Spatio-temporal marine conservation planning to support high-latitude coral range expansion under climate change

Aim: Increasing sea-surface temperatures (SST) have resulted in poleward range expansions of scleractinian corals and declines in their core ranges. These changes may provide management opportunities for the long-term persistence of corals, but spatial prioritization rarely considers and anticipates these changes. We developed a spatio-temporal conservation plan that accommodates future coral range expansions based on projections of future SST. Our spatial planning approach is particularly useful in places with limited information about species distributions. Our aims were to (1) identify areas that consistently remain important for conservation through time and (2) determine the differences between priorities for conservation that account for potential coral range expansions and those that ignore them. Location: Japan. Methods: We developed spatial planning approaches using predicted coral habitat distributions for current conditions, the near future and the distant future. Using the Marxan conservation planning software, we designed conservation plans for scenarios that incorporated different types of spatial and temporal connections. Spatial connections are physical connections between adjacent and nearby areas, whereas temporal connections connect planning areas throughout time. Results: We found that protecting areas important for current and future coral habitat distributions is possible by prioritizing places that are consistently important through time. A spatially and temporally cohesive plan was accomplished with only a 14% increase in the overall reserve system costs, compared with reserve systems ignoring future coral habitat distributions. The attributes of priority areas (e.g. locations, outside boundary length and size) were substantially different when we varied the types of connections. Main conclusions: This study demonstrated that areas with highest conservation priority now will not necessarily be optimal when planning for future change, such as coral range expansions. Furthermore, we showed that incorporating spatio-temporal connections into spatial prioritization achieves objectives of simultaneously conserving corals in the current climate and facilitating their expansions as SST rises

Role of tidal flat in material cycling in the coastal sea

A simple tidal flat model with pelagic and benthic ecosystems was developed in order to analyze the nitrogen cycling in an inter-tidal flat of the Seto Inland Sea, Japan. After the verification of calculation results with the observed results in water quality and benthic biomasses, the role of this tidal flat in nitrogen cycling was evaluated from the viewpoint of water quality purification capability. When there is no suspension feeder in the tidal flat, the water quality purification capability of this tidal flat becomes lower because the outflow of organic nitrogen increases compared to the present case, and the red tides may be generated

Projected coral bleaching in response to future sea surface temperature rises and the uncertainties among climate models

We quantitatively evaluated the effects of rising sea surface temperature (SST) on coral bleaching and the uncertainties resulting from differences in global warming projections. To do so, we used monthly SSTs in the twenty-first century obtained from 23 climate models under the A1B scenario (from the Special Report on Emissions Scenarios) and SST-based indices for coral bleaching. All of the projections indicated that severe bleaching or death of corals will be common and severe in wide areas of the tropical and subtropical oceans by the middle of this century. However, decadal oscillation could modify the exact timing by around +/- 10 years. Such projections are important for conserving marine biodiversity and designing future strategies to avoid tropical and subtropical coral extinction. To obtain more reliable projections and reduce uncertainties, climate models should be improved by using higher spatiotemporal resolutions, and more realistic biological indices should be embedded into existing models

Projection and uncertainty of the poleward range expansion of coral habitats in response to sea surface temperature warming: A multiple climate model study

Using projected monthly mean sea surface tem-perature (SST) in the 21st century obtained by multiple climate models and SST-based indices for the poleward range expansions of three types of coral habitats, we quantitatively evaluated the effects of SST warming on potential northern limit of coral habitats in seas close to Japan and their uncertainty in the global warming pro-jections. The uncertainty in the timing of temperate coral community formation due to global warming was no less than 30 years, with a modulation of ±10 years due to decadal climate variability. Tropical-subtropical and tem-perate coral communities and coral occurrence in seas close to Japan were predicted to shift poleward by a few hundred kilometers by the end of the 21st century. The average estimated speeds of the shifts were 1, 2, and 4 km/year for the tropical-subtropical coral community, temper-ate coral community, and coral occurrence, respectively. The simulated speeds were relatively slower than those previously observed (up to 14 km/year; Yamano et al. 2011), indicating that there are time lags between the new recruitment of coral colonies and the establishment of coral communities. Hence, monitoring of coral dynamics in response to SST warming is required. Collaboration between monitoring and modeling would enhance the reliability of future projections of changes in coral ha-bitats. Such projections are important for conserving marine biodiversity and developing plans for human societies to adapt to global warming

Environmental capacity of oyster culture in the northern part of Hiroshima Bay

The concept of environmental capacity of oyster culture in the northern part of Hiroshima Bay is proposed using a numerical ecosystem model which contains the cultured oyster. The relation between the chlorophyll-a concentration in the upper layer and mortality rate of the cultured oyster was approximated with the TANH function, and the formula about the biochemical process of oyster was built. As the result of numerical ecosystem model calculation, we suggest that the concept of environmental capacity of oyster culture fishery in the northern part of Hiroshima Bay is defined by total phosphorus (TP) load from Ohta River maximizing the standing stock of cultured oyster