Japan's nationwide long‐term monitoring survey of seaweed communities known as the “Monitoring Sites 1000”: Ten‐year overview and future perspectives

Abstract

SUMMARY “Monitoring Sites 1000” – Japan's long‐term monitoring survey was established in 2003, based on the Japanese Government policy for the conservation of biodiversity. Ecological surveys have been conducted on various types of ecosystems at approximately 1000 sites in Japan for 15 years now and are planned to be carried out for 100 years. Since 2008, seaweed communities had been monitored at six sites, featuring the kelp (e.g. Saccharina and Ecklonia; Laminariales) and Sargassum (Fucales) communities in the subarctic and temperate regions of Japan. Annual surveys were carried out during the season when these canopy‐forming seaweeds are most abundant. A non‐destructive quadrat sampling method, with permanent quadrats placed along transects perpendicular to the shoreline, was used to determine species composition, coverage, and vertical distribution of seaweeds at these sites; while destructive sampling was done every 5 years to determine biomass. The occurrence of canopy‐forming species Saccharina japonica (var. japonica) and Ecklonia cava have appeared to be stable at the Muroran (southwestern part of Hokkaido Island) and Shimoda (Pacific coast of middle Honshu Island) sites, respectively; whereas the coverage of Ecklonia radicosa (= Eckloniopsis radicosa) at the Satsuma‐Nagashima site in southern part of Kyushu Island was highly variable until its sudden disappearance from the habitat in 2016. Thalli of E. radicosa lost most of their blades through browsing by herbivorous fish, and thus, this may be one of the causes of the decline. A shift in the community structure related to environmental changes had also been observed at some other sites. Pre‐ and post‐disaster data revealed the impact of the 2011 earthquake and tsunami disasters, including a shift in the vertical distribution of Ecklonia bicyclis (= Eisenia bicyclis) to shallower depths at the Shizugawa site in the Pacific coast of northern Honshu Island, due to seafloor subsidence.

Photosynthetic activity including the thermal‐ and chilling‐light sensitivities of a temperate Japanese brown alga Sargassum macrocarpum

“…Despite the overlapping horizontal distribution of these species in Japan (Yoshida ; Terada et al . , ), their vertical distributions vary, which seems to be structured in response to the vertical attenuation of light. The relatively low compensation ( E c ) and saturation ( E k ) irradiances in the present study revealed the ability of S. macrocarpum to effectively photosynthesize under the low‐irradiance environment at the sublittoral depth.…”

“…Despite the limited distribution in East Asia, this alga is commonly found within temperate regions of Japan, including the coasts of Honshu, Shikoku, and Kyushu islands, which are particularly influenced by the warm Kuroshio and Tsushima currents (Yoshida ; Terada et al . ). This species is rarely found in subarctic Hokkaido Island and in the Pacific coast of northern Honshu Island (Pacific coast of Tohoku region) that is influenced by the cold Oyashio current (Kurile current; Yoshida ).…”

Phosphorus demand and uptake during growth and maturation of the brown alga Sargassum macrocarpum

“…Murase et al 2000aMurase et al , 2000bYatsuya et al 2005), therefore providing important resources to the local fishing industry. Indeed, S. macrocarpum is one of the largest perennial brown seaweeds found throughout the Japan Sea Coast and the Seto Inland Sea of Japan (Yoshida 1983;Murase 2001;Terada et al 2019) and since Sargassacean species can be found in a variety of environments, such as exposed coastlines and quiescent bays, it is likely to exhibit superior tolerance to changes in environmental conditions (e.g. temperature and nutrient concentration).…”

Heat Stress Promotes Nitrogen Accumulation in Meristems via Apical Blade Erosion in a Brown Macroalga With Intercalary Growth

“…The kelp Eisenia bicyclis (Kjellman) Setchell is one of the dominant species on temperate reefs around Japan (Kawai et al, 2020;Terada et al, 2020), and is one of the most phlorotanninrich kelp globally (Ragan and Glombitza, 1986). In the present study, two different experiments were conducted; experiment 1 tested the combined effects of warming, irradiance, and nutrient enrichment on maximum quantum yield of PSII (F v /F m ) to determine the irradiance and nutrient conditions in which warming induces photoinhibition in this kelp species.…”