## 3 Results
### TCs Impacts: Emily, Stan, Wilma, and Dean
#### 3.2.4 Coastal Chl-\(a\) Concentrations  
Our analysis focused on seven days before and after TC landfall to determine spatial patterns associated with each TC trajectory, motion, and exit location (Figures 10 and 11). Chl-\(a\) concentrations before landfall ranged between 0.5 and 2 mg/m\({}^{3}\); these values decrease from the YP coastline towards the continental shelf, which is characterized by a smooth seafloor slope [93]. Except for the Chl-\(a\) distribution after Dean, concentrations increased above 10 mg/m\({}^{3}\) in coastal areas after TC landfall, including Chetumal Bay, Cabo Catoche, Terminos Lagoon, and offshore in the central and northern Campeche coast (Figure 1B, Figure 10A). Figure 9: Enhanced Vegetation Index (EVI) profiles along the Yucatan Peninsula portion of selected tropical cyclones (TCs) tracks: **(A)** Emily, **(B)** Stan, **(C)** Wilma, and **(D)** Dean; TCs trajectory and direction are shown in Figure 7. Blue is before and red after landfall; the zero value in the X-axis is the landfall location; notice the difference in the X-value range per storm. The index difference between the value after and before landfall is in black (EVI change; right Y-axis). A negative difference means that the index is lower after landfall. Within the week following TC passage, there were spatial differences in the Chl-_a_ distribution off the northern and western YP coastlines (Figure 10A). Areas represented by concentrations above 0.5 mg/m\({}^{3}\)increased in all cases from a baseline value before the storm impact of 42% after Dean's passage followed by 28% in Emily and 20% in Wilma. A larger increase (67%) from the baseline value was associated with Stan (Figure 10A) along the Campeche coastal region. Most of the Chl-_a_ enhancements were within 50 km from the YP, with a maximum extension up to 100 km northwest from Cabo Catoche (Figure 1B). To evaluate the spatial changes of Chl-_a_, along the YP coastline, a transect was established along the 25-m isobath off the YP coastline (see Section 2.3; Figure 10A, dotted line) before and after each TC passage (Figure 11). While the Yucatan and Quintana Roo transect segments show a relative increase in Chl-_a_ after the passage of Stan (138%), the increase was lower after Dean (26%) and Emily (24%). The maximum value along the transect after Stan's passage was 5 mg/m\({}^{3}\) and was located 120 km north of Terminos Lagoon (Figure 1), indicating the regional-scale impact of this TC over the southern (left) side of its center track. In contrast, Wilma crossed a limited portion of the YP, and the TC was more distant from the southern GOM; therefore, with some exceptions, there were no net changes in the Chl-_a_ concentration along the transect (Figure 11). Figure 10: (**A**) Chl-_a_ (mg/m\({}^{3}\); averaged seven days before and after landfall) in the Caribbean Sea, Gulf of Mexico, and coastal regions of the Yucatan Peninsula. The area (km\({}^{2}\)) covered by pixels with a concentration above 0.5 mg/m\({}^{3}\) is shown on the panel right corner before and after landfall; the dotted line off the peninsula on the left panel is the transect (T1) discussed in the text (see Figure 11). Tropical cyclone tracks (lines and dots) are at 6-h intervals; concentrations are seven days before (left column) and after (right column) landfall. (**B**) Net Chl-_a_ differences (i.e., before minus after storm passage) for areas (km\({}^{2}\)) above (red tones) and below (blue tones) 0.5 mg/m\({}^{3}\) concentrations. The plus sign indicates the location of the Champion River gauge. In addition to the observed increase in Chl-_a_ along the marine transect to evaluate the effect of TC trajectory and landing position in the GOM (Figure 11), we also observed an increase in concentrations higher than the average Chl-_a_ (\(\sim\)0.5 mg/m\({}^{3}\); [39]) in adjacent coastal and ocean water bounded within the 18\({}^{\circ}\) N, 24\({}^{\circ}\) N, 85\({}^{\circ}\) W, and 93\({}^{\circ}\) W coordinates (Figure 10B).