A Floristic and ecological survey of Assateague Island, Virgina-Maryland

Assateague Island is an offshore bar comprising the south-eastern coast of Maryland and the northeastern coast of Virgina. It is part of the system of discontinuous barrier reefs or bars which occupy most of the Atlantic shoreline from Florida to Massachusetts. These are unstable bars, continuously influenced by storm winds and tides which provide a distinct and rigorous habitat for the vegetation there. General floras of the Delmarva Peninusla do not mention Assateague Island specifically. The objective is to prepare a catalog of the vascular plants of Assateague Island and to describe the communities in which they are found, in the hope it will add to the knowledge of barrier reef vegetation.

Effects of a flash-flood on channel morphology and some insects of a small stony stream in the Peak District, Derbyshire

In this paper, some observations are made following a flash-flood that occurred in Stake Clough, a small tributary of the River Goyt, during the evening of 6 August 1996. The site was visited eight times between 8 August - 30 October 1996 to take samples and make observations on the stream. The flood scoured the bed of Stake Clough but more significantly, caused it to change course along the middle part of the floodplain. Initially after the flood, the numbers of insects in all stretches of the stream channel were low (100-200 m super(2)), but then gradually rose to population densities approaching ten times this figure. The benthos was dominated by the Chironomidae and also leuctrid stoneflies (Leuctra nigra, L. hippopus and L. inermis). On 8th August 1996, 12 mesh bags, each containing oak leaves, were placed in the stream and collected after 24 hours. These were also dominated by chironomids, and contained relatively high numbers of the caddis, Potamophylax cingulatus.

The production of algae growing on gravel in a chalk-stream

Epilithic algae, ie that growing on the surface of stones, was studied as part of the work on the energy flow of the chalk-stream ecosystem, by the River Laboratory. The study area was on Bere Stream and 2 neighbouring streams. The algal biomass was estimated from analysis of chlorophyll a. In Bere Stream the peak chlorophyll a cover occurred in April, while in the neighbouring streams, which have considerably lower nutrient levels, there was on peak. Assuming that 2% of a diatoms dry wt is chlorophyll a, then even in mid-April the biomass of epilithic algae amounted to no more than 15 g dry wt m Super(-2) of exposed gravel. Annual production was calculated to be > 15 times greater than biomass. The estimation of net primary production is always difficult for benthic floras and comparisons are especially difficult when different methods are used. But these figures contrast sharply with those for Ranunculus (water crowfoot) which has a ratio of annual production to maximal seasonal biomass of 1:16. The accumulation of algal biomass is apparently being prevented. Some organic matter may be excreted; some algae will be washed off the bed of the stream by current and grazing by herbivorous invertebrates will also tend to prevent algal accumulation.

The study of the sedimentation mechanism in channels under the impact of tidal currents

The purpose of this research is to study sedimentation mechanism by mathematical modeling in access channels which are affected by tidal currents. The most important factor for recognizing sedimentation process in every water environment is the flow pattern of that environment. It is noteworthy that the flow pattern is affected by the geometry and the shape of the environment as well as the type of existing affects in area. The area under the study in this thesis is located in Bushehr Gulf and the access channels (inner and outer). The study utilizes the hydrodynamic modeling with unstructured triangular and non-overlapping grids, using the finite volume, From method analysis in two scale sizes: large scale (200 m to 7.5km) and small scale (50m to 7.5km) in two different time durations of 15 days and 3.5 days to obtain the flow patterns. The 2D governing equations used in the model are the Depth-Averaged Shallow Water Equations. Turbulence Modeling is required to calculate the Eddy Viscosity Coefficient using the Smagorinsky Model with coefficient of 0.3. In addition to the flow modeling in two different scales and the use of the data of 3.5 day tidal current modeling have been considered to study the effects of the sediments equilibrium in the area and the channels. This model is capable of covering the area which is being settled and eroded and to identify the effects of tidal current of these processes. The required data of the above mentioned models such as current and sediments data have been obtained by the measurements in Bushehr Gulf and the access channels which was one of the PSO's (Port and Shipping Organization) project-titled, "The Sedimentation Modeling in Bushehr Port" in 1379. Hydrographic data have been obtained from Admiralty maps (2003) and Cartography Organization (1378, 1379). The results of the modeling includes: cross shore currents in northern and north western coasts of Bushehr Gulf during the neap tide and also the same current in northern and north eastern coasts of the Gulf during the spring tide. These currents wash and carry fine particles (silt, clay, and mud) from the coastal bed of which are generally made of mud and clay with some silts. In this regard, the role of sediments in the islands of this area and the islands made of depot of dredged sediments should not be ignored. The result of using 3.5 day modeling is that the cross channels currents leads to settlement places in inner and outer channels in tidal period. In neap tide the current enters the channel from upside bend of the two channels and outer channel. Then it crosses the channel oblique in some places of the outer channel. Also the oblique currents or even almost perpendicular current from up slope of inner channel between No. 15 and No. 18 buoys interact between the parallel currents in the channel and made secondary oblique currents which exit as a down-slope current in the channel and causes deposit of sediments as well as settling the suspended sediments carried by these currents. In addition in outer channel the speed of parallel currents in the bend of the channel which is naturally deeper increases. Therefore, it leads to erosion and suspension of sediments in this area. The speed of suspended sediments carried by this current which is parallel to the channel axis decreases when they pass through the shallower part of the channel where it is in the buoys No.7 and 8 to 5 and 6 are located. Therefore, the suspended sediment settles and because of this process these places will be even shallower. Furthermore, the passing of oblique upstream leads to settlement of the sediments in the up-slope and has an additional effect on the process of decreasing the depth of these locations. On the contrary, in the down-slope channel, as the results of sediments and current modeling indicates the speed of current increases and the currents make the particles of down-slope channel suspended and be carried away. Thus, in a vast area of downstream of both channels, the sediments have settled. At the end of the neap tide, the process along with circulations in this area produces eddies which causes sedimentation in the area. During spring some parts of this active location for sedimentation will enter both channels in a reverse process. The above mentioned processes and the places of sedimentation and erosion in inner and outer channels are validated by the sediments equilibrium modeling. This model will be able to estimate the suspended, bed load and the boundary layer thickness in each point of both channels and in the modeled area.

Lake Kainji water hyacinth infestation and the control strategies

The paper documents the aquatic vascular plants situation of Lake Kainji, particularly with the invasion of water hyacinth (Eichhormia crassipes) hitherto alien to the lake system. The frequency of occurrence of some aquatic plants on Lake Kainji have increased whilst a few decreased over the period between 1984 and 1995. More than 53.6% of the lake surface has now been covered by aquatic vascular plants of which water hyacinth alone covered 30.6% (16.4% of the system). Apart from the characteristic rapid multiplication and biomass build-up of the plant, more than 9.1 clumps with a diameter range between 0.8-4cm enter the lake per minute. Thus more than 16.4ha per day or annually 6000ha of water hyacinth are added as drifts. Because of the peculiar hydrological cycle of the lake and the plant aggressiveness and invasiveness, NIFFR (with the support of the GTZ) had developed an approach of control which combines manual, biological, natural, boom construction and chemical measures. These are discussed

Preliminary report on bottlenose dolphin (Tursiops truncatus) uterine samples for parity analysis

There have been numerous studies on various mammalian species regarding vascular changes in uterine arteries elucidating the effects of parity. In equids, vascular changes of uterine arteries have been demonstrated to occur in uniparous and multiparous mares. The severity of these arteriole changes suggests a link to previous pregnancies. Differences in the number or range of pregnancies can be ascertained through microscopic evaluation of elastin deposition in the arterioles, perivascular fibrosis, and stromal cellularity. There has been little, if any, work performed on parity in the bottlenose dolphin (Tursiops truncatus). The objective of this preliminary study was to determine the feasibility of detecting similar vascular changes in the endometrium of known-aged female bottlenose dolphins to assess parity. Archived formalin fixed samples of uterus were obtained from nine bottlenose dolphins with known age and parity. Four slides were made from each sample and individually stained with four different techniques. From our small sample pool, it appears that uteri from nulliparous animals do not develop perivascular fibrosis. Parous uteri developed perivascular fibrosis and arteriolar elastosis. These changes agree with our expectations that some degeneration (elastosis) and compensation (fibrosis) occurs as a result of uterine expansion of pregnancy. The assessment of this technique for use in bottlenose dolphins would provide an important tool in the determination of the reproductive success of dolphin populations, identify individuals who are sexually mature but nulliparous, which could indicate reproductive dysfunction or increased calving intervals, and increase our knowledge on the role contaminants play in reproductive dysfunction.