Saba Bank: hoe actueel is bescherming van de Saba Bank?

'Bleached' (verbleekt) koraal waarbij door het te warme zeewater het koraal zijn pigment (van de symbiont) verliest en door energiegebrek omkomt.

Koraalriffen over de hele wereld worden in hun voortbestaan ernstig bedreigd. Tegen het einde van deze eeuw wordt verwacht dat de riffen zoals we ze vandaag nog kennen zo goed als verdwenen zijn als we onze invloed op het milieu niet drastisch beperken. Is dat erg? Miljarden mensen wonen in de kustzone en met name in de tropen zijn ontzettend veel mensen afhankelijk van de vele diensten die het koraalrif levert. Voedsel, werkgelegenheid, kustbescherming om maar enkele te noemen.

De belangrijkste bedreigingen zijn vervuiling, overbevissing en klimaatverandering met als gevolg koraal'bleaching' en oceaanverzuring.

Lees hier de verklaring (engels) van de International Coral Reef Society (ICRS).

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