Distribution Of Chlorophyll-a Research Articles

Role of Mesoscale Eddies in the Distribution Pattern of Zooplankton Standing Stock of Western Bay of Bengal During Spring Transition

Hydrography and spatial variability of zooplankton community during spring transition associated with Anti Cyclonic Eddies (ACE) and Cyclonic Eddies (CE) in the south western Bay of Bengal is investigated. In situ data collected on board FORV Sagar Sampada and satellite derived products were used for the study. Physical parameters such as temperature, salinity, and sigma-t in the surface waters showed typical spring condition with almost uniform distribution in the region. However, MLD, ILD and BLT showed noticeable variation between ACE and CE region. The satellite derived SSHA overlaid geostrophic current pattern indicates the piling up of surface water (20cm) in the region as the result of ACE centred at 13.25°N, 83°E and negative anomaly of 24cm associated with Cyclonic eddy at 15°N, 84°E. Observed cyclonic eddies (15°N, 84°E) are characterised by depressing temperature by about 7°C at 100m depth. The forcing mechanism of ACE identified as negative wind stress curl and associated westward propagating Rossby waves and formation of CE might be due to baroclinic instability developed by equator ward flow of fresh plume water from the north during the winter monsoon period. The biological response in the primary and secondary level to these phenomena explained based on chlorophyll-a distribution and mesozooplankton standing stock. Satellite imagery showed a uniform distribution of surface chlorophyll (< 0.1 mg m˗3) in the study region, except a slight increase in the CE. Subsurface Chlorophyll Maxima (SCM) observed at the base of the mixed layer showed the preference of phytoplankton community to the optimum environmental conditions. Mesozooplankton standing stock observed was relatively higher at CE and the centre of ACE. Enhanced phytoplankton standing stock due to the nutrient enrichment at CE favoured the abundance of zooplankton community. In contrast to the general trend, core of ACE supported higher zooplankton standing with dominance of copepods, chaetognaths, ostracods etc. Relatively higher biological production in the primary as well as secondary level during the present study was associated either with the extended winter production to the early months of spring or the characteristics like intensity, age, spatial variation of prevailing physical processes.

EFFECTS OF DIPOLE MODE AND EL-NINO EVENTS ON CATCHES OF YELLOWFIN TUNA (Thunnus albacares) IN THE EASTERN INDIAN OCEAN OFF WEST JAVA

The effects of Indian Ocean Dipole Mode and El Niño–Southern Oscillation events on catches of YellowfinTuna (&lt;em&gt;Thunnus albacares&lt;/em&gt;) in the Eastern Indian Ocean (EIO) off Java were evaluated through the use of remotely sensed environmental data (sea surface temperature/SST and chlorophyll-a concentration/SSC) and Yellowfin Tuna catch data. Analyses were conducted for the period of 2003–2012, which included the strong positive dipole mode event in association with weak El-Nino 2006.Yellowfin Tuna catch data were taken from Palabuhanratu landing place and remotely sensed environmental data were taken from MODIS-Aqua sensor.The result showed that regional climate anomaly Indian Ocean Dipole Mode influenced Yellowfin Tuna catch and its composition. The catches per unit effort (CPUE) of Thunnus alabacares in the strong positive dipole mode event in 2006 and weak El-Nino events in 2011 and 2012 was higher. The increase patern of CPUE followed the upwelling process, started from May-June achieved the peak between September-October.Very high increase in CPUE when strong positive dipole mode event (2006) and a weak El-Nino events (2011 and 2012) had a relation with the increase in the distribution of chlorophyll-a indicating an increase in the abundance of phytoplankton (primary productivity) due to upwelling. In contrast, yellowfin tuna CPUE is very low at the La-Nina event (2005), though as the dominant catch when compared to others.

Prediksi Zona Tangkapan Ikan Menggunakan Citra Klorofil-a Dan Citra Suhu Permukaan Laut Satelit Aqua MODIS Di Perairan Pulo Aceh

Fishing ground or fishing zone is a waters area which become a destination for fishing. The prediction of fishing zone can be done by detecting chlorophyll-a and sea surface temperature distribution of Aqua MODIS Imagery. The aim of this study is to predict fishing zone on the waters of Pulo Aceh based on the chlorophyll distribution and sea surface temperature by utilizing the data of Aqua MODIS Satellite Imagery level 3. The stages of this study included collecting imagery, cutting the image according to the desired area, giving lands mark to display a more informative image, extracting information of chlorophyll-a and the distribution of sea surface temperature, and interpolating by using Kriging method. The highest distribution of chlorophyll-a happened in June and August, the spread moved from the the North Pulo Aceh to the South. The distribution of sea surface temperature that suitable for fishing was detected in August around the North Ujung Pulo Breuh and around pulau Keureusik. The potential zone of fishing on the waters of Pulo Aceh was only detected in August in the eastern of pulau Keureusik to Ujong Keumuroh. Pulo Aceh waters is suitable for fishing destination in August.

Bathymetrical influences on spatial and temporal characteristics of chlorophyll-a concentrations in the Southern Ocean from 2002 to 2012 (October to March) using MODIS

Phytoplankton blooms, particularly in the Southern Ocean, can have significant impact on global biogeochemistry cycling. To investigate the accuracy of chlorophyll-a distribution, and to better understand the spatial and temporal dynamics of phytoplankton biomass, we examine chlorophyll-a estimates (October–March from 2002 to 2012) derived from Moderate Resolution Imaging Spectrometer (MODIS) data following the ocean chlorophyll-a 3 model (OC3M) algorithm. Noticeable seasonality occurs in the temporal distribution of chlorophyll-a concentrations, which shows the highest value in December and January and an increasing tendency during the 2002–2012 period. The spatial distribution of chlorophyll-a varies greatly with latitude, as higher latitudes experience more phytoplankton blooms (chlorophyll-a concentration larger than 1 mg/m3) and marginal seas (Ross Sea and Amundsen Sea) show different bloom anomalies caused by two dominant algae species. Areas at higher latitudes and shallow water (<500 m) experience the shorter ice-free periods with greater seasonality. A noticeable bathymetry gradient exists at 2500-m isobaths, while water at the 500–2500-m depth experiences quite long ice-free periods with a stable water environment. Blooms generally occur near topographic features where currents have strong interactions when the water depth is more than 2500 m. Based on these findings, we can classify the Southern Ocean into two bloom subregions, 0–500 m as an enhanced bloom zone (EBZ), and 500–2500 m as a moderate bloom zone (MBZ). The EBZ has a quite high-bloom probability of about 30%, while the MBZ has only 10%.

Characterization of water quality in stratified nursery recycling irrigation reservoirs

Recycling irrigation reservoirs (RIRs) are an emerging aquatic ecosystem of global significance. Building upon the recent discovery of thermal stratification in these novel systems and its impacts on the vertical distribution of dissolved oxygen and pH, this study investigated the dynamics of chlorophyll a (CHLA), oxidation reduction potential (ORP), electrical conductivity (EC), and turbidity in the water columns of eight RIRs in the Mid-Atlantic region in USA over a 3-year period from 2011 to 2014. The vertical distribution of CHLA was associated with thermal stratification while ORP and EC were directly affected by thermal stratification. Specifically, CHLA concentration was greatest in the middle thermocline, followed by lower hypolimnion during the stratification period. ORP level was higher at the surface than bottom with differences up to 505.67mv in Reservoir VA23. EC level was higher in the bottom than at the surface with the maximum difference of 0.90dSm−1 in Reservoir VA22. The top–bottom ORP and EC differences increased when water was stratified. Turbidity was indirectly affected by stratification. The correlation of turbidity with total precipitation was stronger during the non-stratification period from November to March than during the stratification period from April to October, mainly due to restriction on water mixing. The characterization of these additional water quality parameters in the water columns of RIRs provides fundamental knowledge about this novel water system and will help in developing sound water quality management practices for improved crop health and production while reducing agriculture's environmental footprint. This study also provides additional evidence supporting pH as a significant indicator for monitoring water quality in RIRs.

Satellite-derived estimates of primary production during the Sargasso Sea winter/spring bloom: Integration of in-situ time-series data and ocean color remote sensing observations

Accurate estimates of primary production from satellite-derived data on both regional and global scales are one of the most important goals of international ocean color remote-sensing programs. This manuscript presents surface concentrations and vertical distributions of chlorophyll-a (Chl-a) data as a proxy for phytoplankton biomass, and calculated photosynthesis–irradiance (P–E) curve parameters, which were used to estimate integrated monthly primary production in the Sargasso Sea euphotic zone from 2004 to 2009. The measured surface Chl-a in the Sargasso Sea was low but exhibited strong seasonal variation, and correlated well with satellite estimates of Chl-a. Underwater light transmission was modeled using a shifted Gaussian model from 69 vertical Chl-a profiles, which were collected in the Sargasso Sea. The P–E curve parameters were experimentally derived; the maximum photosynthetic rate, PmB ranged from 1.51 to 3.05 (mgC(mgChl-a)−1h−1) and the maximum light utilization coefficient, αB, ranged from 0.017 to 0.806 (mgC(mgChl−a)−1(Wm−2)−1h−1). These data and previously published P–E curve parameter estimates were used in a spectrally varying model to estimate integrated primary production in the Sargasso Sea euphotic zone. Output from two of the four primary production models agreed well with in-situ measurements (±20%) and captured the strong seasonal variation.

Spatio-temporal distribution of chlorophyll-a in relation to physico-chemical parameters in coastal waters of the northwestern Bay of Bengal.

The present study focuses on understanding the long-term distribution of physico-chemical parameters and their influence on the distribution of chlorophyll-a (chl-a) at a coastal site in the northwestern Bay of Bengal. Chl-a showed large variability (0.12 to 10.05mgm(-3)) on a spatio-temporal scale during the study period. However, the distribution showed a similar pattern with marginal variability from March 2010 to February 2011 and March 2011 to February 2012. The vertical distribution of salinity, pH, total suspended matter (TSM) and chl-a showed systematic temporal variability. However, dissolved oxygen (DO) and nutrients (nitrite+nitrate, phosphate, silicate) did not show any significant spatio-temporal trend. Chl-a showed bimodal distribution on an annual scale, with the first peak appearing during the pre-monsoon period in March due to a seasonal phytoplankton bloom, whereas the second peak occurring during September as a result of nutrient loading from river influx due to monsoonal precipitation. Factor analysis revealed the association of low salinity and high nutrients with chl-a. This infers that the nutrients brought by the influx of river into the study area were fuelling the growth and abundance of phytoplankton. Cluster analysis resulted in two distinct clusters among all physico-chemical datasets, indicating the presence of two distinct areas separated by the 30 m isobath that were strongly influenced by physico-chemical characteristics associated with the seasonal monsoon.

Assessing Potential Algal Blooms in a Shallow Fluvial Lake by Combining Hydrodynamic Modelling and Remote-Sensed Images

Shallow fluvial lakes are dynamic ecosystems shaped by physical and biological factors and characterized by the coexistence of phytoplankton and macrophytes. Due to multiple interplaying factors, understanding the distribution of phytoplankton in fluvial lakes is a complex but fundamental issue, in the context of increasing eutrophication, climate change, and multiple water uses. We analyze the distribution of phytoplankton by combining remotely sensed maps of chlorophyll-a with a hydrodynamic model in a dammed fluvial lake (Mantua Superior Lake, Northern Italy). The numerical simulation of different conditions shows that the main hydrodynamic effects which influence algal distribution are related to the combined effect of advection due to wind forces and local currents, as well as to the presence of large gyres which induce recirculation and stagnation regions, favoring phytoplankton accumulation. Therefore, the general characters of the phytoplankton horizontal patchiness can be inferred from the results of the hydrodynamic model. Conversely, hyperspectral remote-sensing products can be used to validate this model, as they provide chlorophyll-a distribution maps. The integration of ecological, hydraulic, and remote-sensing techniques may therefore help the monitoring and protection of inland water quality, with important improvements in management actions by policy makers.

Reprint of: Chlorophyll enhancement in the central region of the Bay of Biscay as a result of internal tidal wave interaction

A multi-sensor satellite approach based on ocean colour, sunglint and Synthetic Aperture Radar imagery is used to study the impact of interacting internal tidal (IT) waves on near-surface chlorophyll-a distribution, in the central Bay of Biscay. Satellite imagery was initially used to characterize the internal solitary wave (ISW) field in the study area, where the “local generation mechanism” was found to be associated with two distinct regions of enhanced barotropic tidal forcing. IT beams formed at the French shelf-break, and generated from critical bathymetry in the vicinities of one of these regions, were found to be consistent with “locally generated” ISWs. Representative case studies illustrate the existence of two different axes of IT propagation originating from the French shelf-break, which intersect close to 46°N, −7°E, where strong IT interaction has been previously identified. Evidence of constructive interference between large IT waves is then presented and shown to be consistent with enhanced levels of chlorophyll-a concentration detected by means of ocean colour satellite sensors. Finally, the results obtained from satellite climatological mean chlorophyll-a concentration from late summer (i.e. September, when ITs and ISWs can meet ideal propagation conditions) suggest that elevated IT activity plays a significant role in phytoplankton vertical distribution, and therefore influences the late summer ecology in the central Bay of Biscay.

Retrieving the evolution of vertical profiles of Chlorophyll-a from satellite observations using Hidden Markov Models and Self-Organizing Topological Maps

We present a statistical method, denoted PROFHMM, to infer the evolution of the vertical profiles of oceanic biogeophysical variables from sea-surface data. This method makes use of discrete Hidden Markov Models whose states are defined through Self-Organizing Topological Maps. The Self-Organizing Topological Maps are used to provide the states of the Hidden Markov Model, as well as improve its parameters. After introducing the general principles of PROFHMM, we present the results obtained in a case study in which the evolution of the vertical profiles of Chlorophyll-a was inverted from sea-surface data. We applied PROFHMM for the reconstruction of the evolution of the vertical distribution of Chlorophyll-a at BATS, by training it on the numerical outputs of the NEMO-PISCES model, and reproducing the evolution of this model by using a sequence satellite observations. We obtained a root mean square error of 0.0399ng/l for the validation year 2008.

Variability of environmental heterogeneity in northern Patagonia, Chile: effects on the spatial distribution, size structure and abundance of chlorophyll-a

La cadena de islas incluyendo Desertores-Apiao y Quemchi situada en el Mar Interior de Chiloe, en la Patagonia chilena norte (41-44°S), actua como una barrera natural para el flujo de agua en direccion norte-sur que influye en el intercambio y circulacion entre las micro cuencas norte y sur. La micro cuenca norte se caracteriza por el dominio de las aguas estuarinas superficiales mientras que la micro cuenca sur se encuentra afectada por aguas Subantarticas y Ecuatoriales Subsuperficiales desde el oceano costero adyacente. Esta situacion determina diferencias claves en la distribucion espacial, abundancia y composicion por tamano de la biomasa autotrofica (medida como clorofila-a). Estas diferencias cuali y cuantitativas de clorofila-a se evaluaron en dos epocas contrastantes durante expediciones en 2004 y 2005 (Cruceros de Investigacion Marina, CIMAR 10 y 11 Fiordos). En ambas micro cuencas, se analizaron parametros fisicos, quimicos y bio-opticos de la capa de mezcla superficial junto con imagenes satelitales compuestas de 8 dias de clorofila-a (MODIS-AQUA). La principal diferencia de la heterogeneidad ambiental entre zonas fue determinada por la concentracion de nitratos y acido silicico. En primavera la abundancia de la clorofila-a mostro alta variabilidad en ambas micro cuencas y con predominancia del micro-fitoplancton. En el invierno austral el micro-fitoplancton tambien fue dominante en una amplia gama de condiciones ambientales, pero estrechamente vinculada a zonas con alta concentracion de acido silicico. Las fracciones mas pequenas, sin embargo, dominaron en un entorno mas homogeneo caracterizado por una mayor concentracion de nitratos. Aunque los nutrientes no se agotan en el area de estudio, la razon nitrato/acido silicico influencia claramente la abundancia, la composicion por tamano y la estructura espacial de la comunidad autotrofica durante invierno bajo menor disponibilidad de luz y procesos oceanograficos mas complejos durante la primavera.

Phytoplankton distribution during the winter convective season in Sendai Bay, Japan

We investigated the elevated chlorophyll-a (Chl-a) zone found along the coast in winter in Sendai Bay, Japan, using hydrographic observations and a one-dimensional ecosystem model. Chlorophyll-a distribution was vertically homogeneous with a horizontal gradient and could be approximated as a power function of bottom depth; Chl-a concentration drastically increased with decreasing bottom depth, despite temperature and salinity being almost vertically and horizontally homogeneous. The observed results revealed significant correlations among Chl-a and nutrients concentrations proportional to the Redfield ratio. Diatoms accounted for more than 99% of the detected total cells, indicating the occurrence of a diato m bloom. A one-dimensional ecosystem model, which incorporated vertical mixing and the self-shading effect of phytoplankton, revealed that bottom depth was responsible for the occurrence of the bloom during the convective season in coastal area where vertical mixing reached the bottom and that there existed the critical bottom depth where the integrated Chl-a in the water column remained constant. A bloom could occur where the bottom depth is shallower than the critical bottom depth, not when the depth of the mixed layer is shallower than the classical critical depth and the stratification is established. From the observational and model results, it is suggested that the diatom bloom was induced by oceanic water intrusion, which transported nutrients to the bay and the elevated Chl-a zone was formed within a month after the intrusion.

Physical forcing mechanisms controlling the variability of chlorophyll-a over the Royal-Charlotte and Abrolhos Banks-Eastern Brazilian Shelf.

The Abrolhos Bank is part of the so-called Eastern Brazilian Shelf and is an area of high ecological and economic importance. The bank supports the largest and richest coral reefs in the South Atlantic and the largest rhodolith bed in the world. The spatial and seasonal variation of phytoplankton concentration, however, and the dynamic processes controlling that variability have remained poorly known. The present study investigates the seasonal and spatial distributions of chlorophyll-a (Chl-a) and water conditions by analyzing nine years (2003–2011) of level-3 Moderate-resolution Imaging Spectroradiometer (MODIS) derived Chl-a, National Centers for Environmental Prediction (NCEP)/ETA model-derived winds, NCEP model-derived heat fluxes, thermohaline and velocity results from the Hybrid Circulation Ocean Model (HYCOM) 1/12o assimilated simulation. The results show that low/high concentrations occurred in austral spring-summer (wet season)/autumn-winter (dry season), with the highest values observed in the northern portion of the Abrolhos Bank. The typical meteorological and oceanographic conditions during austral summer favor the development of strong stratification. These conditions are 1) N-NE winds that favor an upwelling-type Ekman circulation; 2) coupling between the open ocean and the continental shelf through the western boundary current, which promotes cooler subsurface water to rise onto the shelf break; and 3) positive net heat flux. In contrast, the S-SE winds during autumn are in the opposite direction of the predominant current system over the Abrolhos Bank, thus reducing their speed and inducing an inverse shear. The warmer ocean and a somewhat cool and dry atmosphere promote the evaporative cooling of the surface layer. The above processes drive mixed layer cooling and deepening that reaches its maximum in winter. The blooming of phytoplankton in the Abrolhos Bank waters appears to be regulated by changes in the mixed layer depth, with Chl-a levels that start to increase during autumn and reach their peak in June-July.

Temporal and spatial distribution of phytoplankton chlorophyll-a and its relationships with environmental factors in Dongjiang River, Pearl River basin

为了解珠江流域东江干流水体叶绿素a的时空分布及与环境因子的关系,于2012年6月(丰水期)和12月(枯水期)对东江干流进行采样调查分析.结果表明,东江水体叶绿素a含量具有明显的时空分布特征,其全年变化范围为0.84~14.93μg/L,整体均值为3.60±2.45μg/L,丰水期叶绿素a含量显著高于枯水期;而丰、枯水期叶绿素a含量空间分布特征相似,上游河段显著低于下游河段.相关性与主成分分析结果显示,水体中总氮浓度、总磷浓度、有机物含量、水温和水流流速等都是影响东江浮游植物生长的重要因素,其中以总磷的影响最为显著,表明磷可能是东江浮游植物生长的限制因子.;Sampling was carried out in wet season and dry season of 2012 in order to analyze the distribution of chlorophyll-a and the effects of water environment factors on chlorophyll-a in Dongjiang River, Pearl River basin. Results showed chlorophyll-a concentration appeared strong temporal and spatial variations in Dongjiang River, ranging from 0.84 to 14.93μg/L, and with the annual mean value of 3.60±2.45μg/L. The chlorophyll-a concentration in wet season was obviously higher than that in dry season. For wet and dry season, the temporal distribution of chlorophyll-a had a similar pattern, increasing from upstream to downstream. The correlation analysis and principal components analysis indicated TN, TP, COD_Mn, water temperature and flow velocity were the most important factors for the growth of phytoplankton in Dongjiang River, and phosphorous might be the limiting factor because of its remarkable influence on phytoplankton.

Distribution and Seasonal Variation of Nutrient Salts and Chlorophyll-a in Surface Seawater Along Alexandria Costal Zone Area

The aim of the present study is to investigate the hydrographic characteristics, nutrient salts and chlorophyll-a (Chl-a) along Alexandria Costal Zone Area. The study revealed that the pH values lie slightly in the alkaline side, with a range of 7.53 to 8.12, salinity showed a slightly variation, it ranged from 35.34 to 38.28 PSU, the values of dissolved oxygen were fluctuated between 4.77 and 11.13 mgl-1. The annual average of nutrients (μM) was as follow: (7.97 ± 1.72), (0.66 ± 0.14), (2.18 ± 0.73), (0.37± 0.09) and (12.42 ± 4.04) for nitrate, nitrite, ammonium, reactive phosphate and silicate, respectively. Relatively high levels of Chl-a concentrations was recorded during the period of study ranged from 0.38 to 6.96µgl-1 and a positive correlation was found between Chl-a and both NO3, NH4, PO4 and SiO4 (r= 0.383, 0.303, 0.213 and 0.341, respectively). Very high values of N/P ratio were recorded during the study period, this consideration showed that Phosphorus was limiting factor in the study area.

Locality of Chlorophyll-A Distribution in the Intensive Study Area of the Ariake Sea, Japan in Winter Seasons based on Remote Sensing Satellite Data

Mechanism of chlorophyll-a appearance and its locality in the intensive study area of the Ariake Sea, Japan in winter seasons is clarified by using remote sensing satellite data. Through experiments with Terra and AQUA MODIS data derived chlorophyll-a concentration and truth data of chlorophyll-a concentration together with meteorological data and tidal data which are acquired for 6 years (winter 2010 to winter 2015), it is found that strong correlation between the chlorophyll-a concentration and tidal height changes. Also it is found that the relations between ocean wind speed and chlorophyll-a concentration. Meanwhile, there is a relatively high correlation between sunshine duration a day and chlorophyll-a concentration. Furthermore, it is found that there are different sources of chlorophyll-a in the three different sea areas of Ariake Sea area in the back, Isahaya bay area, and Kumamoto offshore area.

Landsat-8 OLI를 이용한 북극해 스발바드 피요르드의 고해상도 Ocean Color Product 산출

Ocean Color products have been used to understand marine ecosystem. In high latitude region, ice melting optically influences the ocean color products. In this study, we assessed optical properties in fjord around Svalbard Arctic sea, and estimated distribution of chlorophyll-a and suspended sediment by using high resolution satellite data, Landsat-8 Operational Land Imager (OLI). To estimate chlorophyll-a and suspended sediment concentrations, various regression models were tested with different band ratio. The regression models were not shown high correlation because of temporal difference between satellite data and in-situ data. However, model-derived distribution of ocean color products from OLI showed a possibility that fjord and coastal areas around Arctic Sea can be monitored with high resolution satellite data. To understand climate change pattern around Arctic Sea, we need to understand ice meting influences on marine ecosystem change. Results of this study will be used to high resolution monitoring of ice melting and its influences on the marine ecosystem change at high latitude. KOPRI (Korea Polar Research Institute) has been operated the Dasan station on Svalbard since 2002, and study was conducted using Arctic station.

Is the East Australian Current causing a marine ecological hot-spot and an important fisheries near Fraser Island, Australia?

The distributions of chlorophyll-a (Chl-a) blooms near the Fraser Island continental shelf along the east coast of Australia were analysed for the period 2002–2012. The blooms were found to exhibit two distinct quasi-climatological patterns. The first pattern was a broad near-coast mid-shelf distribution that prevailed from about March to July each year. The second pattern was established due to re-occurring outer-shelf Chl-a blooms southeast of Fraser Island from about August to February. The outer-shelf Chl-a bloom concentration maxima appeared to be higher than those associated with the near coast pattern. Both distributions were found to be characterised by significant year-to-year variability in the number of total blooms, the length of blooms and the Chl-a bloom concentration maxima. The physical cause of the outer-shelf Chl-a concentration maxima was of particular interest, since this location overlaps with a region previously identified as a key eastern Australian marine ecological site and important fisheries. In this analysis, we found that the area also overlaps with a hot-spot in EAC-generated bottom layer stress, which appears to be the main driver of the “Southeast Fraser Island Upwelling System”.

Estimating trans-seasonal variability in water column biomass for a highly migratory, deep diving predator.

The deployment of animal-borne electronic tags is revolutionizing our understanding of how pelagic species respond to their environment by providing in situ oceanographic information such as temperature, salinity, and light measurements. These tags, deployed on pelagic animals, provide data that can be used to study the ecological context of their foraging behaviour and surrounding environment. Satellite-derived measures of ocean colour reveal temporal and spatial variability of surface chlorophyll-a (a useful proxy for phytoplankton distribution). However, this information can be patchy in space and time resulting in poor correspondence with marine animal behaviour. Alternatively, light data collected by animal-borne tag sensors can be used to estimate chlorophyll-a distribution. Here, we use light level and depth data to generate a phytoplankton index that matches daily seal movements. Time-depth-light recorders (TDLRs) were deployed on 89 southern elephant seals (Mirounga leonina) over a period of 6 years (1999–2005). TDLR data were used to calculate integrated light attenuation of the top 250 m of the water column (LA250), which provided an index of phytoplankton density at the daily scale that was concurrent with the movement and behaviour of seals throughout their entire foraging trip. These index values were consistent with typical seasonal chl-a patterns as measured from 8-daySea-viewing Wide Field-of-view Sensor (SeaWiFs) images. The availability of data recorded by the TDLRs was far greater than concurrent remotely sensed chl-a at higher latitudes and during winter months. Improving the spatial and temporal availability of phytoplankton information concurrent with animal behaviour has ecological implications for understanding the movement of deep diving predators in relation to lower trophic levels in the Southern Ocean. Light attenuation profiles recorded by animal-borne electronic tags can be used more broadly and routinely to estimate lower trophic distribution at sea in relation to deep diving predator foraging behaviour.

The permanent ice cover of Lake Bonney, Antarctica: The influence of thickness and sediment distribution on photosynthetically available radiation and chlorophyll-a distribution in the underlying water column

The thick permanent ice cover on the lakes of the McMurdo Dry Valleys, Antarctica, inhibits spatial lake sampling due to logistical constraints of penetrating the ice cover. To date most sampling of these lakes has been made at only a few sites with the assumption that there is a spatial homogeneity of the physical and biogeochemical properties of the ice cover and the water column at any given depth. To test this underlying assumption, an autonomous underwater vehicle (AUV) was deployed in Lake Bonney, Taylor Valley. Measurements were obtained over the course of 2 years in a 100 × 100 m horizontal sampling grid (at a 0.2 m vertical resolution). Additionally, the AUV measured the ice thickness (in water equivalent) and collected images looking up through the ice, which were used to quantify sediment distribution on the surface and within the ice. Satellite imagery was used to map sediment distribution on the surface of the ice. We present results of the spatial investigation of the sediment distribution on the ice cover and its effects on biological processes, with particular emphasis on photosynthetically active radiation (PAR). The surface sediment is a secondary controller of the ice cover thickness, which in turn controls the depth-integrated PAR in the water column. Our data revealed that depth-integrated PAR was negatively correlated with depth-integrated chlorophyll-a (r = 0.88, p < 0.001, n = 83), which appears to be related to short-term photoadaptation of phytoplanktonic communities to spatial and temporal variation in PAR within the water column.