The West Coast rock lobster’s natural ability to adapt to varying environmental conditions may be its saving grace when it comes to climate change. This is according to research conducted by aquaculture scientist Dr Jarred Lee Knapp of Stellenbosch University.
His research shows that these crustaceans have a natural ability to physiologically adapt to rising sea temperatures and increasingly acidic seawater which are predicted to be part and parcel of ongoing greenhouse gas emissions.
Most of his research was conducted at the Department of Agriculture, Forestry and Fisheries (DAFF) Marine Research Aquarium in Sea Point, Cape Town.
The West Coast rock lobster (Jasus lalandii) is a sought-after delicacy that is wild caught according to strict permit regulations. This crustacean, which is a species of spiny lobster, lives in the cold waters of the Benguela Current System, off the West Coast of South Africa and Namibia.
It’s not an easy space to live in, as environmental conditions in this oceanic region often change. An example is upwelling events, during which nutrient-rich water is driven towards the surface. This leads to phytoplankton blooms and even subsequent extreme red tide events. When the phytoplankton dies and decomposes, low oxygen levels can be found in some areas. These events can cause the surrounding seawaters pH level to reach extremely low values, from a more basic or alkaline seawater pH of 8.0 to a more acidic pH of 6.6.
“These events have been forecast to become more frequent and severe due to increased ocean acidification that is caused by the trapping of increased amounts of carbon dioxide in seawater,” explains Dr Knapp.
A global pH for seawater of about 7.3 is expected by the year 2300. Dr Knapp says that due to the already low pH levels in the Benguela Current system, extended periods of high acidity could occur here in the not too distant future.
He started his research because lobster is a valuable resource to the South Africa fishing industry. Also, very little was known about how well spiny lobster will cope with the predicted environmental changes. He set out to determine how the rock lobster physiologically responds in the short term to changes in seawater pH, and the long term effects that such changes have on growth and on the respiratory protein, haemocyanin. Subsequently, he assessed the ability of the lobster to respond to long term exposure to decreased seawater pH at two temperatures, and how it affects lobsters’ ability to defend itself against disease.
Dr Knapp found that the West Coast rock lobster is able to quickly respond to changes in its environment. These changes can be maintained for a sustained period. They are also reversible, should circumstances become more favourable again. West Coast rock lobster is able to adjust its respiratory capacity at a molecular level. Also, long term exposure to decreased pH did not have an impact on its immune system’s ability to fight an introduced bacterium.
Dr Knapp however warns: “The availability and quality of their food could influence the ability of the West Coast rock lobster to deal with environmental stressors.”
Rock lobster typically feed on a mixed diet consisting of, among others, mussels and sea urchins. He also notes that in reality, the lobster is typically not only exposed to one or two stressors at a time, but rather a multitude of environmental factors. These, in combination, could have an influence the lobster ability to respond to environmental change.
In terms of the value of his findings, Dr Knapp says: “It provides important initial information to help government fisheries scientists predict future management of the resource and the work offers a strong basis from which future studies can be developed.”
Dr Knapp was awarded a PhD (Agric) in Aquaculture on 10 December from Stellenbosch University. Some of his research findings have appeared in the scientific journal Biochemical and Biophysical Research Communications, while other results will be published next year in the Journal of Experimental Marine Biology and Ecology.
* This article is based on a press release written for the Faculty of AgriSciences at Stellenbosch University.