High Concentrations Of Chl Research Articles

Numerical modelling of natural water colour: Implications for remote sensing and limnological studies

Based on suggested earlier optical models of Lakes Ontario and Ladoga, numerical modelling experiments have been carried out to the effect of revealing the responsiveness of chromaticity coordinates (x, y, z), dominant wavelength (lambda dom) and associated spectral purity (p) to the abundance in water of optically active components (OAC), i.e., phytoplankton (chl), suspended minerals (sm) and dissolved organic carbon (doc). It has been shown that highly turbid waters (i.e., waters with high chl and sm concentrations) with low content of doc display colour varying from green to brownish. High turbidity or large doc concentration invariably is characteristic of waters with brown colour. With growing OAC content in water, the chromaticity coordinates and, consequently, the dominant wavelength lambda dom tend asymptotically to respective limit values that seem to be intrinsically characteristic of natural waters. It is also shown that the colour purity p asymptotically tends to values of about 35-45 per cent (with the only exception for waters containing exclusively chl and this in small quantities (0.5mu gl-1)) when concentrations of one or more OAC are over 10 (in respective concentration units). These findings clearly indicate that neither panchromatic nor two-channel ratio images could be meaningful for an unambiguous inference of water quality parameters. Furthermore, the correspondence between water colour physical characteristics (i.e., x, y, z, lambda dom and p) and water colour scales traditionally used in limnology is established.

Distributions of dissolved manganese and fluorescent dissolved organic matter in the Columbia River estuary and plume as determined by in situ measurement

We deployed an instrument package consisting of a SeaBird 911 plus CTD, SeaTech 25-cm transmissometer, Chelsea AquaTracka fluorometer/nephelometer, Seapoint turbidity meter and ZAPS UV fluorometer/chemical sensor during a series of tows and lowerings within the Columbia River plume and estuary in 1994 and 1995. Simultaneous in situ measurements of Chl a, light attenuation, light scattering, and fluorescent dissolved organic matter (FDOM) or dissolved Mn collected along with CTD information provided new insight into the effects of mixing and non-conservative processes on riverine input to the coastal ocean. Inter-relationships among these parameters proved to be effective at delineating three coastal water masses: Columbia River Plume Water (CRPW), Shelf Deep Water (SDW), and Shelf Bottom Water (SBW). CRPW had variable amounts of FDOM, dissolved Mn, and Chl a as the plume mixed with coastal water. SBW was characterized by high concentrations of Chl a and low concentrations of dissolved Mn, suggesting a surface or near-surface source. The properties of SDW were intermediate between humic-rich plume water and turbid bottom water. FDOM displayed a quasi-linear and inverse relationship with salinity inside the estuary and nearshore coastal plume which supports previous work relating this parameter to the humic-rich terrestrial component of dissolved organic matter (DOM). There was, however, considerable evidence of lower FDOM levels within the estuarine turbidity maximum (ETM) and near the seaward boundary of the plume. There were also elevated levels of FDOM near the bottom at some locations on the shelf, suggesting that there may be a significant benthic flux of this material. Thus FDOM appears to be more reactive than previously thought when looked at in detail. Dissolved Mn also displayed non-conservative behavior in the estuary and across the plume showing significant input into surface waters. The sharpest Mn gradient on the shelf occurred near the seaward edge of the plume in an area of relatively high turbidity and Chl a, and relatively low FDOM. These distributions are consistent with the presence of a chemical front near the plume boundary where Mn-oxides are reduced during the oxidation of humic ligands. This process would release dissolved Mn and promote productivity in the turbid zone associated with the leading edge of the plume jet. This study demonstrates that chemical sensors can provide highly resolved, detailed information on trace substance distribution and variability in marine environments.

Modelling the Radiometric Color of Inland Waters: Implications to a) Remote Sensing and b) Limnological Color Scales

Utilizing a bio-optical model previously developed for Lake Ontario, the responsiveness of chromaticity coordinates (X, Y, Z), dominant wavelength (λ dom), and associated spectral purity (p) to the abundance of color-producing agents (CPA) residing within the Lake Ladoga water column was determined. CPA considered were phytoplankton (chl), suspended minerals (sm), and dissolved organic carbon (doc). Waters that contain simultaneously low concentrations of chl, sm, and doc are shown to appear blue to turquoise in color (472–500 nm). Highly turbid waters (i.e., waters containing high concentrations of chl and/or sm) with low concentrations of doc are shown to display colors ranging from green to brown (> 500 nm). Waters with large concentrations of doc, irrespective of turbidity, are shown to be invariably brownish (560–570 nm). With increasing CPA content, X, Y, and Z (and, consequently, λ dom) asymptotically approach constant limit values. An “end-point” dominant wavelength at about 572 nm appears to be intrinsically characteristic of all natural waters. It is shown that when one or more CPA exceeds a critical concentration, the spectral purity p asymptotically approaches values in the range 0.35 to 0.45 for all waters (exceptive of those containing solely chl in the restricted concentration range < 0.5 μg/L). Optical distinctiveness, particularly with respect to indigenous doc, of natural waters, while impacting the spectral purity of the “end-point” radiometric color, does not produce a comparable impact on the “end-point” color itself. This work reinforces the restrictive application of chromaticity analyses to the remote sensing of binary aquatic systems comprised of water plus one CPA. It also illustrates that neither panchromatic nor two-channel ratio images can provide unambiguous inference of water quality parameters. Correspondence between radiometric water color descriptors (X, Y, Z, λ dom, and p) and water color scales traditionally used in limnology is established, illustrating that the platinum-cobalt scale would be most appropriate for assessing waters that were radiometrically yellow, provided that the yellow hue were not invariably attributed to doc.

Composition and biomass of plankton in spring on the Cape Hatteras shelf, with implications for carbon flux

The Ocean Margins Program, an interdisciplinary study focussed at Cape Hatteras, is evaluating whether this region is a net source or sink for carbon, while concurrently developing a mechanistic understanding of the production, cycling and fate of organic carbon. Preliminary to a large multi-ship field program in 1996–1997, the first of several short cruises surveyed Cape Hatteras in May 1993. High concentrations of chl a occurred across the shelf. Stations and depths at which chl a was highest also showed elevated concentrations of large phytoplankton, predominantly chained diatoms, but also single-celled dinoflagellates and obligately photosynthetic ciliates. These populations occurred in deeper waters, however, and their abundance was poorly correlated with proxies of community photosynthesis. Instead, small phototrophic nanoplankton, abundant in surface waters, were positively correlated with primary production. Carbon budgets indicated that inner shelf waters contained ca 50% more living POC than outer shelf waters. The relative importance of large phytoplankton and grazers decreased with distance offshore, and they were replaced by photosynthetic nanoplankton and microzooplankton. Even greater changes in living POC occurred in the alongshore direction due to the dramatic reductions in diatoms in southern waters. Estimated herbivory was ca 2–4 gC m −2 d −1. The ratio of heterotrophic : autotrophic POC increased from 38% in northern waters to 137% in southern waters, suggesting that phytoplankton was being converted into consumer carbon as shelf waters advected south. The dominant consumers at most stations were single-celled protozoan zooplankton and small copepods, whose fecal products remain in suspension in energetic shelf environments, suggesting that much of the non-diatomaceous POC was exported as shelf waters exited at Cape Hatteras.

Why does the relationship between sinking flux and planktonic primary production differ between lakes and oceans?

The fraction of primary production lost to sinking (the export ratio) increases with productivity in the ocean and decreases slightly with productivity in lakes. To explore why this distinction exists, we compared marine and freshwater regressions relating chlorophyll concentrations in the euphotic zone to each of the three variables that define the export ratio: primary productivity, carbon sinking fluxes, and euphotic zone depth. Chlorophyll was found to predict these three variables well (r2 = 0.54–0.90) in both lakes and the ocean. The differences between the marine and freshwater export ratio—productivity relationships stem primarily from a discrepancy in the primary productivity—Chl relationships. On average, a &gt;10‐fold difference in Chl‐specific productivity exists between the most oligotrophic lakes (Chl = 0.2 mg−3) and oceanic regions with similar Chl concentrations. This difference disappears at higher concentrations of Chl because primary productivity: Chl ratios increase with productivity in lakes. In addition, carbon sinking rates average 2–3‐fold higher in the oceans than in lakes with similar concentrations of Chl. The trends of marine and freshwater export ratio‐production can be qualitatively reproduced with Chl‐based predictions of euphotic zone primary productivity, depth, and carbon sinking losses from regressions. Marine and freshwater ecosystems may differ systematically in the efficiency of nutrient recycling processes in the water column and in the nature of settling material.

Measurement of Fe(II) in surface water of the equatorial Pacific

The distribution of Fe(II) in euphotic waters of the equatorial Pacific Ocean was examined with novel in situ sampling and analytical methodology. Dissolved Fe(II) was isolated and preconcentrated, at depth, with a ligand-exchange Chromatographic technique and then determined spectrophotometrically. The distribution of Fe(II) in the upper 100 m was both temporally and spatially variable but generally exhibited maxima near the surface and often at depths with higher concentrations of Chl a. The concentration of Fe(II) varied from below the detection limit of 0.12 to 0.53 nmol kg-‘. Exposure of equatorial Pacific water to simulated sunlight in the laboratory resulted in similar Fe(II) concentrations, suggesting that photochemical reduction may be an important source for Fe(II) in these waters. Field measurements indicate that Fe(II) may comprise a significant fraction of the Fe present in euphotic ocean waters, which typically contain < 1 .O nmol kg-’ of dissolved Fe. The presence of detectable steady state concentrations of Fe(II) is believed to be the result of faster rates of photochemical and(or) biological reduction of Fe(III), relative to rates of Fe(II) oxidation by oxygen, peroxides, and other oxidants.

Distribution of algal chlorophyll and carotenoid pigments in a stratified estuary: the Krka River, Adriatic Sea

The detailed distribution of algal chlorophyll and carotenoid pigments was determined around the halocline (freshwater-seawater interface) in the Krka Estuary on the east coast of the Adriatic Sea; in May 1988. After collection of water along the estuary, particulate matter was extracted and analyzed for pigments by high-performance liquid chromatography coupled with absorbance and fluorescence detection. Bottom marine waters were characterized by lower chlorophyll a (chl a) concentrations than encountered in surface waters, decreasing downstream from 0.50 μg l −1 to 0.16 μg l −1 at the marine end-member. The highest concentrations of chl α (up to 26.34 μg l −1) were found in the interfacial layer, an particularly at one station located off the city of Šibenik, where high inputs of nutrients supported the accumulation of living algae at the halocline. Fucoxanthin was the most abundant carotenoid, which indicates a euryhaline dominance of diatoms in the estuary, whereas the dinoflagellate-derived carotenoid peridinin was confined to the interfacial and bottom saline waters of the inner estuary. High concentrations of alloxanthin and chl b were found in the interfacial layer, which also suggests an accumulation of Cryptophyceae and green algae in the inner estuary. Phaeophorbides showed higher concentrations in bottom waters than in surface waters, whereas the highest concentrations occurred in the interfacial layer. These high levels could reflect a density trapping of dead cells in an early degradation state, as suggested by the importance of allomerized chl a and chlorophyllide a vs. total chl a, or of faecal pellets originating from zooplankton grazing in the interfacial layer.

Reflected Far-Red Light Effects on Chlorophyll and Light-Harvesting Chlorophyll Protein (LHC-II) Contents under Field Conditions

The influence of various colors of soil cover (mulch) on the farred/red (FR/R) ratio in upwardly reflected light and on concentrations of chlorophyll (Chl) and light-harvesting Chl protein (LHC-II) were measured under field conditions. The FR/R ratios above green surfaces were higher than over white surfaces. Even though plants (Gossyplum hirsutum L. cv PD-1) were grown in full sunlight, those that received higher FR/R ratios in upwardly reflected light were taller and had thinner leaves with higher concentrations of Chl and LHC-II. A controlled environment experiment showed FR/R control of Chl and LHC-II concentrations. The results illustrate the importance of spectral distribution of reflected light on plant growth and a potential means of altering the chemistry of leaf crops under field conditions.