All six of our aquanauts have now been living underwater for over two days and with that comes some getting used to as well as some very special experiences.
For the scientists on this mission, they have the luxury of time out on the reef to study how sponges change the surrounding water chemistry. They are sampling before dawn and up until midnight, and taking their time getting the measurements just right. And on this mission, they are also testing what may be one of the only and smallest underwater mass spectrometers in the world - a high tech instrument to measure a suite of substances in the water. For the scientists it is also a chance to observe the coral reef ecosystem around the clock and simply watch as conditions change and organisms interact. The Aquarius undersea habitat provides them time and access to the coral reef, a luxury most coral reef scientists can only dream of. Dr. Brian Popp says that so far what he enjoys the most is, “After dark the yellow tail snapper hang out right by the view port next to the dining room table and we can watch them feed. It is so cool to see little zooplankton trying to swim away and then bang, they become dinner. Really, though the science we get to do here is so unique that it is really the best part about Aquarius”.
Our habitat technicians work alongside the scientists in Aquarius to keep them safe, sound, and enable them to do their research. On this mission Mark and Larry are in Aquarius and working closely with a surface crew to monitor the life support systems, make sure everything is working properly, and keeping the habitat running smoothly (this usually includes a lot of scrapping or scrubbing of algae and other organisms that like to grow on the habitat). And taking a bit of time, I’m sure, to check out all those fish staring in at them - particularly that giant goliath grouper that has been hanging around.
For all of the aquanauts living undersea also comes with its challenges, from living in tight quarters with five other people to eating food under high pressure. Humor is a must when you are living beneath the waves. More on this in blogs to come as we check in with the aquanauts over the next few days.
Dr. Ellen Prager
Chief Scientist, Aquarius Reef Base
The day began at 04:15 today for Howard and I. The data collected by Team Aquarius with our underwater mass spectrometer during the September 2007 mission indicated some interesting diurnal variations, which showed oxygen uptake (respiration > photosynthesis) by sponges at night and oxygen production (photosynthesis > respiration) during the day. Respiration is greatest at about 05:00, so we suited up to collect some key samples while being cautiously watched by the nighttime denizens of Aquarius (nurse shark, goliath grouper, many way-cool snapper and the ever-present barracuda). When we returned we “cooked” freeze dried eggs for our breakfast burritos and added some hot sauce for a bit of a zing. Jim and Patrick followed us out at the crack of dawn and ended up staying out most of the day. Thanks to these guys, we now also have real-time physical data streaming into Aquarius that allows us to see variations in the rates of sponge pumping.
Patrick also today managed to “talk” over the internet with more than 70 elementary school children in western Dade County! He gave them a virtual tour of Aquarius on the inside while our Rolex Scholar (Brenna Mahoney – see the latest issue of SCUBA Diving magazine) gave a video tour of the outside. Jim has a hot date with a sponge at midnight tonight, but I’ll let him tell you all about it in his journal entry a bit later.
The most excellent Aquarius staff set-up the Navy Camera at one of our study sites so check out that new web cam link – look for Howard and I at 05:00 tomorrow.
Aloha, Brian
Splash down at 9:15 am this morning….. It was a bit rough top side but calm as a clam once we hit bottom. The whole day was devoted to setting up equipment. Things went well but I always find it amazing how a simple task like leveling a piece of equipment can take so long underwater. When all was said and done we had real time data streaming back into our little home. The day felt kind of short since I need to be back in by 5pm for we could get an early start tomorrow morning. (We all are required 12 hours of dry time every night for safety sakes) As the sun set it was really cool to watch the mass spec data change as we transitioned into night. Some of the masse changed as much at 1.5% in a little over an hour.
Howard signing off from 50ft below!
Coastal ecosystems are regions of remarkable biological productivity and diversity, yet they are among our most disturbed natural environments. Although many human activities cause change in the coastal zone, they occur against a background of natural change. Effective coastal-zone management requires that we identify and understand these separate causes of ecosystem change. This requires an understanding of the biogeochemical processes that sustain the natural resources of tropical and subtropical ecosystems. In this study we focus on marine sponges because they strongly effect nitrogen (N) cycling in coastal environments through pumping and filtering tremendous volumes of water while their hosted microorganisms affect a wide range of ecologically important N transformations. Our new in situ measurements of whole sponge respiration, water pumping rates, and chemical fluxes indicate that previous studies based upon enclosure or laboratory experiments can dramatically underestimate net fluxes and cannot provide data needed to establish actual net fluxes of dissolved inorganic nitrogen (DIN) and other N species.
The overall goal of our research is to quantify sponge impacts on coastal N cycles. Previous work has identified high rates of N transformations within sponge communities. These include nitrification (i.e., the chemolithoautotrophic conversion of ammonia to nitrogen oxides), dissolved/particulate organic N uptake and degradation, and potentially N2 fixation and denitrification (i.e., the bacterial-mediated respiration of organic matter using nitrogen oxides as electron acceptors in lieu of oxygen). Thus, marine sponges may be adding or subtracting bioavailable N from coastal systems. Our initial investigations of N cycling in sponges demonstrated that they play a major role in the N budget of coral reefs and other shallow water tropical ecosystems (see AQUARIUS Mission 4 August 15-24, 2005 and Mission 6 17-25 September 2007). This mission will examine the role of sponges in the coastal N cycle by (i) using in situ methodologies to construct accurate N budgets for sponges that will identify them as nutrient sources or sinks, and (ii) to examine environmental controls over sponge mediated N transformations. The net impact of sponges on biogeochemical N cycling in coastal environments is largely unknown. Our research program is the first to use in situ methods to quantify the nitrogen cycling in sponges and the resultant flux of DIN and dissolved organic nitrogen from sponges.
Of paramount importance in calculation of chemical fluxes in the oceans is linking the magnitude of the water flow transporting the chemicals with real time measurements of the substrates and products of biogeochemical reactions. During our mission, we will measure sponge excurrent pumping rates using acoustic Doppler velocimeters (ADVs) on a variety of sponge species. Our in situ data collected over the past three years have documented sponge pumping rates as great as 100,000 L seawater per day per L of sponge tissue, and sponge excurrent velocities > 25 cm/s. We will use newly developed underwater in situ membrane inlet mass spectrometry instrumentation that makes possible extremely sensitive and rapid measurements of N2, Ar, CH4, O2, CO2 and other trace gases. These data will be combined with discrete samples on which we will measure inorganic nutrient, total dissolved inorganic carbon, and nitrous oxide concentrations as well as the stable isotopic compositions of nitrate, nitrous oxide and total dissolved inorganic carbon. A major goal of our mission will be to compare pumping rate data of dissolved oxygen, total dissolved inorganic carbon, and various N species in the sponge excurrent plume vs. the concentration of these species in the ambient water surrounding the sponge. With these data we can measure the net chemical flux for several sponge species to determine the impacts sponges have on coastal N cycles.
We now recognize that sponges play a crucial role in the nutrient balance of coastal environments because they are abundant in tropical, temperate and polar habitats, they process tremendous amounts of water, and they can host abundant and active microbial populations. The impact of sponges on biogeochemical cycling in these environments however, is largely unknown. The information we collect on the sponge species living in proximity to AQUARIUS is likely to have broad implications for nitrogen biogeochemistry in coastal ecosystems with abundant sponges. This research is supported by the National Science Foundation (OCE-0624406 to Christopher S. Martens and Niels L. Lindquist and OCE 0624703 to Brian N. Popp) and NOAA/NURC through the Coral Reef Alliance.