Variability Of Chlorophyll-a Research Articles

A first description of the summer upwelling off the Bay of Algeciras and its role in the northwestern Alboran Sea

A local upwelling process is observed in the mouth of the Bay of Algeciras showing a singular pattern, partially disengaged of the neighboring coastal upwelling variability. The physical mechanisms which drive this local upwelling are not clear, but the Ekman pumping seems to be the most important forcing factor. The surface chlorophyll-a variability associated with this local upwelling is uncorrelated with the concentration registered in the inner Bay of Algeciras or in the surrounding coastal and shelf waters. Secondary, the emerged waters in the mouth of the Bay of Algeciras flow eastwards into the northwestern Alboran Sea dragged by the northern edge of the Atlantic Jet, forming a narrow and elongated nutrient-enriched area (hereafter called filament) usually detached from the coast. A sampling station located at 14.6 km from the coastline and 68 km far from the mouth of the Bay of Algeciras was employed to monitor the presence of the filament in the Alboran Sea. The filament is most frequently presented during the summer (in fact, it was detectable in more than 50% of the days of august). When the filament is distinguishable, its chlorophyll-a concentration doubles in average the values registered in neighboring locations, and in annual average also higher nitrate and phosphate surface concentrations (about 30%) are registered at the filament location. These results indicate that the filament provides nutrients to the surface waters of Alboran not only when it is optically detected. Our analyses indicate that the trajectory of the filament follows the northern edge of the western gyre of Alboran although its width and speed are variable depending on the Atlantic Jet properties and the related sub-mesoscale activity.

Development of a Biogeochemical and Carbon Model Related to Ocean Acidification Indices with an Operational Ocean Model Product in the North Western Pacific

We developed a biogeochemical and carbon model (JCOPE_EC) coupled with an operational ocean model for the North Western Pacific. JCOPE_EC represents ocean acidification indices on the background of the risks due to ocean acidification and our model experiences. It is an off-line tracer model driven by a high-resolution regional ocean general circulation model (JCOPE2M). The results showed that the model adequately reproduced the general patterns in the observed data, including the seasonal variability of chlorophyll-a, dissolved inorganic nitrogen/phosphorus, dissolved inorganic carbon, and total alkalinity. We provide an overview of this system and the results of the model validation based on the available observed data. Sensitivity analysis using fixed values for temperature, salinity, dissolved inorganic carbon and total alkalinity helped us identify which variables contributed most to seasonal variations in the ocean acidification indices, pH and Ωarg. The seasonal variation in the pHinsitu was governed mainly by balances of the change in temperature and dissolved inorganic carbon. The seasonal increase in Ωarg from winter to summer was governed mainly by dissolved inorganic carbon levels.

Mismatched seasonal patterns of larval production and quality in subtropical barnacle populations along a coastal trophic gradient

The seasonal breeding patterns of a wide array of marine invertebrates are shaped by strong and deterministic environmental factors over their geographic distribution range, such as temperature or photoperiod. Whether or not such patterns will remain adaptive at more localized scales may depend on how consistent are secondary drivers controlling resource supply to parents and offspring. We address this question by examining the seasonal patterns of both the trophic state of coastal waters, and larval production and quality produced by a filter-feeding invertebrate, the intertidal barnacle Chthamalus bisinuatus, along a 150 km long trophic gradient in Southeastern Brazil. Results are consistent to previous remote sensing work showing strong seasonal variation of chlorophyll-a and particulate organic carbon concentrations, increasing 2 to 2.5 times from summer – early autumn to winter, compatible to enhanced production through vertical mixing caused by passing cold fronts. The spatial gradient was also verified and found to be consistent between seasons, but contrasts were of smaller magnitude (coefficients of variations between 15 and 35%). All reproductive parameters showed important seasonal but no spatial trends. Larval production was much higher in summer-early autumn, agreeing with previous results based on gonad development and early recruitment rate for this same species and published results for other chthamalids. However, per capita parental transfer of neutral fatty acids to larvae and larval survival without exogenous food increased 2 and 1.4 times from the breeding to the non-breeding season, respectively, indicating that coastal oceanographic processes favor larval quality when reproductive activity is lower. Given that food limitation is likely frequent in the study region, shifting from oligotrophic to mesotrophic, and that effects of larval nourishing can be carried over to benthic barnacle stages, results also suggest that the contribution of out-of-season offspring to overall recruitment may be disproportionately higher.

SPATIAL DISTRIBUTIONS OF NUTRIENTS AND CHLOROPHYLL-A: A POSSIBLE OCCURRENCE OF PHOSPHORUS AS A EUTROPHICATION DETERMINANT OF THE JAKARTA BAY

Phytoplankton blooms due to nutrient enrichment (eutrophication) have been considered as the primary factor causing several massive fish kills occurred in the Jakarta Bay. This study aims to determine the spatial variation of phytoplankton abundance based on chlorophyll-a concentration and its relationship with nutrient level and composition. A field observation was conducted in July 2015 measuring chlorophyll-a and nutrient concentrations. Chlorophyll-a was measured using fluorometer Trilogy AU-10 while nutrients was using spectrophotometer Shimadzu UV-1800. The result showed that chlorophyll-a concentration was relatively higher in the western compared to the eastern region of the Jakarta Bay. In addition, the western region was high in orthophosphate, nitrate and silicate while the eastern region was high in ammonium and nitrate. Statistical analysis shows that chlorophyll-a had the highest significant correlation against orthophosphate in the western region and chlorophyll-a had no significant correlation with nutrients in the eastern region. It seems that phosphorus was the primary determinant of chlorophyll-a variability with a concentration of orthophosphate of more than 0.028 mg P/L is required to increase chlorophyll-a concentration. In addition, low orthophosphate concentration (0.014 mg P/L) below its minimum requirement for maximum phytoplankton growth was likely the factor causing the absence of chlorophyll-a and nutrients relationship in the eastern region. In summary, phosphorus is seemingly the primary eutrophication determinant in the Jakarta Bay.

Phytoplankton diversity and trophic status of Lake Maninjau, West Sumatra, Indonesia

Abstract. Sulastri, Henny C, Nomosatryo S. 2019. Phytoplankton diversity and trophic status of Lake Maninjau, West Sumatra, Indonesia. Pros Sem Nas Masy Biodiv Indon 5: 242-250. Microcystis blooms have been recorded in Lake Maninjau in 2000, October 2011 and recently on April 2018. Microcystis bloom was characterized by green color enhancement in the column water due to high concentration of chlorophyll-a reach to > 100 µg.L-1. The occurrence of phytoplankton bloom in this lake was not recorded all the year but Microcystis was disappeared and the water is clear again in a certain period. This study was aimed to reveal phytoplankton diversity and relation to trophic status in Lake Maninjau. Phytoplankton diversity and water quality include water transparency, temperature, DO, pH, conductivity, and nutrient were observed in 2009, 2014, 2015, 2016 dan 2018. Phytoplankton sample and water quality parameters were measured in the euphotic zone at nine stations. Three variable chlorophyll-a, Secchi depth (transparency) and total phosphorus concentration used to calculate the trophic state index. There are 121 species of phytoplankton belong to phylum Chlorophyta (74 species), Cyanophyta (23 species), Pyrrhophyta (7 species) dan Euglenophyta (4 species). The trophic status in Lake Maninjau showed variability temporally; it was mesotrophic, meso-eutrophic, eutrophic and hiper-eutrophic. Hypereutrophic status was characterized by low phytoplankton diversity (27 species), high chlorophyll-a, nutrient concentration, and Microcystis aeruginosa abundance (4180.932 x 103 individual.L-1). Mesotrophic was characterized by high phytoplankton diversity (63 species) belong to phylum Chlorophyta especially family Desmidiaceae, Oocyataceae, Scenedesmusceae, and low nutrient concentration. The higher trophic status is more decrease phytoplankton diversity.

Vertical Structure of the Water Column at the Virgin Islands Shelf Break and Trough

The steep US Virgin Islands Shelf Break (VISB) and the Virgin Islands Trough (VIT) at the Northeastern Caribbean Sea comprise a dynamic region of the Atlantic Ocean. In situ oceanographic data collected in the region during April 2017 were used to examine the spatial variability in temperature, density, salinity, and relative Chlorophyll-a. Analysis of data from the upper 300 m of the water column, that include deep and shallow water stations in the shelf break region, shows strong stratification of the water column. Stations shallower than 800 m along the shelf break are more variable in temperature, density, and salinity than those that are deeper than 800 m along the trough. For shallow stations, the mixed layer depth deepens along-shelf from West to East while at the deep stations the opposite occurs. Salinity maxima exhibit more variability in depth and range of values in the shallow stations compared to deep stations. Six different types of water masses that contribute to the strong stratification in the region were identified in our study: Caribbean Surface Water, Subtropical Underwater, Sargasso Sea Water, Tropical Atlantic Central Water, Antarctic Intermediate Water, and North Atlantic Deep Water. The upper level Caribbean Surface Water, Subtropical Underwater, and Sargasso Sea Water are present in shallow stations, indicating potential meridional intrusions from the VIT to the VISB which may not be resolved by current ocean circulation models and are not captured in satellite data. The analysis presented here indicates that competing physical processes may be controlling the vertical structure of the water column in the region and merit further examination.

The Effect of the ENSO on the Variability of SST and Chlorophyll-a in the South China Sea

The South China Sea (SCS) is one of the western marginal oceans of the Pacific Ocean, surrounded by South China, the Indo Peninsula of China, Peninsular Malaysia, the Philippines, and Borneo Island. The effect of the ENSO on the Variability of SST and chlorophyll-a has been investigated by many researchers. However, in the study, there were not still a small number of researchers who studied in this SCS area using high-resolution satellite imagery data. Chlorophyll-a and SST data taken from MODIS data, and wind analysis data from CCMP (Cross Calibrate Multi-Platform). The results obtained, wind speed affects over changes SST and Chlorophyll-a at SCS. The influence of wind speed against the variability of SST is very strong, but otherwise, over variability of Chlorophyll-a is less impact. There is a high correlation between ENSO (El Nino) with the SST which tends to be dominant throughout the west season due to the influence of wind speed in the South China Sea from the Pacific towards Australia throughout the west season. However, this is in contrast to the correlation between ENSO and Chlorophyll-a which appears less dominant, which is suspected of other factors that may affect Chlorophyll-a anomalies in addition to wind and SST factors.

Proposal of a trophic state index in semiarid reservoirs using data of the Banabuiú Basin, state of Ceará, Brazil

Abstract Aim This study aimed to develop a Trophic State Index that simulates the cumulative impact in 18 reservoirs in the Banabuiú basin, located in the semiarid region of the State of Ceará. Methods Analyses were made for physical (temperature, transparency and turbidity), chemical (dissolved oxygen, pH and total phosphorus) and biological (chlorophyll-a) variables as indicators of reservoir water quality. Data used in this study were made available by the Water Resources Management Company of the State of Ceará (COGERH), in the years between 2010 and 2013. An adaptation was developed for trophic classification (TSISA), incorporating the three most relevant variables for trophic evaluation, total phosphorus, chlorophyll-a and transparency. For interpreting the data set, we used multivariate statistics as Hierarchical Cluster Analysis (HCA) and Factor Analysis/Principal Component Analysis (PCA). Results The similarity of Banabuiú basin reservoirs in relation to water eutrophication gave rise to three distinct groups: I, II and III consisting of nine, four and five reservoirs, respectively. The calculation of minimum and maximum values and percentiles of the correlated parameters defined four classes of trophic state; it was observed that the reservoirs in the group I showed trophic classification predominantly between oligotrophic (54.7%), mesotrophic (30.2%), group II, eutrophic (44.4%) and hypertrophic (33.3%) and those of the group III, eutrophic (39.1%) and hypertrophic (60.9%). Conclusions The TSISA presented a simple methodology and easy interpretation of the data, grounded in the quality of water of reservoirs located in the semiarid region of Ceará. Thus, its use can contribute for the reduction of errors in the inference of the trophic state of reservoirs in this region and should be considered as an indicator for more detailed studies.

The influence of physical-chemical variables on the spatial and seasonal variation of Chlorophyll-a in coastal waters of Unguja, Zanzibar, Tanzania

Chlorophyll-a (Chl-a) concentrations were measured at four sites around Unguja, Zanzibar during the northeast (NE) and southeast (SE) monsoon seasons. Data for Chl- a , nitrate, phosphate, ammonia, dissolved oxygen, sea sur - face temperature, pH and salinity were collected once a month from March 2008 to March 2009. The SE monsoon had insignificantly higher Chl- a compared to the NE monsoon season when Chl- a for Bawe, Chumbe, Pongwe and Mnemba were combined (W = 234, p = 0.93). The drivers of high Chl- a during the SE monsoon were ammonia and nitrate. Results from individual sites showed that Pongwe and Mnemba had higher median Chl- a during the SE- than the NE monsoon season. Temperature, dissolved oxygen and ammonia were the major factors that influenced high Chl- a at these sites. In contrast, Chumbe and Bawe had higher median Chl- a during the NE- than the SE mon- soon season. The major factors influencing high Chl- a in the NE at Chumbe and Bawe were high levels of nutrients, mainly from sewage effluent and various human activities around the coast in Zanzibar town. The interaction of Chl- a between monsoon seasons (NE and SE) and sites (Bawe, Chumbe, Pongwe and Mnemba) was insignificant (F (1,3) = 1.3144, p = 0.2949). The principal component analysis revealed that different physical and chemical environmental variables affect Chl- a concentration over time and location.

VARIABILITY OF CHLOROPHYLL-A DISTRIBUTION AROUND BELITUNG ISLAND WATERS OBSERVED BY AQUA-MODIS SATELLITE DATA

<p>Belitung Island has a strategic geographical location, which is directly bordered with Sumatera and Kalimantan also Karimata and Malacca Straits. Those conditions make the waters productivity being high due to the support from the biogeochemical cycle, nutrient runoff, and upwelling. This study aims to determine the seasonal variability of chlorophyll-a (Chl-a) around Belitung waters. The method used in this study was spatial analysis with IDW (inverse distance weighted) to interpolate the Chl-a surface distribution. Sea Surface Temperature (SST) acquired from Aqua-MODIS were retrieved from NASA (National Aeronautics and Space Administration) and wind data were obtained from ECMWF (European Centre for Medium-Range Weather Forecasts), data were analyzed statistically and spatially. The Chl-a concentration in the northeast monsoon ranged 0.38-3.5 mg.m-3, in the southwest monsoon ranged 0.15-18.7 mg.m-3, and in the transitional season ranged 0.29-9.04 mg.m-3. The Chl-a concentration during southwest and 1st transitional monsoons were higher due to the maximum sunlight intensity stimulating photosynthesis of autotroph biota. The condition of SST is indicating the upwelling event that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface. Seasonal SST variability ranged 22.6-28.3oC, 27.3-32.1oC, 30.7-32.3oC, and 29.1-32.8oC during northeast, 1st transitional, southwest, and 2nd transitional monsoons respectively. The existence of ENSO (El-Nino Southern Oscillation) contributes to enhance the Chl-a concentration. During ENSO years, the Chl-a concentration was higher than non-ENSO years due to the great impact of ENSO inducing upwelling and higher nutrient availability. Chl-a and SST conditions can be used to predict fishing ground and upwelling area. </p>

Variability of surface chlorophyll-a distributions in the northwestern coast of Sumatra revealed by MODIS

The variability of surface chlorophyll-a (chl-a) distributions in the northwestern coast of Sumatra are important components associated with the phytoplankton biomass that supports and enrich the fishery resources of the region. This study analyzes satellite data-ocean color derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua for a period of January 2003 to December 2015. The results show that the surface chl-a distribution is strongly associated with the large-scale forcing (e.g. monsoonal winds, EL Niño–Southern Oscillation and the Indian Ocean Dipole). On the seasonal time scale, it is shown that the satellite observed surface chl-a concentration during the boreal fall and winter (September-January) is higher than that observed during the boreal summer (June-August). The highest concentration was observed in September which is about 0.2 mg m-3. In contrast to the western coast, the surface chl-a in the eastern coast of Sumatra has excessive concentration around 0,5-10 mg m-3 all year around. In addition, the study also revealed that the anomaly of surface chl-a concentration was observed along the western coast of Sumatra is much higher during the positive IOD (pIOD) and EL Niño events.

Water clarity measures as indicators of recreational benefits provided by U.S. lakes: Swimming and aesthetics

Lakes provide recreational benefits related to water quality. Using data from the 2007 and 2012 United States National Lake Assessments (N = 2067 lake visits), we developed indicators for three benefits: swimming, general recreational value, and aesthetic appeal. For two combined ecoregions (“Mountains” and “Plains”) we related objective measures of water clarity, including Secchi depth, turbidity, and water-column chlorophyll-a concentration to subjective visual assessments of recreational benefit quality. There were significant associations between water clarity measures and visual assessments from which we derived water-clarity based thresholds between benefit quality classes (exceptional, high, low, marginal) for each benefit type. More variation in Secchi depth and turbidity was explained by benefit quality than was variation in chlorophyll-a. Threshold values were different between combined ecoregions. Compared to lakes in the Mountains ecoregion, recreational users of Plains lakes have lower expectations for water clarity. Thresholds were generally in accord with water clarity thresholds and guidance derived from published regional studies. Including indicators of the quality of benefits humans receive from lakes in assessments of lake conditions can increase public participation in decision-making and reveal changes in benefit quality over time.

Chlorophyll-A variability in the southern coast of Java Island, Indian Ocean: corresponding to the tropical cyclone of Ernie

Tropical cyclone is an atmospheric phenomenon formed above warm ocean in a tropical region. Generally, tropical cyclone gives negative impact, such as extreme rainfall, strong winds, and extreme wave height. On the other hand, however, tropical cyclone gives positive impact on triggering the ocean fertility by induced chlorophyll-a concentration caused by vertical mixing and upwelling in the ocean. Related to this, a study has been conducted to determine the concentration of chlorophyll-a after the occurrence of Ernie cyclone in Indian ocean near western part of Australia and along the southern coast of Java island. The data that used in this study is daily wind speed data from 5 - 11 April 2017, daily average data of SST from 5 - 11 April 2017, and 8-day composite data of chlorophyll-a data from Aqua-MODIS satellite. The analysis of chlorophyll-a concentration showed a slow response of ocean fertility increment in the southern coast of Java island. Chlorophyll-a concentration along the cylone trajectory prior to the cyclone was in the range of 0.08 mg/m3 – 0.15 mg/m3 and significantly increased up to 88%–100% in a week after the occurrence of cyclone. On the next third and fourth weeks after cyclone, the concentration of chlorophyll-a along the cyclone trajectory decreases gradually. Meanwhile its sea surface temperature decreased significantly, especially in areas where cyclone had passed.

A Multivariate Analysis Framework to Detect Key Environmental Factors Affecting Spatiotemporal Variability of Chlorophyll-a in a Tropical Productive Estuarine-Lagoon System

Here, we demonstrate how a combination of three multivariate statistic techniques can identify key environmental factors affecting the seasonal and spatial variability of chlorophyll-a (Chl-a) in a productive tropical estuarine-lagoon system. Remote estimation of Chl-a was carried out using a NIR-Red model based on MODIS bands, which is highly consistent with the in situ measurement of Chl-a with root mean square error (RMSE) of 15.24 mg m−3 and 13.43 mg m−3 for two independent datasets used for the model’s calibration and validation, respectively. Our findings suggest that the river discharges and hydraulic residence time of the lagoons promote a stronger effect on the spatial variability of Chl-a in the coastal lagoons, while wind, solar radiation and temperature have a secondary importance. The results also indicate a slight seasonal variability of Chl-a in Mundaú lagoon, which are different the from Manguaba lagoon. The multivariate approach was able to fully understand the relative importance of key environmental factors on the spatiotemporal variability of Chl-a of the aquatic ecosystem, providing a powerful tool for reducing dimensionality and analyzing large amounts of satellite-derived Chl-a data.

The Role of Confluence in Shaping Water Quality Parameters on Example of the Flow-Through Lake Bikcze (Eastern Poland)

The role of confluence (flowability) in shaping the concentration of dissolved oxygen (DO), chlorophyll-a (chl-a) and pH was determined using a model approach. The calculations considered both horizontal and vertical variability of parameters. There was a general tendency for the pH and oxygen to increase along the transect connecting the place of surface water inlet, deepest point of the lake basin and the place of water outlet, and the reverse tendency for chlorophyll. The average gradient for particulate radius was calculated as arithmetic mean value of six partial gradients (corresponding to individual depths, every 0.5 m). Values of average gradients indicated high dynamics of DO and pH concentration changes as well as low chlorophyll-a variability. A slight inclination of the final resultant vector gradients of DO and pH from the surface water inlet, deepest point of the lake basin and the place of water outlet transect indicated the dominant role of confluence in these parameters variability (values amounted to 6.08 mg·km−1 and 3.34 pH units·km−1, respectively). The value of the chlorophyll-a gradient vector (1.86 µg·km−1) indicated a slight differentiation of the parameter in the basin, independent of the hydrological conditions. The concentration of chl-a in the polymictic Lake Bikcze resulted from the effect of the limnic conditions; the flowability of the lake was just one of many factors affecting the variability of the parameter.

Spatial and temporal variability of surface chlorophyll-a in the Gulf of Tomini, Sulawesi, Indonesia

Sari QW, Siswanto E, Setiabudidaya D, Yustian I, Iskandar I. 2018. Spatial and temporal variability of surface chlorophyll-a in the Gulf of Tomini, Sulawesi, Indonesia. Biodiversitas 19: 793-801. The Gulf of Tomini (GoT) is mostly influenced by seasonal and interannual events. So, the immensive aim of this study is to explore spatial and temporal variations of chlorophyll-a (chl-a) and oceanographic parameters in the GoT under the influences of monsoonal winds, El Niño Southern Oscillation (ENSO), and Indian Ocean Dipole (IOD). The data were collected from the satellite imaging of chl-a and sea and surface temperature (SST) as well as surface wind from the reanalysis data for a period of January 2003 to December 2015. Monthly variations of the chl-a and SST in the GoT reveal chl-a bloom in the center part to the mouth of the GoT during the southeast monsoon season (boreal summer). The chl-a concentrations were relatively higher (>0.1 mg m-3) and distributed throughout most of the areas near the Maluku Sea. The SST in the middle of the GoT was relatively lower than that near the Maluku Sea (the eastern part of the GoT). On the other hand, during the northwest monsoon (boreal winter), the chl-a concentration decreased (<0.1 mg m-3). During this season, the SST was relatively higher (28-29 °C) than that during the boreal summer (27-26 °C) and distributed uniformly. Meanwhile, on interannual timescale, the ENSO and IOD play important role in regulating chl-a distribution in the GoT. High surface chl-a concentration was observed during El Niño and/or positive IOD events. Enhanced surface chl-a concentration during El Niño and/or positive IOD events was associated with the upward Ekman pumping induced by the southeasterly wind anomalies. The situation was reversed during the Niña and/or negative IOD events.

Landsat TM/ETM+ and machine-learning algorithms for limnological studies and algal bloom management of inland lakes

Accumulating remotely sensed and ground-measured data and improvements in data mining such as machine-learning techniques open new opportunities for monitoring and managing algal blooms over large spatial scales. The goal of this study was to test the accuracy of remotely sensed algal biomass determined with machine-learning algorithms and Landsat TM/ETM+ imagery. We used chlorophyll-a concentration data from the 2007 National Lake Assessment (NLA) (lake N = 1157) by the US Environmental Protection Agency to train and test Landsat TM/ETM+ algorithms. Results showed significant improvements in chlorophyll-a retrieval accuracy using machine-learning algorithms compared with traditional empirical models using linear regression. Specifically, the results from boosted regression trees and random forest explained, respectively, 45.8% and 44.5% of chlorophyll-a variation. Multiple linear regression could only explain 39.8% of chlorophyll-a variation. The chlorophyll-a concentration derived from Landsat TM/ETM+ and a simple to use Google Earth Engine application, accurately characterized a 2009 algal bloom in western Lake Erie to show the model worked well for the analysis of temporal changes in algal conditions. Compared with chlorophyll-a data from the NLA, chlorophyll-a measurements with our Landsat TM/ETM+ model had almost the same correlation with lake’s total phosphorus concentrations, especially when using multiple Landsat images. Therefore, Landsat measurements of chlorophyll-a have value for ecological assessments and managing algal problems in lakes.

Different responses of chlorophyll-a concentration and Sea Surface Temperature (SST) on southeasterly wind blowing in the Sunda Strait

During southeast monsoon, along the western coast of Sumatra Island and southern coast of Java Island are known as the coastal upwelling areas denoted by the occurrence of Sea Surface Temperature (SST) cooling and chlorophyll-a blooming. Located between Sumatra and Java Islands, Sunda Strait waters may give different response to the southeasterly wind blowing above. Using SST and chlorophyll-a data obtained from daily MODIS level 3 during 2006–2016, this study demonstrated the evidence on how bathymetry and topography modified the effect of southeasterly wind on the spatial variability of SST and chlorophyll-a. All datasets were composed into monthly and monthly climatology. The area in the center of Sunda Strait had the lowest chlorophyll-a concentration and the warmest SST during the peak of upwelling season. The deep bottom topography and the absence of barrier land prevented the generation of wind driven coastal upwelling. However, the chlorophyll-a concentration in this area had the highest correlation with the wind speed which means that the variation of chlorophyll-a concentration in this area was highly depended on the variability of wind. On the other hand, the areas with shallow bathymetry and in front of Panaitan and Java Islands had higher chlorophyll-a concentration and cooler SSTs.

Effect of ENSO on the variability of SST and Chlorophyll-a in Java Sea

Sea surface temperature (SST) and chlorophyll-a (Chl-a) are two parameters often used for identifying the marine productivity. Located at the maritime continent, the variability of SST and Chl-a in the Indonesian seas is influenced by El Niño Southern Oscillation (ENSO). The previous studies showed that the effect of El Niño tend to decrease SST and increase Chl-a in the areas within the Indonesian seas. Using long time observation of satellite data (2003-2016), it was found different result in Java Sea. Since Java Sea has strong seasonal variability influenced by monsoon wind, the effect of ENSO depend on the season. During southeast monsoon season, El Niño (La Niña) tend to increase (decrease) the speed of southeasterly wind cause the decrease or increase of SST. On the contrary, during northwest monsoon season, El Niño (La Niña) tend to decrease (increase) the speed of northwesterly wind cause the increase (decrease) of SST. The dependence of Chl-a on wind speed is only observed in the off shore which exhibit the strong seasonal variation. However, the effect of ENSO on the variability of Chl-a is not robust since the effected amplitude is less than the RMSE of Chl-a data.

Investigating the chlorophyll-a variability in the Gulf of Taranto (North-western Ionian Sea) by a multi-temporal analysis of MODIS-Aqua Level 3/Level 2 data

The analysis of chlorophyll-a (chl-a) variability on a long-term basis could allow detecting possible issues in the whole marine ecosystem functioning. The Gulf of Taranto (Southern Italy), in the North-western Ionian Sea (Mediterranean Sea), has been affected by several environmental threats in the last decade, thus deserving the implementation of an adequate monitoring system able to provide accurate indications about the variability of the most relevant bio-optical parameters.In this context, the main objectives of this study are to investigate the long-term chl-a variability in the Gulf of Taranto and identify the occurrence of any past spatiotemporal anomalies by implementing the multi-temporal Robust Satellite Technique (RST) on a 12-year (2003–2015) period of MODIS/AQUA Level 3/Level 2 chlorophyll-a data. The achieved results show well-clustered near-surface positive chl-a anomalies during the January–February 2011 period. This detected offshore phytoplankton bloom may be related to sub-basin processes, such as the inflow of the Western Adriatic Coastal Current (WACC), probably fostered by the cyclonic reversal of the Bimodal Oscillating System (BiOS) mechanism. Therefore, the RST approach proved successful in detecting chl-a anomalous variations with a high level of confidence regardless of the absolute value measured, thus suggesting its exportability in other areas with different site-setting conditions.