Chlorophyll-a Measurements Research Articles

Characterization and evolution of natural aquatic biofilm communities exposed in vitro to herbicides

River biofilms are assemblies of autotrophic and heterotrophic microorganisms that can be affected by pollutants such as those found in watersheds and wastewater treatment plants. In the laboratory, experimental biofilms were formed from river water, and their overall composition was investigated. Denaturing gradient gel electrophoresis (DGGE) and cytometry were used to assess the richness and diversity of these communities. The software Cytostack (available on request) was developed to treat and analyze the cytometric data. Measurements of chlorophyll-a and carotenoids were used to assess the global composition of the photoautotrophic community, whereas proteins, polysaccharides (PS) content, and esterase activities were used to assess overall changes in the mixed communities. We evaluated the effects that 3 weeks of treatment with the herbicides diuron and glyphosate (10μgL−1) had on these biofilms. Exposed to diuron, bacterial communities adapted, changing their composition. Glyphosate inhibited growth of one autotrophic community but caused no chlorophyll deficit. As a whole, the biofilm acted as a micro-ecosystem, able to regulate and maintain a constant level of photosynthetic pigment through the structural adaptation of the autotrophic community. These results are one more proof that microbial diversity of aquatic biofilms is influenced by chemical stresses, potentially leading to disturbances within the ecosystems.

Comparison of optically derived particle size distributions: scattering over the full angular range versus diffraction at near forward angles

The volume scattering function (VSF) of particles in water depends on the particles' size distribution and composition as well as their shape and internal structure. Inversion of the VSF thus provides information about the particle population. The commercially available LISST instrument measures the scattering at near forward angles to estimate the bulk size distribution of particles larger than about 1 μm. By using scattering over the full angular range (0°-180°), the recently improved VSF-inversion method [X. Zhang, M. Twardowski, and M. Lewis, Appl. Opt. 50, 1240 (2011).] can characterize particles in terms of particle subpopulations, which are described by their unique size distribution and composition. Concurrent deployments of the Multispectral Volume Scattering Meter and the LISST in three coastal waters (i.e., Chesapeake Bay, Mobile Bay, and Monterey Bay) allowed us to compare the size distributions derived from these two different methods. We also obtained indirect validation of the results for submicrometer particles and for the composition of particles provided by the VSF-inversion method. For particle sizes ranging from 1 to 100 μm, the concentration was shown to vary over 10 orders of magnitude, and excellent agreement was found between the two methods with a mean relative difference less than 10% for the total size distributions. The inversion results also reproduced spectral variations in the shape of the VSF, although these spectral variations were not frequently observed in our study. The increased backscattering towards the shorter wavelengths was explained by the stronger influence of submicrometer particles affecting the backscattering. Based on published measurements of cell sizes and intracellular chlorophyll-a [Chl] concentrations over a wide range of phytoplankton species and strains, [Chl] was estimated for the inverted subpopulations that were identified as phytoplankton based on their refractive index and mean sizes. The estimated [Chl] agreed well with the fluorescence-based estimates in both magnitude and trend, thus reproducing a bloom event observed at a time series station.

Trends in the surface chlorophyll of the California Current: Merging data from multiple ocean color satellites

Standard remote sensing reflectance products from four ocean color sensors (OCTS, SeaWiFS, MODISA, MERIS) and over 10,000 in situ measurements of surface chlorophyll-a (Chl-a) concentration in the California Current were used to create empirical algorithms that are consistent with in situ data as well as between individual sensors. Using these algorithms, a merged multi-sensor time series of the surface Chl-a concentration in California Current region was created. The merged Chl-a time series (November 1996–December 2011) show a significant (P<0.01) increasing trend off central California and significant (P<0.01) decreasing trends in the central North Pacific gyre and off southern Baja California. Although this 15-year time series is too short to separate interannual and multidecadal cycles from climate trends, both of these trends are consistent with the predicted effects of global warming. The expected increase in vertical stratification of the water column and the resulting decreased vertical flux of nutrients would lead to lower Chl-a in the gyre but the increased upwelling-favorable winds leading to stronger upwelling off central California or the increased nitrate content of the upwelled water would lead to higher Chl-a in the upwelling region. The decreased Chl-a off southern Baja California resembles the effect of a decreased influence of strong El Nino events.

Response of diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT) trace metal profiles in sediments to phytodetritus mineralisation

Environmental contextContaminated sediments can have a large and lasting effect on marine ecosystems. It was discovered that significant amounts of pollutants, especially arsenic, were released from contaminated sediments during a phytoplankton bloom in the Belgian Continental Zone. Once released to the water column, these pollutants can accumulate up marine food chains and be a source of contaminants to humans. AbstractField data from the Belgian Continental Zone showed elevated trace metal concentrations at the sediment–water interface after the occurrence of a phytoplankton bloom. In the present study, laboratory incubation experiments were used to investigate the effect of the phytodetritus remineralisation process on the release of trace metals from contaminated muddy sediments. This remineralisation process was followed by the measurement of chlorophyll-a and dissolved organic carbon levels in the top sediment layers. Two gel techniques, diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT), were used to assess vertical metal profiles in the sediment pore waters and to calculate the metal effluxes. These metal effluxes compared very well with the trace metal concentration variations in the overlying water of the sediment. Much higher effluxes of Mn, Co and As were observed after 2 days of incubation in the microcosms which received additions of phytodetritus. This trend gradually decreased after 7 days of incubation, suggesting that the elevated efflux of trace metals was proportional to the quantity of phytodetritus mineralised at the sediment–water interface. The release of large amounts of toxic elements from the sediments after phytoplankton blooms can therefore potentially affect the marine ecosystem in the Belgian Continental Zone.

Summertime Phytoplankton Bloom in the South Sulawesi Sea

During southeast (SE) monsoon, strong southeasterly winds induce offshore phytoplankton bloom in the South Sulawesi Sea (SSS). Alongshore wind stress, through interaction with the land topography, is suspected to be the main driving force. The bloom begins in June, enhances in July and reaches peak in August (1.3 mg/m3), then weakens in September. The bloom events coincide perfectly with the low SST and strong wind occurrences. Using advance satellite remote sensing measurements of chlorophyll-a (Chl a), sea surface temperature (SST), and sea surface vector winds for May-September 2004, we describe the seasonal and spatial distributions of the summertime phytoplankton bloom and related oceanographic features in the SSS.

Optical properties of Peter the Great Bay waters compared with satellite ocean colour data

The shipboard measurements of optical and hydrological properties of seawater were used for development of regional bio-optical algorithms of waters of Peter the Great Bay. The shipboard measurements of chlorophyll-a and dissolved organic matter (DOM) concentrations were obtained by flow-through laser fluorometer (LF-3) (Institute for Automation and Control Processes, Vladivostok, Russia) and Sea-Bird Profiling CTD SBE-19plus (Conductivity, Temperature and Depth Sea-Bird Electronics, Sea-Bird Electronics, Inc., Washington, USA) equipped with WetStar fluorometers (WET Labs, Oregon, USA). The measurements were optically weighted according to light attenuation by depth. Ocean colour Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua data were used for our comparative analysis. Chlorophyll-a concentrations from ocean colour data were retrieved by OC3M, Garver-Siegel-Maritorena (GSM) and Carder algorithms. Relationships of the shipboard and satellite sensor data were analysed comparatively in our work. The Carder model gives the most general results of estimation of chlorophyll-a concentrations for all observed water cases. OC3M and GSM algorithms show good performance in case I water but they have large errors in the Amur Bay waters because of a large impact of the Razdolnaya river and Vladivostok city anthropogenic activity. Two regional chlorophyll-a algorithms were offered and they improve significantly the accuracy of chlorophyll-a concentration estimation. The first one is based on empirical regression between chlorophyll-a concentration and remotely sensed reflectance ratio. The second one uses satellite-derived values of sun-induced chlorophyll-a fluorescence when chlorophyll-a concentrations are higher than 3 mg m−3. The last one gives the best results for all water cases and provides an approach for separation between DOM produced by phytoplankton and DOM not connected with phytoplankton activity. This allows a regional DOM algorithm to be made.

Using genetic algorithms to calibrate a dimethylsulfide production model in the Arctic ocean

The global climate is intimately connected to changes in the polar oceans. The variability of sea ice coverage affects deep-water formations and large-scale thermohaline circulation patterns. The polar radiative budget is sensitive to sea-ice loss and consequent surface albedo changes. Aerosols and polar cloud microphysics are crucial players in the radiative energy balance of the Arctic Ocean. The main biogenic source of sulfate aerosols to the atmosphere above remote seas is dimethylsulfide (DMS). Recent research suggests the flux of DMS to the Arctic atmosphere may change markedly under global warming. This paper describes climate data and DMS production (based on the five years from 1998 to 2002) in the region of the Barents Sea (30–35°E and 70–80°N). A DMS model is introduced together with an updated calibration method. A genetic algorithm is used to calibrate the chlorophyll-a (CHL) measurements (based on satellite SeaWiFS data) and DMS content (determined from cruise data collected in the Arctic). Significant interannual variation of the CHL amount leads to significant interannual variability in the observed and modeled production of DMS in the study region. Strong DMS production in 1998 could have been caused by a large amount of ice algae being released in the southern region. Forcings from a general circulation model (CSIRO Mk3) were applied to the calibrated DMS model to predict the zonal mean sea-to-air flux of DMS for contemporary and enhanced greenhouse conditions at 70–80°N. It was found that significantly decreasing ice coverage, increasing sea surface temperature and decreasing mixed-layer depth could lead to annual DMS flux increases of more than 100% by the time of equivalent CO2 tripling (the year 2080). This significant perturbation in the aerosol climate could have a large impact on the regional Arctic heat budget and consequences for global warming.

On phosphate pumping into the surface layer of the eastern Gotland Basin by upwelling

Hydrographic, current, and nutrient measurements were performed on board of the R/V Poseidon in the eastern Gotland Basin from 12 to 21 July 2007, complemented by satellite measurements of sea surface temperature and chlorophyll-a and by measurements of turbulent dissipation. The main aim of the investigations was to elucidate the pathways of phosphate from the intermediate winter water into the surface mixed layer and how this phosphate flux fosters phytoplankto growth. The deep water of the Gotland Basin was exposed to an enduring stagnation phase resulting in a nitrogen to phosphorus ratio very much lower than the Redfield ratio. The intermediate winter water was completely depleted of nitrate but contained a phosphate pool of about 0.40 µM. The surface mixed layer had a mean depth of about 18 m and water temperature of 16 °C and was depleted of both nitrate and phosphate. The average of photosynthetically active radiation during the cruise was about 700 µE/(m²s) at the sea surface. Three pulses of westerly wind with maximum wind speed of about 15 m/s forced upwelling during the cruise at the east coast of Gotland and downwelling at the Latvian coast. The corresponding eastward Ekman offshore transport moved surface water within about three days through the coastal boundary layer and in roughly 50 days across the Gotland Basin. Two mesoscale eddies were observed off the south eastern coast of Gotland which supported upwelling filaments near the southern tip of this island. Within the coastal boundary layer, the upwelling transported phosphate from the intermediate winter water into the surface layer off Gotland where it was mixed with the phosphate depleted surface water. Generally, the upwelled phosphate was taken up by the plankton community of the surface mixed layer already within the coastal boundary layer and transformed completely into the particulate and dissolved organic phase. However, at sites where upwelling filaments develop, dissolved phosphate is transported over a distance of about three times the internal Rossby radius in offshore direction. The phosphate transport into the surface mixed layer of the eastern Gotland Basin by upwelling exceeded the corresponding transport by turbulent mixing through the seasonal thermocline by about one order of magnitude during typical summerlike wind conditions.

Spatial variability associated with shifting land use: Water quality and sediment metals in La Parguera, Southwest Puerto Rico

Development in southwest Puerto Rico, as in many areas of the Caribbean, is outpacing the ability of upland flora, salt flats, and mangroves to capture sediments and intercept and transform nutrients. A comparative study to examine the effects of development on near-shore water quality in La Parguera, Puerto Rico, was initiated in 1998. Total suspended solids were significantly higher in the vicinity of developing areas compared to reference areas. Chlorophyll-a measurements near of the wastewater treatment plant averaged two times the level of other areas. The overall average concentrations of copper, chromium, nickel, and zinc in sediments collected from salt flats exceeded values reported to cause impairment of biological systems. Marine sediments near more developed locations had the highest metal concentrations, suggesting a greater transport in this area. Natural resources are the primary attraction in this area; therefore, protection of near-shore resources should receive greater attention in land use planning.

Remote sensing of ocean hazard influences on marine ecosystem

Abstracts / Journal of Biotechnology 136S (2008) S519–S526 IL-045Remote sensing of ocean hazard influences on marine ecosys-tem Danling Tang ∗ , Z.Z. Yan, H. Zhao RemoteSensingCenteronMarineEcology/Environment(RSMEE),LED,South China Sea Institute of Oceanology Chinese Academy of Sciences164 West Xingan Road, Guangzhou, China, 510301E-mail address: lingzistdl@126.com (D. Tang).Frequency of all kinds of natural hazards has increased in the lasttwo decades. These natural hazards have killed thousands of peo-pleandaffectedmillionsofpeople.Withthedevelopmentofspacetechnology, information about the land, ocean, atmosphere andmeteorological parameters can be routinely available which willhelpscientificcommunityingettinginformationaboutthedamagefrom all kinds of Natural Hazards and also one can get informationabout early warning of an impending natural hazard. This paperinvestigates the influences of ocean hazards, such as tsunami andtyphoon,andHarmfulAlgalBlooms(HAB)onmarineecosystem,byanalyzing satellite remote sensing data and historical records andin situ measurements of Chlorophyll-a (Chl-a), sea surface temper-ature (SST), suspended sediment concentration (SSC), and winds.The study area is so called “Asian waters”, including Indian Ocean,South China Sea, and Japan Sea. This study has found changes ofsuspended sediment, Chlorophyll-a, phytoplankton blooms, andair-sea interaction for local weather after tsunami and typhoon.

Determination of chlorophyll-a amount in Golden Horn, Istanbul, Turkey using IKONOS and in situ data

The objective of this research was to explore an accurate and fast way of estimating chlorophyll-a amount, a water quality parameter (WQP), using IKONOS satellite sensor image and in situ measurements. Since the in situ data of WQPs are limited with the number of sampling locations, deriving a correlation between these measurements and remotely sensed image allows synoptic estimates of the related parameter over large areas even if the areas are in remote and inaccessible locations. In this study, simultaneously collected satellite image data and in situ measurements of chlorophyll-a were correlated using multivariate regression model. Different experiments were designed by changing the numbers and distributions of in situ measurements. Regression coefficients of each design and differences between model-derived data and in situ measurements were calculated to find out the optimum design to produce chlorophyll-a map of study region. Results illustrated that both the number and distribution of in situ measurements have impact on regression analysis, therefore should be selected attentively. Also, it is found that IKONOS imagery is an efficient and effective source to derive chlorophyll-a map of the large areas using limited number of ground measurements.

Influence of temperature and food availability on the biochemical composition and mortality of juvenile Mercenaria mercenaria (L.) during the over-winter period

Over-winter mortality of juvenile aquacultured northern quahogs (=hard clams), Mercenaria mercenaria, is a significant problem for the Mid-Atlantic and Northeast aquaculturists. Although protecting seed from predators improves survival, significant mortalities still frequently exceed 50%. The mortality has been attributed to severe winter temperatures, however, this suggestion has yet to be systematically investigated. We hypothesize that extended periods of low water temperatures (<5 °C) will result in reduced hard clam pumping, and a subsequent increase in the use of energy stores for metabolism. This would then lead to demise in physiological condition and cause mortality in the spring when water temperatures increase, food levels are low and metabolic demand is high. In this study, juvenile aquacultured hard clams were planted at two sites in Jamaica Bay, New York during the fall in the years of 2001, 2002, and 2004, to investigate the magnitude and mechanisms of action of over-winter mortality through the winter and spring. Measurements of temperature, chlorophyll-a, and total clam biochemical composition were conducted to identify any correlations with over-winter mortality. The field data indicate that a mild winter (2001–2002) results in negligible mortality. Similarly, a severe winter (2004–2005) followed by a spring in which the rise in water temperature coincides with high food (chlorophyll-a) levels also results in low mortality. In contrast, significant mortality (up to 0.99% per day) occurs in the spring following a severe winter (2002–2003), at a time when water temperatures are rising but food levels are low (Chl-a<3 µg L−1). During this period a rapid decline of carbohydrate content is observed, suggesting the use of energy reserves to maintain metabolic activity. Mortality is associated with carbohydrate levels below 10% of the tissue dry weight. Therefore, it appears that significant mortality of juvenile aquacultured hard clams occurs when phytoplankton abundance is low as water temperature is increasing during the spring. It would be more appropriate to refer to this phenomena as a winter–spring mortality.

Coupling between Land and Ocean Biospheres as Observed by Sea-viewing Wide Field-of-view Sensor (SeaWiFS)

SeaWiFS measurements of Chlorophyll-a (Chl-a) and Normalized Difference Vegetation Index (NDVI) are analyzed for understanding the coupling between the oceanic and terrestrial biospheres at interannual timescale. Principal component analysis (PCA) of NDVI and Chl-a jointly suggests existence of stationary/dipole modes of variability between several neighbouring land-ocean regions. PC time series for NDVI and Chl-a separately are found to be anticorrelated during the period of this analysis (Autumn 1997-Summer 2006). Other satellite and analyzed products, e.g., sea-surface temperature, precipitation, absorbing aerosols suggest that the observed land-ocean biospheres are coupled beyond that can be explained by purely dynamical mechanisms.

Resurrection of the Lake Michigan Eutrophication Model, MICH1

The Lake Michigan model, MICH1, was developed more than 30 years ago. This framework was evaluated using field data collected in 1976 and was later applied to predict total phosphorus and phytoplankton concentrations in Lake Michigan during the 1980s and early 1990s. With a renewed interest in the interaction of phytoplankton with toxics and the applicability to Total Maximum Daily Load studies, several new models have been developed and older models have been revived. As part of our interest in plankton dynamics in Lake Michigan, the MICH1 model was resurrected. The model was evaluated over the 1976–1995 period, with a surprisingly good model fit to lake-wide average total phosphorus (TP) field data. However, the model was less successful in mimicking the chlorophyll-a measurements, especially in the hypolimnion. Given the results, the model was applied to perform a few long-term TP model simulations. Using the model with average 1994–95 phosphorus loadings, a steady state was reached within approximately 20 years, and the lakewide phosphorus concentration was below the International Joint Commission water quality guideline of 7 μg/L. This exercise demonstrated that a relatively simple, four-segment model was able to mimic the TP lake-wide data well. However, this model was less suitable to predict future chlorophyll-a concentrations due to the limitation in the representation of the foodchain and the difficulty of the coarse segmentation of the model to capture the deep chlorophyll-a layer. Strengths and limitations of this model can guide future development of eutrophication models for Lake Michigan and the other Great Lakes.

North Atlantic and North Sea Climate Change: curl up, shut down, NAO and Ocean Colour

The strength of the North Atlantic Current (NAC) (based on sea-surface elevation slopes derived from altimeter data) is correlated with westerly winds (based on North Atlantic Oscillation [NAO] Index data over a nine year period [1992–2002] with 108 monthly values). The data time window includes the major change in climate forcing over the last 100 years (1995 to 1996). It is shown that the NAO Index can be used for early warning of system failure for the NAC. The correlation response or early warning time scale for western Europe and south England is six months. The decay scale for the NAC and Subtropical Gyre circulation is estimated as three years. Longer period altimeter elevation/circulation changes are discussed. The sea-surface temperature (SST) response of the North Sea to negative and positive NAO conditions is examined. The overall temperature response for the central North Sea to NAO index forcing, reflecting wind induced inflow, shelf circulation and local climate forcing, is ∼5 months. In years with strong North Atlantic winter wind induced inflow, under marked NAO positive conditions, mean temperatures (∼10.5°C) are about 1°C warmer than under negative conditions. In 1996 under extreme negative winter NAO conditions, the North Sea circulation stopped, conditions near the Dogger Bank became more continentally influenced and the winter (March) temperature fell to 3.1°C whereas in 1995 under NAO positive winter conditions the minimum temperature was 6.4°C (February). Seasonal advance of North Atlantic and North Sea temperature is derived in relation to temperature change. Temperature change and monthly NAO Index are discussed with respect to phytoplankton blooms, chlorophyll-a measurements, ocean colour data and the anomalous north-eastern Atlantic 2002 spring/summer bloom SeaWiFS chlorophyll concentrations.

The grazing effects of grass shrimp,Palaemonetes pugio, on epiphytic microalgae associated withSpartina alterniflora

Experiments were performed seasonally to estimate grass shrimp,Palaemonetes pugio, grazing on the epiphytic microalgae of cordgrass,Spartina alterniflora, and to determine if grass shrimp have the potential to regulate epiphyte abundance. Grass shrimp were given access to live culms with low and high epiphytic abundance and standing dead culms collected from the streamside levee of a Louisiana salt marsh. Plexiglas frames were used to hold culms upright in aquaria and to restrict grass shrimp access to one half of each culm. We compared epiphyte biomass on the sides of culms exposed to shrimp with the corresponding unexposed sides. Epiphytes were removed from the lowest 10 cm of culms on days 0, 3, and 10, and chlorophylla (chla) measurements on each culm half were made by fluorometry. Chla biomass on culm halves not exposed to grass shrimp significantly increased over time. Percent reductions in chla on culm halves exposed to grass shrimp (calculated by subtraction from the corresponding half not exposed to shrimp) significantly increased over time for at least one culm type in all seasons. Grass shrimp caused an average 30% reduction of epiphyte biomass over 3 d and a 40% reduction over 10 d, suggesting that grass shrimp have the capability of consuming a substantial proportion of the daily production of epiphytes. Epiphytes from standing-dead culms may be more important than those from live culms at the marsh edge to the diet of grass shrimp because chla biomass was, on average, high, and standing-dead culms were seasonally abundant. Diagnostic photosynthetic pigments from selected culms, grass shrimp gut contents, and fecal pellets were identified by high performance liquid chromatography and were used to quantify the taxonomic groups of epiphytic microalgae. Results suggested that diatoms, brown algae, green algae, red algae, and cyanobacteria were present on all culms. Similarities in the pigment content of grass shrimp gut contents and fecal pellets suggested that all algal groups were ingested. Pigment data analysis could not detect a change in the composition of the microalgal assemblage associated with grass shrimp grazing. Assuming that the reduction in chla was due exclusively to grazing, grass shrimp consumed an average of 0.5–1.5 g epiphyte carbon shrimp−1 d−1, suggesting that grass shrimp benefit significantly from the consumption ofS. alterniflora epiphytic algae.

Comparison of bio-physical marine products from SeaWiFS, MODIS and a bio-optical model with in situ measurements from Northern European waters

In this paper, we compare bio-physical marine products from SeaWiFS, MODIS and a novel bio-optical absorption model with in situ measurements of chlorophyll-a (Chla) concentrations, total suspended material (TSM) concentrations, normalized water-leaving radiances (nLw) and absorption coefficients of coloured dissolved organic matter (aCDOM), total particulate (atotal) and phytoplankton (aphy) for 26 satellite match-ups in three Northern European seas. Cruises were undertaken in 2002 and 2003 in phytoplankton dominated open ocean waters of the Celtic Sea and optically complex waters of the Western English Channel (WEC) and North Sea. For all environments, Chla concentrations varied from 0.4 to 7.8 mg m−3, TSM from 0.2 to 6.0 mg l−1 and aCDOM at 440 nm from 0.02 to 0.30 m−1. SeaWiFS OC4v4, with the Remote Sensing Data Analysis Service (RSDAS) atmospheric correction for turbid waters, showed the most accurate retrieval of in situ Chla (RMS = 0.24; n = 26), followed by MODIS chlor_a_3 (RMS = 0.40; n = 26). This suggested that improving the atmospheric correction over optically complex waters results in more accurate Chla concentrations compared to those obtained using more complicated Chla algorithms. We found that the SeaWiFS OC4v4 and the MODIS chlor_a_2 switching band ratio algorithms, which mainly use longer wavebands than 443 nm, were less affected by CDOM. They were both more accurate than chlor_MODIS in the higher CDOM waters of the North Sea. Compared to MODIS the absorption model was better at retrieving atotal (RMS = 0.39; n = 78) and aCDOM (RMS = 0.79; n = 12) in all study areas and TSM in the WEC (RMS = 0.04; n = 10) but it underestimated Chla concentrations (RMS = 0.45; n = 26). The results are discussed in terms of atmospheric correction, sensor characteristics and the functioning and performance of Chla algorithms.

Factors influencing the distribution, biomass, and productivity of phytoplankton in the Scotia Sea and adjoining waters

During January and February 2000 four research vessels,f rom Russia,t he UK, Japan, and the United States, conducted an oceanographic survey with 137 hydrographic stations within the Scotia Sea and adjoining waters as part of a survey sponsored by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) to estimate the biomass and distribution of Antarctic krill in the Scotia Sea. Chlorophyll-a (Chl-a) measurements showed great variability in phytoplankton biomass within the Scotia Sea,wi th some areas having among the lowest Chl-a concentrations found in Antarctic waters (o0.1mgm_3 in surface waters) while other areas were among the richest with 410mgm_3. This paper describes the distribution and concentration of Chl-a in the upper 100m of the water column and relates the Chl-a profiles at individual stations to profiles of upper water-column stability,t o the depth of the upper mixed layer, and to the mixing of different water masses. The 58 stations with the lowest Chl-a values in surface waters also had low values for integrated Chl-a (33.9+-9.5mgm_2) and a Chl-a maximum at depths of between 70 and 90m,in contrast to all other stations where deep Chl-a maxima did not occur. The T/S diagrams at many of these stations were indicative of Antarctic Circumpolar Current (ACC) waters. The central Scotia Sea and areas to the west and north of South Georgia had significantly higher integrated Chl-a values (98.1+-46.0mgm_2, n ¼ 57),i n addition to five stations with very high Chl-a values (mean of 359+-270mgm_2). The mean rate of integrated primary production,wh ich was estimated using the Chl-a data and the mean incident solar radiation measured from previous cruises as well as from satellite data,w as estimated to be 994mg carbon m_2 day_1. The temperature profiles at these stations suggested that considerable interleaving and mixing of water types had occurred,w hich was also evident in the T/S diagrams,w hich indicated mixing of ACC waters with coastal waters originating from Bransfield Strait or theWeddell Sea. There was no significant correlation between integrated Chl-a values and the profiles of upper water column stability or the depth of the upper mixed layer. The spatial variability in phytoplankton biomass within the Scotia Sea is discussed in relation to the hypothesis that low iron concentrations are the major factor controlling phytoplankton biomass in these pelagic Antarctic waters and that concentrations of iron available for phytoplankton uptake are strongly influenced by fronts and the mixing of different water masses.

Deriving phytoplankton biomass in the Marginal Ice Zone from satellite observable parameters

Water mass properties and sea ice history have a significant impact on the vertical distribution of phytoplankton in the Marginal Ice Zone of the northern Barents Sea. A method is suggested to identify the phase and magnitude of the phytoplankton bloom based on satellite observable values of chlorophyll-a, temperature, salinity and sea ice history. For each bloom phase, formulae are provided for calculation of the chlorophyll-a column from satellite-equivalent measurements of chlorophyll-a.

Application of empirical neural networks to chlorophyll-a estimation in coastal waters using remote optosensors

This paper presents chlorophyll-a estimation in coastal waters off the Gulf of Finland using remote optosensors. Concurrent remote optosensor data and in situ measurements of water quality were obtained in the study area. Significant correlations were observed between digital values and chlorophyll-a measurements. The results as a case study show that the estimated accuracy of chlorophyll-a retrieval using neural networks is higher than the accuracy of chlorophyll-a estimation using regression analyzes in the area. The study also shows one example why remote optosensors are critical to monitor water quality in coastal areas such as the Gulf of Finland.