Climate Change Impacts Marine Organisms by Altering Their Sensory Pathways

Research related to the effect of global change on marine organisms has traditionally concentrated on physiological effects.

Climate Change Impacts Marine Organisms by Altering Their Sensory Pathways" />

One classic example is the decreased ability of an oyster to maintain or build a robust shell in an ocean that is turning out to be more acidic as a result of high concentrations of carbon dioxide. Of late, scientists have started to explore how animal behavior is disrupted by varied facets of global change.

Currently, a study headed by Dr Emily Rivest of William & Mary’s Virginia Institute of Marine Science has produced the results of these first-ever behavioral studies—exposing broad patterns as well as interesting outliers. This study offers a theoretical framework to help guide upcoming studies in this evolving field.

Climate change will significantly impact marine organisms by altering sensory pathways. This will have consequences for ecological and evolutionary interactions, including mating, predation, and habitat selection.

Dr Emily Rivest, Assistant Professor, Virginia Institute of Marine Science

As a case in point, Dr Rivest quoted a study that was performed in 2016 and headed by co-author Brittany Jellison of the University of California, Davis. The study demonstrated that tidepool snails are more vulnerable to sea-star predation as a result of ocean acidification. This trend disrupts the creatures’ capacity to process and react to chemical cues that are left behind by starfish in the ocean.

A new study, headed by Virginia Institute of Marine Science (VIMS) in the Chesapeake Bay, is also investigating how ocean acidification is likely to have an impact on a predator-prey interaction, which occurs between clams and blue crabs.

The ongoing study, predicated on a review of 120 relevant journal articles, seems to be the most recent issue of Frontiers in Marine Science. Apart from Jellison and Rivest, the study was co-authored by Erin Satterthwaite, Gabriel Ng, Brian Gaylord, and Susan Williams of UC Davis and also by Hannah Bradley of James Madison University. The National Science Foundation funded the study.

Sensory Pathways

One of the main objectives of the study was to explain how human pressures on the environment could have an impact on every step in the sensory pathways between sea creatures.

“Our review,” stated Rivest, “emphasizes that behavior is the outcome of a sensory pathway that includes the production of information, transmission of that information through the environment, reception of the information by an organism, and then a response—what the organism decides to do with the information.”

In addition, the review differentiates between data generated incidentally—what researchers call a cue—and data that is deliberately produced by a marine organism—a signal.

“Knowing where, and in how many places, climate change breaks that pathway,” Rivest added, “will help us anticipate how it might affect broader ecological processes, like food-web and population dynamics.”

If we can better illuminate where climate change stressors impact the sensory pathway, then we can develop more targeted, effective management and conservation efforts.

Erin Satterthwaite, Study Co-Author, University of California, Davis

The researchers’ review cited instances of the effects of global change at each step in the sensory pathway. For instance:

• Studies performed on weakfish as well as croaker, well-known recreational fish species in the Chesapeake Bay, discovered that increased turbidity and warmer waters modify the production of sounds used by males of both species to lure females, thereby possibly impacting the breeding success.
• Studies performed on cormorants showed that increased turbidity caused by more frequent cloudbursts and nutrient pollution can degrade the transmission of light, potentially decreasing feeding success among these extremely visual avian predators.
• According to a 2013 study, breeding cobia larvae in waters containing increased levels of carbon dioxide have an impact on the creatures’ otoliths, which may modify their capacity to detect sound. Otoliths are actually calcified bodies that are present in the inner ear and used by vertebrates to perceive movement and gravity.

For their global-change impacts, the researchers selected those that were listed by the Intergovernmental Panel on Climate Change (IPCC) in its latest report—increasing temperatures, improved low-oxygen zones, ocean acidification, increased turbidity, heightened UV-B radiation, salinity changes, excess nutrients, greater stratification, and altered hydrodynamics.

Part of the U.N. body, the IPCC has been tasked to direct the international response to the present climate-change crisis.

Think Globally, Act Locally

The researchers’ findings hold implications on both the local and international scale.

First, we found there are some generalizable mechanisms. If a global change stressor affects the production of a visual cue or signal, it’s likely to affect the production of acoustic and chemical cues and signals as well, and vice versa.

Dr Emily Rivest, Assistant Professor, Virginia Institute of Marine Science

Undeniably, among the five environmental factors that had an impact on production—ocean acidification, growing temperatures, increased turbidity, salinity changes, and low oxygen—four did so for numerous senses. It was found that ocean acidification impacts the production of auditory, olfactory, and visual cues and signals.

“We think the common denominator could be physiological stress,” stated Rivest. “The change in temperature, salinity, or ocean acidification stresses the organism and may impair its ability to produce a cue or signal.”

However, when it comes to transmission, the researchers’ review revealed that global change stressors are likely to have an impact on only one mode—that is, olfactory, visual, or acoustic. For example, Rivest cited a study that established the fact that increased nitrogen from land-based runoff was largely responsible for the decline of a Florida coral reef.

“That’s one of the benefits I see of doing work like this is,” added Rivest. “If you can better understand the relationship between pathways and more local stressors such as nutrient pollution, then you have a more tractable way to make a difference.”

“Rather than trying to affect the behavior of the whole world—to lower carbon emissions—you could work to manage local causes of pollution such as land clearing and stormwater runoff. These local solutions may actually be more effective in some places, and they are not currently getting as much attention,” Rivest concluded.