Measuring behavior of coral larvae in response to antifouling coatings

What effect do ship hull coatings have on coral viability and restoration? And how can non-toxic alternatives effect mobility behavior in coral larvae?

Published on

Thu 12 Jan. 2023

Measuring behavior of coral larvae in response to antifouling coatings

The pressure on tropical coral reefs and coastal areas due to climate change and human activity remains ever-increasing. Heat stress is a well-known example as one of these factors, but also antifouling agents from ships (mostly from ship groundings) can lead to heavy contamination of coral reefs.

Toxic marine coatings

Antifoulings, usually applied in by painting, are specialized coatings on hulls of ships (or other marine man-made structures) to slow down or even prevent the growth of (sub)aquatic organisms. This is aimed at performance and cost management of said ship. Historically, antifouling paints have been known to contain a considerable amount of toxic compounds, such as tributyltin (banned) and copper, greatly affecting marine life. Paint particles eaten by the smallest of organisms, such as (zoo)plankton, can trickle down into the food chain and cause bioaccumulation in larger species such as fish.

ship paint toxicity marine life

The effect of antifoulings on coral reefs

In coral reefs, antifouling agents have been found to inhibit coral larval settlement and survival, which are crucial for reef recovery. Non-toxic antifouling alternatives may decrease toxicity, which indeed seems to be the case for coral larvae [1]. However, Lisa Röpke from the Leibniz Centre for Tropical Marine Research in Bremen (Germany), flags attention for behavioral responses in coral larvae such as mobility/swimming activity during exposure to these potentially non-toxic agents.

If mobility of coral larvae is compromised in any way, other functional responses such as habitat selection, feeding, predator avoidance, competition and reproduction are also at risk, all-in-all reducing fitness and survival of coral larvae. This is why measuring behavior is crucial and the development of innovative tools, that allow for automatic and quantitative measurements of behavior, may complement ecotoxicological studies significantly.

Acropora millepora and EthoVision XT

Röpke’s most recent study focusses on the behavior of Acropora millepora coral larvae [2]. Per exposure group, 32 larvae were recorded for 25 min in a dark box while tracking analysis was performed with Noldus’ EthoVision XT. Three recently-developed, and potentially non-toxic, antifouling coatings were tested: (1) antiadhesive (silicon-based sol-gel coatings which exhibit antiadhesive surface properties), (2) cerium dioxide (CeO2-x) nanoparticle and (3) encapsulated biocide dichlorooctylisothiazolinone (DCOIT).








RESOURCES: Read more about EthoVision XT

Find out how EthoVision XT is used in a wide range of studies and how it can elevate your research!

  • Free white papers and case studies
  • Customer success stories
  • Recent blog posts

Decreased mobility

Swimming velocity and activity of Acropora millepora coral larvae were measured, and were found to be considerably decreased during exposure to all three antifouling compounds, with a 2-fold decreased mean swimming velocity in one treatment, compared to the control. In the DCOIT exposed group, activity and velocity were decreased to almost zero.

ethovision coral larvae lisa roepke
Dark box recording setup with antifouling-coated tile and silicone ring pools with coral larvae (© Lisa Röpke)

Measuring behavior is essential

Measuring behavior in coral larvae is extremely innovative. And the results of this study by Röpke et al. suggest that these coatings do have an effect on larval behavior, however without a clear indication whether this is due to biochemical interaction(s) with the larvae, toxicity, physical topographies, or some combination of these.

The coatings measured in this study were originally presumed to be non-toxic, thus to not cause mortality or interferences with juvenile coral fitness. However, when applied freshly without former conditioning in natural seawater they do seem to affect ecologically relevant parameters that are of extreme importance to coral reef viability. These changes in behavior are thus important endpoints to consider.

Standardization

The study by Röpke [2] also provides an insightful manual for using EthoVision XT with coral larvae, providing other scientists the means to perform rapid and reliable quantification of behavior in similar research, while also working towards standardization of such protocols.

Lisa Röpke is in the final stages of her PhD studies. Feel free to contact her regarding any questions on her study via email: [email protected] 

lisa roepke leibniz marine research
© Jan Meier, Leibniz Centre for Tropical Marine Research (ZMT)

Literature

  1. Roepke, Lisa K.; Brefeld, David; Soltmann, Ulrich; Randall, Carly J.; Negri, Andrew P.; Kunzmann, Andreas (2022). Antifouling coatings can reduce algal growth while preserving coral settlement. Sci. Reports 2022 121, 12 (1), 1–14
  2. Roepke, Lisa K.; Brefeld, David; Soltmann, Ulrich; Randall, Carly J.; Negri, Andrew P.; Kunzmann, Andreas (2022). Applying behavioral studies to the ecotoxicology of corals: A case study on Acropora millepora. Front. Mar. Sci., 9, 2458

Related Posts

The bat - moth aerial battle in 3D
05 May animal behavior research Other (Animal)

The bat - moth aerial battle in 3D

Moths arrived first on the evolutionary stage; when much later on bats appeared with their sophisticated apparatus for echolocating prey, moths were forced to change or die.
Time is of the essence in fish studies
04 May animal behavior research Other (Animal)

Time is of the essence in fish studies

You recently moved into your new house. How do you feel? How do you act in this new space? The answers may depend on how long you have lived there…
A new rat model for neonatal white matter injury
13 Feb animal behavior research Other (Animal)

A new rat model for neonatal white matter injury

Preterm birth is a major problem in neonatal healthcare. Erik van Tilborg developed a new animal model to closely mimic this clinical situation, an important step in finding new treatment options.