In vitro Antioxidant activity and Phytochemical composition of Syringodium isoetifolium

Seagrass are the marine flowering plants found mainly in clear, shallow estuaries and coastal waters. In all temperate and trophical region seagrasses grow both internally and subtidally. One such seagrass namely Syringodium isoetifolium has many medicinal properities. This seagrass have most promising pharmacological activities which may include anti-inflammatory, anticancer, antidiarrheal, antihaemorrhoidal activities. This study is focussed on the phytochemical evaluation and in vitro antioxidant activity of aqueous, ethanol and hydroalcoholic extract of Syringodium isoetifolium. The qualitative analysis of Syringodium isoetifolium shows the presence of tannin, saponin, flavonoids, steroids, terpenoids, alkaloids, anthraquinone, polyphenol and coumarin. In all the three extracts only ethanol shows the high concentration of phytocompounds. Emodins, glycoside and anthocyanin were found to be absent in all the three extracts. Quantitative analysis of total phenol, flavonoid, saponin and tannin were found to be 193.10 ±13.52, 106.11 ± 7.42, 52.96 ± 3.64 and 81.30 ± 5.69. Superoxide anion radical, Nitric oxide and Hydroxy radical scavenging assay showed that Syringodium isoetifolium was an excellent scavenger of these radicals. These results are an indication of the potent antioxidant property of the extract and may be responsible for some of the therapeutic uses of Syringodium isoetifolium.

7Be/210Pbxs Ratio-Derived Age and Residence Time of Suspended Sediments in Galveston Bay

The winds associated with the passage of meteorological fronts cause waves that induce sediment remobilization/resuspension, especially within shallow estuaries such as Galveston Bay. The passage of cold fronts, collectively, on an annual to decadal basis, generate more sediment resuspension than most hurricanes and tropical storms. With a warming climate, the intensity of all meteorological events is shifting toward having greater impacts on these biologically productive environments. To better understand sediment resuspension within the bay, water samples were collected during frontal passages at two locations in Galveston Bay, including one location in the middle portion of the bay and another closer to the mouth of the bay. By collecting precipitation, water samples in both the middle and lower bay, and measuring the ratio of 7Be/210Pbxs in these samples; we quantified the residence times of total suspended sediment (TSS) in middle and lower Galveston Bay. Our results showed that suspended sediment age increased and percent of new suspended sediment decreased along the axis from the middle bay to the lower bay. This results from the initial introduction of newly labeled isotopes and suspended load coming from fluvial discharges which enter at the top of the bay and travel through the bay. The age of suspended sediment from the first sampling event was 70 ± 10 days, whereas the age in the second event was 16 ± 3 days greater. In the last sampling event, the age of suspended sediment event was 35 ± 7.4 days younger than the second, suggesting that the majority of suspended sediments was likely transported entirely out of the bay by the second cold front, prior to the final sampling event. This indicates that there are longer suspended sediment residence times when the water is trapped within the bay. Our estimated residence time of suspended sediments (51–105 days) suggest the particle-bound contaminants adsorb to suspended sediment may spend months suspended in the bay before exiting the bay or being accreted into the bay sediment column, increasing the exposure time of living organisms to various particle-bound contaminants.

Using Drones to Measure Jellyfish Density in Shallow Estuaries

Understanding jellyfish ecology and roles in coastal ecosystems is challenging due to their patchy distribution. While standard net sampling or manned aircraft surveys are inefficient, Unmanned Aerial Vehicles (UAVs) or drones represent a promising alternative for data collection. In this technical report, we used pictures taken from a small drone to estimate the density of Aurelia sp. in a shallow fjord with a narrow entrance, where the population dynamic is well-known. We investigated the ability of an image processing software to count small and translucent jellyfish from the drone pictures at three locations with different environmental conditions (sun glare, waves or seagrass). Densities of Aurelia sp. estimated from semiautomated and manual counts from drone images were similar to densities estimated by netting. The semiautomated program was able to highlight the medusae from the background in order to discard false detections of items unlikely to be jellyfish. In spite of this, some objects (e.g., seagrass) were hardly distinguishable from jellyfish and resulted in a small number of false positives. This report presents a preview of the possible applications of drones to observe small and fragile jellyfishes, for which in situ sampling remains delicate. Drones may represent a noninvasive approach to monitoring jellyfish abundance over time, enabling the collection of a large amount of data in a short time. Software development may be useful for automatically measuring jellyfish size and even population biomass.

Shady business: the darkening of estuaries constrains benthic ecosystem function

Coastal intertidal soft-sediment habitats provide ecosystem services to millions of people worldwide, yet are under intense pressure from land-use change and sea-level rise (SLR). Both pressures interact to reduce light reaching the seafloor, thereby disrupting benthic primary producers and the ecosystem functions and services they provide. This study considers the implications of altered light climate on microphytobenthic (MPB) production in shallow estuaries. Continuous measurements of seafloor photosynthetically active radiation (PAR) were made over 9 mo on intertidal sandflats in 14 New Zealand estuaries spanning a turbidity gradient. A literature summary of benthic photosynthesis-irradiance curves was used to predict PAR limitation at sampling sites. Estimates of the proportion of time MPB would be light limited during emersion ranged from a median of 32-64% compared to a median of 55-100% during immersion. For estuaries close to 100% PAR limitation during immersion, emerged intertidal areas represent a refuge for MPB production which is vulnerable to SLR. Based on hypsometric curves (a representation of estuary bathymetry), the intertidal area of our study estuaries is predicted to decrease by 27-94% in response to SLR of 1.4 m. The combination of high PAR limitation during immersion and large losses of intertidal area will increase vulnerability to the loss of MPB production and the associated ecosystem services, which will push these ecosystems towards tipping points. The research highlights how the interplay between local and global scale stressors may ultimately trigger ecological collapse under future global change.

Modelling the Influence of Riverine Inputs on the Circulation and Flushing Times of Small Shallow Estuaries

Simple flushing time calculations for estuarine systems can be used as proxies for eutrophication susceptibility. However, more complex methods are required to better understand entire systems. Understanding of the hydrodynamics driving circulation and flushing times in small, eutrophic, temperate estuaries is less advanced than larger counterparts due to lack of data and difficulties in accurately modelling small-scale systems. This paper uses the microtidal Christchurch Harbour estuary in Southern UK as a case study to elucidate the physical controls on eutrophication susceptibility in small shallow basins. A depth-averaged hydrodynamic model has been configured of the estuary to investigate the physical processes driving circulation with particular emphasis on understanding the impact of riverine inputs to this system. Results indicate circulation control changes from tidally to fluvially driven as riverine inputs increase. Flushing times, calculated using a particle tracking method, indicate that the system can take as long as 132 h to flush when river flow is low, or as short as 12 h when riverine input is exceptionally high. When total river flow into the estuary is less than 30 m3 s−1, tidal flux is the dominant hydrodynamic control, which results in high flushing times during neap tides. Conversely, when riverine input is greater than 30 m3 s−1, the dominant hydrodynamic control is fluvial flux, and flushing times during spring tides are longer than at neaps. The methodology presented here shows that modelling at small spatial scales is possible but highlights the importance of particle tracking methods to determine flushing time variability across a system.

Shark detection probability from aerial drone surveys within a temperate estuary

Drones are easy to operate over metres-to-kilometre scales, making them potentially useful to monitor species distributions and habitat use in shallow estuaries with widely varying environmental conditions. To investigate the utility of drones for surveying bonnethead sharks (Sphyrna tiburo) across estuarine environmental gradients, we deployed decoys, fashioned to mimic sharks, in the field. Decoys were placed in two flight areas (0.8 km2 each) in shallow (<2 m) water near Beaufort, N.C., on five days during 2015–2016. Survey flights were conducted using a fixed-wing drone (senseFly eBee) equipped with a digital camera. Images were indexed for combinations of six environmental factors across flights. Images representative of all (N = 36) observed environmental combinations were sent to a group of 15 scientists who were asked to identify sharks in each image. Non-parametric rank-sum comparisons and regression tree analysis on resultant detection probabilities highlighted depth as having the largest, statistically reliable influence on detection probabilities, with decreasing detection probabilities at increased depth. Detection probabilities were higher during midday flights, with notable effects of wind speed and cloud presence also apparent. Our study highlights depth as a first-order factor constraining the temperate estuarine habitats over which drones may reliably quantify sharks (i.e., <0.75 m).