Coastal Waters Of Gulf Research Articles

Distribution of ascidians Phallusia nigra (Tunicata: Ascidiacea) on the north coast of the Persian Gulf, Iran

Although there are a number of marine organisms located from various parts of the world, little information exists from Iranian coastal waters regarding the distribution of ascidian species. Hence, the present study attempts to describe the presence and distribution of Phallusia nigra from the four different stations along Persian Gulf coastal waters. The current study is the first record of the ascidian P. nigra off the Larak Island, Hengam Island, Qeshm Island and Bandar-e-Lengeh along the Iranian coasts of the Persian Gulf.

Quantifying the hurricane risk to offshore wind turbines

The U.S. Department of Energy has estimated that if the United States is to generate 20% of its electricity from wind, over 50 GW will be required from shallow offshore turbines. Hurricanes are a potential risk to these turbines. Turbine tower buckling has been observed in typhoons, but no offshore wind turbines have yet been built in the United States. We present a probabilistic model to estimate the number of turbines that would be destroyed by hurricanes in an offshore wind farm. We apply this model to estimate the risk to offshore wind farms in four representative locations in the Atlantic and Gulf Coastal waters of the United States. In the most vulnerable areas now being actively considered by developers, nearly half the turbines in a farm are likely to be destroyed in a 20-y period. Reasonable mitigation measures--increasing the design reference wind load, ensuring that the nacelle can be turned into rapidly changing winds, and building most wind plants in the areas with lower risk--can greatly enhance the probability that offshore wind can help to meet the United States' electricity needs.

Validation of Terra-MODIS phytoplankton chlorophyll fluorescence line height. I. Initial airborne lidar results.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra spacecraft contains spectral bands that allow retrieval of solar-induced phytoplankton chlorophyll fluorescence emission radiance. Concurrent airborne laser-induced (and water-Raman normalized) phytoplankton chlorophyll fluorescence data is used to successfully validate the MODIS chlorophyll fluorescence line height (FLH) retrievals within Gulf Stream, continental slope, shelf, and coastal waters of the Middle Atlantic Bight portion of the western North Atlantic Ocean for 11 March 2002. Over the entire approximately 480-km flight line a correlation coefficient of r2 = 0.85 results from regression of the airborne laser data against the MODIS FLH. It is also shown that the MODIS FLH product is not influenced by blue-absorbing chromophoric dissolved organic matter absorption. These regional results strongly suggest that the FLH methodology is equally valid within similar oceanic provinces of global oceans.

Chlorophyll and plankton of the Gulf coastal waters of Saudi Arabia bordering a desalination plant

As on land, plants are the real producers in the sea, and on them depend all marine living resources and the basic sustainability of ecosystems. Primary production is performed by chlorophyll-bearing plants ranging from the tiny phytoplankton to the giant kelps through the process ofphotosynthesis. Zooplankton play an important role as secondary producers, and together with phytoplankton they support the vast assemblages of marine food chain with all their diversity and complexity. Data on chlorophyll pigments, phytoplankton and zooplankton are regarded as a sound basis for environmental appraisal of ecosystems. This paper presents a set of data collected from the Saudi Arabian coastal waters near the desalination plants in AI-Jubail. Materials were collected from six different sites covering the intake and discharge zones during cruises carried out in 1997–1998. Analyses of chlorophyll pigments were made using the spectrophotometric method. Plankton samples were collected using a Nansen plankton net with a mesh size of 75 μ and analyzed following standard procedures. Chlorophyll a, b, c and phaeophytin are the most commonly occurring pigments in seawater. Their concentrations showed wide fluctuation. The phytoplankton community was composed of 35 genera representing the Diatoms, Dinoflagellates and blue- green algae. Zooplankton were composed ofProtozoa, Coelenterata, Ctenophora, Aschelminthes, Annelida, Mollusca, Arthropoda, Echinodermata and Chordata. Arthropoda, represented by Cladocera, Copepoda and Crustacean larvae, formed the largest group followed by Chordata. The distribution of phyto- and zooplankton was examined and discussed on a seasonal, annual and inter-annual basis. In terms of species, overall species composition was not affected by plant discharge. The study brings out a greater understanding of the changes experienced by biotic communities as a result of impingement, entrainment and entrapment consequent to water passage through the plant structures. The study reflects the ecological relationships that the phytoplankton and the zooplankton of the region possess with respect to intake and discharge. Further, the study has brought to light a very redeeming feature of the ecosystem to sustain its productivity and planktonic abundance. It was observed that seawater temperature, conductivity and total suspended solids did not act as limiting factors. Besides throwing much light on the little known biological aspects of desalination sites, the data provided constitute a significant addition to the knowledge base of marine living resources in an industrial zone of Gulf coastal waters.

Seasonal dispersion of petroleum contaminants in the Gulf of Thailand

Six oceanographic moorings were maintained in 1993 and 1994 and provided data on the water circulation and the flushing characteristics of the Gulf of Thailand. The concentration of dissolved and dispersed petroleum hydrocarbons (DDPH) was measured at 78 sites in 1994 and 1995 in coastal waters of the Gulf. The water circulation was sluggish and the Gulf was poorly flushed; the mean currents were generally <0.07 m s -1. Under the influence of the South China Sea, an anticyclonic gyre existed in the southeast monsoon, a cyclonic gyre in the northwest monsoon, and sluggish currents the rest of the time. Even in the dry season brackish water was found inshore; this suggests that freshwater, that arrived in the Gulf in the previous wet season, was trapped along the coast and that little mixing occurred between offshore and coastal waters. In coastal waters of the Inner Gulf and the Eastern Sea Board there were occasional acute pollution events (DDPH>40 μg l -1), superimposed 25% of the time upon chronic pollution (DDPH≈4 μg l -1) due to limited flushing of the Inner Gulf and the Eastern Sea Board, and the presence of slightly contaminated water elsewhere (DDPH<1.2 μg l -1) 75% of the time. Only the Outer Gulf seems relatively uncontaminated (DDPH≈0.01–0.1 μg l -1). The seasonal distribution of the DDPH appeared to be controlled by the water circulation; indeed the highest DDPH values in the Inner Gulf occurred in November–December because of the net currents were weak and variable. The highest DDPH values on the Eastern Sea Board occurred in April–August when the region simultaneously received contaminated coastal water from the Inner Gulf. The smallest DDPH values on the Eastern Sea Board occurred in September–November because strong westward currents prevailed which flushed the contaminants. The observed currents and DDPH data were used to drive an oil spill model which predicted that acute contamination occurs at least once a year everywhere in the Inner Gulf.

Food Habits and Dietary Overlap of Newly Settled Red Drum (Sciaenops ocellatus) and Atlantic Croaker (Micropogonias undulatus) from Texas Seagrass Meadows

Food habits and dietary overlap of newly settled larval and juvenile red drum and Atlantic croaker were examined during the period when the two species co-occur in seagrass nurseries. A total of 274 red drum (4.00 19.99 mm SL) and 205 Atlantic croaker (8.00 17.99 mm SL) were used for this analysis. Of the red drum stomachs examined, 8.4% were empty while 28.8% of Atlantic croaker stomachs contained no food. Major prey items identified for both species were calanoid copepods, harpacticoid copepods and mysid shrimp across all size classes. Ontogenetic trophic niche shifts were detected for red drum and Atlantic croaker. Type and quantity of food ingested by red drum were similar across all stations (Aransas Bay Station: lH, 2T and 3H) examined. Atlantic croaker ingested the same types of prey at all stations, but contained varying quantities of food throughout the study area. In general, high dietary overlap was observed between red drum and Atlantic croaker with most overlap values (Schoener’s index) exceeding 70%. INTRODUCTION Red drum (Sciuenops ocellutus) spend most of their adult lives offshore and migrate to tidal passes to spawn in late August through mid-November, whereas adult Atlantic croaker (Micropogonius undufutus) occupy gulf coastal waters and congregate offshore to spawn in early October through February (Johnson 1978). Pelagic larvae of both species are transported by currents through tidal inlets and into nursery habitats in bays and estuaries (Rooker et al. 1998). Consequently, larval and juvenile red drum (4 20 mm SL) occupy seagrass beds from late September to early December, while larval and juvenile Atlantic croaker (8 18 mm SL) are found in seagrass beds from early October to February (Holt et al. 1983, Rooker et al. 1998). Both species concurrently occupy seagrass beds in November at similar sizes. Conspecifics and morphologically similar species (i.e., confamilials) occupying similar habitats can potentially compete for food particularly during times when fish densities are high and prey is scarce. Intraspecific and interspecific competition among larval fishes can reduce growth rates, which in turn, may increase early-life stage mortality due to starvation or predation (Houde 1987). Therefore, it is important to understand the trophic relationships of early life stages. Fishes change resource (food) use throughout the course of their lives, especially during larval and juvenile stages. Such ontogenetic niche shifts may divide sizestructured populations into ecologically distinct stages basedon diet (Olson 19%). Duration of stages and transition among stages has the potential to minimize intraspecific competition for food. Although several studies have addressedfood habits of these two species separately (Bass and Avault 1975, Chao and Musick 1977, Oversteet and Heard 1978, Steen and Laroche 1983, Govoni et al. 1983, Cumn et al. 1984, Govoni et al. 1986, and Peters and McMichael 1987), no dietary overlap analysis has been conducted on newly settled red drum and Atlantic croaker. The primary aim of this study was to obtain an understanding of the trophic dynamics of newly settled larval and juvenile red drum and Atlantic croaker occurring in seagrass habitat. Specific objectives were to: 1) quantitatively describe the diets of larval and juvenile red drum and Atlantic croaker; 2) determine ontogenetic changes in diets of the two species; 3) determine ifdiet varies across different sites and habitats for red drum and Atlantic croaker; 4) determine interspecific dietary overlap between red drum and Atlantic croaker; and 5) determine if red drum and Atlantic croaker feed on equal quantities of food at similar sizes during the cooccurring period. MA T E R I A L S AND METHODS Diurnal sampling (0730 1700 h) was conducted weekly from October throughDecember 1994. Fish samples were taken from three stations in Aransas Bay (lH, 2T and 3H) and two stations in Redfish Bay (4H and 5T)(Figure 1). Stations lH, 3H and 4H were in shoal grass (Hulodule wrightii) while stations 2T and 5T were in turtle grass (Thulussiu testudinum) (Figure 1). A 1 m (diameter), 505 pm mesh cone net attached to a 0.75 m (length) x 0.56 m (height)epibenthic sledwas hand-towed for 20 m across the grassbed sites. Three samples f” each site were obtained picked free of grass, and preserved in 5% formalin. Standard

Inherent optical properties of the ocean: Retrieval of the absorption coefficient of chromophoric dissolved organic matter from fluorescence measurements

The quantitative relationship between the absorption and fluorescence emission of chromophoric (colored) dissolved organic matter (CDOM) has been determined along five cruise tracks in the western North Atlantic Ocean, the Gulf of Mexico, and Monterey Bay, and includes Gulf Stream, Loop Current, slope, shelf, and coastal waters. We present a protocol for the determination of CDOM fluorescence that will allow both interlaboratory comparisons and the calibration of airborne fluorescence measurements. This protocol is based on the use of the water Raman signal as an internal radiometric standard and quinine sulfate as an external standard. This study demonstrates that when an appropriate and consistent procedure is used to standardize fluorescence measurements, the fluorescence per unit absorption exhibits surprisingly little variation for diverse waters. The maximum variability observed between all sites was 36% and within the western North Atlantic the variability was only 12%. Algorithms are presented for retrieval of the absorption coefficient of CDOM at 355 and 337 nm from shipboard or airborne measurements of the water‐Raman‐normalized fluorescence emission resulting from 355‐ and 337‐nm excitation.

Direct plating procedure for enumerating Vibrio vulnificus in oysters (Crassostrea virginica).

A procedure for enumerating and identifying Vibrio vulnificus in oysters was developed and evaluated. This method consists of growth on a direct plating medium (VVE medium) for isolating the organism from shellfish tissues, followed by biochemical tests for differentiating and identifying presumptively positive isolates. Densities of V. vulnificus are reliably obtained in 2 to 4 days, and as few as 10 culturable cells per 100 g can be identified. The procedure was evaluated by using a DNA probe technique specific for the cytotoxin-hemolysin gene of V. vulnificus and gas chromatographic analysis of the fatty acid contents of positive isolates. Only 3.2 and 0.4% of the isolates gave false-positive and false-negative results, respectively. The average level of recovery on VVE medium for 33 strains, including both clinical and environmental isolates, was 92% of the level of recovery obtained with brain heart infusion agar supplemented with 1% NaCl. The densities of V. vulnificus in oyster homogenates and individual oysters harvested from gulf and Atlantic coastal waters revealed that seasonally high levels occurred. The VVE medium procedure facilitated enumeration of this pathogen in molluscan shellfish and had a distinct advantage over the widely used most-probable-number procedure for V. vulnificus enumeration, which requires 5 to 7 days and often gives improbable and imprecise results.

Hydrocarbons and related photo-oxidation products in Saudi Arabian Gulf coastal waters and hydrocarbons in underlying sediments and bioindicator bivalves

Saudi Arabian coastal waters near sandy beaches, severely contaminated with crude oil released in Kuwait during the 1991 Gulf War, as well as underlying sediments and a few bivalves, were analysed to assess concentrations and composition of petrogenic hydrocarbon mixtures and structurally related oxidation products. Concentrations of dissolved oil residues determined by UV spectrofluorometry (UVF) near oil deposits on beaches did not exceed 3.5 μg l −1; concentrations dropped to approximately 1/10th of this value a few miles offshore. Gravimetric concentrations of unfractionated lipophilic material extracted from large volumes of seawater at the same stations were up to 10 times those determined by UVF. After chromatography on silica gel, individual petroleum hydrocarbons in the low polarity fractions and oxidation products in the polar fractions were characterized by their spectra (GC/MS) and quantitated by Selected Ion Monitoring (SIM) GC/MS. Concentrations of oxidation products (ketones, aldehydes, alcohols) of aromatic hydrocarbons exceeded those of their parent compounds by more than an order of magnitude. Significant concentrations were also found of the presumably pyrogenic triplett sensitizer anthraquinone. Contributions to polar fractions of water extracts by biosynthesized lipids were negligible. UVF determinations appear to underestimate concentrations of dissolved oil residues, because many oxidation products have lower fluorescence quantum yields than the respective parent hydrocarbons. Their ecotoxicological properties are unknown. Concentrations measured in sediments by UVF ranged from 13 to 540 μg g −1 dry wt and 0.5 to 103 μg g −1 as measured by gas chromatography with flame ionization detection (FID GC). Bivalves ranged from 0.8 to 1.5 μg mg −1 extractable organic matter (EOM) by UVF, and 0.1 to 0.3 μg mg −1 EOM by GC analysis. PAHs were identified in sediment and bivalve extracts by GC/MS and quantitated by SIM GC/MS. None of the relatively water soluble alkylbenzene photo-oxidation products found in water samples nor any higher molecular weight quinones could be detected in sediment extracts. However, ion chromatograms strongly suggest the presence of numerous high molecular weight aromatics in that matrix.

Non-O1 Vibrio cholerae in Shellfish, Sediment and Waters of the U.S. Gulf Coast

In a study conducted throughout U.S. Gulf Coastal waters, Vibrio cholerae non-O1 was isolated more frequently from water samples than from shellfish or sediment samples. Frequency of V. cholerae recovery was directly related to water temperature and inversely related to salinity. The presence of V. cholerae was not adequately indicated by the fecal coliform standards for shellfish-growing waters and market shellfish as established by the National Shellfish Sanitation Program. Although all cultures tested by the Y-1 mouse adrenal cell assay or by radioimmunoassay for production of a cholera toxin-like toxin were negative, 4 of 13 isolates caused diarrhea in the infant rabbit.