Join the 34th Rosenstiel Award in Oceanographic Science Recipient, Dr. Dennis McGillicuddy from Woods Hole Oceanographic Institution at the following events:

Welcoming Reception

Date: Monday, 21st of April 2008
Time: 5:00 p.m.
Location: Commons

First Seminar

Title: Oases in the Oceanic Desert: Turbulent Storms in the Sea and their Impact on Biological Productivity
Date: Tuesday, 22nd of April 2008
Time: 11:00 a.m.
Location: Slab Seminar Room (S/A 103)
Abstract:

Understanding the controls on biological productivity of the ocean is of fundamental importance for two main reasons. First, plankton productivity sets a first-order constraint on the energy available to sustain oceanic ecosystems. Second, formation and subsequent sinking of organic particles removes carbon from the surface ocean (the so-called “biological pump”), which plays a key role in partitioning of carbon dioxide between the ocean and atmosphere. New evidence suggests that the currents, fronts and eddies that comprise the “internal weather of the sea” could play a vital role in regulating ocean productivity. Turbulent storms in the interior of the sea can transport large quantities of nutrients from the deep sea into the well-lit surface layers, fueling massive profusions of plankton. Because they are so intermittent, such blooms largely escape detection by traditional oceanographic sampling techniques. Fortunately, new methods of synthesizing satellite data and computer models permit scientists to locate these areas in real time, making it possible to guide research vessels directly to where such events are taking place. The ability to effectively observe these highly episodic “oases in the oceanic desert” is leading to better understanding of their importance in the functioning of marine ecosystems and biogeochemical cycling.

Second Seminar

Title: Observations and models of harmful algal blooms (“red tides”) in the Gulf of Maine: from climatology to forecasting
Date: Wednesday, 23rd of April 2008
Time: 10:00 a.m.
Location: Slab Seminar Room (S/A 103)
Abstract:

Throughout the global coastal ocean, harmful algal blooms (HABs) are a serious economic and public health problem. In New England, the most serious HAB issue is paralytic shellfish poisoning, a potentially fatal illness that occurs when humans eat shellfish that have accumulated saxitoxins as they feed on the dinoflagellate Alexandrium fundyense. This organism has a complex life cycle, including a resting cyst that overwinters in bottom sediments and a planktonic vegetative phase during which blooms occur.

Climatological distributions of A. fundyense have been simulated by incorporating its population dynamics into a model of the seasonal mean flow. A model that includes germination, growth, mortality, and nutrient limitation is qualitatively consistent with observations. Cells germinated from cyst beds in the Bay of Fundy and offshore of mid-coast Maine are advected from east to west in the coastal current. Growth of vegetative cells is limited by temperature from April through June throughout most of the region, whereas nutrient limitation occurs in July and August in the western gulf. These factors cause the center of mass of the bloom to shift upstream in the coastal current as the season progresses.

In 2005, the western Gulf of Maine and southern New England were hit by the worst A. fundyense bloom to occur in at least 30 years. Numerical models have been used to hindcast this historic bloom and to investigate its causes. Sensitivity experiments distinguish the roles of three major factors: 1) high abundance of cysts in western Gulf of Maine sediments; 2) several strong storms with prevailing downwelling-favorable winds; and 3) anomalously large fresh water discharge entering the gulf due to abundant rainfall and heavy snowmelt. Our results suggest that high abundance of cysts in western Gulf of Maine was the main cause of the 2005 bloom.

These results suggest that cyst abundance could be a first-order predictor of overall bloom severity in the coming year. Observations in the fall of 2007 indicate cyst abundance off mid-coast Maine is 30% higher than it was preceding the historic bloom of 2005. Predictions for the 2008 bloom season will be discussed.