Factors driving the seasonal distribution of planktonic and epiphytic ciliates in a eutrophicated Mediterranean Lagoon     

Amel Dhib  Mounir Ben Brahim  Boutheina Ziadi  Fourat Akrout  Souad Turki  Lotfi Aleya 《Marine pollution bulletin》2013

We studied the distribution of planktonic and epiphytic ciliates coupled with environmental factors and microalgae abundance at five stations in Ghar El Melh Lagoon (Tunisia). Planktonic ciliates were monitored for a year and epiphytic ciliates were sampled during summer 2011 in concordance with the proliferation of the seagrass Ruppia cirrhosa. Ciliate assemblage was largely dominated by Spirotrichea followed respectively by Tintinnida of and Strombidiida. No significant difference was found in the distribution of ciliate species among the stations. Redundancy analysis indicates that abiotic factors (temperature and nutriments) have a significant effect on the dynamics of certain ciliates. For epiphytic ciliates, 4 species were identified: Tintinnopsis campanula, Aspidisca sp., Strombidium acutum and Amphorides amphora. Based on PERMANOVA analyses, ciliates exhibit significant correlations among months and stations. According to ACP, epiphyte distribution follows roughly those of R. cirrhosa and pH. Significant correlations were found between harmful dinoflagellates and both planktonic and epiphytic ciliates.  相似文献   

Hydrology of Okarito Lagoon and the inferred effects of selective logging in Okarito Forest     

J. M. Macpherson 《新西兰海洋与淡水研究杂志》2013,47(1):25-39

Okarito Lagoon (43° 11′S, 170° 14′E) is a small (20 km²) shore‐parallel, predominantly subtidal estuary, deepest near the landward end, and linked to the sea by two subtidal channels incised through shallow subtidal and intertidal flats which occupy the southern third of the lagoon. Tides at sea vary from 2.1m (spring) to 1.2 m (neap), but in the lagoon the tidal range is constant through the lunar cycle and varies from 0.80 m at the entrance to 0.17 m in the upper lagoon. Tidal water level and flow asymmetries in the subtidal channels are separated by a 1.7 h phase difference. Variations in the net discharge through the inlet result from changing flow cross‐sections rather than from variations in current velocities. Both the tidal‐averaged volume and the tidal compartment of the lagoon vary through the lunar cycle, from maxima at spring tides to minima at neap tides.

Freshwater inflows vary from less than 11 m³.s^‐1 to more than 750 m³.s^‐1. During storms, water level in the lagoon rises rapidly by 2–3 m, then declines to normal over several days. Three water masses, two with salinity and turbidity largely controlled by antecedent rainfall, normally occur in the lagoon. Suspended sediment concentrations in both freshwater inflows and lagoon waters are normally low but increase during floods. Most sediment is supplied by the Waitangi‐taona River or by erosion of tidal channel margins. The lagoon is floored with organic‐rich mud and sandy mud, deposited predominantly from suspension. Surface sediment is consistently muddier than subsurface sediment, probably reflecting an increase in the mud supply since diversion of the Waitangi‐taona River in 1967.

Comparisons of the estimated sediment yield and water inflow effects of the 1967 river diversion with short‐term observations during selective logging suggest that the effects of logging on sediment yield, water balance of the lagoon, and dissolved solids inputs will be small compared with changes caused by diversion of the Waitangi‐taona River.  相似文献   

Dynamics of water exchange and salt flux in the Macuse Estuary,central Mozambique,southern Africa     

《African Journal of Marine Science》2013,35(2):203-208

The Siberian subspecies of the red knot Calidris canutus canutus spends the non-breeding season largely in West Africa (Mauritania and Guinea Bissau), where approximately half a million occurred in the 1980s. It was a rarely seen in southern Africa in the early part of the 20th century, but there were about 12 500 in the 1970s and 1980s. The main sites were Langebaan Lagoon, Berg River Estuary, Olifants River Estuary (South Africa) and Walvis Bay Lagoon (Namibia). There was a decline in the number of red knots at Langebaan Lagoon in the 1990s, to around 20% of the number that occurred there in the 1980s. Numbers remained low in the 2000s. In addition, the percentage that remained during the austral winter (the breeding season in the Arctic) declined, and there was none during the period 2001–2009. This suggested that first-year birds, which largely comprise the austral winter population, were no longer travelling to southern Africa. The decline in numbers coincided with the decline in West Africa, but it was disproportionately larger in southern Africa. The observed pattern of change is consistent with a buffer effect, whereby southern Africa represents an extension to the range to less suitable habitat (requiring a 6 000 km extension to the migration) when the population size and competition is high in the main localities in West Africa. We are probably now witnessing the gradual decline in the number of adult birds who are fixed in their use of southern Africa as their non-breeding quarters.  相似文献   

Effect of coastal waves on sea level in Óbidos Lagoon,Portugal     

Madalena S. Malhadas  Paulo C. Leitão  Adélio Silva  Ramiro Neves 《Continental Shelf Research》2009

This study reports the role of waves, tide, wind and freshwater discharges over the sea level in Óbidos Lagoon, a coastal system connected to the sea through a narrow and shallow mobile inlet. To address the hydrodynamic features of this coastal system, the relative importance of different physical forcings were evaluated. For this purpose, observations together with realistic and idealized numerical modeling were used. Both model and measurements show that the lagoon sea level remains above offshore sea level during storm wave periods. Hence, a simplified inlet-lagoon idealized model was described through mathematical expressions, to understand and highlight the physical processes responsible for sea-level elevation.  相似文献   

Relationships between hydrodynamic parameters and grain size in two contrasting transitional environments: The Lagoons of Venice and Cabras, Italy   总被引：3，自引：0，他引：3  

E. Molinaroli  S. Guerzoni  G. De Falco  A. Sarretta  A. Cucco  S. Como  S. Simeone  A. Perilli  P. Magni   《Sedimentary Geology》2009,219(1-4):196-207

A comparison was made of shallow water sediments from the Lagoon of Venice (LV) and the Lagoon of Cabras (LC), comparing depositional environments and exploring the relationships between hydrodynamics and sedimentological parameters. The two water bodies are very different in size (LV: 360 km²; LC: 22 km²), and the sediments predominantly consist of silty-clay (LV: Mz ≈ 26 μm; LC: Mz ≈ 6 μm). However, there are large differences between the two lagoons with respect to sand (LV: mean 19%; LC: mean ~ 3%) and clay (LV: mean 20%; LC: mean 45%) contents. The Lagoon of Venice (mean depth ~ 1 m) can be considered a tidal basin, whereas the Lagoon of Cabras (mean depth ~ 2 m) has the character of a coastal lake in which wind is the main hydrodynamic forcing factor. A comparison of sediment grain-size distributions with water circulation patterns in different parts of the lagoons highlighted some interesting differences. Grain-size analyses of samples reveal a deficiency of particles around 8 μm in the LC, which is interpreted as reflecting the transition between cohesive flocs/aggregates and non-cohesive coarser silt particles, while the transition limit in the LV is ~ 20 μm. Thus, particles are cohesive below 8 μm in the LC and below ~ 20 μm in the LV. This is probably because of the differences in the clay/silt ratio, which is much lower in the LV (~ 0.3) than in LC (~ 1), conferring a “silt-dominated network structure” on most of the LV sediments.The hydrographical data used were root mean square velocity (RMSV) and water residence time (WRT), computed under the main forcing conditions. The results show a general correlation between RMSV and sortable silt in the LC, and between RMSV and coarser sediments (63–105 μm) in the LV. Some significant differences between the lagoons were detected in the degree of correlation between WRT and grain size. Root mean square velocity (~ 7 cm s^− 1 in the LV and ~ 3 cm s^− 1 in the LC) was a greater forcing factor in the LC than in the LV. Conversely, WRT, which is on average ~ 16 days in the LV and ~ 19 days in the LC, has more influence in the LV. This study highlights the usefulness of comparing environments with different hydrodynamic energies, e.g., tidal and/or wind-driven currents, to elucidate and thereby improve our understanding of the processes governing the spatial distribution of sedimentological features, the transport mechanisms of sediments, and the relationship between them. The results demonstrate that the approach outlined in this study has the potential to provide a universal hydro-sedimentological classification scheme.  相似文献   

Occurrence and levels of polybrominated diphenyl ethers (PBDEs) in recent sediments and marine organisms from Xiamen offshore areas, China   总被引：3，自引：0，他引：3  

Qingzhao Li  Changzhou Yan  Zhuanxi Luo 《Marine pollution bulletin》2010,60(3):464-4627

Surface sediments and porewater from 12 sites within Xiamen offshore areas and organisms from a heavily contaminated site Yuandang Lagoon were sampled and analyzed for eight polybrominated diphenyl ethers (PBDEs) congeners (-28, -47, -99, -100, -153, -154, -183 and -209). The total concentrations of eight PBDEs (∑₈PBDEs) and BDE-209 in sediments ranged from 0.27 to 76.54 ng/g with an average of 16.31 ng/g and from 0.10 to 70.11 ng/g with an average of 14.94 ng/g, respectively. Concentrations of ∑₈PBDEs in porewater ranged from 2.5 to 34.1 ng/L, with a mean value of 15.3 ng/L. In this study, the partition coefficients (log ) of PBDE congeners (without -209) were significantly correlated with their octanol-water partition coefficients (log K_OW) (r² = 0.74, P < 0.01). ∑₈PBDE concentrations ranged from 0.33 to 1.26 ng/g (lipid weight) in marine organisms, and PBDE congener patterns were significantly different between fish and clam, crab.  相似文献   

Evaluating the source and seasonality of submarine groundwater discharge using a radon-222 pore water transport model   总被引：1，自引：0，他引：1  

Christopher G. Smith  Jaye E. Cable  Jonathan B. Martin  Moutusi Roy 《Earth and Planetary Science Letters》2008,273(3-4):312-322

Pore water radon (²²²Rn) distributions from Indian River Lagoon, Florida, are characterized by three zones: a lower zone where pore water ²²²Rn and sediment-bound radium (²²⁶Ra) are in equilibrium and concentration gradients are vertical; a middle zone where ²²²Rn is in excess of sediment-bound ²²⁶Ra and concentration gradients are concave-downward; and an upper zone where ²²²Rn concentration gradients are nearly vertical. These ²²²Rn data are simulated in a one-dimensional numerical model including advection, diffusion, and non-local exchange to estimate magnitudes of submarine groundwater discharge components (fresh or marine). The numerical model estimates three parameters, fresh groundwater seepage velocity, irrigation intensity, and irrigation attenuation, using two Monte Carlo (MC) simulations that (1) ensure the minimization algorithm converges on a global minimum of the merit function and the parameter estimates are consistent within this global minimum, and (2) provide 90% confidence intervals on the parameter estimates using the measured ²²²Rn activity variance. Model estimates of seepage velocities and discharge agree with previous estimates obtained from numerical groundwater flow models and seepage meter measurements and show the fresh water component decreases offshore and varies seasonally by a factor of nine or less. Comparison between the discharge estimates and precipitation patterns suggests a mean residence time in unsaturated and saturated zones on the order of 5 to 7 months. Irrigation rates generally decrease offshore for all sampling periods. The mean irrigation rate is approximately three times greater than the mean seepage velocity although the ranges of irrigation rates and seepage velocities are the same. Possible mechanisms for irrigation include density-driven convection, wave pumping, and bio-irrigation. Simulation of both advection and irrigation allows the separation of submarine groundwater discharge into fresh groundwater and (re)circulated lagoon water.  相似文献   

Effects of reef morphology variations on wave processes over fringing reefs     

《Applied Ocean Research》2019

Many low-lying tropical and sub-tropical atolls fringed by coral reefs are susceptible to coastal inundation during extreme wave events. Previous studies have shown that the infragravity (IG) wave is the dominant component of shoreline run-up compared to the sea and swell (SS) wave and the wave-induced setup. To better understand both the SS and IG wave dynamics over a fringing reef with various morphologies, a series of laboratory experiments were conducted in a wave flume based on an idealized fringing reef profile. The shoreline responses of waves to different reef morphologies with/without the reef crest, the lagoon and the reef surface roughness were examined. IG wave resonance on the reef flat was identified by a spectral analysis of the shoreline wave records. Subsequently, a numerical model based on the Boussinesq equations was validated by the experimental data. The model was then applied to investigate the impacts of varying reef morphologic features (fore-reef slope, reef-crest width, lagoon width, and reef roughness coefficient) on the shoreline wave motions.  相似文献   

秦皇岛七里海潟湖湿地非繁殖期鸟类多样性          下载免费PDF全文

戴宇飞  吴福星  赵丽媛  雷威  曾千慧  王先艳 《应用海洋学学报》2019,38(4):569-577

2016年9月至2017年4月,采用样线法和可变大小样方法相结合,对七里海潟湖湿地非繁殖期鸟类进行了调查研究。调查共记录到鸟类13目27科60种,其中雀形目鸟类10科14种,占物种总数量的23. 33%;非雀形目鸟类17科46种,占物种总数量的76. 67%。湿地水鸟数量占全部鸟类总数量的95. 11%,水鸟类群主要为鸥类、雁鸭类、鸻鹬类和鹭类。鸟类居留类型主要为旅鸟和夏候鸟,分别占物种总数量的35. 00%和33. 33%。鸟类区系方面,以古北界鸟类和广布种鸟类为主,分别占物种总数量的63. 33%和26. 67%。经统计,鸟类多样性指数、均匀度指数和丰富度指数的平均值分别是1. 86、0. 39和2. 31。七里海潟湖湿地位于东亚—澳大利西亚迁徙路线上,是重要的鸟类迁徙停歇地和觅食地,鸟类尤其是水鸟资源丰富,应当受到关注和保护。  相似文献   

A regional water balance indicator inferred from satellite images of an Andean endorheic basin in central-western Argentina     

Lucas O. Bianchi  Juan Antonio Rivera  Facundo Rojas  Mauro Britos Navarro  Ricardo Villalba 《水文科学杂志》2017,62(4):533-545

In the Central Andes of Argentina (30–37°S), snowmelt is the main source of freshwater, an essential natural resource for ~2.2 million people in the adjacent arid lowlands. In this region, Laguna Llancanelo collects the water inputs from the Malargüe endorheic basin. Previous studies concerning the annual and intra-annual variations of this lagoon and its relationship with regional climate are rare. We obtained a monthly record for the Laguna Llancanelo area (LLA, 1984–2013) using the modified normalized difference water index derived from Landsat images. Monthly LLA ranges between 35 km² and 411 km² and is significantly related to variations of the Río Malargüe, the main snow-fed tributary to the lagoon. There is no long-term relationship between LLA and local rainfall, but rapid increases in LLA result from heavy rainfall around the lagoon. Conversely, rapid reductions in LLA encompass periods with both reduced discharge from the Río Malargüe and low local rainfall. The LLA integrates moisture of both Pacific (snowfall in the upper Andes) and Atlantic (lowland rainfall) origins; therefore, we propose using LLA as an indicator of regional water balance.  相似文献