David A. Phinney

Photosynthetic Characteristics of Picoplankton Compared with Those of Larger Phytoplankton Populations, in Various Water Masses in the Gulf of Maine

AbstractCell numbers of eucaryotes and cyanobacteria in phototrophic picoplankton and ratios of in vivo fluorescence of phycoerythrin: chlorophyll a indicated that chroococcalean cyanobacteria played a more prominent role in phytoplankton communities, at the least productive stations. At stations displaying large vertical density gradients, subsurface maxima of phytoplankton pigments were observed. Ratios of in vivo fluorescence of phycoerythrin: chlorophyll a were always greater at the pigment maximum than at the surface. Cyanobacteria from pigment maxima demonstrated greater phycoerythrin fluorescence intensity and photosynthetic rates than cyanobacteria from the surface. Photosynthetic characteristics of picoplankton ( 3 μm populations. The picoplankton differed from larger phytoplankton, in that (1) their pattern of photosynthetic carbon fixation did not vary significantly with decreasing light intensity, and at optimal intensities ...

Monsoons boost biological productivity in Arabian Sea

Monsoons over the Arabian Sea—the oceanic basin that separates the Arabian peninsula from the Indian subcontinent—follow seasonal cycles, reversing directions twice a year, in summer and winter. Rather than spreading across the expanse of the sea, the southwest (summer) monsoon is often concentrated into a jet over the central Arabian Sea. Evidence suggests that variations in wind stress force substantial upwelling in the ocean to the west of the jet, and weaker upwelling or even downwelling to the east. This upwelling provides nutrients to the euphotic zone and enhances biological productivity.

Primary Productivity of Phytoplankton and Subtidal Microphytobenthos in Cobscook Bay, Maine.

Abstract Cobscook Bay is a shallow, biologically rich, geographically complex, macrotidal estuary located in eastern-most Maine. Seasonal measurements of light attenuation and microalgal biomass as water column phytoplankton and subtidal microphytobenthos were used to estimate primary production using a light and chlorophyll model. The Bay was found to be a high nutrient/low chlorophyll estuary characterized by intense tidal mixing. Seasonal patterns of biomass and productivity indicated a single peak in mid- to late summer that resulted from the growth limiting effects of water column temperature in spring and light availability in fall. Spatial patterns indicated elevated standing stocks in areas where the residence time of waters in the Inner Bay increased, allowing growth to exceed export due to tidal flushing. Site to site comparisons of average water column phytoplankton and subtidal microphytobenthic production demonstrated that suspended microalgae account for only one-tenth of the microalgal productivity of Cobscook Bay since attached microalgae can avoid advective processes and adapt to changes in light availability at short time scales. This example of a high nutrient/low chlorophyll estuary is used to reevaluate the concept of “new” production since nitrate is never limiting and ammonium is present at high concentrations throughout the year.

Adaptation to low photon flux densities in Protogonyaulax tamarensis var. excavata, with reference to chloroplast photomorphogenesis

Changes in cellular chlorophyll content, cell volume, and light scatter of a New England red tide dinoflagellate, Protogonyaulax tamarensis var. excavata (clone GT-429), cultured in various light regimes are reported. Individual cells were analyzed, using flow cytometry and compared to traditional bulk measurements. Compared to high photon flux densities (182 μEin m-2 s-1), changes were measured that reflected increased chlorophyll fluorescence and increased cell volume at reducec photon flux densities when cell division was sustained, and increased flourescence and decreased cell volume when cell division ceased. These optical changes were accompanied by conformational changes in the chloroplasts. We found no change in photosynthetic carboxylating enzyme activities. We suggest that this photomorphogenesis of the chloroplasts at low photon flux densities may be an indication of stress and survival vs adaptive value to these persistent cells.

Real-Time Characterization of Individual Marine Particles at Sea: Flow Cytometry

Oceanographers have always wrestled with the time-space dilemma. The enormity of the oceans and the manifold physical, chemical and biological processes compound to make ‘sampling’ in the oceanic realm an omni-present problem. For the most part, the oceanographer has been wed to the research vessel. This has heavily restricted and frequently determined experimental design. It is unlikely that measurements which are widely spaced in time and space will provide further fruitful information on the rate of processes in the oceans.

Yellow substances in the coastal waters of the Gulf of Maine: implications for ocean color algorithms

We believe that the coastal estuaries of the Gulf of Mexico during spring runoff are among the worst possible cases for the measurement of phytoplankton chlorophyll by satellite colorimetry. Five coastal sections were sampled during May, 1996, extending from the 100m isobath shoreward to the mounts of major rivers in the southern Gulf of Maine. Water columns were dominated by short wavelength absorbing materials of terrestrial origin which, like many coastal areas, are inversely correlated with salinity. Excluding water absorption which is negligible at short visible wavelengths, we have modeled the system using two major absorbers: dissolved yellow substances and particulates. In Gulf of Maine coastal waters during spring, 80-90 percent of the total absorption coefficient at short visible wavelengths is due to yellow substances. At salinities greater than 30 parts per thousand and at wavelengths longer than 450nm, the dominance of dissolved yellow substances decreases. In terms of remote sensing reflectance, the use of two wavelength ratio algorithms leads to disastrous overestimates of phytoplankton chlorophyll concentrations. On the positive side, this dataset will be useful for testing algorithms designed to retrieve phytoplankton chlorophyll from water leaving radiances measured at stations with high concentrations of colored dissolved organic matter.

The relationship between phytoplankton concentration and light attenuation in ocean waters

The accuracy of chlorophyll estimates by ocean color algorithms is affected by the variability of particulate attenuation; the presence of dissolved organic matter and the non-linear inverse relationship between the attenuation coefficient, K, and chlorophyll. Data collected during the Warm Core Rings Program were used to model the downwelling light field and determine the impact of these errors. A possible mechanism for the non-linearity of K and chlorophyll is suggested, namely, that changing substrate from nitrate-nitrogen to ammonium causes enhanced blue absorption by photosynthetic phytoplankton in oligotrophic surface waters.

Classification of boreal macrotidal littoral zone habitats in the Gulf of Maine: comparison of IKONOS and CASI multispectral imagery

Increasingly, remote sensing has become a useful tool for mapping and measuring terrestrial and aquatic environments. Advances in the spatial and spectral resolution of satellite-borne sensors have allowed affordable investigations of littoral macrotidal coastal systems that previously required more costly aircraft-based imagery. In this communication, we compare the results from analysis of a 4 m spatial resolution, multispectral IKONOS satellite image of the intertidal habitats of Islesboro, Maine, USA with that of an aerial compact airborne spectral imager survey of the same regions captured 4 years earlier. There was 72% agreement between the surveys in spite of the temporal gaps between the images. Accuracy varied by habitat class and the perceived error can be assigned to temporal and definitional issues rather than basic acquisition and analytic protocols. Most of the error can be explained by: (1) inadequacy of training sites, (2) temporal variations and (3) class definitions. We conclude that IKONOS imagery provides sufficient spatial and spectral resolution to map and monitor diverse intertidal habitats as found in the macrotidal Gulf of Maine.

Spectral diffuse attenuation of phytoplankton measured by the filter pad technique: are we on the right track?

The measurement of light absorption by photosynthetic microalgae is of concern to algal physiologists and plankton ecologists. Interest in this topic by algal physiologists originated with the measurement of quantum efficiency. Recently, plankton ecologists have also felt the need for accurate measurements of phytoplankton quantum efficiency within the submarine light field. In addition, the need for absorption measurements is pivotal to the development of algorithms for global remote sensing. The pioneering research in algal light absorption was done by physiologists such as Shibata and Duysens continued by Latimer and Butler. Their techniques were applied to natural phytoplankton populations by Kiefer and Yentsch. In the course of these developments we may have overlooked the essential problems of absorption measurements. The papers of Shibata and Duysens make the point that spectral definition concerns the ratio of absorption to scattering. The instrumental constraints associated with the measurement technique changes that ratio. It is unclear how much scattering is associated with the phytoplankton as opposed to the optical configuration. Perhaps our present methods are not realistic for optically characterizing natural waters. In this paper we compare spectral absorption measured in a configuration where absorption markedly dominates scattering to situations where scattering is a major component of attenuation. We have placed these extremes in the context of optical closure of light attenuation in natural waters.

Relationship Between Cross-Sectional Absorption And Chlorophyll Content In Natural Populations Of Marine Phytoplankton

We have measured the in vivo absorption of light (670 nm) by natural phytoplankton populations collected from a variety of locations in the North Atlantic Ocean. There is a strong correlation between chlorophyll content and absorption. By using a linear regression model the mean value for chlorophyll specific absorption (A*) is 0.0138. The range in this value is about .0100 - .0300. At chlorophyll concentrations less than 0.5 gg/1 the slope differs from the slope at higher concentrations. The scatter of points around the mean increases with increasing chlorophyll. By grouping chlorophyll concentrations a mean and standard error have been determined for each group. This allows the entire data set to be fitted with a power model curve (Y = aXb). The exponent b is 0.758(3/4) which argues that A* is a function of cell volume, i.e., A* = .0667 Chlag/1)-758.