Chemical Oceanography Cruise (OS499A) is one of four cruise electives available to Marine Biology and Marine Science majors.  Minimal prerequistes encourage students at all stages of their degree programs to take the half-semester courses.  The variety of student interests and abilities in these courses in many ways mirrors those found on typical oceanographic research cruises.  

Students in a recent cruise course found answers to basic questions about sugars in Penobscot Bay waters.  Their measurements, quite possibly the first for Maine estuaries, applied a new technique¹ to a suite of cruise samples.  Students planned the cruise, did the sample collection, made supporting measurements at sea, and completed the laboratory analyses.  Professor Boucher taught the course and selected the topic since so little is known about monosaccharides (simple sugars) in coastal waters, despite their importance in the carbon cycle.  The measurements, challenging analytically due to ease of contamination, required students to develop good lab technique.  

What were the results? Read on to find out!

	After learning techniques and doing a "shake-down" cruise earlier in the semester, students confer to make a cruise plan.  The plan will be given to the Captain and will make the best use of valuable ship time.  Estimates of the sampling time required at each station and transit times were noted during the shake-down cruise.  Jesse Dalton, far left, uses MapTech software to plot station locations and check tidal conditions for cruise day. Belinda Teague (far right) readies filtration equipment for dissolved nutrients.
	Students decide the cruise will start at 7:30 AM (everyone on board at 7:00 AM!) and travel up eastern Penobscot Bay to the Penobscot River.  By approximately 1 PM, eight stations will have been sampled for a variety of water quality parameters.  The cruise track will revisit stations sampled in early summer and will, conditions permitting, span a salinity gradient from normal Bay salinities (~30 PSU) to freshwater.
	Cruise day -- perfect weather and flat seas.  Students (and instructor, working as directed by students) are too busy preparing for the first station to get pictures of setting up on deck.
	Sarah McCarthy and Jeremy Shambaugh prepare electrodes and warm up the fluorometer for the day's measurements below deck on the R/V Friendship.  They will measure the chlorophyll fluorescence, pH, and alkalinity of the samples brought to them by the deck team.  The fluorescence measurements will help identify zones of higher primary production (photosynthesis).  pH and alkalinity will help to chemically characterize the estuary's waters, and to identify the Penobscot River as the major freshwater source to the estuary.
	On deck, between Stations 1 and 2.  Station chiefs Jessica Clifford (behind CTD unit and barely visible) and Jay Marsh (right) record sample bottle information and prepare for Station 2.  At each station, the CTD is cast (using the winch wire visible in the image) to measure the water column salinity, temperature and density.  A transmissometer mounted to the CTD unit records the passage of light through water at different depths.  The data are used to identify regions of high biological activity and/or suspended sediments.  At Station 5 near the mouth of the Penobscot River, light transmission approached zero and the water was highly colored with dark sediments at many depths.  Belinda Teague (left) filters water samples.
	Jay Marsh points to harbor seals basking on a ledge near the mouth of the Penobscot River.  Within the hour, the flood tide will submerge the ledge and the seals will be swimming.  Jay's duties on deck included checking the Secchi depth at each station and measuring dissolved oxygen in the water samples.  The Secchi data will be used to show the maximum water depth for photosynthesis.
	Jessica Clifford watches the CTD enter the water.  The instrument is kept at the surface until it communicates electronically with a computer in the cabin a few minutes later.  A student watches the computer screen as data are received in real time from the instrument, and relays information about bottom depth to the winch operator.  Eight Niskin sample bottles (not visible) are also attached to the same frame (known as a "rosette").  These are "fired" by the computer to close at selected depths, enabling water samples to be retrieved from different depths.
	A successful cruise; the R/V Friendship heads to port on schedule. Meanwhile, students are busy making the last measurements at sea and stowing equipment.  In port, students will hose down the CTD and deck with fresh water.  They will also return equipment to the lab and store samples properly (for further processing or analysis). For homework, the original cruise data (CTD and transmissometry) are converted and "binned" to a new format for examination in a spreadsheet.  This process condenses the thousands of measurements the CTD and transmissometer take on a single downcast to just a few data points per meter of depth in the water column.
	In lab the following week, the class breaks into groups to prepare samples for monosaccharide analysis.  Jeremy Shambaugh (left) and Jesse Dalton pipet solutions into test tubes containing the cruise samples.  Afterwards, the samples with the most dissolved monosaccharides will be the most blue.
	Test tubes ready to be analyzed.  The absorbance of light by the cruise samples is related to their monosaccharide content.  Samples called "standards" containing known amounts of glucose, a monosaccharide, are processed with the samples.  The light absorbance of each standard is plotted against concentration and the graph is used to determine the amount of monosaccharide in each sample.
	Sarah Austin and Jay Marsh record the light absorbance of their samples using a visible light spectrophotometer..
What do our analyses show? Samples from all depths are closely related to salinity -- the fresher the water, the higher the monosaccharide content.  The content of monosaccharides in surface waters is shown at right. Most likely, the Penobscot River is the major source of dissolved sugars to the estuary.	How do Penobscot Bay concentrations relate to those of other regions? Monosaccharide concentrations reported for offshore regions are typically 0-20 µM C; our values extrapolate to these amounts.  Our data fall within ranges found in the Elorn estuary in France (Senior and Chevolot, 1991).  They are slightly higher than in the Delaware Bay estuary at the same time of year (Witter and Luther, 2002).
???????	What's next?   Though the cruise course has ended, the study of sugars in Penobscot Bay will continue through projects and faculty research.  Our data suggest monosaccharides pass through the estuary largely unused -- further work will assess if that is a seasonal phenononym.  Additional measurements will also quantify the total sugar content of these waters and their relationship to parameters such as chlorophyll, nutrients and pH. As more of these type of data become available to the scientific community, unresolved questions about the carbon cycle can be addressed.  As a student at the Corning School, you have the opportunity to contribute to the global scientific community!