SMSG Blog

We – Kostas and Frithjof – are the 2 botanists in the team, and we have been trying to assess and capture as much of Ascension’s diversity in terms of seaweeds (macroalgae) as possible during this expedition. Due to a clash of timing with other, similar work in Greece in August, we only came here on Sept. 3, but we are also staying about 9 days longer than the other team members.

The first thing that strikes any diver is that Ascension has a heavily fish-dominated coastal marine ecosystem. Most of the seabed looks rocky without any seaweeds. So where are the algae?

Well, there must be algae in the system – they ultimately produce the biomass and energy to sustain this impressive abundance of animal life. It is not clear at the current time what respective contributions benthic and planktonic algae make to sustaining the coastal marine food web, but it is obvious that the turnover of algal biomass in either case has to be very high. In other words, they probably grow very fast, and they also get eaten (grazed) very fast.

The most common fish species around Ascension is the black triggerfish, which is omnivorous – which means that it also grazes most types of fleshy seaweeds. This species is clearly one of the main suspects for grazing most seaweeds to (almost) invisibility.

[caption id="attachment_665" align="aligncenter" width="584"] Grazing black triggerfish. Just in a footnote, we also witnessed cannibalism by Black Triggerfish, they even eat their own, dead mates


[caption id="attachment_666" align="aligncenter" width="584"] Sleeping black triggerfish.

Still, despite the voracious triggerfish, we found a rather rich seaweed flora, just over 70 species in about 2 weeks of intense searching and collecting, including almost 20 new, previously unrecorded taxa. Most of them are either very small (in the open sea around Ascension) due to the strong grazing pressure, typically occurring in small turf-like mats. Larger seaweeds can only be found in places were grazers can’t fully exert their pressure – in particular, in intertidal rock pools and in swell zones.

[caption id="attachment_667" align="aligncenter" width="628"] The green alga Neomerys in a coralline community.

There is one exception to the above – calcareous red algae (coralline red algae) actually dominate much of Ascension’s seabed ecosystem, covering large surfaces and constituting structuring elements to the seabed communities and landscape. Due to their solid calcium carbonate skeleton, they are unpalatable to grazers, and they somewhat fulfil the reef-building role that corals play in many other tropical marine areas around the world. They either form loose piles on the seabed (maerl - rhodoliths), or beautiful, tower- or coral-like, reef-forming structures. Corals have indeed a very cryptic existence around Ascension, and it is not clear to date why that is the case. There are only few experts for coralline red algae in the world (neither of the 2 of us are). We will join forces with two of them, Rafael Riosmena-Rodriguez in Mexico and A. Athanasiadis in Sweden, for identifying the many samples of coralline red algae collected during our dives.

[caption id="attachment_668" align="aligncenter" width="628"] Coralline red algae forming tower- or reef-like structures during a night dive in English Bay, Sept. 4

Time and facilities during expeditions like this one are always severely limiting factors. In other words, a visiting investigator may easily miss some of the algal biodiversity in a place like Ascension either because it is too small, or outside its growing season. For this reason, we have collected many substratum samples (fragments of sea shells, sand, coralline red algae) in sterile tubes which will be incubated under suitable culture conditions in the laboratory of Frithjof’s friend Akira Peters in Roscoff. Over the following months, Akira will monitor them for algal outgrowth and obtain unialgal isolates (i.e. only one algal strain at a time). By experience, this approach captures a number of taxa usually inaccessible or unavailable during the fieldwork. Our list of around 70 macroalgal taxa around Ascension may still get longer for a while after returning to Europe!

- Contributed by Frithjof C. Kuepper (Oceanlab, University of Aberdeen, Scotland) & Kostas Tsiamis (Hellenic Centre for Marine Research, Greece)

The team returns to Shelly Beach

We mentioned in one of our early posts that two of our team members had been fortunate enough to be shown a very special site here on Ascension, the small rock pools at Shelly Beach where two very rare and vulnerable species of shrimp are found.

Yesterday a large number of the team enjoyed a return visit to the pools, escorted by Stedson Stroud and Jolene Sim of Ascension Conservation. This time we were loaded with all the equipment we would need for a survey of the site, including underwater cameras, devices to measure salinity and temperature, GPS units to map the site and, most excitingly, special permission by the Ascension Island Government to collect a small number of samples for further study.

Enjoy this short gallery of images taken at this exceptional location.

[gallery orderby="title"]

Last night the Ascension Island community were invited to a presentation by the team about their previous work in Falklands and South Georgia, as well as talks about the current expedition.

The talk was held in the Saint's Club, here in Georgetown, which is one of the centres of night-life in this small town. It's a great place to unwind at the bar, have lunch or watch a game of skittles!

Everyone enjoyed the images of undersea life, some of which have already been loaded to this blog as well as some detailed information about some of the methods we are using to capture some animals for further study.

Throughout our stay in Ascension the group has very much appreciated the great interest in the expedition by island residents. As we reluctantly prepare to leave soon, we remind all that anyone who would like to chat about the project will be most welcome to corner any member of the team while we're still here!

[caption id="attachment_559" align="aligncenter" width="584"] Paul Brickle introduces the talk with some information about the work of the Shallow Marine Surveys Group.


[caption id="attachment_562" align="aligncenter" width="584"] Peter Wirtz entertaining the audience with an impromptu talk about the various animals found in Ascension waters.


[caption id="attachment_561" align="aligncenter" width="584"] Simon Morley provides details about his settlement plate experiments.


[caption id="attachment_560" align="aligncenter" width="584"] Jude Brown explains the survey methods used by the team to count sealife underwater.


 

[caption id="attachment_563" align="aligncenter" width="584"] Frithjof Kuepper wraps up the presentation with some information about the search for new algal species.


 

Ascension Island – a lonely piece of land in a seemingly borderless ocean turned out to be the centre of an oceanographic 'collision'  which does not happen very often in featureless seas. Here, the central branch of the Southern Equatorial Current that normally goes on surface meets the Southern Equatorial Counter-Current that normally goes in subsurface layers but right here, between 7 and 8°S, it travels to the surface. Interactions of these two streams give rise to high water turbulence, numerous gyres and eddies and other kinds of water unrest. Those, combined with upwelling areas in inshore waters caused by the bottom topography, are responsible to the high productivity of the area that attracts numerous large predators close to shore that might be seen filleted on Georgetown pier almost every night.

[caption id="attachment_547" align="aligncenter" width="584"] Getting picked up by our research vessel for the circumnavigation of the island, the Queen of Atlantis.

To study the local oceanographic features, a total of 16 oceanographic stations with manually deployed CTD (Conductivity – Temperature – Density) devices were carried out. To complete the picture around the island, Vlad Laptikhovsky, Steve Cartwright, Wetjens Dimmlich, Frithjof Kuepper and Kostas Konstantinos circumnavigated Ascension in the comfort of the Queen of Atlantis. Generally conditions in the voyage were good but did become quite rough along the more exposed coast near Boatswain Bird Island.

The results reveal a complicated oceanographic structure even in the upper 50-m layer, where waters of both the major oceanic currents combined with a mixed layer of local origin.

[caption id="attachment_548" align="aligncenter" width="584"] Vlad deploying the CTD during the 4-hr trip around Ascension.

During the past two weeks the interaction of these currents was quite mobile. The cold productive Counter-Current eventually occupied the surface layer around most of the island, excluding the small offshore part in the north around English Bay. The more saline (because of evaporation) Equatorial Current moved its water mostly deeper than 20 m revealing expected phenomenon of temperature increase with depth, and surfaced only in the very north of the studied area.

- Contributed by Vladimir Laptikhovsky

[caption id="attachment_169" align="alignleft" width="300"] Prof. Frithjof Kuepper
University of Aberdeen, Scotland.

Frithjof has recently been appointed to the Chair in Marine Biodiversity at the University of Aberdeen, after previous appointments at the Scottish Association for Marine Science (SAMS; initially as Lecturer and Head of the Culture Collection of Algae and Protozoa from 2003 until late 2008, then as Reader).

Over the past 20 years, he has studied the chemical ecology, physiology, biochemistry and biodiversity of aquatic and marine plants/algae, especially in the context of biotic / abiotic stress and biogeochemical cycles, resulting in the publication of 60 peer-reviewed papers and 3 book chapters.

At pre-university level, he won international recognition with First Prizes at the European Community Contest for Young Scientists and at the Young Europeans' Environmental Research Competition. He received a French-German Ph.D. on brown algal stress responses and pathologies (1998-2001), working at the CNRS – Station Biologique de Roscoff (France), the University of Konstanz and at the Université de Paris-Sud XI / Orsay, supported by fellowships of the German Academic Merit Foundation (Studienstiftung des deutschen Volkes) and of the European Commission (Marie Curie doctoral fellowship). He further studied the role of microbial metal chelators in marine ecosystems as a post-doctoral fellow at the University of California, Santa Barbara (2001-3), where he remained a visiting professor in the Dept. of Ecology, Evolution and Marine Biology (EEMB) until 2010.

Besides pathologies, he is interested in algal halogen metabolism and the atmospheric impact of algal halogen emissions. This work resulted in the first-ever description of an inorganic antioxidant in a living system, iodide in kelp, and was selected as one of the 100 Science Stories of the Year 2008 by DISCOVER Magazine.

He has conducted and participated in expeditions and field trips with a scope in phycological / marine research throughout the world, notably to the Shetland Islands, French Polynesia, Malaysia, Chile, Argentina, the Falkland Islands, Japan, California, Ireland, Greece, Cyprus, the Canadian Arctic, and, most recently, Antarctica (Adelaide Island) and Ascension Island.

He has been a member of the Editorial Board of Marine Biotechnology from 2004-2010 and he currently is a member of the Editorial Board of Algae, the Peer Review College of the UK Natural Environment Research Council, and he was a member of the Council of the British Phycological Society from 2004-2007. Frithjof is fluent in English, Modern Greek, French, and German.

Within the framework of this project in Ascension, Frithjof (jointly with Kostas Tsiamis) is particularly interested in establishing an inventory of Ascension’s macroalgae and in understanding some of the major questions of algal benthic ecology around Ascension, including why coralline red algae (rather than corals) dominate much of the benthos, and whether deeper parts of the euphotic zone of Ascension’s benthos might harbour kelp populations.