Sea-water seasonal changes at a heavy tourism investment site on the Jordanian northern coast of the Gulf of Aqaba, Red Sea

The Gulf of Aqaba exhibits a strong seasonality due to convective mixing during winter and stratification during summer. The present study provides a detailed appraisal of summer and winter sea-water characteristics at the northern coast of the Gulf of Aqaba, that is witnessing rapid development and increasing changes in its geomorphological characteristics. Sea-water temperature, salinity, nutrients, and chlorophyll a concentrations were measured biweekly at five coastal and four cross-sectional stations during the periods February to April and July to September 2004. Meteorological conditions were continuously recorded at the Marine Science Station. The coastal study sites included four open coastal stations and a marina with one-way exchange with the open water. The effect of convective mixing was clearly apparent on the sea-water characteristics. Natural seasonal characteristics of higher nutrients and chlorophyll a concentrations were recorded during winter at most of the open coastal stations. In the cross-sectional stations, the concentrations of nutrients and chlorophyll a were not different between the surface and the bottom during winter, but the bottom waters had generally higher concentrations during summer. Some deviations from the natural seasonal cycle were recorded at the marina and other coastal stations. Here, higher nutrient and chlorophyll a concentrations were recorded in summer than in winter. These deviations that are most likely due to anthropogenic effects are discussed.     

Quality standard codes of reference of Jordanian coastal waters of the Gulf of Aqaba,Red Sea

Back in 1992, the Gulf of Aqaba Environmental Action Plan (GAEAP), a collaboration between the Aqaba Region Authority (ARA), Jordan and the World Bank, gave considerable emphasis to the environmental protection of the Gulf of Aqaba [The World Bank. Gulf of Aqaba Environmental Action Plan. Report No. 12244JO (1993).]. The document recommended the establishment of a marine reserve and the long term monitoring of the coastal habitats’ environmental quality. The combination of a dedicated follow up, the collaborative efforts of ARA and the Marine Science Station (MSS), and the founding of the Aqaba Special Economic Zone Authority (ASEZA) have turned the recommendations into reality. A comprehensive monitoring program of the Jordanian coastal habitats commenced in 1999. The first three years of the program were financed by a donation from The Global Environmental Facility (GEF). In return, Jordan has committed itself to the maintenance of the monitoring program as an ongoing tool for sustainable coastal management. The monitoring program includes observations on benthic habitat, fish communities, bottom sediments and seawater quality. This paper focuses on the results of seawater-quality monitoring in the first three years. Records of weather conditions, coastal currents, seawater temperature, transparency, salinity, density, pH, alkalinity, dissolved oxygen, ammonia, nitrate, nitrite, phosphate, silicate, particulate matter, chlorophyll a, zooplankton biomass, total coliform, fecal coliform, hydrocarbons and sedimentation rate have been generated monthly since January 1999 at six coastal stations, and one offshore reference station, in the Jordanian waters of the Gulf of Aqaba. The coastal stations are located at sites with different benthic habitats and are occupied by different human activities. Offshore records of density (thermohaline structure), nutrients and chlorophyll a depicted two well-defined seasons; a nutrient-/chlorophyll a-rich, mixed water winter from December to April and a nutrient-/chlorophyll a-poor, stratified water summer from June to October. Short transition seasons appeared in May and November. The mixing and stratification seasons were also clearly depicted in the coastal waters. Statistical analysis of the three-year data collected at the offshore station revealed no significant inter-annual differences in the upper 125 m of the water column with respect to any of the measured parameters. At coastal stations, the water quality at the two northernmost stations was significantly different in comparison to the upper 125 m at the offshore station and to the other coastal stations, with respect to the two key indicator parameters: inorganic nitrogen and chlorophyll a. The three-year findings of the monitoring program are employed to suggest standard codes of reference for the coastal water quality.     

Quality standard codes of reference of Jordanian coastal waters of the Gulf of Aqaba, Red Sea

Back in 1992, the Gulf of Aqaba Environmental Action Plan (GAEAP), a collaboration between the Aqaba Region Authority (ARA), Jordan and the World Bank, gave considerable emphasis to the environmental protection of the Gulf of Aqaba [The World Bank. Gulf of Aqaba Environmental Action Plan. Report No. 12244JO (1993).]. The document recommended the establishment of a marine reserve and the long term monitoring of the coastal habitats' environmental quality. The combination of a dedicated follow up, the collaborative efforts of ARA and the Marine Science Station (MSS), and the founding of the Aqaba Special Economic Zone Authority (ASEZA) have turned the recommendations into reality. A comprehensive monitoring program of the Jordanian coastal habitats commenced in 1999. The first three years of the program were financed by a donation from The Global Environmental Facility (GEF). In return, Jordan has committed itself to the maintenance of the monitoring program as an ongoing tool for sustainable coastal management. The monitoring program includes observations on benthic habitat, fish communities, bottom sediments and seawater quality. This paper focuses on the results of seawater-quality monitoring in the first three years. Records of weather conditions, coastal currents, seawater temperature, transparency, salinity, density, pH, alkalinity, dissolved oxygen, ammonia, nitrate, nitrite, phosphate, silicate, particulate matter, chlorophyll a, zooplankton biomass, total coliform, fecal coliform, hydrocarbons and sedimentation rate have been generated monthly since January 1999 at six coastal stations, and one offshore reference station, in the Jordanian waters of the Gulf of Aqaba. The coastal stations are located at sites with different benthic habitats and are occupied by different human activities. Offshore records of density (thermohaline structure), nutrients and chlorophyll a depicted two well-defined seasons; a nutrient-/chlorophyll a-rich, mixed water winter from December to April and a nutrient-/chlorophyll a-poor, stratified water summer from June to October. Short transition seasons appeared in May and November. The mixing and stratification seasons were also clearly depicted in the coastal waters. Statistical analysis of the three-year data collected at the offshore station revealed no significant inter-annual differences in the upper 125 m of the water column with respect to any of the measured parameters. At coastal stations, the water quality at the two northernmost stations was significantly different in comparison to the upper 125 m at the offshore station and to the other coastal stations, with respect to the two key indicator parameters: inorganic nitrogen and chlorophyll a. The three-year findings of the monitoring program are employed to suggest standard codes of reference for the coastal water quality.     

A comparative seasonal study of two populations of Hypnea musciformis from the East and West Coasts of Florida,USA I. Growth and chemistry

Dry weight levels of the red alga Hypnea musciformis (Wulfen) Lamouroux from Atlantic and Gulf of Mexico coastal sites in florida, USA were lowest in the late winter and early spring, increasing through the summer and highest in the fall. There was a two-month lag in the Gulf coast population's dry weight pattern, indicating differing growth patterns. Chlorophyll a, phycoerythrin and phycoerythrin/chlorophyll a ratios were highest in the winter and lowest in the summer for both populations. Total pigment levels for H. musciformis from the Atlantic coast site were significantly greater than those of the Gulf coast. Protein and carbohydrate percentages were inversely related in both populations, with carbohydrate levels highest in summer and protein levels highest in winter. The Gulf coast population contained significantly more protein than the Atlantic coast plants. Carrageenan levels were highest in spring and lowest in fall, the Atlantic coast population generally had higher levels than the Gulf coast population. The differences in seasonal patterns and levels of the chemical constituents were reflected by distinct morphological characteristics for each population. The Atlantic coast population was larger, darker, more coarse in texture and possessed more crozier branch tips than the Gulf coast plants. These distinctions represent acclimitization responses that relate to habitat differences.     

Bioassay of biotin and its distribution in the sea

A simple, rapid and sensitive method of microbiological assay for the determination of biotin in seawater has been developed by using a marine bacterium, Achromobacter sp. (Strain yH-51) as an assay organism. When the organism was incubated at 25°C for 48 h in a synthetic medium with constant shaking, a standard reference curve of bioassay was obtained. The organism is sensitive in the range 0.1 to 8.0 ng/l biotin. The distribution of biotin has been determined in the East China Sea, the North Pacific Ocean, and the bays and inlets along the Pacific coast of Japan. Biotin concentrations in surface waters were in the range from less than 0.1 ng/l up to 57.9 ng/l; generally high in coastal waters and low in deep open waters. The concentrations were generally high in surface waters, and rapidly decreased with depth down to 50 m, below which values were generally low. The vertical distribution of biotin followed closely the concentration of chlorophyll a, with high concentrations of biotin restricted to the euphotic layer of high chlorophyll a contents at most stations observed. Biotin concentrations in surface waters were generally high during summer, but in autumn and winter the concentrations decreased markedly.     

Chlorophyll blooms and the spring/neap tidal cycle: observations at two stations on the coast of Connemara,Ireland

Water temperature, chlorophyll a and phaeophytin were recorded every 2 to 4 d, in order to describe short-term variability in phytoplankton blooms. Data were collected from May to September 1984 and March to September 1985 at shore stations on the coast of Connemara, western Ireland. Comparisons with offshore data suggest that the shore data is representative of coastal water. Chlorophyll a was highest at neap tides in spring, and at spring tides in early summer. In late summer, transient chlorophyll blooms occurred at neap tides, possibly due to a localized accumulation of flagellates in stable conditions.     

Relationships between nutrients and macroalgal biomass in a brazilian coastal lagoon: the impact of a lock construction

The Piratininga Lagoon is a coastal, choked, and brackish ecosystem in SE Brazil, where uncontrolled discharge of domestic sewage led to eutrophication, increasing massive proliferation of benthic macroalgae, and decrease of the lagoon mean depth. In 1992, a dam was constructed by the local Municipality at its tidal channel aiming at stabilising its water level. Main physico-chemical parameters, together with macroalgae biomass, nutrient concentrations in the water column, particulate organic carbon, and chlorophyll a were recorded monthly at 4 sampling stations within the Piratininga lagoon from April 1994 to April 1995. The data, compared with “before-lock” existing studies, show that nutrients and chlorophyll a concentrations significantly increased after the lock construction. Based on the functioning of the ecosystem, we propose to harvest the algal mats before their decomposition period in order to partly remove the nutrient stocks from the lagoon and the future ecosystem modelling to predict the impact of natural and anthropogenic eutrophication.     

Mechanisms of production and fate of organic phosphorus in the northern Adriatic Sea

In the period from 1980 to 1984 organic phosphorus, nutrients, primary production rates (¹⁴C), chlorophyll a (chl a) standing crops, and basic oceanographic parameters were measured during 23 cruises at six stations in the open waters of the northern Adriatic Sea. These waters are significantly influenced by polluted Po River discharge. Organic phosphorus was correlated with several parameters which characterize phytoplankton activity and organic matter decomposition processes. In the late winter-spring period, organic phosphorus is produced during phytoplankton blooms. It is hypothesized that microzooplankton grazing is the main factor increasing the organic phosphorus concentrations in summer (up to 1.1 mol 1^-1). Fall and winter had much lower values (below 0.3 mol 1^-1) due to remineralization processes and an increased water mass exchange between the northern and central Adriatic regions. The direct contribution of organic phosphorus by freshwater discharge was not found to be significant. The higher organic phosphorus concentrations that can occur in low salinity waters are most likely due to their increased capability to support primary production.     

Growth,reproduction and gross biochemical composition of the Manila clam Ruditapes philippinarum in the Bay of Arcachon,France

Growth, reproduction and gross biochemical composition of the Manila clam Ruditapes philippinarum were studied for one oceanic and two inner stations in the Bay of Arcachon, France, from March 1989 to March 1991. During this period, sea-water temperature, salinity and chlorophyll a were also recorded. A marked increase in length occurred during the first year in all areas, after which growth rates decreased. In contrast, weight increased more steadily. The Manila clam exhibited best development in the oceanic area, but there was no difference in growth of clams between the two inner stations. Differences in growth between oceanic and inner stations may result from differences in fluctuations of environmental conditions such as temperature and salinity. Except for higher carbohydrate contents in clams recovered in autumn from the oceanic station Le Ferret, biochemical components differed little between stations. During the second winter, glycogen levels were relatively low, but no mortalities were recorded. On the other hand, sowing spat in autumn instead of spring or sowing larger-sized spat did not reduce the time required for culture of R. philippinarum.     

Light acclimation states of phytoplankton in the Southern Ocean, determined using photosynthetic pigment distribution

In high-latitude waters such as the Southern Ocean, the primary production of phytoplankton supports the ecosystem. To understand the photo-acclimation strategy of such phytoplankton within cold environments, the vertical distribution profile of photosynthetic pigments was analyzed in the Southern Ocean. Samples were taken along 110°E during the austral summer, and along 150°E and around the edge of the seasonal sea ice of the Antarctic Continent during the austral autumn. Pigment extraction methods were optimized for these samples. The standing crop of chlorophyll a was larger in the region along the edge of the seasonal sea ice than at sampling stations in open ocean areas. Chlorophyll concentration seemed to be dependent on the formation of thermo- and haloclines along the edge of the seasonal sea ice, but not in the open ocean where such clines are less pronounced. The marker pigments fucoxanthin and/or 19′-hexanoyloxyfucoxanthin were dominant at most sampling stations throughout the water column, while other marker pigments such as alloxanthin were quite low. This indicated that diatoms and/or haptophytes were the major phytoplankton in this area. Comparison of the relative ratio of fucoxanthin with that of 19′-hexanoyloxyfucoxanthin allowed some stations to be characterized as either diatom-dominant or haptophyte-dominant. The relative ratio of xanthophyll-cycle pigments (diadinoxanthin plus diatoxanthin) to chlorophyll a was high in surface waters and decreased gradually with depth. This suggests that near the ice edge during summer in the Southern Ocean, both diatoms and haptophytes acclimate to their light environments to protect their photosystems under high-light conditions.     

Seasonal growth and composition of fronds of Macrocystis pyrifera in the Falkland Islands

Frond growth of Macrocystis pyrifera in the Falkland Islands was monitored in shallow coastal water from December 1985 to March 1987, and at a different site in deeper water from December 1985 to June 1986. Growth rates in the deeper bed were generally higher than those recorded in the coastal zone. At both sites, node initiation and elongation rate fluctuated according to the seasonal pattern of light or water temperature. In the shallow coastal area, nitrate was abundant in the winter and below detection levels during late spring and summer. Correlation analysis suggests that the production of the fronds of the giant kelp in this area was probably inhibited during the summer months by extremely low concentrations of nutrients. Internal nitrogen was exhausted approximately one month after a sharp decline in ambient nitrate concentration, and carbon reserves were formed. In the deeper bed of M. pyrifera, nitrogen was abundant all year round and the production of the fronds reflected the seasonal pattern of light or water temperature. The nitrogen content of the tissue probably did not drop below a level that limited production, and no internal carbon reserves were accumulated.     

Aspects of water column primary productivity in the Chukchi Sea during summer

Measurements of primary productivity, chlorophyll a, incident solar radiation, phosphate-P, silicate-Si, nitrate-N, nitrite-N, ammonium-N, temperature and salinity were made in the Marginal Ice Zone of the Chukchi Sea in summer 1974. Low to moderate levels of primary productivity (0.07 to 0.97 g C m^-2 half-day^-1) were observed; primary productivity exceeded 3 g C m^-2 half-day^-1 at two stations. Surface primary productivity was nitrogen-limited at most stations. Mean chlorophyll a concentration in the photic zone varied from 0.4 to 17.8 mg m^-3. Higher concentrations and significant subsurface accumulation of chlorophyll a, reaching 40 mg m^-3, were observed in July at stations near the ice-edge than those in open water. No chlorophyll maximum was noted in September, when values ranged from 0.4 to 2.2 mg m^-3. It is postulated that the contribution of sea-ice algae to the total chlorophyll content can be substantial, but that the stay of these cells in the water column may not be long. Non-linear regression estimates from solar radiation and chlorophyll-specific primary productivity data showed a maximal photosynthetic rate of 18 mg C mg chlorophyll a ^-1 half-day^-1, an optimal light intensity of 54 langleys half-day^-1, and markedly reduced primary productivity at moderately higher light intensities. These features indicate that phytoplankton was shade-adapted.     

Phytoplankton blooms are strongly impacted by microzooplankton grazing in coastal North Pacific waters

Phytoplankton growth and microzooplankton grazing were measured in two productive coastal regions of the North Pacific: northern Puget Sound and the coastal Gulf of Alaska. Rates of phytoplankton growth (range: 0.09–2.69 day⁻¹) and microzooplankton grazing (range: 0.00–2.10 day⁻¹) varied seasonally, with lowest values in late fall and winter, and highest values in spring and summer. Chlorophyll concentrations also varied widely (0.19–13.65 μg l⁻¹). Large (>8 μm) phytoplankton cells consistently dominated phytoplankton communities under bloom conditions, contributing on average 65% of total chlorophyll biomass when chlorophyll exceeded 2 μg l⁻¹. Microzooplankton grazing was an important loss process affecting phytoplankton, with grazing rates equivalent to nearly two-thirds (64%) of growth rates on average. Both small and large phytoplankton cells were consumed, with the ratio of grazing to growth (g:μ) for the two size classes averaging 0.80 and 0.42, respectively. Perhaps surprisingly, the coupling between microzooplankton grazing and phytoplankton growth was tighter during phytoplankton blooms than during low biomass periods, with g:μ averaging 0.78 during blooms and 0.49 at other times. This tight coupling may be a result of the high potential growth and ingestion rates of protist grazers, some of which feed on bloom-forming diatoms and other large phytoplankton. Large ciliates and Gyrodinium-like dinoflagellates contributed substantially to microzooplankton biomass at diatom bloom stations in the Gulf of Alaska, and microzooplankton biomass overall was strongly correlated with >8 μm chlorophyll concentrations. Because grazing tended to be proportionally greater when phytoplankton biomass was high, the absolute amount of chlorophyll consumed by microzooplankton was often substantial. In nearly two-thirds of the experiments (14/23), more chlorophyll was ingested by microzooplankton than was available for all other biological and physical loss processes combined. Microzooplankton were important intermediaries in the transfer of primary production to higher trophic levels in these coastal marine food webs. Received: 12 November 1999 / Accepted: 4 October 2000     

Studies of primary productivity in coastal waters of southern Long Island,New York

Phytoplankton productivity of the tidal estuaries and coastal waters of southern Nassau Country, Long Island, New York, USA was determined monthly at 28 stations during 1966. Diatoms alternated with dinoflagellates in dominating the standing crop in the coastal area. The estuaries were characterized by sustained blooms of green flagellates and dinoflagellates during the spring/summer period, 1966. Chlorophyll a ranged from 1.0 to 27.6 mg/m³ in the estuarine area, and 1.45 to 10.15 mg/m³ in adjacent coastal waters. Rate of phytosynthesis per unit weight chlorophyll a for surface samples in the region under study a veraged from 3.1 to 3.5 mgC/mg chlorophyll a/h. At light saturation, however, the ratio varied according to water temperature and species' composition. Primary productivity decreased seawards, with mean values for 1966 of 0.35, 0.22, and 0.16 gC/m³/d for the estuarine, nearshore and offshore areas, respectively.This study was carried out at the Lamont Geological Observatory of Columbia University Palisades; New York, USA.The study was conducted with financial assistance from Nassau County, New York, and the G. Unger Vetlesen Foundation.     

Plankton community dynamics of the central Great Barrier Reef Lagoon: Analysis of data from Ikeda et al.

Plankton data collected by Ikeda et al. (1980) from the central region of the Great Barrier Reef, and spanning two years (1976 through 1978) of zooplankton records, have been analyzed extensively for spatial and temporal patterns. Estimates of net zooplankton (including chaetognaths, copepods, and larvaceans) and microzooplankton (juvenile copepods, encompassing nauplii and copepodites, and ciliates) were assessed at three stations across the 60 km lagoon. Temperature, salinity, and chlorophyll a were also measured. A cross-lagoonal gradient was identified in the plankton, concurring with results of related surveys of benthic taxa, such as scleractinian corals, soft corals, macro-algae, fish, sponges, crinoids, etc. Two associations of net zooplankton were identified. The first was associated primarily with the inner lagoon; the second with the outer lagoon. The inshore association was characterized by higher abundances of almost all net zooplankton taxa, particularly chaetognaths, copepods, polychaetes, decapods, and meroplanktonic larvae as well as higher concentrations of chlorophyll a. This inshore association wove back and forth across the lagoon through time, dominating the lagoon entirely during periods of high river discharge, reaching the mid-shelf platform reefs in this region, and sometimes being entirely absent during dry periods. Both seasonal and annual peaks in plankton abundance were generally linked with degree of runoff. Summer/autumn peaks of abundance were evident in chaetognaths, copepods, and larvaceans while annual variation was detected in the former two as well as in chlorophyll a concentrations. Depth stratification was noted in juvenile copepods and chlorophyll a concentrations at the center of the lagoon, with higher abundances recorded in deeper waters. The central Great Barrier Reef lagoon was found to be typical of other tropical coastal waters where plankton community dynamics are controlled primarily by physical factors. We suggest that any substantial changes in river discharge in this area will affect plankton production.A.I.M.S. Contribution No. 242     

Characteristics and potential environmental impacts of sand material from sand dunes and uplifted marine terraces as potential borrow sites for beach nourishment along the Jordanian coast of the Gulf of Aqaba

The coastal zone management and development plans which include tourism development necessitate among many other management practices, the extension of the available area of the present natural but narrow, limited and widely eroded beaches by implementing some type of nourishment practices. The present work is providing information on selected sites as possible sources of suitable sand, chemical and granulometric characteristics of their sand, and the potential direct and long-term environmental effects and consequences of its use in any future nourishment practices. Seven sites located within the up-lifted terraces area along the Jordanian portion of the Gulf of Aqaba, were selected as potential sources or borrow sites for sand that may be used in any future nourishment projects. Two sites were selected at the northeastern side of Aqaba region to represent sand dunes. Sand material from these sites were analyzed for their physical characteristics (grain size) as well as their content of heavy metals, organic carbon, total nitrogen, total phosphorous, and calcium carbonate. Standard methodological techniques were used during analysis of all constituents. The results were compared with those obtained from the analysis of sand deposits of six beaches along the Jordanian coastline of the Gulf of Aqaba. Results indicate that sand of the selected borrow sites has grain size fractions that are suitable for use in beach nourishment. Results of the measured pollution indicators indicate that their levels in the sand of the potential borrow sites are within or lower than their levels in the marine and coastal sediments of the Gulf of Aqaba and the Red Sea. These properties, in addition to the wide occurrence and availability of such sources along the coasts of the Red Sea and the Gulf of Aqaba, suggest that it will be a cheep source of sand for beach extension and restoration and their use in large amounts in beach nourishment project will not pose major hazards on the quality of seawater of the Gulf of Aqaba area     

Salps in the Lazarev Sea,Southern Ocean: I. Feeding dynamics

Feeding dynamics of the Antarctic salps Ihlea racovitzai and Salpa thompsoni were studied in the Lazarev Sea in fall 2004, summer 2005–2006 and winter 2006. Pigment concentrations in the guts of both species were positively correlated with ambient surface chlorophyll a (chl a). No evidence was found for salp clogging even at dense surface concentrations of up to 7 μg chl a L⁻¹. However, gut pigment concentrations had a lower range than ambient pigment concentrations, suggesting that salps increased retention times of ingested material in low-food environments. For medium-sized I. racovitzai and S. thompsoni, estimated individual daily rations reached 7–10 and >100% of body carbon in winter and summer, respectively. Daily respiratory needs of I. racovitzai and S. thompsoni accounted for 28 and 22% of daily carbon assimilation based on pigment ingestion rates in winter, and for 2 and 1% in summer, respectively. The grazing impact of the salp populations on the phytoplankton standing stock was negligible during all seasons due to generally low salp densities. Fatty acid trophic biomarkers in the salps suggest high year-round contributions of flagellates and modest contributions of diatoms to the salp’s diet. These markers showed low seasonal variability for I. racovitzai. The more pronounced seasonality of trophic markers in S. thompsoni were likely related to their generally deeper residence depth in winter linked to a seasonal alternation of sexual and asexual generations.     

Differences in productivities between the Great Australian Bight and the Gulf of Carpentaria,Australia, in summer

Phytoplankton standing crop (chlorophyll a) and primary productivity were recorded, and zooplankton biomass was estimated in the two large bays of Australia, the Great Australian Bight on the south coast (December, 1965) and the Gulf of Carpentaria on the north coast (December, 1968). In the Gulf of Carpentaria, the phytoplankton standing crop (average, 27.3 mg chlorophyll a m^-2) and primary productivity (average, 133.1 mg C m^-2 h^-1), as well as zooplankton biomass (average, 305.3 mg wet weight m^-3) are much higher than in the Great Australian Bight (12.1 mg chlorophyll a m^-2, 18.2 mg C m^-2 h^-1, 7.1 mg wet weight m^-3, respectively). The unexpectedly low productivity values in the Great Australian Bight are attributable to environmental conditions of this bay, which obtains neither replenishment of nutrients from the land nor receives upwelling of deep water.     

GIS and remote sensing as tools for conducting geo-hazards risk assessment along Gulf of Aqaba coastal zone,Egypt

Satellite remote sensing data, in addition to Geographic Information Systems (GIS), offers an excellent alternative to conventional mapping techniques in monitoring and mapping of geo-hazards areas. One of the most sustainable development projects in Egypt has been accomplished in Sinai, especially along and around the Gulf of Aqaba and the Gulf of Suez. Variations along the coastal zone of the Gulf of Aqaba have been identified through the analysis of multi-temporal satellite images with the aid of GIS analysis. The study area is subject to rapid and increasing changes in land-use/land-cover that resulting from natural and human activities such as flash flooding, seismic activity, landslides, and tourist and urban activities. This is in addition to the construction projects of roads, ports, PowerStation stations, mineral exploration, beaches, and tourist villages resulting from major environmental impacts. The current study aims to use Remote Sensing and GIS tools to investigate, monitor, and assess geo-hazards through the building of a geographical database. Several techniques have been developed over the last decade mostly to study the geological and geomorphologic characteristics of the terrain; land-use and land-cover changes. These are based on satellite imagery and Digital Elevation Models (DEM) to determine the topographic features, and geo-hazards maps. It is concluded that integrated approaches to monitoring can successfully be used to assess the environmental impacts along the Gulf of Aqaba coastal zone.     

Nutrient characteristics and sediment texture of the seagrass beds of the Gulf of Mannar

Changes in nutrient concentrations and sediment texture of the seagrass beds were recorded for two years from July 1996 to June 1998 at monthly intervals at two stations (Station 1--Manoli island; Station 2--Chinnapalam) of the Gulf of Mannar Marine Biosphere Reserve. Different nutrients in water showed varied concentrations in different seasons. Phosphate concentration varied between 2.32 and 7.32 microM, nitrate concentration ranged from 5.2 to 18.78 microM and nitrite concentration from 1.92 to 732 microM. Sand was a major component of the sediments, followed by silt and clay at both the stations. At station 1, sand composition varied between 85.9 and 95.3% while at station 2, it varied between 81.9 and 93.6%. Silt composition varied between 3.1 and 9.4% at station land at station 2, it varied between 4.0 and 12.4%. At station 1, clay composition varied from 1.6 to 4.6% and at station 2, it varied between 2.1 and 5.6%. The present study revealed that the nutrients and sediment characteristics of the seagrass beds of the Gulf of Mannar has clear spatial and temporal variations. They are largely interlinked and influenced by the human activities and climatic changes and are individually or jointly governing the distribution, diversity, biomass and productivity of the seagrasses of the Gulf of Mannar.