Introduction

Sharks are the Batman of the sea. They act as protectors towards ecosystems by keeping ecosystem inhabitants from destroying each other, and are greatly feared and misunderstood. Sadly, many sharks are having a difficult time surviving as of late in no small part due to the effects of climate change. In this blog, I shall look at some of the effects of climate change on sharks, but more specifically sharks found in the Great Coral Reef.

One of the few pictures I have taken of live sharks

So, what does that mean for the oceans and those creatures that live within? One less scary creature, right? A victory for smaller, weaker fish everywhere? Well, it's not that simple for the poor, defenseless, tasty fish. Believe it or not, sharks actually have quite an impact on ecosystems. Sharks will eat whatever organism is most abundant to them at the time. But, as a wise man once said, "With great power comes great responsibility." With their ability to consume whatever prey is most abundant to them, they are also able to make sure that species of prey does not become too numerous for the ecosystem to maintain. Because of their massive effects on the marine ecosystems, sharks are what are known as keystone predators.

Take the tiger shark, which is found in the Great Barrier Reef, as an example.1 One of the species of prey that is on the tiger shark's menu is the dugong. The diet of a dugong consists mainly of sea grass. When dugongs are capable, they will eat the entire plant, disrupting any of the organisms that use the seagrass as habitat. However with the increased presence of tiger sharks, dugongs avoid some of the areas where seagrass flourishes. Thanks to the these sharks, species that rely on the seagrass are able to thrive better. For an interesting and simplified food web diagram, click here.

So, hopefully with this background on keystone predation you are able to see why it is that sharks are important to a community. Without the sharks hunting the most abundant of prey, the former prey would grow in abundance and destroy other important parts of the community in order to get there... Heartless dugongs...With fewer sharks chowing down on these ambitious (and not to mention delicious) creatures, one species of marine organism may get the upper hand and muscle the other species out of the running.

To show you a summary of what the reduction of one species of shark may cause, I leave you this figure I made:

Information on Grey Nurse Shark food chain found here