It’s sea otter awareness week, which seems like a great time to reveal something heroic about this charismatic animal. A recent study from UC Santa Cruz concluded that sea otters are helping to save the ocean—with their appetites.

When you think of sea otters, you may think “cute and cuddly,” but these playful marine mammals are top predators, like great white sharks and tigers, and their hunt for food is helping to maintain ecosystem health along portions of California’s coastline.

The sea otter’s role in ecosystem management begins with one of its preferred foods: crabs. Sea otters eat crabs. Crabs in turn eat sea slugs and small crustaceans. The slugs and crustaceans eat algae off sea plants, keeping them green and healthy. It’s a relatively typical food web but now it’s clear: The healthier the crab-eating otter population is, the healthier the plants tend to be.

Sea plants, like eelgrass, along the west coast are important habitat for fish such as Pacific herring, halibut and salmon. They also protect shorelines from storms and waves, and they soak up carbon dioxide from seawater and the atmosphere.  Thus, a healthy coastal ecosystem has the right mix of otters eating crabs and invertebrates eating algae.

Unfortunately, seagrass meadows have been declining worldwide, partly due to excessive nutrients from agricultural and urban runoff entering coastal waters.  When sewage and agricultural waste like fertilizers spill into the sea, ecosystems suffer. Excessive nitrogen and phosphorus in the water spawns excessive algae growth, which can block sunlight and limit plant growth. Coastal areas that would otherwise be swaying in seagrass and kelp turn brown, murky, and barren of important marine species. But, not when sea otters are around.

Brent Hughes from the University of California, Santa Cruz and his colleagues studied 50 years’ worth of data, comparing areas with or without otters. The team discovered that otters trigger the above ecological chain reaction that protects seagrass meadows and can stave off algal blooms.

“The seagrass is really green and thriving where there are lots of sea otters, even compared to seagrass in more pristine systems without excess nutrients,” Hughes says.

Sea otters were hunted to near extinction in the 19^th and 20^th centuries. Populations on the California coast are slowly recovering now, and one of those places otters have called home since the 1980s is Elkhorn Slough, an estuary in Monterey Bay. Hughes and his colleagues determined that the re-colonization of that estuary by sea otters has been an important factor in the seagrass comeback.

In Tomales Bay, a nearby inlet with far lower levels of incoming nutrients, but no otters, the beds don’t look nearly as good. Hughes told Ed Yong of National Geographic:

The seagrass looks relatively unhealthy: it’s brown, covered in algae, and slumped over. The crabs are four times more abundant and 30 percent bigger than they are in Elkhorn Slough.

The findings in Elkhorn Slough suggest that expansion of the sea otter population in California and re-colonization of other estuaries will likely be good for seagrass habitat—and coastal ecosystems—throughout the state.

“This provides us with another example of how the strong interactions exerted by sea otters on their invertebrate prey can have cascading effects, leading to unexpected but profound changes at the base of the food web,” Hughes says. “It’s also a great reminder that the apex predators that have largely disappeared from so many ecosystems may play vitally important functions.”

The study was published last month in the Proceedings of the National Academy of Sciences.

(Sea otters also play a heroic role in the next Academy planetarium show! Currently in production and set for a fall 2014 opening date, the latest production from our visualization studio will highlight complex relationships in ecosystems—and how humans fit into the picture.)

Jami Smith is a science geek-wannabe and volunteers for Science Today.

Image: Robert Scoles/NOAA

Healthy ecosystems often rely on secret agents. Not spies, but organisms that might not seem to have an obvious connection to a natural community. We reported on this earlier in the week when we described the influence of toucans on the evolution of palm trees in the Brazilian rainforest. Now, two other recent studies make these hidden, yet important, connections more apparent.

With coral reef ecosystems around the world under threat from climate change, coral bleaching and ocean acidification, Australian researchers are looking for resourceful ways to save these communities. Reporting in Nature Communications this week, a team led by Joseph Maina from Macquarie University determined that a coral reef off the coast of Madagascar could benefit from a healthy forest on the mainland.

It’s not obvious, but the scientists discovered that improving land-use management strategies, such as controlling sediment pollution caused by deforestation and soil erosion, are crucial to reef survival.

“Curbing sediment pollution to coral reefs is one of the major recommendations to buy time for corals to survive ocean warming and bleaching events in the future,” says co-author Jens Zinke of the University of Western Australia. “Our results clearly show that land-use management is the most important policy action needed to prevent further damage and preserve the reef ecosystem.”

In another study, published last week in PLoS Biology, researchers examined the role of species in a variety of ecosystems—from coral reefs to tropical forests to alpine meadows—in terms of their abundance. David Mouillot of the University of Montpellier 2 and his colleagues found that it is primarily the rare species, rather than the more common ones, that have distinct traits involved in unique ecological functions. As biodiversity declines, these unique features are particularly vulnerable to extinction because rare species are likely to disappear first.

Biodiverse environments are characterized by many rare species. These rare species contribute to the taxonomic richness of the area, but their functional importance in ecosystems is largely unknown. It is often assumed that they fulfill the same ecological roles as those of common species but have less impact because of their low abundance, but the work of Mouillot and his team shows that, in fact, the opposite may be true.

Examples of such functional species include the giant moray (Gymnothorax javanicus), a predatory fish that hunts at night in the labyrinths of coral reefs; the pyramidal saxifrage (Saxifraga cotyledon), an alpine plant that is an important resource for pollinators; and Pouteria maxima, a huge tree in the rainforest of Guyana, which is particularly resilient to fire and drought. Not only are these species rare, but they have few functional equivalents among the more common species in their respective ecosystems.

“Our results suggest that the loss of these species could heavily impact upon the functioning of their ecosystems,” says Mouillot. “This calls into question many current conservation strategies.” The authors argue that the preservation of biodiversity as a whole—not just the most common species—appears to be crucial for the resilience of ecosystems.

Image: David Mouillot/PLoS Biology

Protecting biodiversity is essential to our health and longevity on this planet. But can we quantify that value? Especially the economic value?

Late last year, researchers from the US and France attempted to put dollar amounts on the importance of biodiversity by correlating it to the prevalence of tropical disease in developing countries. According to their introduction in PLoS Biology:

Along with 93% of the global burden of vector-borne and parasitic diseases (VBPDs), the tropics host 41 of the 48 “least developed countries” and only two of 34 “advanced economies.”

They contend that economic growth falters when people get sick. (Seems reasonable.) And the spread of disease among humans, many scientists argue, can increase or decrease depending on factors in the natural environment, including biodiversity.

The more diverse an ecosystem, the greater the chance that a pathogen is diluted among numerous and potentially less-than-ideal host species and, therefore, the less abundant the disease. In 2002, researchers found this to be true with Lyme disease. NPR sums it up well:

If you have a rich community of tick hosts, like squirrels, mice and other small mammals, the disease is diluted among them. But if the habitat is degraded, and ticks carrying Lyme have only white-footed mice as hosts, the disease risk to humans can rise dramatically.

The Academy’s microbiologist, Shannon Bennett, weighed in on biodiversity’s impact on human diseases. In a recent email, she wrote:

I am sure biodiversity influences the transmission of infectious diseases one way or another.  Over 75% of new, emerging or re-emerging human diseases are caused by pathogens from animals, according to the World Health Organization. That means that the ecological communities we live in, and how pathogens cycle through the different players, are key to human health. Biodiversity is one way that we measure the complexity of these communities. In what way biodiversity is important, or how these communities specifically affect infectious diseases and risk, depends on the pathogen ecology and life history, and host species relationships.

Stanford researchers brought up this same point last month—“depends on the particulars,” as Bennett put it—in a study in Ecology Letters. A summary from the Stanford Report states:

The researchers found that the links between biodiversity and disease prevalence are variable and dependent on the disease system, local ecology and probably human social context.

The role of individual host species and their interactions with other hosts, vectors and pathogens are more influential in determining local disease risk, the analysis found.

That dovetails exactly with the research Bennett and Academy entomologist Durrell Kapan are conducting. They’re currently studying mosquito vector communities and the relationships between their biodiversity, the diversity of their microbes, and the presence of pathogens.

As for putting a price tag on biodiversity, Bennett encourages the PLoS study’s authors:

I find the authors’ argument intriguing and certainly a significant angle to consider in support of the health value of biodiversity, and one that is unique—no one has teased out the financial correlations between biodiversity and human societies. That it includes human health and infectious diseases is the angle I find particularly intriguing and worth following up on with empirical studies.

And on these studies of human disease and biodiversity in general? Bennett is excited about the possibilities of further research, including her own:

Increasingly we are recognizing and appreciating that humans are members of complex communities of other species, and that the make-up of these communities, whether they live inside of us or outside, can be very important to human health, as well as the health of all life. Human health and the health of life on this planet are coupled. We need to understand those coupling mechanisms better to ensure sustainability of that life, and the best way to understand those coupling mechanisms is with a multi-disciplinary approach, bringing together human health researchers with ecologists and evolutionary biologists, to name a few!

Some organizations have sprung up to do just that. Bennett points to two examples: the One Health Initiative and the EcoHealth Association. Whatever dollar value we assign to biodiversity and other ecosystem services, let’s wish these organizations luck in improving human health and well-being.

Image: CDC

Here’s one: Dimensions of Biodiversity, a program for graduate students funded by the National Science Foundation. It currently boasts 112 grad students from 14 institutions in five countries, with 23 faculty members advising these students.

Their mission? According to their website, “To prepare the next generation of biodiversity researchers for higher levels of academic and scientific interaction, while simultaneously advancing, synthesizing, and baselining knowledge of biodiversity science on a global scale.”

At the AAAS meeting last month, three members of the program talked about a few of the various projects of Dimensions of Biodiversity.

Selina Heppell, a professor at Oregon State University, discussed a project to measure biodiversity in the oceans utilizing commercial fishing data. Samantha Davis, a graduate student at UC Santa Barbara, described three separate projects looking at the variability in biodiversity in tropical forests. And Ailene Ettinger, a student at the University of Washington, looked at data about the efficacy of citizen science and the data collected by non-scientists. (Her PowerPoint opened with a picture of citizen scientists on the Academy’s roof!)

The young researchers are using existing data in each study, looking at old observations in entirely new ways. All of the projects span many institutions and approach biodiversity beyond species numbers. They look at the diversity of individual species, of course, but they also look at the diversity of groups of species and functions of each species. For example, you can look at functional biodiversity as how many herbivores, carnivores, top predators, and bottom dwellers exist within an ecosystem. Their diagram, above right, demonstrates this and the effects and influences to an ecosystem.

Students drive each endeavor, but they don’t need to select something within their particular program of study. And like the iGem teams, each project includes a diverse group of students—biologists, statisticians, writers, you name it.

And the results? A recent paper about remote sensing in rainforests and two more publications forthcoming (see here and here). Also an online blog that was introduced earlier this year at the popular Science Online conference.

The Academy supports a similar NSF-funded program, this one for undergraduates. The Summer Systematics Institute has been running for an astounding 17 years and “addresses critical issues such as, world-wide threats to biodiversity, the origins and diversification of life, phylogenetic systematics and evolutionary biology, which have become critical components of undergraduate education.” Stay tuned for a video about the SSI program, available on Science Today later this year.

Diagram courtesy of biodiverseperspectives.com

10 years

102 researchers from 21 countries

129,000 specimens

25,000 species in a 6,000-hectare forest

…yielding an estimate of 6 million arthropod species on our planet.

Ready for the details behind the numbers?

In 2003 and 2004, a large team of scientists (see numbers above) led by the Smithsonian Tropical Research Institute on an endeavor called Project IBISCA-Panama, scoured Panama’s San Lorenzo rainforest for arthropods (which includes insects, spiders, and millipedes).

They sampled the forest from top to bottom from a construction crane, inflatable platforms, and balloons, climbing ropes through forest layers as well as crawling along the forest floor to sift soil and trap arthropods.

They then spent the next eight years identifying the 129,000 specimens collected within twelve 20-by-20 meter squares. They determined that within those specimens, there were over 6,000 species of arthropods. Using various models the team extrapolated the total number of arthropod species to 25,000 residing in the 6,000-hectare forest.

The research is published in the current edition of Science.

According to Science Now,

The study is the most extensive survey of insects, spiders, and their relatives ever undertaken and should help researchers get a better understanding of what factors influence biodiversity.

“This is a high number as it implies that for every species of vascular plant, bird or mammal in this forest, you will find 20, 83, and 312 species of arthropods, respectively,” explains lead author Yves Basset.

“If we are interested in conserving the diversity of life on Earth, we should start thinking about how best to conserve arthropods,” adds Tomas Roslin, one of 35 co-authors.

“Another exciting finding was that the diversity of both herbivorous and non-herbivorous arthropods could be accurately predicted from the diversity of plants,” says Basset.

“By focusing conservation efforts on floristically diverse sites, we may save a large fraction of arthropods under the same umbrella. Further, this strengthens past ideas that we should really be basing estimates of global species richness on the number of plant species,” stresses Roslin.

For some amazing images of these arthropods and the collection process, please visit National Geographic.

Image: Thomas Martin, Jean-Philippe Sobczak, and Hendrik Dietz, T.U. Munich

Biodiversity informatics is a way to catalog life—its diversity and distribution, its past, its present—and potentially, its future. With the world changing so quickly, biodiversity informatics can be the key to protecting all of life on Earth.

The Academy’s Stan Blum leads our biodiversity informatics effort and his bio page describes his work well:

Academy scientists generate enormous amounts of information as they collect, describe, document, and compare organisms. That information comes in a variety of forms, including text, photographs, DNA sequences, taxonomic names, classifications, distributions maps, and ultimately publications.  Our goals in biodiversity informatics are to ensure that information is captured effectively when it is created, and flows efficiently through analysis, into appropriate outputs.

Capture Effectively

While biodiversity informatics would not exist without 21st-century technology, it’s actually been around since the mid-80s, undertaken by a group called the Biodiversity Information Standards or TDWG, from their original name—the Taxonomic Databases Working Group. As their name implies, the importance is on creating an industry standard to share the information on life stored in the collections of institutions like ours. Stan attended their conference last month in New Orleans. Through conferences such as these, 250 or so biodiversity informatics scientists from all over the world develop new technologies and share best practices to catalog life—its evolution, ecology, biogeography and more.

Appropriate Outputs

Cataloging allows scientists throughout the world to use the data for different research projects. From building the Encyclopedia of Life to challenging old models of plant distributions on islands to understanding threatening invasive species—the primary data supporting these studies are assembled and shared through another organization called the Global Biodiversity Information Facility (GBIF).

And this is just the birth of this notion. As more collections—in addition to the Academy’s—become part of these catalogs, they will become more vital in protecting all life on our wonderful planet. “Conservation depends on this information,” Stan urges.

21st-century science to address 21st-century concerns…

Image: Tom Harpel/Wikipedia

It is known that biologically diverse streams are better at cleaning up pollutants than less rich waterways, so Bradley Cardinale of the University of Michigan created 150 miniature model streams to find out why this is.

The model streams use recirculating water in flumes to mimic the variety of flow conditions found in natural streams. Cardinale grew between one and eight species of algae in each of the mini-streams, then measured each algae community’s ability to soak up nitrate, a nitrogen compound that is a nutrient pollutant of global concern. He found that nitrate uptake increased linearly with species richness. On average, the eight-species mix removed nitrate 4.5 times faster than a single species of algae grown alone.

The reason? Niche partitioning, Cardinale said.

In the stream experiments, each algae species was best adapted to a particular habitat in the stream and gravitated to that location—its unique ecological niche. As more algae species were added, more of the available habitats were used, and the stream became a bigger, more absorbent sponge for nitrate uptake and storage.

Sound familiar? Think Charles Darwin. “People as far back as Darwin have argued that species should have unique niches and, as a result, we should see a division of labor in the environment,” Cardinale said.

This is exciting news because nitrate is an ingredient in many fertilizers and is found in surface runoff from agricultural land that makes its way into streams, lakes and coastal zones. It is a leading cause of degraded water quality worldwide.

“The primary implication of this paper is that naturally diverse habitats are pretty good at cleaning up the pollutants we dump into the environment, and loss of biodiversity through species extinctions could be compromising the ability of the planet to clean up after us,” according to Cardinale.

Image credit: Danuta Bennett

Villy Christensen of the University of British Columbia (UBC) said, “Yes, there will be fish left, but it will be a very different ocean from the ones your parents and grandparents knew and even different from now.”

The biggest difference? Large, predatory fish will be gone.

In fact, over the last one hundred years, the population of these large, top-of-the-food-web fish has declined by two-thirds, half of that decline occurring only in the last 40 years. And that population continues to decline.

There will be many small fish left, but not necessarily the ones we eat.

He and his colleague, Reg Watson, also from UBC, are working with scientists, governments and NGOs to build a global database of fishing efforts to truly understand what’s going on in the world’s oceans.

Seventy-six million tons of fish are consumed each year, and Watson found that we are fishing harder for the same or less result. It’s possible that we’ve hit “peak fish,” according to Watson. Jacqueline Alder of the UN Environment Program in Kenya is working with the UBC group, looking at their models in terms of marine biodiversity and sustainability. She urged that we must reduce fishing efforts immediately to allow fish stocks to rebuild.

In addition, there was much discussion around the non-sustainability of using fish for feedstock in aquaculture and agriculture– fish we are not directly eating. The science and technology have to get better to use plant-based feedstock for fish farms.

Christensen stressed this is a large view of what’s going on in the entire ocean ecosystem, not just one area or species.

For more focused, local information, read our recent article on banning shark finning, and the San Francisco Chronicle had a devastating article last week stating that some of the fish in the Delta may be too far gone to save from extinction.

Image: Mila Zinkova/Wikimedia