Modeling the Habitat Distribution of Acanthopagrus schlegelii in the Coastal Waters of the Eastern Taiwan Strait Using MAXENT with Fishery and Remote Sensing Data

Black sea bream, Acanthopagrus schlegelii, is among the most commercially valuable species in the coastal fishery industry and marine ecosystems. Catch data comprising capture locations for the gillnet fisheries, remotely sensed environmental data (i.e., sea surface temperature, chlorophyll-a concentration, and current velocity), and topography (bathymetry) from 2015 to 2018 were used to construct a spatial habitat distribution of black sea bream. This species is concentrated in coastal waters (<3 nm) from December to April (spawning season). The maximum entropy (MaxEnt) method and corresponding habitat suitability index among seasons were used to clarify the species’ spatial distribution and identify the seasonal variations in habitat selection. The patterns corresponded closely to the changes in oceanographic conditions, and the species exhibited synchronous trends with the marine environment’s seasonal dynamics. Chlorophyll-a concentration and bathymetry substantially influenced (80.1–92.9%) black sea bream’s habitat selection. By applying the MaxEnt model, the optimal habitats were identified with four variables including depth and satellite-derived temperature, current velocity and chlorophyll-a concentration, which provides a foundation for the scientific assessment and management of black sea bream in coastal waters of the Eastern Taiwan Strait.

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Bio-Optical Characteristics of the Black Sea Coastal Waters near Sevastopol: Assessment of the MODIS and VIIRS Products Accuracy

Morskoy gidrofizicheskiy zhurnal ◽

10.22449/0233-7584-2021-2-233-246 ◽

2021 ◽

Vol 37 (2) ◽

Author(s):

E. Yu. Skorokhod ◽

T. Ya. Churilova ◽

T. V. Efimova ◽

N. A. Moiseeva ◽

V. V. Suslin ◽

...

Keyword(s):

Chlorophyll A ◽

Black Sea ◽

Coastal Waters ◽

Light Absorption ◽

Ecological Monitoring ◽

Optically Active ◽

The Black Sea ◽

Active Components ◽

Chlorophyll A Concentration

Purpose. The purpose of the work is to evaluate accuracy of the satellite products for the coastal waters near Sevastopol, reconstructed by the standard algorithms based on the MODIS and VIIRS (installed at the artificial Earth satellites Aqua and Terra, and at Suomi NPP, respectively) data. Methods and Results. In situ sampling was carried out at the station (44°37'26" N and 33°26'05" E) located at a distance of two miles from the Sevastopol Bay. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients by optically active components were measured in accordance with the current NASA protocol. The spectroradiometers MODIS and VIIRS Level 2 data with spatial resolution 1 km in nadir around the in situ station (44°37'26"±0°00'32" N and 33°26'05"±0°00'54" E) were used. The satellite products were processed by the SeaDAS 7.5.3 software developed in NASA. The research showed that the standard NASA algorithms being applied to the MODIS and VIIRS data, yielded incorrect values of the optically active components’ content in the Black Sea coastal waters near Sevastopol as compared to the data of in situ measurements in the same region: the satellite-derived “chlorophyll a concentration” was on average 1.6 times lower in spring, and 1.4 times higher in summer; the contribution of phytoplankton pigments to total light absorption at 443 nm was underestimated in 8.7 times; the light absorption by colored detrital organic matter was overestimated in 2.2 times. Conclusions. The NASA standard algorithms are inapplicable to calculating bio-optical indices in the coastal waters of the Black Sea near Sevastopol since they provide incorrect values of the satellite products (Ca-s, aph-s(443) and aCDM-s(443)). Operative ecological monitoring based on satellite data requires development of a regional algorithm taking into account the seawater optical features in the region and in the coastal zone, in particular.

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Comparison of chlorophyll a concentration values retrieved from MODIS-Aqua spectroradiometer with the results of measurements in the coastal waters of the Black Sea near Sevastopol

Marine Biological Journal ◽

10.21072/mbj.2019.04.4.05 ◽

2019 ◽

Vol 4 (4) ◽

pp. 53-61

Author(s):

E. Yu. Skorokhod ◽

T. V. Efimova ◽

N. A. Moiseeva ◽

E. A. Zemlianskaia ◽

T. Ya. Churilova

Keyword(s):

Chlorophyll A ◽

Black Sea ◽

Coastal Waters ◽

Field Measurements ◽

The Black Sea ◽

Optical Monitoring ◽

Chlorophyll A Concentration ◽

Low Concentrations ◽

Satellite Product ◽

Significant Underestimation

The results of the comparison of the values of the standard satellite product “Chlorophyll a Concentration” recovered from MODIS-Aqua satellite with the results of field measurements in the coastal waters of the Black Sea near Sevastopol from 2009 to 2019 as a part of regular bio-optical monitoring have been presented. Differences between seasons in the nature of the error of the standard satellite product “Chlorophyll a Concentration” using the standard NASA algorithm were established: in spring, a significant underestimation of the values of the standard satellite product “Chlorophyll a Concentration” (up to 2.1 times) at high chlorophyll a concentrations was noted according to the results of the full-scale measurements, and in summer a significant overestimation of the values (up to 3.8 times) at low concentrations was noted. Throughout the year, depending on the season, the error in determining the standard satellite product “Chlorophyll a Concentration” on average varied from ±24 % to ±51 %. To increase the accuracy of determining the chlorophyll a concentration with remote sensing, it is necessary to use a regional approach.

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Bio-Optical Characteristics of the Black Sea Coastal Waters near Sevastopol: Assessment of the MODIS and VIIRS Products Accuracy

Physical Oceanography ◽

10.22449/1573-160x-2021-2-215-227 ◽

2021 ◽

Vol 28 (2) ◽

Author(s):

E. Yu. Skorokhod ◽

T. Ya. Churilova ◽

T. V. Efimova ◽

N. A. Moiseeva ◽

V. V. Suslin ◽

...

Keyword(s):

Chlorophyll A ◽

Black Sea ◽

Coastal Waters ◽

Light Absorption ◽

Ecological Monitoring ◽

Optically Active ◽

The Black Sea ◽

Active Components ◽

Chlorophyll A Concentration

Purpose. The purpose of the work is to evaluate accuracy of the satellite products for the coastal waters near Sevastopol, generated by the standard algorithms based on the MODIS and VIIRS (installed at the artificial Earth satellites Aqua and Terra, and at Suomi NPP, respectively) data. Methods and Results. In situ sampling was carried out at the station (44°37’26" N and 33°26’05" E) located at a distance of two miles from the Sevastopol Bay. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients by optically active components were measured in accordance with the current NASA protocol. The spectroradiometers MODIS and VIIRS Level-2 data with spatial resolution 1 km in nadir around the in situ station (44°37’26"±0°00’32" N and 33°26’05"±0°00’54" E) were used. The satellite products were processed by the SeaDAS 7.5.3 software developed in NASA. The research showed that the standard NASA algorithms being applied to the MODIS and VIIRS data, yielded incorrect values of the optically active components’ content in the Black Sea coastal waters near Sevastopol as compared to the data of in situ measurements in the same region: the satellite-derived “chlorophyll a concentration” was on average 1.6 times lower in spring, and 1.4 times higher in summer; the contribution of phytoplankton to total light absorption at 443 nm was underestimated in 8.7 times; the light absorption by colored detrital matter was overestimated in 2.2 times. Conclusions. The NASA standard algorithms are inapplicable to calculating bio-optical indices in the coastal waters of the Black Sea near Sevastopol since they provide incorrect values of the satellite products (Ca-s, aph-s(443) and aCDM-s(443)). Operative ecological monitoring based on satellite data requires development of a regional algorithm taking into account the seawater optical features in the region and in the coastal zone, in particular.

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Development of phytoplankton in the winter-spring period in the coastal waters of Crimea

Marine Biological Journal ◽

10.21072/mbj.2021.06.1.08 ◽

2021 ◽

Vol 6 (1) ◽

pp. 102-114

Author(s):

Z. Z. Finenko ◽

I. M. Mansurova ◽

I. V. Kovalyova ◽

E. Yu. Georgieva

Keyword(s):

Growth Rate ◽

Specific Growth Rate ◽

Chlorophyll A ◽

Black Sea ◽

Coastal Waters ◽

Specific Growth ◽

Shelf Zone ◽

The Black Sea ◽

Chlorophyll A Concentration ◽

Spring Period

The analysis of phytoplankton in the winter-spring period is important for investigating peculiarities of its annual dynamics and the Black Sea ecosystem overall functioning. Phytoplankton state in the winter-spring period in the Black Sea shelf zone is less studied than that of the summer-autumn season; conducting such a research is especially important for solving several problems, related to the productivity of the last links of the food chain, the formation of water hydrochemical regime, and the carbon cycle in the sea. The aim of the work is to assess the effect of seasonal conditions on the development of phytoplankton and its production estimates in the winter-spring period in the coastal waters of Crimea. The article presents the results of studies of hydrophysical (water temperature, density, and relative transparency) and biological indicators (chlorophyll a concentration, its fluorescence, taxonomic composition, and phytoplankton production estimates) in the Black Sea shelf zone in January – April 2016–2019. The studies were carried out at 50 stations, located in the coastal waters of Crimea from the Karkinitsky Bay to the Kerch Strait. Chlorophyll a concentration was measured by the standard fluorometric method, species composition was determined by microscopy, and phytoplankton specific growth rate was calculated according to the previously developed model. In winter (January – February), the values of chlorophyll a content and upper mixed layer depth were the highest (0.42–0.52 mg·m−3 and 44–58 m, respectively); in spring (March – April) they were 2–3 times lower. In January – February, the coccolithophore species Emiliania huxleyi (Lohmann) W. W. Hay & H. P. Mohler, 1967 predominated; in March – April, in different years, either dinoflagellates and diatoms or coccolithophores, dinoflagellates, and diatoms prevailed. In winter, chlorophyll a vertical distribution at most stations was uniform; in spring, unimodal profiles with a depth maximum prevailed, the location of which was not related to temperature and density gradients. Relative changes in chlorophyll a concentration and fluorescence with depth were usually the same. Phytoplankton production and daily production/biomass ratio (P/B) increased from winter to spring. There was no correlation between the values of integral production, biomass, and maximum specific growth rate of algae. Maximum specific growth rate was the least variable indicator. During the winter-spring period, algae in the photosynthetic zone divided on average once every 2–5 days.

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