Unraveling the Impact of the hidden invader
In the vast and complex Great Lakes ecosystem, not all invaders arrive with a dramatic splash or grow to intimidating sizes. Some, like the Bloody Red Shrimp (∗Hemimysisanomala∗), are small, often overlooked, but nonetheless powerful agents of change. This tiny, elusive crustacean, named for its reddish hue when alive, has rapidly colonized the Great Lakes, highlighting how even subtle shifts at the base of the food web can have cascading, and still-unfolding, impacts on our freshwater seas.
From Eurasia to the Lakes: Who Are They and How Did They Arrive?
The Bloody Red Shrimp is native to the Ponto-Caspian Sea region of Eastern Europe and Western Asia, an area we’ve seen as a source for many other Great Lakes invaders, including the zebra mussels and round gobies. Like them, the Bloody Red Shrimp’s journey to North America was via ballast water discharged from transoceanic vessels.
First detected in Lake Ontario in 2006, its spread through the Great Lakes was remarkably swift. By 2007, it had already been found in Lakes Michigan, Huron, and Erie, and by 2008, it had reached Lake Superior. This rapid colonization underscores its adaptability and efficient dispersal mechanisms, including potentially hitchhiking on recreational boats and fishing gear.
A Nocturnal Nibbler: What Makes Them Successful?
The Bloody Red Shrimp’s success as an invader stems from a combination of factors:
- Versatile Feeding: They are omnivorous, consuming both phytoplankton (algae) and zooplankton (tiny animals), making them competitors with a wide range of native species for food resources. They can filter feed from the water column or graze directly on the lake bottom.
- Nocturnal Habits: They often spend their days hidden near the lake bottom, migrating into the water column to feed at night. This nocturnal behavior might help them evade visual predators during the day.
- Rapid Reproduction: They reproduce quickly, with females carrying developing young in a brood pouch, allowing for efficient population growth.
- Tolerance: They are remarkably tolerant of varying water quality, temperature, and salinity conditions, which aids their establishment in diverse parts of the Great Lakes and connected waterways.
- Lack of Native Predators: Native fish are not accustomed to preying on this species, especially given its relatively recent arrival and nocturnal habits, leading to fewer natural controls.
he Hidden Harm: What Impacts Are They Having?
The full extent of the Bloody Red Shrimp’s long-term impacts on the Great Lakes is still being actively researched, but early findings point to significant ecological consequences:
1. Food Web Disruption and Competition:
By consuming both phytoplankton and zooplankton, Bloody Red Shrimp directly compete with native zooplankton species (like Daphnia and native Mysis shrimp) and small, planktivorous fish for food. This can reduce food availability for native species that rely on these basal resources, potentially impacting the growth and survival of larval and juvenile fish.
Research by Dr. David Jude, Professor Emeritus at the University of Michigan, who has extensively studied Great Lakes food webs and invasive species, expressed concerns early on: “Any time you have a new invasive species consuming significant amounts of plankton, it’s going to affect the food web. We’re concerned about what this means for the entire Great Lakes food web and for fish that rely on these resources.”
2. Altered Nutrient Cycling:
By consuming large quantities of algae, the Bloody Red Shrimp can potentially shift how nutrients move through the ecosystem. While they might contribute to water clarity by reducing suspended algae, this comes at the cost of redirecting energy away from native grazers that play vital roles in the food web.
3. Impact on Native Mysis Shrimp:
There’s concern about competition with the native Great Lakes Mysis shrimp (Mysis diluviana), a cold-water species that is a crucial food source for deepwater native fish like lake trout and sculpins. While their niches don’t perfectly overlap, increased competition could indirectly impact these important native predators.
4. Nuisance for Anglers:
Similar to the Spiny Waterflea, Bloody Red Shrimp can accumulate in thick masses on fishing lines, downrigger cables, and nets, creating a slimy nuisance for anglers and potentially aiding in their overland transport to new water bodies.
Science on the Small Scale: Who is Studying and Fighting Them?
Scientists are diligently working to understand the Bloody Red Shrimp’s biology, spread, and ecosystem impacts to inform management strategies.
- NOAA Great Lakes Environmental Research Laboratory (GLERL): Researchers at GLERL actively monitor the distribution and abundance of Bloody Red Shrimp and study their feeding behaviors and interactions with native species.
- U.S. Geological Survey (USGS) Great Lakes Science Center: USGS scientists are involved in long-term monitoring programs that track changes in zooplankton communities and fish diets, helping to assess the Bloody Red Shrimp’s ecological footprint.
- Academic Researchers: Universities throughout the Great Lakes region, including those involved with Sea Grant programs, are conducting studies on their reproductive strategies, physiological tolerances, and detailed dietary analyses to pinpoint their precise role and impact within the food web. This includes efforts to understand how climate change might influence their spread and impact.
- State and Provincial Natural Resource Agencies: These agencies are involved in monitoring newly infested areas and communicating with the public about preventing further spread through “Clean, Drain, Dry” practices for recreational gear.
The Bloody Red Shrimp is a powerful reminder that not all invasive threats are immediately obvious. Its ongoing spread and subtle, yet pervasive, impacts reinforce the need for continuous research, vigilant monitoring, and public awareness to protect the intricate balance of the Great Lakes – our deep world – from even its smallest invaders.
