Antarctic Marine Ecosystem: Explaining Key Concepts Lesson at a glance Students will play a simple game that illustrates important concepts related to Antarctic marine biology such as biodiversity, climate change, overfishing effects, and marine keystone species. Background In order to understand “who eats whom” in the Antarctic marine food chains, it is important to keep in mind some key concepts: -­‐ The animals and plants that live in the Antarctic have to adapt to low temperatures, long periods of darkness, and the seasonal sea ice. -­‐ Algae (phytoplankton) are at the base of the Antarctic food web, known as producers. They are consumed by consumers such as the Antarctic krill, Euphausia superba (a small shrimp-­‐like crustacean), and other herbivorous zooplankton (e.g. copepods). In turn, these are consumed by a wide range of species of fish, squid, and top predators such as whales, seals, penguins and albatrosses. -­‐ The energy transference from phytoplankton to top predators can be very quick. For example, one of the simplest Antarctic food chains is phytoplankton eaten by Antarctic krill and this species is then eaten by a top predator, the baleen whales. -­‐ Antarctic krill is considered a keystone species (a species that plays a critical role in maintaining the structure of an ecosystem) in the Antarctic marine ecosystem. If Antarctic krill would be removed from the Antarctic marine ecosystem, the marine ecosystem would “collapse” and would experience a dramatic shift in its structure. Figure 1 demonstrates the complicated food chain and the role Krill play. -­‐ Antarctic exploitation of ocean resources (fisheries and whales/seals hunting) started Figure 1. An Antarctic marine food web and the connections between species and krill. in the19th century and was focused mostly on seals and penguins, and in the 20th century the focus shifted to whales and fish fisheries, pushing some species close to extinction. Today, there is no whale/seal/penguin hunting and Antarctic fisheries (mostly focused on fish and Antarctic krill) are well managed. -­‐ Climate change is known to have effects on the Antarctic marine ecosystem. For example, the increase of temperatures may have negative effects on the abundance, distribution and reproductive capacity of various species (such as the Antarctic krill, fish and benthic species). Time Preparation: 5 minutes Class time: 30 minutes Materials (per group of students) Jenga game Activity directions 1. Build the jenga tower to represent the Antarctic food web. 2. Each student should remove a single jenga piece with only 1 finger and put it on the top of the pile. Each jenga piece represents a species removed from the Antarctic food web (either by overfishing or climate change). Discussion In the beginning of the game, imagine the untouched jenga tower representing the Antarctic food web in equilibrium (the only activity being different species eating others). The first concept to understand here is that although the Antarctic food web can be relatively simple, it can also be complex (i.e. various species eating many other species). As each jenga piece is removed (remember to keep on putting them back on top), gaps within the tower become obvious and the tower becomes more “fragile”. This illustrates the concept that removing species from the marine ecosystem (either through overfishing or climate change) is not good. At a given stage, one more piece of jenga removed will make the tower collapse. That piece represents the Antarctic krill, the keystone species. Without it all the Antarctic food web would collapse. Figure 2. Example of a jenga game. Extensions/adaptations Adjust the complexity of the jenga game according to the age of your students. For the younger pupils, each student could receive a jenga piece and draw their favourite Antarctic organism on it while the general concepts of food webs and the relevance of the Antarctic krill is explained. For older students (University level), consider giving a lecture on comparing the Antarctic food webs from different parts of the Antarctic (Scotia Sea versus Ross Sea). Instead of the jenga game also consider using a “pick up sticks” game. In this case, initially all sticks are together and really demonstrates how complex the Antarctic food web can be (any stick touching other could represent eating or being eaten by another species). Here, the students play the role of “fisheries” or “climate change” as they remove the species from the pack... until there is the danger of no more species left.