An overview of beach morphodynamic classification along the beaches between Ovari and Kanyakumari,Southern Tamilnadu Coast,India

Beach morphology relates the mutual adjustment between topography and fluid dynamics. The morphological makeup of beach systems is not accidental because the arrangement and association of forms occur in an organized contextual space and time. Since the classification derived by Wright and Short (1983) from the analysis of the evolution in a number of Southern Tamilnadu beach sites, beach systems are comprehended in terms of three-dimensional morphodynamic models that include quantitative parameters (wave breaking height, sediment fall velocity, wave period, and beach slope) and boundary conditions for definable form-processes association (e.g., the presence or absence of bars as well as their types). This has led to the classification of beaches into three main categories relating the beach state observations with the physical forcing (Short, 1999) dissipative, intermediate (from the intermediate–dissipative domain to the intermediate-reflective domain), and reflective modes. The morphodynamic classification of beach types was based on the Wright–Short equations (1984) (dimensionless fall velocity–Dean parameter).     

Placer Deposits of Southern Tamil Nadu Coast, India

Exploration for placer deposits, especially for ilmenites, has been undertaken systematically in the southern coast of Tamil Nadu, India. On the basis of drainage network. Coastal landforms, lithology, and neotectonics, the study area has been grouped into five sectors: Mandapam, Valinokkam, Tuticorin, Manappad, and Kanyakumari. Ilmenites are abundant in Kanyakumari (Max. 53.39 wt%) and Tuticorin (Max. 20.88 wt%) sectors, negligible in Manappad (Max. 0.60 wt%) and Valinokkam (Max. 3.88 wt%) sectors and absent in the Mandapam sector. The abnormal enrichment of ilmenites in the Kanyakumari sector in the absence of any drainage network points to the possibility of a relict source. Literary and scientific evidence corroborates the existence of an Eastern Gondwana land called Lemuria, South of Kanyakumari which was later submerged in the Flandrian transgression. The association of other heavy minerals with ilmenites like overgrown and outgrown zircon supplements the idea of a longer stay of ilmenites in the depositional basin. Ilmenites from these fossil strandlines must have been reworked by the present day coastal processes and deposited in favorable bay-like NE-SW coastal configurations in Kanyakumari-Kuttankuli and Kallar-Vaippar regions under high energy wave conditions. The present study has disclosed the enrichment of ilmenites up to 1 m in depth in the above two zones which can be commercially exploited. The present study also calls for confirming part of the lost continent called Lemuria or Eastern Gondwana by systematic scientific investigations.     

Potential Usage of Remote Sensing Data in Studying the Behaviour of Shore Drift Along Kerala Coast, India

Landsat images were analysed to examine direction, amount and behaviour of long-shore drift and its contribution towards deciding areas vulnerable to coastal erosion and accretion along the coast of Kerala. Two approaches are adopted while utilizing the remote sensing data. Net shore-drift direction is determined firstly by studying various coastal landform indicators and secondly by studying offshore turbidity distribution patterns. Landform indicators study suggest that during the south-west monsoon period, strong southerly currents are eroding protruded sectors and depositing eroded material, though partially, along varying sectors. Whereas during the rest of the year, under the influence of a northerly current, accretion is taking place along retreating sectors which has been reflected in the development of beach ridges. Turbidity pattern distribution exhibited by satellite image suggests that for January and February, long-shore drift is from south to north. The results of the two studies were found to be comparable. It may be concluded that shore-drift direction, which can be determined effectively by remote sensing, is season-dependent and plays a significant role in deciding the areas of coastal erosion and accretion.     

Grain Size Analysis and Depositional Environment Condition along the Beaches between Ovari and Kanyakumari,Southern Tamilnadu Coast,India

Textural analysis is the epicenter of any sedimentological research. Granulometric analyses of unconsolidated sediments are used as an index to decipher the depositional environment. The granulometric analysis display a significant fluctuation in mean size, sorting, skewness, and kurtosis due to the variation in wave energy and the extent of turbulence affecting the beach environment during the crosshore and alongshore movement of sediments. The present study is to document the variation in grain size distribution within foreshore sediments, i.e., between the high water line and the plunge point wherein the sediments are deposited under different wave energy conditions.     

浙江近岸海域表层沉积物中氮的存在形态及其含量的分布特征

运用分相浸取法分析了浙江近岸海域60个站位的表层沉积物(0～2 cm)中各形态氮的含量和分布.研究结果表明,表层沉积物中总氮(TN)含量为214.66～861.44 mg/kg,均值为580.52mg/kg,位于浅水区的长江口、杭州湾和浙江沿岸的TN含量低于东部远岸海域;可转化态氮(TTN)含量只占总氮的3.06%～37.24%,有机态和硫化物结合态氮(OSF-N)是沉积物中可转化态氮的主要赋存形态,非转化态氮(NTN)是浙江近岸海域表层沉积物中的优势形态.各站位沉积物中氮在不同提取相中的含量差异较大,与沉积物的陆源输入、沉积物重金属含量、粒径分布及沉积海域的水动力条件等因素有关.     

Structure and distribution of the benthic macrofauna on a Northwest African sandy beach close to a freshwater river discharge

The effects of the freshwater discharge of the Oued Sebou River on the macroinfauna, was studied on the sandy beach of Mehdia through the analysis of the abiotic parameters and of the macrozoobenthos. In autumn 2002 and spring 2003, three beach sites, each with two transects, localized at 50, 3500 and 5720 m from the river mouth respectively, were studied. Positive correlations were recorded for beach slope and pH whereas negative ones were obtained for organic matter content and salinity at increasing distances from the river mouth. Significant differences between beach sites and seasons occurred for median grain size, organic matter content and pH. For each beach site, mean macroinfauna abundance varied between 30 and 100 ind.·m⁻² and in spring there was a significant correlation between this parameter and the increasing distance from the river mouth. No significant correlation was instead found between species richness and the increasing distance, although the farthest beach site from the mouth had the highest number of species during both seasons. The results indicated the importance of organic matter content and salinity for the macrofaunal abundance whereas the diversity indices were more affected by beach slope and grain size. The results showed that there was no clear spatial trend in compound indices of the macrofauna across the sampled sites and the influence of the river discharge of Sebou River did not seem to be significant and consistent on the macrobenthos of this mesotidal shore. Comparison with microtidal shores revealed the influence of the tidal excursion and swell characteristics on the response of the benthic structures of sandy beaches to discharges of freshwater.     

Nearshore sediment characteristics and formation of mudbanks along the Kerala coast,southwest India

In order to gain insight into the formation dynamics of mudbanks off the Kerala coast of India, extensive surveying of the nearshore bathymetry along with sediment characterization was undertaken. The textural and geotechnical properties of the surficial sediments of a mudbank were determined during pre-monsoon, monsoon, and post-monsoon periods. The mudbank sediments were clayey silts with high water and organic carbon contents, high Atterberg limits, and low bulk density, and therefore very susceptible to entrainment. During the monsoon, the mudbank regime was characterised by enhanced turbidity and a benthic fluff layer, triggered by the increasing swell of the early monsoon period. Re-suspension exposed a more consolidated, previously sub-bottom, layer which exhibited lower water content and greater shear strength than the pre-monsoon seabed. Texturally, the monsoon seabed was similar to the pre-monsoon seabed, with the same modal grain size, but the proportions of sand and coarse silt increased nearshore, while the proportions of fine and very fine silt increased offshore. There was a seaward-fining textural gradient at all times, but this became pronounced during the monsoon period. Paradoxically, the monsoonal seabed displayed greatly reduced wet bulk density. It is hypothesized that this was due to the presence of gas, probably methane, in the sediments (while the pre-monsoon sediments were fully saturated, the monsoon sediments were only 83% saturated). We speculate that the gas was forced into the surficial sediments either by wave pumping (at the onset of the monsoon) or by seaward-flowing subbottom freshwater (derived from monsoonal rains). With the waning of the monsoon, the benthic fluid mud layer rapidly disappeared and the seabed returned to its pre-monsoon state as suspended sediments were redeposited. The mudbank regime is therefore essentially an in situ phenomenon. It is suggested that the mudbanks are palimpsest, marshy, lagoonal deposits, rich in organic matter and derived gas, that were submerged after a marine transgression. The surficial sediment is annually entrained during the monsoon, but erosion is limited by the formation of the benthic fluid mud layer, which attenuates wave generated turbulence. Although some fine sediment disperses alongshore and offshore, most is returned to the seabed as the monsoon declines.     

Spatial distribution and geochemistry of the nearshore gas seepages and their implications to natural gas migration in the Yinggehai Basin,offshore South China Sea

About 120 gas seepage vents were documented along the west and southwest coast of the Hainan Island, South China Sea, in water depths usually less than 50 m. The principal seepage areas include the Lingtou Promontory, the Yinggehai Rivulet Mouth, Yazhou Bay, the Nanshan Promontory and the Tianya Promontory. They occur along three major zones, reflecting the control by faults and lateral conduits within the basement. It is estimated that the total gas emission from these seepage vents is 294–956 m³/year. The seepage gases are characterized by a high CH₄ content (76%), heavy δ¹³C₁ values (−38 to −33‰) and high C₁/C_1–5 ratios (0.95–1.0), resembling the thermogenic gases from the diapiric gas fields of the Yinggehai Basin. Hydrocarbon–source correlation shows that the hydrocarbons in the sediments from seepage areas can be correlated with the deeply buried Miocene source rocks and sandstone reservoirs in the central depression. The 2D basin modeling results based on a section from the source rock center to the gas seepage sites indicate that the gas-bearing fluids migrated from the source rocks upward through faults or weak zones encompassed by shale diapirism or in up-dip direction along the sandstone-rich strata of Huangliu Formation to arrive to seabed and form the nearshore gas seepages. It is suggested that the seepage gases are sourced from the Miocene source rocks in the central depression of the Yinggehai Basin. This migration model implies that the eastern slope zone between the gas source area of the central depression and the seepage zone is also favorable place for gas accumulation.     

台湾海峡南部及闽南沿岸的鲸豚记录

1991～1999年,在台湾海峡南部和闽南沿海获52只鲸豚标本,1种须鲸、5种齿鲸.已对其中3种海豚进行过专题报道.本文对另3种,即花斑原海豚、伪虎鲸和鲲鲸进行研究.给出了这3种的体表颜色、大小、性别、齿式,各部位测量记录;以及心、肺等内脏的重量.     

Origin and geochemistry of surface sediments in the mud deposit area offshore the Shandong Peninsula,China

The waters offshore the Shandong Peninsula separate the North Yellow Sea from the South Yellow Sea, and receive a large amount of terrestrial material from Chin...     

多源卫星高度计海浪资料在中国近海的验证及应用

Studies of offshore wave climate based on satellite altimeter significant wave height(SWH) have widespread application value. This study used a calibrated multi-altimeter SWH dataset to investigate the wave climate characteristics in the offshore areas of China. First, the SWH measurements from 28 buoys located in China's coastal seas were compared with an Ifremer calibrated altimeter SWH dataset. Although the altimeter dataset tended to slightly overestimate SWH, it was in good agreement with the in situ data in general. The correlation coefficient was 0.97 and the root-mean-square(RMS) of differences was 0.30 m. The validation results showed a slight difference in different areas. The correlation coefficient was the maximum(0.97) and the RMS difference was the minimum(0.28 m) in the area from the East China Sea to the north of the South China Sea.The correlation coefficient of approximately 0.95 was relatively low in the seas off the Changjiang(Yangtze River) Estuary. The RMS difference was the maximum(0.32 m) in the seas off the Changjiang Estuary and was0.30 m in the Bohai Sea and the Yellow Sea. Based on the above evidence, it is confirmed that the multialtimeter wave data are reliable in China's offshore areas. Then, the characteristics of the wave field, including the frequency of huge waves and the multi-year return SWH in China's offshore seas were analyzed using the23-year altimeter wave dataset. The 23-year mean SWH generally ranged from 0.6–2.2 m. The greatest SWH appeared in the southeast of the China East Sea, the Taiwan Strait and the northeast of the South China Sea.Obvious seasonal variation of SWH was found in most areas; SWH was greater in winter and autumn than in summer and spring. Extreme waves greater than 4 m in height mainly occurred in the following areas: the southeast of the East China Sea, the south of the Ryukyu Islands, the east of Taiwan-Luzon Island, and the Dongsha Islands extending to the Zhongsha Islands, and the frequency of extreme waves was 3%–6%. Extreme waves occurred most frequently in autumn and rarely in spring. The 100-year return wave height was greatest from the northwest Pacific seas extending to southeast of the Ryukyu Islands(9–12 m), and the northeast of the South China Sea and the East China Sea had the second largest wave heights(7–11 m). For inshore areas, the100-year return wave height was the greatest in the waters off the east coast of Guangdong Province and the south coast of Zhejiang Province(7–8 m), whereas it was at a minimum in the area from the Changjiang Estuary to the Bohai Sea(4–6 m). An investigation of sampling effects indicates that when using the 1°×1°grid dataset, although the combination of nine altimeters obviously enhanced the time and space coverage of sampling, the accuracy of statistical results, particularly extreme values obtained from the dataset, still suffered from undersampling problems because the time sampling percent in each 1°×1°grid cell was always less than33%.     

Temporospatial dynamics and public health significance of bacterial flora identified on a major leatherback turtle (Dermochelys coriacea) nesting beach in the Southern Caribbean

Grande Riviere beach, on the island of Trinidad, supports the largest nesting population of leatherback turtles in the Caribbean region. Throughout the nesting season, nests are naturally disturbed by newly nesting females, resulting in egg breakage and loss of some nest viability. This environment is ideal for the growth and proliferation of microorganisms. The range of bacterial flora present in beach sand and egg shells was examined, with emphasis on bacteria that may pose a threat to public and animal health. The extent to which the bacterial load and genera on the beach changed throughout the season was also assessed. Twenty‐five genera were identified, with Pseudomonas spp. found to be the most predominant environmental bacteria. Four genera identified possess zoonotic potential, while five additional genera are known to be of public and animal health significance. Distinct shifts in the density and distribution of bacteria were observed along the beach from early to peak nesting season. Shifts were seen across heavily traversed zones, thus highlighting the potential exposure threats posed to beach visitors and animals alike. Further studies aimed at speciating this population of bacteria, as well as isolating potential fungal pathogens may mitigate this threat. Identification of bacterial agents that are specifically pathogenic to leatherback turtles, turtle eggs, hatchlings and those who may interact with these animals will serve to enhance and guide efforts to better conserve this species and protect the health of all who visit this ecologically significant site.     

三亚大东海砂质潮间带小型底栖生物的时空分布及影响因素

于2015年和2016年对三亚大东海砂质潮间带进行了季节性的调查,对小型底栖生物及其所处的沉积环境进行了研究,探讨了小型底栖生物的丰度、生物量和群落的时空变化及其与环境变量的关系。共鉴定小型底栖生物类群11个,优势类群为海洋线虫类与桡足类(二者占总丰度83.13%);小型底栖生物年平均丰度为(595.77±442.72)ind·10cm~(–2),小型底栖生物2015年12月的平均丰度为(768.70±533.22) ind·10cm~(–2), 2016年6月平均丰度为(422.85±236.42) ind·10cm~(–2)。丰度分布呈现明显的季节和潮区差异。相关分析结果表明pH、偏态系数与小型底栖生物的丰度呈极显著的负相关,分选系数、中值粒径与之呈极显著的正相关性。小型底栖生物的丰度随季节变化趋势为冬季夏季。食物丰度、溶氧量升高与沉积物粒径的变化是冬季桡足类丰度的大幅增加的主要原因。TWO-WAY ANOVA与ANOSIM结果显示,潮带对小型底栖生物丰度和群落结构的影响在冬季显著。SIMPER分析结果显示,此差异主要来源为桡足类和线虫类。BIOENV分析结果显示,溶氧量和分选系数的组合最能解释这种差异。这一结果可能是由于高、中潮带的人为干扰与砂滩的清理作用导致。夏季潮带间丰度与群落结构差异不显著,pH、盐度、叶绿素含量是影响其分布的主要原因。研究结果可为砂质滩小型底栖生物的研究提供基础数据,也可为全球气候变化背景下砂质潮间带的保护、开发和利用提供科学依据。     

Fan delta development and processes offshore a seasonal river in a seismically active region, NW Gulf of Corinth

High-resolution geophysical surveys (seismic, side-scan sonar) offshore of the Eratini River, a seasonally flowing river in the NW Gulf of Corinth, Greece, revealed a small fan delta with a variety of bottom features (blocky deposits, chutes and sediment instabilities). Considering the relatively small size of this river, however, these features could not be explained as being produced solely by river flow processes. Based on morphological features, the fan delta can be subdivided into a high- and a low-energy area. Sedimentation processes in the fan delta are associated with flood-derived sediment input, hyperpycnal flows which erode the fan surface, mud settling from suspension plumes, shelf sedimentation and sediment failures. The observed blocky deposits are considered to be the result of earthquake-induced mass flows in 1965 and 1995, whereas the chutes would be produced both by erosive mass flows and by hyperpycnal currents. The bulk block sediment volume has probably resulted from the 1965 earthquake. The 1965 evacuation zone and the related chutes were buried by the prograding fan delta. The main causative factor triggering the observed sediment instabilities is considered to be liquefaction, which is caused by (1) frequent earthquake-induced cyclic loading and (2) low sediment shear strengths created by rapid deposition during floods, in both cases associated with high pore-water pressures.     

Organic carbon and nitrogen in the northern California current system: comparison of offshore, river plume, and coastally upwelled waters

During the first year of the Northeast Pacific GLOBEC program we examined the spatial distributions of dissolved and particulate organic carbon and nitrogen in the surface waters off the Oregon and Washington coasts of North America. Eleven east–west transects were sampled from nearshore waters to 190 km offshore. Hydrographic data and the distribution of inorganic nutrients were used to characterize three distinct water sources: oligotrophic offshore water, the Columbia River plume, and the coastal upwelling region inshore of the California Current. Warm, high salinity offshore water had very low levels of inorganic nutrients, particulate organic carbon (POC) and dissolved organic carbon (DOC). Warm, low salinity water in the Columbia River plume was relatively low in nitrate, but showed a strong negative correlation between salinity and silicate. The river plume water had the highest levels of total organic carbon (TOC) (up to 180 μM) and DOC (up to 150 μM) observed anywhere in the sampling area. Cold, high salinity coastal waters had high nutrient levels, moderate to high levels of POC and particulate organic nitrogen (PON), and low to moderate levels of DOC and dissolved organic nitrogen (DON). Each of these regions has characteristic C:N ratios for particulate and dissolved organic material. The results are compared to concentrations and partitioning of particulate and dissolved organic carbon and nitrogen in other regions of the North Pacific and North Atlantic Oceans.     

广东流沙湾近岸和离岸育珠海区养殖环境的调查

2011年2月~2012年1月对广东流沙湾近岸和离岸育珠海区6个航次11个指标进行了调查。结果表明,近岸和离岸育珠海区水温、透明度、盐度和pH周年变化范围相似,水温呈现明显季节性变化,透明度、盐度和pH周年比较稳定,揭示目前流沙湾近岸和离岸育珠海区水流交换较好。近岸和离岸育珠海区叶绿素a和浮游植物细胞密度具有类似的周年变化规律,夏秋季高于冬春季。在4~7月份和9~10月份,近岸海区叶绿素a和浮游植物细胞密度呈现显著递增趋势,而10月份之后,显著递减。2~4月份,以及12月份至次年1月份,叶绿素a值和浮游植物细胞密度均较低。5~11月份,离岸海区叶绿素a和浮游植物细胞密度均显著低于近岸海区。近岸和离岸育珠海区COD含量周年变化范围分别为0.2~0.7 mg/L和0.1~0.8 mg/L,均达到国家一类水质标准。近岸海区和离岸海区无机氮(inorganic nitrogen,IN)含量周年变化范围分别为1.9~8.0μmol/L和3.4~8.7μmol/L,均达到国家第二类水质标准。两个海区IN含量的周年变化趋势与叶绿素a值和浮游植物细胞密度的周年变化趋势相反,冬春季高于夏秋季。无机磷(inorganic phosphorus,IP)在流沙湾近岸和离岸海区含量具有相似的周年变化趋势,其季节性变化与无机氮恰好相反,表现为夏、秋季含量高于冬、春季。6~8月份,近岸海区IP超出国家二类水质标准分别达44.67%、96.33%和210%,离岸海区在相同的月份超出国家二类标准分别达75.67%、86%和230.67%。揭示在夏、秋季节应合理控制贝类养殖密度和流沙湾周边环境的污染。     

Provenance Signature of Pre-Cambrian and Mesozoic Rocks in the Nearshore Placers of Konkan,Central West Coast of India

Heavy mineral studies of the nearshore placer deposits of the Konkan Coast reveal a dominant assemblage comprised of garnet and kyanite along with other accessory minerals like epidote, olivine and rutile. The heavy mineral assemblage of the study region shows a characteristic suite of 17 types of heavy minerals. Their abundance shows hardly any drastic variation in the four bays studied. Overwhelming presence of minerals like garnet and kyanite in the studied four bays points to the source as metamorphic rocks. The presence of etched garnets, overgrown zircons and etched kyanites corroborate the recycling of paleo-sediments into the bay. Characterization of opaques under the microscope also corroborates the influence of a metamorphic source, rather than the adjoining basaltic rocks. However, the absence of metamorphic rocks in the hinterland suggests the possibility of deposition of sediments predominantly from offshore. Factor analysis results also corroborate the overwhelming influence of metamorphic rocks in the present study region rather than the abutting basalts.     

Development policies,state interventions and struggles for livelihood rights in coastal communities in Kerala,India: A case study of the Cochin clam fishery

One of the major dilemmas of using rural commons for industrial uses in developing countries relates to the failure of the state to evolve consensus on allocating property rights to local communities and modern enterprises in a manner that sustains livelihoods and ecosystems. While traditional coastal communities enforce customary rights for fishing and mineral mining, the state sometimes reallocates traditional fishing territories to commercial mining to facilitate rapid industrialization. Communities oppose such transfers because of the negative impacts of commercial dredging on traditional fishing and ecosystems. Based on detailed field level surveys conducted in 2004, this paper describes how rural island communities along Cochin estuary expressed their opposition to the transfer of clam-mining rights to industries by democratic social mobilization. Counter moves were collectively organized by modern enterprises and trade unions which had the support of the state. However, major political parties retreated from conflict management, leaving the matter in a state of flux. This paper suggests that the state must recognize traditional livelihood rights of communities if it is to resolve conflicts and ensure the sustainable and equitable use of natural resources.     

Differences in perception and reaction of tourist groups to beach marine debris that can influence a loss of tourism revenue in coastal areas

Marine debris is the most conspicuous pollutant that makes beaches aesthetically unappealing to users. The perceptions and reactions of beach users to stranded litter were compared between second-home owners and users (SHOU) and non-recurrent tourists (T). A questionnaire was applied to obtain socio-economic characteristics; assessment of the overall beach quality and perception of beach litter pollution (perception); hypothetical scenarios of marine litter pollution and deterrence (reaction); and potential alternative destinations in the case of deterrence (economic effect). Questionnaires (n = 319) were applied at two Brazilian subtropical beaches, with different physiographical settings (Pontal do Sul, PS, estuarine beach; Ipanema, I, open-ocean beach). Beach users’ groups differed regarding daily expenses (T > SHOU), period of permanence per trip (SHOU > T) and trip frequency (SHOU > T). The open-ocean beach (I) was rated the worst regarding overall beach quality. Marine debris generation was mainly attributed to local “beach users”, in the open-ocean beach (I). “Marine” (or non-local) sources were four times more frequently cited in the estuarine beach (PS). Perception on actual litter pollution and litter deterrence scenarios, did not vary between beaches or groups. More than 85% of beachgoers would avoid a beach visit if a worst scenario (> 15items/m²) occurred and most users would choose a neighboring state beach destination. Stranded litter may potentially reduce local tourism income by 39.1%, representing losses of up to US$ 8.5 million per year. These figures are proxies to support the trade-off local authority's make between investments to prevent/remove beach litter and the potential reduction in income from a tourist destination change.