Evaluation of Satellite Retrievals of Chlorophyll-a in the Arabian Gulf

Al-Naimi, Noora; Raitsos, Dionysios Ε.; Ben-Hamadou, Radhouan; Soliman, Yousria

doi:10.3390/rs9030301

Cited by 52 publications

(33 citation statements)

References 40 publications

(52 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first optical depth, Z90, is the penetration depth of light (e.g., Al-Naimi et al, 2017;Cherkasheva et al, 2013;Gordon & Morel, 1983). It represents how deep the satellite signal penetrates in the water column (e.g., Al-Naimi et al, 2017). To calculate this over the study area, the diffuse attenuation coefficient (Kd(490)) was estimated.…”

Section: Calculation Of the First Optical Depthmentioning

confidence: 99%

Shelf‐Break Upwelling and Productivity Over the North Kenya Banks: The Importance of Large‐Scale Ocean Dynamics

et al. 2020

View full text Add to dashboard Cite

The North Kenya Banks (NKBs) have recently emerged as a new frontier for food security and could become an economically important fishery for Kenya with improved resources providing better accessibility. Little research has been done on the mechanisms supporting high fish productivity over the NKBs with information on annual and interannual environmental variability lacking. Here we use a high-resolution, global, biogeochemical ocean model with remote sensing observations to demonstrate that the ocean circulation exerts an important control on the productivity over the NKBs. During the Northeast Monsoon, which occurs from December to February, upwelling occurs along the Kenyan coast, which is topographically enhanced over the NKBs. Additionally, enhanced upwelling events, associated with widespread cool temperatures, elevated chlorophyll, nutrients, primary production, and phytoplankton biomass, can occur over this region. Eight such modeled events, characterized by primary production exceeding 1.3 g C/m −2 /day, were found to occur during January or February from 1993-2015. Even though the upwelling is always rooted to the NKBs, the position, spatial extent, and intensity of the upwelling exhibit considerable interannual variability. The confluence zone between the Somali Current and East African Coastal Current (referred to as the Somali-Zanzibar Confluence Zone) forms during the Northeast Monsoon and is highly variable. We present evidence that when the Somali-Zanzibar Confluence Zone is positioned further south, it acts to enhance shelf-edge upwelling and productivity over the NKBs. These findings provide the first indication of the environmental controls that need to be considered when developing plans for the sustainable exploitation of the NKB fishery. Plain Language SummaryThe North Kenya Banks (NKBs) have recently emerged as a region capable of sustaining a rich fishery, which would boost Kenya's economy. Little research has been conducted on the environmental controls that affect these fisheries and whether there is annual variability over multiple years. Here an ocean model is used, with satellite remote sensing data, to investigate how the ocean influences this region. Specifically, the convergence of two currents during the Northeast Monsoon, the Somali Current and the East African Coastal Current, which meet near the NKBs and flow away from the coast. This induces the upwelling of cold, nutrient-rich waters, which are brought up from depth to the surface, resulting in the NKBs being a highly productive area. The confluence of these two currents forms from December to February and its position along the Kenyan coast varies from year-to-year. This leads to considerable variability in the intensity, position, and spatial extent of productive waters. Productivity is enhanced over the NKBs when the confluence of the two currents is generally positioned further south. These findings provide the first indication of the environmental controls that need to be taken into account when developing plans for sust...

show abstract

Section: Calculation Of the First Optical Depthmentioning

confidence: 99%

Shelf‐Break Upwelling and Productivity Over the North Kenya Banks: The Importance of Large‐Scale Ocean Dynamics

et al. 2020

View full text Add to dashboard Cite

show abstract

“…It is now one of the most effective means to acquire spatially and temporally cohesive daily information on global waters. The cost effective accessibility and long-term availability have made it a vital and practical tool in aquatic studies (Brando & Dekker, 2003;Hu et al, 2004;Platt et al, 2009;Matthews et al, 2010;Zhang et al, 2015;Alikas & Kratzer, 2017), including retrieving phytoplankton pigments (Kutser, 2004;Simis et al, 2005;Gitelson et al, 2009;Moses et al, 2009;Al-Naimi et al, 2017), estimating Coloured Dissolved Organic Matter (CDOM) (Dall'Olmo et al, 2017) and Total Suspended Solids (TSS) (Chen et al, 2007a,b). To detect and map phytoplankton blooms in optically complex inland and coastal waters, ocean colour indices have been demonstrated as one promising approach (Gower et al, 2005(Gower et al, , 2006Hu, 2009;Hu et al, 2010;Matthews et al, 2012;Matthews, 2014;Palmer et al, 2015;Hu & Feng, 2017).…”

Section: Introductionmentioning

confidence: 99%

MERIS observations of phytoplankton phenology in the Baltic Sea

Zhang

Lavender

Müller

et al. 2018

Science of The Total Environment

View full text Add to dashboard Cite

The historical data from the MEdium Resolution Imaging Spectrometer (MERIS) is an invaluable archive for studying global waters from inland lakes to open oceans. Although the MERIS sensor ceased to operate in April 2012, the data capacities are now re-established through the recently launched Sentinel-3 Ocean and Land Colour Instrument (OLCI). The development of a consistent time series for investigating phytoplankton phenology features is crucial if the potential of MERIS and OLCI data is to be fully exploited for inland water monitoring. This study presents a time series of phytoplankton abundance and bloom spatial extent for the highly eutrophic inland water of the Baltic Sea using the 10-year MERIS archive (2002-2011) and a chlorophyll-a based Summed Positive Peaks (SPP) algorithm. A gradient approach in conjunction with the histogram analysis was used to determine a global threshold from the entire collection of SPP images for identifying phytoplankton blooms. This allows spatio-temporal dynamics of daily bloom coverage, timing, phytoplankton abundance and spatial extent to be investigated for each Baltic basin. Furthermore, a number of meteorological and hydrological variables, including spring excess phosphate, summer sea surface temperature and photosynthetically active radiation, were explored using boosted regression trees and generalised additive models to understand the ecological response of phytoplankton assemblages to environmental perturbations and potential predictor variables of summer blooms. The results indicate that the surface layer excess phosphate available in February and March had paramount importance over all other variables considered in governing summer bloom abundance in the major Baltic basins. This finding allows new insights into the development of early warning systems for summer phytoplankton blooms in the Baltic Sea and elsewhere.

show abstract

“…It provides synoptic views, with spatially and temporally cohesive coverage of global waters from open oceans to inland lakes at a near daily frequency. Chlorophyll-a (Chl-a), acting as the primary photosynthetic pigment of phytoplankton, has been widely used as a proxy to indicate phytoplankton abundances (Vos et al, 2003;Gons et al, 2008;Ruiz-Verdu et al, 2008;Nair et al, 2008;Moses et al, 2009;Brewin et al, 2013;Al-Naimi et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Determination of phytoplankton abundances (Chlorophyll- a ) in the optically complex inland water - The Baltic Sea

Zhang

Lavender

Müller

et al. 2017

Science of The Total Environment

View full text Add to dashboard Cite

A novel approach, termed Summed Positive Peaks (SPP), is proposed for determining phytoplankton abundances (Chlorophyll-a or Chl-a) and surface phytoplankton bloom extent in the optically complex Baltic Sea. The SPP approach is established on the basis of a baseline subtraction method using Rayleigh corrected top-of-atmosphere data from the Medium Resolution Imaging Spectrometer (MERIS) measurements. It calculates the reflectance differences between phytoplankton related signals observed in the MERIS red and near infrared (NIR) bands, such as sun-induced chlorophyll fluorescence (SICF) and the backscattering at 709nm, and considers the summation of the positive line heights for estimating Chl-a concentrations. The SPP algorithm is calibrated against near coincident in situ data collected from three types of phytoplankton dominant waters encountered in the Baltic Sea during 2010 (N=379). The validation results show that the algorithm is capable of retrieving Chl-a concentrations ranging from 0.5 to 3mgm, with an RMSE of 0.24mgm (R=0.69, N=264). Additionally, the comparison results with several Chl-a algorithms demonstrates the robustness of the SPP approach and its sensitivity to low to medium biomass waters. Based on the red and NIR reflectance features, a flagging method is also proposed to distinguish intensive surface phytoplankton blooms from the background water.

show abstract

Evaluation of Satellite Retrievals of Chlorophyll-a in the Arabian Gulf

Cited by 52 publications

References 40 publications

Shelf‐Break Upwelling and Productivity Over the North Kenya Banks: The Importance of Large‐Scale Ocean Dynamics

Shelf‐Break Upwelling and Productivity Over the North Kenya Banks: The Importance of Large‐Scale Ocean Dynamics

MERIS observations of phytoplankton phenology in the Baltic Sea

Determination of phytoplankton abundances (Chlorophyll- a ) in the optically complex inland water - The Baltic Sea

Contact Info

Product

Resources

About