The role of marine plastic debris and microplastics as a carrier of hazardous chemicals in the marine environment is an emerging issue. This study investigated expanded polystyrene (EPS, commonly known as styrofoam) debris, which is a common marine debris item worldwide, and its additive chemical, hexabromocyclododecane (HBCD). To obtain a better understanding of chemical dispersion via EPS pollution in the marine environment, intensive monitoring of HBCD levels in EPS debris and microplastics was conducted in South Korea, where EPS is the predominant marine debris originate mainly from fishing and aquaculture buoys. At the same time, EPS debris were collected from 12 other countries in the Asia-Pacific region, and HBCD concentrations were measured. HBCD was detected extensively in EPS buoy debris and EPS microplastics stranded along the Korean coasts, which might be related to the detection of a quantity of HBCD in non-flame-retardant EPS bead (raw material). The wide detection of the flame retardant in sea-floating buoys, and the recycling of high-HBCD-containing EPS waste inside large buoys highlight the need for proper guidelines for the production and use of EPS raw materials, and the recycling of EPS waste. HBCD was also abundantly detected in EPS debris collected from the Asia-Pacific coastal region, indicating that HBCD contamination via EPS debris is a common environmental issue worldwide. Suspected tsunami debris from Alaskan beaches indicated that EPS debris has the potential for long-range transport in the ocean, accompanying the movement of hazardous chemicals. The results of this study indicate that EPS debris can be a source of HBCD in marine environments and marine food web.

Radiocesium (137Cs) migration from headwater forested areas to downstream rivers has been investigated in many studies since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, which was triggered by a catastrophic earthquake and tsunami on 11 March 2011. The accident resulted in the release of a huge amount of radioactivity and its subsequent deposition in the environment. A large part of the radiocesium released has been shown to remain in the forest. The dissolved 137Cs concentration and its temporal dynamics in river water, stream water, and groundwater have been reported, but reports of dissolved 137Cs concentration in soil water remain sparse.In this study, soil water was sampled, and the dissolved 137Cs concentrations were measured at five locations with different land-use types (mature/young cedar forest, broadleaf forest, meadow land, and pasture land) in Yamakiya District, located 35 km northwest of FDNPP from July 2011 to October 2012. Soil water samples were collected by suction lysimeters installed at three different depths at each site. Dissolved 137Cs concentrations were analyzed using a germanium gamma ray detector. The dissolved 137Cs concentrations in soil water were high, with a maximum value of 2.5 Bq/L in July 2011, and declined to less than 0.32 Bq/L by 2012. The declining trend of dissolved 137Cs concentrations in soil water was fitted to a two-component exponential model. The rate of decline in dissolved 137Cs concentrations in soil water (k1) showed a good correlation with the radiocesium interception potential (RIP) of topsoil (0–5 cm) at the same site. Accounting for the difference of 137Cs deposition density, we found that normalized dissolved 137Cs concentrations of soil water in forest (mature/young cedar forest and broadleaf forest) were higher than those in grassland (meadow land and pasture land).

Persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) were determined in abiotic samples from Concepción Bay in Central Chile. Samples were soxhlet extracted and injected in gas chromatography–mass spectrometry (GCMS). Polybrominated diphenyl ethers (PBDEs) showed the highest levels in air (3–1100 pg m⁻³), in water (2–64 pg L⁻¹), in sediment, and soil (1–78 ng g⁻¹ (dw)). PAHs were also high in the air (1–6 ng m⁻³), in water (1–7 ng L⁻¹), in sediment (90–300 ng g⁻¹ (dw)), and in soil (15–2300 ng g⁻¹ (dw)). The polychlorinated biphenyls (PCBs) and chlorinated pesticides were generally low and did not show clear trends along the water column, with exception of PAHs. New data are presented in this work to assess the health status of a relevant coastal area in central Chile.

In this study, the climate change, tsunami and biodiversity for 336 km coastline endangered at the South China Sea was investigated with the review for the past, current and prediction models for the future. The hydraulic study of the coastal area was conducted using a well-established 2D numerical model suite Delft3D. The study revealed that the generated earthquakes at the convergence zone in the last century are small (Mw7.3), the possibility that a megathrust earthquake event in the SCS basin occurs in the future. The study area comprises a narrow strip of vegetation notably dominated by Casuarina equisetifolia with other coastal plants. Mangrove forests are found along the coastline and estuaries that are overlaid with marine alluvial soils. The current paper is the first comprehensive study of the South China Sea, and the findings increase the awareness among the public to understand the risk associated with environmental pollution.

The abundance and composition of anthropogenic marine debris from 2012 to 2014 was assessed according to three bottom trawl surveys conducted on the upper continental slope between 198 m and 501 m off the Pacific coast of northeastern Japan. The surveys quantitated marine debris as follows: 33.52–164.62 items km⁻² (January to July 2012), 91.68–215.11 items km⁻² (November 2012 to May 2013), and 160.13–178.19 items km⁻² (November 2013 to May 2014). Plastic bags or household materials mainly dominated terrestrial sources of debris. Principal component analysis latitudinally divided the study area according to debris abundance caused by geographical and hydrodynamic features. The long-term effect of tsunami-associated debris on the seafloor environment was recognized, because terrestrial sources such as heavy household materials were most abundant throughout the study period, with the additional accumulation of fishing gear and plastic bags.

With putting a focus on the balance among the nutrient salts such as nitrogen and phosphorus, the Ministry of the Environment (MOE) developed the Action Plan for Healthy Material Circulation in Ocean (just called the Healthy Plan). The plan aims to facilitate the healthy and smooth circulation of the nutrients with an integrated management over land and sea as a package in respective sea areas. The Healthy Plan is now in a pilot phase and is to be implemented for some selected model regions.Meanwhile, devastating tsunamis caused by the Great East Japan Earthquake on March 11th, 2011 severely damaged the natural environments in the affected regions. In the affected bays, seaweed beds and spawning grounds disappeared in a blink. MOE has launched on the recovery activities of Zostera (eelgrass) beds, using the concepts and the methods used in the “Sato-umi Creation” activity which is a purposeful environmental recovery project.

Tetepare Island in the Solomon Islands is the largest uninhabited island in the South Pacific and supports seagrass beds inside fringing reefs along its coastline. We monitored the diversity and abundance of seagrass species on Tetepare and nearby sparsely-populated Rendova Island over a 12 year period, 4 years before and up to 8 years after a major earthquake and tsunami event in January 2010. Both seagrass cover and diversity declined after the tsunami and had not reached pre-Tsunami levels after 8 years. Seagrass cover declined the fastest at sites on Rendova, closest to the epicentre, declining from 50% to <10% cover within 12 months of the earthquake. At sites within the Tetepare MPA, seagrass cover took longer to decline and dropped from an average of 50% to <10% within 2 years and became dominated by Halophila ovalis. Species richness declined from 9 to 4 species with some species such as Syringodium isoetifolium disappearing from monitoring sites. Community-based monitoring was an effective method of documenting long term changes in seagrass cover and long-term monitoring is required to determine if seagrass beds are permanently altered or return to pre-tsunami conditions.

We investigated two sediment cores to understand whether a tsunami in Onagawa Bay, Japan caused environmental changes. The value of δ¹³C ranged from −21.9‰ to −24.3‰ and of δ¹⁵N ranged from 5.1 to 5.9‰. We conclude that the source of the sediment in the present study area was mainly oceanic and not terrestrial. The chlorophyll concentration ranged from 1.8 to 4.0 μg/g ww, and did not vary greatly between surface and bottom layers. We inferred that all layers were deposited after the tsunami. The major phytoplankton taxa in sediments were diatoms from DNA sequencing. The presence of harmful dinoflagellates was minor. The concentrations of several heavy metals decreased slightly after the tsunami. We inferred that heavy metals in sediments were diluted by the tsunami disturbance. The land in Onagawa suffered serious damage, but disturbance of the seabed was much less evident.

This study is the first to systematically quantify, categorize, and map marine macro-debris across the main Hawaiian Islands (MHI), including remote areas (e.g., Niihau, Kahoolawe, and northern Molokai). Aerial surveys were conducted over each island to collect high resolution photos, which were processed into orthorectified imagery and visually analyzed in GIS. The technique provided precise measurements of the quantity, location, type, and size of macro-debris (>0.05m²), identifying 20,658 total debris items. Northeastern (windward) shorelines had the highest density of debris. Plastics, including nets, lines, buoys, floats, and foam, comprised 83% of the total count. In addition, the study located six vessels from the 2011 Tōhoku tsunami. These results created a baseline of the location, distribution, and composition of marine macro-debris across the MHI. Resource managers and communities may target high priority areas, particularly along remote coastlines where macro-debris counts were largely undocumented.

The soundscapes of four bays along the Kona Coast of Hawaii Island were monitored between January 2011 and March 2013. Equivalent, unweighted sound pressure levels within standard 1/3rd-octave bands (dB re: 1μPa) were calculated for each recording. Sound levels increased at night and were lowest during the daytime when spinner dolphins use the bays to rest. A tsunami provided an opportunity to monitor the soundscape with little anthropogenic component. We detected a decrease in sound levels and variability in one of the busiest bays. During the daytime in the 3.15kHz 1/3rd octave band, we detected 92 loud outliers from vessels, aquaculture, and military mid-frequency active sonar. During one military mid-frequency active sonar event sound levels reached 45.8dB above median ambient noise levels. The differences found in the bays illustrate the importance of understanding soundscapes to effectively manage noise pollution in marine ecosystems.