OS12A-01 10:20h
Observed Response of the Hudson River Plume to Wind Forcing
One objective of the May 2004 pilot study for the Lagrangian Transport and Transformation Experiment (LaTTE) was to determine the relative advantages of studying the Hudson River plume within the spatial and temporal context provided by a research-friendly coastal ocean observatory. Towards this end, a shelf-wide observational backbone was locally enhanced with high-resolution relocatable systems in the New York Bight apex. The permanent backbone includes local acquisition of international satellite ocean color imagery, a network of long-range High Frequency radars, and a cross-shelf Endurance line occupied by an autonomous underwater glider. The higher resolution HF Radar, glider and mooring network was originally deployed in the vicinity of the Long-term Ecosystem Observatory, where it attracted a large number of scientists to coastal upwelling experiments conducted offshore Tuckerton, NJ from 1998-2001. With scientific interest in the series of coastal upwelling experiments having peaked and run its course through the publication phase, the high resolution systems were moved to the New York Bight Apex to hopefully repeat the cycle of attracting a variety of scientists to a specific interdisciplinary process study site. During the LaTTE pilot study, datasets from the nested observation network were assembled in real-time at a shore-based acquisition center, and high-resolution atmospheric forecasts were performed. Specific emphasis was placed on communicating the real time observatory data and forecasts to scientists on a pair of research vessels conducting a dye release with the associated physical, biological and chemical sampling. Observational results from the observatory will be reviewed, with specific emphasis placed on the observed response of the Hudson River plume to a windshift from upwelling to downwelling favorable winds in the middle of the pilot experiment. This includes a shift from a relatively weak plume flowing eastward along the south shore of Long Island to a much more distinct plume flowing southward along the New Jersey coast. The observatory results provide a spatial and temporal context for viewing the LaTTE dye release, chemical and biological results.
http://marine.rutgers.edu/cool/latte/
OS12A-02 10:35h
Dye Tracer Experiments in the Hudson River Plume During LaTTE\#1, May 2004
During LaTTE \#1 (LAgrangian Transport and Transformation Experiment), in May 2004, a tracer experiment using Rhodamine dye was conducted to study the circulation and mixing in the Hudson River plume. The experiment consisted of two (28 kg) injections of Rhodamine-WT into the surface mixed layer of the plume. The dispersing dye patch was monitored in situ with a Chelsea Ltd. Aquatraka III fluorometer attached to an undulating Eco-shuttle for 1.2 and 2.2 days after the first and second injections respectively. Persistent upwelling winds prior to and during the first experiment drove the plume to the east along Long Island's South Shore. When winds shifted to downwelling a new plume quickly set-up along the New Jersey coast and propagated down shelf at speeds exceeding 50 cm/s. The second injection occurred in the leading edge of the new plume. Several aspects of the dye's behavior appear to be inconsistent with the expected Ekman response to downwelling winds. In particular, after injection the plume remained thin, dye penetrated into the halocline, and the salinity of the leading edge of the dye-patch increased rapidly. In contrast, Ekman theory would have predicted a landward movement of the dye and a thickening of the plume. Furthermore, the rapid salting of the plume during downwelling-favorable wind conditions differs from numerical results of Fong and Geyer. We speculate that time-dependency may play be an important factor in the early evolution of the plume's structure, circulation and mixing.
OS12A-03 INVITED 10:50h
Dissolved Organic Matter in the Hudson River Plume
As part of the LATTE (Lagrangian Transport and Transformation Experiment) program, dissolved organic carbon (DOC), total nitrogen (TN), and chromophoric dissolved organic matter (CDOM) were measured in the Hudson River Estuary and Plume. As revealed by high resolution measurements from the Integrated Coastal Observation System (ICOS), dissolved organic matter has several sources within the estuary including the Hudson and Raritan Rivers, and a yet unidentified anthropogenic source off Manhattan. The quantity of dissolved organic matter that is exported from the Hudson River Estuary is significantly greater than that which the Hudson River can supply by simply conservative mixing with coastal seawater. In May, 2004, rhodamine dye was injected at the surface as the plume flowed out onto the New York/New Jersey shelf, once as the plume turned north towards Long Island, and once as the plume flowed south along the New Jersey coast. The ECOShuttle (a towed-undulating vehicle) carrying a rhodamine fluorometer was able to track these dye patches. An examination of dissolved organic matter transformations that occurred over these two to two and one-half day Lagrangian experiments will be discussed. In addition seasonal distributions of dissolved organic matter distributions will be presented from cruises in June 2003, June 2004 and September 2004 under different river flow and wind conditions.
OS12A-04 11:05h
Trace Metals and Nutrients in the Hudson River Buoyant Plume
In order to determine the spatial distribution and biological impacts of contaminant metals and nutrients associated with the Hudson River buoyant plume, the transport and transformations of mercury, other trace metals, and major nutrients are being measured as part of the LaGrangian Transport and Transformation Experiment (LaTTE). Beginning in the spring of 2004, a series of dye patch experiments will be carried out that will include continuous underway chemical and biological sampling within the well-sampled framework of an operational ocean observatory. During the first experiment in May 2004, surface water samples for dissolved and suspended particle concentrations of mercury, monomethylmercury, and bioactive and non-essential trace metals were collected using a trace metal clean, underway sampling system. A semi-continuous (5 min resolution) record of dissolved gaseous mercury (elemental mercury) in surface waters revealed diurnal patterns of mercury reduction and volatilization. The results of this project will improve predictions of contaminant movements and ecosystem impacts within the Middle Atlantic Bight.
OS12A-05 11:20h
Tidal Mixing and Buoyancy Advection: Joint Influences on Lobster Distribution in Coastal Maine
The Eastern Maine Coastal Current (EMCC) flows southwestward from the mouth of the Bay of Fundy to Penobscot Bay on the central Maine coast. Maximum non-tidal surface speeds reach 20-30 cm/s about 20 km offshore during April-May when the outflow from the Saint John River is strongest. Vigorous tides cause strong vertical and horizontal mixing, so that dispersal of neutral particles is influenced both by advection and tidal mixing. To survive, planktonic lobsters carried southwestward in the surface flow must settle to a nearshore cobble substrate. Larvae hatched near the Bay of Fundy can be advected to the central coast in 2-3 weeks, roughly the time needed to reach settlement stage. Over the same period, transverse tidal mixing is sufficient to raise nearshore larval concentrations to about half that offshore in the axis of the EMCC. Both processes may be necessary to explain the observed lobster distribution, which exhibits a distinct maximum in the central coastal region. The seasonal development of the EMCC is also influenced by winds and the larger circulation of the Gulf of Maine. This work is part of a multidisciplinary synthesis study funded by the NOAA Coastal Ocean Program.
OS12A-06 11:35h
Contrasting inherent optical properties and carbon metabolism between five northeastern (USA) estuary-plume systems.
We have recently developed the ability to rapidly assess surface inherent optical properties (IOP), oxygen concentration and pCO2 in estuarine-plume systems using flow-through instrumentation. During the summer of 2004, several estuarine-plume systems were surveyed which include the Pleasant (ME), Penobscot (ME), Kennebec-Androscoggin (ME), Merrimack (NH-MA) and Hudson (NY). Continuous measurements of surface chlorophyll and colored dissolved organic carbon (CDOM) fluorescence, beam attenuation, temperature, salinity, oxygen and pCO2 were taken at each system along a salinity gradient from fresh water to near oceanic endmembers. CTD and IOP profiles were also taken at predetermined surface salinity intervals. These were accompanied by discrete determinations of chlorophyll (HPLC and fluorometric), total suspended solids (TSS), dissolved organic carbon (DOC) and alkalinity. IOP data were calibrated using chlorophyll, DOC and TSS data to enable the retrieval of these constituents from IOP data. Considerable differences in the data sets were observed between systems. These ranged from the DOC-enriched, strongly heterotrophic Pleasant River System to the high-chlorophyll autotrophic Merrimack River System. Using pCO2 and oxygen saturation measurements as proxies for water column metabolism, distinct relationships were found between trophic status and inherent optical properties. The nature of these relationships varies between systems and is likely a function of watershed and estuarine attributes including carbon and nutrient loading, in-situ production and related autochthonous inputs of DOC and alkalinity. Our results suggest that IOP data may contain significant information about the trophic status of estuarine and plume systems.
OS12A-07 11:50h
High resolution coral records of reactive and micronutrient trace metals: Monitoring biological responses to flood plumes.
The influences of flood plumes on the coastal ocean are difficult to investigate because they are intermittent, transient and highly variable in nature. The application of trace metals in coral carbonates as proxy recorders of marine environmental conditions has been demonstrated as an excellent method for overcoming these difficulties. Coral records of trace metals have been widely used to provide historical records of physical impacts of flood plumes such changing salinity ($\delta$O$^{18}$), sediment load (Ba) and anthropogenic inputs such as heavy metal pollution (eg. Pb, Cd). Despite successful applications to physical properties, the use of coral records to monitoring the biologic responses to these changing environmental conditions has proved more difficult. With improvements in analytical techniques however, it is now possible to investigate coral records of reactive (rare earth elements) and micronutrient (eg Mn, Zn and Cu) trace metals, which can be used to more widely explore the biogeochemical implications of flood plumes to the coastal ocean. We have obtained high resolution temporal records of rare earth elements, Cu, Zn, Mn and Sn, from corals from two locations, (1) near Townsville on the Great Barrier Reef (GBR) and (2) Kaneohe Bay on Oahu, Hawaii. Both of these locations often display large phytoplankton blooms following flood events, providing a good opportunity to test the idea that coral records can be used to monitor the biological response to flood plumes. These coral records show significant responses to flood plumes that can only be attributed to biogeochemical cycling that occurs as a result of the flood plume influence, rather than the flood plume itself. Thus a mechanism for exploring the biological response to flood plumes is provided. It has generally proven difficult however, to interpret these coral records without a good understanding of the coastal processes. Therefore we also include evidence from direct trace metal measurements of a coastal Trichodesmium bloom on the GBR and data from experimental blooms using Kaneohe Bay seawater, induced by nutrient addition. Using this information we discuss the implications for the application of coral records to long term monitoring of biologic responses to flood plumes.
OS12A-08 12:05h
Large Phytoplankton Blooms Fuelled by Agricultural Runoff Into Especially Vulnerable Ocean Waters
In large areas of the ocean, primary productivity is controlled by supply of nutrients to surface waters. The relative balance between supply and removal of nutrients-such as nitrogen, phosphorus, and iron-determines which nutrient is most limiting to phytoplankton growth. Areas with high rates of microbial denitrification exhibit large nitrogen deficits relative to other nutrients. These regions are particularly vulnerable to inputs of nitrogen from other sources, as we demonstrate here for the Gulf of California, where nitrogen in agricultural runoff fuels large (54-577 km$^{2}$) phytoplankton blooms. Despite naturally high nutrient concentrations and rates of primary productivity agricultural nitrogen exerts a surprisingly strong and consistent effect on phytoplankton biomass, stimulating blooms only days after irrigation and fertilization of agricultural fields. Because these blooms can be transported rapidly over long distances, their ecological effects are likely felt across the Gulf. As fertilized agriculture intensifies and expands globally, these findings highlight the sensitivity of the world's oceans to runoff, particularly in the developing tropics and subtropics.