Although bioluminescence (BL) in the open ocean has been extensively studied, coastal BL remains poorly understood due, in large degree, to a lack of BL instrumentation appropriate to measure the fine-scale biological and physical complexity of the coastal regime. As a contribution toward understanding coastal BL, we developed the Multipurpose Bioluminescence Bathyphotometer (MBBP). This compact, self-contained bathyphotometer (BP) was designed to function in a variety of deployment modes, including conventional shipboard profilers, towed platforms, autonomous underwater vehicles (AUVs), and profiling moorings. In all configurations, the instrument preserves signal structure at centimeter to meter scale resolution, the scale at which higher-flow instruments might disturb thin layers and other fine-scale water column features. In the MBBP, seawater is conveyed with minimal premeasurement excitation into a light-baffled stimulation and measurement chamber at a continuously measured flow rate of 350 to 400 mL s -1. A photomultiplier tube (PMT) records light from bioluminescent organisms after they are mechanically stimulated at the chamber entrance by a high-velocity impeller. Calibration and test protocols were developed to determine BL stimulation efficiency and MBBP measurement characteristics. To illustrate the capabilities of the MBBP to resolve the fine-scale structure of the BL community, measurements from two coastal environments are presented.

a b s t r a c tEcosystem function will in large part be determined by functional groups present in biological communities. The simplest distinction with respect to functional groups of an ecosystem is the differentiation between primary and secondary producers. A challenge thus far has been to examine these groups simultaneously with sufficient temporal and spatial resolution for observations to be relevant to the scales of change in coastal oceans. This study takes advantage of general differences in the bioluminescence flash kinetics between planktonic dinoflagellates and zooplankton to measure relative abundances of the two groups within the same-time space volume. This novel approach for distinguishing these general classifications using a single sensor is validated using fluorescence data and exclusion experiments. The approach is then applied to data collected from an autonomous underwater vehicle surveying 4500 km in Monterey Bay and San Luis Obispo Bay, CA during the summers of [2002][2003][2004]. The approach also reveals that identifying trophic interaction between the two planktonic communities may also be possible.

As part of Hyperspectral Coupled Ocean Dynamics Experiment, a high-resolution hydrographic and bio-optical data set was collected from two cabled profilers at the Long-Term Ecosystem Observatory (LEO). Upwelling-and downwelling-favorable winds and a buoyant plume from the Hudson River induced large changes in hydrographic and optical structure of the water column. An absorption inversion model estimated the relative abundance of phytoplankton, colored dissolved organic matter (CDOM) and detritus, as well as the spectral exponential slopes of CDOM and detritus from in situ WET Labs nine-wavelength absorption/attenuation meter (ac-9) absorption data. Derived optical weights were proportional to the parameter concentrations and allowed for their absorptions to be calculated. Spectrally weighted phytoplankton absorption was estimated using modeled spectral irradiances and the phytoplankton absorption spectra inverted from an ac-9. Derived mean spectral absorption of phytoplankton was used in a bio-optical model estimating photosynthetic rates. Measured radiocarbon uptake productivity rates extrapolated with water mass analysis and the bio-optical modeled results agreed within 20%. This approach is impacted by variability in the maximum quantum yield (Ф) and the irradiance light-saturation parameter (Ek (PAR)). An analysis of available data shows that Фmax variability is relatively constrained in temperate waters. The variability of Ek(PAR) is greater in temperate waters, but based on a sensitivity analysis, has an overall smaller impact on water-column-integrated productivity rates because of the exponential decay of light. This inversion approach illustrates the utility of bio-optical models in turbid coastal waters given the measurements of the bulk inherent optical properties.

The majority of organic carbon in the oceans is present as dissolved organic matter (DO~f); therefore understanding the distribution and dynamics of DOM is central to understanding global carbon cycles. Describing the time-space variability in colored dissolved organic matter (eDOM) has been difficult, as standard spectrophotometric methods for eDOM determination are laborious and susceptible to meth· odological biases. Previously, measurements of eDOM absorption in discrete water samples by use of a liquid·waveguide capillary cell (LWCC) compared favorably with measurements made with a benchtop spectrophotometer. Given this, we focused on automating the LWCC technique to improve our spatial and temporal sampling capabilities for eDOM. We found strong correlations between CDOM absorp tion spectra collected from discrete water samples using standard methods and selected corresponding CDOM spectra collected by the automated LWCC system. The near-continuous measurements by the LWCC system made it possible to map the temporal, spatial, and spectral variability ofCDOM absorption along the ship track.