Global solutions to regional problems: Collecting global expertise to address the problem of harmful cyanobacterial blooms. A Lake Erie case study

Abstract

In early August 2014, the municipality of Toledo, OH (USA) issued a 'do not drink' advisory on their water supply directly affecting over 400,000 residential customers and hundreds of businesses (Wilson, 2014). This order was attributable to levels of microcystin, a potent liver toxin, which rose to 2.5μgL^-1 in finished drinking water. The Toledo crisis afforded an opportunity to bring together scientists from around the world to share ideas regarding factors that contribute to bloom formation and toxigenicity, bloom and toxin detection as well as prevention and remediation of bloom events. These discussions took place at an NSF- and NOAA-sponsored workshop at Bowling Green State University on April 13 and 14, 2015. In all, more than 100 attendees from six countries and 15 US states gathered together to share their perspectives. The purpose of this review is to present the consensus summary of these issues that emerged from discussions at the Workshop. As additional reports in this special issue provide detailed reviews on many major CHAB species, this paper focuses on the general themes common to all blooms, such as bloom detection, modeling, nutrient loading, and strategies to reduce nutrients.

Keywords: CHAB; Cyanobacteria; Lake Erie; Microcystin; Nitrogen; Phosphorus.

Figure 1

The relationships between annual discharge (A) and annual flow-weighted mean concentrations and loads of dissolved reactive phosphorus (DRP [B and C]), total particulate phosphorus (TPP [D and E]), Nitrate-N [F and G] and total Kjeldahl nitrogen (TKN [H and I]) for the Maumee River at Waterville, OH. The percent change between 5-year running average values for 1994 and 2012 are shown for each parameter.

Figure 2

A comparison between Mehlich 3 phosphorus soil test levels in the agronomic zone (0-20 cm. cores) and the environmental zone (zone of interactions with runoff water – 0-5 cm. cores) for 1610 fields in the Sandusky River Watershed.

Figure 3

Summer 2015 surface water in situ chlorophyll a (black) and phycocyanin (gray) profiles expressed as relative fluorescence units (RFU) measured with an EXO2 sonde (YSI Inc.) deployed from a buoy at the city of Sandusky (OH) principal water intake in coastal waters of Lake Erie. Use of a multiparameter sonde resolved an algal bloom in mid-July (arrow) that was not dominated by cyanobacteria, thus guiding water treatment options by city utilities personnel.

Figure 4

Image of CHAB in west-central Lake Erie captured on July 28, 2015 by the Operational Land Imager (OLI) on Landsat 8. The CHAB enveloped the Lake Erie islands and continued into Canadian waters east of Point Pelee. The persistent CHAB in Sandusky Bay is also visible. Landsat imagery courtesy of NASA Goddard Space Flight Center and U.S. Geological Survey.

Figure 5

Annual acreage of winter wheat planted in the Maumee River watershed for counties in the states of A) Ohio B) Indiana and C) Michigan. Data from the United States Department of Agriculture National Agriculture Statistical Service (www.nass.usda.gov, accessed on Feb 4, 2015).

Figure 6

Tile drainage deployment in the USA. Key indicates percent of acreage drained by tile (data from 2012 US Census of Agriculture).

Figure 7

Mean summer alkalinity estimates for the three basins of Lake Erie since 1983. Data demonstrate a drop in CaCO₃ equivalents since the early 1980’s that is coincident with the invasion of D. polymorpha into the system. While some level of recovery has been observed in the Central and Eastern basins, alkalinity in the western basin remains low. Data from the Great Lakes National Program Office (courtesy. R. Barbiero).

Figure 8

Mean summer temperature in Lake Erie’s western basin since 1983. Surface water temperatures for the western basin of Lake Erie have increased ~ 0.05 °C yr^-1 (R² = 0.129, p = 0.066).