Rock Island Paradise

Mushroom-shaped rock due to erosion
Photo credit: H. Rivera

I've mentioned Palau's Rock Islands quite a few times now - how unique they are in that they harbor amazing reefs despite having low pH conditions and hotter water temperatures than Palau's outer reefs, both conditions that corals usually stay away from. I'd like to give you a better sense now of just what it's like to visit these Rock Island bays and spend the day diving or sampling, surrounded by the lush vegetation as we drop Niskin after Niskin over the side of the boat to take our water samples.

Hannah peaks up from
a swim
Photo credit: H. Rivera

Taoch Bay, Palau
Photo credit: H. Rivera

The Rock Islands are undeniably the most beautiful place I've been to so far. Driving through the meandering channels, making our ways through the plethora of mushroom-shaped islands, each a vivid, deep green from the trees, shrubs, and palm fronds that overwhelm its sheer limestone cliffs. We can see flocks of Tropics birds and Knots that fly overhead finding shelter in the vegetation as they roam the waters for fresh catch. The sounds of monkeys echo through the bays, along with the screeches of fruit bats. The waters are usually a bright turquoise near the shallows, clear and bright during our recently sunny dives. Most of our dives sites are smalls bays in which the corals grow mainly around the walls of the enclosure where the water is shallowest and they can get the most light, although the proximity to the surface is somewhat offset by the shading they receive from the islands. The depth drops off rather quickly toward the center of the embayments, sometimes reaching 50 or 60 feet (15-18 meters). The coral community is bright and colorful, harboring plenty fish that come to grow up closer to shore, where they are better protected.  

The work our lab has conducted in these islands over the last several years has helped us better understand their importance. We hope to uncover more of their secrets when we return to analyze all the samples collected on our current expedition.

-Hanny Rivera

Close Encounters of a Finned Kind

Dolphins race our boat
Captured by P. Lohmann

Fishing is banned in Marine Protected Areas (MPAs), allowing fish populations to recover from previous exploits and providing a shelter in which populations outside of the protected area can be spared from pursuit. As a result fish diversity and abundance is usually greater within MPAs than outside them. During our stop in Kayangel, the northernmost of Palau's states we explored Kayangel's MPA - we only conducted surveys here as taking of coral samples is prohibited. The benefit of its protected area status was evident right away. 

Octopus tries to blend in with its
surroundings
Spotted by M. Kaplan

On our boat ride through the MPA we were greeted by large pod of dolphins, with two groups dashing and jumping off the bow of both our boats. Once we were in the water, our first sight was a school of four white-tip reef sharks, who were slowly roaming the edge of the reef. Later on in our dive we saw two others sleeping under a large coral boulder.  Along with several moray eels, and vast diversity of angelfish, parrotfish, damselfish, groupers, snappers, the fish wildlife was spectacular. The invertebrate populations were likewise robust, we discovered an octopus and wide assortment of snails, hermit crabs, ovulids, sea cucumbers and the likes. 

White-tip shark explores the reef
Photo credit: M. Kaplan 

It was quite evident from our dives that even a region that is already as naturally rich and diverse in fish, coral, and invertebrate populations as Palau, can benefit tremendously from MPAs. Palau will soon be declaring its entire exclusive economic zone as a marine sanctuary, meaning it will issue no commercial fishing licenses and only local subsistence fishing will be allowed in designated areas. The result of this measure will undoubtedly be an even healthier and thriving marine habitat. I look forward to returning to Palau's waters severals years after the changes come into effect and seeing their impact. In the meantime, I'll leave with a few more gorgeous pictures that showcase our adventures.

-Hanny Rivera 

Curious squirrel-eye fish says hello
Photo credit: M. Kaplan

Variety of fish over the reef crest
Photo credit: M. Kaplan

Green moray eel wakes up from a nap
Photo credit: M. Kaplan

School of permit fish
Photo credit: M. Kaplan

Sampling the Deep Blue Sea

Kathryn draws water from
 the Niskin bottle to
measure nutrients
Photo credit: H. Rivera 

Winch used to lower and
raise Niskin for
deeper sample sites
Photo credit: H. Rivera 

One of our aims for this current expedition is to characterize and understand the water chemistry and nutrient profiles of the water around the Palauan archipelago. Water samples are taken using a Niskin bottle, a large bottle that can be lowered to a particular depth and then triggered to closed, by sending a messenger weight to trip the latch. This seals the bottle collecting the water of that depth. We can then bring the bottle back up and process the collected water for our analysis of interest. 

Max sends the messenger
weight to trip the bottle
Photo credit: H. Rivera

During our cruise we've collected water samples over each of our coral reef sites as well as several off shore sites. This allows us to see how the water changes as it comes from the open ocean over Palau's lagoon and into the reef's closer to land. We can track declines in pH, changes in salinity, temperature, and nutrient levels as the water flows over the reefs and is changed by metabolic activity, wave actions and other perturbations. 

For our deep offshore sites we had a handy winch to help up raise and lower the bottle. Our sampling went very smoothing and we had gorgeous weather, during our very last deployment though we had a minor malfunction and ended up hauling up 150 meters of line with ~30 lbs weight by hand... that gave Pat and Max quite the morning workout! They recovered our bottled though and we had our last samples :)

-Hanny Rivera

Helen Island, Population: 3

Welcome Sign at Helen

Photo credit: M. Kaplan

Turtle Nursery at Helen Reef
Photo credit: M. Kaplan

During our stay at Helen Reef, we were able to make a quick pit stop on the Helen island the only land for miles and miles. The island is inhabited only by three park rangers who patrol the area against illegal fishing and poaching and monitor the reefs and protect wildlife. For instance, they gather new turtle hatchling and allow them to grow up under protection before re-releasing them into the wild due to otherwise high levels of mortality and dwindling turtle populations.

The island is small and absolutely beautiful, crystal clear turquoise waters surround the shallow sandy banks that surround it and white sandy beaches make up its entire coastline. A handful of coconut palms line the horizon, along with a several small trees and few shrubs and grasses. Its most noticeable feature are the thousands of birds flying overheard, circling and cawing, probably a bit agitated to see so many humans on the island. They come there to nest and rest, and nearly every branch on every available tree is overtaken by birds, with signs of nests visible anywhere the branches meet and create a secure enough surface.

Bird nest
Photo credit: H. Rivera

Birds of Helen Island
Photo credit: H. Rivera

The rangers live in a small house and keep their supplies, water, fuel, and other resources under sheltered cover. There is no electricity on the island, nor refrigeration. The rangers usually stay on the island for several months at a time, often years. Transit to and from the mainland is scarce, not many boats pass this way. It's certainly a different way of life, but without a doubt a beautiful and unique place.            

- Hanny Rivera

Helen Reef

Satellite View of Helen Reef

We just completed our work at Helen Reef, the southernmost of Palau's reefs. Helen Reef is rather isolated from any large mainland, inside the atoll is a small island less that half a square kilometer in size, uninhabited, except for three rangers who patrol the reef's marine protected area. The closest other island is Tobi Island, which has a population of less than 100.

The coral reefs at Helen suffered greatly during the 1998 El Niño year, which led to bleaching events worldwide. El Niño years result in warmer waters and temperatures. Bleaching occurs when corals lose their endosymbiotic algae, Symbiodinium, due to stress, usually extremely hot temperatures. The colors of corals are actually a result of the pigmentation in this algae, so when corals lose their symbionts the colonies appear white, as the calcium carbonate skeleton becomes visible through the coral's naturally translucent tissue - hence the term bleaching. If temperatures return to normal and the stress ceases in time (at most a few weeks), corals can re-acquire their algal symbionts and return to a healthy state; however, if they remain bleached for too long, colonies can die as they starve without the input of carbohydrates that their algae typically provide. 

Example of a bleached coral
colony in Dongsha Atoll
Photo credit: T. De Carlo 

Much of the monitoring efforts implemented in Palau were a response to the extensive coral bleaching that occurred during 1998. Thanks to these efforts we now have data following the recovery, or lack thereof, of reefs from that time period thru today. Helen's reefs suffered dramatically during this event, but made a quick and remarkable come back, making Helen Reef an important site to characterize and understand. During our time here we collected samples and conducted surveys at various different habitats including the outer reef crest, inner reef and the channel that leads into the lagoon of Helen's atoll (the channel is the squiggly line in the satellite view above). 

Corals at Helen Reef
Photo credit: H. Rivera

Coral diversity at Helen Reef
Photo credit: H. Rivera

Wreck on Helen Reef

During our dives we found colorful and diverse reefs, thriving with life. In our first dive on the outer reef, two small reef sharks greeted us as we swam from our boat over the drop off towards the reef, which was dominated by branching corals and small fish. On our way to the second dive site a pod of dolphins followed us into Helen's lagoon, jumping over the rough waves that are typical of Helen's NW side, where several wrecks in the distant attest to the dangers of running aground onto a coral reef. In our second dive site we found plenty of massive Porites, great for our coring and tissue sampling needs. Our second day of diving was likewise full of great dive sites, with good coral, a testament to Helen Reef's resilient recovery from previous bleaching events. Overall, our work here was a success and the diving spectacular. We even got to visit the ranger's island, but I'll tell you all about that in the next post. Next stop: Kayangel. 

-Hanny Rivera

Where in the world are our strongest corals?

Seventy Islands, Palau - One of several
Rock Islands chains in Palau

The Palauan archipelago is a composed of more than 250 islands. Among these are about 200 known as the Rock Islands, due their tough limestone composition. These islands form a series of semi enclosed bays south of Palau's most populated island, Koror. These bays are thriving with wildlife and the coral cover and diversity is spectacular, especially when considering the environmental conditions in these areas...

Reef-building corals, build make their skeleton from calcium carbonate (limestone),

specifically the aragonite mineral form of calcium carbonate. How difficult it is for them to make aragonite is largely dependent on a quantity called the aragonite saturation, which essentially corresponds to how favorably this mineral can form under the current conditions and is very sensitive to the pH of the water.

Decades of research on coral health and optimal conditions for coral growth indicate that corals can make their skeletons more easily and more quickly when the pH is more basic as opposed to more acidic, or correspondingly when the aragonite saturation is higher. The relationship between coral growth and pH is particularly relevant in the context of global climate change and rising atmospheric concentrations of CO2 - as CO2 concentrations in the atmosphere increase, more CO2 becomes dissolved in the oceans, a process that decreases the pH of the water (commonly referred to as ocean acidification), and decreases the aragonite saturation. Combined with other stressors such as increased temperatures, increased pollution and nutrient input, impacts from overfishing and coastal developments, corals face an increasing number of threats.

Corals in Nikko Bay, Palau
Photo Credit: H. Barkley

In Palau's Rock Islands, the pH and the aragonite saturation is much lower than in the surrounding outer reefs, however, the corals in these bays show no reduction in growth despite living in conditions we would normally deems stressful for their growth. Our lab made this discovery a few years ago and has been studying the corals in these bays ever since, trying to understand just how they are able to defy our expectations. Why can they thrive under these conditions? Have they always been able to do so? Are the populations in these bays different from those in other regions of Palau? Is there genetic exchange between these resistant corals and other populations in Palau's outer reefs and beyond?

In our current expedition will have a rare opportunity to reach some of the islands farthest from Palau's mainland, such as Helen Reef, the southernmost of Palau's reefs and Kayangel, the northernmost. We will characterize environmental conditions at these new sites - for instance, are there other low pH sites we've yet to uncover? Furthermore, we also want to study connectivity between different areas of Palau. By taking tissue samples from corals at multiple locations, we can use genetic techniques to study gene flow between different regions, this can tell us if corals in a particular environment, such as the low pH Rock Islands, are genetically isolated from other populations and have perhaps adapted to these conditions over time. If they are not isolated, it can tells us where these resistant populations could have dispersed to in the past, indicating those areas may show resistance when conditions become stressful in the future. Knowledge that is very important in making adequate management decisions.

We will tour Palau for almost three weeks, stopping at fifteen sites. We are quite fortunate to have use of the vessel M/V Alucia, for our work during this expedition, without which access to the farther reefs like Helen and Kayangel would have been unfeasible. We'll keep you posted with updates, so don't forget to follow us!

Anchors away.

-Hanny Rivera