In the past few decades, the Great Lakes have quickly become a major hot spot for invasive aquatic species. Of these invaders, the spiny water flea has proven itself to be quite destructive. Despite its tiny size, this creature has shown ample evidence that it can cause colossal damage to its habitat.

Professor Norman D. Yan and his colleagues at York University have measured and studied the populations of zooplankton in the Great lakes in order to better understand the extent of damage that the spiny water flea is causing. The team set out to visit Harp Lake, located in Lake Ontario, to collect samples of zooplankton. They found that the zooplankton community has been drastically reduced and assign the blame to the spiny water flea.  Yan and his colleagues argue that if left unchecked, this invasive crustacean will slowly begin to unravel the fragile food web of the lakes.

Canadian Journal of Fisheries & Aquatic Sciences 58.12 (2001): 2341-2350.

Biol. Invasions 12, 1045-1051 (2010)

The probability that a native predator will incorporate an invasive species into its diet depends upon the potential benefits versus costs of ingestion.  However, when said invader possesses chemical defenses different from native biota – specifically, the toxicity of the invasive cane toad (Bufo marinus) in Australia – mortality due to toxin ingestion should change predation preferences.  But what happens to the diets of predators that are able to consume the toads without dying?

John Llewelyn et al. of the University of Sydney conducted field surveys in northern Queensland to determine whether a toxin-resistant Australian snake would prey upon B. marinus.  Captured snakes were palpated to induce regurgitation, and the contents of their upper digestive tracts were examined. The study showed that keelbacks (Tropidonophis mairii) feed primarily on native frogs rather than toads.  The authors believe this occurs because consumption of toads produces significant sublethal effects and little nutritional benefit.  Thus, B. marinus can thrive even amongst predators capable of overcoming its potent chemical defenses.

Mar Ecol Prog Ser. Vol. 401: 291–294, 2010.

Since its introduction into Florida nearly a decade ago, Pterois volitans, the Lionfish, began its invasion of the coral reefs in the West Atlantic, especially in the Bahamas. In its non-native habitat, the Lionfish has become much more productive and successful than in its native home, because there are limited predators once it reaches adulthood. With the increase in Lionfish, there is a decrease in native fish recruitment.

Andrew B. Barbour,of the University of Florida, and his colleagues decided to answer the question of this invasive phenomenon. Do the Lionfish have an affect on the decreased recruitment? They  hypothesized that the Lionfish have been living in the mangroves that the native species use to reproduce. To test this, researchers checked the mangroves and examined stomach contents of the lionfish. In the contents, the scientists found remnants of species that are found within the Mangrove. With this analysis, the scientists concluded that the Lionfish had been preying on fish in the mangroves, most of which are juvenile. This has lead to increased juvenile mortality and therefore, the researchers believe, has lead to decreased recruitment. Despite their finding, the researchers hope for more in depth studies to be held.