I grew up in northeast Ohio, not far from Lake Erie. For you Europeans, that’s one of the Great Lakes which separate the USA from Canada. For this reason – well, and the fact that I’m a planktonophile – I’ve been following the story about Toledo, Ohio’s, drinking water restrictions closely. Last weekend residents of Toledo were warned not to drink their tap water, swim in the lake, wash their hands or bathe in the water, or even to let their pets romp on the shores of Lake Erie. The reason for the ban? Lake Erie was experiencing a spectacular (to a plankton ecologist!) harmful algal bloom (HAB) – a proliferation of phytoplankton. This one was so spatially extensive it could clearly be seen from space, and even Buzzfeed and Huffington Post reported the event (pop culture media reporting on plankton!).
Toledo tap water samples were found to contain dangerous levels of microcystin, a biotoxin produced by the cyanobacteria Microcystis spp. The toxin can induce dizziness, nausea, vomiting, diarrhoea, and liver damage when ingested and even contact with the water may induce rashes. As far as HAB effects go, Microcystis’s aren’t the worst – some HAB taxa cause amnesia or even paralysis. Nevertheless, summer is hot and the ban on drinking water led the inevitable rush on supermarket bottled water which resulted in an area shortage.
This isn’t the first time Lake Erie has been impacted by a HAB. In 2011 an enormous Microcystis bloom covered 20% of the surface area of the lake, causing a hypoxic dead zone, fish kills, and green sludge on the beaches. I was lucky enough to see that particular magnificent bloom from the air as my plane circled the lake to land in Cleveland (note: I was in the aisle seat and my seat mate was definitely not as excited about this event as I was. He was kind enough to take a photo for me though – check it out to the right). The reason HABs are interesting to me is because they are a clear example of where plankton and policy collide. Their human health, fishery and tourism impacts grab headlines and public interest, and are therefore of concern to local and regional policy makers. In fact, two current pieces of European legislation, the Water Framework Directive and Marine Strategy Framework Directive, contain objectives about limiting the occurrence and impacts of these events.
Like the 2011 Lake Erie HAB, the current Microcystis bloom was likely caused by nutrient run-off from land, a symptom of eutrophication. Lake Erie has suffered from eutrophication historically; in the 1960s and 1970s the Lake was so eutrophic due to agricultural nutrient run off, sewage inputs and industrial pollution its waters were the colour and consistency of pea soup (the Cuyahoga River in Cleveland also caught on fire but that’s another story). During the 1980s the US and Canada, in a stunning example of transboundary ecosystem management, implemented a programme to reduce harmful inputs and clean up the lake (the accidental introduction and spread of the invasive zebra mussel, Dreissena polymorpha, which filtered phytoplankton from the water, also helped). During my childhood Lake Erie was a place to sail, fish and swim. So, why the resurgence of eutrophication symptoms? Lake Erie is fundamentally a different ecosystem than in it was 40 years ago and one key reason for this (amongst other anthropogenic pressures such as wetland loss, invasive species and aging sewage systems) is climate change. In the North Sea, warming temperatures have been found to exacerbate eutrophication and that could be what is happening in Lake Erie. In other words, warmer waters are more sensitive to nutrient loading, and nutrient levels which previously may have been too low to generate a HAB now make these blooms possible. If this is indeed the case in Lake Erie, I hope policy makers make hard and difficult choices about nutrient management in the catchment, as I want future generations to have the happy memories of a healthy lake that I have.
Abigail McQuatters-Gollop, Plankton and Policy