Tag Archives: Grazers

Herbivore management may be the key to balancing the energetic budget on coral reefs

A new paper published by Emily Kelly and colleagues explains how we can balance the energetic budget on Hawaiian coral reefs through herbivore management and protection. Herbivores on coral reefs play an important role in controlling algal growth, but in systems where density of herbivores is low, algae can grow at a faster rate than they are consumed, resulting in a surplus of algae on the reef.

 

When herbivores are protected on these reefs, it allows the herbivore populations to grow and the rate of algal consumption to catch up to the algal growth rate, thus “balancing the budget.”

Though primary production still outweighs consumption at Kahekili (where this study was conducted in Maui, Hawaii), researchers in this study observed a diminishing margin between algal production and consumption by herbivores over the 5-year period of the study. Herbivores consumed 20.8% of the primary production in 2010, which rose to consumption of 67.0% by 2014.

This increase in consumption is due in part to increases in herbivore population (more mouths on the reef) and in part to greater impact by larger individuals (bigger bites from the reef). This implies that continued protection of herbivores at Kahekili could lead to a balanced energetic budget in the future!

Cover of fleshy algae decreased over the first 5 years of herbivore protection at Kahekili Herbivore Fisheries Management Area

Click here to read more!

Kelly, E. L. A., Y. Eynaud, I. D. Williams, R. T. Sparks, M. L. Dailer, S. A. Sandin, & J. E. Smith. 2017. A budget of algal production and consumption by herbivorous fish in an herbivore fisheries management area, Maui, Hawaii. Ecosphere 8(8):e01899.10.1002/ecs2.1899 [pdf]

Do different species of herbivorous fish have unique grazing roles on coral reefs, or are they all grazing alike?

Coral reefs are home to a large diversity of organisms.  The herbivorous fishes, those fish that eat algae in competition with corals, are no exception to such diversity.  But do the many species of herbivores have unique grazing roles on reefs or are all herbivorous fishes grazing alike?

 

This was the focus of a study recently published in Oecologia by marine ecologist Emily Kelly and colleagues in the Smith and Sandin Labs of the Center for Marine Biodiversity and Conservation at Scripps, along with researchers at the Hawaii Division of Aquatic Resources, and NOAA’s Coral Reef Ecosystem Program in Hawaii.

 

The research team quantified fish foraging behavior, stomach contents, and feeding selectivity to determine the role of individual herbivore species on a reef in Maui, Hawaii.  They found important differences across herbivores in the types of algae different fish consumed and the impact of each bite.

 

“At first pass we often think about all herbivores consuming the same algae in the same way on coral reefs- these fishes are the lawn mowers of reefs, mowing down algae that competes with coral.  But what we find is that in fact these herbivores could be seen as many different types of gardening tools, each with a slightly different function in grazing. Therefore, understanding the role of individual herbivorous fish species is important for knowing how the herbivore community as a whole can influence reef composition and reef health,” says Kelly, lead author of the study.  “This finding is especially important given that we as humans put a lot of pressure on coral reefs, including through overfishing.  Knowing that herbivore species are grazing different algae and in different ways is important for managing a diverse community of herbivores to promote healthy reefs,” she says.

 

Further, the researchers found that using only one method of inquiry into feeding suggested that all fish were grazing similarly on the reef, but using three methods revealed more differences in feeding across fishes.

 

Along with Kelly, Scripps researchers Yoan Eynaud, Samantha Clements, Molly Gleason, and Jennifer Smith were co-authors on the study.

Click to read more!

Investigating functional redundancy versus complementarity in Hawaiian herbivorous coral reef fishes
Kelly, E.L.A., Eynaud, Y., Clements, S.M. et al. Oecologia (2016). doi:10.1007/s00442-016-3724-0

Adventures in Chagos

By Samantha Clements.

This year, during the months of March and April, I conducted coral reef benthic surveys for the Khaled bin Sultan Living Oceans Foundation (KSLOF) in Chagos. Chagos is the largest archipelago in the world and lies within the British Indian Ocean Territory. The islands of the archipelago are very far from any continents and have been uninhabited and protected since the 1970’s, and therefore provide a unique environment, free of local human impacts, to study coral reefs and the faunal communities they support.

Chagos is located in the middle of the Indian Ocean, just south of the Maldives.

Chagos is located in the middle of the Indian Ocean, just south of the Maldives.

Coconut palms, hermit crabs, and birds dominate the uninhabited islands of Chagos.

Coconut palms, hermit crabs, and birds dominate the uninhabited islands of Chagos.

Coconut palms, hermit crabs, and birds dominate the uninhabited islands of Chagos.

Uninhabited island in Chagos.

Coconut palms, hermit crabs, and birds dominate the uninhabited islands of Chagos.

Coconut palms, hermit crabs, and birds dominate the uninhabited islands of Chagos.

Occasionally, moray eels will come into the tide pools during the day to hunt for crabs.

Occasionally, moray eels will come into the tide pools during the day to hunt for crabs.

Since Chagos is protected from fishing, fish from all trophic levels, from herbivores to planktivores and predators, are able to thrive in large numbers. Additionally, they often grow to be much larger than similar species in areas where fishing is allowed.

A school of bait fish cruises over the reef.

A school of bait fish cruises over the reef.

Large schools of fusiliers often surround divers conducting surveys. Here you can see an aggregation of snappers hovering in the background.

Large schools of fusiliers often surround divers conducting surveys. Here you can see an aggregation of snappers hovering in the background.

Large schools of herbivores, such as these surgeonfish, cruise the reef consuming turf algae.

Large schools of herbivores, such as these surgeonfish, cruise the reef consuming turf algae.

Very small glass fish will school in large numbers and seek refuge beneath ledges on walls or crevices in Porites bommies.

Very small glass fish will school in large numbers and seek refuge beneath ledges on walls or crevices in Porites bommies.

Red snappers (Lutjanus bohar), midnight snappers (Macolor macularis), and black snappers (Macolor niger) often travel in loose groups, searching for food.

Red snappers (Lutjanus bohar), midnight snappers (Macolor macularis), and black snappers (Macolor niger) often travel in loose groups, searching for food.

A school of yellowspot trevally pass through my transect.

A school of yellowspot trevally pass through my transect.

The steephead snapper (Lutjanus gibbus) is often found in large schools near the benthos.

The steephead snapper (Lutjanus gibbus) is often found in large schools near the benthos.

Grey reef sharks patrol the reef during a dusky dive.

Grey reef sharks patrol the reef during a dusky dive.

Tawny nurse sharks are extremely common in Chagos. They have small eyes and poor eyesight and will often come very close to divers to get a better look

Tawny nurse sharks are extremely common in Chagos. They have small eyes and poor eyesight and will often come very close to divers to get a better look

In addition to fish, many invertebrates thrive in this refuge from fishing, including the ever-popular day octopus (Octopus cyanea).

In addition to fish, many invertebrates thrive in this refuge from fishing, including the ever-popular day octopus (Octopus cyanea).

In a rare moment, an painted rock lobster (Panulirus versicolor) comes out of hiding.

In a rare moment, an painted rock lobster (Panulirus versicolor) comes out of hiding.

This hairy yellow hermit crab (Aniculus maximus) was carrying a shell that was about the same size as an American football!

This hairy yellow hermit crab (Aniculus maximus) was carrying a shell that was about the same size as an American football!

Since Chagos is uninhabited, the corals that build the reefs are free from local anthropogenic stressors, such as pollution, sedimentation, and other direct interaction. The coral cover is relatively high on most reefs and often dominated by large tables of the genus Acropora.

Large table Acropora.

Large Acropora table

Despite being free from local anthropogenic stressors, these corals are still susceptible to global stressors, such as ocean acidification and global warming. During our time in Chagos, our science team witnessed a coral bleaching event, the first reported in the Indian Ocean this year. For more information about the bleaching event, check out an interview with KSLOF’s chief scientist, Dr. Andrew Bruckner: http://www.cbsnews.com/news/indian-ocean-reefs-hit-by-coral-bleaching/.

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Though bleaching can be detrimental to coral reefs if the event lasts for a long period of time, there is hope for recovery in Chagos, as recruitment of new corals is high in many places where past episodes of bleaching or disease have wiped out coral in the recent past.

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Overall, the KSLOF Chagos expedition was an incredible adventure and a wonderful chance to see how a coral reef lives and functions without the direct interference of local human populations.

The reef from above, with a great view of the new corals growing

The reef from above, with a great view of the new corals growing

Baby coral recruits can be seen growing on what used to be an Acropora table; the next generation!

Baby coral recruits can be seen growing on what used to be an Acropora table; the next generation!

My first summer in the field – by Gideon Butler

My first summer in the field

 

When I tell people that I spent six weeks on Maui this summer, nobody seems to believe that it wasn’t a vacation. I tell them that I was working from dawn to dark every day and that my body was covered in scrapes and bruises by the end, but all they hear is, “I was living in paradise and scuba diving every day, and I got a great tan!” To be honest, I can’t really blame them. The fact that coral reef ecology means scuba diving in tropical paradise is one of the primary reasons I chose the field. Even though I was utterly exhausted by the end, and each day brought new challenges, it was the most exciting and fulfilling work I’ve ever done.

The goal of my first field season was to help PhD student Levi Lewis pull out an experiment that had been on the reef for 3 years. I got to go because he needed a dive buddy and extra hand. Levi’s main experiment looked at the health of reefs by placing PVC tiles called Calcification Accretion Units (CAU) on the reef and seeing what grew on them. Half of these CAUs had plastic mesh on them to prevent herbivores from grazing on them, and the first phase of our work was cleaning and repairing these cages for the final month they would be on the reef. This is when I learned of the sacred place zip-ties have in the hearts of scientists. Over the course of the trip we used over 1000 zip ties, and using them underwater never got easier. Imagine threading a needle in a hurricane. I would almost have a tie zipped but then the surge would toss me 15 feet away across the reef. Luckily, surge works both ways and I would eventually get carried back to try again. On some really rough days I learned to just wedge myself into the reef and hope there wasn’t an eel in the hole I was sticking my hand into.

 

That’s me, “doing work.”  Notice the zip ties?

That’s me, “doing work.” Notice the zip ties?

 

We also did some really fun and totally not frightening experiments with urchins. For those who don’t know, Hawaii has a few species of urchin that have heavily toxic spines. While those guys were frightening at first, they were mostly a non-issue if you handled them carefully and kept a lookout while diving (I learned that the hard way after I accidentally drop-kicked one of our research specimens with my fin—sorry, buddy!). The really terrifying urchins are the completely harmless Tripneustes gratilla. Why are they so scary if they’re harmless? Well, these lovely little fellas have a fascinating survival strategy. T. gratilla doesn’t have toxic spines and it can’t run away, so when an individual is threatened it ensures the survival of its species by releasing sperm all over the reef (it’s possible that the mechanism is meant to gross out predators, but I’m pretty sure that only works against humans). Unfortunately for us, T. gratilla regards pretty much everything as a threat, including being transported in a cooler in our science van. We would try not to make hard stops because the lid didn’t seal too well, but after a few trips I think we were both too embarrassed to offer anyone else a ride. It’s ok though, we’re biologists, right?

 

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The evil T. gratilla, being incubated for metabolism measurements (left). The cages we stuck them in to conduct grazing assays (right). The purpose of the assay was to see what algae each species of urchins prefers to eat, and how much. The metabolism data can give clues as to how active the urchins are (and how much food they would need). Urchins are an important player on Hawaiian reefs because they trim back algae that would otherwise smother coral.

  One of the real joys of the trip was all the practical problem solving involved. There is no Sears for science, so we had to design and build all of our experiment set ups. For marine ecologists, this means spending some quality time with PVC and (predictably) zip ties. Beyond building the tools we also had to design the experiments themselves to fall within the limitations of our equipment and still be scientifically rigorous. Of course, no matter how thorough you are in the planning phase, when go -time comes there will always be some small problem. It sounds perverse, but I came to enjoy it when these problems happened because it meant there was one more puzzle to solve. Maybe it helped that it wasn’t my PhD dissertation that hinged on these experiments; it was probably a lot more nerve-wracking for Levi.

Taking metabolism measurements

Taking metabolism measurements

A big pile of CAUs

A big pile of CAUs

In all, I am immensely grateful for this opportunity. I learned so much about science and field work, I got to see some amazing critters and sights, and I met an awesome group of people. Big thanks to Levi and the Smith Lab, as well as the Maui ohana I was lucky enough to become part of.

Doing the a’a dance.  Lava rock hurts!

Doing the a’a dance. Lava rock hurts!

The crew: Levi, me, and Susan Kram, a fellow Smith Lab member.

The crew: Levi, me, and Susan Kram, a fellow Smith Lab member.

Go-time.

Go-time.

We got to dive in the shark tank at Maui Ocean Center.  Yes, that’s a tiger shark.

We got to dive in the shark tank at Maui Ocean Center. Yes, that’s a tiger shark.

Smith Lab’s Clint Edwards Publishes New Paper!

Smith Lab’s Clinton Edwards is now a proud author of the Proceedings of the Royal Society Biology! 

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His Master’s thesis: Global assessment of the status of coral reef herbivorous fishes: evidence for fishing effects examines the global status of herbivorous fish and how their presence affects the dynamics of the marine ecosystem.

 Cover3_EKAbstract: Coral reefs are among the most threatened ecosystems on the planet due to overfishing, pollution, warming and ocean acidification. Coral reef herbivores–the “lawn mowers” of the landscape are widely known for their importance in maintaining reef health and assisting in recovery following disturbances because they eat seaweeds that compete with fragile corals for space. We conducted the first global assessment of the status of these important fish and found that herbivore mass is reduced by > 50% in areas accessible to fishing in comparison to unfished locations. Further, we show that fishing affects the structure of the herbivore community in a way that may actually harm reefs. We recommend greater global protection of this highly important group of reef fishes.

Smith Lab Collects Data From Year Long Ocean Acidification Experiment

The multipurpose sombrero - it shades-out unwanted glare and makes taking photos of tiles way more fun

The multipurpose sombrero – it shades-out unwanted glare and makes taking photos of tiles way more fun

A crew of lab members worked together this week to collect data for Emily Donham’s ocean acidification experiment examining the effects of declining pH and grazing on local communities of benthic organisms.  This project is a part of the California Sea Grant project run through the Smith Lab and Scott Hamilton’s lab at Moss Landing Marine Laboratories to examine the effects of ocean acidification on local seaweeds and invertebrates in California.
Blank tiles are definitely busy with life after 12 months by the kelp forests

Blank tiles are definitely busy with marine  life after 12 months underwater by the kelp forests

The work in the lab over the last couple of days consisted of weighing the tiles to determine growth changes over the last month in the different pH and grazing treatments, removing baby kelps and other algae from the tiles, and preparing for future examinations of the diversity of the cool seaweeds and invertebrates that have been living on the tiles.  The team in the lab put in a lot of hours but had a great time seeing the end result of over a year of work!
Written by: Emily Kelly
Photos Credit: Emily Kelly

Research Adventures in Maui

Our “urchin prison” setup

We’re back in Maui to check on experiments and collect data. This round, fellow labmate Clint Edwards  has joined me & it’s been a great adventure.  We’ve been working hard and playing hard.

We have an in situ (in the field) experiment that explore the rates and preferences of herbivorous sea urchins in Hawaii.

 

 

Our smorgasbord of algae

Why you ask? Urchins are important consumers of algae on tropical coral reefs.  Without urchins, algae may grow unchecked and smother the corals that build reef environments; and that’d be bad. We know urchins are important in general, but there are 6 common species of herbivorous urchins in Maui’s reefs and we’re trying to figure out whether they all serve the same functions or perform complementary functions in reef systems.

So, we collect them, use grazing assays or “urchin prisons” as Clint calls them, and provide a smorgasbord of algae to observe what and how fast they eat. Pretty simple concept, but not so easy to to execute as you can see.

 We also ventured out with a couple of cohorts, Don & Mark, to use UV lights to capture Fluoresceine die oozing from some previously labeled wastewater seeps.  We weren’t sure what we would find; and we were shocked to find an amazing psychedelic light show on the new moon.  In addition we were surrounded by a wonderful array of wildlife; most notably, a moray eel tearing into the flesh of a freshly-captured brown tang.

               

For the Maui nightlife, one might expect liquor, dancing, feasting, & light shows.  Well, we found liquid, dancing, feasting & light shows; albeit, all submarine.

Four Days of Data and Chicken Wire

Emily does some data collection on the reef

I just completed a whirlwind four-day research trip to collect data and put in new hardware for an experiment that’s been on-going off West Maui for the last two years.  Check out the photos taken during data collection and after setting up the new shiny green chicken wire cages that are at Airport Beach / Kahekili Herbivore Fisheries Management Area.  You can find them on the reef in 25 feet of water and the different cage designs reflect the different herbivores (or seaweed-eaters) that can graze inside during this experiment.  Some of the cages allow herbivorous fish to graze, some allow urchins, some allow both, and some allow neither.

Shiny new green chicken wire cages

The goal of the Herbivore Fisheries Management Area (put into place by the Hawaii Division of Aquatic Resources in 2009 to protect herbivores from fishing) is to see more herbivores on the reef so that they will reduce algae cover and increase coral cover.  With a little help from a couple rolls of chicken wire, the data from this experiment tell us how these different algae-grazers are affecting the coral reef community.

Mahalo nui loa to friend of the lab Mark Miller for generously volunteering his time as a field assistant this week!

Notes from the Field: Hawaii


Emily Kelly (left) scraping turf algae with Kerrie Krosky of UH Hilo. credit: Rebecca Most

Emily Kelly has hopped over from Maui to the Big Island of Hawaii for the month of August to work on a project in collaboration with the University of Hawaii, Hilo and the US National Park Service at Kaloko-Honokohau National Historical Park.  The research team is investigating how fast fish eat algae and how fast algae grows in areas of high and low nutrients on the reef.  The team is looking at grazing on and growth of macroalgae (the bigger seaweed you see waving around on the reef) and turf algae (the brown fuzzy carpet that covers dead coral or rocks) and has set up the experiment to allow for no grazing (cage), grazing by only fish (fence to keep urchins out), grazing by only urchins (canopy to keep fish out), and grazing by both (open areas).  Over time, the team will measure what changes they see in the amount of algae in each plot.  Two weeks into the project and with a team of 6 divers, the turf experiment is installed and running!  More updates to come as the team sees what changes may occur over the course of the experiment!

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