News » National Marine Week Ocean Hero - Dr Kerry Ann van der Walt

Our Ocean Hero for National Marine Week 2020
Dr Kerry-Ann van der Walt

In celebration of National Marine Week, the Marine Stewardship Council (MSC) ran an Ocean Health blog, with QA-style guest content to put a spotlight on the main threats our oceans are facing – and on the organisations that are doing something about it. NRF-SAIAB scientists contributed to this blog, sharing information about their marine research projects on climate change and how they are addressing this issue.

This is what our Ocean Hero and Postdoctoral Researcher, Dr Kerry-Ann van der Walt had to say about Climate Change:

Dr Kerry-Ann van der Walt – Postdoctoral Researcher at SAIAB
PhD in Ichthyology and Fisheries Science from Rhodes University

  1. 1. Provide us with a context of our marine resources in South Africa.

Climate change is the change in climate over long time periods (decades to millennia) that can negatively affect animals and the health of ecosystems (Figure1). Causes of climate change include rising mean temperatures; increases in strength of wind and ocean currents; changes in rainfall patterns (flooding and drought); increases in climate extreme events (heatwaves and cold spells), rising sea levels, and ocean acidification (Figure 1). In South Africa, effects of climate change have already been recorded, especially within our water environments, in the form of rising mean sea temperatures, flooding events, and droughts. In the future, these effects of climate change within the country’s water environments are expected to increase, resulting in more intense and frequent extreme climate events and climate variability.

Figure 1. Poster explaining the effects of climate change.
Designed by Dr. Kerry-Ann van der Walt for National Science Week (2016),
sourced from the NRF South African Institute for Aquatic Biodiversity (SAIAB).

  1. 2. Explain to us the impacts of climate change on our oceans and marine life.

One of the major effects of climate change in South Africa’s surrounding oceans are changes in temperature. Rising mean ocean temperatures and increases in temperature variability events in the form of marine heatwaves and coastal upwelling (movement of deep cold water to the ocean’s surface by wind motion) will negatively impact marine organism’s growth and development, distribution patterns, and reproduction output. Many marine organisms are ectotherms whereby their body temperature is controlled by the temperature of the water around them. Rising mean and extreme ocean temperatures can then directly affect the metabolism, life cycle, and behavior of marine organisms. Also, as ocean temperatures rise and become more variable, the location of ideal water temperatures may shift for many marine organisms to deeper waters or locations of cooler water temperatures which may not necessarily be preferable. Furthermore, temperature serves as a cue for reproduction for many marine organisms (e.g. fish), and so with increased temperature changes along South Africa’s coastline, marine organisms breeding schedules could be changed which may threaten population survival.

Another effect of climate change that is a growing concern in this region is ocean acidification. Ocean acidification is a result of increased carbon dioxide emissions in the air mixing with sea water which lowers pH levels and makes oceans more acidic over time. This change in seawater acidity can negatively impact marine organisms in various ways. In marine fishes, growth and development may be slowed down, especially in the early life stages, influencing survival and population growth. In marine mussels, oysters, and corals, highly acidic water can dissolve their shells and skeletons (made up of calcium carbonate) which will lower their survival and ultimately result in a loss of food and shelter for other larger marine organisms like fishes.

  1. 3. Provide an overview of the projects led by SAIAB to address, study or mitigate the impacts of climate change on the marine ecosystem.

At the South African Institute for Aquatic Biodiversity (SAIAB), we have numerous projects led by our scientists in collaboration with other Institutions that focus on assessing the impacts of climate change on marine biodiversity. Recent projects include:

  • Evaluating the tolerance of common coastal fishes and invertebrates to extreme temperatures (Rhodes University).
  • The effects of exploitation on the resilience of an important linefish species to climate change (Rhodes University, University of Southampton, Memorial University of Newfoundland).
  • Assessing the vulnerability of estuarine biota to climate change through the response of organisms changes in temperature, flood regime, and habitat loss (Department of Agriculture, Forestry and Fisheries, Nelson Mandela University, CSIR, Oceanographic Research Institute, Walter Sisulu University).
  • Coastal ocean acidification in Algoa Bay and its impacts on the physiology and behavior of a common coastal fish (Rhodes University, Gothenburg University).
  • The role of mangrove habitat complexity in shaping the thermal physiology of invertebrate and fish larvae (Rhodes University; Hong Kong University).
  1. 4. List some simple ways in which consumers/ South Africans can help minimise or mitigate the impacts of climate change on the coastal and marine environment.

 South African consumers can help minimize the impacts of climate change on the coastal and marine environment by:

  • Cutting down on carbon usage: By lowering your energy or electricity usage, you are reducing carbon emissions which may mix with seawater resulting in it being more acidic. Ways to lower your electricity usage include drying your laundry on a clothesline instead of in a tumble dryer, using your dishwasher only when it is full, and unplugging electronics from the wall socket when not in use. You can further cut carbon emission by replacing light bulbs and older appliances with newer, more efficient energy saving models. Instead of using your vehicle daily, try reduce carbon emissions by walking, biking, taking the bus, or carpooling to work, school or the grocery store. Overall, consume less. The less food or products you buy, the less fossil fuel is being burnt to extract, produce and ship products around the World.
  • Switching to green power: Not all energy comes from burning fossil fuels. Clean, unlimited energy can come from the sun and wind. So as consumers, switching to plant-derived plastics, biodiesel and wind-power can lower carbon emissions.
  • Planting trees: Planting native trees on your property can help lower carbon emissions. Getting involved in a community forest restoration, dune or coastal revegetation program in your area will also make a great difference in your region.
  • Reducing, reusing, and recycling: Garbage, especially plastic, is a great risk to marine animals. Marine animals such as turtles, seabirds and seals often mistake floating plastic goods as food or become tangled in it. To prevent harming any marine animals and polluting the oceans with this toxic material, buy only the food you need, without any packaging whenever possible, and use reusable or brown paper bags. Reuse plastic bottles and if possible replace plastic bottles with glass bottles. Recycle plastic and glass containers that cannot be reused in recycle bins in your area if possible. All this will reduce the amount of waste going to landfills and carbon emissions that result when new items are made. 
  • Being water wise: All water resources eventually leads to the ocean, and in order to keep it healthy, consumers need to reduce the amount of chemicals used. For instance, reduce the amount of fertilizer used in your garden as extra nutrients from the fertilizer can affect the oceans ecosystem and can cause harmful algae blooms. When purchasing fruits and vegetables, target those that have been grown without pesticides, as pesticides contain toxins that can harm marine life. 
  1. 5. What does ocean sustainability/ ocean health mean to you?

The oceans, and in particular coastal areas, are a very important part of the Earths ecosystem as they serve as a home for million marine species that provide important ecosystem services. Using our oceans sustainably is therefore so important to me as we need to ensure that these millions of species and the services they provide remain, in order to ensure our survival. With the impacts of climate change increasing, the risk of these millions of species becoming fewer and fewer is high, so protecting our oceans and marine life where possible is a necessity. Managing our oceans better requires action from all of us.

  1. 6. In your opinion, and within the context of climate change, what role can/is sustainable fishing (and seafood) playing in mitigating the impacts on our oceans?

Climate change is expected to make sustainable fishing even more urgent and crucial. Due to the impacts of climate change, the supply of products from both marine and coastal fisheries and aquaculture is unpredictable in the near future and has raised many questions as to how we can look after this resource sustainably. By being aware of the impacts of climate change (i.e. increases in ocean temperature; ocean acidification) that will change the abundance and distribution of important fisheries and aquaculture production is a great starting point and by researching further how we can then adapt or change to more sustainable fishing practices will help us prepare for a worst case scenario. 

  1. 7. As an Ocean Hero this Marine Month, please provide us with a quote or educational tip in celebration of our oceans and ocean heritage.

Aristotle quoted, “What is common to many is least taken care of, for all men have greater regard for what is their own than what they possess in common with others”. For us to protect our oceans, use them sustainably, and mitigate the effects of climate change, we need to stop taking this important resource for granted and start working together to protect it and the services it provides, because at the end of the day the ocean is a thread that connects everything together!