Yap Manta Diving
Tis the season for the year’s most exciting manta ray diving where the chance to find yourself in a manta mating dance over a shallow reef, exist here like nowhere else in the world.
At daily manta ray dives where we’re getting the cleaning station encounter with rays slowly gliding right in front and over divers.
Manta mating season is December – April where we start to expect females coming in to clean with would-be courting males in their zone.
Down south, where we’ve only seen a manta cleaning once, we hover over white sand slopes and scour pinnacles looking for macro life.
Yap Caverns Macro
As part of Marine Biology weeks event, we have some fun information about Yap’s mangroves to share:
A view from space on Yap shows a green island with dense forests. Yap is not a volcanic island, but part of the largely submerged oceanic Philippine plate (whereas actually most of the Philippines do not belong to this tectonic plate). In the east, the Pacific plate is partially subducting below this plate, forming the Yap trench with more than 8500m depth. Yap Island is surrounded by a 1-2km broad fringing reef, that is interrupted by several channels and inside there are highly structured lagoons and bays. Along the coastline there are extensive mangrove forests. During our Marine Biology Weeks we explored several Mangrove sites, which can be seen in the map:
- German Channel
- Channel Maap – Rumung
- Chamorro bay
- Mangroves at Mii´l lagoon
- Mangroves at Tamil
Ecological role & nutrient cycles
Considered by some as useless and unaccessible swamp full of mosquitoes – in fact the mangroves present a fascinating and important ecosystem , and within it is teeming with life. Building a bridge between land and the sea, mangroves serve as a nursery for reef fish, haven for small marine life and habitat for a peculiar community.
Mangrove trees can drop more than 700 tons of leaves per square km per year. Mangrove leaves and dead seedlings are being devoured by snails, crustaceans, worms and others, which in turn are food for the higher stages of the food web. The remaining parts and mud, which has still a certain content of organic material, is cracked down further by bacteria and fungi, which are food for microorganisms, filter-feeding sponges, and detritus-feeders, like sea cucumbers. And again: everything goes up the food chain – straight to the fish, birds, mammals at the top. Therefore the mangroves provide a constant nutrient and food supply for the associated fauna and flora, as well as adjacent ecosystems, e.g. the coral reefs. At the direct border to the sea, and inside the lagoons, bays and rivers, the mangrove stilt-roots are marching out to expand their living space. Water currents are effectively lowered through the thicket, thus, sediments can settle down in this sheltered space between the roots, creating an unique mangrove ecosystem, also called “Mangal”.
Mangrove trees are best adapted to the stressful conditions of saltwater immersion.
Tides are washing in and out, the muddy soil lacks oxygen – no other trees may survive here! Mangrove trees are able to extract their fresh water from the salt water, and some species then just expel the salt through their leaves. That can be seen as visible salt crystals on the leaves.
Within the mangrove zone, various species occur successively from the seaward border to the inner zone. These inner zones get immersed by saltwater only during extreme high tides or storms and are increasingly influenced by freshwater. The different mangrove species have different forms of aerial roots which escape the anoxic soil and enable gas-exchange during flooding:
- Stilt-roots arise from the trunk and extend outward and downward into the soil
- Pneumatophores are pencil-like roots protruding upward from horizontal roots
- Knee-roots are like bending knees above the ground, looping up and down with a knob-like structure at the top and
- Plank-roots, that are undulating, horizontal ribbon-like roots above the ground.
After fertilization, the mangroves´flowers develop into fruits, that may grow further as different shaped and elongated seedlings. One day, these seedlings drop from the tree. While most of these seedlings will not survive, but become food for crabs and other shore inhabitants, some of them may settle in the closer vicinity of the parent tree, while others may float away for as long as one year, to form new colonies far away, possibly to colonize new islands…
According to a terrestrial biodiversity survey from 2002 (M. C. Falanruw) for the “FSM National Biodiversity Strategy and Action Plan Project”, Yap has the most diverse mangroves and the most species of mangrove trees within the Federated States of Micronesia (FSM), with a total number of 15 species, whereas Kosrae, Pohnpei and Chuuk have only 10 species each.
Rhizophora stylosa is the most common mangrove at the seaward margin, they form prominent stilt-roots and elongated, pointed seedlings. There occur three other Rhizophora species at Yap.
Bruguiera gymnorrhiza prefers low salinity areas with freshwater input and therefore occurs mainly from the middle to the inner mangrove zone. They have conspicuous knee-roots and form elongated seedlings, similar to Rhizophora spp.
Sonneratia alba forms conical Pneumatophores arising from the anoxic, sandy mud. It occurs within the whole Mangal, from low to high salinity areas. The leaves and seedlings are rounded.
Xylocarpus spp. form heavy fruits with a diameter up to 20cm which are therefore called by the locals as „canon balls“, cause they produce a loud splash when they fall down in the water. They occur within the inner zone and prefer a low salinity.
Inside the Mangal
Obviously, entering the mangroves is not the same as snorkeling in the crystal clear water of a sandy lagoon. But after entering the turbid water and once your eyes become adapted to the shady light conditions, you get compensated with interesting insights:
At places where a minimum amount of light is available, algae grow on the roots or any other available kind of substrate.
Occasionally snails and crabs can be seen underwater, tunnels within the sediment give a hint towards their inhabitants.
Much of the life, with all those tiny invertebrates, occurs within the mud. But after a while staying motionless in the water, the first fish occurs:
The shy Banded archerfish (Toxotes jaculatrix) patrols swiftly through the stilt-root thicket. This fish got its name, cause it targets insects which are sitting on a branch up to several metres above the water surface, in order to shoot them down with an accurate rush of water to devour it. Another wonder of nature, how these creatures could make this as its life concept, despite the difficulties due to the refraction of light through the water surface.
Between some branchwood fallen into the water – a group of Silver moonies (Monodactylus argenteus) hangs around. In the sunnier vicinity I spot various other mangrove-associated fishes, like half-beaks (Hemiramphidae), various Cardinal fish (Apogonidae), Mojarras (Gerreidae) and Whiptail Breams (Nemipteridae). Within the thicket of roots, juveniles of various reef fishes find shelter. The mangroves are widely known for their importance as nursery for reef fish. Now I see juveniles of various reef fish, e.g. surgeonfishes (Acanthurus triostegus and A. nigrofuscus), Triggerfishes (Rhinecanthus aculeatus) and others.
At the transition to the sea grass, where more light is available, life becomes more obvious: Various green, red and brown algae are growing on any available hard substrate. A glance on the corals which live at the edge of the mangroves makes clear that sedimentation is a very important factor for corals. It’s a constant struggle against being buried. After a disturbance of sediments caused by any usual tidal flood, or storm, or any other major water movement, these sediments will settle down on all surfaces, and there is no exemption for the corals. The coral may get rid of these sediments by contraction of it´s tissue or excretion of mucus – but all by the cost of energy. Thus only a few groups or species of corals may live (or better said: “survive”) within the mangroves. Mainly those species are highly opportunistic ones that occur in a very broad range of different environments, e.g. Porites spp. or Pocillopora spp.. Here, they do not need to compete with all those corals, like in the lagoons or on the outer reefs… but despite this, it´s really hard to survive…
In addition to sediments, the sponges are the most severe challenge: Sponges of various colors and shapes thrive in course of their abundant bacterial food, scientifically called “pico-zooplankton”, which they filter out of the water column, often a multiple of their own volume within a minute. They may grow on any kind of hard substrate, even on live crabs. And in some cases they also bore into live corals, finally eroding their host. In the coral reef one can observe the constant battle for living space not only between different corals, but also between corals and sponges and algae. Beneath breakage through storms, sponges represent one of the major contributors for reef erosion. And here, within the mangroves and seagrass beds, the sponges are clearly at advantage…
Tunicates are highly evolved organisms and ancient relatives of the vertebrates, including us humans. Actually, tunicates and vertebrates belong to the same tribe (Chordata) within the tree of life. But after their larval stage in which they resemble a vertebrate larvae, they just settle down on a free place on hard substrate in order to become a brainless filter-feeder, same as the much less developed sponges.
After these short snorkel trips at six different mangrove sites and getting only a quick insight of these cryptic ecosystems, I realize that here is much more to be explored…
Importance & Conservation
A huge amount of the worlds´ mangrove forests have already been destroyed through rigid coastal development, or by the shrimp-farming industry. Since whole mangrove systems have just been eradicated all over the globe, we should consider their real importance, not only as an unique ecosystem and haven of biodiversity, that plays a crucial role for the adjacent marine environments, especially the coral reefs. Not only this, mangroves also protect the shorelines from tidal erosion and heavy waves from tropical storms as a second front line, straight after the coral reefs which are the first fortress against the power of the oceans. Just to give an example – this has clearly been recognized after the devastating Tsunami in 2004 in Sumatra, where mangrove areas had experienced a much lower death toll than unprotected areas. Especially in view of rising sea levels the coastal protection provided by healthy mangroves, should be seen as a very important aspect and the remaining mangroves will play an increasing role for coastal communities in the mid-term. Simply said – the mangroves have to be protected, so they will protect us.
Text & Photos: © Stephan Moldzio / Marine Biology Workshops: http://www.greencorals.de/english-mangroves-of-yap/?lang=en
***Great first MARINE BIOLOGY WEEKS at Manta Ray Bay Resort !***
Three different Workshops were successfully conducted in course of the first Marine Biology Weeks at Manta Ray Bay Resort & Yap Divers in Yap/Micronesia: One 3-day Marine Biology Workshop “basic”, a 2-day Coral-ID Workshop and a 2-day Marine Biology Workshop “advanced”.
MARINE BIOLOGY WORKSHOP “basic”
During the 3-day Marine Biology Workshop “basic” we started with fishes, how to identify the families, their characteristics and we dealt with their ecological role. We worked with a reef illustration and “plastic fishes” and also used a species list from FishBase that includes 1070 fish species of Micronesia. Next day´s topic was coral reef ecology, the importance of coral reefs as centers of biodiversity, the overwhelming variety of different lifeforms and their manifold interrelations, as well as the today´s human threats to the reefs by climate change, overfishing, pollution and more.
Coral reefs play a fundamental role for humanity, not only in view of food production, coastal protection, livelihoods, but also as unique and fascinating habitats that have to be preserved. During our dives we collected samples of sand, reef rock and plankton and investigated them under stereomicroscopes. Wow! – even the sand represents a fascinating microcosm, with stunning organisms whose habitat is firstly determined by currents, sedimentation and therefore by the grain size of sand – and of course by food supply. This is where the mangroves and sea grass beds come into play which provide a continuous supply of organic matter…
Thus, we also made a kayak tour deep inside the mangroves – including snorkeling, of course! The mangroves represent an unique ecosystem with multiple important functions and there is a very interesting transition to the adjacent habitats, e.g. seagrass beds, the sandy bottom of the lagoons and the coral reef. We found the shy Archer fish and various other fish, corals, invertebrates and algae which live within the mangroves and sea grass beds.
After those investigations of mainly small marine organisms and their interrelations, we went to the dive site “Vertigo”. Fortunately, nobody experienced `vertigo´, but for the whole dive we had roughly 25 sharks around us. Mainly Blacktip – and Grey Reef Sharks, but occasionally a Whitetip Reef Shark passed along the deeper reef slope. In the thick of it, Two-spot Red Snappers and nearby, two Napoleon Wrasses, groupers, jacks and other “big fish”.
In the evenings we had two presentations about “Coral Reef Ecology” and “Corals – the architects of the reefs”, as well as two nightdives. Here, we observed all those invertebrates which are hiding during the day from their predators, which were sleeping right now until dawn… The coral polyps were fully expanded now and actively feeding on zooplankton that was bustling around in the water column (in fact, it felt like these little creatures were trying to invade our ears…)
One of these dives was a fluorescence nightdive with blue light lamps and yellow mask filters – all corals were glowing predominantly in green, but also in blue, red and even violet!
After the ´basic´ workshop all participants carried on with the Coral ID workshop.
In this 2-day workshop, we intensively dealt with corals and the method of coral ID down to genus level along the Indo Pacific Coral Finder authored by Russell Kelley, founder of the Coral Identification Capacity Building Program (CICBP). We took a closer look at their biology, on the process of reef building as well as impacts e.g. coral bleaching, sedimentation, overfertilization, feeding scars from various reef dwellers…
The Coral Finder is the way to tackle the not-too-easy field of coral identification, with the goal to determine any hard coral down to genus level. It is an elaborate visual method, that harnesses our human “eye-brain-supercomputer”, thus it is easy to learn for everybody.
After being empowered to distinguish the different corals from each other, the eye was ready to recognize their specific occurrence in the different zones of the reefs, from the deeper slopes of the outer reef, over the reef flat straight into the lagoons, while some tough species made it as far as to the mangroves…
Finally, on the last day of the first week we gave a small presentation about the outcome of our course to all guests on the restaurant ship “Mnuw”. We projected some pictures from the workshop on the big screen and our Reef Illustration with the fish species we had observed during these 5 days was displayed in the hotel foyer.
MARINE BIOLOGY WORKSHOP “advanced”
Within the second week we had another 2-day workshop.
On the first day we started again with fishes and the reef illustration, as well as microscoping of sand, reef rock and plankton samples. On the second day we had a quick snapshot into the work with scientific databases, using the example of FishBase how to learn about fishes, how to gather informations about species and families and their ecology, and how to draw up fish species lists for any region of the world. With this tool, you can prepare yourself for the underwater world BEFORE you go into the water during your next diving holiday. Of course, this is a bit too much for only one day, but the participants have received the workshop materials to deal with these topics by themselves further on.
We also did a Fluorescent nightdive again, here we came upon a big crab which was busy just to pinch off one arm of an unfortunate blue sea star. Later on we saw another sea star, obviously intact, with only four arms…
At the dive spot and cleaning station “Stammtisch” we encountered the impressive Reef Manta Rays (Manta alfredi), who regularly visit these cleaning stations inside the lagoon beyond Mi´l Channel. But we have also had many other remarkable encounters: At the dive spot O´Keefe´s Passage a Bat fish felt so attracted by us, that it followed us for more than 20 minutes!At Lionfish Wall, a big male Bumphead Parrotfish came very close, encircling one of us for two rounds and slowly swam further down the reef wall… At dive site “Vertigo” we observed one sharksucker jumping over from one grey reef shark to a black-tip reef shark and back – just as if it had accidentally taken the wrong bus line…
These are only a few examples cause this is beautiful nature and you will always get surprised when you dive along the amazing reefs of Yap!
A big THANK YOU to all very active and motivated participants (you were really great!! :-), to the top guides from Yap Divers and the excellent support, infrastructure and logistics of the MRBR staff!
Text & Photos: © Stephan Moldzio / Marine Biology Workshops
P.S.: Check out these fish species occurring around Yap: https://www.facebook.com/pg/MarineBiologyWorkshops/photos/?tab=album&album_id=1632289843501647
Here is our lineup of presenting scientists for our next Manta Mania citizen science event.
Come learn about sharks and rays while diving with big animals in a super size 16 dive special event week in Yap! Photo ID’s, special research dives and learning directly from today’s leading scientists on our big animals in Yap.
Project Leader, Manta Trust
“This is an rare opportunity for divers to dive with manta rays together with the scientists who study them. You’ll get to see the type of equipment we use, how we gather information and how its processed. We planned this event to take place during manta mating season, the most active time of year where close interaction with multiple animals is nearly assured – we are hoping to get a lot of valuable information. During the day you’ll dive with mantas and over the pristine reefs surrounding Yap, in the afternoon you’ll attend workshops to learn about megafauna, and in the evening you get to see pictures of these amazing animals. Not only will you be learning about mantas but also their very close relatives the mobula, sharks and other marine mammals. We hope everyone will come away from this experience awed by the ocean and its creatures with a deep appreciation for Yap and love for it’s people and culture.”
President, Founder, Chief Scientist – HAMER
Dr. Deakos has spent most of his entire life in the water, either as a competitive swimmer, water polo player, scuba diver and marine biologist. Originally from Canada, was fortunate to experience living in various countries around the globe during his early years. His chosen career working in wildlife biology and marine research is an extension of his passion for the natural world and his marvel for the ocean. After working with several avian and reptile species, his interests rapidly returned to the ocean and towards marine mammals, which eventually led him to Hawaii in 1996. At the University of Hawaii, he completed his master’s degree studying humpback whale behavior and continued his graduate work by completing his doctoral degree with a focus on manta ray ecology. In 2004, Dr. Deakos founded the Hawaii Association for Marine Education and Research (HAMER), a non-profit dedicated to protecting and preserving Hawaii’s manta rays. Over the past, over 430 distinct manta rays have been identified in Maui, the largest known in the United States, however sighting rates have dropped by over 90% in just the past decade. To help understand the reason for this rapid decline, HAMER is investigating habitat use using acoustic and satellite tags, stock structure and paternage using genetics, and age-class demographics and growth rates using paired-laser photogrammetry. An automated pattern-recognition software is being developed to match manta ray photos quickly and research continues to focus on ways to eliminate man-made threats to the mantas such as entanglement in fishing gear and impacts to their reef habitat through land-based sources of pollution.
Chief Science Officer, Association for Marine Exploration
Dr. Sonia J. Rowley is a postdoctoral research associate at the Department of Geology and Geophysics, University of Hawai'i, Research Associate at the Bishop Museum, and Chief Science Officer for the non-profit organization the Association for Marine Exploration. She is also the recipient of the prestigious Sir. David Attenborough Award for Fieldwork, and recently elected Fellow of the Linnaean Society of London.
Sonia specializes in the evolution and diversity of gorgonian (sea fan) octocorals, particularly across different depths throughout the Indo-Pacific. Sonia has >34 years diving and expedition experience around the globe, and integrates advances in closed circuit rebreather diving technology with a suite of analytical research tools for her work. She endeavours to share her research discoveries especially with the local communities throughout the Indo-Pacific to assist in reef conservation measures. Sonia is particularly delighted to be part of Manta Mania as it provides the opportunity to share her experiences and excitement of these magnificent animals, as well as the many fascinating creatures she encounters at depth.
Guam Long-term Coral Reef Monitoring Program
Roxanna Miller has been living on Guam for the past 11.5 years and graduated with her Master's in Biology in 2011 from the University of Guam. Upon graduation, Miller worked for a small environmental consulting firm before she began working for the Guam Long-term Coral Reef Monitoring Program as the Guam NOAA Coral Fellow. After her fellowship ended, she was the Guam Marine Invasive Species Coordinator for a short period before returning to the Guam Long-term Coral Reef Monitoring Program as the Monitoring Technician in 2015. Since the birth of her second child in 2016 she has taken an leave of absence but remains one of Guam’s coral experts, remaining close to the ocean professional and personally as an avid paddler.
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Great first MARINE BIOLOGY WEEK at Manta Ray Bay Resort & Yap Divers!
During the 3-day Marine Biology Workshop “basic” we started with fishes, how to identify the families, their characteristics and ecological role. We also used a species list from The FishBase Project including 1070 fish species of Micronesia. Next day´s topic was coral reef ecology, the importance of coral reefs as centers of biodiversity, the overwhelming variety of different lifeforms and their manifold interrelations, as well as the today´s human threats to the reefs by climate change, overfishing, pollution and more.
Coral reefs play a fundamental role for humanity, not only in view of food production, coastal protection, livelihoods, but also as unique and fascinating habitats that have to be preserved.
During our dives we collected samples of sand, reef rock and plankton and investigated them under stereomicroskopes. Wow! – even the sand represents a fascinating microcosm, with stunning organisms whose habitat is firstly determined by currents, sedimentation and therefore the grain size of sand – and of course food supply. Here comes the mangroves and sea grass beds which provide a constant supply of organic matter… Thus, we also made a kayak tour deep inside the mangroves – including snorkeling, of course! The mangroves are an unique ecosystem with multiple important functions and there is a very interesting transition to the adjacent habitats, e.g. seagrass beds, the sandy bottom of the lagoons and the coral reef. We found the shy Archer fish and various other fish, corals, invertebrates and algae living within the mangroves and sea grass beds.
After those investigations of the “small stuff” (we should actually reconsider it as “basic stuff”…) we went to the dive site “Vertigo”. Fortunately, nobody experienced `vertigo´, but for the whole dive we had roughly 25 sharks around us. Mainly Blacktip – and Grey Reef Sharks, but occasionally a Whitetip Reef Shark passed along the deeper reef slope. In between, Two-spot Red Snappers and nearby, two Napoleon Wrasses, groupers, jacks and other “big stuff”.
Well, the Mantas appeared to be sufficiently cleaned, thus there was no need to visit the cleaning station at Goofnuw channel… or they were at Mil´ channel while we were hanging around Goofnuw…
In the evenings we had two presentations about “Coral Reef Ecology” and “Corals – the architects of the reefs”, as well as two nightdives. Here, we observed all those invertebrates which are hiding during the day from their predators which were sleeping, then, until dawn… The coral polyps were fully expanded and actively feeding on zooplankton that was swirling in the water column (actually those small creatures tried to invade our ears…)
One of these dives was a fluorescence nightdive with blue light lamps and yellow mask filters – all corals were glowing predominantly in green, but also in blue, red and even violet!
While the 2-day Coral ID workshop, we intensively dealt with corals and the method of coral ID down to genus level along the #Indopacific Coral Finder authored by Russell Kelley / BYOGUIDES , founder of the Coral Identification Capacity Building Program (CICBP). We took a closer look at their biology, on the process of reef building as well as impacts e.g. coral bleaching, sedimentation, overfertilization, various feeding scars … After being empowered to distinguish the different corals under water, the eye was ready to notice their specific occurrence in the different zones of the reefs, from the deep slopes of the outer reef, over the reef flat straight into the lagoons, while some tough species made it as far as to the mangroves…
Finally, on the last day we gave a small presentation about the outcome of our course to all guests on the restaurant ship “Mnuw”. We beamed some pictures from the workshop on the whiteboard and our Reef Illustration with the fish species we had observed during these 5 days was displayed in the hotel foyer.
A big THANK YOU to all very active and motivated participants (you we´re really great!!), to the top guides from @YapDivers and the excellent support, infrastructure and logistics of the MRBR staff!
Diplom-Biologe Stephan Moldzio über die 1. Meeresbiologie-Woche in Yap:
“Während des zweitägigen Korallenbestimmungs-Workshops befassten wir uns ausführlich mit Korallen und der Methode der Korallenbestimmung auf Ebene der verschiedenen Gattungen. Dazu verwendeten wir den “Indopacific Coral Finder“ von Russell Kelley/BYOGUIDES, Gründer des „Coral Identification Capacity Building Program (CIPB).
Einen genaueren Blick warfen wir sowohl auf ihre Biologie, auf den Vorgang der Riffbildung als auch auf Einflüsse wie Korallenbleiche, Sedimentation, Überdüngung, Fraßspuren verschiedener Riffbewohner…
Nachdem alle Teilnehmer mit dem nötigen Rüstzeug ausgestattet waren um die verschiedenen Korallengattungen unter Wasser zu unterscheiden, ging es natürlich geradewegs ins Wasser. Nun nahmen die Teilnehmer auch das Vorkommen der unterschiedlichen Korallen in verschiedenen Zonen der Riffe wahr – von den tiefen Hängen des Außenriffs über das Riffdach, geradewegs in die Lagunen, während es einige widerstandsfähige Arten handelt, bis in den Mangrovengürtel schaffen.
Bei diesen Untersuchungen bekamen die Teilnehmer Plätze zu Gesicht, die im Tagesprogramm nicht angefahren werden.
Die Teilnehmer lernten den Unterschied zwischen in Folge der Korallenbleiche ausgeblichenen Korallen und kürzlich abgestorbenen Korallen kennen und erkannten auch Frassspuren etwa von Papageifischen, Falterfischen, Drupella-Schnecken oder Dornenkronen-Seesternen.
Was mal wieder zeigt: Meeresbiologie ist mitnichten trockene Kost – tatsächlich ist sie ziemlich spannend sobald man erst einmal die Zusammenhänge im marinen Ökosystem versteht.
Am letzten Abend gab es dann eine kleine Präsentation zu den Resultaten auf dem Restaurantschiff Mnuw. Wir projizierten einige Fotos vom Workshop auf die Großleinwand am Top-Mast, und unser Riff-Modell mit den in den vergangenen fünf Tagen beobachteten Fisch-Arten wurde im Hotelfoyer aufgestellt.
Ein großes DANKESCHÖN an alle aktiven und motivierten Teilnehmer (Ihr wart wirklich toll!!), an die superguten Guides von Yap Divers und an das Team vom Manta Ray Bay Resort für ihre exzellente Unterstützung, Infrastruktur und Logistik!”
Hier geht es zu Stephans Facebook-Seite mit noch mehr Fotos: https://www.facebook.com/stephan.moldzio/media_set?set=a.716343725230907.1073741838.100005658570842&type=3&pnref=story