Yearly Archives: 2018

The Key to Successfully Conserving Our Salt Marshes

Benthic Ecology Blog Post by: Natalie Posdalljian

Coastal ecosystems are suffering rapid decline and increased degradation as a result of human disturbances. Finding successful solutions for conserving and protecting important habitats is critical. Formerly perceived as coastal ‘wastelands’, salt marshes are one of the most underappreciated coastal systems. In addition to housing a wide variety of flora and fauna, salt marshes are extremely productive coastal systems that serve as a barrier between land and sea. Extremely vulnerable to human activity, tidal marshes are in trouble and efforts worldwide have ramped up to stave decline. Restoration, or returning habitats back to a healthy condition, is a promising yet challenging method used for conserving salt marshes. Successful restoration requires effective initial rehabilitation of the habitat and long-term persistence, stability, and resiliency in the face of future natural and human disturbances. Restoration isn’t always successful and attempts could result in partial recovery or complete failure, where restored conditions do not match those of natural marshes. A new study might have found the key to amplifying salt marsh restoration success; fostering mutual interactions between species.

What Are Salt Marshes?

Continuously flooded and drained by tides, salt marshes are found worldwide, along every U.S. shoreline and most commonly within estuaries. Salt marshes facilitate complex food webs including primary producers (i.e. salt-tolerant grasses, vascular plants, phytoplankton, etc.), primary consumers (i.e. zooplankton, molluscs, insects, etc.), and secondary consumers (i.e. birds and fish). What makes salt marshes particularly unique is their existence between land and sea, linking marine habitats and organisms to their terrestrial neighbors directly inland.

Why Are Salt Marshes Important?

Salt marshes provide a wealth of services, referred to as ecosystem services that make them extremely valuable habitats to conserve. Salt marshes serve as nursery habitats for a variety of marine life, including more than 75 percent of fishery species. Wading birds feed in these productive habitats while migratory birds use salt marshes as stopping points on their routes. Salt marshes serve as a buffer between land and sea, filtering nutrients, run-off, and heavy metals, even shielding coastal areas from storm surge, flood, and erosion. These transitional ecosystems are also vital in combating climate change by sequestering carbon in our atmosphere.

What Natural and Anthropogenic Disturbances Do Salt Marshes Face?

Salt marshes occupy prime coastal real estate sharing the shoreline with around 10 percent of the world’s population or nearly 600 million people, according to the United Nations. This makes marshes extremely prone to human disturbances, especially habitat loss seen from land reclamation for urban development and agriculture. Being surrounded by these areas leads to an influx of nutrients in the form of sewage, agricultural run-off, and industrial waste.

Enrichment by excess nutrients causes shift in vegetation structure and provides non-native organisms the opportunity to invade and thrive in salt marshes. Invasive species like the common reed in Narragansett Bay, outcompete indigenous reeds and marsh grasses eventually leading to decline of wildlife and plant diversity, species abundance, and in the worst-case scenario, extinction,

Overfishing is often also blamed for degradation of salt marsh habitats. Loss of top predators like cod, striped bass, and blue crabs has been linked to collapse of salt marshes. With top predators being commercially and recreationally fished out, voracious herbivores like marsh crabs take over and destroy cordgrass, an essential wetland plant. The consumers who are being overfished play an important role in regulating these communities and removing them out of a system could lead to its collapse.

Climate change, and associated sea level rise, also negatively affect salt marshes. Distribution of plants and animals within marshes are based on various factors, especially tolerance of specific organisms to salinity and wetness. Temporary or permanent flooding from sea level rise could drown certain plants, not giving them enough time to move further inland in order to survive, and lead to erosion of the marsh into open water.

How Can We Conserve Salt Marshes?

As salt marshes are reinterpreted, their ecosystem services become better understood.  This results in an increase of conservation efforts to the tune of 1 billion US$ worldwide. Efforts include proper management of existing marshes, introduction of legislation to protect ecologically important habitats, reduction of intense development along the coast, and restoration of damaged marshes.

Two ideologies exist when considering options for restoring salt marshes.  One option acknowledges that humans have done enough damage. Perhaps habitats are better off with no additional anthropogenic interference and only require time and space to recover naturally. The second option emphasizes restoring degraded habitats back to their natural state.  Restoration efforts include removing non-native species, removing dikes, levees, etc. to restore natural tidal influences, and establishment of a single foundation species to facilitate the return of natural biodiversity. Although great in theory, restoration is logistically difficult, expensive, labor- intensive, and not always successful.

So, What Is the Key to Restoration Success?

Positive interactions are relationships between different species that result in better growth, reproduction and/or survival for at least one species involved in the interaction without negatively affecting the other species. Several studies have found that positive interactions reduce physical stress and increase resource availability within salt marshes. For example, mussels stabilize and fertilize soil that benefit the cordgrass, a primary foundation species.

Cordgrass traps sediments, creates low-marsh habitats, provides site for mussels to attach, and contribute dead plant matter to their diet. Positive interactions, such as those between mussels and cordgrass, play an important role in the function and stability of marshes. However, consideration of these implications and the potential of harnessing these interactions to improve salt marsh restoration has been limited thus far. In fact, a survey found that only 1 out of 25 restoration agencies in the U.S. considered positive interactions within their restoration design.

A group of scientist from all over the world set out to investigate whether positive interactions between cordgrass and mussels can increase restoration success in degraded U.S. salt marshes. They found that co-transplanted mussels, those transplanted with cordgrass, increased nutrients and reduced sulphide stress for local cordgrass. In return, this increased cordgrass growth and expansion throughout the habitat. Then the scientists simulated a disturbance and removed above-ground vegetation and mussels. They found that co-transplanted cordgrass had three times the survival rate compared to cordgrass that was transplanted without mussels. Not only did co-transplantation enhance cordgrass and mussel growth, it also improved resiliency of the foundation species to disturbance. Overall, the study found that mussels amplified cordgrass recolonization and resilience across broad spatial and temporal scales and utilizing these relationships could improve restoration success.

Integrating positive interactions is a simple yet promising tool to incorporate into restoration design across all coastal ecosystems. This tool has the potential to improve initial restoration success and also long-term resiliency, especially in the face of disturbances that these habitats will no doubt face in coming decades. This study contributed yet another method into the restoration toolbox that managers and policymakers should utilize in conjecture with other established methods to rehabilitate and reconstruct coastal ecosystems.

This newspaper article was inspired by NPR science and the following study,
http://onlinelibrary.wiley.com/doi/10.1111/1365-2664.12960/abstract.


 

New inhabitants of seafloor and shoreline habitats in Central California surprise researchers, provide new insight into valuable coastline

Benthic Ecology Blog Post by Tyler Hee

Researchers have found surprising abundances of non-native species in several intertidal habitats (the area of shore exposed at low-tide and submerged at high-tide) and subtidal habitats (the shallow are just below the intertidal) along the important, exposed coastline of Central California. Watersipora a non-native group of bryozoans, or marine invertebrates that live in colonies, and are usually found in calmer waters but was found extensively distributed during the surveys. Additionally, Caulacanthus ustulatu, a species of red turf alga that can form dense patches and outcompete native algae species was found at several survey sites.

Generally, more invasive or non-native species of marine organisms are reported in harbors, bays, and estuaries than in wave-battered, open-coast habitats like those found along Central California. Perhaps due to this difference, there is less concern and more infrequent management efforts for non-natives along the coast of Central California. This indifference however, should be addressed as the subject area of this study is extremely important both ecologically and economicall.

What’s so special about coastal Central California?

The area studied by Zabin et al. covered 275 km, stretching from Pt. Reyes located north of San Francisco Bay southward to Ventura Rocks just south of Monterey Bay. These waters include the Greater Farallones National Marine Sanctuary (GFNMS) and the Monterey Bay National Marine Sanctuary (MBNMS). From estuarine wetlands to rocky shores to kelp forests and open ocean, these two sanctuaries protect important aquatic habitats. These habitats are important for a wide range of fish and marine mammals – some of which are endangered or threatened – that call the waters off Central California home.

These coastal waters, rich with life, are important not only for the animals and other organisms that live there but for the human communities in the area. GFNMS supports 508 commercial and recreational fishing jobs each year with a combined fisheries worth of $53.2 million. Even more staggering, the non-consumptive uses of GFNMS, namely tourism and related activities, supports 1,131 jobs and generates an output of $145.8 million. Not to be outdone, commercial and recreation fisheries in MBNMS annually supports 1,755 jobs and creates an output of $194.8 million. The non-consumptive uses of MBNMS support 542 jobs and generates and output of  $69.4 million each year.

Clearly, the areas examined by Zabin et al. are both diverse, ecologically important marine habitats as well as extremely important natural resources that support vital coastal economies for California. Thus, understanding possible trends and developments of potential invasions by non- native species is crucial to the long-term ecological and economic health of the region.

Non-native species found in unexpected areas
The team of scientists surveyed 20 areas in the 275 km stretch of coast from 2014-2015. They looked at an array of intertidal and subtidal sites and recorded the number of and percent of sea floor coverage by non-native species at the study sites. Upon completion of their study, the team found that while numbers of non-native species in these exposed coastal systems are not as abundant across the entire range as in sheltered areas such as harbors, there were some species that were much more common than expected.

The small colonial group of animals, Watersipora, was found in 45% of the study area at one site and 26% lower in the tidal area at the same site. Additionally, the red turf alga Caulacanthus ustulatus, which may compete with native turf alga, was found to cover nearly 20% of the shoreline at one study site.

Despite limited findings, big implications about potential vulnerability in Central California
This study marks the first recorded account of Watersipora in the cooler, wave-exposed waters of Central California. The spread of these invertebrates into waters thought to be too cool and exposed to wave shock could be an important indicator of broader environmental changes to these ecosystems such as warming ocean conditions or adaptation by the non-native animal.

The data collected on the red turf alga, Caulacanthus ustulatus, is the first numerical report for the non-native seaweed. The high coverage at one of the teams Central California study sites is of interest because of the observed impacts this non-native alga has had on native algae and invertebrates in Southern California waters.

The observation of these non-native species in the coastal habitats of Central California merits further attention. There is currently insufficient data to fully understand what trends may or may not be occurring to allow these non-native species to spread to areas previously believed to be highly resistant to such expansion. There is also no information on what impact or damage may be occurring as these species being to occur in new habitats. Further study is needed to ensure effective management decisions of this ecologically and economically important area.

What’s next?

The novel observation of Watersipora and Caulacanthus ustulatus in the typically cooler, open- coast systems of Central California at unexpected abundances may result from by the species or may signal broader regime shifts. Similar to the supposed northward range expansion of tuna crabs off Southern California, the observation of these non-native species in new territory may be linked to changing ocean conditions, namely warmer water. The causes behind these occurrences should be examined because they may help to further explain the changing ecosystem structures of other Central and Northern Califronia habitats like the spike in purple urchins and loss of kelp beds. Thus, before conservation and management decisions can be made in response to changing conditions, we must first ask “what’s driving these changes?” To make decisions before that question is answered puts the ecosystem health and economic value of the Central California coast area in unnecessary jeopardy.

References

Laura Smith-Spark. Red Tuna Crabs Wash Up on San Diego Beaches. 17 June 2015. https://www.cnn.com/2015/06/17/us/californiasan-diego-crab-invasion/index.html.

Office of National Marine Sanctuaries. Gulf of Farallones National Marine Sanctuary: Commercial Fisheries – Economic Summary. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. 2014. Economic Contributions from Recreational Fishing in Greater Farallones National Marine Sanctuary, 2010 – 2012. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. Monterey Bay National Marine Sanctuary: Commercial Fisheries – Executive Summary. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. 2014. Economic Contributions from Recreational Fishing in Monterey Bay National Marine Sanctuary, 2010 – 2012. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Office of National Marine Sanctuaries. Dec 2015. Socioeconomics of California’s Northern Central Coast Region: Economic contributions from non-consumptive use. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Office of National Marine Sanctuaries.

Swierts, T., & Vermeij, M. J. (2016). Competitive interactions between corals and turf algae depend on coral colony form. PeerJ, 4, e1984.

Zabin, C. J., Marraffini, M., Lonhart, S. I., McCann, L., Ceballos, L., King, C., … & Ruiz, G. M. (2018). Non-native species colonization of highly diverse, wave swept outer coast habitats in Central California. Marine Biology, 165(2), 31.


 

Are we changing coral reefs and the ecosystem services they provide?

Benthic Ecology Blog Post by Travis Courtney

Coral reefs provide about half a billion people around the world with food, coastal protection, building materials, and/or income (1). Thirty million of those people live on atolls and are nearly entirely dependent on the ecosystem services provided by coral reefs for their livelihood (1).

Despite their great importance, coral cover has declined in recent decades primarily due to a combination of increasing global seawater temperatures and local overfishing, pollution, and land use changes (2,3). Corals are the dominant reef builders making these losses in coral cover particularly alarming for the people depending on coral reef ecosystem services. A recent study (4) led by Jennifer Smith at the Scripps Institution of Oceanography and published in the scientific journal Proceedings of the Royal Society B supports these alarming concerns with the finding that human impacts on coral reefs across the tropical Pacific Ocean may be negatively impacting the very ecosystem services we depend on.

An example of an inhabited island surrounded by a coral reef (5).

The team of researchers explored local human impacts on coral reefs by comparing coral reefs at 450 sites from 56 islands spanning 50° of latitude over the last 10 years. They looked at both inhabited islands and remote uninhabited islands to test whether coral reefs around islands with human populations were different from coral reefs surrounding uninhabited islands. The scuba diving researchers took over 6500 photos of the coral reef seafloor and analyzed them using computer software to determine the total proportion of corals and different types of algae at every reef location. By looking at the abundances of the different reef building corals and algae relative to the non-reef building algae species, they could test whether humans were potentially changing the abilities of coral reefs to not only grow, but also recover from disturbances like elevated temperature stress and storm activity too.

The researchers recorded 37% fewer reef-building corals and 40% fewer calcifying algae on inhabited island reefs compared to uninhabited island reefs. This striking difference in reef- building species led the researchers to conclude that human populations are likely decreasing the capacity of coral reefs to grow. Because coral reefs have many organisms living on the seafloor, the researchers underscore the importance of additionally monitoring other coral reef organisms to better understand how interactions might affect coral reef responses to future change. Among these other organisms, turf algae and calcifying algae help paint a better picture of what reefs might look like in the future. Turf algae prevent new corals from settling onto the reef and directly compete against older established corals by forming turf-like mats on the reef bottom.On the other hand, calcifying coralline algae cement the hard-structure of the reef together and help new corals settle onto the reef.

The researchers found that across all of their sites, there was 50% more turf algae and 40% fewer reef-building coralline algae on inhabited island reefs than uninhabited island reefs. Increased turf algae and decreased coralline algae on inhabited island reefs both have the same effect of decreasing the ability of new corals to settle onto the reef. This suggests that local-scale human impacts may reduce the ability of coral populations to recover following coral loss from disturbances such as elevated seawater temperatures and storm activity.

Reducing fishing pressure of herbivorous fishes such as the above parrotfish may help promote coral reef health(6).

What local-scale impacts are causing these changes in coral reef communities on inhabited islands? The researchers suggest that fishing of algae-eating fishes might be causing increases in turf algae on reef environments, but what role do nutrients and other local effects have on coral reef communities? Understanding these questions may help us develop effective policies to increase the overall capacity of coral reefs to continue growing and providing the ecosystem services that so many people depend on.

At the local level, reducing local fishing pressure may help sustain fish populations that eat turf algae to recruit new corals on reefs near human populations. Meanwhile, globally decreasing greenhouse gas emissions will lessen the rise of ocean temperatures that otherwise threaten coral health. If we can change the way we interact with coral reefs and our planet, perhaps we can in turn help to support the very ecosystem services we depend on.

The study by Jennifer Smith and colleagues can be found here:

http://rspb.royalsocietypublishing.org/content/283/1822/20151985.full

Sources:
1.http://www.unep.org/esm/Waterecosystems/Strategies/MarineEcosystemsBranch /MarineEcossstemsBranchUnits/TheCoralReefUnit/CoralReefs-ValuableandVulnerable/tabid/129878/Default.aspx

  1. Gardner, T. A., Côté, I. M., Gill, J. A., Grant, A., & Watkinson, A. R. (2003). Long-term region-wide declines in Caribbean corals. Science, 301(5635), 958-960.
  2. Bruno, J. F., & Selig, E. R. (2007). Regional decline of coral cover in the Indo-Pacific: timing, extent, and subregional comparisons. PloS one, 2(8),
  3. Smith, J. E., Brainard, R., Carter, A., Grillo, S., Edwards, C., Harris, J., … & Vroom, P. S. (2016, January). Re- evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific. In Proc. R. Soc. B (Vol. 283, No. 1822, p. 20151985). The Royal
  4. Image from <http://worldcometomyhome.blogspot.com/2014/09/1239-maldives-vivanta-by-taj-coral-reef.html>.
  5. Image from: Jackson, J., Donovan, M., Cramer, K., & Lam, V. (2014). Status and trends of Caribbean coral reefs: 1970-2012. Global Coral Reef Monitoring

 

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