted illness in the swimming public.  Our Sanitarians collect and analyze samples for the presence of E. Coli bacteria, which is a good indicator of bathing water contamination and if present increase the risk of disease transmission to swimmers.”  The health department findings have a one-day delay from time of sampling to reporting.  These results are reported in local newspapers, announced on local radio stations, and are available on their website (www.eriecohealthohio.org/environmentalhealth.html).

The results provided by the Erie County Health Department are a valuable means of alerting beachgoers of potentially harmful bacteria.  The methods employed by the Health Department involve collecting water samples from their 25 selected areas, transporting the sample to a laboratory, and determining the numbers of E. coli in the sample.  Unfortunately, there is a delay in the reporting because it takes at least 18 hours to grow E. coli in the laboratory.  Hence, by the time these results are available, water-quality conditions may have already changed.  In an effort to provide real-time forecasting of E. coli levels, a system called Nowcast has been created as a result of multi-year partnerships on several projects between the U.S. Geological Survey (USGS) Ohio Water Science Center (OWSC), and other federal, state, and local agencies and universities.  Nowcast uses predictive models based on easily obtained measurements such as rainfall and wave height to estimate levels of E. coli and to calculate the probability that the bathing-water standard will be exceeded.  The calculation and reporting of these results takes less than an hour.  Nowcast has been in use since 2006 for Hunting Beach in Bay Village.  Other beaches have been added to the monitoring program since then.  Ohio is currently monitoring nine sites including Nickel Plate Beach in Huron and Main Street Beach in Vermilion.  Nowcast results are updated by the Erie County Health Department by noon on Monday through Thursday during the swimming season and can be found on the Nowcast web site (www.ohionowcast.info/index.asp).