Coral Reef Ecology

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Smith Lab at Scripps Institution of Oceanography
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The Sargassum horneri Invasion at Catalina Island

Mon, 03/16/2015 - 3:54pm

By Niko Kaplanis

In April of 2006, during a survey for the Channel Islands Research Program (CIRP), renowned scientists Kathy Ann Miller and John Engle discovered an established population of the invasive alga Sargassum horneri near the Wrigley Marine Science Center at Santa Catalina Island. This was the first instance of the species being documented at one of California’s offshore islands. Reconnaissance surveys spurred by this initial discovery then revealed established populations at San Clemente Island in May of 2007, and subsequently, populations have been discovered throughout the rest of the Channel Island chain. S. horneri has now become very well established at Catalina, expanding its range to occupy the entire leeward (north) side of the island, as well as some locations on the more exposed and native-algal dominated south shore, and flourishing through multiple generations.

A thick wall of Sargassum horneri, some plants reaching more than 2 m in length

A thick wall of Sargassum horneri, some plants reaching more than 2 m in length

In the past month I visited Catalina to assist with ongoing research on the S. horneri invasion at Catalina lead by Lindsay Marks, a PhD student at UC Santa Barbara. Lindsay has undertaken a heroic effort — conducting monthly surveys at sites throughout the leeward side of the island and running multiple removal experiments—with the goal of tracking the invasion and providing detailed information on the ecology, life history, reproductive capacity, and impacts of this species.

 Sampling a quadrat.

Sampling a quadrat.

The visit provided mind-blowing insight into how dominant S. horneri can become at invasion locations. Each of the nine sites we dove was entirely dominated by thickets of the invasive alga growing in incredible densities extending from the shallow sub-tidal down to depths of 60 or 80 ft. Both the densities and abundances observed at Catalina far exceed those of San Diego, which may be a result of the longer invasion history at the island, a difference in the invasion environment, or some other as-of-yet unknown factor. The island is also starkly devoid of native Macrocystis pyrifera, the giant kelp that typically forms kelp forests along the island’s coast. While this phenomenon can’t be directly attributed to the Sargassum invasion – other factors such as persistently warm water ocean temperatures in the area are also likely in play—it is reasonable to assume that the invasion is contributing to it.

The thicket from above.

The thicket from above.

The thicket from below.

The thicket from below.

The island provides an exciting opportunity to study the invasion, and I am grateful to Lindsay Marks for inviting me to assist with her research. Whether the population will remain persistent in the current densities and spatial abundances, and whether an invasion on the scale observed at Catalina will occur elsewhere is unclear, but her work is sure to provide some insight into these questions.

One of the few sites still dominate by native macroalgae.

One of the few sites still dominate by native macroalgae.

 

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The Faces and Functions of Algae on the Reef

Fri, 02/27/2015 - 12:30pm

By Samantha Clements

Algae, often referred to as “seaweed,” are underwater “plants” that, unlike land plants, lack a vascular system. Algae live underwater and obtain water, nutrients, and sunlight directly from the environment. Because algae don’t need a vascular system, they come in many shapes and sizes and may look very different from land plants. Some algae, such as Ventricaria (“Sailor’s Eyeball”), can exist as a single cell that can grow to be larger than 10 cm in diameter!

A large Ventricaria cell (~10cm) sits nested within a Pachyseris colony

A large Ventricaria cell (~10cm) sits nested within a Pachyseris colony

A large Ventricaria cell (~10cm)

Benthic scientist, Samantha Clements, takes a selfie in the reflective surface of a large Ventricaria specimen (~8cm)

For many people, algae on coral reefs are synonymous with environmental decline. Often the presence of algae is associated with terms such as “harmful algal bloom” and “eutrophication,” which imply the negative effects of too much algae in an environment. It’s true that under some conditions algae can grow uncontrolled and become a problem for reef-building corals, as they compete for both space and sunlight on the reef. One thing that can lead to an overgrowth of algae is an excess of nutrients in the water, either naturally from upwelling of nearby nutrient-rich waters, or from anthropogenic sources, such as agricultural runoff from land. These nutrients act as fertilizers for plants on the reef, allowing them to grow very quickly. Another thing that can cause algae to grow uncontrolled on a reef is release from the pressure of herbivory. This is often caused by overfishing in communities where reef fish and other herbivores, such as sea urchins, are consumed as an important source of dietary protein.
Algae, however, are very important to a healthy coral reef ecosystem under natural conditions. They provide important habitat for many small creatures and act as the base of the food chain that fuels the community of coral reef critters. Algae come in all shapes, sizes, colors, and textures and have about as many functions as faces! Halimeda, a bright green, segmented alga, has branches that contain calcium carbonate—these calcified segments become sand on the reef when they fall off and crumble. Crustose coralline algae (CCA) is a type of red, calcified algae that grows as a pink crust on the reef and is often referred to as the “cement of the reef” because it grows over loose bits of reef and essentially glues them together. It also provides a very important substrate for coral larvae to settle on. Turf is an assemblage of small, primarily filamentous, algae that grow as a dense mat. Turf is an important food source for herbivorous fishes and sea urchins, and fills most of the space on the reef where corals aren’t already growing. Many algae add to the natural beauty of the reef, such as the bright red blades of Peyssonnelia growing in shady overhangs, and the curly-cues of Padina growing between corals wherever there’s space.

This Phyllidia nudibranch makes its way through a dense bed of Halimeda

This Phyllidia nudibranch makes its way through a dense bed of Halimeda

Padina grows in beautiful curls that fill in the space between fingers of branching Porites

Padina grows in beautiful curls that fill in the space between fingers of branching Porites

Cyanobacteria is a type of algae that occurs naturally on reefs, but can become problematic (and often scary looking!) in large quantities

Cyanobacteria is a type of algae that occurs naturally on reefs, but can become problematic (and often scary looking!) in large quantities

In the Smith Lab, we often collect algae to make algal pressings for our herbarium, a collection of pressed and dried algae with information about the date and location each specimen is found. Algal pressings can be very beautiful, often resembling intricate watercolor paintings. They provide important information about which algae grow in various environments and act as a catalog of diversity for the places we’ve been.
While algae have the potential to become a nuisance, they are always part of a healthy reef community. There are natural fluctuations in the abundance of algae found on a reef, but the most important things we can do to ensure algae don’t get out of control are to protect our reefs from overfishing and pollution. The rest is up to nature!

Benthic scientist, Samantha Clements, photographs an algal specimen for collection

Benthic scientist, Samantha Clements, photographs an algal specimen for collection

A gelatinous red alga collected for identification

A gelatinous red alga collected for identification

Samantha organizes algal pressings from the Global Reef Expedition’s Herbarium

Samantha organizes algal pressings from the Global Reef Expedition’s Herbarium

Herbarium pressing of Caulerpa

Herbarium pressing of Caulerpa

Herbarium pressing of Padina

Herbarium pressing of Padina

Herbarium pressing of Portieria

Herbarium pressing of Portieria

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Adventure in Puerto Morelos, Mexico

Mon, 02/09/2015 - 10:53am
By Mike Fox

 

Last week I traveled south to Puerto Morelos, Mexico to participate in an intensive 3-week course about Light and Photosynthesis on Coral Reefs. Hosted by Dr. Roberto Iglesias-Prieto and the National Autonomous University of Mexico (UNAM), this class provides an incredible opportunity to study the photosynthetic physiology of corals, algae, and seagrasses. Our course is taught at the UNAM Institute of Marine Science and Limnology, located on the shores of the second largest barrier reef system in the world, the Mesoamerican reef.

The UNAM campus. Puerto Morelos, Mexico.

The UNAM campus. Puerto Morelos, Mexico.

I first learned about coral reefs while completing my undergraduate degree. During that time I spent almost two years living and working in the Caribbean. The turquoise waters and white sandy beaches were easy to fall in love with but it was the corals and the algae I learned about there that inspired my career as a marine scientist. I still think about those reefs and their familiar species of coral so I was very excited to return to the Caribbean after five years away.

Imagine my surprise when I first went out to the beach and found that it was practically buried in seaweed!! There are plenty of stories about the coral reefs in the Caribbean being completely overgrown by algae but even the worst reports hadn’t prepared me for this. However, after a bit of research, I am happy to report that this seaweed is not coming from the local reef. The brown alga that is covering the beaches is known as Sargassum natans, and shockingly it has traveled from hundreds of miles away!

The amount of Sargassum that has washed ashore over the past week is truly amazing. It also makes our walk to school a little more difficult on the narrow sections of the beach!

The amount of Sargassum that has washed ashore over the past week is truly amazing. It also makes our walk to school a little more difficult on the narrow sections of the beach!

Globally, 2014 was the hottest year on record. Unfortunately, in the Florida Keys these warm temperatures caused considerable coral bleaching. Although warm water temperatures can be harmful to corals, they are not necessarily bad for other organisms. While the corals in the Keys were bleaching, the Sargassum in the nearby Sargasso Sea was thriving. It turns out that the extreme productivity of the Sargassum population in the Sargasso Sea this year has caused far more algal biomass to wash ashore on beaches in the Caribbean than usual. During the summer months, wind and current patterns typically deposit some of this floating forest along the beaches of the northern Caribbean Islands. This year, however, extensive deposits of Sargassum have been reported as far south as Trinidad and as far east as Africa! So far, no one that I have spoken to here in Puerto Morelos can ever remember Sargassum deposits of this magnitude along the Mesoamerican reef.

With more Sargassum coming in each day, the beaches here look more like our beaches at home in California where we sometimes find them buried under kelp after big swell events. Although one thing is for sure, with themassive amount of Sargassum that has been washing ashore across the entire Caribbean region, the primary productivity of the Sargasso Sea is nothing short of awe-inspiring. Most of the resorts here are frantically trying to remove the seaweed from the beaches but from my point of view it serves as an impressive reminder of the wonders of nature. Thinking about how connected our marine ecosystems are, I can’t help but wonder if there will be any lasting impacts on the seagrass and reef systems just offshore. I guess we will just have to wait and see…

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Many tourists come to the Mexican Yucatan to enjoy the miles of white sand beaches so the resorts are fighting a losing battle to keep their beaches clear of the seaweed.

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Pangas in the local harbor floating on a huge mass of Sargassum that washed ashore after a small storm.

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Northern Channel Islands Algae Collection Trip

Thu, 01/22/2015 - 1:10pm

By Niko Kaplanis

In a recent collaboration with the Paul Jensen Lab here at Scripps, I travelled to the Northern Channel Islands to assist with collections for their research. The Jensen lab focuses on microbial distributions and interactions with marine plants and invertebrates as well as sequence-based approaches to the discovery of natural products from marine microbes. Our objective for the trip was to collect and identify as many algae and invertebrates as possible. The microbial communities growing in association with these samples were then to be processed and their genes searched for sequences which encode for the production of novel compounds.

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Getting ready for a dive

My experience with local marine algal species — accrued from field work for my invasive algal project and through serving as a TA for Jen’s phycology lab– earned me the title of seaweed identification expert for the trip, and I was put in charge of collecting and identifying algae. The recent discovery of invasive Sargassum horneri on Santa Cruz Island in 2012 provided a second personal objective for the trip — to add our collection sites to the list of locations where invasive algae had been searched for in the islands. We were specifically looking for this invasive alga also because a recently collected sample of this species from Catalina turned up a genetic sequence which encoded for the production of polybrominated diphenyl ethers or PBDEs. These chemical compounds are typically anthropogenically produced for use in industrial flame retardants, but this discovery suggested that microbial communities potentially growing specifically with this species could be a natural source. These compounds are known to bioaccumulate in both humans and marine mammals and to cause adverse health effects, specifically reducing fertility and having hormone-disrupting effects on estrogen and thyroid hormones. As such, identifying natural sources of these compounds is an active and important area of research.

Our trip began in Santa Barbara Harbor where we loaded our gear onto the Conception, a dive boat operated by the dive charter company Truth Aquatics. Motoring overnight through the rough seas of the Santa Barbara Channel put us at San Miguel Island, the westernmost island in the chain. Through the course of the next four days we would travel east, diving the leeward side of every island in the chain, ending in Anacapa Island.

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The wise and ever pensive Dr. Paul Jensen

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Anacapa Island and the eastern-most point on the Northern Channel Islands

The diving in the Northern Channel Islands proved to be remarkable, with many marine reserves harboring healthy kelp forests home to a diverse array of invertebrate, fish, and algal species. We were also blessed with abnormally warm water and calm seas, producing a feeling that we were diving an area more akin to the tropics than the California coast. Collections went smoothly, and we were able to collect and identify roughly a dozen unique algae at each site. Interestingly, Sargassum horneri only occurred at Anacapa Island, an area where it had not been previously documented. Whether these samples will produce sequences for novel compounds is not yet known, though the processing of these samples will soon give us an answer. Contributing to this project was a blessing, and I feel very lucky to have been a part of it, and to have been able to nurture a collaboration within our diverse institution.

 

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Coral Reef Ecosystems: Human Impacts, Pristine Reefs & Conservation Strategies

Tue, 01/20/2015 - 8:30am

Jeffery B. Graham Perspectives on Ocean Science Lecture Series presents Dr. Jenner Smith

Check out Dr. Smith’s presentation here!  http://www.ucsd.tv/search-details.aspx?showID=28675

Understanding how humans impact marine ecosystems is crucial to developing successful conservation strategies that protect the health of our ocean.  Discover how Scripps marine ecologist Jennifer Smith and her team are conducting research relevant to solving human-induced problems in environments ranging from coral reefs to the waters off our shores.

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The CAU Slaughterhouse Chronicles

Fri, 01/16/2015 - 12:43pm

By Adi Khen

As a first-time volunteer at the Smith lab, I got to be involved in one of the most exciting parts of data processing: drying, weighing, acidifying and, basically, slaughtering CAUs!

Let me explain… CAU stands for Calcification Accretion Unit, or in this case a set of two stacked PVC tiles that are used to measure carbonate accretion and successional development on coral reefs. Three years ago, PhD student Levi Lewis, installed 160 CAUs across 8 different reef sites on leeward Maui. Half of the CAUs at each site were “caged,” or enclosed in a stainless steel frame to prevent herbivory, while the rest were “uncaged.” Environmental characteristics at each site, such as temperature, light, pH, salinity, and sedimentation were also measured. By installing and later removing CAUs, researchers are able to sample reef communities without causing extensive damage to the reef.

This past summer, Levi removed all of his CAUs from the reef and brought them back to the lab. The macroalgae that had grown on the tiles, as well as the sediments that had collected on the tiles and the cryptic invertebrates that found shelter among them, were put into separate bags and frozen for future processing. All tiles were photographed for image analysis and then, our slaughterhouse was open for business.

Innocent CAUs laying out, completely unaware of what’s about to hit them

Innocent CAUs laying out, completely unaware of what’s about to hit them

After pouring 5% HCl on the CAUs, their carbonate instantly started dissolving

After pouring 5% HCl on the CAUs, their carbonate instantly started dissolving

About a day later, bare CAUs sitting on top of a container of their own fleshy (macroalgae and acid)

About a day later, bare CAUs sitting on top of a container of their own fleshy (macroalgae and acid)

We dried the tiles in a drying oven, weighed them, let them soak in acid until all of their calcified matter dissolved, scraped them, and then dried and weighed them again (the difference between the initial and final tile masses would then represent the amount of carbonate accretion). We also filtered out the remaining fleshy matter from each tile, dried it, and weighed it to find the amount of fleshy biomass on each tile. After several months of the lab reeking of acid, we were left with about 300 clean PVC tiles, and we moved onto our next subjects: the macroalgae and invertebrates.

Macroalgae samples were also collected from the tiles in Maui, and froze for later analysis. Well, we thawed them, sorted each CAU’s algae by type or species, dried them, and then weighed them individually. We could then compare not only the difference in macroalgal cover between sites, but also the density and diversity of the macroalgal communities.

Microscope view of filaments of Dasya algae that had grown on one of the CAUs

Microscope view of filaments of Dasya algae that had grown on one of the CAUs

Microscope view of the growing tip of another thin branching alga

Microscope view of the growing tip of another thin branching alga

Microscope view of a cystocarp on Halichrysis, a leafy red alga

Microscope view of a cystocarp on Halichrysis, a leafy red alga

As for the frozen invertebrates, we thawed them, too, sieved them into different size categories, and then identified and quantified the critters from each CAU. This would help us determine the diversity, abundance, and potential importance of cryptic invertebrates in benthic communities.

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Inverted microscope view of the same invertebrate (which I like to call, “inverted invert”)

Inverted microscope view of the same invertebrate (which I like to call, “inverted invert”)

My sketch of the “inverted invert,” now hanging by the lab’s microscope

My sketch of the “inverted invert,” now hanging by the lab’s microscope

These days, though our slaughterhouse is no longer in session, we’re getting ready to photoanalyze the surfaces of each of the CAUs to get a better picture of benthic community development on Maui’s reefs.

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Influential conservation papers of 2014 – featuring Smith Lab’s Clinton Edwards!

Thu, 01/15/2015 - 5:14pm

Clint Edwards, et al.  publication, Global assessment of the status of coral reef herbivorous fishes: evidence for fishing effects, has been selected as one of the most influential conservation papers of 2014!!  Congratulations Clint & Smith Lab!!!

http://conservationbytes.com/2014/12/22/influential-conservation-papers-of-2014/

Congratulations to Clint for completing his Master's!

Congratulations to Clint and Jennifer!

 

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