Ocean Resilience: Biodiversity’s Role in Coping with Adversity
The intricate interaction of habitat and inhabitants—both marine and human—holds the key to the ocean’s ability to support us all.
A portfolio made up of one type of security, or even containing a single stock, would be a risky one. It wouldn’t always perform well, and could easily prove disastrous during an economic crisis. We could say that this type of portfolio would not be resilient and would be challenged to recover from difficult times.
Resilience in the ocean is much the same, and biodiversity can be thought of as a portfolio of living things. Director Emmett Duffy explains: “The more species—or diversity—you have in a system, the more that diversity buffers you from variation in the environment, just like a diverse stock portfolio buffers you from variance in the economy.”
We all depend on stability to survive and thrive. However, we’re living in a world that’s changing rapidly. Humans are taking massive amounts of fish from the ocean, dumping trash and pollution into it, inadvertently transporting invasive species, and changing the global climate. Since the benefits we receive from the ocean are vast—it provides food, maintains clean water, protects our shoreline and disposes of waste, both atmospheric and otherwise—understanding the ocean’s resilience is of utmost importance.
“In order to continue to receive these benefits,” Dr. Duffy says, “we need to know that the ocean ecosystem is able to handle what we’re throwing at it. Resilience is the ability of the system to handle those impacts and continue to provide services. So we’re striving to understand how that resilience works—and what aspects of the ecosystem maintain its resilience.”
MarineGEO has a variety of research efforts underway in the quest to unlock the mysteries of resilience and how biodiversity strengthens it. “Biodiversity is the heart of resilience, which is one reason why MarineGEO is so focused on biodiversity,” he says. “Another reason is that most of the existing ocean observing networks have neglected biodiversity. So it’s a big hole in what we know about how coastal ecosystems operate.”
The Interplay of Native and Invasive Species
Exploding populations of non-native species have wrought havoc on both land and sea, from kudzu overtaking forests to lionfish gobbling up reef fish in the Caribbean. Brian Cheng, a postdoctoral fellow with MarineGEO, is looking at exactly this aspect of resilience: the ability of an ecosystem to resist the introduction of non-native species.
“We have only begun to unravel the role of predation, or consumption, by native species and how this affects invasion,” Dr. Cheng says. “For example, what if a native fish could prevent the establishment of invasive species, simply by consuming all of the newly introduced plants or animals.”
Cheng has developed a series of standardized field experiments to safely test the interaction among non-native species and native predators, and he is conducting them in seagrass meadows across a broad expanse of ocean, from the temperate zones of Connecticut and Virginia down to Florida and the tropical areas of Belize and Panama.
Designing experiments that are standardized across all locations is a very powerful way of reliably comparing patterns across vast areas, a key goal of MarineGEO. But finding uniformity in the ocean can be a challenge.
“One issue is that species are often restricted to the temperate zone or the tropics, making comparisons across these regions difficult,” he says, “but we are using two groups of animals that are widely distributed throughout the Atlantic Ocean—bryozoans, or moss animals, and tunicates, or sea squirts.” Similarly, seagrass meadows can be found from temperate to tropical latitudes. This experiment not only measures predator type and activity, but also helps reveal geographic variation.
Preliminary findings have been surprising. Because of the diversity of the tropics, it was widely assumed that their predators would be more voracious. However, Cheng found that predators are just as active at his temperate sites, implying that tropical diversity does not automatically provide special protection from invasions, as was previously thought. Therefore we should be as careful about human-assisted introductions in warm waters as we are in the cooler regions.
“We have a lot of work to do to figure out how native predators can control invasive species,” asserts Cheng. “In the meantime, the safest approach to managing these ecosystems is to preserve biodiversity and the function that these communities may provide in controlling invaders.”
We need to be mindful that increased human traffic, particularly with the expanded capacity of the Panama Canal and the opening of new shipping lanes through the increasingly ice-free Arctic Ocean, has the potential to mix marine species and homogenize the life of the world’s oceans, with possibly grave consequences for the ocean’s resilience. Globalization has indeed made the Earth a much smaller place.
Healthy Biodiversity Means Healthy Fisheries
There is a very strong linkage between the health of marine systems and the health of the fisheries they support. As increasing numbers of fish and other species are taken out of an area, a negative feedback loop can occur, especially in reefs. When reef-cleaning herbivores like parrotfish are removed, the health of the ecosystem as a whole often declines. And as the reefs start to degrade, their ability to support fish populations also start to decline, and people have to fish even harder to make a living.
Stephen Box, Smithsonian researcher and MarineGEO executive committee member, is making headway in breaking this vicious cycle. Dr. Box began by working with small-scale fishers in the Caribbean and Southeast Asia to systematically record catch information. Through these data, Box is helping define the importance of local fisheries to coastal communities and provide fishers with information that can give them a voice in how their fishery is managed.
“The problem has been that previously it was incredibly difficult to collect fisheries information from small rural communities across large areas of coastline,” Box says. “As a result we really didn’t know what was happening in those near-shore fisheries. Most biodiversity, especially in tropical marine systems, is in shallow waters, in coral reefs, mangroves and seagrass beds. It is in these areas that people fish, so you have this chronic impact from human use that wasn’t being well quantified.”
To help communities document their activities, Box and his team developed a novel, picture- and icon-based Android app where buyers can easily record the catch being purchased from fishers. This visual application overcomes the challenges of language and low literacy and makes it especially applicable for fishers in the developing world.
Fishers and buyers have been very engaged in the initiative, helping in the initial design and then testing and providing feedback. Capturing data on these small, fragmented and dispersed fishing communities will demonstrate their contribution to food security and the national economy, and more accurately reflect the pressures on the fisheries as a whole.
While half of the program is trying to capture the production from these fisheries, the other half is considering how to design marine protected areas and no-take zones to reflect the fishers’ priorities as well as conservation objectives.
“The question is, how can we start putting in these areas that can protect the biodiversity that we know underpins productive fisheries, but site them in such a way that the benefit from those reserves spills over into the fished areas,” he says. “So to be able to do that, we have to understand both the ecology and movement of the target species, but also the movement and activities of the fishers themselves as ‘predators’ of these species. That’s the piece that hasn’t been captured very well previously, and it’s a new element that really needs to be incorporated into the marine reserve design.”
However, another aspect is being able to determine the success of these protected areas. “With a lot of marine management in developing countries, strategies are developed and implemented, but the mechanisms to measure whether they are actually working are not in place,” he says. “This is because no one has been doing the long-term monitoring to see if there is ecosystem recovery, and if biodiversity is being retained or even increasing, and from a fishery side, whether catches are improving.”
“With baseline monitoring data from MarineGEO, we can start drawing a straight line between a human-driven impact on the marine environment—fishing—and the quality of the marine environment,” he says. “So as we come up with improved marine reserve networks and start limiting specific types of damaging fishing activities, like trawling or dynamite fishing, we can determine whether there is measurable change in the condition of marine systems that are connected to that fishery. That will be a great outcome.”
As the management of fisheries and protected areas require decades-long commitments, so do efforts to quantify and understand the health of the ocean and its biodiversity. MarineGEO is taking the pulse of marine systems around the world, not only capturing a snapshot of how ecosystems are doing today, but building datasets that will track change over time, providing critical information about the condition of the marine environment, how it’s changing, why it’s changing, and thus its resilience.
“I think the Smithsonian is uniquely placed to be able to make these long-term commitments to take biodiversity and ecosystem monitoring from MarineGEO and then link it to the human use of marine systems,” Box says. “That’s a very powerful combination—I would say unparalleled. That’s the vision that we are aiming at.”