Jorge E Corredor

Marine sediment samples and interstitial water from five stations at the southwest of PuertoRico with different characteristics in composition, were submitted to acetylene reduction technique for nitrogen fixation quantification and ammonium analysis respectively. All stations showed positive results. Glucose addition to the samples increased nitrogen fixation in a proportion of 50 to 200. Organic matter per cent correlated to both: nitrogen fixation and ammonium concentration, indicated a direct proporcionality. In addition nitrogen fixation correlated to the ammonium concentration per station, showed that nitrogen fixation could be limited by the ammonium ion presence in those benthic systems.

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, alt...

Inorganic N enrichment of near-surface waters and phytoplankton biomass increase denote the occurrence of 'island mass effects' in the wakes of Sombrero and St. Croix. Ammonia is the most prevalent inorganic species of available N in the island wakes but is present only in low concentrations. Nitrate, although prevalent in deeper waters, is rarely found in near-surface waters. An instance is documented of nitrate enrichment associated with an isopycnal displacement of close to 30 m. No evidence is, however, available for the mixing of water masses necessary to provide lasting enrichment of the near-surface waters. Biomass of phytoplankton is significantly greater in the wakes of these oceanic islands than in offshore waters. -from Authors

Direct analysis of Ca+2 and Mg+2 is required for accurate determination of meta-stable carbonate mineral phase saturation states (Ω CaCO3; Ω MgCO3) in seawater, sediment pore-waters and other high ionic strength brines. To this end we have implemented a method using High Performance Liquid Chelation Ion Chromatography (HPLCIC) in which metal ion complexation at the stationary phase renders separation efficiency insensitive to high ionic strength matrix effects common to other ion chromatography methods. This method, using direct automated on-column injection, vastly increases sample throughput capacity in comparison to current titration methods. Calcium and magnesium ions in IAPSO standard seawater were selectively separated using a monolithic silica column (100 x 4.6 mm I.D.) activated with a covalently bonded iminodiacetic acid (IDA) chelator. The colored ion chelates resulting from post-column reaction of the ions with a second chelator, in this case 4-(2-pyridylazo)-resorcinol (...

Orinoco River influence in the Caribbean Sea, characterized by high nutrient input, causes a decrease of Trichodesmium populations. The Caribbean Time Series (CaTS) station, south of Puerto Rico (17 degrees 36'N 67 degrees 00'W), was monitored for 25 months in order to observe the Trichodesmium abundance pattern and the presence of the river plume. In general, mean Trichodesmium abundance was higher at the surface and decreased with depth. The mean upper water column (surface to 20 m) abundance was 54.1 +/- 32.6 col/m3. Within the sampling period, abundance was highly variable (1-700 col/m3). Correlation between Trichodesmium abundance and wind speed (p=0.002), chlorophyll a concentration (p=0.001), nitrate (p=0.02) and silicate (p=0.003) concentrations were statistically significant. However, Trichodesmium abundance was not correlated with salinity (p=0.70), temperature (p=0.16) and seawater density (p=0.71) variations at CaTS. Eastern Caribbean regions highly influenced by...

Reef corals typically contain a number of pigments, mostly due to their symbiotic relationship with photosynthetic dinoflagellates. These pigments usually vary in presence and concentration and influence the spectral characteristics of corals. We studied the variations in pigment composition among seven Caribbean shallow-water Scleractinian corals by means of High Performance Liquid Chromatography (HPLC) analysis to further resolve the discrimination of corals. We found a total of 27 different pigments among the coral species, including some alteration products of the main pigments. Additionally, pigments typically found in endolithic algae were also identified. A Principal Components Analysis and a Hierarchical Cluster Analysis showed the separation of coral species based on pigment composition. All the corals were collected under the same physical environmental conditions. This suggests that pigment in the coral's symbionts might be more genetically-determined than influenced ...

This study was undertaken to quantify the emission and distribution of nitrous oxide and to explore its relation to pertinent physical and chemical parameters in a red mangrove forest located at Magueyes island, Puerto Rico. Rates of N2O evolution, which ranged from 0·05 to 1·4 μmole m-2 h-1 (overall mean=0·50 μmole m-2 h-1), are comparable to those of other previously studied ecosystems. A significant diel cycle of N2O emission was observed. Dissolved N2O concentration averaged 0·15 nmole cm-3 (SD=0·09, n=54) with a range of 0·1 to 0·57 nmole cm-3. Dissolved and exchangeable inorganic nitrogen was present mostly in the form of ammonium (overall mean=212·2 nmole cm-3) with lesser amounts of nitrate (overall mean=29·0 nmole cm-3). Redox potentials in the sediments generally decreased with depth, with a mean value of 377 mV at the sediment surfaces and lower mean value (159 mV) at 10 cm. We have explored the probable sources of N2O in the mangrove forest sediment using correlation analysis between the data obtained in this study and comparing these observations with previous studies of N2O metabolism. Our results, while not excluding the possibility of N2O production through denitrification, indicate that N2O is produced mainly by nitrification in sediments of this mangrove forest.

We examined the ultraviolet (UV) absorption spectra (280-400 nm) of coral tissue extracts and the concentration and composition of mycosporine-like amino acids (MAA) in three common Caribbean reef-building corals using UV spectroscopy and high-pressure liquid chromatography. Two of the species examined Porites astreoides (green morphotype) and Acropora cervicornis are widely distributed ranging from <1.0 to over 25 m depth, while the third, Mycetophyllia ferox, is a plating species usually confined to the deeper parts of the reef. UV absorption spectra (280-400 nm) of coral tissue extracts in seawater exhibited absorption maxima between 320 and 340 nm and protein-specific absorption in general decreased with depth. A. cervicornis and P. astreoides exhibited hypsochromic displacement in their UV-absorption spectra relative to M. ferox, denoting greater capacity per mole unit MAA for absorption of the shorter, more energetic, and thus more harmful radiation. MAA content of M. ferox...

Global warming will lead to changes in rainfall patterns over the planet. As a consequence, it will modify streamflow behaviour too. The change of runoff regime implies not only changes in mean values, but also changes in extreme values. These extreme values represent drought runoff and high peak runoff from floods. Floods are an important factor for structural design of bridges for roads/river intersections. Usually, bridges are designed for stationary hydrologic conditions, implying that the probabilities of maximum flows are constant in time. Due to the climate change process, maximum flow values that are used as critical values for structural bridge design could be underestimated for regions where an increase of precipitation is expected. Therefore, a climate change sensitivity analysis of maximum flows is necessary. This sensitivity analysis will allow an assessment of the vulnerability of hydrostructures designed under assumption of stationary hydrological conditions. This pap...

Prior studies have shown that the Mona Passage and the shelf break along the SW coast of Puerto Rico are sites of internal wave generation and these waves have been partially characterized. Joint shipboard and glider-based observations have now allowed more detailed documentation of a tidally-induced internal wave train generated in the Mona Passage between Puerto Rico and Hispaniola. Wave

MAJOR RIVER PLUMES IN THE TROPICAL OCEAN: PHYSICAL AND BIOGEOCHEMICAL EXPRESSION The Caribbean and Western Tropical Atlantic receive massive inputs of Orinoco and Amazon River water carrying a load of organic and inorganic materials into waters characteristically devoid of these. The magnitude of riverine impact became evident as remote sensing became an ocean color monitoring tool. These observations depict riverine plumes, containing dissolved organic matter and phytoplankton well above background concentrations, being advected into the oligotrophic ocean. Subsequent research revealed that riverine intrusions radically modulate trophic balance and activity through changes in plankton abundance, composition and size distribution and last but not least: availability of solar irradiance. Moreover, riverine influence responds to climate processes and oceanic mesoscale processes bringing about significant spatial and temporal variability at annual and interannual scales. We discuss obs...

ABSTRACT After five years of continued development, the Caribbean Coastal Ocean Observing System (CariCOOS) has reached a major turning point regarding the nature of its ocean observing platforms and numerical modeling efforts. During the design stage of CariCOOS, stakeholder consultations highlighted the need for operational instrumented buoy platforms to provide data on winds, waves, currents and water quality. This led to the deployment of three full data buoys off the coasts of San Juan, Ponce and the United States Virgin Islands (USVI), a directional Datawell Waverider buoy in the Mona Passage, an array of shore based High Frequency Radar antennas for surface current mapping in the Mona Passage, and a network of 13 hurricane-hardened coastal meteorological stations. In addition, a suite of numerical models of winds and waves are currently operational for the region and continuously validated with our observational assets. Although stakeholders have expressed satisfaction with the regional-scale understanding obtained with CariCOOS models and ocean observing assets, recent consultations have highlighted the need for sector focused products to be developed at smaller scales targeting selected ports, highly visited and yet often hazardous tourist beaches, marine protected areas and other locations. Efforts in the current developmental stage are aimed in this direction; our mission consists of a combination of maintaining our suite of buoys, weather stations and numerical models with the development of new observing platforms and models to satisfy the nearshore-specific needs of our stakeholders. Despite being closer to shore, however, observing and predicting the complexity of the wind, wave and current patterns in the nearshore region requires highly specialized sensors and very high resolution numerical models. Stakeholder-driven efforts focused in the nearshore region currently underway at Cari-COOS include the development of a high-resolution jetski-based bathymetric - urveying and side scan sonar system, a real-time surfzone currents and beach hazards warning system, and the implementation of a three-dimensional baroclinic circulation model for important ports and nearshore regions. In this paper we describe these and other new initiatives in detail and explain the design and development process.

ABSTRACT The influence of the Orinoco River on the primary production in eastern Caribbean waters was investigated using fast repetition rate fluorometry (FRRF) and ocean color remote sensing. FRRF-based carbon fixation rates significantly correlated with independent estimates based on the 14C uptake method (r = 0.92, n = 9). Satellite-derived estimates of primary production, using the Carbon Based Productivity Method (CbPM), moderately correlated with in situ FRRF-based measurements. These estimates varied with river plume dilution gradients, with the highest rates associated with waters under river plume influence (CbPM 631 mg C m-2 d-1 and FRRF 570 mg C m-2 d-1). A time series of satellite-derived estimates (2002-2011) revealed seasonal variations associated with river discharge and climate driven fluctuations. Regional integrated productivity of about 2.80 Tg C yr-1 was calculated based on the average spatial coverage of the Orinoco River plume over the last decade.