Semi-enclosed Water Body Research Articles

Low diversity, high dominance, and high host prevalence of parasitic isopods of the family Cymothoidae in Chilika lagoon, India: a comparative study between a semi-enclosed ecosystem and its adjoining open region.

Patterns in parasite diversity are shaped by their environmental and ecological settings, and to better understand their interactions with hosts and the corresponding biology, it is crucial to understand these context-dependent patterns. To achieve this, we use cymothoid isopods, an important group of fish parasites, to test a long-standing hypothesis about parasite diversity and prevalence pattern: whether semi-enclosed water bodies allow low diversity and high prevalence of parasitic isopods. Specifically, we compare these patterns between Chilika lagoon (Odisha, India), a semi-enclosed water body, and the adjoining Odisha coast (India). Our finding reveals that the semi-enclosed Chilika lagoon has a considerably lower diversity of parasitic isopods than its adjoining open sea along the Odisha coast. Additionally, the parasitic isopod infection levels in Chilika lagoon are noticeably higher, and isopod assemblage is less even than those in coastal waters along the Odisha coast. Our results support the hypothesised association between enclosed water bodies, parasite diversity, and host prevalence and contribute to an enhanced comprehension of the ecology of parasitic isopods in distinct marine environments.

Long term investigation on shoreline changes of an Island, inside a Gulf (Hormuz Island)

Shorelines, as the boundary between the body of water and the land, are influenced by different natural and anthropogenic factors. As a consequence, they are highly dynamic and are of great concern for coastal zone management. However, their behavior varies depending on their location, whether they are situated in the open ocean or within a semi-enclosed body of water. Besides, anthropogenic activities in developed beaches and/or coastal cities are the main reason for high rates of change. Thus, normally pristine and undeveloped areas are likely to experience lower rate of shoreline transformation. Hormuz Island as a typical undeveloped pristine island, with minimum anthropogenic activities in its coastlines, located inside a semi-enclosed body of water of the Persian Gulf, is the case study for this research. The alteration of the shoreline is extensively studied for 30 years. The shoreline change is analyzed using net shoreline movement, and linear regression rate indexes of the digital shoreline analysis system tool. Our findings indicated that alterations in the shoreline of Hormuz Island primarily align with natural processes, and the impact of anthropogenic activities on these changes is constrained. The average shoreline change is approximately 0.1 m/year and seldom surpasses 2.0 m/year. These outcomes align with findings observed in other undisturbed regions situated within semi-enclosed bodies of water, such as gulfs or bays. Utilizing identified shoreline alterations, our study area was categorized into three classes: dominant accretion, dominant erosion, and negligible transformation. The shore with negligible changes encompasses more than half of the island. Acknowledging the restricted variability in alterations observed in the beaches within the semi-enclosed area, there is a recognized need to develop an international classification for these types of beaches, in order to be comparable with each other all around the world.

Numerical modeling of ocean currents and suspended sediment distribution in Benoa Bay, Bali

Benoa Bay is a semi-enclosed water body that includes a shallow estuary area that supports important aquatic ecosystems, including mangrove ecosystems, seagrass beds, and coral reefs. The reclamation of Benoa Harbor and the construction of a toll road in Benoa Bay are suspected to have increased sedimentation. The objective of this study is to model ocean currents and suspended sediment distribution during the Northwest and Southeast monsoons in the waters of Benoa Bay. Numerical models are used to describe the hydrodynamic process as the main driver of the process of pollutant movement in the waters. The current pattern resulting from the model in the waters of Benoa Bay has the same pattern in the Northwest and Southeast Monsoons, with the current velocity of the Northwest Monsoon ranging from 0 – 1.6583 m/s and the Southeast Monsoon ranging from 0 – 1.4729 m/s. The distribution of suspended sediment in the Northwest Monsoon is quite high compared to the Southeast Monsoon. The distribution of suspended sediment in the Northwest Monsoon ranges from 0 – 846 mg/L and in the Southeast Monsoon, it ranges from 0 – 598 mg/L.

Numerical Investigation of Diapycnal Mixing of the Kitikmeot Sea in the Southern Canadian Arctic Archipelago

ABSTRACT Utilizing a 1 / 12 ∘ numerical model, we examine the diapycnal mixing patterns in the Kitikmeot Sea, a semi-enclosed water body within the southern Canadian Arctic Archipelago. The analysis reveals that mixing intensity near the sea surface varies seasonally, with effective diffusivity values ranging from 10 − 5 to 10 − 3 m 2 s − 1 , while away from the surface, the effective diffusivity remains relatively stable between 10 − 5 and 10 − 4 m 2 s − 1 . The seasonal fluctuations in surface mixing intensity are strongly influenced by ice coverage, which impacts both the stratification and the energy input to the surface driving the mixing process. Mixing energetics analysis indicates that the majority of energy contributing to the mixing processes are applied to the sea surface. During ice-free periods, wind-driven stirring dominates near-surface mixing with effective diffusivities of 10 − 5 to 10 − 4 m 2 s − 1 . Minimum near-surface effective diffusivity values occur in July and August, when the surface water is fresher and near-surface stratification is stronger due to spring freshet. Conversely, during ice-covered seasons, surface cooling and brine rejection primarily drive near-surface mixing, leading to effective diffusivities of 10 − 3 m 2 s − 1 or higher. In most cases, the observed mixing efficiency is within the range of what has been found in other regions of the Arctic Ocean.

Wind-Forced Seasonal Exchange between Marginal Seas and the Open Ocean

Abstract The circulation within marginal seas subject to periodic winds, and their exchange with the open ocean, are explored using idealized numerical models and theory. This is motivated by the strong seasonal cycle in winds over the Nordic Seas and the exchange with the subpolar North Atlantic Ocean through the Denmark Strait and Faroe Bank Channel. Two distinct regimes are identified: an interior with closed f/h contours and a shallow shelf region that connects to the open ocean. The interior develops a strong oscillating along-topography circulation with weaker ageostrophic radial flows. The relative importance of the bottom Ekman layer and interior ageostrophic flows depends only on ωh/Cd, where ω is the forcing frequency, h is the bottom depth, and Cd is a linear bottom drag coefficient. The dynamics on the shelf are controlled by the frictional decay of coastal waves over an along-shelf scale Ly = f0LsHs/Cd, where f0 is the Coriolis parameter, and Ls and Hs are the shelf width and depth. For Ly much less than the perimeter of the basin, the surface Ekman transport is provided primarily by overturning within the marginal sea and there is little exchange with the open ocean. For Ly on the order of the basin perimeter or larger, most of the Ekman transport is provided from outside the marginal sea with an opposite exchange through the deep part of the strait. This demonstrates a direct connection between the dynamics of coastal waves on the shelf and the exchange of deep waters through the strait, some of which is derived from below sill depth. Significance Statement The purpose of this study is to understand how winds over marginal seas, which are semienclosed bodies of water around the perimeter of ocean basins, can force an exchange of water, heat, salt, and other tracers through narrow straits between the marginal sea and the open ocean. Understanding this exchange is important because marginal seas are often regions of net heat, freshwater, and carbon exchange with the atmosphere. The present results identify a direct connection between processes along the coast of the marginal sea and the flow of waters through deep straits into the open ocean.

Drivers of hypoxia variability in a shallow and eutrophicated semi-enclosed fjord

Seasonal deoxygenation of coastal waters has been observed with increasing frequency around the world, with consequences for ecosystem functioning and continued benthic capacity to buffer hypoxia. Here, we present a hydrodynamical-ecological model study of the Limfjord in Denmark, an example of a semi-enclosed water body affected by recurring seasonal deoxygenation. Applying observations and model results, we show that water temperature, combined with wind strength and direction are the most important controllers of short-term interannual variability of bottom oxygen, while ventilation through episodic water inflow from the North Sea and local stratification create a spatial decoupling of deoxygenation. Nutrient load to the fjord drives sustained high biological productivity, but does not affect the interannual variability to the same degree. However, high biological turnover rates likely push the system closer towards a deoxygenated state, making the fjord more sensitive to future changes in temperature, wind and ventilation by reducing the buffer capacity of the sediments.

Effect of environmental variables on the growth of Asian green mussel Perna viridis (Linnaeus, 1758), in two different aquaculture systems in Goa, west coast of India

Asian Green mussel, Perna viridis (Linnaeus, 1758), is a bivalve mollusc with high market demand along India’s western coast, specifically in Goa. An experiment was conducted to compare the environmental variables, specific growth rate (SGR) and length-weight progression of the species raised in two different coastal aquaculture systems; a semi-enclosed water body (SEW) and an open-water system (OWS). The variables chlorophyll-a and plankton density were high in SEW and these variables were positively correlated with the growth rate of the species. The ‘b’ value of the length-weight relationship and SGR were found high and allometric in nature in SEW. The prediction of SGR using the generalised linear model has indicated that plankton density and nitrate are the variables that influence the growth of P. viridis. Thus, being a predominant filter-feeder on plankton, the high plankton density channeled through the rich nutrients and chlorophyll content might have triggered the growth of mussels in SEW. India is blessed with many semi-enclosed coastal water bodies lying unutilised, and the results indicate that there is scope for mussel culture in these systems, which will provide a source of secondary livelihood for the coastal fishers. Keywords: Bivalves, Coastal aquaculture, GLM, Molluscan culture, Zuari

Magnetotactic bacteria in vertical sediments of volcanic lakes in NE China appear Alphaproteobacteria dominated distribution regardless of waterbody types.

Magnetotactic bacteria (MTB) distribute widely in sediment habitats and play critical roles in iron cycling. Here, the vertical distribution of morphology and phylogenetic diversity of MTB in sediments (0-15cm) of three lakes (open waterbody, Bailonghu, BL; semi-enclosed waterbody, Yaoquanhu, YQ; enclosed waterbody, Yueyapao, YY) in Wudalianchi volcanic field (China) were investigated. TEM showed the appearance of coccoid, rod-shaped, oval-shaped, and arc-shaped MTB. With the increase of BL sediment depth, the number of rod-shaped and spherical MTB decreased and increased, respectively. High-throughput sequencing indicated that Alphaproteobacterial MTB dominantly thrived in these lakes regardless of waterbody types. In BL and YY, the dominant genus was Magnetospirillum (44.99-70.80%) which showed a peak in the middle layer. In YQ, the genus Magnetospira was dominant in the upper (52.36%) and middle (66.56%) layer and Magnetococcus (69.63%) existed dominantly in the bottom layer. The vertical distribution of MTB in sediments of these lakes decreased first and then increased. Functional analysis showed that ABC transporter and two-component system of MTB changed significantly with the sediment depth. RDA indicated that the distribution of Magnetospirillum was positively associated with sulfide, pH, and TC. These findings will expand our knowledge of the vertical distribution of MTB in volcanic lakes.

Influences of Tidal Flat and Thermal Discharge on Heat Dynamics in Xiangshan Bay

Water temperature in estuaries is sensitive to thermal discharges and expansive tidal flats; as such, this parameter is essential in maintaining estuarine ecosystem. Semi-enclosed water bodies with poor water exchange easily accumulate heat. This is especially true for Xiangshan Bay, which contains two power plants and a large area of tidal flats. This bay was used as an example to study water temperature and heat dynamics, considering the thermal discharge and tidal flats. This study developed and validated a three-dimensional hydro-heat flux numerical model using field data on tidal elevation, currents, water temperature, and tidal flat temperature. The Finite Volume Community Ocean Model combines an accurate thermal discharge model with the air-water-tidal flat heat flux model. The findings showed that thermal discharge provides heat to the bay in summer and winter, and increases the water temperature of the entire bay by 0.7°C in summer, while maintaining water temperature at 0.52°C in winter. The atmosphere and open seas had greater impacts on heat in the bay in winter and summer. The atmosphere and tidal flats provided heat to the bay in summer and absorbed heat from the bay during winter; the opposite was true for the open sea. The effect of tidal flats in summer is less than that in winter, and provides 1.31 × 1013 J of heat to the bay in summer, while taking 8.63 × 1013 J of heat from the bay in winter. This study provides a comprehensive understanding of the effects of tidal flats and thermal discharge on water temperature and heat in macro-tidal bays and estuaries; its results are applicable to similar bays around the world.

Indication of Possible Shifts in Copepod Species Composition in St. Pauls Inlet, a Fjordal Estuary Connected to the Gulf of St. Lawrence

St. Pauls Inlet, a coastal brackish lake/estuary within Gros Morne National Park in Newfoundland and Labrador (Canada), is a semi-enclosed body of water with a narrow 80-m wide opening to the marine Gulf of St. Lawrence and with freshwater input from 24 streams. An initial biological survey of St. Pauls Inlet in 1977/78 during Park planning stages found dominant members of the mesozooplankton community to be copepods of genera Acartia, Calanus, Oithona, and Temora. Subsequent surveys of 2009, 2010, and 2019 found Calanus abundance to be much reduced or absent and low adult microcrustacean (copepods + cladocerans) densities. Recent data suggest that Calanus finmarchicus, a large energy-rich copepod, has declined across the Gulf of St. Lawrence and the wider Northwest Atlantic, with the zooplankton community shifting towards smaller, warm-water copepods This shift is coincident with rising surface sea-surface temperatures in the Atlantic. Mid-July temperatures in the inlet were higher in 2009, 2010, and 2019 compared with 1977. Shifting zooplankton abundances in St. Pauls Inlet, even with reduced exchange with the Gulf, may reflect wider trends in the Northwest Atlantic and be a useful indicator of a changing coastal environment in this national park.

Picophytoplankton community dynamics in a tropical river estuary and adjacent semi-enclosed water body

Picophytoplankton community dynamics in a tropical river estuary and adjacent semi-enclosed water body

Environmental mechanisms associated with fish kill in a semi-enclosed water body: An integrated numerical modeling approach

Fish kill incidents are causing increasing concern to coastal communities globally due to the associated economical, commercial and social impacts. In the Arabian/Persian Gulf, human activities have accelerated to meet the rising demands and the economical ambitions, and are associated with organic and inorganic waste loads linked to algal blooms and fish kills in the receiving environment. Understanding the environmental circumstances associated with these events is crucial for planning and coastal management. This study focuses on Kuwait Bay (in the NW of the Gulf) which has a history of repeated fish kills on multiple scales. A numerical model has been successfully utilized, reproducing the key elements associated with fish kill incidents (hydrodynamics, water quality, and particle tracking) and revealing the transport and mixing time scales associated with the major fish kill incident in the Bay in 2020. The study indicated that the environmental circumstances of fish kills can vary in the Bay, so such incidents must be investigated individually. The large scale fish kill incident was found to be associated with unprecedented waste loads during summer 2020. This coincided with a low dynamic period at critical locations within the Bay. As a result, major hypoxic conditions lasting 15 days occurred along the main axis of the Bay in a manner unusual compared to previous events. The model provided key information on the dissolved oxygen, including the mixing and transport time scales, before, during, and after the event. The transport of the dead fish from the hypoxic front to the shoreline was also modeled. Collectively, model results provided generic coastal management approaches suitable for shallow embayments such as the Bay.

Modelling the advection of pollutants in the Hudson Bay complex

The Hudson Bay Complex is a system of semi-enclosed waterbodies in the eastern Canadian sub-Arctic with limited communication to the Arctic Ocean via Fury and Hecla Strait, and to the North Atlantic Ocean via Hudson Strait. There has been a significant increase in ship traffic in the Hudson Bay Complex as it provides a maritime link to Eurasia, known as the Arctic Bridge, and the southern route of the Northwest Passage, connecting the ports in the North Atlantic Ocean and Pacific Ocean. The increasing ship traffic could promote a higher risk of accident, especially when considering the higher mobility of sea ice due to the warming over the polar region . In this study, we used a high-resolution numerical model to highlight the circulation pathways of pollutants due to ocean advection . We released Lagrangian particles at 9 sites, located along the Arctic Bridge and the southern Northwest Passage, every 10 days through the operating season (June–October) for 12 years (2004–2015), to determine when and over which sites the accidental spill of pollutant would have the greatest negative impact. We characterized three circulation pathways with respect to the oceanic circulation regime of where the particles were initially seeded, and computed the following parameters to numerically describe the spreading of particles: area occupied, distance travelled, and the depths of particles. We conclude that the particles released in eastern Hudson Strait exhibited the largest spreading area rapidly below the surface layer, posing a challenge for recovery operations and a threat to the environment. • Circulation pathways of pollutants in Hudson Bay due to ocean advection are studied. • This study is based on an ocean-sea ice coupled high-resolution model and Lagrangian particle tracking scheme. • The particles exhibited three main pathways with respect to oceanic circulation regime. • Particles released in the eastern Hudson Strait exhibited the largest spreading area with highest variability.

Detecting Ship Wakes for the Study of Coastal Processes

Rätsep, M.; Parnell, K.E., and Soomere, T., 2020. Detecting ship wakes for the study of coastal processes. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1258–1262. Coconut Creek (Florida), ISSN 0749-0208.Wakes from contemporary vessels may affect, and in some places dominate, coastal processes in the vicinity of major shipping lanes. The analysis of the properties and impact of wakes has generally been restricted to wakes that can be visually observed in raw data. In this work, spectral analysis of the time series of single-point measurements of water surface elevation from Tallinn Bay is used to highlight the structure of ship wakes using a Short Time Fourier Transform. This method makes it possible to determine the speed and distance of a vessel from the measurement site. Wakes are detected using an algorithm based on Gabor multipliers. The results are compared with vessel passages retrieved from the Automatic Identification System (AIS) data. The algorithm detects the majority of ship wakes that can be visually recognized in spectrograms and misses only those with low signal to noise ratio or those in close proximity to another vessel wake. The calculated speed and distance are consistent with the AIS data except for high-speed vessels sailing at ≥30 knots. The results indicate that by using these techniques the detection of vessel wakes from a single-point wave record is achievable under favorable weather conditions. The methods provide an option for mitigation of the impact of ship wakes in semi-enclosed water bodies.

The Importance of Offshore Exchange for Water Temperatures in Norwalk Harbor

The Norwalk Harbor is the estuarine portion of the Norwalk River, which connects to Long Island Sound. Like many embayments, this macrotidal harbor experiences higher summer water temperatures than waters farther offshore, which contribute to water quality problems. The summer season is characterized by surface heating, strong tides (as in all seasons), weak winds, and low river discharge. To determine the relative importance of exchange with offshore waters in regulating the harbor temperature, a control volume approach is used to make a summer temperature budget for the harbor based on observations. Time series of harbor temperature, surface heat flux, and Norwalk River inflow are constrained with measurements of water temperatures, atmospheric conditions, and river discharge. The impact of offshore exchange is inferred as the residual after the real temperature change in the harbor, and all other sources of temperature change are constrained. The analysis indicates that, in the summer, the impact of offshore exchange is comparable to the impact of the surface heat flux and far greater than the impact of the river. Consequently, the harbor is much cooler during summer than it would be if it was not connected to Long Island Sound. The methods applied here are applicable to any relatively small, semi-enclosed body of water and do not require the use of models or velocity observations. It is likely that many other embayments have an appreciable degree of thermal buffering via exchange with offshore waters.

Magnetotactic bacteria diversity of and magnetism contribution to sediment in Wudalianchi volcanic barrier lakes, NE China

Magnetotactic bacteria (MTB), the members of sediment microorganisms, play an important role in geochemical iron-cycling and sediment magnetism. This study aimed to investigate the diversity and magnetism contribution of MTB in three volcanic barrier lakes with different waterbody types (open waterbody, YC; semi-enclosed waterbody, WB; and enclosed waterbody, YYP). High-throughput sequencing results showed that MTB affiliated to Alphaproteobacteria, Betaproteobacteria and Nitrospira distributed widely in these lakes. The genera of Magnetococcus (98.10%) and Candidatus Magnetoovum (1.47%) were endemic to YC and WB, respectively. The changes in frequency-dependent susceptibility (χfd) values before and after magnetic collection in YC, WB and YYP samples were − 0.28%, 0.05% and − 0.22%, respectively. The magnetic susceptibility was significantly associated with Chao1 (R2 = 0.637 to 0.763, p < .01) and Shannon index (R2 = 0.803 to 0.998, p < .01). The room- and low-temperature magnetic characteristics of sediment samples were analyzed by vibrating sample magnetometer (VSM) and radio-frequency superconducting quantum interference device (SQUID). Results indicated that the presence or absence of MTB could lead to the changes in the room- and low-temperature magnetism of volcanic lake sediments, which would extend our knowledge of MTB magnetism contribution to volcanic ecosystems.

Intensive use of Lagrangian trajectories to quantify coastal area dispersion

Coastal waters are subject to great environmental and anthropogenic pressures. The diffusion and the transport of these waters are a key element for environmental, ecological and economic management. There are numerous indicators of hydrological characteristics based on theories of transport time scale. However, these indicators strongly depend on the geographical shape of the studied area and tend to give information after long integration time periods, generally on the order of weeks. Here, to qualify a coastal area’s dispersion more precisely, we combined two Lagrangian approaches and estimated a local diffusivity. This paper presents the numerical implementation and the results obtained over a tidally flushed, semi-enclosed water body located at mid-latitude. This new coefficient was estimated using the hydrodynamic model MARS 3D with a barycentric repositioning technique over a tidal period to ensure its reliability. We highlight the existing relationships between local diffusivity and both horizontal and vertical processes. Methodological aspects were analysed based on a reference case (number and distribution of particles, resolution, integration time period). The consistency and sensitivity of the coefficient were studied with different forcing conditions (hydrodynamical and meteorological regimes). In conclusion, our local diffusivity provides a new perspective for understanding the land–sea interface and coastal dispersion and holds potential for future studies of coastal marine ecosystems.

Wind-wave measurements and modelling in the shallow semi-enclosed Palk Bay

Wind-wave characteristics of the Palk Bay, a semi-enclosed water body, are studied by the wave measurements carried out at 2 locations during a one-year period. The analysis of wave data sets shows that wind-sea dominates the Palk Bay during 96% of the time and the contribution of swells are insignificant (<4%). In the Palk Bay, wind speeds are low and act on a limited fetch of only a few kilometers and thus cause waves with small amplitudes, short-wave periods, and short wavelengths. In an annual cycle, significant wave height varied from 0.2 to 1.9 m with an average of 0.6 m. The mean wave periods are mostly concentrated in a narrow range (2–4 s) with a large proportion (~48%) of the waves with a mean wave period less than 3 s. In the southern part of the Palk Bay, northerly waves are more energetic compared to the southerly waves. The wave hindcast data reproduce significant wave height with reasonable accuracy, with a positive bias of 0.08 m, root mean square error of 0.3 m and scatter index of 0.5 when the forcing winds are from Weather Research and Forecast (WRF) numerical model.

Collapse of macrophytic communities in a eutrophicated coastal lagoon.

Collapse of macrophytic communities in a eutrophicated coastal lagoon.

WATER POLLUTION LEVELS IN THE SUWUNG ESTUARY, BALI, BASED ON BIOLOGICAL OXYGEN DEMAND

Biological Oxygen Demand (BOD) is generally used for determining water pollution levels in bodies of water. Estuary is a semi-enclosed body of water that can be polluted via land areas or rivers. This study was conducted to determine the spatial distribution of water pollution levels in the Suwung Estuary in Bali based on BOD5 analyses conducted in January and February 2016. Samples were taken in 20 points (19 points in the Suwung Estuary and 1 outside the Suwung Estuary as control). BOD5 samples were then analysed in the laboratory. Our BOD5 analyses used the amperometric method based on the National Field Manual for the Collection of Data Water-Quality, Chapter A7. BOD5 samples were taken at all tide cycles, during low to high tide and high to low tide. BOD5 values ranged from 0.84 mg/L–9.47 mg/L during lowto high tide and 0.96 mg/L–8.75 mg/L during high to low tide. Results of the BOD5 analyses showed slight contamination in the Suwung Estuary during both tidal conditions. The BOD5 values’ spatial distribution showed higher values around cage aquacultures, rivers, the Suwung Landfill, and around the Benoa Harbour.