Chlorophyll a Concentration Distribution on the Mainland Coast of the Gulf of California, Mexico

Abstract

Coastal zones are important areas for the development of diverse ecosystems. The analysis of chlorophyll a (Chl a), as an indicator of primary production in these regions, is crucial for the quantification of phytoplankton biomass, which is considered the main food chain base in the oceans and an indicator of the trophic state index. This variable is greatly important for the analysis of the oceanographic variability, and it is crucial for determining the tendencies of change in these areas with the objective of determining the effects on the ecosystem and the population dynamics of marine resources. In this study, we analysed the Chl a concentration distribution on the mainland coast of the Gulf of California based on the monthly data from July 2002 to July 2019, obtained from remote sensing (Moderate-Resolution Imaging Spectroradiometer Aqua (MODIS-Aqua) with a 9 km resolution). The results showed a clear distribution pattern of Chl a observed along this area with the maximum levels in March and minimum levels in August. A four-region characterisation on this area was used to make a comparison of the Chl a concentrations during warm and cold periods. The majority of the results were statistically significant. The spectral analysis in each of the four regions analysed in this study determined the following variation frequencies: annual, semi-annual, seasonal, and inter-annual; the last was related to the macroscale climatological phenomena El Niño-La Niña affecting the variability of the Chl a concentration in the study region.

Variability of Net Primary Productivity and Associated Biophysical Drivers in Bahía de La Paz (Mexico)

“…Zooplankton biomass ranged from 50 to 1000 mL, and values between 100 and 450 mL were more frequent, with averages between 146-829 mL from winter to spring, with maximum values observed in February, May, and June (556, 829, and 553 mL, respectively) [21,60]. In summer, even when biomass decreased (<200 mL), increases of around 300 mL were observed in July [21,60], and similar values inside and outside a cyclonic vortex (500 mL) were observed in Cuenca Alfonso, while decreases in biomass (130 mL) were observed in the southern portion of the bay in June [57]. Increased zooplankton biomass during the warm season and subsequent grazing may have decreased phytoplankton biomass in BLP [61].…”

“…The time series of NPP and SST anomalies showed annual and inter-annual variation, which has been related to coastal upwelling processes in the GC [57]. In the BLP, these have been associated with local processes related to diurnal winds, breezes, and bathymetric effects [30].…”

“…Some of the processes that bring nutrients to the euphotic zone in BLP are the coastal divergences caused by the circulation around Boca Grande [26], wind mixing [29], and the contributions of anthropogenic wastewater in the southern portion of the Ensenada de La Paz lagoon [57]. The highest concentration of nitrate (NO 3 ) at the surface (Table 1) was related to the winter-spring period, which was in turn related to positive WSC values.…”

“…Other authors using satellite-estimated Chl-a data have found similar results to those in this study, which is perhaps because only the University of Oregon [43] currently provides satellite NPP information. For example, Robles-Tamayo [57] used spectral analysis and determined that the annual, semi-annual, seasonal, and inter-annual frequencies affect the variability of the Chl-a concentration in the GC. For BLP, significant relationships between environmental factors and chlorophyll satellite data have been found using exponential models, with steep slopes and high correlations observed during La Niña events [68].…”

Application of Generalized Cauchy Process on Modeling the Long-Range Dependence and Self-Similarity of Sea Surface Chlorophyll Using 23 years of Remote Sensing Data

“…This phenomenon leads to the empirical values of ACF (blue dash line shown in Figure 4) being slightly higher than the theoretical values of ACF (black line shown in Figure 4) with the temporal lags between 2 and 10 days at most locations. However, with the temporal lag increasing from 10 to 25 days, the empirical values become smaller than the theoretical values, because the SSC may be influenced by the global climatic dynamics, such as the Southern Pacific Oscillation Index [49], which is different from algae's own growth condition. Moreover, there may be another situation that algae blooms with enough nutrient inputs [50], leading to extremely high SSC values, e.g., the SSC value increases rapidly and peaks for one or 2 days (as some peaks shown in Figure 3); and that may be the reason that the value of the fractal dimension is the highest among the 10 series, i.e., D 1.7964 with the highest maximum SSC value and standard deviation across the study period.…”