Sea Bottom Environment Research Articles

EVIDENCE OF MASS MORTALITY OF THE LONG-LIVED BIVALVE MERCENARIA STIMPSONI CAUSED BY A CATASTROPHIC TSUNAMI

ABSTRACTTsunamis are huge disasters that can significantly damage benthic organisms and the sea-bottom environment in coastal areas. It is of great ecological importance to understand how benthic ecosystems respond to such destructive forces and how individual species are affected. Investigating the effect of such disasters on animals that are seldom caught alive is particularly difficult. Bivalve mollusks are especially suitable for investigating how a tsunami affects coastal benthic species because they preserve an environmental record in their shells that can be extended back in time by crossdating the records of multiple individuals. Here we studied dead shells of Mercenaria stimpsoni, a long-lived clam, and precisely determined the time of death by using nuclear bomb–induced radiocarbon (bomb-14C) and by counting annual growth increments. First, a quasi-continuous, regional bomb-14C record was created by analyzing the shells of 6 live-caught M. stimpsoni individuals. Then 27 dead shells collected from the seafloor of Funakoshi Bay were 14C-dated and analyzed. The results showed that the huge tsunami that struck northeastern Japan on 11 March 2011 caused mass mortality of this bivalve in Funakoshi Bay. Nine of the 27 clams died during the March 2011 tsunami, probably by starvation after burial by tsunami deposits or exposure above the seafloor as a result of sediment liquefaction during the earthquake. The dating method used in this study can help us understand how long-lived marine organisms with low population density are affected by huge natural disasters such as a tsunami.

Benthic Foraminiferal Response to the Millennial-Scale Variations in Monsoon-Driven Productivity and Deep-Water Oxygenation in the Western Bay of Bengal During the Last 45 ka

In this study, we presented a high-resolution benthic foraminiferal assemblage record from the western Bay of Bengal (BoB) (off Krishna–Godavari Basin) showing millennial-scale variations during the last 45 ka. We studied temporal variations in benthic foraminiferal assemblages (relative abundances of ecologically sensitive groups/species, microhabitat categories, and morphogroups) to infer past changes in sea bottom environment and to understand how monsoon induced primary productivity-driven organic matter export flux and externally sourced deep-water masses impacted the deep-sea environment at the core site. Our records reveal a strong coupling between surface productivity and benthic environment on glacial/interglacial and millennial scale in concert with Northern Hemisphere climate events. Faunal data suggest a relatively oxic environment when the organic matter flux to the sea floor was low due to low primary production during intensified summer monsoon attributing surface water stratification and less nutrient availability in the mixed layer. Furthermore, records of oxygen-sensitive benthic taxa (low-oxygen vs. high-oxygen benthics) indicate that changes in deep-water circulation combined with the primary productivity-driven organic matter flux modulated the sea bottom oxygen condition over the last 45 ka. We suggest that the bottom water at the core site was well-ventilated during the Holocene (except for the period since 3 ka) compared with the late glacial period. At the millennial timescale, our faunal proxy records suggest relatively oxygen-poor condition at the sea floor during the intervals corresponding to the cold stadials and North Atlantic Heinrich events (H1, H2, H3, and H4) compared with the Dansgaard/Oeschger (D-O) warm interstadials. The study further reveals oxygen-poor bottom waters during the last glacial maximum (LGM, 19–22 ka) which is more pronounced during 21–22 ka. A major shift in sea bottom condition from an oxygenated bottom water during the warm Bølling–Allerød (B/A) (between 13 and 15 ka) to the oxygen-depleted condition during the cold Younger Dryas (YD) period (between 10.5 and 13 ka) is noticed. It is likely that the enhanced inflow of North Atlantic Deep Water (NADW) to BoB would have ventilated bottom waters at the core site during the Holocene, B/A event, and probably during the D-O interstadials of marine isotope stage (MIS) 3.

Environmental characterization of a dredging disposal site on the continental shelf of Espírito Santo, Brazil

Dredge material placement is among the major problems in coastal management. Sedimentation caused by dredge-spoil disposal presents a series of impacts, including the burial of benthos and the suffocation of filter-feeding benthic organisms. To minimize dredging impacts, studies in dredging disposal sites shall be performed to allow better approaches to adverse ecological risks. The goal of the present study was to map the sea bottom environment of a potential dredge disposal site by performing its geomorphology and ecology characterization, in the continental shelf of Espirito Santo state. Acoustic images were obtained using side scan sonar to characterize sediment texture and the geometry of deposits, along with a bathymetric survey. Additionally, underwater footage provided images and the description of the biota communities. The bathymetric survey revealed a relatively plain and homogenous bottom, with the presence of a paleochannel. Smooth elevations, with approximately 0.50m high, were found and characterized as calcareous biogenic concretions, among benthic and nektonic organisms. The organisms revealed a heterogeneous composition and a scattered distribution throughout the sampling stations, with the presence of a threatened species.

Microfacies analysis of the Lower-Middle Ordovician succession at Xiangshuidong, southwestern Hubei Province, and the drowning and shelf-ramp transition of a carbonate platform in the Yangtze region

During the Early-Middle Ordovician, the Yangtze Platform in South China was drowned, as indicated by the replacement of pure grey grainstones and packstones of the Hunghuayuan Formation by purple red, argillaceous limestone of the Zitai Formation and correlative units, which are mixed siliciclastic and carbonate deposits. The Xiangshuidong Section, located in Songzi City, southwestern Hubei Province, was selected to study the process in detail. Cluster analysis of point-count groups of the Hunghuayuan and the Zitai formations, indicates that the former contains six microfacies: MF-1 peloidal grainstone, MF-2 thrombolitic grainstone, MF-3 oolitic grainstone, MF-4 bioclastic grainstone, MF-5 lithoclastic grainstone, MF-6 interreef bioclastic grain-packstone, indicating a shelf setting before drowning, while the latter contains seven microfacies: MF-7 bioclastic grainstone, MF-8 bioclastic grain- to packstone, MF-9 bioclastic packstone, MF-10 bioclastic wackestone, MF-11 argillaceous bioclastic wackestone, MF-12 open-marine bioclastic wackestone, MF-13 calcimudstone, indicating the ramp setting during and after the drowning. The drowning was gradual and fluctuating, starting as a marginal shoal, through the inner ramp, and becoming a stable ramp setting. This drowning is mainly attributed to a global sea-level rise, and an increase of terrigenous supply that resulted from local tectonic movement (i.e. the initiation of collision between the South China and Cathaysia blocks). After drowning, red offshore marine facies were well developed along the platform margin, indicating an oxic sea bottom environment during the first acme of GOBE in South China. The changes in environments associated with this transition may have provided new evolutionary opportunities that contributed to the Middle Ordovician diversification.

Distribution of Bottom Trawling Effort in the Yellow Sea and East China Sea.

Bottom trawling is one of the most efficient fishing activities, but serious and persistent ecological issues have been observed by fishers, scientists and fishery managers. Although China has applied the Beidou fishing vessel position monitoring system (VMS) to manage trawlers since 2006, little is known regarding the impacts of trawling on the sea bottom environments. In this study, continuous VMS data of the 1403 single-rig otter trawlers registered in the Xiangshan Port, 3.9% of the total trawlers in China, were used to map the trawling effort in 2013. We used the accumulated distance (AD), accumulated power distance (APD), and trawling intensity as indexes to express the trawling efforts in the Yellow Sea (YS) and East China Sea (ECS). Our results show that all three indexes had similar patterns in the YS and ECS, and indicated a higher fishing effort of fishing grounds that were near the port. On average, the seabed was trawled 0.73 times in 2013 over the entire fishing region, and 51.38% of the total fishing grounds were with no fishing activities. Because of VMS data from only a small proportion of Chinese trawlers was calculated fishing intensity, more VMS data is required to illustrate the overall trawling effort in China seas. Our results enable fishery managers to identify the distribution of bottom trawling activities in the YS and ECS, and hence to make effective fishery policy.

Non-calcified macroalgae from the lower Famennian (Upper Devonian) of the Holy Cross Mountains, Poland

Non-calcified algal remains were collected from the lower Famennian deposits at the Kowala quarry in the Holy Cross Mountains, central Poland. Each specimen is represented solely by vegetative organs. On the basis of the material collected, a new algal genus and species has been formally erected. Vittella dixii nov. gen., nov. sp. (Order ?Bryopsidales) includes thalli consisting of long bundles of hair-like filament structures arranged in parallel fashion to the thallus length. Some other algal remains are regarded as Inocaulis-like forms. They possess long, flat blades with entire margins, and are ornamented with very dense, hair-like projections. The rest of the specimens found so far has been illustrated and tentatively classified as probably belonging to either Bryopsidales or Dasycladales algae. The exceptional preservation of the non-calcified algal thalli investigated suggests that special taphonomic conditions have prevailed during sedimentation of the lower part of the Famennian Kowala section. These may have involved rather rapid burial in oxygen-restricted (dysoxic and anoxic) sea-bottom environment, inhibiting the activities of scavengers and bioturbators, as well as oxidative degradation. The preservation of the algae, together with sedimentological and geochemical characteristics of the host rocks indicate that they rather represent parautochthonous assemblage, buried close to their natural habitat.

韓国竜院湾における底質改善法の設計

韓国竜院湾における底質改善法の設計

A Parametric Model for Characterizing Seabed Textures in Synthetic Aperture Sonar Images

High-resolution synthetic aperture sonar (SAS) systems yield finely detailed images of sea bottom environments. SAS image texture models must be capable of representing a wide variety of sea bottom environments including sand ripples, coral or rock formations, and flat hardpack. In this paper, a parameterized model for SAS image textures is derived from the autocorrelation functions (ACFs) of the SAS imaging point spread function (PSF) and the ACF of the seabed texture sonar cross section (SCS). The proposed texture mixture model is analytically tractable and parameterized by component mixing parameters, mixture component correlation lengths, the single-point intensity image statistical shape parameter, and the rotation of the ACF mixture components in the 2-D imaging plane. An iterative parameter estimation algorithm based on the expectation-maximization (EM) algorithm for truncated data is presented and tested against various synthetic and real SAS image textures. The performance of the algorithm is compared and discussed for synthetically generated data across various image sizes and texture characteristics. The model fit is also compared against a small set of real SAS survey images and is shown to accurately fit the imaging PSF and seabed SCS ACF for these textures of interest.

An Experimental Study on Effect of Oxygen Supply to the Bottom of Hypoxic Sea on Oxygen Consumption Characteristic and Sea Bottom Environment

An Experimental Study on Effect of Oxygen Supply to the Bottom of Hypoxic Sea on Oxygen Consumption Characteristic and Sea Bottom Environment

A Study on Remediation Index of Sea Bottom Environment and Its Estimation Method by Field Investigation

Oxygen consumption by bottom sediment in a eutrophied port and harbor is modeled based on field investigation. The model consists of factors of biological contribution and chemical-physical contribution. It is presented that these factors can be estimated by water temperature and dissolved oxygen above the sea bottom. Through modeling sediment oxygen consumption it is found that a penetration depth of oxygen is a useful parameter to represent sea bottom environment as a remediation. Further, estimation method of penetration depth of oxygen is improved to take into the change of the dissolved oxygen above sea bottom consideration.

The impact of the Bagnoli industrial site (Naples, Italy) on sea-bottom environment. Chemical and textural features of sediments and the related response of benthic foraminifera

The coastal zone of the disused industrial site of Bagnoli, has been studied since 1999 in order to highlight chemical and ecological features of pollution, mainly due to a steel plant. This further study was performed in order to check the foraminiferal response to changes in sediment grain-size and contaminant concentrations and to recognise the actual effects of the environmental stress determined by industrial pollution on the foraminiferal assemblages. This was attained by considering a wider area than in the previous studies so as to recognise the possible reference conditions. Very high contamination, mainly due to Cu, Fe, Hg, Mn, Ni, Pb, Zn and PAHs, was recorded in the marine sediments close to the steel plant. Contaminant concentrations and sediment composition were recognised as important factors influencing the foraminiferal response by means of statistical analysis. The foraminiferal abnormality index (FAI) is positively correlated with heavy metals concentration, exceeding the natural threshold in front of the plant. Furthermore, increasing pollution levels correspond to the increase of pollution-tolerant species in the assemblage.

Mineralogical, petrological and radioactivity aspects of some building material from Egyptian Old Kingdom monuments

Abstract Mineralogical, petrological, XRF and radioactivity measurements were carried out on several Egyptian monuments (at Giza plateau and Abydos), as an integrated archaeological sciences project concerning Egyptian cultural heritage with a threefold aim: (a) the multifold analysis of construction material (granite, limestone, sandstone, gypsum), providing new data, (b) a detailed radioactivity survey of the monuments, and (c) the development of a new optical stimulated luminescence dating approach for limestone buildings. Regarding the aim (a), hypotheses that large building stones used in the monuments were cast, as opposed to carved out of natural stone, are not supported by (i) the presence of undamaged fossils, (ii) lack of zeolite peaks in X-ray patterns, which would be expected if CaO was used in making cement, and (iii) random emplacement and strictly homogeneous distribution of fossil shells in the whole rock in accordance with their initial in situ settling in a fluidal sea bottom environment. Moreover, statistical clustering of chemical composition indicated five rock sub-categories and XRF analysis reported inhomogeneity of rock composition. In aim (b) a detailed dose rate survey of the studied monuments and of the radioisotope content (U, Th, K, Rb) of specimens is reported that form a unique data-base for any undertaken dating project. Regarding aim (c), quartz separation from limestone powder presents a new way to date limestone blocks by the single aliquot Optical Stimulated Luminescence (OSL) dating protocol, and three indicative dating cases are presented.

Subtidal macrozoobenthos communities from northern Chile during and post El Niño 1997–1998

Despite a large amount of climatic and oceanographic information dealing with the recurring climate phenomenon El Nino (EN) and its well known impact on diversity of marine benthic communities, most published data are rather descriptive and consequently our understanding of the underlying mechanisms and processes that drive community structure during EN are still very scarce. In this study, we address two questions on the effects of EN on macrozoobenthic communities: (1) how does EN affect species diversity of the communities in northern Chile? and (2) is EN a phenomenon that restarts community assembling processes by affecting species interactions in northern Chile? To answer these questions, we compared species diversity and co-occurrence patterns of soft-bottoms macrozoobenthos communities from the continental shelf off northern Chile during (March 1998) and after (September 1998) the strong EN event 1997–1998. The methods used varied from species diversity and species co-occurrence analyses to multivariate ordination methods. Our results indicate that EN positively affects diversity of macrozoobenthos communities in the study area, increasing the species richness and diversity and decreasing the species dominance. EN represents a strong disturbance that affects species interactions that rule the species assembling processes in shallow-water, sea-bottom environments.

東京都内湾の底層水域環境と底生動物との関係

An investigation on relationship between sea bottom environment and macrobenthic fauna was carried out at 29 points of Tokyo Inner Bay in different seasons. Concentrations of COD and total sulfide and thickness of sedimentary accumulation in all investigated areas except some coastal areas and waterways were over 30 mg·g-1, 1.0 mg·g-1 and 0.7 m respectively, which suggested that the sediment of the above area had suffered from serious organic pollution. The number of macrobenthic species decreased at the places where concentrations of COD and total sulfide and ignition loss of sediment were over 20 mg·g-1, 0.3 mg·g-1 and 8%. More than 10 species of macrobenthos were hardly observed at the places where COD concentration, ignition loss, total sulfide concentration of sediment and thickness of sedimentary accumulation were over 50 mg·g-1, 14%, 2 mg·g-1 and 1 m, respectively. No macrobenthos was observed in the offshore areas with serious organic pollution and macrobenthic fauna at the places surrounding was very poor in summer. The inner area of central waterbreak, where the sediment condition was comparatively good, could have diverse and rich macrobenthic fauna in spring, however it became an area with no or poor macrobenthos in summer due to the decrease of DO in sea bottom layer.

人工護岸構造物の優占生物が大阪湾沿岸域の富栄養化に及ぼす影響 １． 垂直護岸でのムラサキイガイの成長と脱落

Some areal investigations were conducted along the coast of Osaka Prefecture from 1989 to 1991 and effects of Mytilus populations on the coastal bottom environment were examined on the basis of their distribution, production and elimination. Mytilus edulis galloprovinciallis predominated on vertical walls or block mounds of the northern and eastern coasts of Osaka Bay, and its maximum standing stock reached 230.4 kg m&lt-1&gt in wet body weight at a breakwater outside Osaka South Outer-Port in July 1990. The total biomass of the mussels along the eastern coasts of Osaka Bay in July 1990 was estimated as ca. 1.2 × 104 t in wet body weight, ca. 5.5 × 103 t in wet tissue weight and ca. 90 t in dry tissue nitrogen. Population density and biomass of M. edulis galloprovinciallis markedly declined in Ozaki Harbor in late summer. As a result, elimination of the mussels (108.4 gN m&lt-2&gt) exceeded by 1.7 times than their production (65.1 gN m&lt-2&gt) in May to September, 1990. These findings suggested that the bulk of the mussels was deposited and decomposed on the sea bed in summer when oxygen saturations of the bottom seawater were low. For dense population of M. edulis galloprovinciallis on the vertical walls of the eutrophic Osaka Bay, more attention should be paid to their negative effects on the sea bottom environment by their mortality and decomposition in summer, rather than the positive effects through their filtering and purifying functions of the sea water.

Generation of metal deposits on the sea floor

Recent studies of volcanogenic base metal sulfide deposits and of metalliferous sediments in the Red Sea indicate precipitation of iron and base metals under conditions varying from reducing to oxidizing, at or near sites of fumarolic brine emission onto the sea floor. Differing lithofacies of iron-rich sediments were apparently deposited penecontemporaneously, mainly in response to changing chemical, biological, and sedimentary lithofacies conditions.Iron-rich sediments associated with the cupriferous pyrite bodies of Cyprus have been studied to determine the behavior of Fe, Mn, Cu, Zn, Pb, Ni, Co, Cr, Sn, Mo, Ag, and Au, when these fumarolic brines enter the sea bottom environment. Variations in metal abundances and ratios indicate that rapidly changing Eh is a major factor controlling metal deposition on the sea floor. The Fe/Mn ratio in these sediments is a useful indicator of the amount of interaction of these fumarolic brines and normal oxygenated sea water. Results suggest that zinc, copper, and gold are concentrated in the high Fe/Mn ratio proximal sediments; nickel is concentrated in the low Fe/Mn ratio distal sediments; and lead, silver, tin, and molybdenum are relatively unaffected by oxidation of the fumarolic brine solution by normal sea water.These concepts of sea floor deposition controlling the distribution of metals may also be applicable to other types of stratabound metalliferous deposits, like certain skarn, greisen, and gold ores, heretofore considered to be of epigenetic origin.