Saba Bank expeditie: Memoires van een vrijwilliger

Vrijdag 30 oktober
Bas Westerhof

Als oud marien bioloog en nu hoofdzakelijk part time postbode is de rol van vrijwilliger een mogelijkheid terug te keren naar mijn oude leven. Een mogelijkheid om, zij het in een ondersteunde rol, weer eens wetenschappelijk te zijn. Oh and for Thank You’s look at the last paragraph.

Vrijdag 23 oktober:  Een dag voor we aan boord zouden gaan worden we geacht dat we op Sint Maarten zouden zijn. Dat was namelijk de opstapplaats voor mij. Het gaf mij en mijn mede-vrijwilliger Lodewijk tijd om te wennen aan de lokale warmte. Deze was drukkend, als op een warme zomeravond in Nederland, vlak voor een onweersbui.

Zaterdag 24 oktober: In de middag, rond een uur of drie zouden we opstappen. ‘s Ochtends om een uur of 10 stonden we op de stoep. Een beetje vroeg, maar goed, een rondje door klein Amsterdam -een inwoner vergeleek Sint Maarten met Amsterdam vanwege het bijna identieke aantal nationaliteiten- en het was lunchtijd. Tijdens de lunch maak ik kennis met een aantal mede-expeditieleden. Daarna, om een uur of vier vertrokken we richting Statia om de laatste expeditieleden en materialen op te pakken.

Het opzetten van de tent

Zondag 25 oktober: De eerste duikdag en de reden dat ik mee ben. Het assisteren bij de onderwaterwerkzaamheden. De dag werd begonnen met een tocht richting de Sababank, waar mijn werkzaamheden zich zouden focussen op het opzetten van de tent. Belangrijk hierbij is om te weten dat de tent zo min mogelijk mag lekken. Anders zijn de metingen nutteloos. Dat is gemakkelijker gezegd dan gedaan. De Sababank bestaat namelijk uit een volwassen rif en geen zand. Haringen kreeg je dus niet in de grond en de tent werd door de stroming langzaamaan vrij getrokken van de kettingen en de loodblokken.

Maandag 26 oktober: Vlak voordat we onder zouden gaan om metingen te doen volgt een nieuwe opdracht. De tent en omgevingsapparatuur moet omhoog. De proef zal worden voortgezet in de luwte van Saba, waar haringen wel de bodem in kunnen. Het probleem daar echter was dat erin de week ervoor net de eerste regen in maanden was gevallen. In de namiddag ging de eerste poging tot het opnieuw opzetten van de tent dan ook verkeerd.

Dinsdag 27 -Vrijdag 30 oktober: De tent hebben we dinsdag succesvol neergezet en heeft met wat kleine wijzigingen tot donderdagmiddag op de bodem gestaan. Gedurende die tijd werden er overdag om de 3 uur metingen gedaan. Ondertussen maakte ik kennis met de populatie verpleegsterhaaien aldaar. Sommigen nieuwsgierig kijkend naar de apparatuur, andere slechts gebruik makend van ons effect op kleinere vissen. Een daarvan in het bijzonder mag worden genoemd: Spot, ook wel Gorby genaamd vanwege de opvallende vlek op zijn hoofd was een vaak geziene gast.

And with Spot I would like to start the heartfelt Thank You’s to the people that made the expedition a lasting memory for me. To the scientists I say thank you for taking me along for the boat ride. To the other volunteers I say it was great working with you. To the crew I say thank you for putting up with me. And perhaps I should notify the non-Dutch reading people of this at the start. So see you and once again thank you.

Greetings Bas Westerhof.

Saba Bank Expedition: Camping under water II

Fleur van Duyl
Saturday 31 October 2015

Hi there! I am Fleur van Duyl of the Royal Netherlands Institute for Sea Research on Texel. I organized and coordinated the second week of the 2 week expedition to the Saba Bank 2015.  With a group of 14 scientists of NIOZ, IMARES, Naturalis and volunteers (thank you so much) and the professional and friendly crew supporting us we had the challenging task to do high tech research on the Saba Bank. Fancy equipment was launched from the Caribbean Explorer II liveaboard followed by a bunch of brave divers and crew. Conditions on the Saba Bank range from dead calm to hurricane conditions. We hit almost dead calm for a short period followed by increasing oceanic swell. Imagine you are tossed back and forth over the sharp calcareous reef bottom and try to take your underwater samples at 15-20m depth or get heavy equipment down to do it for you, or put up a tent. Yes, it is fun and hard! Nobody has been doing this in such a setting before as far as we know.

Photo. 1. Sunset with Captain Michael of Caribbean Explorer II and me (photo Oscar Bos)

The aim of this week is to find out if the Saba Bank, a gigantic 2200 km2 atoll next to Saba, is net growing or eroding. Climate change causes the oceans to warm up and to acidify. This affects corals , coralline algae and other calcifying organism that produce calcium carbonate.  And eutrophication adds to that. The corals are also exposed to coral-eroding organisms such as parrotfish or sea urchins. These graze for tasty algae or dig holes and grind away the calcium carbonate. Sponges excavating the corals are very common here as well and might play a large role in the breakdown and dissolution of calcium carbonate. To test whether the reef grows or erodes, we set up an experiment on the seafloor, in which a small part of the reef is enclosed by a tent and monitored accurately.

Photo 2. Underwater campsite (photo Erik Meesters) 

We had to leave our underwater camp site  on the Saba Bank  because of increasing swell (with the danger of damaging equipment) and wind speed and we headed for a more protected site in the shade of the only active volcano of the Netherlands (Dutch Caribbean), Mount Scenery on Saba. When you stick your hand in the sand underwater you might feel the heat coming out (interesting underwater temperature profiles..).  We put up our underwater campsite at about 20 m depth. Nurse sharks did not really bother our presence and activities. They liked the underwater lights of the divers for chasing prey (happily not us). Turtles now and then inspected the site. We kept the tents and other equipment in for several days and hope for a smashingly exciting data set. We are now on our way back to St Maarten and I am deeply relieved that we came all out safe and healthy. See us next time Saba Bank!!!

Saba bank expedition: Coral fauna of Saba and the Saba Bank

Bert W. Hoeksema
Naturalis Biodiversity Center, Leiden, The Netherlands
Thursday 29 October 2015

The original aim of the coral diversity survey was (1) to find out whether the coral fauna of Saba Bank matches the coral fauna of St Eustatius and (2) to check whether the Saba Bank coral fauna has remained the same over nearly half a century by a comparison with results of an earlier marine biodiversity expedition to Saba Bank, which was organized in 1971 by the Dutch Navy and Naturalis.

A disk-shaped corallith at Saba Bank (Photo: Bert Hoeksema).

Due to weather conditions and other circumstances, only three dives were made on Saba Bank, all at a single locality, which is not enough for the planned comparisons. A total of 18 stony coral species was recorded (15-17 per dive). Some of the encountered coral species showed morphological variation by being either attached or free-living. The latter are so-called coralliths or living rolling stones. However, coralliths belonging to the genus Madracis were not ball-shaped as regular coralliths but disk-shaped, similar to many species of mushroom corals in the Indo-Pacific. This particular coral shape may be related to swell-generated currents that push free-living coral fragments over the shallow sea floor.

Because diving at Saba Bank had to be aborted, the survey was continued at Ladder Bay, Saba, where nine dives were made. Here a total of 42 species was encountered (26-37 per dive), which is a very high number for a single locality in the Caribbean. One of these species is Tubastraea coccinea, a non-indigenous species from the Indo-Pacific. This species may have been introduced as fouling organism on an oil rig and was first reported from Curaçao in 1943. It is known as an aggressive invasive species in Brazil, where it competes for space with local, endemic coral species.

Tubastraea coccinea is a non-indigenous coral species, which accidently has been introduced from the Indo-Pacific (photo: Bert Hoeksema).

Some stony corals were observed as host for the Christmas tree worm (Spirobranchus giganteus). Various host coral species were previously not known as associate for this tube worm, which is probably a generalist with regard to its host preference. However, many coral species have never been reported as its habitat.

Christmas tree worm as associate of an Agaricia fragilis coral at Saba, which probably represents a new host record (photo: Bert Hoeksema).

Saba Bank Expedition: A tale of many corals

Dahlia Hassell
Thursday 29 October 2015

Me studying coral diversity

Hi, I am Dahlia Hassell and currently I am working for the Saba Conservation Foundation as the Saba Bank Science Officer with the Saba Bank Management Unit. My work with the Saba Bank consists of the fisheries data monitoring and assisting the IMARES students with their research during their time on Saba along many other tasks.

As a native of Saba, it was a pleasure to experience the Saba Expedition 2015 with new faces and various goals for the week.

Me and the giant tarpon (photo: Erik Meesters)

In my perspective, many times the corals that are found on Saba tend to be overlooked and this week I was able to see the underwater world in a different perspective. Hard coral expert, Bert Hoeksema, was my buddy for the week and a blessing in disguise due to my lack of expertise in the subject. Our week consisted of searching within the crevices of the reef, under the ledges, in shallow/ deep waters for the various species found on the Saba Bank, and the dive site Ladder Labyrinth on Saba. Together, we were able to spot a total of 42 species of hard coral on Ladder Labyrinth and that's hitting a record! Can you imagine if we were able to visit the other dive sites on Saba?

On another note, this was not the only thing that kept us busy on the Caribbean Explorer II for the past week. One of the items on the Expedition list was to set up the incubation tent underwater and it was quite the task for the divers. Science was in the making, and I was astounded by how the researchers turned the vessel's boutique into the lab, or how they spent countless hours in a dinghy  to wait for the the water samples, or pumping the tent to ensure it would stand tall, and basically all that was part of the tedious process that involved in having valid data from this tent.

Science became alive in the eyes of this Saban during this past week, and it was an honor to witness it in my homeland's waters.

Expedition Saba Bank with the Caribbean Explorer - 2015

Expedition Saba Bank with the Caribbean Explorer - 2015

The lettuce slug (Elysia crispata) (photo: Ewan Trégarot) 

We have been looking at benthos community, fish assemblages, reef complexity and water chemistry to characterize ecological and chemical dynamic of coral reef on Saba Bank/Saba.

At home, in Martinique, I work in a Non-Profit Organization (Observatoire du Milieu Marin Martiniquais). I usually do reef monitoring for the French Initiative on Coral Reef program (IFRECOR), either benthic or fish assemblages surveys. The arrival of the red lionfish has kept me busy for the past few years.

Now and then, I do underwater photography with my very small compact camera that can make relatively good pictures.

This expedition was also a real challenge in terms of photography as I was « competing » with people having super high resolution - wide angle or macro lenses on full frame DSLR or very good APS-C cameras. Night dives were most of the time optional but I manage to do all of them, as it’s always full of reef creatures we hardly see during the day.

Nurse shark during the night dive (photo: Ewan Trégarot)

Rays and sharks have contributed a lot to the awesomeness of the dives, especially the little nurse shark that keep following you during night dives. Very cool at first, it became a little annoying when it starts bumping your hand while you try making macro pictures! It’s very much like a pet!

Erik might be one of the most difficult buddy to keep close by, but always a pleasure to dive with him!

GoPro time lapse came up really well with a successful deployment of the tent in Ladder Bay, Saba.

Alkalinity was measured with the famous “SEAS-DIC”, which somehow contributed a lot to making bad jokes. Je ne sais toujours pas pourquoi...

An impressive barracuda (photo: Ewan Trégarot)

Rugosity was, to sum up, my main duty on this expedition, along with some coral recruits recording, tent deployment and water samples.

Oscar asked me to write something for this very special blog, so I’m making it a little special for this very special man!

Thanks everyone for this amazing expedition! The crew was fabulous and the “cuisine” very good!

Ewan Trégarot (if you haven’t figured it out yet)

Saba Bank Expedition: Small lab science

Steven van Heuven
Tuesday 27 October 2015

Our titration lab in the 'boatique'

Among seagoing oceanographers, it is generally assumed that personal comfort during cruises (we like to call them 'expeditions') scales with the size of the research vessel: small ships have people share huts and eat deep fried food, while larger ships may have luxuries ranging from mere pools and gyms to small grocery stores (generally liquor only) and bakeries preparing fresh pastries and cake every day. Our current makeshift RV, the live-aboard Caribbean Explorer II does not fit along that line. It a vessel of only some 30 meters long, but WITH the freshly baked cookies, bread and cake, excellent food and deserts, bedding service AND featuring a rather oversized (saltwater) pool at tropical temperatures. And they even allow diving harhar.

Are there no drawbacks then? Should every country get on board with the microship-revolution? Well, if there is a single complication about this boat, its that on with all that luxury there is little room left for anything else, LEAST OF ALL labspace. Bringing any more electronics than your underwater camera means you'll be working in the mess (locally referred to as the dining room) between meals.

For the one team on board that had hoped to be able to set up a small instrument in air-conditioned conditions this initially meant TOUGH LUCK – the dining room is not airconned, and it actually rather HOT and HUMID. After consulting with the crew – in particular the exceedingly cooperative, friendly, hospitable purser Rob – we were granted unique round-the-clock access to the ship's souvenir shop (the 'boatique' O_o), well stocked with various tourism paraphernalia (shirts, caps) at bewildering prices. Some of that was cleared away into tall, towel-covered piles to make place for our super fancy optical alkalinity titration setup.

Fresh samples to be processed

This new instrument, conceived by Sherwood Liu, our Floridian colleague and fellow passenger during week 1, allows us to perform highly precise and accurate measurements of the seawater property called 'alkalinity'. Whereas the classical super-expensive titrators would require 2 meters of bench space in a climatized laboratory and use dozens of liters of distilled water, the new instrument can be installed on the small table originally displaying 4 baseball-caps, and it consumes nothing but a single box of tissues per day (my regular rate anyway).

And that's how I found myself taking turns with colleagues Alice and Didier titrating and bubbling colorful little pots of seawater in a lab too small to fit a chair, but no less happy about it all.

Steven's Award

BYE! Steven

Saba Bank Expedition: Physical physics

Janine Nauw
Wednesday 28 October 2015

I’m Janine Nauw, physical oceanographer at the Royal NIOZ. In early May, I was invited to join the cruise on the Caribbean Explorer II (CE II) doing the physics part of the CoralCarib project, which looks into the calcification or erosion of the corals on the Saba Bank. The Caribbean Explorer II is not a research vessel, but a liveaboard. For non-divers, a liveaboad is a vessel for divers to take their holiday on. You can spend your whole holiday in the water, only going out when your dive-computer tells you to breath out some nitrogen, before going back in again. Meanwhile, the cook is preparing wonderful meals in the galley and your bed is being made and your room cleaned; it’s like an all-inclusive resort on the water. 

Me and my buddy

Doing research on a vessel like this is very much possible, I can say now after spending a week on the CE II. I was responsible for investigating the physics, or hydrodynamics, in the area surrounding the experimental site. The experiment involved placing a tent on the reef, closing it up and looking at the changing chemistry in the tent. Yes, you read it correctly, fellow scientists with help of the crew put up a decent size tent on the reef at 15 and 20 m below sea level! Putting pins in the reef is not really possible, so the tent was held in place by putting heavy chains and weights on the flaps that in normal circumstances keep the rain out, but in this case keep the water in. As with every tent, it cannot not be completely closed off from the environment, but always some exchange exists, e.g. the tent leaks. To determine the leakage, we measure the salinity inside and outside of the tent; add a certain amount of salt water in the tent and wait until the salinity in the tent is equal again the one outside of the tent. In practice, this involved actually diving down to the tent and adding a highly saline solution into the tent with a 500 ml syringe (or two). 

The Acoustic Doppler Current Profiler (ADCP) on the camping site 

Besides this, we also took an Acoustic Doppler Current Profiler (ADCP) down, which measures the currents and turbulence structure in the entire water column using sound pulses and recording the Doppler shift of the returned signal. This is a measure for the current speed, just as the change in frequency in an approaching or a parting ambulance is a reference for its speed. On the Saba Bank, it was on the hard reef, but near Saba in Ladders Labyrinth we had a sandy bottom, so we dug The ADCP in, keeping only its “head” above the seafloor giving us an extra 20 cm of data near the seafloor. 

Besides diving and digging, operating the CTD was also quite strenuous. A CTD measures salinity, temperature and depth throughout the water column by lowering it to the seafloor and hauling it again using a winch. I, a spoiled scientist who has worked only on proper research vessels, am used to the CTD being operated by an electrical powered winch by the crew, while I’m sitting inside watching a computer screen seeing the data coming in. Here, we don’t have that luxury, as there is no electrical powered which. However, we brought a manual one – I and many others of the scientific crew, got plenty exercise from that, especially on one of the three deeper cast that were more than 100 meters deep.

Hence it took quite some physical work, including lots of diving, some digging and exercising on the CTD-winch, to collect a very nice dataset about the physics of the experimental site. Meanwhile, we were being pampered by the crew, just like any other guest on the CE II would. And all of this in one of the most beautiful places in the world.

Saba Bank expedition: Camping under water!

Erik Meesters
27 October 2015

This picture could have been the start of a new hype. Romantic camping for divers. However, it is our little coral world, a so called mesocosm, in which we measure everything that is going on (see blog Fleur van Duyl).

Scientists from the Royal Netherlands Institute for Sea Research have worked night and day to get everything ready and working. Now we are here on the Saba Bank hoping for suitable weather. As it is we had to go to Saba Where we are trying our different mesocosms out. We have one big tent and two small ones and by measuring the chemistry of the water we can deduce how the little world under the tent is functioning. This will give us data that will help to understand how coral reefs function and how we can better protect them from pollution and the negative effects of climate change.

Expedition Saba Bank: First week done. Highlights.

24 October 2015
Erik Meesters Expedition leader first week

Divers hanging on line and waiting to be picked up
while being watched by sharks

Well the first week is behind us. Part of the team has now left and we have a couple of new people on board to help with the next part.The expedition went very well. We were able to do everything we had planned and more. The Dutch navy was able to put in the two new moorings, so we now we can stay the night over on the Bank without anchoring. This is very good, because that way we will not cause any damage to the reef.

We also explored a new part of the bank that appeared very rich in terms of coral cover and fish density. In many places we found large groupers and together with the large number of sharks this seems to indicate that the bank is in a relatively good condition.

Yellowfin Groupers closely followed by a trumpet fish on the
Saba Bank

We had very calm weather which helped enormously to get things done. Normally, wave are easily 2-3m high, but this year there only was a little rippling over the bank. Maybe this is related to the El Nino event  which is causing strange and unpredictable weather patterns all over the world. For the marine life it can be devastating. Some animals travel half way across the globe to rich waters and an El Nino may change current patterns and upwelling areas may not turn into the highly productive systems that animals expect or just turn into the opposite.

For corals an el nino may lead to warm water and to bleaching, the loss of the unicellular symbiotic algae from the tissue of the corals. As a consequence the coral appears white because the underlying white skeleton is shining through. The animal is not yet dead, but this is likely to happen if the warm water temperatures last for more than a week.

A coral (Porites astreoides)  that is partly bleached.

What exactly will happen is difficult to predict. Sea currents are among the most difficult things to predict. Let's hope sea water temperatures will quickly return to normal and that the damage to the Saba Bank coral ecosystem will be minimal. Since corals generally are very slow growing, an intense bleaching episode may need a few decades of recovery. There are indications that healthy corals bleach less, and reports from Gouadeloupe are already speaking of severe bleaching while here on the Saba Bank we only saw a few bleached corals. This seems to indicate that corals in general are healthy on the Saba Bank and may be some reasons for optimism for the Saba Bank coral reef ecosystem.

Expeditie Sababank: A Bank of Sponges?

Aiolochroia crassa. Photo by Oscar Bos.

By Lisa Becking

During the Saba Bank 2015 expedition, I am studying the sponge diversity. My partner in crime is Oscar Bos, who is making brilliant pictures of the colorful species. Here I’ll give a little background to the study and in a coming blogpost I’ll fill you in on our actual day-to-day activities.

The Saba Bank houses an expansive coral reef ecosystem with a rich diversity of marine species. Not only a high diversity of corals, but also a great diversity of sponge species. Sponges are little recognized yet vital components of reef systems. They are giant vacuum cleaners, which filter out all sorts of bacteria and fungi from the water column.

Sponges are able to provide food for other reef organisms by converting dissolved organic carbon into detritus. Besides food, they also offer shelter to a variety of creatures who live among the internal channels of the sponges. What is more, sponges are beautiful!

Sponges on the Saba Bank. Photo by Franck Mazeas

Hard surface is a valuable asset in the reef. Sponges and corals are in a constant rivalry for space. It may seem silent and peaceful down there, but all the while warfare is raging in the reefs as sponges and corals smother each other or exude their toxic chemicals to claim and maintain space. This competition is a natural state, yet in recent years there has been some concern that sponges are getting the upper hand and that the Caribbean reefs are turning into so called ‘sponge reefs’. The reason for this is that corals are becoming weaker and their cover is generally declining due to a variety of causes such as climate change, disease and local disturbances. A high abundance and diversity of sponges is not necessarily a bad thing, but a coral reef does need corals after all!

Callyspongia plicifera. Photo by Oscar Bos.

Due to its offshore location and upper-mesophotic reef system (20-50 m deep), Saba Bank coral reefs appear to have suffered relatively little anthropogenic disturbance compared to the reefs of the surrounding islands. Yet the Saba Bank reefs are still vulnerable to global stresses from climate change. With the current research we aim to see if the Saba Bank is becoming a ‘sponge reef’.

During the IMARES Saba Bank expeditions in the years 2011, 2013 and now in 2015, thirty-three 50m long transects were laid out in over the reefs and photographed. We will analyze these photographs of the benthos to see what the composition was of the community of sponge species in each year and to see how the cover and abundance of these sponges have changed through time. Identifying sponges based only on overview pictures is tough. To make certain we identify the sponges correctly, we’re setting up an identification database of sponge species, by collecting tissue and pictures of each species of sponge. When we get back home we’ll be identifying the pieces of sponge with molecular (DNA) techniques and morphological characters. In addition, we’ll compare our data with the historic collection of sponges from the Saba Bank from the 1970s that is now stored at Naturalis Biodiversity Center, Leiden.

Previous work of ours from 2013 has shown that Saba Bank is a store house of marine diversity for the nearby islands. With the current expedition we will document the sponge diversity that is thriving on the Bank.

Expeditie Sababank: het verhaal achter de foto's

Donderdag 22 oktober
Door: David Stevens

Ik ben David Stevens, huisarts in Voorburg en onderwaterfotograaf. Na 1 jaar biologie ben ik geneeskunde gaan doen. Biologie is echter wel altijd een passie gebleven. Boven water ben ik excursies blijven doen met oud studiegenoten en onderwater ben ik actief gebleven bij de Leidse studentenduikvereniging. De nadruk ligt bij deze vereniging op mariene biologie. Na 10 jaar duikervaring kreeg ik de behoefte de levende wereld onderwater vast te gaan leggen. Mijn passie onderwaterfotografie was geboren.

Het is begin juni 2015 toen ik van Ingvild Harkes de vraag kreeg om als onderwaterfotograaf mee te gaan op expeditie naar Sababank. Ingvild is bij het Wereldnatuurfonds (WNF) manager van het Kusten- en Oceanenprogramma in Caribisch Nederland. WNF is medefinancierder van deze expeditie. Mijn rol als onderwaterfotograaf is zo veel mogelijk van het onderzoek vastleggen in een beeld-verhaal. Met als extra opdracht ook foto's te maken die het grote publiek aanspreken. Dit is een aardige klus aangezien het onderzoek erg specialistisch is.

We komen aan en het is al meteen duidelijk dat ik niet de enige ben met een camera. Het zag er indrukwekkend uit. Eerlijkheidshalve moet ik zeggen dat ik me even afvroeg waarom ik was meegegaan, want ik was niet de enige fotograaf. Maar al snel realiseerde ik me dat Ingvild en ik de enigen aan boord zouden zijn die alle teams aan het werk zouden zien. Daar waar iedereen in zijn eigen onderzoek bezig is bewegen wij ons vrij tussen alle teams en krijgen alles te zien. Een heerlijke ervaringsrijkdom en ik voel me dan ook bevoorrecht dat ik dit allemaal mag vastleggen.

Er zijn meerdere teams aan boord:

• Team vissen: Tadzio Bervoets, Steve Piontek, Ingrid van Beek, met hulp van de crewleden Brett en Polly
• Team koralen en sponzen (benthos): Franck Mazeas, Jean-Philippe Maréchal, Ewan Trégarrot, Erik Meesters, Lisa Becking, Oscar Bos.
• Team NIOZ: Fleur van Duyl, Steven van Heuven, Xuewu Liu, Didier de Bakker, Alice Webb.

We doen in de 6 dagen 11 duikstekken aan. Om ervoor te zorgen dat de verschillende duikers geen last van elkaar hebben worden de teams verdeeld in 2 groepen. Als het vissenteam zijn werk heeft gedaan op een duikstek gaan de andere teams op dezelfde lokatie hun gegevens verzamelen. Ik begeef me afwisselend tussen groep 1 en 2 om alles te kunnen vastleggen.

Er volgden veel interessante gesprekken met de verschillende onderzoekers. Allen even aardig en even gemotiveerd om mij uit te leggen waarom ze bepaalde gegevens gingen verzamelen. Ik kreeg een kijkje in de keuken maar ik leerde ook meteen de teamleden kennen.

Het fotograferen en de gesprekken hebben me veel gebracht. Het was een rijke en leerzame ervaring waarbij ik op een nieuwe manier beeldmateriaal kon verzamelen.

Bedankt allemaal.

Saba Bank Expeditie: Erosie op de bank / Erosion on the Bank

Woensdag 21 oktober
Alice Webb

Alice en Didier aan het werk tijdens de meting (foto: David Stevens)

Mijn werk op de Saba bank is echt leuk. Mijn begeleider Didier Bakker (IMARES) en ik willen weten of de koraalriffen hier gezond zijn. Met de hulp van Steven van Heuven (NIOZ) duiken we in water vol met haaien en meten sponzen die in het koraal boren. Je vraagt je af waarom wij geïnteresseerd zijn in deze dingen? Nou, de moeders en neefjes van Oscar, Lisa en Steven lezen mee. Voor jullie, een beetje context, omdat jullie het anders misschien niet snappen.

Boorspons (Foto: Didier de Bakker)

Coral reef systems worldwide exist in a dynamic balance moderated by various processes resulting either in carbonate production or in the breakdown of previously deposited skeletal carbonate. Corals represent the primary constructional components on many reefs whilst bioeroding agents such as sponges, bivalves and worms directly degrade the reef’s framework increasing their susceptibility to physical and chemical erosion. Ongoing ocean acidification causes major shifts in species composition generally assumed to result in a shift in the growth/erosion balance.  Determining the relative role of these different processes is therefore crucial to conceptualise and quantify reef geomorphic performances.

By joining the Saba bank cruise, we aim to find out if the reefs of this gigantic submerged atoll are shifting towards net erosion instead of net growth. Using the ReefBudget method, we record calcifying and bioeroding species along fixe transects while diving.

Three days into the cruise, we have already dived 7 sites and recorded data along 21 transects. Each site very distinct from the other. Some reefs present high densities of bioeroding sponges while others harbour healthy coral populations. Many sites still await us and we look forward to analysing our data and determining the state of Saba Bank coral reefs.

Nou, ik ben klaar met mijn verhaal; ik hoop dat jullie het leuk vinden. Morgen is er iemand anders aan de beurt, ik denk jouw moeder, Roose. Je vous souhaite à tous et à toute une merveilleuse lecture. La vie à bord nous sourit et nous mangeons comme des rois.

Bon vent!

Saba Bank Expeditie: Hamerhaai in de vissurvey!

Ingrid van Beek
Dinsdag 20 oktober

Het vissurvey team bestaat uit 6 personen, die als eerste te water gaan om de visgemeenschappen op de Sababank te inventariseren: 3 duikers leggen ieder een transectlijn uit, achter de onderzoekers aan zwemmend om de vissen niet te verstoren; 3 onderzoekers noteren aantal en lengte van 100 vissoorten in een zogenaamd ‘belt transect’ van 50 meter lang en 5 meter breed. Het is belangrijk dat de transectlijnen recht en op de juiste plek liggen, want het benthos team gebruikt ze daarna om koralen en andere soorten bodembedekking onder de lijn te fotograferen.

Op de eerste duikdagen werd het vissurvey team onder aan de ankerlijn steeds verrast door een verpleegsterhaai die nieuwsgierig om de duikers heen zwom. Mogelijk verwachtten ze een lekker hapje, want op dit deel van de Saba Bank plaatsen vissers regelmatig lobster traps (kreeftenkooien) voorzien van aas. Het is opvallend dat er tijdens deze expeditie meer haaien gezien worden dan bij eerdere expedities. Bij praktisch ieder duikstation wel een of meer soorten, van verpleegsterhaaien en Caribische rif haaien tot een 3 meter lange hamerhaai! Scalloped en Great Hammerheads zijn pelagische haaien, die soms het rif opzoeken en soms ook duikers benaderen. Aan het eind van het transect kwam de hamerhaai op ons af en boog af toen hij op ongeveer 5 meter afstand was. Van opzij was de bijzondere kop goed zichtbaar, waarna hij helaas uit het zicht verdween voor we een foto konden maken.

Veel voorkomende vissoorten in de transecten zijn parrotfish (papegaaivissen), groupers (zeebaarsen, waaronder ook de grotere soorten zoals de Nassau Grouper en Yellowfin Grouper) en andere roofvissen zoals jacks (horsmakrelen) en barracuda.

Na afloop van de expeditie zullen de visdata vergeleken worden met die van voorgaande jaren om te bepalen of er een significant verschil is in de tijd en per station en of er een relatie is met de benthos en complexiteit van het rif.

Saba Bank Expeditie: Sharks on the Saba Bank

Monday 19 Oct 2015:
Tadzio Bervoets

I am typing this blog entry on a live-aboard dive boat that for two weeks has been transformed into a bonafide research expedition ship. Ordinarily I am manager of the St. Maarten Nature Foundation, which is the organization that manages the Man of War Shoal Marine Protected Area on Sint Maarten. But for the past three days and for the next three days to come myself and sixteen of my colleagues are inventorizing and mapping one of the world’s largest submerged coral atolls, the Saba Bank.

My specific job, together with my colleagues Ingrid van Beek of IMARES and Steve Piontek of the Statia Fisheries Department, is to conduct underwater fish transacts, which is a fancy word for doing fish counts along a fifty-meter length of tape at various depths and at various locations on the Saba Bank. We look for various species ranging from conch to grouper, snapper to damsel fish and from chromis to what is undoubtedly everyone’s favorite: sharks.

The presence and management of sharks on the Saba Bank is of close personal importance to me: I am also chair of the Dutch Caribbean Nature Alliance Shark Project which, with the support of the Dutch National Postcode Lottery, has embarked on conserving sharks on all six islands of the Dutch Caribbean.

On the 1st of September 2015 Dutch State Secretary Sharon Dijksma declared the EEZ of Bonaire and Saba, which includes the Saba Bank, as a shark and marine mammal sanctuary. The area, called the Yarari Sanctuary after the Arawak Indian word for a ‘fine place’, is committed to the effective protection of sharks and rays on the Saba Bank and during this expedition we have seen no shortage of them. On almost every dive we’ve had them come to check out what we were doing in their underwater kingdom.

Nurse shark  
But there is still work to do. During some monitoring dives we noticed sharks caught in lobster and fish traps, reinforcing the need to work with local stakeholders, and especially with fishermen, in ensuring that these globally threatened animals are protected and conserved.

It is now almost nine in the morning; time for the first dive of the day! The weather has been excellent with very calm conditions, unusual for the Saba Bank. We are all excited and ready to do our science and to record very important data on fish populations. And there is no better place I would rather be than right here with my fellow researchers and the excellent crew of the Caribbean Explorer, getting to know this beautiful and mythical part of the Caribbean Sea; the Saba Bank.

Tadz Bervoets

 Nurse shark trapped in lobster trap

Saba Bank Expeditie: Op weg naar Sint Eustatius

Zaterdag 17 okt 2016.
Door: Oscar Bos

Welcome on board! De zongebruinde purser Rob met een Londense tongval sjouwt de tassen de Caribbean Explorer op. Al 10 jaar zwerft hij over zee in de Caribbean en geroutineerd als hij is, kent hij binnen 1 minuut alle namen van de wetenschappers aan boord. De fles koude wijn staat aanlokkelijk op de bar, bier staat in de koelkast, de bedden zijn strak opgemaakt, afgetopt met een welkomstchocolaatje. Het lijkt verdorie wel vakantie.

Maar we zijn hier voor serieus werk en vergis je niet, vanaf vanochtend 5:30 uur ben ik, nog onder invloed van de jetlag, druk bezig met de voorbereidingen: de sponzendatabase testen, minuscule plastic cupjes nummeren voor het DNA werk, labels knippen. Expeditieleider Erik test de GPS en camera en laat me de kaarten van de Sababank zien: een groot halfrond rif, 20 meter op z’n ondiepst.

Tijdens ons ontbijt jaagt een prettig regenbuitje de toeristen onder de parasols. Terug in de hotelkamer schuilen we zelf voor een opgefokte man die geheel tegen zijn zin door een vijftal politiemannen gearresteerd wordt. Ik beschouw de muur tussen onze kamer en de hal als onze eigen kogelvrije afscheiding, wel spannend om wat van die vermaarde onderwereld mee te pikken. Tussen het geschreeuw klink de bezwerende stem van de receptioniste ‘Relaxssss! Relaxsss!’. Misschien waren we getuige van een mislukte drugsdeal, je weet het niet. En het wordt langzaam weer stil. 16:00 uur: we zetten koers naar Sint Eustatius (Statia) om de rest van het team op te pikken. Rond het schip duiken de bruine genten naar vis, terwijl de zon langzaam zakt en de sterrenhemel tevoorschijn komt. Er gaat heel veel gebeuren deze week.

Lisa en ik gaan ons op de biodiversiteit van sponzen storten, waarvan er momenteel 81 soorten bekend zijn op de Sababank. Ingrid en een aantal Franse collega’s tellen vissen en koralen langs een 50 m lange lijn. Ewan uit Martinique bekijkt de complexiteit van het rif, Erik maakt elke meter een foto van het koraal en de bodemdieren. Fleur tenslotte kijkt naar de fosfaatfluxen door sponzen op het rif en gaat CTD profielen nemen om de watertemperatuur en zoutgehalte te meten. De koraalspecialisten maken zich ernstig zorgen over het koraal, omdat het water dit jaar extreem warm is: nu al rond de 30 graden. Daarboven treedt bleaching op, waarbij de symbiotische algen, die in koralen zitten en ze van voedsel voorzien, het weefsel verlaten en kan het rif afsterven.

De crew aan boord bestaat uit een stelletje fraaie avonturiers, die maanden of jaren op dit duikschip zitten. Allemaal zijn ze ook duikspecialisten. De Canadese zeevrouw Polly maakte ooit een onderwaterontmoeting tussen een visserschip en twee gigantische ‘barrel sponges’ mee. Deze olievatvormige sponzen zijn zo groot dat je er als duiker geheel in past. De visserslijn tjopte ze doormidden, en de halve bovenkanten daalden kansloos op het aanpalende rif. Polly had een briljantje ingeving: ze puzzelde de geamputeerde reuzensponzen terug en hield daarna bij hoe het ze verging. Een paar weken later was het alsof er nooit iets gebeurd was: een paar littekens rijker deden de sponzen gewoon hun ding. Dus van ons kleine DNA monstertje zullen de sponzen op de Sababank niet veel last hebben. De nacht brengen we door langs de kade op Sint Eustatius, waar de overige wetenschappers aan boord komen. De groep is compleet, zondag kan het echte werk beginnen.

Oscar Bos

Saba Bank expeditie van start

De expeditie is bijna begonnen. Gisteren om 4:00 werd ik opgehaald en samen met Ingrid naar Schiphol gebracht. Beetje vroeg en zo’n nacht slaap je nooit goed. Op schiphol voegden zich 5 andere teamleden bij ons. De rest komt morgen op Sint Maarten aan of stapt aan boord op St. Eustatius (Statia). Een goede vlucht gehad met de KLM en voor de middag landen we op St. Maarten waarbij je ongeveer de handdoeken van het strand wegblaast als je landt (badgasten kunnen ook beter maar niet te hoog springen als er een vliegtuig landt).

Met een taxi die meer bagage bevatte dan mensen, naar een klein hotel op front street gereden. Dicht in de haven waar we onderzoeksschip de Caribbean Explorer (zie de foto links) al zagen liggen. Hij was net binnen.

De crew moet inkopen doen om de boot weer van proviand voor de volgende week te voorzien. Veel rust krijgen ze niet, want om 15:00 uur vanmiddag mogen we aan boord.

Wordt vervolgd...