Son of a beach: Coastal development and the loss of natural beaches over time (1919 to 2018) on Okinawa Island, southern Japan.

The coastline of Okinawa Island, Japan, has been affected by human-made alterations for decades, often from land reclamation and coastal defense construction. Here, we use an Imperial Japanese Army map made between 1919 and 1921 to describe the composition of the Okinawan coastline approximately 100 years ago, and by overlapping this old map with a modern-day map of Okinawa (2018), we identified 131 sites where coastlines showed clear human-made alterations. For these sites, we examined what kinds of ecosystems were lost and what has replaced them.

A community and functional comparison of coral and reef fish assemblages between four decades of coastal urbanisation and thermal stress.

Urbanized coral reefs experience anthropogenic disturbances caused by coastal development, pollution, and nutrient runoff, resulting in turbid, marginal conditions in which only certain species can persist. Mortality effects are exacerbated by increasingly regular thermal stress events, leading to shifts towards novel communities dominated by habitat generalists and species with low structural complexity.There is limited data on the turnover processes that occur due to this convergence of anthropogenic stressors, and how novel urban ecosystems are structured both at the community and functional levels.

Coral cover and rubble cryptofauna abundance and diversity at outplanted reefs in Okinawa, Japan.

Global climate change is leading to damage and loss of coral reef ecosystems. On subtropical Okinawa Island in southwestern Japan, the prefectural government is working on coral reef restoration by outplanting coral colonies from family Acroporidae back to reefs after initially farming colonies inside protected nurseries. In order to establish a baseline for future comparisons, in this study we documented the current status of reefs undergoing outplanting at Okinawa Island, and nearby locations where no human manipulation has occurred.

Environmental DNA can act as a biodiversity barometer of anthropogenic pressures in coastal ecosystems.

Loss of biodiversity from lower to upper trophic levels reduces overall productivity and stability of coastal ecosystems in our oceans, but rarely are these changes documented across both time and space. The characterisation of environmental DNA (eDNA) from sediment and seawater using metabarcoding offers a powerful molecular lens to observe marine biota and provides a series of 'snapshots' across a broad spectrum of eukaryotic organisms. Using these next-generation tools and downstream analytical innovations including machine learning sequence assignment algorithms and co-occurrence network analyses, we examined how anthropogenic pressures may have impacted marine biodiversity on subtropical coral reefs in Okinawa, Japan.

Expanding walls and shrinking beaches: loss of natural coastline in Okinawa Island, Japan.

Okinawa is the largest and most populated island of the Ryukyu Archipelago in southern Japan and is renowned for its natural resources and beauty. Similar as to what has been happening in the rest of the country, Okinawa Island has been affected by an increasing amount of development and construction work. The trend has been particularly acute after reversion to Japanese sovereignty in 1972, following 27 years of post-war American administration.

Marine biodiversity research in the Ryukyu Islands, Japan: current status and trends.

Marine biodiversity and derived ecosystem services are critical to the healthy functioning of marine ecosystems, and to human economic and societal well-being. Thus, an understanding of marine biodiversity in different ecosystems is necessary for their conservation and management. Coral reefs in particular are noted for their high levels of biodiversity, and among the world's coral reefs, the subtropical Ryukyu Islands (RYS; also known as the Nansei Islands) in Japan have been shown to harbor very high levels of marine biodiversity.

Digging for DNA at depth: rapid universal metabarcoding surveys (RUMS) as a tool to detect coral reef biodiversity across a depth gradient.

Background: Effective biodiversity monitoring is fundamental in tracking changes in ecosystems as it relates to commercial, recreational, and conservation interests. Current approaches to survey coral reef ecosystems center on the use of indicator species and repeat surveying at specific sites. However, such approaches are often limited by the narrow snapshot of total marine biodiversity that they describe and are thus hindered in their ability to contribute to holistic ecosystem-based monitoring.

Speciation among sympatric lineages in the genus (Cnidaria: Anthozoa: Zoantharia) revealed by morphological comparison, phylogenetic analyses and investigation of spawning period.

Zoantharians are sessile marine invertebrates and colonial organisms possessing sexual and asexual reproductive ability. The zooxanthellate zoantharian genus is widely distributed in coral reef ecosystems. In the Ryukyu Archipelago, Japan, sympatric and are the dominant species of this genus in the intertidal zone.

Three new species and the molecular phylogeny of from the Indo-Pacific Ocean (Anthozoa, Hexacorallia, Zoantharia).

In this study, three new species of macrocnemic zoantharians (Hexacorallia, Zoantharia) are described from localities in the Indo-Pacific Ocean including the Red Sea, the Maldives, Palau, and southern Japan: , , and Although the genus is currently restricted to species living on antipatharians, is not associated with any living substrate and instead is found on coral reef carbonate substrate within narrow caves or cracks. The two new species that have association with antipatharians, and , can be distinguished by their relative coenenchyme development and the antipatharian species that each uses as substrate. Additionally, all new species described in this study have unique nuclear internal transcribed spacer region of ribosomal DNA (ITS-rDNA) sequences.