[Tide Bites] Understanding the Effects of Ocean Acidification on Predator-Prey Interactions

This article comes from “Tide Bites”, the monthly newsletter of UW Friday Harbor Laboratories. Seroy, S. (2017, July). Understanding the Effects of Ocean Acidification on Predator-Prey Interactions. Retrieved from https://fhl.uw.edu/about/news-and-events/newsletters/. [link to original article]. Applications for undergrads wishing to study and research at Friday Harbor Labs this autumn are still being accepted.

Understanding the Effects of Ocean Acidification on Predator-Prey Interactions

by Sasha Seroy

Sasha Seroy is a graduate student in the Oceanography Department at the University of Washington, advised by Dr. Daniel Grünbaum.

Marine organisms are experiencing dramatic environmental changes due to global climate change. As atmospheric carbon dioxide concentrations rise, the oceans absorb increasing amounts of carbon dioxide, which results in acidification. While ocean acidification affects several different types of organisms, calcifiers — those that make their shells or skeletons from calcium carbonate like shellfish or corals — have been identified as particularly vulnerable. Acidification not only increases the likelihood of shell or skeleton dissolution, it can also make it more difficult for organisms to create calcium carbonate in the first place. Several studies have investigated the effects of ocean acidification on calcifiers in isolation; however, in nature, organisms interact with a wide variety of other organisms, from predators to prey to competitors. These interactions have the potential to amplify or reduce the effects of acidification with consequences that could propagate up to population and community levels. I am particularly interested in how interactions between predators and prey are influenced by changing ocean chemistry.

bryozoan colonies
Fig. 1: Individual feeding zooids within a bryozoan colony (left), an entire single bryozoan colony (center), and multiple bryozoan colonies growing on kelp (right).

The encrusting bryozoan Membranipora membranacea is commonly found in the waters around San Juan Island and presents a good model system to investigate the effects of acidification on predator-prey interactions. Membranipora forms large circular colonies composed of zooids — the individual units within a colony (Figure 1) — on kelp blades. As they grow, colonies add subsequent rings of zooids to their outer edge. This structure makes it simple to divide colonies like cutting a pizza, and then expose genetically identical slices of the same colony to different environmental conditions via laboratory manipulations. Membranipora exhibits an inducible defense — a defense that is only formed in the presence of predators — which helps protect them from being eaten. Upon receiving chemical cues that the predatory sea slug Corambe steinbergae is close by, Membranipora produces spines on skeletons of newly-formed zooids along the outer growing edge of the colony (Figure 2). While these inducible spines are beneficial, they present a trade-off because they require energy to make, and leave less energy to put toward colony growth. Therefore, the cost associated with increased protection is a reduction in overall colony growth. Thus, similar to tree rings, we can see which rings of zooids were formed at a time of high predation by looking for defensive spines. Since these interactions are easy to quantify and Membranipora forms its skeleton from calcium carbonate, this system is a good model to understand how ocean acidification might affect predator-prey dynamics.

[read the full post at FHL Tide Bites]

[UW Today]: Ocean acidification to hit West Coast Dungeness crab fishery, new assessment shows

from UW Today, January 12

The study modeled the potential risks of ocean acidification (under a future decrease in pH) on the West Coast marine food web and fisheries over 50 years, from 2013 to 2063.

The acidification of the ocean expected as seawater absorbs increasing amounts of carbon dioxide from the atmosphere will reverberate through the West Coast’s marine food web, but not necessarily in the ways you might expect, new research shows.

Dungeness crabs, for example, will likely suffer as their food sources decline. Dungeness crab fisheries valued at about $220 million annually may face a strong downturn over the next 50 years, according to the research published Jan. 12 in the journal Global Change Biology. But pteropods and copepods, tiny marine organisms with shells that are vulnerable to acidification, will likely experience only a slight overall decline because they are prolific enough to offset much of the impact, the study found.
“What stands out is that some groups you’d expect to do poorly don’t necessarily do so badly – that’s probably the most important takeaway here,” said Kristin Marshall, lead author of the study who pursued the research as a postdoctoral researcher at the University of Washington and NOAA Fisheries’ Northwest Fisheries Science Center. “This is a testament in part to the system’s resilience to these projected impacts. That’s sort of the silver lining of what we found.”Marine mammals and seabirds are less likely to be affected by ocean acidification, the study found.

[read the full article at UW Today]

[UW Today] Ocean acidification study offers warnings for marine life, habitats

Coral ecosystems, like these pictured off the coast of Mexico, will be hit hard as the oceans become more acidic.
Christopher Harley/University of British Columbia
Coral ecosystems, like these pictured off the coast of Mexico, will be hit hard as the oceans become more acidic.

Acidification of the world’s oceans could drive a cascading loss of biodiversity in some marine habitats, according to research published Nov. 21 in Nature Climate Change.

The work by biodiversity researchers from the University of British Columbia, the University of Washington and colleagues in the U.S., Europe, Australia, Japan and China, combines dozens of existing studies to paint a more nuanced picture of the impact of ocean acidification.

While most research in the field focuses on the impact of ocean acidification on individual species, the new work predicts how acidification will affect the living habitats such as corals, seagrasses and kelp forests that form the homes of other ocean species.

“This work demonstrates the value of international collaborations to address a problem that’s global in scope and crosses boundaries between distinct habitats and ecosystems,” said co-author Terrie Klinger, professor and director of the UW’s School of Marine and Environmental Affairs who also co-directs the Washington Ocean Acidification Center. “We can begin to test predictions with data from different locations to better understand likely ecosystem responses to ocean acidification.”

[Read more at UW Today]