Mouth Of Bay Research Articles

Long-Term Temporal and Spatial Distribution of Coliform Bacteria in Jiaozhou Bay Associated With Human Activities and Environmental Governance

Coliform bacteria (CB) can be used as an indicator of seawater quality. Long-term monitoring of seawater quality based on CB abundance is lacking in Jiaozhou Bay. In this study, CB abundance in surface seawater of 12 different stations in Jiaozhou Bay was investigated by culturing method. The results showed that: (1) the abundance of CB showed a decreasing tendency during the investigation. During 2004–2007, 2008–2013, and 2014–2017, the average CB abundance decreased significantly, forming a “three stages phenomenon”; (2) the average CB abundance in the first half of the year was lower than that in the second half; (3) the CB abundance in Jiaozhou Bay was spatially heterogeneous. The maximum average CB abundance was observed in the estuary area, and followed by the bay mouth area, the outer bay area, and the inner bay area. The highest abundance may be associated with sewage discharge related to human activities; (4) the abundance of CB was most positively correlated with the concentration of ammonium salt and nitrate, while most negatively correlated with salinity; (5) the years 2007 (2008) and 2013 (2014) were time points of the “three stages phenomenon.” These time points coincide with environmental governance actions, indicating that the actions have played a prominent role in improving seawater quality. Long-term survey of CB can not only serve as an indicator of seawater quality, but also provide a basis for the development of environmental governance strategies and pollution control.

Macrobenthic community of a tropical bay system revisited: Historical changes in response to anthropogenic forcing

The present study examines historical perspectives of the macrobenthic community in response to different phases of anthropogenic perturbations in Kakinada Bay, a tropical embayment on the east coast of India. Multivariate analysis of the snapshot data (1958–2017) revealed considerable changes in the Bay environment following a breakwater construction across the Bay mouth in 1997. Subsequently, port expansion activities, industrialization, urbanization, and geomorphic alterations in the Godavari delta brought deterrent changes in the Bay. The fluctuations over the years in hydrographical and sediment characteristics increased environmental heterogeneity and caused significant spatio-temporal shifts in the macrobenthic community between 1995-1996 and 2016-2017. The observed variabilities were suggestive of anthropogenic perturbations of the system with future repercussions on Bay ecosystem functioning. Overall, this study provides evidence on the long-term impact of anthropogenic activities on coastal marine communities and stresses the importance of macrobenthos as bioindicators of such changes in tropical systems.

Fishing Ground Mapping Model in The Semi-Enclosed Saleh Bay, West Nusa Tenggara

Saleh Bay is a semi-enclosed area of water in Nusa Tenggara Barat Province that is enriched by fisheries resources. The bay’s strategic position, surrounded by several small islands, makes it an area of fertile water. An area of water is considered a potentially ideal fishing ground if it contains several oceanographic phenomena, including thermal fronts and upwelling. Fishing activities in Saleh Bay have been found to be ineffective and inefficient due to local people’s continued use of traditional methods such as fishing by signs of nature (instincts), wind direction, astrological signs and previous experience. This study aimed to create a mapping model of the fishing grounds in Saleh Bay based on remote sensing satellite data. Spatial analysis of daily level 3 images from the Suomi-National Polar-Orbiting Partnership (SNPP) was conducted throughout January and August 2019. The image acquisition period was adapted based on the seasonal system of Indonesia. The study area was determined based on thermal front events as identified by sea surface temperature (SST) data analysed using statistical regression with a Non-Linear Multi-Channel SST (NLSST) approach. An ideal fishing ground is characterised by several oceanographic settings such as upwelling and thermal front occurrence. The average SST distribution in January 2019 was relatively high, ranging from 30.39 to 33.70 oC, while in August 2019, the temperature declined significantly, ranging from 25.09 to 29.30 oC. Concerning the fishing ground model, a plethora of potential fishing ground areas were identified in August compared to January 2019, at 144 and 42 points respectively. This reflected the density of the fishing grounds observed. The fishing grounds were most likely to be concentrated in the bay mouth during the southwest monsoon and within the bay near the plateau during the northeast monsoon. The seasonal variability of Saleh Bay played a significant role in the spatial extraction of the fishing ground data.

The Anthropogenic Impact on the True Seals (Carnivora: Phocidae) at the Mouth of Piltun Bay (Sakhalin Island, Russia)

The Anthropogenic Impact on the True Seals (Carnivora: Phocidae) at the Mouth of Piltun Bay (Sakhalin Island, Russia)

Spring phytoplankton blooms in the Northern Satsunan region, Japan, stimulated by the intrusion of Kuroshio Branch water

The Kuroshio current greatly affects biological processes in coastal areas. The Kagoshima Bay has good spawning ground for major migratory fish, serves as an important feeding area for fish larvae, and is affected by the Kuroshio current; however, there is little information concerning the biological response to the Kuroshio intrusion in this location. During the mixing period, the Kuroshio current approaches the Kagoshima Bay and a density flow, consisting of surface inflow and bottom outflow, is generated. We hypothesize that the bottom water in the bay, having a high nutrient concentration, mixes with the surface layer when the water flows out of the bay and that this contributes to the high biological production at the bay mouth. In this study, we conducted a field survey of the water quality in March 2016 and, using a three-end member mixing model, examined whether the bottom water of the bay could be a nutrient source supporting the phytoplankton bloom in the bay mouth. We discuss the fate of the organic matter derived from the primary production promoted by a nutrient supply event. The results indicate that the N-based phytoplankton biomass represented less than 80% of the N uptake by the phytoplankton, as estimated by subtracting the measured nitrate concentration from the supplied nitrate concentration based on the mixing model, indicating that the phytoplankton bloom at the bay mouth was supported by the supply of bottom water from the bay. Based on the C/N molar ratio (6.4) calculated by C/chlorophyll a (Chl-a) and N/Chl-a in this study, the highest value of nitrogen uptake was 12 mg C m−3 d−1 in terms of the carbon assimilation. The feeding rate of the mesozooplankton was estimated to be 13.6 mg C m−3 d−1 using a physiological model. An analysis of the food web structure is required to assess the effects of feeding by mesozooplankton; however, most of the phytoplankton bloom caused by mixing could be efficiently transferred to mesozooplankton in this study area.

Изменение седиментационных потоков плутония в донные отложения бухты Севастопольская в период до и после аварии на ЧАЭС

Бухта Севастопольская, расположенная в северной акватории Чёрного моря, подвергалась радиоактивному загрязнению техногенными радионуклидами, включая 238,239+240Pu, и испытывала другие виды техногенной нагрузки. Одним из них явилось строительство заградительных молов на входе в бухту в 1975–1986 гг., которое привело к изменению её гидрологического режима. Целью данной работы было оценить изменение седиментационных потоков 238Pu и 239+240Pu в донные отложения устьевой части бухты Севастопольская в период до и после аварии на Чернобыльской АЭС (1962–1986 и 1986–2013 соответственно). Плутоний в осадках определяли радиохимическим методом, с последующим измерением активности радиоизотопов на альфа-спектрометре. Скорость осадконакопления определяли с помощью геохронологической датировки слоёв осадка по изменению отношения активностей 238Pu/239+240Pu в керне донных отложений. Затем рассчитывали скорость седиментации осадочного вещества в донные осадки. Установлено, что в период после 1986 г. среднегодовая скорость осадконакопления и скорость седиментации осадочного вещества в устье бухты увеличились на 63 и 70 % соответственно. Оценка седиментационных потоков 238,239+240Pu за два исследуемых периода показала, что поток 238Pu в донные отложения увеличился после 1986 г. на 150 %, а поток 239+240Pu — на 49 %. Повышенная процентная доля 238Pu в седиментационном потоке плутония после 1986 г. указывает на чернобыльское происхождение плутония в слоях донных отложений выше 11 см. Суммарный эффект увеличения седиментационных потоков 238,239+240Pu в устье бухты в постчернобыльский период обусловлен ростом интенсивности радиоактивных выпадений после аварии на ЧАЭС и влиянием гидротехнических сооружений на режим седиментационных процессов в акватории (увеличением скорости седиментации осадочного вещества).

Extent and Causes of Chesapeake Bay Warming

AbstractCoastal environments such as the Chesapeake Bay have long been impacted by eutrophication stressors resulting from human activities, and these impacts are now being compounded by global warming trends. However, there are few studies documenting long‐term estuarine temperature change and the relative contributions of rivers, the atmosphere, and the ocean. In this study, Chesapeake Bay warming, since 1985, is quantified using a combination of cruise observations and model outputs, and the relative contributions to that warming are estimated via numerical sensitivity experiments with a watershed–estuarine modeling system. Throughout the Bay’s main stem, similar warming rates are found at the surface and bottom between the late 1980s and late 2010s (0.02 ± 0.02°C/year, mean ± 1 standard error), with elevated summer rates (0.04 ± 0.01°C/year) and lower rates of winter warming (0.01 ± 0.01°C/year). Most (~85%) of this estuarine warming is driven by atmospheric effects. The secondary influence of ocean warming increases with proximity to the Bay mouth, where it accounts for more than half of summer warming in bottom waters. Sea level rise has slightly reduced summer warming, and the influence of riverine warming has been limited to the heads of tidal tributaries. Future rates of warming in Chesapeake Bay will depend not only on global atmospheric trends, but also on regional circulation patterns in mid‐Atlantic waters, which are currently warming faster than the atmosphere.

Dynamics of Tidal and Residual Currents Based on Coastal Acoustic Tomography Assimilated Data Obtained in Jiaozhou Bay, China

AbstractTo investigate the dynamics of tidal and residual currents in a shallow bay with narrow bay mouth and large tidal flat area, this study conducted three sets of coastal acoustic tomography (CAT) observations at 13 stations in deep area of Jiaozhou Bay (JZB), China, from December 6–18, 2015. Thereafter, travel time difference data observed via CAT were assimilated into a barotropic tidal model to realize an extrapolated study in tidal flats. The root mean square difference was 6.5 cm/s between assimilation and acoustic Doppler current profile data. Harmonic analyses indicated that the semidiurnal tide (M2) was predominant; however, relatively large nonlinear tidal currents (M4 and M6) were also found. Moreover, the spatial mean amplitudes of M2, M4, and M6 were 0.35 (excluding the tidal flat), 0.09, and 0.04 m/s, respectively. Dynamic analyses showed that continuity and advection terms were the main contributors to M4 in the bay mouth, whereas M4 in the tidal flats was generated by continuity and friction terms. Furthermore, bottom friction was the primary contributor to M6. In addition, residual currents with multi‐vortex structures appeared near the bay mouth, the maximum speed reached 0.60 m/s, and advection, continuity, and bottom friction contributed more to the generation of residual current eddies. Horizontal pressure gradient of residual elevation and advection of tidal and residual currents were the dominant factors maintaining the residual current near the bay mouth. The generation mechanisms of M4 and M6 were first discussed based on the assimilation of the current field data in JZB.

Mechanisms Driving Decadal Changes in the Carbonate System of a Coastal Plain Estuary

AbstractUnderstanding decadal changes in the coastal carbonate system is essential for predicting how the health of these waters responds to anthropogenic drivers, such as changing atmospheric conditions and riverine inputs. However, studies that quantify the relative impacts of these drivers are lacking. In this study, the primary drivers of decadal trends in the surface carbonate system, and the spatiotemporal variability in these trends, are identified for a large coastal plain estuary: the Chesapeake Bay. Experiments using a coupled three‐dimensional hydrodynamic‐biogeochemical model highlight that, over the past three decades, the changes in the surface carbonate system of Chesapeake Bay have strong seasonal and spatial variability. The greatest surface pH and aragonite saturation state (ΩAR) reductions have occurred in the summer in the middle (mesohaline) Bay: −0.24 and −0.9 per 30 years, respectively, with increases in atmospheric CO2 and reductions in nitrate loading both being primary drivers. Reductions in nitrate loading have a strong seasonal influence on the carbonate system, with the most pronounced decadal decreases in pH and ΩAR occurring during the summer when primary production is strongly dependent on nutrient availability. Increases in riverine total alkalinity and dissolved inorganic carbon have raised surface pH in the upper oligohaline Bay, while other drivers such as atmospheric warming and input of acidified ocean water through the Bay mouth have had comparatively minor impacts on the estuarine carbonate system. This work has significant implications for estuarine ecosystem services, which are typically most sensitive to surface acidification in the spring and summer seasons.

Origin of the Particulate Organic Matter in a Monsoon-Controlled Bay in Southern China

In this study, the isotopic composition (δ13C and δ15N), total organic carbon content, total nitrogen content, and C/N ratios of suspended particulate organic matter (POM) in Zhanjiang Bay, which is a semi-enclosed bay with concentrated artificial activities in Southern China, were analyzed in order to investigate the seasonal variations in the principal POM sources in the monsoon region. In summer, the δ13C and δ15N values showed a weak correlation with the chlorophyll a (Chl a), suggesting that terrigenous sources were dominant. However, in winter, the particulate organic carbon and particulate nitrogen values were correlated with the Chl a in the middle bay and bay mouth. Moreover, the δ13C values showed a significant correlation with Chl a during the winter, indicating that the contribution of the in situ phytoplankton was relatively important and was affected by the monsoon in winter. Compared with the corresponding δ13C values, the δ15N values exhibited a complex spatial distribution. By using a Bayesian mixing model, in the upper bay, the source of POM was mainly from marine organic matter (49%) in summer, and almost an equilibrated contribution of all sources in winter. In the middle bay and bay mouth, the POM contribution mainly originated from marine organic matter (53%) during the winter. In contrast, the POM source was mainly soil organic matter (63%) in summer, suggesting that the POM was sourced from the runoff from the upstream basin. Our results suggest that the seasonal shifts of the source of POM should be taken into account when estimating C or N mass balance in the monsoon-controlled bay.

Size, spatial distribution and potential of anchovy in Inner Ambon Bay

Inner Ambon Bay is a small pelagic fish fishing ground, especially anchovy. Anchovy plays important role in the skipjack fishery as live bait in Ambon city. Nevertheless, research for its resource management is rarely done. The aim of the research is to obtain information of population size, spatial distribution of densities and Maximum Sustainable Yield of anchovy. Densities data of fish were obtained using hydro acoustics device at six parallel transect lines and one cross parallel transect line in October 2015. Three fish species caught by beach seine, comprise Encrasicholina heteroloba (96.3%), Sardinella spp.(2.8%) and Rastrelliger spp.(0.9%). Mean value of total length of E. heteroloba was 5.30 cm shorter than the length of same fish noted in October 2005 was 5.48cm. Spatial distribution of anchovy densities shows that low density (0-2 fish/m2) occupy wider space, evenly distributed in north, east, and south of the bay. The fish density of 2-4 fish/m2 were in small groups occupy smaller space distributed in the middle to west of the bay. The density 4–6 fish/m2 to high density 28–30 fish/m2 occupy only very small space in the west near bay mouth. Maximum sustainable yield of anchovy in inner Ambon Bay was estimated 6.9±4.3 tons.

The Study on Hydrodynamic Characteristics of Qianhai Bay in Shenzhen

Based on the fixed-point observation data in Qianhai Bay of Shenzhen in May 2020, the horizontal and vertical distribution characteristics of tidal current, wave in summer near Qianhai Bay of Shenzhen are analyzed. The results show that the correlation coefficient of high and low tide level between the Qianhai Bay and Chiwan hydrological station is 0.98. The former Bay is dominated by irregular semidiurnal tidal current, which basically rotates anticlockwise. Due to the special shape of Qianwan Bay, the average velocity in the bay is small, but the maximum velocity of flood tide is 0.48m/s, the maximum velocity of ebb tide is 0.45m/s, the possible maximum velocity is 0.64m/s at the bay mouth. The average wave height is 0.07m, the normal wave direction is southwest West (WSW), and the average period is 2.9s.

Probing the contamination characteristics, mobility, and risk assessments of typical plastic additive–phthalate esters from a typical coastal aquaculture area, China

Contamination characteristics, equilibrium partitioning and risk assessment of phthalate esters (PAEs) were investigated in seawater, sediment and biological samples collected from the Xiangshan Bay area during an annual investigation between January and November 2019. PAE concentrations detected in the mariculture environment in surface seawater, sediment, and biological samples were 172–3365 ng/L, 190–2430 μg/kg (dry weight [dw]), and 820–4926 μg/kg (dw), respectively. The dominant congeners in different media included di-n-butyl phthalate (DnBP), diisobutyl phthalate (DiBP), and di(2-ethylhexyl) phthalate (DEHP). The inner bay and the bay mouth were the gathering area of PAEs and heavily influenced by the mariculture activities, river inputs, and anthropogenic activities. The bioaccumulation of PAEs demonstrated benthic feeding fishes with relatively high trophic levels concentrated high levels of phthalates. The mobility of PAEs in sediment–seawater showed that the transfer tendency of low-molecular weight species was from the sediment to the water, which was in contrast with those of high-molecular weight PAEs. DEHP, DiBP and DnBP had various degrees of ecological risks in the aquatic environment, whereas only the DiBP posed potential risks in sediments. The current assessment of carcinogenic and noncarcinogenic risks posed by fish consumption were within acceptable limits for humans.

Effects of terrestrial inputs and seawater intrusion on zooplankton community structure in Daya Bay, South China Sea

Daya Bay is a eutrophic coastal region with dynamic physico-chemical conditions influenced by terrestrial inputs and seawater intrusion. Zooplankton is a crucial trophic intermediary for energy transfer and fishery resources. In this study, we assessed the distribution and composition of zooplankton in Daya Bay during summer and winter of 2015. We found that zooplankton diversity was the lowest and dominated by small copepods (Acartia spp. and Paracalanus spp.) and gelatinous Oikopleura spp. under terrestrial inputs in the Dan'ao River estuary and Aotou barbour. The highest zooplankton diversity was observed at the bay mouth that influenced by salty intruded seawater, and the dominant oceanic species (such as Euchaeta concinna and Subeucalanus subcrassus invaded into the top of the bay in winter. The dominant species in the estuary shift from Penilia avirostris to Acartia spp. compared with historical researches, indicating the effect of human activities on the succession of dominant species.

The coupled effects of stocking density and temperature on Sea Scallop (Placopecten magellanicus) growth in suspended culture

Despite the profitability of the wild Atlantic Sea Scallop, Placopecten magellanicus, fishery, the U.S. still imports more than 26,000 tonnes of various scallop products annually. Atlantic Sea Scallop (hereafter referred to as scallop) aquaculture is one method of mitigating this imbalance. We examined scallop growth at three sites across the mouth of Penobscot Bay, Maine to determine the coupled effects of lantern net stocking density and temperature on growth and mortality. Scallops were held in high and low (20 and 10 individuals tier−1, respectively) density treatments, and shell height measurements were recorded monthly for one year. We divided the growth rate analysis into three periods: winter - spring, summer, and fall. During summer across all sites, growth rates were 75 % higher in low-density nets than in high-density nets. We observed significant nonlinear relationships between shell height growth rate, temperature, and stocking density. Optimal growth occurred within a window of 10–15 °C. Above this threshold, there was a distinct negative relationship between temperature and growth. Our results highlight the importance of maintaining low densities within nets, particularly during periods of high temperature and growth. However, handling in summer and early fall may lead to mortality. Therefore, we recommend that growers stock nets at low densities in the spring, ensuring that they will not require thinning during peak temperatures. Similarly, finding sites that maximize time within a thermal envelope of 10–15 °C will be critical, which in the case of the Gulf of Maine will most likely warrant leasing sites at the mouths of estuaries and bays. These locations offer a combination of sufficient depth and space for sparsely stocked nets, adequate food levels, and optimal salinity and temperature.

Tsunami-induced inundation on the coast of Palu City

The frequency of tsunamis in Indonesia is smaller than other natural disasters. But its destructive power is quite large. Although this disaster has a low probability of occurring. The losses caused by these disaster equaled and even exceeded frequent disasters such as floods and landslides. More than 85% of tsunamis in Indonesia were caused by underwater earthquakes. Thus, mitigation efforts are needed to minimize the impact of the tsunami disaster. The source of the tsunami wave was generated on the Makassar Strait Thrust North Fault. In this study, tsunami was modelled by using Delft3D software. The model approach uses the principle of momentum and continuity. The area of the model was divided into 2 grids. The wave reached the bay mouth in 10 minutes and arrived at the coast of the study area in 20 minutes. The highest peak of water level on the coast occurred in the second wave with an amplitude of 2.45 m and a wave height of 5.19 m. The inundation map was compared to the recorded data from the 2018 tsunami. It was found that there is no significant difference between the two although the tsunami generation were different.

Impacts of large-scale aquaculture activities on the seawater carbonate system and air-sea CO2 flux in a subtropical mariculture bay, southern China

In this study, the variations of the seawater carbonate system parameters and air-sea CO2 flux (FCO2) of Shen’ao Bay, a typical subtropical aquaculture bay located in China, were investigated in spring 2016 (March to May). Parameters related to the seawater carbonate system and FCO2 were measured monthly in 3 different aquaculture areas (fish, oyster and seaweed) and in a non-culture area near the bay mouth. The results showed that the seawater carbonate system was markedly influenced by the biological processes of the culture species. Total alkalinity was significantly lower in the oyster area compared with the fish and seaweed areas, mainly because of the calcification process of oysters. Dissolved inorganic carbon (DIC) and CO2 partial pressure (pCO2) were highest in the fish area, followed by the oyster and non-culture areas, and lowest in the seaweed area. Oysters and fish can have indirect influences on DIC and pCO2by releasing nutrients, which facilitate the growth of seaweed and phytoplankton and therefore promote photosynthetic CO2 fixation. For these reasons, Shen’ao Bay acts as a potential CO2 sink in spring, with an average FCO2 ranging from -1.2 to -4.8 mmol m-2 d-1. CO2 fixation in the seaweed area was the largest contributor to CO2 flux, accounting for ca. 58% of the total CO2 sink capacity of the entire bay. These results suggest that the carbonate system and FCO2 of Shen’ao Bay were significantly affected by large-scale mariculture activities. A higher CO2 sink capacity could be acquired by extending the culture area of seaweed.

Composition and Distributions of Nitrogen and Phosphorus and Assessment of Eutrophication Status in the Maowei Sea

Maowei Sea (MWS) is the largest oyster maricuture bay in Southwest China. Surface water from 12 sampling sites were collected during the dry season to study the composition and distribution of different forms of nitrogen (N) and phosphorus (P) beginning from the inner bay to the bay mouth in the MWS. An improved multi-parameter eutrophication index was developed and applied for the evaluation of the water quality in the MWS. Dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), and particulate nitrogen (PN) averagely accounted for 11.28%, 65.32%, and 23.39% of total N (TN) pool, dissolved inorganic phosphorus (DIP), dissolved organic phosphorus (DOP), and particulate phosphorus (PP) averagely accounted for 54.58%, 30.31%, and 15.12% of total P (TP) pool, respectively. DON and DIP were respectively the dominant forms of N and P in surface water of the MWS, during the study period. Concentration trends of DIN, DIP, DOP, PN, dissolved silicate (DSi), total organic carbon (TOC), chemical oxygen demand (COD) decreased from the inner bay to the bay mouth, suggesting that the MWS may be largely influenced by land-based inputs. Based on nutrient contents and stoichiometry, it likely that phytoplankton growth in the MWS is strongly limited by DIP during the dry season. Results from the improved eutrophication index revealed that the water quality in the MWS is in a state of moderate to poor eutrophication (average EI = 0.953). The eutrophication state decreased from the inner bay to the bay mouth. Nitrate (NO3-N), DON, DIP, DOP, and DSi showed significant positive correlations with eutrophication index (r2 = 0.52∓0.78, P < 0.05), implying that these nutrients are among the significant factors, which could be used in evaluating the eutrophication status of the MWS.

The Calculation and Model Block Diagram of the Surface Cd Content of Haibo River from Land Sources

Applying the survey data of the Cd content in the water of Jiaozhou Bay in October 1992, from the southern waters of the bay mouth to the southeastern waters, the author calculates out the horizontal loss amount, the vertical disputed amount and the vertical sediment amount of the Cd content in the surface and bottom of the water body and determines the model block diagram of the horizontal and vertical changes of Cd content, based on the content changing models of the horizontal matter and the vertical matter proposed by the author himself. The calculation results show that in October, the absolutely horizontal increase amount of Cd content in the surface and bottom layer is 0.12-0.89μg/L, and the relatively horizontal increase amount of Cd content in the surface and bottom layer is 23.52-74.78%. In the southern waters of the bay mouth, the Cd content in the surface and bottom layer has an absolutely vertical disputed amount of 0.09μg/L, and its relatively vertical disputed amount is 23.07%. In the southeastern waters of the bay, the Cd content in the surface and bottom layer has an absolutely vertical sediment amount of 0.68μg/L, and its relatively vertical sediment amount is 57.14%. There is the Haibo River near the southeastern waters of Jiaozhou Bay. In October, the Cd content of the Haibo River is 0.51μg/L, which is higher than the Cd content of 0.39μg/L carried by ocean currents. It provides a lot of supplements to the ocean currents passing the southeastern waters of the bay. During the horizontal migration of the Cd content in the surface and bottom layer, Haibo River supplements the Cd content in the ocean current with the loss and increase of the surface and bottom layer. Through the horizontal changing model of matter content, the horizontal increase of the surface Cd content is calculated. The absolute increase of the Cd content is 0.12μg/L, and the relative increase is 23.52%. Similarly, the horizontal increase of Cd content in the bottom layer is calculated. The absolute increase of Cd content is 0.89μg/L, and the relative increase is 74.78%. During the vertical migration process, the vertical change of the Cd content in the southern waters of the bay mouth and the southeastern waters of the bay reveals the following law: when the surface Cd content is low, the waters present a vertical dilution of the Cd content at the surface and bottom layer, and there is no Cd content accumulation on the seafloor. When the Cd content in the surface layers is high, the waters present a vertical accumulation of Cd content in the surface and bottom layers, and there is an accumulation of Cd content on the seafloor. According to the formula for calculating the Cd content of river sources proposed by author himself, the Cd content of the surface of Haibo River source from land is calculated to be 1.01 μg/L.

Vertical Transfer of Cd Content Between Two Parallel Currents in Opposite Motion

Based on the investigation data about Cd in Jiaozhou Bay in August, 1992, we calculated the horizontal increase amount and vertical diluted amount of Cd content in surface and bottom layers from the southwest waters of the bay to the west waters of the bay mouth, and set up the model block diagram of horizontal and vertical changes of Cd content. The results present that in August, the absolutely increase amount of Cd content in surface and bottom layers was 0.16-0.34μg/L, and the relatively increase amount of Cd content in surface and bottom layers was 51.51-66.66%. In the waters of southwest bay and west bay mouth, Cd content in surface and bottom layers had absolutely vertical diluted amount of 0.24-0.42μg/L, and its relatively vertical diluted amount was 63.63-75.00%. In the horizontal migration process of Cd content in the surface and bottom layers, the horizontal increase amount of Cd content in the surface and bottom layers reached a relatively high level from the southwest of bay to the west of bay mouth. It reveals that in the bay waters, in the parallel and opposite movement of the two currents, the current entering into the bay carried a high value of Cd content, and the Cd content migrated from the water with high content to the water with low content through the diffusion and migration of Cd content. Moreover, the migration direction of Cd content was perpendicular to the parallel movement direction of the two currents. In this way, the low-value Cd content in the outward current was increased, and at the same time, the vertical diffusion, migration and settlement of the high-value Cd content led to the increase of the Cd content in bottom layer in the outward current. In the process of vertical sediment of Cd content in the surface and bottom layers, the current had a low value of Cd content in the bay waters, and the vertical diluted amount of Cd content in the surface and bottom layers reached a high level; in the bay mouth waters, the current had high Cd content, but the vertical diluted amount of Cd content in the surface and bottom layers was also very high. In conclusion, the vertical diluted amount of Cd content in the surface and bottom layers kept a high value regardless of whether the current left the bay or whether the current carried high or low Cd content.