Does climate change create damsels in distress? – Guestblog by Tanika Shalders

TanikaThe latest guestblog on Critter Research is by Tanika Shalders. Tanika is a Technical Officer for the Marine Science Program at the Department of Biodiversity, Conservation, and Attractions in Australia. Her current work entails diving on some of the most amazing reefs in Australia and video analyses of surveys in Australian marine parks. In this guestblog she describes her recently published research on the effects of climate change on damselfishes.

It is currently spring in Australia, a lovely time to be outdoors. Nice temperatures (average maximum of 22), plants in full bloom, perfect picnic weather… just find a nice patch of grass, a cold beverage and some snacks.

Heatwave dogSummer is just around the corner and here in Perth it can get very warm, with an average maximum of 31 degrees (although temperatures up to 40 degrees are not unheard of). Unfortunately, picnics are not as pleasant this time of year. It’s hard to find shade, you’ll likely get sunburnt and your drinks will get warm.

What do you do when the temperatures become unbearable? Head to the coast to cool off in the ocean? Hide in the air-conditioning? Increase your ice-cream consumption? We try to make ourselves as comfortable as possible, moving to a cooler environment where we have everything we need – food, water and shelter.

With this in mind, it is no surprise to learn that other animals are doing exactly the same thing when ocean temperatures rise. Over the past 5 decades ocean temperatures have been increasing due to climate change. There has also been an increase in heat waves.

Heatwave map

Heat waves are becoming increasingly common across the world

Many people connect these events to coral reefs, so it may come to some surprise that the ocean in temperate (southern/cool-water) Australia is warming at least twice as fast than the global average.

In 2011, the south-west of Australia experienced a heat wave. The heat wave lasted more than 10 weeks and temperatures increased up to 5 degrees above normal. This event caused massive changes to the marine environment of south-west Australia. One of the most significant documented impacts was the loss of kelp along the south-west coast. In the warmest area (north) kelp disappeared completely. Changes have also been seen in other organisms such as fish and crustaceans.


Ecklonia radiata, the kelp species which was greatly affected by the 2011 heatwave. Source:

After the heat wave, we decided to investigate if fish had also been impacted by the extreme temperatures. We chose to look at territorial damselfish since they are ‘site attached’. Much like the Hobbits of Middle Earth, they don’t like to leave home. These damselfish farm and protect algae which they use for food and reproduction. This trait makes them a good species to indicate of change as it is unlikely individual fish will move from their home to a new location. However, juvenile fish (recruits) may set up camp in new locations.

Using diver operated stereo-video (DOV), we investigated where these damselfish lived before and after the 2011 heat wave, and how many there were.


The damselfishes in this study. A) Parma occidentalis; B) Pomacentrus milleri; C) Parma mccullochi; D) Parma victoriae. Sources: Fishbase and Reef Life Survey

The main result was that the two (northern) warm-water damselfish became more common in the (southern) cooler waters. The two cooler-water damselfish showed less change.

We also saw a change in algae habitat. The kelp that dominated in 2006 had often been replaced by smaller forms of algae by 2015. This included the turfing algae such as those farmed by the damselfish.

So what does this mean?

These results show that both fish and their habitat are changing due to climate change. When warm water fish move to cooler water, they might push out the local cool water fish on their way south.

This process of warm water fish moving into cooler environments is known to the science world as tropicalisation – previously explained in a guest blog by the wonderful Dr Joseph DiBattista so I won’t go into detail here. Instead I will delve into one of the flow-on effects of tropicalisation: increased competition.


Tanika collecting Diver Operated stereo-Video (DOV) footage. Photo: Will Robbins, DBCA

Competition happens everywhere in the natural world. Plants compete for sunlight, lions compete for antelopes, and high school boys compete for the same girl. Usually competition occurs over food, water, shelter, or booty. Any additional players entering such a highly competitive environment can have devastating effects.

The movement of warm water fish into cooler waters could increase competition for the local fish populations. Since these damsels eat the same food and are very territorial, this means they not only have to compete with each other, but also with new damsel species. It’s hard enough to compete with your siblings for the last helping of dinner – imagine having to compete with your whole street!

Often this means that the local species will have retreat from an area once the invading species starts competing with them for food. Fortunately in this case, it looks like the change in habitat meant there was more food for the damselfish. It is likely that this helped to support a larger number of damselfish by reducing competition.

Most people are starting to become aware that climate change is an issue, sadly it’s a much bigger problem than most believe. Scientists are just being to scratch the surface of understanding the full reach of its impacts. If you would like to learn more about climate change and what you can do to help, please visit this site to find out more.


Tanika Shalders

Technical Officer, Marine Science Program

Department of Biodiversity, Conservation and Attractions

Twitter: @TanikaCShalders

Instagram: tanikacs

Research Gate: Tanika Shalders


Climate change might increase competition in the oceans. Photo Will Robbins, DBCA

Why the ocean matters and why we should talk more about how awesome it is…

This week I attended the CommOcean 2016 conference in Belgium. CommOcean was all about marine science communication and what the best ways are for marine scientists to interact with the general public. Science communication is about more than just reaching non-scientists, but also about making an impact and transforming how people perceive the ocean, it’s about making a positive change. But why would anyone really care about the ocean, or even more, change their day-to-day behaviour for it? A question particularly relevant if you live far away from the sea or don’t have a taste for fish.


The CommOcean2016 crowd in front of the beautiful conference venue in Bruges

The thing is, the ocean matters big time, for everyone, everywhere. On a global scale, the ocean produces more than 50% of the oxygen we breathe (more than trees!). If breathing isn’t your thing, the ocean also provides other trivial things such as food, cures to certain cancers and other diseases, a way to transport most goods around the globe (90% of international trade), and so much more. Current human impacts such as climate change can and will have effects on everyone, even those living furthest away from the sea.

For the people fortunate enough to live close to the coast, the ocean is even more important. Over 1 billion people depend on the sea as their main source of protein, which explains why overfishing is such a big issue. Besides food, the sea also provides a way to make a living as fishermen, through trade, industry, or tourism (muck diving being only one example). For people living on low islands, rising sea levels are a very real and very large threat. Entire countries might sink below the ocean and will have to move elsewhere. Countries like Tuvalu and Kiribati are already negotiating with Australia about possibilities to move their entire population there. Popular holiday destination Maldives has even gone further and is already buying up land in other countries to prepare for relocating its people.

Communicating ocean science is often challenging when people aren’t faced with the ocean in a way the Maldivians or other islanders are. Not being able to see what is below the waves might be the biggest challenge to get people to care about our oceans. It is hard to comprehend  just how amazing life in the sea can be without diving in it, or without the help of talented filmmakers and photographers to show us.

The fact that many scientists are still perceived to live in their “ivory tower of knowledge”, without interacting with people does not help either. The issues facing the oceans are often more complicated than those on land and often seem overwhelming. If the only news people hear about the oceans is bad news, they won’t be keen to listen to the yet another doomsday talk. Most marine scientists are not trained to be communicators and are often too worried about oversimplifying their message, resulting in nuanced, scientifically correct communication that is unfortunately understand by nobody else but scientists. Lastly, in a world where Twitter, Facebook, etc. are increasingly the main source of information for people, it is hard to get attention with a science message. After all, who wants to read about weird fish, if you could be reading about what a Kardashian had for breakfast or that your favourite soccer player went wild on a party last night?


Rita Steyn explaining the ins and outs of Twitter

So what is the solution? How do you get the message across that the oceans matter? I’m in no way an expert, but luckily there were experts around at CommOcean. The first step is to adapt you message to the people you are talking to, don’t go wild on the crazy science talk, have a clear message. (in case you forgot: “Oceans are awesome! Get the news out there!“). Ideally try to interact directly with the people to whom your research is important, stop talking over people’s heads and listen to what they care about. Using social media is a good thing, but do it right and don’t get stuck on just one method. Not everyone uses Twitter or visits websites about science, many people don’t have smartphones and might prefer written media, etc. Don’t forget that humans are visual animals, presenting your message in a more attractive way than dry text will get more attention.


Lastly, maybe most importantly, don’t forget to give the good news. There might be a load of bad news out there, but the ocean is still a beautiful place, something I feel everyone should know about too. Telling people about the beauty that can be found and offering practical tips on how to do something about protecting it can go a long way.

In the long run, what we really need is ocean science to become ingrained in all levels of education. As one of the most important ecosystems in our world, the ocean deserves more attention. After all, as long as people are not aware of the importance of the ocean (and the issues facing it), they cannot change their attitudes about the ocean and they will definitely not change their behaviour to preserve it.


PS: In the spirit of using different communication channels, crittersresearch is now also live on twitter as @DeBrauwerM.

PS: All photos sourced from the CommOcean2016 Facebook page


Climate vagrants: Guestblog by Joey DiBattista

I have been writing blog posts about my research for over a year now, talking about how interesting my research is. But there is a lot of interesting marine research happening besides mine. So I will now try to get friends and colleagues to write guestblogs about their research, giving you the chance to have an even better insight in what happens in the world of marine biology.

The person to kick off this new section of the blog is Dr. Joseph DiBattista, a geneticist at Curtin University. If you have been following the Critters Research Instagram account, you might have noticed I was up in Shark Bay last week. I was there to help Joey with his research on “vagrants” in the waters of Western Australia. His blog explains more about these vagrants and what they have to do with climate change…

The age of climate change is upon us. This reality can no longer be denied given that the scientific evidence is overwhelming. One of the areas hardest hit by this human-influenced phenomena is our oceans, and the result for our precious coral reefs is often bleaching, bleaching, and more bleaching. Just ask those that study our beloved Great Barrier Reef, a UNSECO world heritage site where only 7% of its corals escaped nature’s wrath in early 2016.


Bleached coral at the Great Barrier Reef. Photo: XL Catlin Seaview Survey

At the same time that corals were suffering in Australia, so were mangrove forests that border the Cape York Peninsula in the Gulf of Carpentaria, which experienced a die-off like scientists worldwide have never seen before (i.e. 7,000 hectares of mangroves left dead or dying…). The recent temperature fluctuations are attributed to this year’s particularly strong El Niño–Southern Oscillation (ENSO), and have now caused bleaching at Indian Ocean coral reefs in the Maldives and at Christmas Island for example, and are imminently predicted for tropical sites further north in the Pacific Ocean (e.g. Okinawa).

It may seem like temperate ecosystems are protected from these warming effects, but no more are we feeling the heat than in the coastal waters off of South-Western Australia (WA). Near the end of the summer of 2011 we suffered through what was aptly coined a “marine heat wave”. Sea surface temperatures from Ningaloo reef to the southern tip of the continent at Cape Leeuwin, a distance of more than 1,500 km, crept up to over 5° C above the seasonal average. This affront was both broad and sustained, extending out more than 200 km from shore and lasting more than 10 weeks. The heat wave killed off more than 100 km of economically important kelp forests (often teeming with their own rich and unique fauna), that have to this day not recovered, but instead may slowly be replaced by corals, a process known in the science world as tropicalisation.

Chaetodon lunula

Tropical species like this Racoon Butterflyfish (Chaetodon lunula) are increasingly found in Western Australia’s temperate waters. Source:

This heat wave in 2011 overlays on top of an already warming trend in WA, which itself has been flagged as a global climate change hotspot. Climate change not only affects the kelps and the corals, but appears to be resulting in tropical and subtropical fish species rapidly moving towards the poles. Indeed, in addition to WA, tropicalisation has caused important changes to temperate ecosystems by introducing tropical fishes to sites in western Japan and off the coast of New South Wales, all themselves bathed in warm water currents that act as vehicles for this fresh “flow” of fish larvae.


Joey filtering water in Shark Bay to extract eDNA

Normally the water temperatures cool over winter months and these juvenile tropical “vagrants” die off, never to reproduce themselves (…sniff, sniff, shed a tear…), but not for some species. In rare cases, enough individuals survived and have now taken up permanent residence in their new southerly (or northerly for Japan!) home. I have a keen interest in these survivors along the coast of WA, where I have started to use next generation sequencing technology to track the movement and diet of these vagrants. This technology is capable of simultaneously sequencing millions of copies of DNA from complex samples, at a not so nominal cost of course. This innovative work is only possible because of a close collaboration with the Trace and Environmental DNA (TrEnD) laboratory at Curtin University in Western Australia. Particularly Professor Michael Bunce, who has extensive experience in isolating DNA from a variety of substrates including bulk bone, faecal material, and, more recently, samples sourced from the marine sector such as filtered water and fish stomach contents. This project remains in its infancy, but with the Department of Fisheries WA supplementing samples and the TrEnD Lab supporting my experimental work, I am confident that we will soon know exactly where these vagrants are coming from and what they are doing once they get here.

Dr. Joseph DiBattista

Early Career Postdoctoral Research Fellow

Department of Environment and Agriculture

Curtin University


Note: For those keen recreational fisherman or scuba divers in WA, there is a website dedicated to tropical fish species that seem “out of place” in their new temperate environment (click here for site). I encourage anyone that spots vagrant fish to take photos and register their important find on this regularly updated website.