Ortiz Rosa, Suhey

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    Bio-optical and biogeochemical characterization of “Dark Water” events in southwestern Puerto Rico
    (2023-12-08) Ortiz Rosa, Suhey; Armstrong Pacheco, Roy A.; College of Arts and Sciences - Sciences; Hernández López, William J.; Weil Machado, Ernesto F.; Williams, Stacey M.; Department of Marine Sciences; Román Pérez, Rosa I.
    This dissertation characterized and traced black water events (BWE) in southwestern Puerto Rico (PR) coastal and offshore waters. This study provides a dataset to validate ocean color data and to derive empirical algorithms for the Caribbean region. In addition, it contributed to the understanding of light attenuation in surface waters. Furthermore, two of the chapters demonstrated the feasibility of remote sensing data for water quality assessments using two different satellite sensors in Puerto Rican coastal waters. Black water events (BWE) are common in coastal areas associated with wetlands or river outfalls, rich in organic humic matter. In Puerto Rico, BWE can be found along the insular shelf and in oligotrophic waters. In chapter two we integrated in-situ and satellite data for BWE characterization through reflectance band ratios to develop a dark water index. BWE were identified in 8 Sentinel-3A (S3A) images in 2018. A dark water index combining bands (B1+B2)/B6 was used to distinguish these events from the surrounding clear, oligotrophic waters. Our results suggest that an index of less than 7 defines BWE. The S3A absorption of colored dissolved organic matter at 443 nm (ADG443_NN) product values inside the BWE are 15.1 % higher than the values of adjacent clear waters. We suggest that the highest contribution to the BWE optical signal is Colored Dissolved Organic Matter (CDOM), but it is also highly influenced by chlorophyll. The occurrence of BWE around the island appears to be frequent. Follow-up studies are needed to monitor prolonged BWE and examine their impact on coral reefs and associated ecosystems. Chapters three and four assessed the impact of Hurricanes Irma and María (2017) using ocean color data. These studies combined field and satellite data to determine hurricane impacts in water quality using absorption of CDOM (aCDOM) /ADG, Chlorophyll-a, total suspended matter (TSM) and attenuation coefficient (Kd490) parameters as indicators. We determined anomalies in water quality parameters using existing ocean color products from Sentinel 3A at La Parguera Nature Reserve (LPNR) and evaluated the Chlorophyll-a and Kd490 products with the Visible Infrared Imaging Radiometer Suite (VIIRS) data around Puerto Rico.
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    Optical properties and photochemical response of colored dissolved organic matter (cdom) at Jobos Bay National Estuarine Research Reserve (JOBANERR), Puerto Rico
    (2010-12) Ortiz Rosa, Suhey; Corredor García, Jorge E.; College of Arts and Sciences - Sciences; Morell Rodríguez, Julio M.; López Díaz, José M.; Aponte Avellanet, Nilda E.; Department of Marine Sciences; Grove, Kurt A.
    The study evaluated the optical properties and dynamics of CDOM in JOBANERR. CDOM absorption coefficient spectrum (aCDOM), Slope (S), excitation emission matrix (EEM) fluorescence and Parallel Factor Analysis (PARAFAC) were used to characterize sources of CDOM. S values varied from 0.014–0.034 nm-1 and aCDOM ranged from 0.11m-1 to 11 m-1. Mar Negro presented a strong terrestrial source of CDOM while Mar Blanco is a transitional area combining terrestrial and marine CDOM sources. Barca presented a strong marine source and it is influenced by terrestrial sources in wet months. Spatial differences were observed between mangrove semi-enclosed areas and open areas of the bay. Significant differences were found on DOC, salinity and slope parameters seasonally between the study sites. Dissolved Organic Carbon (DOC), aCDOM and fluorescence intensity of the main fluorophores (C, M, A, H) were related to salinity, chlorophyll, and UV dose. DOC and aCDOM presented a low correlation (R2 = 0.16). UV dose correlated with aCDOM (Pearson coefficient = -0.98) in an exponential decay. Chlorophyll correlated with aCDOM (Pearson coefficient = 0.73). PARAFAC showed seven components in samples exposed to sunlight described as humic-like, protein-like, degradation or microbial substances. Two principal processes transform CDOM: photodegradation and dilution. The high variability of CDOM signatures in Jobos waters are explained by chemical transformations of CDOM.