There’s no free lunch, as the saying goes, and the tremendous Midwest economy driven by ocean-going ships moving goods between the heartland of North America and the rest of the world has brought problems to the Great Lakes. More than 180 non-native plants and animals have entered the system, many of them hitching rides on ships leaving ports across the globe and establishing themselves in these inland seas.
There’s no free lunch, as the saying goes, and the tremendous Midwest economy driven by ocean-going ships moving goods between the heartland of North America and the rest of the world has brought problems to the Great Lakes. More than 180 non-native plants and animals have hitched rides on ships leaving ports across the globe and established themselves in these inland seas.
Not all are harmful, but some have disrupted ecosystems, decimated native fish populations, and cost billions to battle. Their names are too familiar: think sea lamprey, alewife, and zebra mussels.
The ballast water that ships use to stabilize their loads have been a major accomplice in spreading these invaders. For years, the federal Environmental Protection Agency took the position that the Clean Water Act did not apply to normal operations of ships. Legal action by environmental groups forced the agency to begin to address the problem, by setting new rules for ballast water. The rules, which have evolved since the early 2000s, required ship operators to empty their ballast tanks in the open ocean and refill them with ocean water before approaching a port, either on the coast or in the St. Lawrence Seaway System. It was thought most organisms native to fresh water would not survive in the salty water.
The new routine has succeeded beyond expectations.
“We were averaging a new non-native in the Great Lakes every 28 weeks,” said Doug Jensen, Aquatic Invasive Species Program Coordinator for Minnesota Sea Grant. The organization is a partnership between the National Oceanic and Atmospheric Administration and the University of Minnesota, and is part of a network of 33 such programs in coastal states. “We’ve gone from that to zero. We’ve interrupted the pathways for introduction.”
Since the ballast water exchange requirement, the bloody red shrimp was found in Lake Michigan in 2006. It is possible it had arrived in the Great Lakes earlier and escaped detection. Based on its behavior in Europe, researchers think it could make its way into inland lakes in the U.S., and they are monitoring its spread. Less than half of the many non-native creatures that have come to the Great Lakes are considered invasive or destructive, and that could turn out to be true for the bloody red shrimp.
But Jensen and other experts don’t think the exchange requirement is enough. Ballast tanks are not simple tubs; they are built with internal structures, piping, and baffles designed to minimize water movement. Some have pockets that flushes won’t reach. “The doors are not completely closed; we know things are still moving around in ballast water,” Jensen said. A 2017 study found several non-indigenous species in ballast water carried by lakers, apparently picked up in the lower Great Lakes and headed for Lake Superior, where these particular species had not been recorded.
Searching for a way
Two U.S. labs are looking for other ways of preventing the spread of invasive species in ballast water. California State University’s Golden Bear Research Center in San Francisco Bay is one; the other is at the University of Wisconsin-Superior’s Lake Superior Research Institute in the Duluth-Superior harbor. In the basement of the UW-S science building, researchers are testing various treatments that could be used in ballast tanks to kill organisms that survive the mid-ocean flushing. In a test underway during a recent visit, a research specialist used a canoe paddle to stir water in a chest-high plastic tank. She had added organic matter to the tank to mimic water found in harbors, turning it the color of weak coffee. Then she seeded it with microbes, algae, or zooplankton to test an experimental control system. In this case, the treatment was ozone produced by a nearby generator. After a specified interval, the researchers counted how many organisms survive.
“People come to us from everywhere,” said Institute Director Matthew TenEyck. Inventors from such diverse fields as wastewater and drinking water treatment, medical devices and the flashbulb industry come up with ideas to kill foreign organisms, and the lab provides proof-of-concept testing at the “beaker scale.” This can answer the basic questions: does the system perform as designed? And does it create residual toxicity? “It has to be safe to discharge,” TenEyck says. “It’s easy and cheap for us to get those answers.”
Several approaches to kill non-natives in ballast tanks are currently being tested. Most begin with filtration, which can be improved by flocculation (getting very small particles to clump together so they can be removed by the filter). Beyond filtration, the primary methods are chemical disinfection (primarily with chlorine) and ultraviolet light, which can alter the DNA of the organisms to prevent reproduction.
But preliminary tests in the lab leave many questions unanswered. Scaling up to real-world conditions presents myriad challenges. “In the lab we use a small filter, we pour water through it and let gravity filter the water,” said TenEyck. “Ships can carry millions of gallons of ballast water. The water pressure is so strong that drilling a hole in an eight-inch-diameter pipe to collect a sample won’t work; the water just keeps surging through the pipe. We had to figure out how to penetrate that pipe and put a sample port in there that collects a representative sample,” he said. “And then, there are physical forces that literally change the shape of these animals: they’re soft-bodied and they can literally pass through that filter because of the pressure of the water.”
TenEyck and his colleagues confront these challenges at a bigger lab on a small pier in the Duluth-Superior Harbor. He is happy to show the facility to a visitor on a sunny September day. The lab is built on a concrete pad that once supported a wooden grain elevator, which burned down in the 1970s. Gulls circle and scream overhead, and trains rumble on sidings nearby, but the lab operates quietly. Harbor water is pumped through a complex pattern of red, blue, and yellow pipes into a series of 200-cubic-meter steel tanks. They look like small storage tanks at an oil refinery, but they’re only about one-fifth the size of the tanks on a Great Lakes ship. Tests can run for 24 hours, or up to five days. At the end, researchers take water quality measurements and count the test organisms remaining in the sample water. They also document the system’s mechanical functions and energy use.
This miniature replica of a shipboard ballast water system offers more control than researchers would have on a ship. “We don’t have to worry about the ship’s schedule, the cargo operations, the different water qualities in different ports,” TenEyck said. And experiments can be repeated – a prime requirement of scientific research.
“We need to use good science: we have to be able to adjust one variable and look at the outcome,” he said.
TenEyck and his colleagues have been on the forefront of this developing science for several years. The EPA is working on a new rule with numeric limits on how many live organisms a ship can discharge in a harbor. How strict does that rule need to be? “If we discharge one animal, will we get an invasion? If we discharge a million animals, will we get an invasion? We had to have a general idea about that,” TenEyck said.
They set up 22 tanks, filled them with harbor water, and released set numbers of spiny waterfleas in each. It’s an invasive creature which already lives in the Duluth Superior Harbor.
“Our results showed that between one and five waterfleas could colonize a tank and successfully reproduce,” said TenEyck. That’s not many, when a ship could be carrying hundreds of thousands! “But this was the best-case scenario for an invasion to occur,” TenEyck pointed out. “There were no predators.” He hopes to repeat the experiment with a different organism, perhaps a copepod, a tiny crustacean, in the months and years ahead.
Freshwater challenges
Nearly two dozen treatment systems have been approved for international use, but they don’t work well in fresh water. They may prevent new invasions from overseas, but there’s also the problem of species hitching rides on Great Lakes ships, from one port to another. Lake Superior has fewer invasive species than the other Great Lakes, but the Duluth-Superior port is extremely busy, with about 900 vessels visiting each year. Some of these ships come in without cargo and load up with taconite ore, coal, or grain. That means they discharge tremendous amounts of ballast water here in the western end of the St. Lawrence Seaway system.
The Lake Carriers’ Association, which represents U.S. flag Great Lakes vessels, is cooperating on invasive species research. Thomas Rayburn, Director of Environmental & Regulatory Affairs for the group, said shipping companies have spent tens of millions of dollars over the last 30 years to minimize their impact. They installed screens on intake pipes to capture and remove sediments, moved intakes from the vessel bottoms to the sides to reduce sediment uptake, and now they pump ballast water rather than relying on gravity, to create enough pressure to crush soft-bodied organisms.
“Since 2006, when both the U.S. and Canada required mid-ocean ballast exchange, we’ve moved more than 104 billion gallons of ballast water into the U.S. side of Lake Superior, in 18-thousand ships, without identifying any successful establishment of non-native species,” Rayburn said.
The fresh water in the Great Lakes poses numerous challenges to blocking the spread of invasive species. In saltwater, it’s easy to create chlorine, which is very effective at killing organisms. Water in Great Lakes ports also tends to be muddier than that in coastal ports, with tannins and suspended solids which make it darker, harder for UV light to penetrate. Also, UV doesn’t kill organisms instantly, and the lakers’ short voyages don’t necessarily provide enough time for it to work. Even the temperature range of Great Lakes water is a challenge. Treatment systems are designed to work above five degrees but Lake Superior is colder than that for much of the year.
Then there’s the matter of scale. Great Lakes vessels are very different from ocean-going ships, and they constitute a tiny minority in the global maritime world, with only 140 vessels in the entire fleet, compared to about sixty-thousand ocean-going ships. Given those numbers, and the relative ease of treating sea water, inventors working on technologies to treat ballast have concentrated on systems for the ocean-going fleet.
At the Duluth Seaway Port Authority, Director of Government and Environmental Affairs Jeff Stollenwerk has been watching the problem for a long time. “The Lake Superior Research Institute is key to meeting the Great Lakes challenge,” he said. “They specialize in freshwater solutions, and they have access to funding that can help move along the development of technologies that will work in the Seaway system.”
North of Duluth, Canada has moved a step ahead of the U.S. in ballast water treatment. Canada recently decided on a numeric standard for how many organisms can be released in ballast water. Stollenwerk expects the U.S. EPA to match the Canadian standard. “The next question is how they’ll implement the standard and apply it to Great Lakes carriers.” That job is assigned to the U.S. Coast Guard.
Vessel owners are nervous about the potential costs of the new rule. One study suggested it could cost $639 million to install treatment systems on the U.S. Great Lakes fleet, and $11 million yearly to operate and maintain them. They will take up space on the ship, which will reduce cargo space, and it could take as much as a year to install the systems, idling capacity on a busy fleet.
The EPA could release its rules in December, and then the Coast Guard has two years to determine how to implement them, including the murky question of how to apply them in the Great Lakes. If workable and cost-effective technologies are found by then, it will be a triumph of science and determination.
Most of these non-native creatures arrived in the Great Lakes in ballast water on ocean-going ships:
Sea lamprey, native to the Atlantic Ocean, were first found in the 1830s in Lakes Erie and Ontario. These eel-like parasites feed on large fish and were a major cause of the collapse of the Great Lakes commercial fishery in the 1940s and 1950s.
Smelt were actually stocked in Michigan’s inland lakes in the early 1900s to make sure Atlantic salmon, also being stocked, had something to eat. They have gone through dramatic population swings and now provide food for the recovering lake trout population.
Alewives are an Atlantic plant-eating fish, first seen in 1868 in Lakes Erie and Ontario. Their booming population contributed to the collapse of the lake trout population in the 1950s. In the 1960s they over-ate their prey, resulting in massive die-offs on public beaches. Natural resources managers responded by introducing Pacific salmon, which cut down on the alewife population and built a profitable recreational fishery. But alewives eat the young of native species such as yellow perch and lake trout and interfere with successful reproduction of those fishes.
Spiny waterfleas are native to northern Europe and were discovered in 1984 in several Great Lakes. They compete with native fish for food, and can reproduce many times faster than other fish.
Eurasion ruffe were first found in 1986 in the Duluth harbor. The population grew rapidly and at one point was thought to comprise 80 percent of the fish living in the western part of Lake Superior. Restrictions on walleye fishing have helped stabilize the population and ruffe do not appear to be causing major disruptions in other Great Lakes locations.
Zebra mussels are native to Eastern Europe and the Middle East; they were first observed in 1988 in several Great Lakes. With their free-floating larvae called veligers, they are rapid reproducers and quick spreaders. They clog water intakes for city drinking water, power plants, and irrigation systems. When they attach to boat surfaces and other equipment, they are carried from lake to lake. They are now found widely throughout the U.S.
Round gobies, native to Eastern Europe and the Middle East, were first detected in 1990 in the St. Clair River and several other Great Lakes locations. These aggressive feeders can eat the eggs and young of native fish, occupy key habitats, spawn multiple times each year, and survive in poor quality water. All these traits give them a competitive advantage.
VHS—Viral Hemorrhagic Septicemia—is a viral disease that has been spreading in the Great Lakes region since 1999. It has caused fish kills in various locations. It was found in Lake Superior in 2010 and so far has not caused major outbreaks of disease in Lake Superior.
Find out more at NOAA’ Great Lakes Aquatic Nonindigenous Species Information System.
