Coastal Bay Research Articles

Tracks of typhoon movement (left and right sides) control marine dynamics and eco-environment in the coastal bays after typhoons: A case study in Zhanjiang Bay

Coastal oceans are highly responsive to typhoons, making them one of the most affected regions. However, our understanding of the impact of typhoon intensity and movement path on marine dynamic processes and eco-environmental factors remains limited because there are very few on-site investigations, especially continuous field observations in the bay during typhoon events. This study investigated dual water isotopes through a continuous survey (with a 5-day interval) during ten cruises in Zhanjiang Bay, associated with two typhoons of varying intensities and landing tracks (left and right sides). After typhoons, the water mass mixing intensified and lasted for several weeks, depending on the intensity of typhoons. During the typhoon periods, there was a considerable increase in contributions from freshwater to nutrient loads; however, this contribution was higher from the stronger typhoon than the weaker one. The weaker Typhoon Lionrock, which landed on the left side of the bay, enhanced the ocean front due to onshore winds induced by the typhoon, causing intrusion of high-salinity seawater into the bay and retaining pollutants in the bay. However, when stronger Typhoon Chaba landed on the right side, offshore winds induced by counterclockwise wind stress during the typhoon resulted in more seawater flowing toward the lower and outer bay. This prevented the forming of an ocean front and played a dilution role in pollutants through its hydrodynamic process. This was primarily due to the fact that the landing trajectory of typhoons directly influenced the direction of seawater flow in Zhanjiang Bay, while the intensity of typhoons further amplifies these flow patterns. This study suggests that tracks of typhoon movement, rather than their intensity and terrestrial runoff, play a crucial role in governing marine dynamics and nutrient supplies in coastal bays during typhoon events.

Coastal eutrophication driven by long-distance transport of large river nutrient loads, the case of Xiangshan Bay, China

With accelerating anthropogenic activities, the overloading of land-derived nutrients and the resultant eutrophication are threatening coastal aquatic habitats worldwide. In semi-enclosed coastal bays, eutrophication is always considered a local problem that can be mitigated by nutrient reduction at a regional scale. However, as the main nutrient drains major global river discharges can have far-reaching effects over hundreds of kilometers alongshore, which are usually not precisely recognized in local coastal zone management. Here, we first quantified the contributions from both local and remote nutrient sources in Xiangshan Bay (XSB), a eutrophic semi-enclosed bay in China 200 km south of the mouth of the Changjiang River (CJR, the world's third largest river), employing a salinity-based conservative mixing model. We found that the nutrients in Xiangshan Bay were mainly supplied by intruded coastal water fed by CJR discharge, contributing 63 % of dissolved inorganic nitrogen (DIN), 65 % of dissolved silicon (DSi), and 49 % of dissolved inorganic phosphorus (DIP) during the summer of 2017, and 75 % of DIN, 75 % of DSi and 60 % of DIP during the winter of 2019. Additionally, long-term interannual trends in the nutrient concentrations of XSB were generally synchronous with those of the downstream portion of the CJR, indicating that CJR discharge seems to be a strong driver of the eutrophication observed in XSB. In contrast, the impact of local nutrient inputs, such as riverine sewage drainage, aquaculture, biogenic activities, and elemental recycling, was much lower and was regionally limited to the inner bay. Interestingly, the DIP contributions of the local and remote sources were similar, indicating the greater relevance of the internal process. Overall, to mitigate eutrophication in large river-adjacent coastal bays, the inter-regional united practices for nutrient source regulation and ecosystem restoration should be permanently applied along the entire river basin-estuary-coastal continuum.

Evaluation of water pollution in the estuary and adjacent coastal Bay of Bengal using water quality index and its implication to sustainable ecosystem management

Evaluation of water pollution in the estuary and adjacent coastal Bay of Bengal using water quality index and its implication to sustainable ecosystem management

Records of the non-native alga Acanthophoraspicifera (Rhodophyta) and their colonial epibionts in La Paz Bay, Gulf of California.

Acanthophoraspicifera, a red alga considered an alien species, was discovered for the first time on the Pacific coast of Mexico in 2006 from a locality inside La Paz Bay, Gulf of California. Since then, more records have shown its presence, 17 localities having been added up to 2015. A two-year field study (2020-2022) visiting 31 sites along the coast of La Paz Bay, complemented with data from literature and citizen science, resulted in a database of 709 entries that spans the data from 2004 to 2023. These data showed a distribution that goes from Punta Coyote, close to Boca Grande, the northern entrance to the Bay to Playa Tecolote in the south, more than 100 km of coastline, including Espiritu Santo Archipelago, an area considered a natural reserve since 2007. Anthropogenic activity and environmental variables did not present statistical differences that explain A.spicifera spreading. It represents a naturalised alien species without evidence of a negative impact. Still, it soon could acquire the status of invasive species together with its epibionts Bryozoa and Hydrozoa detected in this study.

Initial characterization of mitochondrial DNA control region haplotypes of the Antillean manatee (Trichechus manatus manatus, Sirenia:Trichechidae) in Guatemala

Introduction: Small populations are at risk of losing genetic variability much faster than large populations; this subsequently decreases their ability to adapt when facing environmental changes. A small population of the endangered Antillean manatee (Trichechus manatus manatus) has been identified in Guatemala.
 Objective: This study explored the genetic diversity of the Antillean manatee in Guatemala by analysing mitochondrial DNA control region haplotypes in the two most important habitats for the species, Bahía La Graciosa, a coastal bay and Bocas del Polochic, a coastal wetland, both located in the Izabal State.
 Methods: Genetic samples were collected using non or minimally invasive sampling techniques: scraping of epidermal tissue, collection of floating feces, and collection of tissue from carcasses. DNA extractions, DNA amplification using polymerase chain reaction (PCR), and sequencing of the control D-loop region were used to process and analyse the samples.
 Results: Seven mitochondrial DNA sequences were obtained from 36 samples collected (minimum of four and maximum of seven individuals). Four haplotypes were identified, A01, A03, A04, and J01. No other Central American country has reported this number of haplotypes in a manatee population, and it is the first time that haplotype A01 has been reported for the region. The Guatemalan manatee population comprises at least two genetic lineages, the Florida/Greater Antilles lineage (haplotypes A01, A03, and A04) and the Mesoamerican lineage (J01).
 Conclusion: Further studies, with the use of nuclear markers, are necessary to understand the population dynamics between Bahia La Graciosa and Bocas del Polochic to identify the number of management units present in the country; also, the degree of relatedness with the Belizean population needs to be established to better coordinate conservation efforts.

Review of the Implementation of the Concept of Sustainable Tourism on the Manado Bay

Sustainable development of the Manado Bay travel coast is essential. Tour coast is one of the foundations of sustainable tourism and has significantly aided in development. The standards of environmental sustainability for coastal tourism must be observed if development is to continue holding fast and providing its greatest contribution. must be planned using the accepted standards of sustainable development. Community participation plays a key role in determining if sustainable ecotourism development criteria are met. This study intends to categorise the city of Manado's coastal tourism patterns from a sustainable tourism development perspective. The research location was carried out on the coast of the Manado bay. Descriptive quantitative research is the methodology employed. According to the study's findings, there were various types of coast and beach. Manado Bay has a variety of tour types, including tours of the beach, the underwater world, culinary travel, and tourism trading. A draught application for sustainable tourism was identified and applied to four locations in a sequential manner with the help of the public. The findings of the study demonstrate that the tourist area dive, tour trade, tour beaches, and tour culinary are where the public's opinion of implementation indicators is most concerned. Understand the terms of the proposed tourist sustainability demonstration that is being held along the Manado Bay coast.

Sources and pathways of mercury in soils from Antarctic periglacial areas

The Antarctic plays a critical role in global mercury cycling as both a sink of Hg and, in response to rapid global warming, an emerging source of Hg through its release from thawing permafrost and recessing glaciers. At the present time, Antarctica and surrounding areas have little mercury contamination in comparison to other regions of the world. Understanding the sources and transformations of Hg in the Antarctic will be particularly important in predicting the role of a changing environment in the mercury cycle as emissions and global climate change. Study samples were collected at 12 stations, categorized into three groups based on the human or animal presence and flora. Sampling took place in December 2018 and January 2019, and soil and parent rock samples were collected and analyzed for total mercury concentration and its fractions using atomic absorption spectroscopy. Bedrock samples collected on the coast of Admiralty Bay were found to have low organic matter content, while soil samples from the west shore of the bay had a high variability of organic matter content, ranging from 3 % to 41 %. The concentration of total mercury in bedrock ranged from 2.1 ng/g to 15.0 ng/g, and in soil samples, the total mercury concentration ranged from 4.7 ng/g to 143.1 ng/g. This paper reviews current knowledge of Hg cycling in the Antarctic, including its sources, fate, and effects on the ecosystem. The implications of climate change for Hg cycling in the region are also discussed, highlighting the need for continued research to better understand the potential impacts of Hg contamination in the Antarctic.

Building adaptive capacity to address coastal flooding: The case of a small Texas City

Coastal flooding is a severe and recurring problem, as evidenced by recent disasters that have caused significant damage for coastal communities. A community’s ability to mitigate the effects of coastal flooding depends on the local context and its adaptive capacity. Although past research has highlighted the important role that non-governmental organizations play in building adaptive capacity to support effective adaptation, few studies have focused specifically on rural, community-based nonprofits. To fill this gap, we employ a mixed-methods approach to evaluate the role of the Ingleside on the Bay Coastal Watch Association (IOBCWA), a resident-led, community-based nonprofit, in building adaptive capacity to coastal flooding in the City of Ingleside on the Bay (IOB; pop. 800), located in the Coastal Bend Region of Texas. By applying a grounded theory framework, we show that IOBCWA has improved the adaptive capacity of IOB through five primary activities: engaging in community organizing, boosting advocacy and outreach, implementing evidence-based data collection, building capacity among residents, and developing regional communication networks. Our findings are further examined using the Regional Fingerprint tool (Hirschfeld et al., 2020) to assess progress toward building regional adaptive capacity. We identify a need for more formalized policies, enhanced regional partnerships, and broader inclusion of socially vulnerable groups to address environmental challenges. Overall, this work highlights the important role that small, community-based nonprofits like IOBCWA play in building community adaptive capacity and suggests the need for a more comprehensive regional approach with participation from multiple stakeholders to address challenges related to coastal flooding.

Hydrodynamic response to bathymetric changes in Tampa Bay, Florida

Bathymetric changes within estuarine and coastal waters can alter the hydrodynamic evolution of sea level and currents, which in turn can influence the ecosystem by altering material property distributions. Here we apply the Tampa Bay Coastal Ocean Model (TBCOM), with an unstructured, high-resolution grid to investigate the hydrodynamic response to bathymetric changes at the periphery of the Tampa Bay mouth over a relatively small area when compared to the whole model domain. Two separate numerical experiments are conducted with the same forcing, one using the original bathymetry and the other employing a revised synthetic bathymetry. The simulated sea level, amplitude and phase of the M2 tide, and associated currents are compared for the two experiments. Significant changes in water level (up to+/-10 cm) and current velocities (up to 20 cm/s) are found in the shallow peripheral area with the two different bathymetric data sets. These bathymetric influences are not limited to the locations where the bathymetric changes occur; they also extend to remote areas of the bay. Since Tampa Bay bathymetry varies with storm-induced sediment redistributions and human actives such as shipping channel dredging and beach nourishment, these findings emphasize the need for accurate and updated bathymetry for coastal ocean modeling and applications.

Impact of Coastal Reclamation on Seagrass Habitat in Palu Bay, Central Sulawesi, Indonesia

Coastal development by conducting reclamation for various uses, for example port construction and operations, is a growing threat to coastal ecosystems including seagrass meadows. For several decades, reclamation for coastal development in Palu Bay has included port construction or extension of single-purpose privately owned port facilities as well as public shipping ports. In addition, reclamation was carried out to provide land for the construction of hotels, housing, recreational areas and coastal protection. The majority of private port terminals are owned by mining companies exporting rock and aggregate from around Palu Bay. There are many quarries in the mountains along the western coast of Palu Bay, and alluvial materials around several rivers along the eastern shore are also exploited. The purpose of this study was to analyse the impact of reclamation on seagrass habitat in Palu Bay, especially the private ports, which the dominant reclamation purposes conducted in this area. This study found about 66 ports around Palu Bay, the majority privately owned by mining companies operating in Palu City and Donggala Regency. The effects of reclamation include reduced seagrass habitat and decreased water quality.

Short-term forecast of Karenia brevis trajectory on the West Florida Shelf

Blooms of the toxic dinoflagellate Karenia brevis, also known as harmful algal blooms (HABs) or red tides, occur almost annually on the west coast of Florida, killing fish and other marine life, threatening public health and adversely impacting local economies. Mitigating such effects requires improved red tide forecast capabilities on the West Florida Shelf. A short-term Lagrangian trajectory forecast tool is developed to help federal, state, and local end users monitor and manage red tides on the west coast of Florida. The forecast products are based on the West Florida Coastal Ocean Model (WFCOM) and the Tampa Bay Coastal Ocean Model (TBCOM) nowcast/forecast systems. Observed K. brevis cell count data are uploaded daily into the models to generate 3.5-day forecasts of the bloom trajectories both on the shelf and in the estuaries. The tracking tool displays modeled bloom trajectories at the surface and near-bottom with five categories of cell concentrations (each approximately representing an order of magnitude difference in concentration). More general and user-friendly maps are also produced to provide red tide advisories along the coast, including those integrated with satellite imagery.

Temperature amplification and marine heatwave alteration in shallow coastal bays

Shallow coastal ecosystems are threatened by marine heatwaves, but few long-term records exist to quantify these heatwaves. Here, 40-year records of measured water temperature were constructed for a site in a system of shallow bays with documented heatwave impacts and a nearby ocean site; available gridded sea-surface temperature datasets in the region were also examined. Water temperatures at both sites increased significantly though bay temperatures were consistently 3-4°C hotter in summer and colder in winter and were more variable overall, differences not captured in high-resolution gridded sea-surface temperature datasets. There was considerable overlap in heatwave events at the coastal bay and ocean sites. Annual heatwave exposure was similar and significantly increased at both sites while annual heatwave intensity was significantly higher at the bay site owing to the high variance of the daily temperature anomaly there. Event frequency at both sites increased at a rate of about 1 event/decade. Future simulations indicate all heatwave metrics increase, as do days above 28°C, a heat stress threshold for seagrass. Ocean temperatures on the U.S. mid-Atlantic margin have rarely exceeded this threshold, while summer bay temperatures commonly do, allowing ocean exchange with coastal bays to provide thermal relief to bay ecosystems. This will have changed by 2100, creating a thermal environment that threatens seagrass communities in these systems. Documenting such change requires development of long-term water temperature records in more shallow coastal systems.

Dissolved organic matter cycling revealed from the molecular level in three coastal bays of China

As the widespread distributed and critical zones connecting the land and ocean systems, coastal bays are special units with semi-enclosed landforms to accommodate and process dissolved organic matter (DOM) in the context of increasing anthropogenic effects globally. However, compared to other common systems that have been paid much attention to (e.g., large river estuaries, wetlands), the roles of the coastal bays in coastal carbon cycling are less explored. To fill this knowledge gap, here we combined optical techniques and ultra-high-resolution mass spectrometry to systematically investigate the DOM chemistry of the three typical coastal bays in different nutrient levels, Xiangshan Bay, Jiaozhou Bay, and Sishili Bay, in China. Results show that terrestrial signals and anthropogenic imprints were observed in these three bays to various extents. Besides, Xiangshan Bay with a higher nutrient level had the DOM characterized by lower humification and aromaticity degree than Jiaozhou Bay and Sishili Bay, which not likely mainly resulted from the differences in the primary production or photochemical processing. Further examination reveals that microbial processing likely contributes to the differences in DOM chemistry among the three bays, as indicated by different proportions of potentially transformed nitrogen-containing molecules and relative abundances of the island of stability molecules. Considering the nutrient levels in different bays, we speculate that the lower nutrient concentrations would promote the efficiency of the microbial carbon pump (MCP), which hypothesized that heterotrophic microorganisms might contribute to the formation of marine recalcitrant organic carbon. Additionally, the enrichment of oxygen-rich compounds in the unique carboxyl-rich alicyclic molecule pool of Jiaozhou Bay and Sishili Bay suggests that the efficient MCP might preferentially form them in these two bays. This study emphasizes the importance of coordinating the land and ocean systems and controlling the nutrient discharge to coastal bays, thus, to potentially promote long-term marine carbon sequestration.

Tsunami wave characteristics in Sendai Bay, Japan, following the 2016 Mw 6.9 Fukushima earthquake

On 21 November 2016, a Mw 6.9 intraplate earthquake occurred off the Fukushima coast in Japan, triggering a moderate-size tsunami with amplifications and long oscillations along the Sendai Bay coast. Here, we apply a hybrid approach to hindcast the wave characteristics in the Sendai Bay during the 2016 tsunami event, by analyzing coastal tide records, spectral analyses, and tsunami simulations. Our analysis shows that tsunami wave on tide stations mainly carried wave periods of 3.8–22.5 min, triggered by source periods of 18.5–22.5 min. The long oscillation in Sendai Bay was due to longer period of >28.8 min, affected by the presence of edge waves and oscillation of Sendai Bay. High-energy wave was found to be significant in most oscillation periods inside the Sendai Bay and around the Oshika Peninsula. The spatial distribution of maximum spectral and simulated tsunami amplitudes also reveal that the radiated tsunami energy was entrapped in the nearshore areas, resulting in resonance amplifications in the Sendai Bay.

EXPERIMENTAL STUDY OF LAGRANGIAN MIXING IN WEAKLY DISSIPATIVE TIDAL CHANNELS

Estuaries are extremely dynamic environments, allowing wildlife to grow in a wide variety of ecosystems because of the interaction of masses of water with different characteristics. In particular, coastal bays and estuaries are characterized by flows driven by hydraulic unbalance such as baroclinic pressure gradients, river inflows and wind stresses, and tidal waves. Here, following a reductionist approach, we examine dispersion processes in a physical model of a tidal channel bounded by an inlet mouth, with tides as the dominant forcing. The presence of a tidal inlet can generate macro-vortices that during a tidal cycle may influence the momentum and mass transport on relatively large distances (Awaji et al. (1980), Awaji (1982), Branyon et al. (2022)). Moreover, tides tend to produce non-monotonic particle velocity correlation leading to possible particle looping trajectories that also reflect on a looping character of the Lagrangian integral time scales, differently from the classical statistically steady or homogeneous turbulence (Enrile et al. (2019)). Our goal is to examine the dispersion regimes by means of two-dimensional velocity measurements at the free surface reproduced in a large-scale physical model as a starting point for Lagrangian analysis. We show how the presence of a tidal inlet generates complex flow patterns depending on the character of the forcing tides. Furthermore, the mixed nature of tides may be crucial to dispersion processes, as it enhances the ability of the flow to transport mass in the direction of the main flow.

Relationship fecundity – morphometrics in the green tiger shrimp, Penaeus semisulcatus De Haan, 1844 (Decapoda, Penaeidae), along the Palk Bay, southern Peninsular India

Abstract The green tiger shrimp, Penaeus semisulcatus, is a commercial species supporting important fishery along the Palk Bay coasts. It is a much sought-after seafood commodity influencing the livelihood of the local fishers. This study aims to investigate the fecundity of the species in relation to its morphometry. Fecundity is an index of reproductive capacity used to calculate a stock’s reproductive potential and the egg’s survival. The absolute fecundity of the shrimp ranged from 26 100 to 750 000 ova alive per female, and the mean absolute fecundity from 59 100 to 583 000 ova alive per female. The relationship between fecundity and the morphometric measurements showed a positive exponential correlation. One-way ANOVA indicated a significant difference in the different size classes’ carapace length, total weight, ovary weight, absolute fecundity, stomach weight, and gastrosomatic index. There was no significant difference between the relative fecundity and the gonadosomatic index. This study provides insight into the reproductive potential of P. semisulcatus for efficient management of the resource in Palk Bay, Tamil Nadu, India.

Evaluation of Tsunami Disasters Caused by the 1923 Great Kanto Earthquake

The 1923 Great Kanto Earthquake is one of the earthquakes that have occurred multiple times in the past as part of the Sagami Trough earthquakes. These earthquakes, which occurred at the plate boundary, occurred in 1495 (Meio Earthquake), 1703 (Genroku Earthquake), and again in 1923, causing significant damage to various areas in Kanto, including Tokyo and Yokohama, and it came to be known as the Great Kanto Earthquake. The Sagami Trough earthquakes have consistently brought strong tsunami disasters to various areas in Kanto, extending from the Sagami Bay coast to the Boso Peninsula, and residents along the coast were highly aware of the risk of tsunamis occurring after major earthquakes. Although a tsunami occurred in the Great Kanto Earthquake of 1923, it is believed to have had a wave height approximately half that of the tsunami in the Genroku Earthquake. However, this tsunami destroyed the livelihoods of villages and caused significant damage. In this study, we aim to reexamine historical records related to the tsunami in the Great Kanto Earthquake and objectively evaluate the actual situation of this tsunami disaster.

IMPACT OF INCLUDING OVERTOPPING IN HYDRODYNAMIC MODELLING FOR COASTAL INUNDATION IN PORT PHILLIP BAY

During 2019-2021 CSIRO led the Port Phillip Bay Coastal Hazard Assessment (PPBCHA) project, concerning the bay located in Victoria, Australia. This study looked into the three main hazards of inundation, erosion and groundwater. As part of the inundation hazard component, coastal inundation involving wave setup, seawall overtopping, drainage and urban flooding was considered. Computational modelling was the tool used to study these key elements, necessitating the development of a coupled hydrodynamic and overtopping model. This paper details the assessment of the overall flooding sensitivity to the inclusion of the overtopping modelling, surge (storm tide), rainfall, and drainage.

Comprehensive study of algal blooms variation in Jiaozhou Bay based on google earth engine and deep learning

The Jiaozhou Bay ecosystem, a crucial marine ecosystem in China, has been plagued by frequent harmful algal blooms as due to deteriorating water quality and eutrophication. This study analyzed the temporal and spatial changes of harmful algal blooms in Jiaozhou Bay from 2000 to 2022 using the Floating Algae Index (FAI) calculated from MODIS (2000–2022) and Sentinel-2 (2015–2022) satellite image datasets. The calculation results of the image datasets were compared. The frequency of planktonic algal outbreaks was low and constant until 2017, but has increased annually since then. Algae blooms are most common in the summer and primarily concentrated along the bay’s coast, middle, and mouth, with obvious seasonal and spatial distribution characteristics. Several factors influencing algal outbreaks were identified, including sea surface temperature, wind speed, air pressure, dissolved oxygen, nitrogen and phosphorus ratios, chemical oxygen demand, and petroleum pollutants. Algal bloom outbreaks in Jiaozhou Bay are expected to remain high in 2023. The findings provide crucial information for water quality management and future algal outbreak prediction and prevention in Jiaozhou Bay.

Regulated vs. unregulated rivers: Impacts on CDOM dynamics in the eastern James Bay

The eastern James Bay (EJB) coast harbors numerous rivers, but there is a dearth of knowledge concerning dissolved organic matter (DOM) in the downstream coastal water. Here we report a four-year (2018–2021) and multi-seasons field study on the mixing behavior and characteristics of the chromophoric DOM (CDOM) in the nearshore EJB. Freshwater discharged from the extensively regulated La Grande River (LGR) was constantly depleted in DOM compared with the unregulated rivers (URRs), being on average 3.35 times lower in CDOM absorption coefficient at 440 nm (aCDOM(440)) and 2.50 times lower in dissolved organic carbon (DOC). In contrast, the absorption spectral slope between 275 and 295 nm (S275–295, a proxy of molecular weight) and the specific absorption coefficient at 254 nm (a*CDOM(254), an indicator of aromaticity) of the LGR CDOM were only 10.6% lower and 11.7% higher than those of the URRs CDOM, respectively. Riverine input was found to be the dominant source of CDOM in the study area, with little influence from sea ice formation or melting. CDOM distribution fell into two distinct regimes: the LGR-influenced low-CDOM area in the north and the URRs-influenced high-CDOM area in the south. The two areas showed strong conservative but separate aCDOM(440)–salinity relationships converging at a common marine endmember (salinity ∼25) with little seasonality. The composite data combing both areas and all seasons and years exhibited non-linear relationships between S275–295, a*CDOM(254) and aCDOM(440) and a robust simple linear correlation of DOC to aCDOM(440). This study suggests a strong impact of river regulation on CDOM input into the EJB, reveals low seasonal variability of CDOM mixing dynamics and characteristics, and demonstrates the feasibility of using remote sensing from space for real-time and synoptical assessment of DOM dynamics and the associated biogeochemical cycles in the EJB.